Opposing Responses of Bird Functional Diversity to Vegetation Structural Diversity in Wet and Dry Forest

PubMed Central

York, Alan; Swan, Matthew; Christie, Fiona; Di Stefano, Julian

2016-01-01

Disturbance regimes are changing worldwide, and the consequences for ecosystem function and resilience are largely unknown. Functional diversity (FD) provides a surrogate measure of ecosystem function by capturing the range, abundance and distribution of trait values in a community. Enhanced understanding of the responses of FD to measures of vegetation structure at landscape scales is needed to guide conservation management. To address this knowledge gap, we used a whole-of-landscape sampling approach to examine relationships between bird FD, vegetation diversity and time since fire. We surveyed birds and measured vegetation at 36 landscape sampling units in dry and wet forest in southeast Australia during 2010 and 2011. Four uncorrelated indices of bird FD (richness, evenness, divergence and dispersion) were derived from six bird traits, and we investigated responses of these indices and species richness to both vertical and horizontal vegetation diversity using linear mixed models. We also considered the extent to which the mean and diversity of time since fire were related to vegetation diversity. Results showed opposing responses of FD to vegetation diversity in dry and wet forest. In dry forest, where fire is frequent, species richness and two FD indices (richness and dispersion) were positively related to vertical vegetation diversity, consistent with theory relating to environmental variation and coexistence. However, in wet forest subject to infrequent fire, the same three response variables were negatively associated with vertical diversity. We suggest that competitive dominance by species results in lower FD as vegetation diversity increases in wet forest. The responses of functional evenness were opposite to those of species richness, functional richness and dispersion in both forest types, highlighting the value of examining multiple FD metrics at management-relevant scales. The mean and diversity of time since fire were uncorrelated with vegetation diversity in wet forest, but positively correlated with vegetation diversity in dry forest. We therefore suggest that protection of older vegetation is important, but controlled application of low-severity fire in dry forest may sustain ecosystem function by enhancing different elements of FD. PMID:27741290

Primary succession on a Hawaiian dryland chronosequence

Treesearch

Kealohanuiopuna M. Kinney; Gregory P. Asner; Susan Cordell; Oliver A. Chadwick; Katherine Heckman; Sara Hotchkiss; Marjeta Jeraj; Ty Kennedy-Bowdoin; David E. Knapp

2015-01-01

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on...

Characterising Vegetation Structural and Functional Differences Across Australian Ecosystems From a Network of Terrestrial Laser Scanning Survey Sites and Airborne and Satellite Image Archives

NASA Astrophysics Data System (ADS)

Phinn, S. R.; Armston, J.; Scarth, P.; Johansen, K.; Schaefer, M.; Suarez, L.; Soto-Berelov, M.; Muir, J.; Woodgate, W.; Jones, S.; Held, A. A.

2015-12-01

Vegetation structural information is critical for environmental monitoring, management and compliance assessment. In this context we refer to vegetation structural properties as vertical, horizontal and volumetric dimensions, including: canopy height; amount and distribution of vegetation by height; foliage projective cover (FPC); leaf area index (LAI); and above ground biomass. Our aim was to determine if there were significant differences between vegetation structural properties across 11 ecosystem types in Australia as measured by terrestrial laser scanner (TLS) structure metrics. The ecosystems sampled included: mesophyll vineforest, wet-dry tropical savannah, mallee woodland, subtropical eucalypt forest, mulga woodland/grassland, wet eucalypt forest, dry eucalypt forest, tall and wet eucalypt forest, and desert grassland/shrublands. Canopy height, plant area-height profiles and LAI were calculated from consistently processed TLS data using Australia's Terrestrial Ecosystem Research Network's (TERN) Supersites by the TERN AusCover remote sensing field teams from 2012-2015. The Supersites were sampled using standardised field protocols within a core set of 1 ha plots as part of a 5 km x 5 km uniform area using a RIEGL-VZ400 waveform recording TLS. Four to seven scans were completed per plot, with one centre point and then at 25 m away from the centre point along transect lines at 0o, 60o and 240o. Individual foliage profiles were sensitive to spatial variation in the distribution of plant materials. Significant differences were visible between each of the vegetation communities assessed when aggregated to plot and ecosystem type scales. Several of the communities exhibited simple profiles with either grass and shrubs (e.g. desert grassland) or grass and trees (e.g. mallee woodland). Others had multiple vegetation forms at different heights, contributing to the profile (e.g. wet eucalypt forest). The TLS data provide significantly more detail about the relative vertical and horizontal distribution of plant materials. TLS data are providing a step change in satellite image based vegetation mapping, and refining our knowledge of vegetation structure and its phenological variability. Open access plot scale TLS measurements are available through the TERN Auscover data portal.

Quantifying forest vertical structure to determine bird habitat quality in the Greenbelt Corridor, Denton, TX

NASA Astrophysics Data System (ADS)

Matsubayashi, Shiho

This study presents the integration of light detection and range (LiDAR) and hyperspectral remote sensing to create a three-dimensional bird habitat map in the Greenbelt Corridor of the Elm Fork of the Trinity River. This map permits to examine the relationship between forest stand structure, landscape heterogeneity, and bird community composition. A biannual bird census was conducted at this site during the breeding seasons of 2009 and 2010. Census data combined with the three-dimensional map suggest that local breeding bird abundance, community structure, and spatial distribution patterns are highly influenced by vertical heterogeneity of vegetation surface. For local breeding birds, vertical heterogeneity of canopy surface within stands, connectivity to adjacent forest patches, largest forest patch index, and habitat (vegetation) types proved to be the most influential factors to determine bird community assemblages. Results also highlight the critical role of secondary forests to increase functional connectivity of forest patches. Overall, three-dimensional habitat descriptions derived from integrated LiDAR and hyperspectral data serve as a powerful bird conservation tool that shows how the distribution of bird species relates to forest composition and structure at various scales.

Simulation of ICESat-2 canopy height retrievals for different ecosystems

NASA Astrophysics Data System (ADS)

Neuenschwander, A. L.

2016-12-01

Slated for launch in late 2017 (or early 2018), the ICESat-2 satellite will provide a global distribution of geodetic measurements from a space-based laser altimeter of both the terrain surface and relative canopy heights which will provide a significant benefit to society through a variety of applications ranging from improved global digital terrain models to producing distribution of above ground vegetation structure. The ATLAS instrument designed for ICESat-2, will utilize a different technology than what is found on most laser mapping systems. The photon counting technology of the ATLAS instrument onboard ICESat-2 will record the arrival time associated with a single photon detection. That detection can occur anywhere within the vertical distribution of the reflected signal, that is, anywhere within the vertical distribution of the canopy. This uncertainty of where the photon will be returned from within the vegetation layer is referred to as the vertical sampling error. Preliminary simulation studies to estimate vertical sampling error have been conducted for several ecosystems including woodland savanna, montane conifers, temperate hardwoods, tropical forest, and boreal forest. The results from these simulations indicate that the canopy heights reported on the ATL08 data product will underestimate the top canopy height in the range of 1 - 4 m. Although simulation results indicate the ICESat-2 will underestimate top canopy height, there is, however, a strong correlation between ICESat-2 heights and relative canopy height metrics (e.g. RH75, RH90). In tropical forest, simulation results indicate the ICESat-2 height correlates strongly with RH90. Similarly, in temperate broadleaf forest, the simulated ICESat-2 heights were also strongly correlated with RH90. In boreal forest, the simulated ICESat-2 heights are strongly correlated with RH75 heights. It is hypothesized that the correlations between simulated ICESat-2 heights and canopy height metrics are a function of both canopy cover and vegetation physiology (e.g. leaf size/shape) which contributes to the horizontal and vertical structure of the vegetation.

Characterization of Canopy Layering in Forested Ecosystems Using Full Waveform Lidar

NASA Technical Reports Server (NTRS)

Whitehurst, Amanda S.; Swatantran, Anu; Blair, J. Bryan; Hofton, Michelle A.; Dubayah, Ralph

2013-01-01

Canopy structure, the vertical distribution of canopy material, is an important element of forest ecosystem dynamics and habitat preference. Although vertical stratification, or "canopy layering," is a basic characterization of canopy structure for research and forest management, it is difficult to quantify at landscape scales. In this paper we describe canopy structure and develop methodologies to map forest vertical stratification in a mixed temperate forest using full-waveform lidar. Two definitions-one categorical and one continuous-are used to map canopy layering over Hubbard Brook Experimental Forest, New Hampshire with lidar data collected in 2009 by NASA's Laser Vegetation Imaging Sensor (LVIS). The two resulting canopy layering datasets describe variation of canopy layering throughout the forest and show that layering varies with terrain elevation and canopy height. This information should provide increased understanding of vertical structure variability and aid habitat characterization and other forest management activities.

Vertical distribution of the soil microbiota along a successional gradient in a glacier forefield.

PubMed

Rime, Thomas; Hartmann, Martin; Brunner, Ivano; Widmer, Franco; Zeyer, Josef; Frey, Beat

2015-03-01

Spatial patterns of microbial communities have been extensively surveyed in well-developed soils, but few studies investigated the vertical distribution of micro-organisms in newly developed soils after glacier retreat. We used 454-pyrosequencing to assess whether bacterial and fungal community structures differed between stages of soil development (SSD) characterized by an increasing vegetation cover from barren (vegetation cover: 0%/age: 10 years), sparsely vegetated (13%/60 years), transient (60%/80 years) to vegetated (95%/110 years) and depths (surface, 5 and 20 cm) along the Damma glacier forefield (Switzerland). The SSD significantly influenced the bacterial and fungal communities. Based on indicator species analyses, metabolically versatile bacteria (e.g. Geobacter) and psychrophilic yeasts (e.g. Mrakia) characterized the barren soils. Vegetated soils with higher C, N and root biomass consisted of bacteria able to degrade complex organic compounds (e.g. Candidatus Solibacter), lignocellulolytic Ascomycota (e.g. Geoglossum) and ectomycorrhizal Basidiomycota (e.g. Laccaria). Soil depth only influenced bacterial and fungal communities in barren and sparsely vegetated soils. These changes were partly due to more silt and higher soil moisture in the surface. In both soil ages, the surface was characterized by OTUs affiliated to Phormidium and Sphingobacteriales. In lower depths, however, bacterial and fungal communities differed between SSD. Lower depths of sparsely vegetated soils consisted of OTUs affiliated to Acidobacteria and Geoglossum, whereas depths of barren soils were characterized by OTUs related to Gemmatimonadetes. Overall, plant establishment drives the soil microbiota along the successional gradient but does not influence the vertical distribution of microbiota in recently deglaciated soils. © 2014 John Wiley & Sons Ltd.

Ecohydrological Responses of Dense Canopies to Environmental Variability Part 1: Interplay Between Vertical Structure and Photosynthetic Pathway

USDA-ARS?s Scientific Manuscript database

Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and eco physiological functioning of leaves and the structural components of the canopy. These responses have the poten...

Experimental study of a vertical jet in a vegetated crossflow.

PubMed

Ben Meftah, Mouldi; De Serio, Francesca; Malcangio, Daniela; Mossa, Michele; Petrillo, Antonio Felice

2015-12-01

Aquatic ecosystems have long been used as receiving environments of wastewater discharges. Effluent discharge in a receiving water body via single jet or multiport diffuser, reflects a number of complex phenomena, affecting the ecosystem services. Discharge systems need to be designed to minimize environmental impacts. Therefore, a good knowledge of the interaction between effluents, discharge systems and receiving environments is required to promote best environmental management practice. This paper reports innovative 3D flow velocity measurements of a jet discharged into an obstructed crossflow, simulating natural vegetated channel flows for which correct environmental management still lacks in literature. In recent years, numerous experimental and numerical studies have been conducted on vegetated channels, on the one hand, and on turbulent jets discharged into unvegetated crossflows, on the other hand. Despite these studies, however, there is a lack of information regarding jets discharged into vegetated crossflow. The present study aims at obtaining a more thorough understanding of the interaction between a turbulent jet and an obstructed crossflow. In order to achieve such an objective, a series of laboratory experiments was carried out in the Department of Civil, Environmental, Building Engineering and Chemistry of the Technical University of Bari - Italy. The physical model consists of a vertical jet discharged into a crossflow, obstructed by an array of vertical, rigid, circular and threaded steel cylinders. Analysis of the measured flow velocities shows that the array of emergent rigid vegetation significantly affects the jet and the ambient flow structures. It reduces the mean channel velocity, allowing the jet to penetrate higher into the crossflow. It significantly increases the transversal flow motion, promoting a major lateral spreading of the jet within the crossflow. Due to the vegetation array effects, the jet undergoes notable variations in its vortical structure. The variation of the flow patterns affects the mixing process and consequently the dilution of pollutants discharged in receiving water bodies. Copyright © 2015 Elsevier Ltd. All rights reserved.

UAV-LiDAR accuracy and comparison to Structure from Motion photogrammetry

NASA Astrophysics Data System (ADS)

Kucharczyk, M.; Hugenholtz, C.; Zou, X.; Nesbit, P. R.; Barchyn, T.

2016-12-01

We compare the spatial accuracy of a UAV-LiDAR system with Structure from Motion (SfM) photogrammetry. UAV-based LiDAR remote sensing potentially offers advantages over SfM photogrammetry in vegetated terrain, particularly with respect to canopy penetration and related measurements of ground surface elevation and vegetation height; however, little quantitative evidence has been presented to date. To address this, we performed a case study at a field site in Alberta, Canada with six different land cover types: short grass, tall grass, short shrubs, tall shrubs, deciduous trees, and coniferous trees. Both UAV datasets were acquired on the same day. The SfM dataset was derived from images acquired by a senseFly eBee fixed-wing UAV equipped with a 16.1 megapixel RGB camera. The UAV-LiDAR system is a proprietary design that consists of a single-rotor helicopter (2-m rotor diameter) equipped with a Riegl VUX-1UAV laser scanner, KVH 1750 inertial measurement unit, and dual NovAtel GNSS receivers. We measured vegetation height from at least 30 samples in each land cover type and acquired check point measurements to determine horizontal and vertical accuracy. Vegetation height was measured manually for grasses and shrubs with a level staff, and with a total station for trees. Coordinates of horizontal and vertical check points were surveyed with real-time kinematic (RTK) GNSS. We followed standard methods for computing horizontal and vertical accuracies based on the 2015 guidelines from the American Society of Photogrammetry and Remote Sensing. Results will be presented at the AGU Fall Meeting.

Rapid Characterisation of Vegetation Structure to Predict Refugia and Climate Change Impacts across a Global Biodiversity Hotspot

PubMed Central

Schut, Antonius G. T.; Wardell-Johnson, Grant W.; Yates, Colin J.; Keppel, Gunnar; Baran, Ireneusz; Franklin, Steven E.; Hopper, Stephen D.; Van Niel, Kimberley P.; Mucina, Ladislav; Byrne, Margaret

2014-01-01

Identification of refugia is an increasingly important adaptation strategy in conservation planning under rapid anthropogenic climate change. Granite outcrops (GOs) provide extraordinary diversity, including a wide range of taxa, vegetation types and habitats in the Southwest Australian Floristic Region (SWAFR). However, poor characterization of GOs limits the capacity of conservation planning for refugia under climate change. A novel means for the rapid identification of potential refugia is presented, based on the assessment of local-scale environment and vegetation structure in a wider region. This approach was tested on GOs across the SWAFR. Airborne discrete return Light Detection And Ranging (LiDAR) data and Red Green and Blue (RGB) imagery were acquired. Vertical vegetation profiles were used to derive 54 structural classes. Structural vegetation types were described in three areas for supervised classification of a further 13 GOs across the region. Habitat descriptions based on 494 vegetation plots on and around these GOs were used to quantify relationships between environmental variables, ground cover and canopy height. The vegetation surrounding GOs is strongly related to structural vegetation types (Kappa = 0.8) and to its spatial context. Water gaining sites around GOs are characterized by taller and denser vegetation in all areas. The strong relationship between rainfall, soil-depth, and vegetation structure (R2 of 0.8–0.9) allowed comparisons of vegetation structure between current and future climate. Significant shifts in vegetation structural types were predicted and mapped for future climates. Water gaining areas below granite outcrops were identified as important putative refugia. A reduction in rainfall may be offset by the occurrence of deeper soil elsewhere on the outcrop. However, climate change interactions with fire and water table declines may render our conclusions conservative. The LiDAR-based mapping approach presented enables the integration of site-based biotic assessment with structural vegetation types for the rapid delineation and prioritization of key refugia. PMID:24416149

Rapid characterisation of vegetation structure to predict refugia and climate change impacts across a global biodiversity hotspot.

PubMed

Schut, Antonius G T; Wardell-Johnson, Grant W; Yates, Colin J; Keppel, Gunnar; Baran, Ireneusz; Franklin, Steven E; Hopper, Stephen D; Van Niel, Kimberley P; Mucina, Ladislav; Byrne, Margaret

2014-01-01

Identification of refugia is an increasingly important adaptation strategy in conservation planning under rapid anthropogenic climate change. Granite outcrops (GOs) provide extraordinary diversity, including a wide range of taxa, vegetation types and habitats in the Southwest Australian Floristic Region (SWAFR). However, poor characterization of GOs limits the capacity of conservation planning for refugia under climate change. A novel means for the rapid identification of potential refugia is presented, based on the assessment of local-scale environment and vegetation structure in a wider region. This approach was tested on GOs across the SWAFR. Airborne discrete return Light Detection And Ranging (LiDAR) data and Red Green and Blue (RGB) imagery were acquired. Vertical vegetation profiles were used to derive 54 structural classes. Structural vegetation types were described in three areas for supervised classification of a further 13 GOs across the region. Habitat descriptions based on 494 vegetation plots on and around these GOs were used to quantify relationships between environmental variables, ground cover and canopy height. The vegetation surrounding GOs is strongly related to structural vegetation types (Kappa = 0.8) and to its spatial context. Water gaining sites around GOs are characterized by taller and denser vegetation in all areas. The strong relationship between rainfall, soil-depth, and vegetation structure (R(2) of 0.8-0.9) allowed comparisons of vegetation structure between current and future climate. Significant shifts in vegetation structural types were predicted and mapped for future climates. Water gaining areas below granite outcrops were identified as important putative refugia. A reduction in rainfall may be offset by the occurrence of deeper soil elsewhere on the outcrop. However, climate change interactions with fire and water table declines may render our conclusions conservative. The LiDAR-based mapping approach presented enables the integration of site-based biotic assessment with structural vegetation types for the rapid delineation and prioritization of key refugia.

Habitat diversity in uneven-aged northern hardwood stands: a case study

Treesearch

Laura S. Kenefic; Ralph D. Nyland

2000-01-01

Habitat characteristics were quantified in an empirically balanced uneven-aged northern hardwood stand in central New York. Canopy structure, wildlife trees, downed woody material, low cover, and richness and abundance of understory vegetation were assessed. High vertical structural diversity and low horizontal patchiness were associated with the single-tree selection...

Biomass Increases Go under Cover: Woody Vegetation Dynamics in South African Rangelands

PubMed Central

Mograbi, Penelope J.; Knapp, David E.; Martin, Roberta E.; Main, Russell

2015-01-01

Woody biomass dynamics are an expression of ecosystem function, yet biomass estimates do not provide information on the spatial distribution of woody vegetation within the vertical vegetation subcanopy. We demonstrate the ability of airborne light detection and ranging (LiDAR) to measure aboveground biomass and subcanopy structure, as an explanatory tool to unravel vegetation dynamics in structurally heterogeneous landscapes. We sampled three communal rangelands in Bushbuckridge, South Africa, utilised by rural communities for fuelwood harvesting. Woody biomass estimates ranged between 9 Mg ha-1 on gabbro geology sites to 27 Mg ha-1 on granitic geology sites. Despite predictions of woodland depletion due to unsustainable fuelwood extraction in previous studies, biomass in all the communal rangelands increased between 2008 and 2012. Annual biomass productivity estimates (10–14% p.a.) were higher than previous estimates of 4% and likely a significant contributor to the previous underestimations of modelled biomass supply. We show that biomass increases are attributable to growth of vegetation <5 m in height, and that, in the high wood extraction rangeland, 79% of the changes in the vertical vegetation subcanopy are gains in the 1-3m height class. The higher the wood extraction pressure on the rangelands, the greater the biomass increases in the low height classes within the subcanopy, likely a strong resprouting response to intensive harvesting. Yet, fuelwood shortages are still occurring, as evidenced by the losses in the tall tree height class in the high extraction rangeland. Loss of large trees and gain in subcanopy shrubs could result in a structurally simple landscape with reduced functional capacity. This research demonstrates that intensive harvesting can, paradoxically, increase biomass and this has implications for the sustainability of ecosystem service provision. The structural implications of biomass increases in communal rangelands could be misinterpreted as woodland recovery in the absence of three-dimensional, subcanopy information. PMID:25969985

Vertical zonation of soil fungal community structure in a Korean pine forest on Changbai Mountain, China.

PubMed

Ping, Yuan; Han, Dongxue; Wang, Ning; Hu, Yanbo; Mu, Liqiang; Feng, Fujuan

2017-01-01

Changbai Mountain, with intact montane vertical vegetation belts, is located at a sensitive area of global climate change and a central distribution area of Korean pine forest. Broad-leaved Korean pine mixed forest (Pinus koraiensis as an edificator) is the most representative zonal climax vegetation in the humid region of northeastern China; their vertical zonation is the most intact and representative on Changbai Mountain. In this study, we analyzed the composition and diversity of soil fungal communities in the Korean pine forest on Changbai Mountain at elevations ranging from 699 to 1177 m using Illumina High-throughput sequencing. We obtained a total 186,663 optimized sequences, with an average length of 268.81 bp. We found soil fungal diversity index was decreased with increasing elevation from 699 to 937 m and began to rise after reaching 1044 m; the richness and evenness indices were decreased with an increase in elevation. Soil fungal compositions at the phylum, class and genus levels varied significantly at different elevations, but with the same dominant fungi. Beta-diversity analysis indicated that the similarity of fungal communities decreased with an increased vertical distance between the sample plots, showing a distance-decay relationship. Variation partition analysis showed that geographic distance (mainly elevation gradient) only explained 20.53 % of the total variation of fungal community structure, while soil physicochemical factors explained 69.78 %.

A mathematical characterization of vegetation effect on microwave remote sensing from the Earth

NASA Technical Reports Server (NTRS)

Choe, Y.; Tsang, L.

1983-01-01

In passive microwave remote sensing of the earth, a theoretical model that utilizes the radiative transfer equations was developed to account for the volume scattering effects of the vegetation canopy. Vegetation canopies such as alfalfa, sorghum, and corn are simulated by a layer of ellipsoidal scatterers and cylindrical structures. The ellipsoidal scatterers represent the leaves of vegetation and are randomly positioned and oriented. The orientation of ellipsoids is characterized by a probability density function of Eulerian angles of rotation. The cylindrical structures represent the stalks of vegetation and their radii are assumed to be much smaller than their lengths. The underlying soil is represented by a half-space medium with a homogeneous permittivity and uniform temperature profile. The radiative transfer quations are solved by a numerical method using a Gaussian quadrature formula to compute both the vertical and horizontal polarized brightness temperature as a function of observation angle. The theory was applied to the interpretation of experimental data obtained from sorghum covered fields near College Station, Texas.

Effects of corn stalk orientation and water content on passive microwave sensing of soil moisture

NASA Technical Reports Server (NTRS)

Oneill, P. E.; Blanchard, B. J.; Wang, J. R.; Gould, W. I.; Jackson, T. J.

1984-01-01

A field experiment was conducted utilizing artificial arrangements of plant components during the summer of 1982 to examine the effects of corn canopy structure and plant water content on microwave emission. Truck-mounted microwave radiometers at C (5 GHz) and L (1.4 GHz) band sensed vertically and horizontally polarized radiation concurrent with ground observations of soil moisture and vegetation parameters. Results indicate that the orientation of cut stalks and the distribution of their dielectric properties through the canopy layer can influence the microwave emission measured from a vegetation/soil scene. The magnitude of this effect varies with polarization and frequency and with the amount of water in the plant, disappearing at low levels of vegetation water content. Although many of the canopy structures and orientations studied in this experiment are somewhat artificial, they serve to improve understanding of microwave energy interactions within a vegetation canopy and to aid in the development of appropriate physically based vegetation models.

Characterizing Exterior and Interior Tropical Forest Structure Variability with Full-Waveform Airborne LIDAR Data in Lopé, Gabon

NASA Astrophysics Data System (ADS)

Marselis, S.; Tang, H.; Blair, J. B.; Hofton, M. A.; Armston, J.; Dubayah, R.

2017-12-01

Terrestrial ecotones, transition zones between ecological systems, have been identified as important regions to monitor the effects of environmental and human pressures on ecosystems. To observe such changes, the variability in vegetation horizontal and vertical structure must be characterized. The objective of this study is to quantify changes in vegetation structure in a tropical forest-savanna mosaic using airborne waveform lidar data. The study area is located in the northern part of the Lopé National Park in Gabon and is comprised of the vegetation types: savanna, colonizing forest, monodominant Okoumé forest, young Marantaceae forest and mixed Marantaceae forest. The lidar data were collected by the Land Vegetation and Ice Sensor (LVIS) in early March 2016, during the AfriSAR campaign. Metrics derived from the LVIS waveforms were then used to classify the five main vegetation types and characterize observed structural variability within types and across ecotones. Several supervised and unsupervised classification alogrithms, in combination with statistical analysis, were applied. The investigated methods are promising in their use to directly describe the structural variability within and between different vegetation types, map these vegetation types and the extent and location of their transition zones, and to characterize, among other attributes, the sharpness and width of such ecotones. These results provide important information in ecosystem studies as these methods can be used to study changes in vegetation structure, species-specific habitat, or the effects of deforestation and other human and natural pressures on the exterior and interior forest structure. These methods thus provide ample opportunity to assess the vegetation structure in degraded and second growth tropical forests to explore effects of e.g. grazing, logging or fragmentation. From this study we can conclude that lidar waveform remote sensing is highly useful in distinguishing vegetation types and their transition zones which will be increasingly important when assessing the impact of natural and human pressures on the world's tropical forests.

Vegetation change detection and quantification: linking Landsat imagery and LIDAR data

USGS Publications Warehouse

Peterson, Birgit E.; Nelson, Kurtis J.

2009-01-01

Measurements of the horizontal and vertical structure of vegetation are helpful for detecting and monitoring change or disturbance on the landscape. Lidar has a unique ability to capture the three-dimensional structure of vegetation canopies. In this preliminary study, we present the results of a series of exploratory data analyses that tested our assumptions about the links between the structural data obtainable from lidar and the change detection products derived from Landsat imagery. Our study area is located in the Sierra National Forest in the Sierra Nevada Mountains of California and covers a wide range of vegetation types. The lidar data used in this study were collected by the Laser Vegetation Imaging System (LVIS) (Blair et al., 1999). LVIS is a largefootprint lidar system optimized to measure canopy structure characteristics. A series of Landsat scenes from 1984 through 2008 was collected for the study area (Path 42, Row 34) and processed to generate maps of disturbance. The preliminary results described here indicate that even simple metrics of height can be useful in assessing changes in structure brought about by disturbance in forest canopies. For example, canopy height values for 2008 were higher on average than those measured for 1999 in undisturbed forest, whereas this trend is not clearly observable for the disturbed forest patches.

A sampling device for counting insect egg clusters and measuring vertical distribution of vegetation

Treesearch

Robert L. Talerico; Robert W., Jr. Wilson

1978-01-01

The use of a vertical sampling pole that delineates known volumes and position is illustrated and demonstrated for counting egg clusters of N. sertifer. The pole can also be used to estimate vertical and horizontal coverage, distribution or damage of vegetation or foliage.

Using satellite and airborne LiDAR to model woodpecker habitat occupancy at the landscape scale

Treesearch

Lee A. Vierling; Kerri T. Vierling; Patrick Adam; Andrew T. Hudak

2013-01-01

Incorporating vertical vegetation structure into models of animal distributions can improve understanding of the patterns and processes governing habitat selection. LiDAR can provide such structural information, but these data are typically collected via aircraft and thus are limited in spatial extent. Our objective was to explore the utility of satellite-based LiDAR...

A meta-analysis of lesser prairie-chicken nesting and brood-rearing habitats: implications for habitat management

USGS Publications Warehouse

Hagen, Christian A.; Grisham, Blake A.; Boal, Clint W.; Haukos, David A.

2013-01-01

The distribution and range of lesser prairie-chicken (Tympanuchus pallidicinctus) has been reduced by >90% since European settlement of the Great Plains of North America. Currently, lesser prairie-chickens occupy 3 general vegetation communities: sand sagebrush (Artemisia filifolia), sand shinnery oak (Quercus havardii), and mixed-grass prairies juxtaposed with Conservation Reserve Program grasslands. As a candidate for protection under the Endangered Species Act, there is a need for a synthesis that characterizes habitat structure rangewide. Thus, we conducted a meta-analysis of vegetation characteristics at nest sites and brood habitats to determine whether there was an overall effect (Hedges' d) of habitat selection and to estimate average (95% CI) habitat characteristics at use sites. We estimated effect sizes (di) from the difference between use (nests and brood sites) and random sampling sites for each study (n = 14), and derived an overall effect size (d++). There was a general effect for habitat selection as evidenced by low levels of variation in effect sizes across studies and regions. There was a small to medium effect (d++) = 0.20-0.82) of selection for greater vertical structure (visual obstruction) by nesting females in both vegetation communities, and selection against bare ground (d++ = 0.20-0.58). Females with broods exhibited less selectivity for habitat components except for vertical structure. The variation of d++ was greater during nesting than brooding periods, signifying a seasonal shift in habitat use, and perhaps a greater range of tolerance for brood-rearing habitat. The overall estimates of vegetation cover were consistent with those provided in management guidelines for the species.

China’s new-age small farms and their vertical integration: agribusiness or co-ops?

PubMed

Huang, Philip C C

2011-01-01

The future of Chinese agriculture lies not with large mechanized farms but with small capital-labor dual intensifying family farms for livestock-poultry-fish raising and vegetable-fruit cultivation. Chinese food consumption patterns have been changing from the old 8:1:1 pattern of 8 parts grain, 1 part meat, and 1 part vegetables to a 4:3:3 pattern, with a corresponding transformation in agricultural structure. Small family-farming is better suited for the new-age agriculture, including organic farming, than large-scale mechanized farming, because of the intensive, incremental, and variegated hand labor involved, not readily open to economies of scale, though compatible with economies of scope. It is also better suited to the realities of severe population pressure on land. But it requires vertical integration from cultivation to processing to marketing, albeit without horizontal integration for farming. It is against such a background that co-ops have arisen spontaneously for integrating small farms with processing and marketing. The Chinese government, however, has been supporting aggressively capitalistic agribusinesses as the preferred mode of vertical integration. At present, Chinese agriculture is poised at a crossroads, with the future organizational mode for vertical integration as yet uncertain.

Evaluating a small footprint, waveform-resolving lidar over coastal vegetation communities

USGS Publications Warehouse

Nayegandhl, A.; Brock, J.C.; Wright, C.W.; O'Connell, M. J.

2006-01-01

NASA's Experimental Advanced Airborne Research Lidar (EAARL) is a raster-scanning, waveform-resolving, green-wavelength (532 nm) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor records the time history of the return waveform within a small footprint (20 cm diameter) for each laser pulse, enabling characterization of vegetation canopy structure and "bare earth" topography under a variety of vegetation types. A collection of individual waveforms combined within a synthesized large footprint was used to define three metrics: canopy height (CH), canopy reflection ratio (CRR), and height of median energy (HOME). Bare Earth Elevation (BEE) metric was derived using the individual small-footprint waveforms. All four metrics were tested for reproducibility, which resulted in an average of 95 percent correspondence within two standard deviations of the mean. CH and BEE values were also tested for accuracy using ground-truth data. The results presented in this paper show that combining several individual small-footprint laser pulses to define a composite "large-footprint" waveform is a possible method to depict the vertical structure of a vegetation canopy. ?? 2006 American Society for Photogrammetry and Remote Sensing.

Detecting Below-Ground Processes, Diversity, and Ecosystem Function in a Savanna Ecosystem Using Spectroscopy Across Different Vegetation Layers

NASA Astrophysics Data System (ADS)

Cavender-Bares, J.; Schweiger, A. K.; Madritch, M. D.; Gamon, J. A.; Hobbie, S. E.; Montgomery, R.; Townsend, P. A.

2017-12-01

Above-and below-ground plant traits are important for substrate input to the rhizosphere. The substrate composition of the rhizosphere, in turn, affects the diversity of soil organisms, influences soil biochemistry, and water content, and resource availability for plant growth. This has substantial consequences for ecosystem functions, such as above-ground productivity and stability. Above-ground plant chemical and structural traits can be linked to the characteristics of other plant organs, including roots. Airborne imaging spectroscopy has been successfully used to model and predict chemical and structural traits of the above-ground vegetation. However, remotely sensed images capture, almost exclusively, signals from the top of the canopy, providing limited direct information about understory vegetation. Here, we use a data set collected in a savanna ecosystem consisting of spectral measurements gathered at the leaf, the whole plant, and vegetation canopy level to test for hypothesized linkages between above- and below-ground processes that influence root biomass, soil biochemistry, and the diversity of the soil community. In this environment, consisting of herbaceous vegetation intermixed with shrubs and trees growing at variable densities, we investigate the contribution of different vegetation strata to soil characteristics and test the ability of imaging spectroscopy to detect these in plant communities with contrasting vertical structure.

Revealing livestock effects on bunchgrass vegetation with Landsat ETM+ data across a grazing season

NASA Astrophysics Data System (ADS)

Jansen, Vincent S.

Remote sensing provides monitoring solutions for more informed grazing management. To investigate the ability to detect the effects of cattle grazing on bunchgrass vegetation with Landsat Enhanced Thematic Mapper Plus (ETM+) data, we conducted a study on the Zumwalt Prairie in northeastern Oregon across a gradient of grazing intensities. Biophysical vegetation data was collected on vertical structure, biomass, and cover at three different time periods during the grazing season: June, August, and October 2012. To relate these measures to the remotely sensed Landsat ETM+ data, Pearson's correlations and multiple regression models were computed. Using the best models, predicted vegetation metrics were then mapped across the study area. Results indicated that models using common vegetation indices had the ability to discern different levels of grazing across the study area. Results can be distributed to land managers to help guide grassland conservation by improving monitoring of bunchgrass vegetation for sustainable livestock management.

Estimating Forest Vertical Structure from Multialtitude, Fixed-Baseline Radar Interferometric and Polarimetric Data

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.; Law, Beverly E.; Siqueira, Paul R.

2000-01-01

Parameters describing the vertical structure of forests, for example tree height, height-to-base-of-live-crown, underlying topography, and leaf area density, bear on land-surface, biogeochemical, and climate modeling efforts. Single, fixed-baseline interferometric synthetic aperture radar (INSAR) normalized cross-correlations constitute two observations from which to estimate forest vertical structure parameters: Cross-correlation amplitude and phase. Multialtitude INSAR observations increase the effective number of baselines potentially enabling the estimation of a larger set of vertical-structure parameters. Polarimetry and polarimetric interferometry can further extend the observation set. This paper describes the first acquisition of multialtitude INSAR for the purpose of estimating the parameters describing a vegetated land surface. These data were collected over ponderosa pine in central Oregon near longitude and latitude -121 37 25 and 44 29 56. The JPL interferometric TOPSAR system was flown at the standard 8-km altitude, and also at 4-km and 2-km altitudes, in a race track. A reference line including the above coordinates was maintained at 35 deg for both the north-east heading and the return southwest heading, at all altitudes. In addition to the three altitudes for interferometry, one line was flown with full zero-baseline polarimetry at the 8-km altitude. A preliminary analysis of part of the data collected suggests that they are consistent with one of two physical models describing the vegetation: 1) a single-layer, randomly oriented forest volume with a very strong ground return or 2) a multilayered randomly oriented volume; a homogeneous, single-layer model with no ground return cannot account for the multialtitude correlation amplitudes. Below the inconsistency of the data with a single-layer model is followed by analysis scenarios which include either the ground or a layered structure. The ground returns suggested by this preliminary analysis seem too strong to be plausible, but parameters describing a two-layer compare reasonably well to a field-measured probability distribution of tree heights in the area.

The Laser Vegetation Imaging Sensor: a medium-altitude, digitisation-only, airborne laser altimeter for mapping vegetation and topography

NASA Astrophysics Data System (ADS)

Blair, J. Bryan; Rabine, David L.; Hofton, Michelle A.

The Laser Vegetation Imaging Sensor (LVIS) is an airborne, scanning laser altimeter, designed and developed at NASA's Goddard Space Flight Center (GSFC). LVIS operates at altitudes up to 10 km above ground, and is capable of producing a data swath up to 1000 m wide nominally with 25-m wide footprints. The entire time history of the outgoing and return pulses is digitised, allowing unambiguous determination of range and return pulse structure. Combined with aircraft position and attitude knowledge, this instrument produces topographic maps with dm accuracy and vertical height and structure measurements of vegetation. The laser transmitter is a diode-pumped Nd:YAG oscillator producing 1064 nm, 10 ns, 5 mJ pulses at repetition rates up to 500 Hz. LVIS has recently demonstrated its ability to determine topography (including sub-canopy) and vegetation height and structure on flight missions to various forested regions in the US and Central America. The LVIS system is the airborne simulator for the Vegetation Canopy Lidar (VCL) mission (a NASA Earth remote sensing satellite due for launch in year 2000), providing simulated data sets and a platform for instrument proof-of-concept studies. The topography maps and return waveforms produced by LVIS provide Earth scientists with a unique data set allowing studies of topography, hydrology, and vegetation with unmatched accuracy and coverage.

Estimating the relationship between urban 3D morphology and land surface temperature using airborne LiDAR and Landsat-8 Thermal Infrared Sensor data

NASA Astrophysics Data System (ADS)

Lee, J. H.

2015-12-01

Urban forests are known for mitigating the urban heat island effect and heat-related health issues by reducing air and surface temperature. Beyond the amount of the canopy area, however, little is known what kind of spatial patterns and structures of urban forests best contributes to reducing temperatures and mitigating the urban heat effects. Previous studies attempted to find the relationship between the land surface temperature and various indicators of vegetation abundance using remote sensed data but the majority of those studies relied on two dimensional area based metrics, such as tree canopy cover, impervious surface area, and Normalized Differential Vegetation Index, etc. This study investigates the relationship between the three-dimensional spatial structure of urban forests and urban surface temperature focusing on vertical variance. We use a Landsat-8 Thermal Infrared Sensor image (acquired on July 24, 2014) to estimate the land surface temperature of the City of Sacramento, CA. We extract the height and volume of urban features (both vegetation and non-vegetation) using airborne LiDAR (Light Detection and Ranging) and high spatial resolution aerial imagery. Using regression analysis, we apply empirical approach to find the relationship between the land surface temperature and different sets of variables, which describe spatial patterns and structures of various urban features including trees. Our analysis demonstrates that incorporating vertical variance parameters improve the accuracy of the model. The results of the study suggest urban tree planting is an effective and viable solution to mitigate urban heat by increasing the variance of urban surface as well as evaporative cooling effect.

Developing a global mixed-canopy, height-variable vegetation structure dataset for estimating global vegetation albedo and biomass in the NASA Ent Terrestrial Biosphere Model and GISS GCM

NASA Astrophysics Data System (ADS)

Montes, C.; Kiang, N. Y.; Yang, W.; Ni-Meister, W.; Schaaf, C.; Aleinov, I. D.; Jonas, J.; Zhao, F. A.; Yao, T.; Wang, Z.; Sun, Q.

2015-12-01

Processes determining biosphere-atmosphere coupling are strongly influenced by vegetation structure. Thus, ecosystem carbon sequestration and evapotranspiration affecting global carbon and water balances will depend upon the spatial extent of vegetation, its vertical structure, and its physiological variability. To represent this globally, Dynamic Global Vegetation Models (DGVMs) coupled to General Circulation Models (GCMs) make use of satellite and/or model-based vegetation classifications often composed by homogeneous communities. This work aims at developing a new Global Vegetation Structure Dataset (GVSD) by incorporating varying vegetation heights for mixed plant communities to be used as input to the Ent Terrestrial Biosphere Model (TBM), the DGVM coupled to the NASA Goddard Institute for Space Studies (GISS) GCM. Information sources include the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and plant functional types (PFTs) (Friedl et al., 2010), vegetation height from the Geoscience Laser Altimeter System (GLAS) on board ICESat (Ice, Cloud, and land Elevation Satellite) (Simard et al., 2011; Tang et al., 2014) along with the Global Data Sets of Vegetation Leaf Area Index (LAI)3g (Zhu et al. 2013). Further PFT partitioning is performed according to a climate classification utilizing the Climate Research Unit (CRU) and the NOAA Global Precipitation Climatology Centre (GPCC) data. Final products are a GVSD consisting of mixed plant communities (e.g. mixed forests, savannas, mixed PFTs) following the Ecosystem Demography model (Moorcroft et al., 2001) approach represented by multi-cohort community patches at the sub-grid level of the GCM, which are ensembles of identical individuals whose differences are represented by PFTs, canopy height, density and vegetation structure sensitivity to allometric parameters. To assess the sensitivity of the GISS GCM to vegetation structure, we produce a range of estimates of Ent TBM biomass and plant densities by varying allometric specifications. Ultimately, this GVSD will serve as a template for community data sets, and be used as boundary conditions to the Ent TBM for prediction of canopy albedo in the Analytical Clumped Two-Stream canopy radiative transfer scheme, biomass, primary productivity, respiration, and GISS GCM climate.

Associations of wintering birds with habitat in semidesert and plains grasslands in Arizona

USGS Publications Warehouse

Ruth, Janet M.; Stanley, Thomas R.; Gordon, Caleb E.

2014-01-01

We studied associations with winter habitat for seven species of birds, one species-group (eastern and western meadowlarks combined), and total sparrows at seven sites in the semidesert and plains grasslands of southeastern Arizona from 1999–2001, sampling with mist-nets and survey-transects. We measured structure and composition of vegetation, assessing vegetative differences among sites, and modeled associations between indices of avian abundance and six vegetative variables using generalized linear models. For all vegetative variables, there were significant differences among sites. Numbers of northern harriers (Circus cyaneus) were positively associated with total number of sparrows. Indices of abundance for individual species of birds were statistically correlated with various measures of structure and composition of vegetation. In particular, grasshopper (Ammodramus savannarum) and vesper (Pooecetes gramineus) sparrows were negatively associated with amount of bare ground; horned larks (Eremophila alpestris) were negatively associated with vertical grass density; Baird's sparrows (A. bairdii) were negatively associated with shrub density; meadowlarks (Sturnella magna and S. neglecta combined) were positively associated with native grass. Our results suggest that these species would benefit from management of habitat that affects the vegetative characteristics associated with their abundance.

Fuel loads and fuel type mapping

USGS Publications Warehouse

Chuvieco, Emilio; Riaño, David; Van Wagtendonk, Jan W.; Morsdof, Felix; Chuvieco, Emilio

2003-01-01

Correct description of fuel properties is critical to improve fire danger assessment and fire behaviour modeling, since they guide both fire ignition and fire propagation. This chapter deals with properties of fuel that can be considered static in short periods of time: biomass loads, plant geometry, compactness, etc. Mapping these properties require a detail knowledge of vegetation vertical and horizontal structure. Several systems to classify the great diversity of vegetation characteristics in few fuel types are described, as well as methods for mapping them with special emphasis on those based on remote sensing images.

Wildlife associations in Rocky Mountain juniper in the northern Great Plains, South Dakota

Treesearch

Mark A. Rumble; John E. Gobeille

1995-01-01

Rocky Mountain juniper is an important habitat component in the northern Great Plains. These woodlands provide vertical and horizontal vegetative structure that enhances wildlife use. Ecological approaches to managing habitats require understanding relationships between wildlife species and succession in plant communities. We determined bird, small mammals and large...

Modeling and analysis of the vertical roots distribution in levees - a case study of the third Rhone correction

NASA Astrophysics Data System (ADS)

Gianetta, Ivan; Schwarz, Massimiliano; Glenz, Christian; Lammeranner, Walter

2013-04-01

In recent years the effects of roots on river banks and levees have been the subject of major discussions. The main issue about the presence of woody vegetation on levees is related to the possibility that roots increase internal erosion processes and the superimposed load of large trees compromise the integrity of these structures. However, ecologists and landscape managers argue that eliminating the natural vegetation from the riverbanks also means eliminating biotopes, strengthening anthropisation of the landscape, as well as limiting recreations areas. In the context of the third correction of the Rhone in Switzerland, the discussion on new levee geometries and the implementation of woody vegetation on them, lead to a detailed analysis of this issue for this specific case. The objective of this study was to describe quantitatively the processes and factors that influence the root distribution on levees and test modeling approaches for the simulation of vertical root distribution with laboratory and field data. An extension of an eco-hydrological analytic model that considers climatic and pedological condition for the quantification of vertical root distribution was validated with data provided by the University of Vienna (BOKU) of willows' roots (Salix purpurea) grown under controlled conditions. Furthermore, root distribution data of four transversal sections of a levee near Visp (canton Wallis, Switzerland) was used to validate the model. The positions of the levee's sections were chosen based on the species and dimensions of the woody vegetation. The dominant species present in the sections were birch (Betula pendula) and poplar (Populus nigra). For each section a grid of 50x50 cm was created to count and measure the roots. The results show that vertical distribution of root density under controlled growing conditions has an exponential form, decreasing with increasing soil depth, and can be well described by the eco-hydrological model. Vice versa, field data of vertical roots distribution show a non-exponential function and cannot fully be described by the model. A compacted layer of stones at about 2 m depth is considered as limiting factor for the rooting depth on the analyzed levee. The collected data and the knowledge gained from quantitative analysis represent the starting point for a discussion on new levee geometries and the development of new strategies for the implementation of woody vegetation on levees. A long term monitoring project for the analysis of the effectiveness of new implementation strategies of vegetation on levees, is considered an important prospective for future studies on this topic.

Farming of Vegetables in Space-Limited Environments

NASA Astrophysics Data System (ADS)

He, Jie

2015-10-01

Vegetables that contain most of the essential components of human nutrition are perishable and cannot be stocked. To secure vegetable supply in space limited cities such as Singapore, there are different farming methods to produce vegetables. These include low-cost urban community gardening and innovative rooftop and vertical farms integrated with various technologies such as hydroponics, aquaponics and aeroponics. However, for large-scale vegetable production in space-limited Singapore, we need to develop farming systems that not only increase productivity many-fold per unit of land but also produce all types of vegetable, all year-round for today and the future. This could be resolved through integrated vertical aeroponic farming system. Manipulation of root-zone (RZ) environments such as cooling the RZ, modifying mineral nutrients and introducing elevated RZ CO2 using aeroponics can further boost crop productivity beyond what can be achieved from more efficient use of land area. We could also adopt energy saving light emitting diodes (LEDs) for vertical aeroponic farming system to promote uniform growth and to improve the utilisation of limited space via shortening the growth cycle, thus improving vegetable production in a cost-effective manner.

Coherent structures in wind shear induced wave–turbulence–vegetation interaction in water bodies

DOE PAGES

Banerjee, Tirtha; Vercauteren, Nikki; Muste, Marian; ...

2017-08-26

Flume experiments with particle imaging velocimetry (PIV) were conducted recently to study a complex flow problem where wind shear acts on the surface of a static water body in presence of flexible emergent vegetation and induces a rich dynamics of wave–turbulence–vegetation interaction inside the water body without any gravitational gradient. The experiments were aimed at mimicking realistic vegetated wetlands and the present work is targeted to improve the understanding of the coherent structures associated with this interaction by employing a combination of techniques such as quadrant analysis, proper orthogonal decomposition (POD), Shannon entropy and mutual information content (MIC). The turbulentmore » transfer of momentum is found to be dominated by organized motions such as sweeps and ejections, while the wave component of vertical momentum transport does not show any such preference. Furthermore, by reducing the data using POD we see that wave energy for large flow depths and turbulent energy for all water depths is concentrated among the top few modes, which can allow development of simple reduced order models. Vegetation flexibility is found to induce several roll type structures, however if the vegetation density is increased, drag effects dominate over flexibility and organize the flow. The interaction between waves and turbulence is also found to be highest among flexible sparse vegetation. But, rapidly evolving parts of the flow such as the air–water interface reduces wave–turbulence interaction.« less

Lidar and Hyperspectral Remote Sensing for the Analysis of Coniferous Biomass Stocks and Fluxes

NASA Astrophysics Data System (ADS)

Halligan, K. Q.; Roberts, D. A.

2006-12-01

Airborne lidar and hyperspectral data can improve estimates of aboveground carbon stocks and fluxes through their complimentary responses to vegetation structure and biochemistry. While strong relationships have been demonstrated between lidar-estimated vegetation structural parameters and field data, research is needed to explore the portability of these methods across a range of topographic conditions, disturbance histories, vegetation type and climate. Additionally, research is needed to evaluate contributions of hyperspectral data in refining biomass estimates and determination of fluxes. To address these questions we are a conducting study of lidar and hyperspectral remote sensing data across sites including coniferous forests, broadleaf deciduous forests and a tropical rainforest. Here we focus on a single study site, Yellowstone National Park, where tree heights, stem locations, above ground biomass and basal area were mapped using first-return small-footprint lidar data. A new method using lidar intensity data was developed for separating the terrain and vegetation components in lidar data using a two-scale iterative local minima filter. Resulting Digital Terrain Models (DTM) and Digital Canopy Models (DCM) were then processed to retrieve a diversity of vertical and horizontal structure metrics. Univariate linear models were used to estimate individual tree heights while stepwise linear regression was used to estimate aboveground biomass and basal area. Three small-area field datasets were compared for their utility in model building and validation of vegetation structure parameters. All structural parameters were linearly correlated with lidar-derived metrics, with higher accuracies obtained where field and imagery data were precisely collocated . Initial analysis of hyperspectral data suggests that vegetation health metrics including measures of live and dead vegetation and stress indices may provide good indicators of carbon flux by mapping vegetation vigor or senescence. Additionally, the strength of hyperspectral data for vegetation classification suggests these data have additional utility for modeling carbon flux dynamics by allowing more accurate plant functional type mapping.

Bird Perches Increase Forest Seeds on Puerto Rican Landslides.

Treesearch

Aaron B. Shiels; Lawrence R. Walker

2003-01-01

Landslides result in the loss of vertical vegetative structure, soil nutrients, and the soil seed bank. These losses impede timely recovery of tropical forest communities. In this study we added bird perches to six Puerto Rican landslides with three types of surfaces (bare, climbing fern, grass) in an effort to facilitate inputs of forest seeds through bird dispersal...

[Estimating Winter Wheat Nitrogen Vertical Distribution Based on Bidirectional Canopy Reflected Spectrum].

PubMed

Yang, Shao-yuan; Huang, Wen-jiang; Liang, Dong; Uang, Lin-sheng; Yang, Gui-jun; Zhang, Gui-jan; Cai, Shu-Hong

2015-07-01

The vertical distribution of crop nitrogen is increased with plant height, timely and non-damaging measurement of crop nitrogen vertical distribution is critical for the crop production and quality, improving fertilizer utilization and reducing environmental impact. The objective of this study was to discuss the method of estimating winter wheat nitrogen vertical distribution by exploring bidirectional reflectance distribution function (BRDF) data using partial least square (PLS) algorithm. The canopy reflectance at nadir, +/-50 degrees and +/- 60 degrees; at nadir, +/- 30 degrees and +/- 40 degrees; and at nadir, +/- 20 degrees and +/- 30 degrees were selected to estimate foliage nitrogen density (FND) at upper layer, middle layer and bottom layer, respectively. Three PLS analysis models with FND as the dependent variable and vegetation indices at corresponding angles as the explicative variables were. established. The impact of soil reflectance and the canopy non-photosynthetic materials, was minimized by seven kinds of modifying vegetation indices with the ratio R700/R670. The estimated accuracy is significant raised at upper layer, middle layer and bottom layer in modeling experiment. Independent model verification selected the best three vegetation indices for further research. The research result showed that the modified Green normalized difference vegetation index (GNDVI) shows better performance than other vegetation indices at each layer, which means modified GNDVI could be used in estimating winter wheat nitrogen vertical distribution

The Error Structure of the SMAP Single and Dual Channel Soil Moisture Retrievals

NASA Astrophysics Data System (ADS)

Dong, Jianzhi; Crow, Wade T.; Bindlish, Rajat

2018-01-01

Knowledge of the temporal error structure for remotely sensed surface soil moisture retrievals can improve our ability to exploit them for hydrologic and climate studies. This study employs a triple collocation analysis to investigate both the total variance and temporal autocorrelation of errors in Soil Moisture Active and Passive (SMAP) products generated from two separate soil moisture retrieval algorithms, the vertically polarized brightness temperature-based single-channel algorithm (SCA-V, the current baseline SMAP algorithm) and the dual-channel algorithm (DCA). A key assumption made in SCA-V is that real-time vegetation opacity can be accurately captured using only a climatology for vegetation opacity. Results demonstrate that while SCA-V generally outperforms DCA, SCA-V can produce larger total errors when this assumption is significantly violated by interannual variability in vegetation health and biomass. Furthermore, larger autocorrelated errors in SCA-V retrievals are found in areas with relatively large vegetation opacity deviations from climatological expectations. This implies that a significant portion of the autocorrelated error in SCA-V is attributable to the violation of its vegetation opacity climatology assumption and suggests that utilizing a real (as opposed to climatological) vegetation opacity time series in the SCA-V algorithm would reduce the magnitude of autocorrelated soil moisture retrieval errors.

Modeling vegetation heights from high resolution stereo aerial photography: an application for broad-scale rangeland monitoring.

PubMed

Gillan, Jeffrey K; Karl, Jason W; Duniway, Michael; Elaksher, Ahmed

2014-11-01

Vertical vegetation structure in rangeland ecosystems can be a valuable indicator for assessing rangeland health and monitoring riparian areas, post-fire recovery, available forage for livestock, and wildlife habitat. Federal land management agencies are directed to monitor and manage rangelands at landscapes scales, but traditional field methods for measuring vegetation heights are often too costly and time consuming to apply at these broad scales. Most emerging remote sensing techniques capable of measuring surface and vegetation height (e.g., LiDAR or synthetic aperture radar) are often too expensive, and require specialized sensors. An alternative remote sensing approach that is potentially more practical for managers is to measure vegetation heights from digital stereo aerial photographs. As aerial photography is already commonly used for rangeland monitoring, acquiring it in stereo enables three-dimensional modeling and estimation of vegetation height. The purpose of this study was to test the feasibility and accuracy of estimating shrub heights from high-resolution (HR, 3-cm ground sampling distance) digital stereo-pair aerial images. Overlapping HR imagery was taken in March 2009 near Lake Mead, Nevada and 5-cm resolution digital surface models (DSMs) were created by photogrammetric methods (aerial triangulation, digital image matching) for twenty-six test plots. We compared the heights of individual shrubs and plot averages derived from the DSMs to field measurements. We found strong positive correlations between field and image measurements for several metrics. Individual shrub heights tended to be underestimated in the imagery, however, accuracy was higher for dense, compact shrubs compared with shrubs with thin branches. Plot averages of shrub height from DSMs were also strongly correlated to field measurements but consistently underestimated. Grasses and forbs were generally too small to be detected with the resolution of the DSMs. Estimates of vertical structure will be more accurate in plots having low herbaceous cover and high amounts of dense shrubs. Through the use of statistically derived correction factors or choosing field methods that better correlate with the imagery, vegetation heights from HR DSMs could be a valuable technique for broad-scale rangeland monitoring needs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modeling vegetation heights from high resolution stereo aerial photography: an application for broad-scale rangeland monitoring

USGS Publications Warehouse

Gillan, Jeffrey K.; Karl, Jason W.; Duniway, Michael; Elaksher, Ahmed

2014-01-01

Vertical vegetation structure in rangeland ecosystems can be a valuable indicator for assessing rangeland health and monitoring riparian areas, post-fire recovery, available forage for livestock, and wildlife habitat. Federal land management agencies are directed to monitor and manage rangelands at landscapes scales, but traditional field methods for measuring vegetation heights are often too costly and time consuming to apply at these broad scales. Most emerging remote sensing techniques capable of measuring surface and vegetation height (e.g., LiDAR or synthetic aperture radar) are often too expensive, and require specialized sensors. An alternative remote sensing approach that is potentially more practical for managers is to measure vegetation heights from digital stereo aerial photographs. As aerial photography is already commonly used for rangeland monitoring, acquiring it in stereo enables three-dimensional modeling and estimation of vegetation height. The purpose of this study was to test the feasibility and accuracy of estimating shrub heights from high-resolution (HR, 3-cm ground sampling distance) digital stereo-pair aerial images. Overlapping HR imagery was taken in March 2009 near Lake Mead, Nevada and 5-cm resolution digital surface models (DSMs) were created by photogrammetric methods (aerial triangulation, digital image matching) for twenty-six test plots. We compared the heights of individual shrubs and plot averages derived from the DSMs to field measurements. We found strong positive correlations between field and image measurements for several metrics. Individual shrub heights tended to be underestimated in the imagery, however, accuracy was higher for dense, compact shrubs compared with shrubs with thin branches. Plot averages of shrub height from DSMs were also strongly correlated to field measurements but consistently underestimated. Grasses and forbs were generally too small to be detected with the resolution of the DSMs. Estimates of vertical structure will be more accurate in plots having low herbaceous cover and high amounts of dense shrubs. Through the use of statistically derived correction factors or choosing field methods that better correlate with the imagery, vegetation heights from HR DSMs could be a valuable technique for broad-scale rangeland monitoring needs.

Estimating tropical forest structure using LIDAR AND X-BAND INSAR

NASA Astrophysics Data System (ADS)

Palace, M. W.; Treuhaft, R. N.; Keller, M. M.; Sullivan, F.; Roberto dos Santos, J.; Goncalves, F. G.; Shimbo, J.; Neumann, M.; Madsen, S. N.; Hensley, S.

2013-12-01

Tropical forests are considered the most structurally complex of all forests and are experiencing rapid change due to anthropogenic and climatic factors. The high carbon stocks and fluxes make understanding tropical forests highly important to both regional and global studies involving ecosystems and climate. Large and remote areas in the tropics are prime targets for the use of remotely sensed data. Radar and lidar have previously been used to estimate forest structure, with an emphasis on biomass. These two remote sensing methods have the potential to yield much more information about forest structure, specifically through the use of X-band radar and waveform lidar data. We examined forest structure using both field-based and remotely sensed data in the Tapajos National Forest, Para, Brazil. We measured multiple structural parameters for about 70 plots in the field within a 25 x 15 km area that have TanDEM-X single-pass horizontally and vertically polarized radar interferometric data. High resolution airborne lidar were collected over a 22 sq km portion of the same area, within which 33 plots were co-located. Preliminary analyses suggest that X-band interferometric coherence decreases by about a factor of 2 (from 0.95 to 0.45) with increasing field-measured vertical extent (average heights of 7-25 m) and biomass (10-430 Mg/ha) for a vertical wavelength of 39 m, further suggesting, as has been observed at C-band, that interferometric synthetic aperture radar (InSAR) is substantially more sensitive to forest structure/biomass than SAR. Unlike InSAR coherence versus biomass, SAR power at X-band versus biomass shows no trend. Moreover, airborne lidar coherence at the same vertical wavenumbers as InSAR is also shown to decrease as a function of biomass, as well. Although the lidar coherence decrease is about 15% more than the InSAR, implying that lidar penetrates more than InSAR, these preliminary results suggest that X-band InSAR may be useful for structure and biomass estimation over large spatial scales not attainable with airborne lidar. In this study, we employed a set of less commonly used lidar metrics that we consider analogous to field-based measurements, such as the number of canopy maxima, measures of canopy vegetation distribution diversity and evenness (entropy), and estimates of gap fraction. We incorporated these metrics, as well as lidar coherence metrics pulled from discrete Fourier transforms of pseudowaveforms, and hypothetical stand characteristics of best-fit synthetic vegetation profiles into multiple regression analysis of forest biometric properties. Among simple and complex measures of forest structure, ranging from tree density, diameter at breast height, and various canopy geometry parameters, we found strong relationships with lidar canopy vegetation profile parameters. We suggest that the sole use of lidar height is limited in understanding biomass in a forest with little variation across the landscape and that there are many parameters that may be gleaned by lidar data that inform on forest biometric properties.

Quantifying vegetation distribution and structure using high resolution drone-based structure-from-motion photogrammetry

NASA Astrophysics Data System (ADS)

Zhang, J.; Okin, G.

2017-12-01

Vegetation is one of the most important driving factors of different ecosystem processes in drylands. The structure of vegetation controls the spatial distribution of moisture and heat in the canopy and the surrounding area. Also, the structure of vegetation influences both airflow and boundary layer resistance above the land surface. Multispectral satellite remote sensing has been widely used to monitor vegetation coverage and its change; however, it can only capture 2D images, which do not contain the vertical information of vegetation. In situ observation uses different methods to measure the structure of vegetation, and their results are accurate; however, these methods are laborious and time-consuming, and susceptible to undersampling in spatial heterogeneity. Drylands are sparsely covered by short plants, which allows the drone fly at a relatively low height to obtain ultra-high resolution images. Structure-from-motion (SfM) is a photogrammetric method that was proved to produce 3D model based on 2D images. Drone-based remote sensing can obtain the multiangle images for one object, which can be used to constructed 3D models of vegetation in drylands. Using these images detected by the drone, the orthomosaics and digital surface model (DSM) can be built. In this study, the drone-based remote sensing was conducted in Jornada Basin, New Mexico, in the spring of 2016 and 2017, and three derived vegetation parameters (i.e., canopy size, bare soil gap size, and plant height) were compared with those obtained with field measurement. The correlation coefficient of canopy size, bare soil gap size, and plant height between drone images and field data are 0.91, 0.96, and 0.84, respectively. The two-year averaged root-mean-square error (RMSE) of canopy size, bare soil gap size, and plant height between drone images and field data are 0.61 m, 1.21 m, and 0.25 cm, respectively. The two-year averaged measure error (ME) of canopy size, bare soil gap size, and plant height between drone images and field data are 0.02 m, -0.03, and -0.1 m, respectively. These results indicate a good agreement between drone-based remote sensing and field measurement.

Analysis of vegetation effect on waves using a vertical 2-D RANS model

USDA-ARS?s Scientific Manuscript database

A vertical two-dimensional (2-D) model has been applied in the simulation of wave propagation through vegetated water bodies. The model is based on an existing model SOLA-VOF which solves the Reynolds-Averaged Navier-Stokes (RANS) equations with the finite difference method on a staggered rectangula...

44 CFR 63.17 - Procedures and data requirements for imminent collapse certifications by States.

Code of Federal Regulations, 2014 CFR

2014-10-01

... by the Federal Insurance Administrator may certify that a coastal structure is subject to imminent...: (i) Any evidence of existing damage. The damage can include loss or erosion of soil near or around... vegetation). (B) Beach scarp (erosion line on beach, usually a sharp, nearly vertical drop of 0.5 to 3.0 feet...

44 CFR 63.17 - Procedures and data requirements for imminent collapse certifications by States.

Code of Federal Regulations, 2011 CFR

2011-10-01

... by the Federal Insurance Administrator may certify that a coastal structure is subject to imminent...: (i) Any evidence of existing damage. The damage can include loss or erosion of soil near or around... vegetation). (B) Beach scarp (erosion line on beach, usually a sharp, nearly vertical drop of 0.5 to 3.0 feet...

44 CFR 63.17 - Procedures and data requirements for imminent collapse certifications by States.

Code of Federal Regulations, 2013 CFR

2013-10-01

... by the Federal Insurance Administrator may certify that a coastal structure is subject to imminent...: (i) Any evidence of existing damage. The damage can include loss or erosion of soil near or around... vegetation). (B) Beach scarp (erosion line on beach, usually a sharp, nearly vertical drop of 0.5 to 3.0 feet...

44 CFR 63.17 - Procedures and data requirements for imminent collapse certifications by States.

Code of Federal Regulations, 2012 CFR

2012-10-01

... by the Federal Insurance Administrator may certify that a coastal structure is subject to imminent...: (i) Any evidence of existing damage. The damage can include loss or erosion of soil near or around... vegetation). (B) Beach scarp (erosion line on beach, usually a sharp, nearly vertical drop of 0.5 to 3.0 feet...

The potential of small unmanned aircraft systems and structure-from-motion for topographic surveys: A test of emerging integrated approaches at Cwm Idwal, North Wales

NASA Astrophysics Data System (ADS)

Tonkin, T. N.; Midgley, N. G.; Graham, D. J.; Labadz, J. C.

2014-12-01

Novel topographic survey methods that integrate both structure-from-motion (SfM) photogrammetry and small unmanned aircraft systems (sUAS) are a rapidly evolving investigative technique. Due to the diverse range of survey configurations available and the infancy of these new methods, further research is required. Here, the accuracy, precision and potential applications of this approach are investigated. A total of 543 images of the Cwm Idwal moraine-mound complex were captured from a light (< 5 kg) semi-autonomous multi-rotor unmanned aircraft system using a consumer-grade 18 MP compact digital camera. The images were used to produce a DSM (digital surface model) of the moraines. The DSM is in good agreement with 7761 total station survey points providing a total vertical RMSE value of 0.517 m and vertical RMSE values as low as 0.200 m for less densely vegetated areas of the DSM. High-precision topographic data can be acquired rapidly using this technique with the resulting DSMs and orthorectified aerial imagery at sub-decimetre resolutions. Positional errors on the total station dataset, vegetation and steep terrain are identified as the causes of vertical disagreement. Whilst this aerial survey approach is advocated for use in a range of geomorphological settings, care must be taken to ensure that adequate ground control is applied to give a high degree of accuracy.

Mapping Successional Stages in a Wet Tropical Forest Using Landsat ETM+ and Forest Inventory Data

NASA Technical Reports Server (NTRS)

Goncalves, Fabio G.; Yatskov, Mikhail; dos Santos, Joao Roberto; Treuhaft, Robert N.; Law, Beverly E.

2010-01-01

In this study, we test whether an existing classification technique based on the integration of Landsat ETM+ and forest inventory data enables detailed characterization of successional stages in a wet tropical forest site. The specific objectives were: (1) to map forest age classes across the La Selva Biological Station in Costa Rica; and (2) to quantify uncertainties in the proposed approach in relation to field data and existing vegetation maps. Although significant relationships between vegetation height entropy (a surrogate for forest age) and ETM+ data were detected, the classification scheme tested in this study was not suitable for characterizing spatial variation in age at La Selva, as evidenced by the error matrix and the low Kappa coefficient (12.9%). Factors affecting the performance of the classification at this particular study site include the smooth transition in vegetation structure between intermediate and advanced successional stages, and the low sensitivity of NDVI to variations in vertical structure at high biomass levels.

Integrating shotcrete walls into the natural landscape by application of 'Green Walls'

NASA Astrophysics Data System (ADS)

Medl, Alexandra; Kikuta, Silvia

2017-04-01

Steep slopes resulting from major road infrastructure constructions are increasingly perceived as disagreeable disturbance in the landscape. Thus, a tool to consider landscape aspects and integrate these slopes into the natural environment is required. The challenge is to establish a sustainable vegetation layer despite of adverse circumstances such as inclinations of almost 90⁰, exposed position of slopes near streets and lack of soil and water supply. The objective of this study was to assess the performance of an innovative greening technology for vertical structures (shotcrete wall) in terms of vegetation development on varying plant substrates and geotextiles. The field experiment in Steinach am Brenner, Tyrol, Austria, included testing three plant substrates on basis of nearby rocky excavation material ('Innsbrucker Quarzphyllit', 'Bündnerschiefer' and 'Zentralgneis') combined with compost. Additionally, five geotextiles (geogrid (3x4 mm), geogrid (9x10 mm), coir net, coir mat, geo mat) were applied for evaluation. All test combinations were evaluated regarding vegetation cover and biomass production from 2015 to 2016. Analyses of chemical properties were conducted for all plant substrates. Results showed highest vegetation cover ratio on 'Bündnerschiefer' and 'Innsbrucker Quarzphyllit', which can be explained by the favorable mineral composition (nutrient storage capacity) and chemical properties of compost (lower values of electrical conductivity and C/N ratio). In conclusion, the use of 'Green Walls' filled with 'Bündnerschiefer' or 'Innsbrucker Quarzphyllit' plant substrate in combination with netlike geotextiles proved best, since geo grid and coir net turned out as most successful one year after installation. 'Green Walls' are promising in terms of establishing an optimal vegetation cover on vertical structures and are well suited for integrating shotcrete walls into the landscape. The use of local excavation material for greening purposes can be confirmed, whereby the admixture of high-quality compost is necessary to guarantee satisfying results.

The influence of vegetation height heterogeneity on forest and woodland bird species richness across the United States.

PubMed

Huang, Qiongyu; Swatantran, Anu; Dubayah, Ralph; Goetz, Scott J

2014-01-01

Avian diversity is under increasing pressures. It is thus critical to understand the ecological variables that contribute to large scale spatial distribution of avian species diversity. Traditionally, studies have relied primarily on two-dimensional habitat structure to model broad scale species richness. Vegetation vertical structure is increasingly used at local scales. However, the spatial arrangement of vegetation height has never been taken into consideration. Our goal was to examine the efficacies of three-dimensional forest structure, particularly the spatial heterogeneity of vegetation height in improving avian richness models across forested ecoregions in the U.S. We developed novel habitat metrics to characterize the spatial arrangement of vegetation height using the National Biomass and Carbon Dataset for the year 2000 (NBCD). The height-structured metrics were compared with other habitat metrics for statistical association with richness of three forest breeding bird guilds across Breeding Bird Survey (BBS) routes: a broadly grouped woodland guild, and two forest breeding guilds with preferences for forest edge and for interior forest. Parametric and non-parametric models were built to examine the improvement of predictability. Height-structured metrics had the strongest associations with species richness, yielding improved predictive ability for the woodland guild richness models (r(2) = ∼ 0.53 for the parametric models, 0.63 the non-parametric models) and the forest edge guild models (r(2) = ∼ 0.34 for the parametric models, 0.47 the non-parametric models). All but one of the linear models incorporating height-structured metrics showed significantly higher adjusted-r2 values than their counterparts without additional metrics. The interior forest guild richness showed a consistent low association with height-structured metrics. Our results suggest that height heterogeneity, beyond canopy height alone, supplements habitat characterization and richness models of forest bird species. The metrics and models derived in this study demonstrate practical examples of utilizing three-dimensional vegetation data for improved characterization of spatial patterns in species richness.

The Influence of Vegetation Height Heterogeneity on Forest and Woodland Bird Species Richness across the United States

PubMed Central

Huang, Qiongyu; Swatantran, Anu; Dubayah, Ralph; Goetz, Scott J.

2014-01-01

Avian diversity is under increasing pressures. It is thus critical to understand the ecological variables that contribute to large scale spatial distribution of avian species diversity. Traditionally, studies have relied primarily on two-dimensional habitat structure to model broad scale species richness. Vegetation vertical structure is increasingly used at local scales. However, the spatial arrangement of vegetation height has never been taken into consideration. Our goal was to examine the efficacies of three-dimensional forest structure, particularly the spatial heterogeneity of vegetation height in improving avian richness models across forested ecoregions in the U.S. We developed novel habitat metrics to characterize the spatial arrangement of vegetation height using the National Biomass and Carbon Dataset for the year 2000 (NBCD). The height-structured metrics were compared with other habitat metrics for statistical association with richness of three forest breeding bird guilds across Breeding Bird Survey (BBS) routes: a broadly grouped woodland guild, and two forest breeding guilds with preferences for forest edge and for interior forest. Parametric and non-parametric models were built to examine the improvement of predictability. Height-structured metrics had the strongest associations with species richness, yielding improved predictive ability for the woodland guild richness models (r2 = ∼0.53 for the parametric models, 0.63 the non-parametric models) and the forest edge guild models (r2 = ∼0.34 for the parametric models, 0.47 the non-parametric models). All but one of the linear models incorporating height-structured metrics showed significantly higher adjusted-r2 values than their counterparts without additional metrics. The interior forest guild richness showed a consistent low association with height-structured metrics. Our results suggest that height heterogeneity, beyond canopy height alone, supplements habitat characterization and richness models of forest bird species. The metrics and models derived in this study demonstrate practical examples of utilizing three-dimensional vegetation data for improved characterization of spatial patterns in species richness. PMID:25101782

Waveform LiDAR across forest biomass gradients

NASA Astrophysics Data System (ADS)

Montesano, P. M.; Nelson, R. F.; Dubayah, R.; Sun, G.; Ranson, J.

2011-12-01

Detailed information on the quantity and distribution of aboveground biomass (AGB) is needed to understand how it varies across space and changes over time. Waveform LiDAR data is routinely used to derive the heights of scattering elements in each illuminated footprint, and the vertical structure of vegetation is related to AGB. Changes in LiDAR waveforms across vegetation structure gradients can demonstrate instrument sensitivity to land cover transitions. A close examination of LiDAR waveforms in footprints across a forest gradient can provide new insight into the relationship of vegetation structure and forest AGB. In this study we use field measurements of individual trees within Laser Vegetation Imaging Sensor (LVIS) footprints along transects crossing forest to non-forest gradients to examine changes in LVIS waveform characteristics at sites with low (< 50Mg/ha) AGB. We relate field AGB measurements to original and adjusted LVIS waveforms to detect the forest AGB interval along a forest - non-forest transition in which the LVIS waveform lose the ability to discern differences in AGB. Our results help identify the lower end the forest biomass range that a ~20m footprint waveform LiDAR can detect, which can help infer accumulation of biomass after disturbances and during forest expansion, and which can guide the use of LiDAR within a multi-sensor fusion biomass mapping approach.

Drag coefficients for modeling flow through emergent vegetation in the Florida Everglades

USGS Publications Warehouse

Lee, J.K.; Roig, L.C.; Jenter, H.L.; Visser, H.M.

2004-01-01

Hydraulic data collected in a flume fitted with pans of sawgrass were analyzed to determine the vertically averaged drag coefficient as a function of vegetation characteristics. The drag coefficient is required for modeling flow through emergent vegetation at low Reynolds numbers in the Florida Everglades. Parameters of the vegetation, such as the stem population per unit bed area and the average stem/leaf width, were measured for five fixed vegetation layers. The vertically averaged vegetation parameters for each experiment were then computed by weighted average over the submerged portion of the vegetation. Only laminar flow through emergent vegetation was considered, because this is the dominant flow regime of the inland Everglades. A functional form for the vegetation drag coefficient was determined by linear regression of the logarithmic transforms of measured resistance force and Reynolds number. The coefficients of the drag coefficient function were then determined for the Everglades, using extensive flow and vegetation measurements taken in the field. The Everglades data show that the stem spacing and the Reynolds number are important parameters for the determination of vegetation drag coefficient. ?? 2004 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Tirtha; Vercauteren, Nikki; Muste, Marian

Flume experiments with particle imaging velocimetry (PIV) were conducted recently to study a complex flow problem where wind shear acts on the surface of a static water body in presence of flexible emergent vegetation and induces a rich dynamics of wave–turbulence–vegetation interaction inside the water body without any gravitational gradient. The experiments were aimed at mimicking realistic vegetated wetlands and the present work is targeted to improve the understanding of the coherent structures associated with this interaction by employing a combination of techniques such as quadrant analysis, proper orthogonal decomposition (POD), Shannon entropy and mutual information content (MIC). The turbulentmore » transfer of momentum is found to be dominated by organized motions such as sweeps and ejections, while the wave component of vertical momentum transport does not show any such preference. Furthermore, by reducing the data using POD we see that wave energy for large flow depths and turbulent energy for all water depths is concentrated among the top few modes, which can allow development of simple reduced order models. Vegetation flexibility is found to induce several roll type structures, however if the vegetation density is increased, drag effects dominate over flexibility and organize the flow. The interaction between waves and turbulence is also found to be highest among flexible sparse vegetation. But, rapidly evolving parts of the flow such as the air–water interface reduces wave–turbulence interaction.« less

Comparing helicopter-borne profiling radar with airborne laser scanner data for forest structure estimation.

NASA Astrophysics Data System (ADS)

Piermattei, Livia; Hollaus, Markus; Pfeifer, Norbert; Chen, Yuwei; Karjalainen, Mika; Hakala, Teemu; Hyyppä, Juha; Wagner, Wolfgang

2017-04-01

Forests are complex ecosystems that show substantial variation with respect to climate, management regime, stand history, disturbance, and needs of local communities. The dynamic processes of growth and disturbance are reflected in the structural components of forests that include the canopy vertical structure and geometry (e.g. size, height, and form), tree position and species diversity. Current remote-sensing systems to measure forest structural attributes include passive optical sensors and active sensors. The technological capabilities of active remote sensing like the ability to penetrate the vegetation and provide information about its vertical structure has promoted an extensive use of LiDAR (Light Detection And Ranging) and radar (RAdio Detection And Ranging) system over the last 20 years. LiDAR measurements from aircraft (airborne laser scanning, ALS) currently represents the primary data source for three-dimensional information on forest vertical structure. Contrary, despite the potential of radar remote sensing, their use is not yet established in forest monitoring. In order to better understand the interaction of pulsed radar with the forest canopy, and to increase the feasibility of this system, the Finnish Geospatial Research Institute has developed a helicopter-borne profiling radar system, called TomoRadar. TomoRadar is capable of recording a canopy-penetrating profile of forests. To georeference the radar measurements the system was equipped with a global navigation satellite system and an inertial measurement unit with a centimeter level accuracy of the flight trajectory. The TomoRadar operates at Ku-band, (wave lengths λ 1.5cm) with two separated parabolic antennas providing co- and cross-polarization modes. The purpose of this work is to investigate the capability of the TomoRadar system, for estimating the forest vertical profile, terrain topography and tree height. We analysed 600 m TomoRadar crosspolarized (i.e. horizontal - vertical) profile, acquired in October 2016 over a boreal test site in Evo, Finland. The intensity of the reflected backscatter energy was used to measure the height canopy distribution within an individual footprint. As the intensity of the backscatter energy from the ground is exceeding the intensity from vegetation, the estimation of canopy height and the forest structure were based on i) a threshold between canopy and ground and ii) a peak analysis of the backscattering profile. ALS data collected simultaneously was used to validate the TomoRadar results (i.e. canopy height) and to obtain elevation ground truth. The first results show a high agreement between ALS and TomoRadar derived canopy heights. The derived knowledge about the energy distribution within the canopy height profile leads to an increased understanding of the interactions between the radar signal and the forest canopy and will support optimization of future radar systems with respect to forest structure observation.

Characterization of vertical mixing in oscillatory vegetated flows

NASA Astrophysics Data System (ADS)

Abdolahpour, M.; Ghisalberti, M.; Lavery, P.; McMahon, K.

2016-02-01

Seagrass meadows are primary producers that provide important ecosystem services, such as improved water quality, sediment stabilisation and trapping and recycling of nutrients. Most of these ecological services are strongly influenced by the vertical exchange of water across the canopy-water interface. That is, vertical mixing is the main hydrodynamic process governing the large-scale ecological and environmental impact of seagrass meadows. The majority of studies into mixing in vegetated flows have focused on steady flow environments whereas many coastal canopies are subjected to oscillatory flows driven by surface waves. It is known that the rate of mass transfer will vary greatly between unidirectional and oscillatory flows, necessitating a specific investigation of mixing in oscillatory canopy flows. In this study, we conducted an extensive laboratory investigation to characterise the rate of vertical mixing through a vertical turbulent diffusivity (Dt,z). This has been done through gauging the evolution of vertical profiles of concentration (C) of a dye sheet injected into a wave-canopy flow. Instantaneous measurement of the variance of the vertical concentration distribution ( allowed the estimation of a vertical turbulent diffusivity (). Two types of model canopies, rigid and flexible, with identical heights and frontal areas, were subjected to a wide and realistic range of wave height and period. The results showed two important mechanisms that dominate vertical mixing under different conditions: a shear layer that forms at the top of the canopy and wake turbulence generated by the stems. By allowing a coupled contribution of wake and shear layer mixing, we present a relationship that can be used to predict the rate of vertical mixing in coastal canopies. The results further showed that the rate of vertical mixing within flexible vegetation was always lower than the corresponding rigid canopy, confirming the impact of plant flexibility on canopy-flow interactions.

Treatment and utilization of septic tank effluent using vertical-flow constructed wetlands and vegetable hydroponics.

PubMed

Cui, Li-Hua; Luo, Shi-Ming; Zhu, Xi-Zhen; Liu, Ying-Hu

2003-01-01

Vertical flow constructed wetlands is a typical ecological sanitation system for sewage treatment. The removal rates for COD, BOD5, SS, TN, and TP were 60%, 80%, 74%, 49% and 79%, respectively, when septic tank effluent was treated by vertical flow filter. So the concentration of COD and BOD5 in the treated effluent could meet the quality standard for irrigation water. After that the treated effluent was used for hydroponic cultivation of water spinach and romaine lettuce, the removal efficiencies of the whole system for COD, BOD5, SS, TN and TP were 71.4%, 97.5%, 96.9%, 86.3%, and 87.4%, respectively. And it could meet the integrated wastewater discharge standard for secondary biological treatment plant. It was found that using treated effluent for hydroponic cultivation of vegetables could reduce the nitrate content in vegetables. The removal rates for total bacteria and coliform index by using vertical flow bed system with cinder substrate were 80%-90% and 85%-96%, respectively.

Imaging Laser Altimetry in the Amazon: Mapping Large Areas of Topography, Vegetation Height and Structure, and Biomass

NASA Technical Reports Server (NTRS)

Blair, J. Bryan; Nelson, B.; dosSantos, J.; Valeriano, D.; Houghton, R.; Hofton, M.; Lutchke, S.; Sun, Q.

2002-01-01

A flight mission of NASA GSFC's Laser Vegetation Imaging Sensor (LVIS) is planned for June-August 2003 in the Amazon region of Brazil. The goal of this flight mission is to map the vegetation height and structure and ground topography of a large area of the Amazon. This data will be used to produce maps of true ground topography, vegetation height, and estimated above-ground biomass and for comparison with and potential calibration of Synthetic Aperture Radar (SAR) data. Approximately 15,000 sq. km covering various regions of the Amazon will be mapped. The LVIS sensor has the unique ability to accurately sense the ground topography beneath even the densest of forest canopies. This is achieved by using a high signal-to-noise laser altimeter to detect the very weak reflection from the ground that is available only through small gaps in between leaves and between tree canopies. Often the amount of ground signal is 1% or less of the total returned echo. Once the ground elevation is identified, that is used as the reference surface from which we measure the vertical height and structure of the vegetation. Test data over tropical forests have shown excellent correlation between LVIS measurements and biomass, basal area, stem density, ground topography, and canopy height. Examples of laser altimetry data over forests and the relationships to biophysical parameters will be shown. Also, recent advances in the LVIS instrument will be discussed.

Cell lineage patterns in the shoot meristem of the sunflower embryo in the dry seed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jegla, D.E.; Sussex, I.M.

1989-01-01

We mapped the fate of cells in the shoot meristem of the dry-seed embryo of sunflower, Helianthus annuus L. cv. Peredovic, using irradiation-induced somatic sectors. We analyzed 249 chlorophyll-deficient or glabrous (hairless) sectors generated in 236 plants. Most sectors observed in the inflorescence extended into vegetative nodes. Thus cell lineages that ultimately gave rise to reproductive structures also contributed to vegetative structures. No single sector extended the entire length of the shoot. Thus the shoot is not derived from one or a few apical initials. Rather, the position, vertical extent, and width of the sectors at different levels of themore » shoot suggest that the shoot is derived from three to four circumferential populations of cells in each of three cell layers of the embryo meristem. Sectors had no common boundaries even in plants with two or three independent sectors, but varied in extent and overlapped along the length of the shoot. Thus individual cells in a single circumferential population behaved independently to contribute lineages of different vertical extents to the growing shoot. The predicted number of circumferential populations of cells as well as the apparent cell number in each population was consistent with the actual number of cells in the embryo meristem observed in histological sections.« less

Research support of the WETNET Program

NASA Technical Reports Server (NTRS)

Estes, John E.; Mcgwire, Kenneth C.; Scepan, Joseph; Henderson, SY; Lawless, Michael

1995-01-01

This study examines various aspects of the Microwave Vegetation Index (MVI). MVI is a derived signal created by differencing the spectral response of the 37 GHz horizontally and vertically polarized passive microwave signals. The microwave signal employed to derive this index is thought to be primarily influenced by vegetation structure, vegetation growth, standing water, and precipitation. The state of California is the study site for this research. Imagery from the Special Sensor Microwave/Imager (SSM/I) is used for the creation of MVI datasets analyzed in this research. The object of this research is to determine whether MVI corresponds with some quantifiable vegetation parameter (such as vegetation density) or whether the index is more affected by known biogeophysical parameters such antecedent precipitation. A secondary question associated with the above is whether the vegetation attributes that MVI is employed to determine can be more easily and accurately evaluated by other remote sensing means. An important associated question to be addressed in the study is the effect of different multi-temporal composting techniques on the derived MVI dataset. This work advances our understanding of the fundamental nature of MVI by studying vegetation as a mixture of structural types, such as forest and grassland. The study further advances our understanding by creating multitemporal precipitation datasets to compare the affects of precipitation upon MVI. This work will help to lay the groundwork for the use of passive microwave spectral information either as an adjunct to visible and near infrared imagery in areas where that is feasible or for the use of passive microwave alone in areas of moderate cloud coverage. In this research, an MVI dataset, spanning the period February 15, 1989 through April 25, 1990, has been created using National Aeronautic and Space Administration (NASA) supplied brightness temperature data. Information from the DMSP satellite 37 GHz wavelength SSM/I sensor in both horizontal and vertical polarization has been processed using the MVI algorithm. In conjunction with the MVI algorithm a multitemporal compositing technique was used to create datasets that correspond to 14 day periods. In this technical report, Section Two contains background information on the State of California and the three MVI study sites. Section Three describes the methods used to create the MVI and independent variables datasets. Section Four presents the results of the experiment. Section Five summarizes and concludes the work.

Using Satellite and Airborne LiDAR to Model Woodpecker Habitat Occupancy at the Landscape Scale

PubMed Central

Vierling, Lee A.; Vierling, Kerri T.; Adam, Patrick; Hudak, Andrew T.

2013-01-01

Incorporating vertical vegetation structure into models of animal distributions can improve understanding of the patterns and processes governing habitat selection. LiDAR can provide such structural information, but these data are typically collected via aircraft and thus are limited in spatial extent. Our objective was to explore the utility of satellite-based LiDAR data from the Geoscience Laser Altimeter System (GLAS) relative to airborne-based LiDAR to model the north Idaho breeding distribution of a forest-dependent ecosystem engineer, the Red-naped sapsucker (Sphyrapicus nuchalis). GLAS data occurred within ca. 64 m diameter ellipses spaced a minimum of 172 m apart, and all occupancy analyses were confined to this grain scale. Using a hierarchical approach, we modeled Red-naped sapsucker occupancy as a function of LiDAR metrics derived from both platforms. Occupancy models based on satellite data were weak, possibly because the data within the GLAS ellipse did not fully represent habitat characteristics important for this species. The most important structural variables influencing Red-naped Sapsucker breeding site selection based on airborne LiDAR data included foliage height diversity, the distance between major strata in the canopy vertical profile, and the vegetation density near the ground. These characteristics are consistent with the diversity of foraging activities exhibited by this species. To our knowledge, this study represents the first to examine the utility of satellite-based LiDAR to model animal distributions. The large area of each GLAS ellipse and the non-contiguous nature of GLAS data may pose significant challenges for wildlife distribution modeling; nevertheless these data can provide useful information on ecosystem vertical structure, particularly in areas of gentle terrain. Additional work is thus warranted to utilize LiDAR datasets collected from both airborne and past and future satellite platforms (e.g. GLAS, and the planned IceSAT2 mission) with the goal of improving wildlife modeling for more locations across the globe. PMID:24324655

Incorporating Plant Phenology Dynamics in a Biophysical Canopy Model

NASA Technical Reports Server (NTRS)

Barata, Raquel A.; Drewry, Darren

2012-01-01

The Multi-Layer Canopy Model (MLCan) is a vegetation model created to capture plant responses to environmental change. Themodel vertically resolves carbon uptake, water vapor and energy exchange at each canopy level by coupling photosynthesis, stomatal conductance and leaf energy balance. The model is forced by incoming shortwave and longwave radiation, as well as near-surface meteorological conditions. The original formulation of MLCan utilized canopy structural traits derived from observations. This project aims to incorporate a plant phenology scheme within MLCan allowing these structural traits to vary dynamically. In the plant phenology scheme implemented here, plant growth is dependent on environmental conditions such as air temperature and soil moisture. The scheme includes functionality that models plant germination, growth, and senescence. These growth stages dictate the variation in six different vegetative carbon pools: storage, leaves, stem, coarse roots, fine roots, and reproductive. The magnitudes of these carbon pools determine land surface parameters such as leaf area index, canopy height, rooting depth and root water uptake capacity. Coupling this phenology scheme with MLCan allows for a more flexible representation of the structure and function of vegetation as it responds to changing environmental conditions.

Evaluation of Vertical Lacunarity Profiles in Forested Areas Using Airborne Laser Scanning Point Clouds

NASA Astrophysics Data System (ADS)

Székely, B.; Kania, A.; Standovár, T.; Heilmeier, H.

2016-06-01

The horizontal variation and vertical layering of the vegetation are important properties of the canopy structure determining the habitat; three-dimensional (3D) distribution of objects (shrub layers, understory vegetation, etc.) is related to the environmental factors (e.g., illumination, visibility). It has been shown that gaps in forests, mosaic-like structures are essential to biodiversity; various methods have been introduced to quantify this property. As the distribution of gaps in the vegetation is a multi-scale phenomenon, in order to capture it in its entirety, scale-independent methods are preferred; one of these is the calculation of lacunarity. We used Airborne Laser Scanning point clouds measured over a forest plantation situated in a former floodplain. The flat topographic relief ensured that the tree growth is independent of the topographic effects. The tree pattern in the plantation crops provided various quasi-regular and irregular patterns, as well as various ages of the stands. The point clouds were voxelized and layers of voxels were considered as images for two-dimensional input. These images calculated for a certain vicinity of reference points were taken as images for the computation of lacunarity curves, providing a stack of lacunarity curves for each reference points. These sets of curves have been compared to reveal spatial changes of this property. As the dynamic range of the lacunarity values is very large, the natural logarithms of the values were considered. Logarithms of lacunarity functions show canopy-related variations, we analysed these variations along transects. The spatial variation can be related to forest properties and ecology-specific aspects.

Advanced NASA Earth Science Mission Concept for Vegetation 3D Structure, Biomass and Disturbance

NASA Technical Reports Server (NTRS)

Ranson, K. Jon

2007-01-01

Carbon in forest canopies represents about 85% of the total carbon in the Earth's aboveground biomass (Olson et al., 1983). A major source of uncertainty in global carbon budgets derives from large errors in the current estimates of these carbon stocks (IPCC, 2001). The magnitudes and distributions of terrestrial carbon storage along with changes in sources and sinks for atmospheric C02 due to land use change remain the most significant uncertainties in Earth's carbon budget. These uncertainties severely limit accurate terrestrial carbon accounting; our ability to evaluate terrestrial carbon management schemes; and the veracity of atmospheric C02 projections in response to further fossil fuel combustion and other human activities. Measurements of vegetation three-dimensional (3D) structural characteristics over the Earth's land surface are needed to estimate biomass and carbon stocks and to quantify biomass recovery following disturbance. These measurements include vegetation height, the vertical profile of canopy elements (i.e., leaves, stems, branches), andlor the volume scattering of canopy elements. They are critical for reducing uncertainties in the global carbon budget. Disturbance by natural phenomena, such as fire or wind, as well as by human activities, such as forest harvest, and subsequent recovery, complicate the quantification of carbon storage and release. The resulting spatial and temporal heterogeneity of terrestrial biomass and carbon in vegetation make it very difficult to estimate terrestrial carbon stocks and quantify their dynamics. Vegetation height profiles and disturbance recovery patterns are also required to assess ecosystem health and characterize habitat. The three-dimensional structure of vegetation provides habitats for many species and is a control on biodiversity. Canopy height and structure influence habitat use and specialization, two fundamental processes that modify species richness and abundance across ecosystems. Accurate and consistent 3D measurements of forest structure at the landscape scale are needed for assessing impacts to animal habitats and biodiversity following disturbance.

Wind driven vertical transport in a vegetated, wetland water column with air-water gas exchange

NASA Astrophysics Data System (ADS)

Poindexter, C.; Variano, E. A.

2010-12-01

Flow around arrays of cylinders at low and intermediate Reynolds numbers has been studied numerically, analytically and experimentally. Early results demonstrated that at flow around randomly oriented cylinders exhibits reduced turbulent length scales and reduced diffusivity when compared to similarly forced, unimpeded flows (Nepf 1999). While horizontal dispersion in flows through cylinder arrays has received considerable research attention, the case of vertical dispersion of reactive constituents has not. This case is relevant to the vertical transfer of dissolved gases in wetlands with emergent vegetation. We present results showing that the presence of vegetation can significantly enhance vertical transport, including gas transfer across the air-water interface. Specifically, we study a wind-sheared air-water interface in which randomly arrayed cylinders represent emergent vegetation. Wind is one of several processes that may govern physical dispersion of dissolved gases in wetlands. Wind represents the dominant force for gas transfer across the air-water interface in the ocean. Empirical relationships between wind and the gas transfer coefficient, k, have been used to estimate spatial variability of CO2 exchange across the worlds’ oceans. Because wetlands with emergent vegetation are different from oceans, different model of wind effects is needed. We investigated the vertical transport of dissolved oxygen in a scaled wetland model built inside a laboratory tank equipped with an open-ended wind tunnel. Plastic tubing immersed in water to a depth of approximately 40 cm represented emergent vegetation of cylindrical form such as hard-stem bulrush (Schoenoplectus acutus). After partially removing the oxygen from the tank water via reaction with sodium sulfite, we used an optical probe to measure dissolved oxygen at mid-depth as the tank water re-equilibrated with the air above. We used dissolved oxygen time-series for a range of mean wind speeds to estimate the gas transfer coefficient, k, for both a vegetated condition and a control condition (no cylinders). The presence of cylinders in the tank substantially increased the rate of the gas transfer. For the highest wind speed, the gas transfer coefficient was several times higher when cylinders were present compared to when they were not. The gas transfer coefficient for the vegetated condition also proved sensitive to wind speed, increasing markedly with increasing mean wind speeds. Profiles of dissolved oxygen revealed well-mixed conditions in the bulk water column following prolonged air-flow above the water surface, suggesting application of the thin-film model is appropriate. The enhanced gas exchange observed might be explained by increased turbulent kinetic energy within the water column and the anisotropy of the cylinder array, which constrains horizontal motions more than vertical motions. Improved understanding of gas exchange in vegetated water columns may be of particularly use to investigations of carbon fluxes and soil accretion in wetlands. Reference: Nepf, H. (1999), Drag, turbulence, and diffusion in flow through emergent vegetation, Water Resour. Res., 35(2), 479-489.

Developing a global mixed-canopy, height-variable vegetation structure dataset for estimating global vegetation albedo by a clumped canopy radiative transfer scheme in the NASA Ent Terrestrial Biosphere Model and GISS GCM

NASA Astrophysics Data System (ADS)

Montes, Carlo; Kiang, Nancy Y.; Ni-Meister, Wenge; Yang, Wenze; Schaaf, Crystal; Aleinov, Igor; Jonas, Jeffrey A.; Zhao, Feng; Yao, Tian; Wang, Zhuosen; Sun, Qingsong; Carrer, Dominique

2016-04-01

Processes determining biosphere-atmosphere coupling are strongly influenced by vegetation structure. Thus, ecosystem carbon sequestration and evapotranspiration affecting global carbon and water balances will depend upon the spatial extent of vegetation, its vertical structure, and its physiological variability. To represent this globally, Dynamic Global Vegetation Models (DGVMs) coupled to General Circulation Models (GCMs) make use of satellite and/or model-based vegetation classifications often composed by homogeneous communities. This work aims at developing a new Global Vegetation Structure Dataset (GVSD) by incorporating varying vegetation heights for mixed plant communities to be used as boundary conditions to the Analytical Clumped Two-Stream (ACTS) canopy radiative transfer scheme (Ni-Meister et al., 2010) incorporated into the NASA Ent Terrestrial Biosphere Model (TBM), the DGVM coupled to the NASA Goddard Institute for Space Studies (GISS) GCM. Information sources about land surface and vegetation characteristics obtained from a number of earth observation platforms and algorithms include the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and plant functional types (PFTs) (Friedl et al., 2010), soil albedo derived from MODIS (Carrer et al., 2014), along with vegetation height from the Geoscience Laser Altimeter System (GLAS) on board ICESat (Ice, Cloud, and land Elevation Satellite) (Simard et al., 2011; Tang et al., 2014). Three widely used Leaf Area Index (LAI) products are compared as input to the GVSD and ACTS forcing in terms of vegetation albedo: Global Data Sets of Vegetation (LAI)3g (Zhu et al. 2013), Beijing Normal University LAI (Yuan et al., 2011), and MODIS MOD15A2H product (Yang et al., 2006). Further PFT partitioning is performed according to a climate classification utilizing the Climate Research Unit (CRU; Harris et al., 2013) and the NOAA Global Precipitation Climatology Centre (GPCC; Scheider et al., 2014) data. Final products are a GVSD consisting of mixed plant communities (e.g. mixed forests, savannas, mixed PFTs) following the Ecosystem Demography model (Moorcroft et al., 2001) approach represented by multi-cohort community patches at the sub-grid level of the GCM, which are ensembles of identical individuals whose differences are represented by PFTs, canopy height, density and vegetation structure sensitivity to allometric parameters. The performance of the Ent TBM in estimating VIS-NIR vegetation albedo by the new GVSD and ACTS is assessed first by comparison against the previous GISS GCM vegetation classification and prescribed Lambertian albedoes of Matthews (1984), and secondly, against MODIS global estimations and FLUXNET site-scale observations. Ultimately, this GVSD will serve as a template for community data sets, and be used as boundary conditions to the Ent TBM for prediction of biomass, carbon balances and GISS GCM climate.

Modelisation de l'architecture des forets pour ameliorer la teledetection des attributs forestiers

NASA Astrophysics Data System (ADS)

Cote, Jean-Francois

The quality of indirect measurements of canopy structure, from in situ and satellite remote sensing, is based on knowledge of vegetation canopy architecture. Technological advances in ground-based, airborne or satellite remote sensing can now significantly improve the effectiveness of measurement programs on forest resources. The structure of vegetation canopy describes the position, orientation, size and shape of elements of the canopy. The complexity of the canopy in forest environments greatly limits our ability to characterize forest structural attributes. Architectural models have been developed to help the interpretation of canopy structural measurements by remote sensing. Recently, the terrestrial LiDAR systems, or TLiDAR (Terrestrial Light Detection and Ranging), are used to gather information on the structure of individual trees or forest stands. The TLiDAR allows the extraction of 3D structural information under the canopy at the centimetre scale. The methodology proposed in my Ph.D. thesis is a strategy to overcome the weakness in the structural sampling of vegetation cover. The main objective of the Ph.D. is to develop an architectural model of vegetation canopy, called L-Architect (LiDAR data to vegetation Architecture), and to focus on the ability to document forest sites and to get information on canopy structure from remote sensing tools. Specifically, L-Architect reconstructs the architecture of individual conifer trees from TLiDAR data. Quantitative evaluation of L-Architect consisted to investigate (i) the structural consistency of the reconstructed trees and (ii) the radiative coherence by the inclusion of reconstructed trees in a 3D radiative transfer model. Then, a methodology was developed to quasi-automatically reconstruct the structure of individual trees from an optimization algorithm using TLiDAR data and allometric relationships. L-Architect thus provides an explicit link between the range measurements of TLiDAR and structural attributes of individual trees. L-Architect has finally been applied to model the architecture of forest canopy for better characterization of vertical and horizontal structure with airborne LiDAR data. This project provides a mean to answer requests of detailed canopy architectural data, difficult to obtain, to reproduce a variety of forest covers. Because of the importance of architectural models, L-Architect provides a significant contribution for improving the capacity of parameters' inversion in vegetation cover for optical and lidar remote sensing. Mots-cles: modelisation architecturale, lidar terrestre, couvert forestier, parametres structuraux, teledetection.

A terrestrial lidar assessment of climate change impacts on forest structure

NASA Astrophysics Data System (ADS)

van Aardt, J. A.; Kelbe, D.; Sacca, K.; Giardina, C. P.; Selmants, P. C.; Litton, C. M.; Asner, G. P.

2016-12-01

The projected impact of climate change on ecosystems has received much scientific attention, specifically related to geographical species shifts and carbon allocation. This study, however, was undertaken to assess the expected changes in tropical forest structure as a function of changing temperatures. Our study area is a constrained model ecological system and is located on the eastern flank of Mauna Kea Volcano, Hawaii, USA. Nine plots from this closed-canopy, tropical montane wet forest fall along an elevation-based 5.2°C mean annual temperature (MAT) gradient, where multiple other biotic and abiotic factors are held nearly constant. This MAT gradient has been used to assess subtle temperature effects on ecosystem functioning including carbon cycles, but less has been done on the effects of temperature on vegetation structure. We acquired vegetation structural data using a SICK-LMS151 terrestrial laser scanner (905 nm) for full 270x360° coverage. This Compact Biomass Lidar (CBL) was developed by Rochester Institute of Technology and the University of Massachusetts, Boston. Data for each plot along the temperature gradient were collected in a 20 m x 20 m configuration at a 5 m scan spacing. Initial challenges, related to the irregular radial scan pattern and registration of 25 scans per plot, were addressed in order to extract normalized vegetation density metrics and to mitigate occlusion effects, respectively. However, we believe that the CBL scans can be assessed independently, i.e., treating 25 scans/plot as a population sample. We derived height statistics, return density metrics, canopy rugosity, and higher-order metrics in order to describe the differences in vegetation structure, which ultimately will be tied to the elevation-induced temperature range. We hypothesized that, for this MAT gradient (i) vertical vegetation stratification; (ii) diameter distributions; and (iii) aboveground biomass will differ significantly, while more species-dependent canopy rugosity remain stable. Our results support these hypotheses, allowing for future studies of vegetation structural responses to static and dynamic climate drivers. The findings have implications for forest management, mitigation strategies to limit losses in carbon sequestration, and forest inventory in structurally complex forests.

Simulation Based Exploration of Critical Zone Dynamics in Intensively Managed Landscapes

NASA Astrophysics Data System (ADS)

Kumar, P.

2017-12-01

The advent of high-resolution measurements of topographic and (vertical) vegetation features using areal LiDAR are enabling us to resolve micro-scale ( 1m) landscape structural characteristics over large areas. Availability of hyperspectral measurements is further augmenting these LiDAR data by enabling the biogeochemical characterization of vegetation and soils at unprecedented spatial resolutions ( 1-10m). Such data have opened up novel opportunities for modeling Critical Zone processes and exploring questions that were not possible before. We show how an integrated 3-D model at 1m grid resolution can enable us to resolve micro-topographic and ecological dynamics and their control on hydrologic and biogeochemical processes over large areas. We address the computational challenge of such detailed modeling by exploiting hybrid CPU and GPU computing technologies. We show results of moisture, biogeochemical, and vegetation dynamics from studies in the Critical Zone Observatory for Intensively managed Landscapes (IMLCZO) in the Midwestern United States.

Spatial distribution of lacunarity of voxelized airborne LiDAR point clouds in various forest assemblages

NASA Astrophysics Data System (ADS)

Székely, Balázs; Kania, Adam; Standovár, Tibor; Heilmeier, Hermann

2015-04-01

Forest ecosystems have characteristic structure of features defined by various structural elements of different scales and vertical positions: shrub layers, understory vegetation, tree trunks, and branches. Furthermore in most of the cases there are superimposed structures in distributions (mosaic or island patterns) due to topography, soil variability, or even anthropogenic factors like past/present forest management activity. This multifaceted spatial context of the forests is relevant for many ecological issues, especially for maintaining forest biodiversity. Our aim in this study is twofold: (1) to quantify this structural variability laterally and vertically using lacunarity, and (2) to relate these results to relevant ecological features, i.e quantitatively described forest properties. Airborne LiDAR data of various quality and point density have been used for our study including a number of forested sites in Central and East Europe (partly Natura 2000 sites). The point clouds have been converted to voxel format and then converted to horizontal layers as images. These images were processed further for the lacunarity calculation. Areas of interest (AOIs) have been selected based on evaluation of the forested areas and auxiliary field information. The calculation has been performed for the AOIs for all available vertical data slices. The lacunarity function referring to a certain point and given vicinity varies horizontally and vertically, depending on the vegetation structure. Furthermore, the topography may also influence this property as the growth of plants, especially spacing and size of trees are influenced by the local topography and relief (e.g., slope, aspect). The comparisons of the flatland and hilly settings show interesting differences and the spatial patterns also vary differently. Because of the large amount of data resulting from these calculations, sophisticated methods are required to analyse the results. The large data amount then has been structured according to AOIs and relevant AOI pairs or small groups have been formed for comparative purposes. Change detection techniques have been applied to reveal fine differences. The spatial variation can be related to ecologically relevant forest characteristics. Data used in this study have been acquired in the framework of ChangeHabitat2 project (an IAPP Marie Curie Actions project of the European Union), in Hungarian-Slovakian Transnational Cooperation Programme 2007-2013, "Management of World Heritage Aggtelek Karst/Slovakian Karst Caves" (HUSK/1101/221/0180, Aggtelek NP). These studies were partly carried out in the project 'Multipurpose assessment serving forest biodiversity conservation in the Carpathian region of Hungary', Swiss-Hungarian Cooperation Programme (SH/4/13 Project). BS contributed as an Alexander von Humboldt Research Fellow.

Quantifying Vegetation Composition, Structure and Dynamics in Selected Australian Ecosystems: Science to Management

NASA Astrophysics Data System (ADS)

Phinn, S. R.; Scarth, P.; Armston, J.; Witte, C.; Danaher, T.; Flood, N.; Gill, T.; Lucas, R.

2011-12-01

Management of Australian ecosystems is carried out by state governments using information derived from satellite image data. The state of Queensland covers approximately 1.8 x 10^6 km^2 and uses satellite remote sensing and field survey programs to support legislated environmental monitoring, management and compliance activities.This poster outlines how the Joint Remote Sensing Research Program(JRSRP)delivered satellite image based data sets to address these activities by mapping foliage projective cover, vegetation height and biomass. Foliage projective cover (FPC), the vertically projected percentage cover of photosynthetic foliage of all strata, is produced from Landsat TM/ETM data using 88 scenes and over 1700 field sites. The JRSRP enabled government staff to be seconded to a university research group to work on the project, and the university provided postdoctoral and graduate student support. The JRSRP activities focussed on geometric and topographic corrections, BRDF corrections and time-series based approaches for correcting the archive of field survey and Landsat TM/ETM+ images. This has now progressed to a program using the entire Landsat TM/ETM+ archive on an annual basis and annual state-wide field survey data. The Landsat TM/ETM+ calibrations have been a critical input to the Landsat program's global vicarious calibration activities. Vegetation height is a critical parameter required for a range of state-wide activities and can be mapped accurately from field plots to regional areas using airborne Lidar. To develop statewide height estimates, an approach was developed using Icesat and existing vegetation community maps. By aggregating the spaceborne Icesat full waveform data within the mapped vegetation structure polygons it was possible to retrieve vegetation vertical structure information continuously across the landscape. This was used to derive mean canopy and understorey height, depth and density across Queensland, which was validated using airborne lidar data provided by the JRSRP. Biomass mapping is emerging as a critical environmental parameter for local, state and national agencies in Australia. Staff from JRSRP developed an approach with University of Aberystwyth in Wales, through JAXA's Kyoto and Carbon initiative, for acquiring ALOS PALSAR L-band image data, conducting geometric and radiometric corrections, and normalising for significant scene to scene differences in soil and vegetation moisture content. This pre-processing of 31 image strip time-series generated state-wide mosaics for Queensland that were then used with 1815 field survey sites collected across the state to produce a state-wide biomass estimation model for L-HV data, providing estimates for both remnant and non-remnant forests, with saturation at 263 Mg.Ha^-1 for 20% estimation error. The Joint Remote Sensing Research Program has enabled a sound approach to research and development for validated operational applications.

Resistance to uprooting of Alfalfa and Avena Sativa and related importance for flume experiments

NASA Astrophysics Data System (ADS)

Edmaier, K.; Crouzy, B.; Burlando, P.; Perona, P.

2012-04-01

Vegetation influences sediment dynamics by stabilizing the alluvial sediment with its root system. Thus, vegetation engineers the riparian ecosystem by contributing to the formation and stabilization of river bars and islands. The resistance to uprooting of young plants in non-cohesive sediment depends on the competition between flow induced drag and root growth timescales. The investigation of flow-sediment-plant interactions in situ is difficult since variables cannot be controlled and material hardly be collected. In order to investigate ecomorphological processes, laboratory experiments are essential and have gained importance in the last decade. To achieve a better understanding of the dependence of resistance to uprooting on the root system (length and structure) we conducted vertical uprooting experiments with Alfalfa and Avena Sativa which are both species that have been used in flume experiments on vegetation-flow interactions (e.g. Tal and Paola, 2010; Perona et al., in press). Seeds were seeded on quartz sand and vertically uprooted with constant velocity whereat the weight force required to uproot a seedling was measured. After uprooting, roots were scanned and analyzed and the correlation of root parameters with the uprooting work was studied. Total root length was found to be the best explanatory variable, in particular the uprooting work increases following a power law with increasing root length. The impact of other root parameters (main root length, root number, tortuosity) on the uprooting work was as well analyzed. Still, not all influencing root parameters could be captured, like the angle between roots or root hair distribution. Environmental conditions like grain size and saturation were also found to have an effect on the uprooting resistance of roots. So, lower saturated sediment results in a higher uprooting work. This work is a first step to better understand the energy regime for vegetation uprooting and its dependence on various biological and hydraulic variables. Future experiments using the same sediment and vegetation species will apply this knowledge to further investigate flow-vegetation-sediment interactions.

Organized turbulent motions in a hedgerow vineyard: effect of evolving canopy structure

NASA Astrophysics Data System (ADS)

Vendrame, Nadia; Tezza, Luca; Tha Paw U, Kyaw; Pitacco, Andrea

2017-04-01

Vegetation-atmosphere exchanges are determined by functional and structural properties of the plants together with environmental forcing. However, a fundamental aspect is the interaction of the canopy with the lower atmosphere. The vegetation deeply alters the composition and physical properties of the air flow, exchanging energy, matter and momentum with it. These processes take place in the bottom part of the atmospheric boundary layer where turbulence is the main mechanism transporting within-canopy air towards the mid- and upper atmospheric boundary layer and vice versa. Canopy turbulence is highly influenced by vegetation drag elements, determining the vertical profile of turbulent moments within the canopy. Canopies organized in rows, like vineyards, show peculiar turbulent transport dynamics. In addition, the morphological structure (phenology) of the vineyard is greatly variable seasonally, shifting from an empty canopy during vine dormancy to dense foliage in summer. The understanding of the canopy ventilation regime is related to several practical applications in vineyard management. For example, within-canopy turbulent motion is very important to predict small particles dispersion, like fungal spores, and minimize infection studying the effect on leaf wetness duration. Our study aims to follow the continuous evolution of turbulence characteristics and canopy structure during the growing season of a hedgerow vineyard, from bud break to fully developed canopy. The field experiment was conducted in a flat extensive vineyard in North-Eastern Italy, using a vertical array of five synchronous sonic anemometers within and above the canopy. Turbulent flow organization was greatly influenced by canopy structure. Turbulent coherent structures involved in momentum transport have been investigated using the classical quadrant analysis and a novel approach to identify dominant temporal scales. Momentum transport in the canopy was dominated by downward gusts showing increasing importance throughout the growing season. At the same time, transport intermittency increased with developing leaf density. The contribution by interaction terms, acting opposite to downward momentum flux, increased in the lower canopy. The analysis of event time scales revealed that momentum transport in the vineyard was dominated by sweeps of 2-4 s duration and ejections of 4-6 s duration, which can be summed to estimate an average duration of dominating coherent structures in the order of 6-10 s. The evolution of canopy morphology did not have any clear influence on structure duration.

Parametric analysis of synthetic aperture radar data acquired over truck garden vegetation

NASA Technical Reports Server (NTRS)

Wu, S. T.

1984-01-01

An airborne X-band SAR acquired multipolarization and multiflight pass SAR images over a truck garden vegetation area. Based on a variety of land cover and row crop direction variations, the vertical (VV) polarization data contain the highest contrast, while cross polarization contains the least. When the radar flight path is parallel to the row direction, both horizontal (HH) and VV polarization data contain very high return which masks out the specific land cover that forms the row structure. Cross polarization data are not that sensitive to row orientation. The inclusion of like and cross polarization data help delineate special surface features (e.g., row crop against non-row-oriented land cover, very-rough-surface against highly row-oriented surface).

Use of an airborne lidar system to model plant species composition and diversity of Mediterranean oak forests.

PubMed

Simonson, William D; Allen, Harriet D; Coomes, David A

2012-10-01

Airborne lidar is a remote-sensing tool of increasing importance in ecological and conservation research due to its ability to characterize three-dimensional vegetation structure. If different aspects of plant species diversity and composition can be related to vegetation structure, landscape-level assessments of plant communities may be possible. We examined this possibility for Mediterranean oak forests in southern Portugal, which are rich in biological diversity but also threatened. We compared data from a discrete, first-and-last return lidar data set collected for 31 plots of cork oak (Quercus suber) and Algerian oak (Quercus canariensis) forest with field data to test whether lidar can be used to predict the vertical structure of vegetation, diversity of plant species, and community type. Lidar- and field-measured structural data were significantly correlated (up to r= 0.85). Diversity of forest species was significantly associated with lidar-measured vegetation height (R(2) = 0.50, p < 0.001). Clustering and ordination of the species data pointed to the presence of 2 main forest classes that could be discriminated with an accuracy of 89% on the basis of lidar data. Lidar can be applied widely for mapping of habitat and assessments of habitat condition (e.g., in support of the European Species and Habitats Directive [92/43/EEC]). However, particular attention needs to be paid to issues of survey design: density of lidar points and geospatial accuracy of ground-truthing and its timing relative to acquisition of lidar data. ©2012 Society for Conservation Biology.

Estimation of Leaf Area Index and Plant Area Index of a Submerged Macrophyte Canopy Using Digital Photography

PubMed Central

Zhao, Dehua; Xie, Dong; Zhou, Hengjie; Jiang, Hao; An, Shuqing

2012-01-01

Non-destructive estimation using digital cameras is a common approach for estimating leaf area index (LAI) of terrestrial vegetation. However, no attempt has been made so far to develop non-destructive approaches to LAI estimation for aquatic vegetation. Using the submerged plant species Potamogeton malainus, the objective of this study was to determine whether the gap fraction derived from vertical photographs could be used to estimate LAI of aquatic vegetation. Our results suggested that upward-oriented photographs taken from beneath the water surface were more suitable for distinguishing vegetation from other objects than were downward-oriented photographs taken from above the water surface. Exposure settings had a substantial influence on the identification of vegetation in upward-oriented photographs. Automatic exposure performed nearly as well as the optimal trial exposure, making it a good choice for operational convenience. Similar to terrestrial vegetation, our results suggested that photographs taken for the purpose of distinguishing gap fraction in aquatic vegetation should be taken under diffuse light conditions. Significant logarithmic relationships were observed between the vertical gap fraction derived from upward-oriented photographs and plant area index (PAI) and LAI derived from destructive harvesting. The model we developed to depict the relationship between PAI and gap fraction was similar to the modified theoretical Poisson model, with coefficients of 1.82 and 1.90 for our model and the theoretical model, respectively. This suggests that vertical upward-oriented photographs taken from below the water surface are a feasible alternative to destructive harvesting for estimating PAI and LAI for the submerged aquatic plant Potamogeton malainus. PMID:23226557

Characterization, validation and intercomparison of clumping index maps from POLDER, MODIS, and MISR satellite data over reference sites

NASA Astrophysics Data System (ADS)

Pisek, Jan; He, Liming; Chen, Jing; Govind, Ajit; Sprintsin, Michael; Ryu, Youngryel; Arndt, Stefan; Hocking, Darren; Wardlaw, Timothy; Kuusk, Joel; Oliphant, Andrew; Korhonen, Lauri; Fang, Hongliang; Matteucci, Giorgio; Longdoz, Bernard; Raabe, Kairi

2015-04-01

Vegetation foliage clumping significantly alters its radiation environment and therefore affects vegetation growth as well as water and carbon cycles. The clumping index is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index (LAI) retrieved from mono-angle remote sensing and allows accurate separation of sunlit and shaded leaves in the canopy. Not accounting for the foliage clumping in LAI retrieval algorithms leads to substantial underestimation of actual LAI, especially for needleleaf forests. Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ~6 km resolution, from Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) product at 500 m resolution. Most recently the algorithm was applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this presentation we characterize and intercompare the three products over a set of sites representing diverse biomes and different canopy structures. The products are also directly validated with both in-situ vertical profiles and seasonal trajectories of clumping index. We illustrate that the vertical distribution of foliage and especially the effect of understory needs to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements respond to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can be propagated into the foliage clumping maps. Our results indicate that MODIS data and MISR data with 275 m in particular can provide good quality clumping index estimates at pertinent scales for modeling local carbon and energy fluxes.

Characterization, Validation and Intercomparison of Clumping Index Maps from POLDER, MODIS, and MISR Satellite Data Over Reference Sites

NASA Astrophysics Data System (ADS)

Pisek, J.; He, L.; Chen, J. M.; Govind, A.; Sprintsin, M.; Ryu, Y.; Arndt, S. K.; Hocking, D.; Wardlaw, T.; Kuusk, J.; Oliphant, A. J.; Korhonen, L.; Fang, H.; Matteucci, G.; Longdoz, B.; Raabe, K.

2015-12-01

Vegetation foliage clumping significantly alters its radiation environment and therefore affects vegetation growth as well as water and carbon cycles. The clumping index is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index (LAI) retrieved from mono-angle remote sensing and allows accurate separation of sunlit and shaded leaves in the canopy. Not accounting for the foliage clumping in LAI retrieval algorithms leads to substantial underestimation of actual LAI, especially for needleleaf forests. Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ~6 km resolution, from Moderate Resolution Imaging Spectroradiometer (MODIS) Bidirectional Reflectance Distribution Function (BRDF) product at 500 m resolution. Most recently the algorithm was applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this presentation we characterize and intercompare the three products over a set of sites representing diverse biomes and different canopy structures. The products are also directly validated with both in-situ vertical profiles and seasonal trajectories of clumping index. We illustrate that the vertical distribution of foliage and especially the effect of understory needs to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements respond to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can be propagated into the foliage clumping maps. Our results indicate that MODIS data and MISR data with 275 m resolution in particular can provide good quality clumping index estimates at pertinent scales for modeling local carbon and energy fluxes.

Mitigating Uncertainty from Vegetation Spatial Complexity with Highly Portable Lidar

NASA Astrophysics Data System (ADS)

Paynter, I.; Schaaf, C.; Peri, F.; Saenz, E. J.; Genest, D.; Strahler, A. H.; Li, Z.

2015-12-01

To fully utilize the excellent spatial coverage and temporal resolution offered by satellite resources for estimating ecological variables, fine-scale observations are required for comparison, calibration and validation. Lidar instruments have proved effective in estimating the properties of vegetation components of ecosystems, but they are often challenged by occlusion, especially in structurally complex and spatially fragmented ecosystems such as tropical forests. Increasing the range of view angles, both horizontally and vertically, by increasing the number of scans, can mitigate occlusion. However these scans must occur within the window of temporal stability for the ecosystem and vegetation property being measured. The Compact Biomass Lidar (CBL) is a TLS optimized for portability and scanning speed, developed and operated by University of Massachusetts Boston. This 905nm wavelength scanner achieves an angular resolution of 0.25 degrees at a rate of 33 seconds per scan. The ability to acquire many scans within narrow windows of temporal stability for ecological variables has facilitated the more complete investigation of ecosystem structural characteristics, and their expression as a function of view angle. The lightweight CBL has facilitated the use of alternative deployment platforms including towers, trams and masts, allowing analysis of the vertical structure of ecosystems, even in highly enclosed environments such as the sub-canopy of tropical forests where aerial vehicles cannot currently operate. We will present results from view angle analyses of lidar surveys of tropical rainforest in La Selva, Costa Rica where the CBL was deployed at heights up to 10m in Carbono long-term research plots utilizing a portable mast, and on a 25m stationary tower; and temperate forest at Harvard Forest, Massachusetts, USA, where the CBL has been deployed biannually at long-term research plots of hardwood and hemlock, as well as at heights of up to 25m utilizing a stationary tower.

a Point Cloud Classification Approach Based on Vertical Structures of Ground Objects

NASA Astrophysics Data System (ADS)

Zhao, Y.; Hu, Q.; Hu, W.

2018-04-01

This paper proposes a novel method for point cloud classification using vertical structural characteristics of ground objects. Since urbanization develops rapidly nowadays, urban ground objects also change frequently. Conventional photogrammetric methods cannot satisfy the requirements of updating the ground objects' information efficiently, so LiDAR (Light Detection and Ranging) technology is employed to accomplish this task. LiDAR data, namely point cloud data, can obtain detailed three-dimensional coordinates of ground objects, but this kind of data is discrete and unorganized. To accomplish ground objects classification with point cloud, we first construct horizontal grids and vertical layers to organize point cloud data, and then calculate vertical characteristics, including density and measures of dispersion, and form characteristic curves for each grids. With the help of PCA processing and K-means algorithm, we analyze the similarities and differences of characteristic curves. Curves that have similar features will be classified into the same class and point cloud correspond to these curves will be classified as well. The whole process is simple but effective, and this approach does not need assistance of other data sources. In this study, point cloud data are classified into three classes, which are vegetation, buildings, and roads. When horizontal grid spacing and vertical layer spacing are 3 m and 1 m respectively, vertical characteristic is set as density, and the number of dimensions after PCA processing is 11, the overall precision of classification result is about 86.31 %. The result can help us quickly understand the distribution of various ground objects.

Spectral properties of plant leaves pertaining to urban landscape design of broad-spectrum solar ultraviolet radiation reduction

NASA Astrophysics Data System (ADS)

Yoshimura, Haruka; Zhu, Hui; Wu, Yunying; Ma, Ruijun

2010-03-01

Human exposure to harmful ultraviolet (UV) radiation has important public health implications. Actual human exposure to solar UV radiation depends on ambient UV irradiance, and the latter is influenced by ground reflection. In urban areas with higher reflectivity, UV exposure occurs routinely. To discover the solar UV radiation regulation mechanism of vegetation, the spectral reflectance and transmittance of plant leaves were measured with a spectrophotometer. Typically, higher plants have low leaf reflectance (around 5%) and essentially zero transmittance throughout the UV region regardless of plant species and seasonal change. Accordingly, incident UV radiation decreases to 5% by being reflected and is reduced to zero by passing through a leaf. Therefore, stratified structures of vegetation are working as another terminator of UV rays, protecting whole terrestrial ecosystems, while vegetation at waterfronts contributes to protect aquatic ecosystems. It is possible to protect the human population from harmful UV radiation by urban landscape design of tree shade and the botanical environment. Even thin but uniformly distributed canopy is effective in attenuating UV radiation. To intercept diffuse radiation, UV screening by vertical structures such as hedges should be considered. Reflectivity of vegetation is around 2%, as foliage surfaces reduce incident UV radiation via reflection, while also eliminating it by transmittance. Accordingly, vegetation reduces incident UV radiation to around 2% by reflection. Vegetation influence on ambient UV radiation is broad-spectrum throughout the UV region. Only trees provide cool UV protective shade. Urban landscapes aimed at abating urban heat islands integrated with a reduction of human UV over-exposure would contribute to mitigation of climate change.

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.; Shroder, John F.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four-dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least-studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems are determined by the many interactions among physical and biological processes. Conservation and restoration of the valuable ecosystem services that floodplains provide depend on improved understanding and predictive models of interactive system controls and behavior.

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems are determined by the many interactions among physical and biological processes. Conservation and restoration of the valuable ecosystem services that floodplains provide depends on improved understanding and predictive models of interactive system controls and behavior.

Combining high fidelity simulations and real data for improved small-footprint waveform lidar assessment of vegetation structure (Invited)

NASA Astrophysics Data System (ADS)

van Aardt, J. A.; Wu, J.; Asner, G. P.

2010-12-01

Our understanding of vegetation complexity and biodiversity, from a remote sensing perspective, has evolved from 2D species diversity to also include 3D vegetation structural diversity. Attempts at using image-based approaches for structural assessment have met with reasonable success, but 3D remote sensing technologies, such as radar and light detection and ranging (lidar), are arguably more adept at sensing vegetation structure. While radar-derived structure metrics tend to break down at high biomass levels, novel waveform lidar systems present us with new opportunities for detailed and scalable structural characterization of vegetation. These sensors digitize the entire backscattered energy profile at high spatial and vertical resolutions and often at off-nadir angles. Research teams at Rochester Institute of Technology (RIT) and Carnegie Institution for Science have been using airborne data from the Carnegie Airborne Observatory (CAO) to assess vegetation structure and variation in savanna ecosystems in and around the Kruger National Park, South Africa. It quickly became evident that (i) pre-processing of small-footprint waveform data is a critical step prior to testing scientific hypotheses, (ii) a number of assumptions of how vegetation structure is expressed in these 3D signals need to be evaluated, and very importantly (iii) we need to re-evaluate our linkages between coarse in-field measurements, e.g., volume, biomass, leaf area index (LAI), and metrics derived from waveform lidar. Research has progressed to the stage where we have evaluated various pre-processing steps, e.g., convolution via the Wiener filter, Richardson-Lucy, and non-negative least squares algorithms, and the coupling of waveform voxels to tree structure in a simulation environment. This was done in the MODTRAN-based Digital Imaging and Remote Sensing Image Generation (DIRSIG) simulation environment, developed at RIT. We generated "truth" cross-section datasets of detailed virtual trees in this environment and evaluated inversion approaches to tree structure estimation. Various outgoing pulse widths, tree structures, and a noise component were included as part of the simulation effort. Results, for example, have shown that the Richardson-Lucy algorithm outperforms other approaches in terms of retrieval of known structural information, that our assumption regarding the position of the ground surface needs re-evaluation, and has shed light on herbaceous biomass and waveform interactions and the impact of outgoing pulse width on assessments. These efforts have gone a long way in providing a solid foundation for analysis and interpretation of actual waveform data from the savanna study area. We expect that newfound knowledge with respect to waveform-target interactions from these simulations will also aid efforts to reconstruct 3D trees from real data and better describe associated structural diversity. Results will be presented at the conference.

Vertical stratification of forest canopy for segmentation of understory trees within small-footprint airborne LiDAR point clouds

NASA Astrophysics Data System (ADS)

Hamraz, Hamid; Contreras, Marco A.; Zhang, Jun

2017-08-01

Airborne LiDAR point cloud representing a forest contains 3D data, from which vertical stand structure even of understory layers can be derived. This paper presents a tree segmentation approach for multi-story stands that stratifies the point cloud to canopy layers and segments individual tree crowns within each layer using a digital surface model based tree segmentation method. The novelty of the approach is the stratification procedure that separates the point cloud to an overstory and multiple understory tree canopy layers by analyzing vertical distributions of LiDAR points within overlapping locales. The procedure does not make a priori assumptions about the shape and size of the tree crowns and can, independent of the tree segmentation method, be utilized to vertically stratify tree crowns of forest canopies. We applied the proposed approach to the University of Kentucky Robinson Forest - a natural deciduous forest with complex and highly variable terrain and vegetation structure. The segmentation results showed that using the stratification procedure strongly improved detecting understory trees (from 46% to 68%) at the cost of introducing a fair number of over-segmented understory trees (increased from 1% to 16%), while barely affecting the overall segmentation quality of overstory trees. Results of vertical stratification of the canopy showed that the point density of understory canopy layers were suboptimal for performing a reasonable tree segmentation, suggesting that acquiring denser LiDAR point clouds would allow more improvements in segmenting understory trees. As shown by inspecting correlations of the results with forest structure, the segmentation approach is applicable to a variety of forest types.

Sediment infilling and wetland formation dynamics in an active crevasse splay of the Mississippi River delta

USGS Publications Warehouse

Cahoon, Donald R.; White, David A.; Lynch, James C.

2011-01-01

Crevasse splay environments provide a mesocosm for evaluating wetland formation and maintenance processes on a decadal time scale. Site elevation, water levels, vertical accretion, elevation change, shallow subsidence, and plant biomass were measured at five habitats along an elevation gradient to evaluate wetland formation and development in Brant Pass Splay; an active crevasse splay of the Balize delta of the Mississippi River. The processes of vertical development (vertical accretion, elevation change, and shallow subsidence) were measured with the surface elevation table–marker horizon method. There were three distinct stages to the accrual of elevation capital and wetland formation in the splay: sediment infilling, vegetative colonization, and development of a mature wetland community. Accretion, elevation gain, and shallow subsidence all decreased by an order of magnitude from the open water (lowest elevation) to the forest (highest elevation) habitats. Vegetative colonization occurred within the first growing season following emergence of the mud surface. An explosively high rate of below-ground production quickly stabilized the loosely consolidated sub-aerial sediments. After emergent vegetation colonization, vertical development slowed and maintenance of marsh elevation was driven both by sediment trapping by the vegetation and accumulation of plant organic matter in the soil. Continued vertical development and survival of the marsh then depended on the health and productivity of the plant community. The process of delta wetland formation is both complex and nonlinear. Determining the dynamics of wetland formation will help in understanding the processes driving the past building of the delta and in developing models for restoring degraded wetlands in the Mississippi River delta and other deltas around the world.

High spatial resolution three-dimensional mapping of vegetation spectral dynamics using computer vision and hobbyist unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Dandois, J. P.; Ellis, E. C.

2013-12-01

High spatial resolution three-dimensional (3D) measurements of vegetation by remote sensing are advancing ecological research and environmental management. However, substantial economic and logistical costs limit this application, especially for observing phenological dynamics in ecosystem structure and spectral traits. Here we demonstrate a new aerial remote sensing system enabling routine and inexpensive aerial 3D measurements of canopy structure and spectral attributes, with properties similar to those of LIDAR, but with RGB (red-green-blue) spectral attributes for each point, enabling high frequency observations within a single growing season. This 'Ecosynth' methodology applies photogrammetric ''Structure from Motion'' computer vision algorithms to large sets of highly overlapping low altitude (< 130 m) aerial photographs acquired using off-the-shelf digital cameras mounted on an inexpensive (< USD$4000), lightweight (< 2 kg), hobbyist-grade unmanned aerial system (UAS). Ecosynth 3D point clouds with densities of 30 - 67 points m-2 were produced using commercial computer vision software from digital photographs acquired repeatedly by UAS over three 6.25 ha (250 m x 250 m) Temperate Deciduous forest sites in Maryland USA. Ecosynth canopy height maps (CHMs) were strong predictors of field-measured tree heights (R2 0.63 to 0.84) and were highly correlated with a LIDAR CHM (R 0.87) acquired 4 days earlier, though Ecosynth-based estimates of aboveground biomass densities included significant errors (31 - 36% of field-based estimates). Repeated scanning of a 0.25 ha forested area at six different times across a 16 month period revealed ecologically significant dynamics in canopy color at different heights and a structural shift upward in canopy density, as demonstrated by changes in vertical height profiles of point density and relative RGB brightness. Changes in canopy relative greenness were highly correlated (R2 = 0.88) with MODIS NDVI time series for the same area and vertical differences in canopy color revealed the early green up of the dominant canopy species, Liriodendron tulipifera, strong evidence that Ecosynth time series measurements capture vegetation structural and spectral dynamics at the spatial scale of individual trees. Observing canopy phenology in 3D at high temporal resolutions represents a breakthrough in forest ecology. Inexpensive user-deployed technologies for multispectral 3D scanning of vegetation at landscape scales (< 1 km2) heralds a new era of participatory remote sensing by field ecologists, community foresters and the interested public.

Infrared temperature measurements over bare soil and vegetation - A HAPEX perspective

NASA Technical Reports Server (NTRS)

Carlson, Toby N.; Perry, Eileen M.; Taconet, Odile

1987-01-01

Preliminary analyses of aircraft and ground measurements made in France during the HAPEX experiment show that horizontal radiometric surface temperature variations, as viewed by aircraft, can reflect the vertical profile of soil moisture (soil versus root zone) because of horizontal variations in vegetation density. Analyses based on one day's data show that, although horizontal variations in soil moisture were small, the vertical differences between a dry surface and a wet root zone were large. Horizontal temperature differences between bare soil, corn and oats reflect differences in the fractional vegetation cover, as seen by the radiometer. On the other hand, these horizontal variations in radiometric surface temperature seem to reflect real horizontal variations in surface turbulent energy fluxes.

Geomorphometric correlations of vegetation cover properties and topographic karst features based on high-resolution LiDAR DTM of Aggtelek Karst, NE Hungary

NASA Astrophysics Data System (ADS)

Székely, Balázs; Telbisz, Tamás; Koma, Zsófia; Kelemen, Kristóf; Szmorad, Ferenc; Deák, Márton; Látos, Tamás; Standovár, Tibor

2015-04-01

Topography and lithology are two major factors influencing the vegetation cover, its mosaic pattern and lateral transitions. In karstic areas the topography has a high diversity, microtopographic landforms influence the local ecological setting, vegetation structure. Presence of sinkholes of various sizes and geometric arrangements causes rapid lateral variation of the slope, aspect patterns as well as highly modify the soil water balance in time and space. These diversity of factors defines a mosaicked habitat pattern for vegetation assemblages. The World Heritage Site Aggtelek Karst/Slovakian Karst Caves has characteristic natural and environmental properties concerning the geomorphological as well as the ecological values. In order to be able to study the topographic influence on the ecological setting, a high-resolution digital terrain model (DTM) and digital surface model (DSM) have been derived from airborne laser scanning data depicting the karstic micro- and macrotopographic Landscape elements and the envelope surface of the canopy. Additional vegetation parameters like closure and average height have been derived from a normalized digital surface model (nDSM). Extensive mapping of vegetation properties has been carried out: centered on points of a grid array several vegetation-specific data - including composition and structure of tree and shrub layers, herbacesous vegetation and tree regeneration - have been acquired. Various classification patterns - based on trees pecies composition, vertical vegetation structure - have been derived from this data set. The comparison of the vegetation classification data and the geomorphometric DTM derivatives yielded interesting results. Certain vegetation characteristics often correlate with the geomorphometric properties. We interpret this similarity as sensitivity of vegetion to fine-scale variations in geomorphic properties like aspect, illumination conditions and soil properties. However, in many cases the vegetation pattern shows no correlation with natural settings. It may be the result of human impact, which actively formed the local land use in these hilly-low mountain karst area since the Middle Ages. These studies have been financed partly by the following projects: data acquisition: "Hungarian-Slovakian Transnational Cooperation Programme 2007-2013", "Management of World Heritage Aggtelek Karst/Slovakian Karst Caves" (HUSK/1101/221/0180, Aggtelek NP), data evaluation: 'Multipurpose assessment serving forest biodiversity conservation in the Carpathian region of Hungary', Swiss-Hungarian Cooperation Programme (SH/4/13 Project), and Hungarian National Research Fund OTKA NK83400 and OTKA 104811. BS contributed as an Alexander von Humboldt Research Fellow, TT was supported by the János Bolyai Scolarship of the Hungarian Academy of Sciences.

Russia: Saratov

Atmospheric Science Data Center

2013-04-17

... to differences in brightness and texture between bare soil and vegetated land. The chestnut-colored soils in this region are brighter ... of vegetation relative to the nadir camera, which sees more soil. In spring, therefore, the scene is brightest in the vertical view and ...

Role of vegetation on erosion processes: experimental investigation

NASA Astrophysics Data System (ADS)

Termini, Donatella

2014-05-01

Investigations on soil-system ecology are ever more oriented toward quantitative information based on the study of the linkages between physical processes and ecological response in rivers. As it is known, in presence of vegetation, the hydrodynamics characteristics of flow are principally determined by the mutual interrelation between the flow velocity field and the hydraulic behavior (completely submerged or emergent) of the vegetation elements. Much effort has been made toward identifying the theoretical law to interpret the vertical profile of flow longitudinal velocity in vegetated channels. Many theoretical and experimental studies in laboratory channels have been carried out and especially the case of submerged flexible vegetation has been examined (Termini, 2012). The effects of vegetation on flow velocity are significant and of crucial importance for stabilizing sediments and reducing erosion. Vegetation has a complex effect on walls roughness and the study of the hydrodynamic conditions of flow is difficult. Although most studies based on the "boundary layer" scheme so that the hydrodynamic conditions inside and above the vegetated layer are considered separately, some authors (Ghisalberti and Nepft, 2002; Carollo et al., 2008) claim that the "mixing layer" scheme is more appropriate to define the velocity profile both inside and outside the vegetated layer. Experimental program has been recently carried out in two laboratory flumes constructed at the laboratory of Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali - University of Palermo (Italy) with real and flexible vegetation on the bed. In this paper, attention is paid to the influence of vegetation on the erosion processes both on the bed and on the channel banks. The structure of the detailed flow velocity field is analyzed and compared with that obtained in absence of vegetation. Attention is then devoted to the analysis of soil erosion mechanism. Carollo F.G., Ferro V., Termini D. (2008). Flow velocity profile and turbulence characteristics in a vegetated straight flume. International Congress Riverflow 2008- Cesnme - Izmir (Turkey) 3-5 September Ghisalberti, M. & Nepf, H. M. 2002. Mixing layer and coherent structures in vegetated acquatic flows. Journal of Geophysical Reseach 107(2). Termini D. (2012). Experimental investigation on the role of vegetation on sediment transport mechanism: review of recent results - 9th ISE - International Symposium on Ecohydraulics - 2012, ISSN 0945-358X Vienna - CD proceedings-

Full-waveform and discrete-return lidar in salt marsh environments: An assessment of biophysical parameters, vertical uncertatinty, and nonparametric dem correction

NASA Astrophysics Data System (ADS)

Rogers, Jeffrey N.

High-resolution and high-accuracy elevation data sets of coastal salt marsh environments are necessary to support restoration and other management initiatives, such as adaptation to sea level rise. Lidar (light detection and ranging) data may serve this need by enabling efficient acquisition of detailed elevation data from an airborne platform. However, previous research has revealed that lidar data tend to have lower vertical accuracy (i.e., greater uncertainty) in salt marshes than in other environments. The increase in vertical uncertainty in lidar data of salt marshes can be attributed primarily to low, dense-growing salt marsh vegetation. Unfortunately, this increased vertical uncertainty often renders lidar-derived digital elevation models (DEM) ineffective for analysis of topographic features controlling tidal inundation frequency and ecology. This study aims to address these challenges by providing a detailed assessment of the factors influencing lidar-derived elevation uncertainty in marshes. The information gained from this assessment is then used to: 1) test the ability to predict marsh vegetation biophysical parameters from lidar-derived metrics, and 2) develop a method for improving salt marsh DEM accuracy. Discrete-return and full-waveform lidar, along with RTK GNSS (Real-time Kinematic Global Navigation Satellite System) reference data, were acquired for four salt marsh systems characterized by four major taxa (Spartina alterniflora, Spartina patens, Distichlis spicata, and Salicornia spp.) on Cape Cod, Massachusetts. These data were used to: 1) develop an innovative combination of full-waveform lidar and field methods to assess the vertical distribution of aboveground biomass as well as its light blocking properties; 2) investigate lidar elevation bias and standard deviation using varying interpolation and filtering methods; 3) evaluate the effects of seasonality (temporal differences between peak growth and senescent conditions) using lidar data flown in summer and spring; 4) create new products, called Relative Uncertainty Surfaces (RUS), from lidar waveform-derived metrics and determine their utility; and 5) develop and test five nonparametric regression model algorithms (MARS -- Multivariate Adaptive Regression, CART -- Classification and Regression Trees, TreeNet, Random Forests, and GPSM -- Generalized Path Seeker) with 13 predictor variables derived from both discrete and full waveform lidar sources in order to develop a method of improving lidar DEM quality. Results of this study indicate strong correlations for Spartina alterniflora (r > 0.9) between vertical biomass (VB), the distribution of vegetation biomass by height, and vertical obscuration (VO), the measure of the vertical distribution of the ratio of vegetation to airspace. It was determined that simple, feature-based lidar waveform metrics, such as waveform width, can provide new information to estimate salt marsh vegetation biophysical parameters such as vegetation height. The results also clearly illustrate the importance of seasonality, species, and lidar interpolation and filtering methods on elevation uncertainty in salt marshes. Relative uncertainty surfaces generated from lidar waveform features were determined useful in qualitative/visual assessment of lidar elevation uncertainty and correlate well with vegetation height and presence of Spartina alterniflora. Finally, DEMs generated using full-waveform predictor models produced corrections (compared to ground based RTK GNSS elevations) with R2 values of up to 0.98 and slopes within 4% of a perfect 1:1 correlation. The findings from this research have strong potential to advance tidal marsh mapping, research and management initiatives.

What Does a Multilayer Canopy Model Tell Us About Our Current Understanding of Snow-Canopy Unloading?

NASA Astrophysics Data System (ADS)

McGowan, L. E.; Paw U, K. T.; Dahlke, H. E.

2017-12-01

In the Western U.S., future water resources depend on the forested mountain snowpack. The variations in and estimates of forest mountain snow volume are vital to projecting annual water availability; yet, snow forest processes are not fully known. Most snow models calculate snow-canopy unloading based on time, temperature, Leaf Area Index (LAI), and/or wind speed. While models crudely consider the canopy shape via LAI, current models typically do not consider the vertical canopy structure or varied energetics within multiple canopy layers. Vertical canopy structure influences the spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability. Within the canopy both the snowpack and energetic exposures to the snowpack (wind, shortwave and longwave radiation, turbulent heat fluxes etc.) vary widely in the vertical. The water and energy balance in each layer is dependent on all other layers. For example, increased snow canopy content in the top of the canopy will reduce available shortwave radiation at the bottom and snow unloading in a mid-layer can cascade and remove snow from all the lower layers. We examined vertical interactions and structures of the forest canopy on the impact of unloading utilizing the Advanced Canopy-Atmosphere-Soil-Algorithm (ACASA), a multilayer soil-vegetation-atmosphere numerical model based on higher-order closure of turbulence equations. Our results demonstrate how a multilayer model can be used to elucidate the physical processes of snow unloading, and could help researchers better parameterize unloading in snow-hydrology models.

Robotic tilt table reduces the occurrence of orthostatic hypotension over time in vegetative states.

PubMed

Taveggia, Giovanni; Ragusa, Ivana; Trani, Vincenzo; Cuva, Daniele; Angeretti, Cristina; Fontanella, Marco; Panciani, Pier Paolo; Borboni, Alberto

2015-06-01

The aim of this study is to evaluate the effects of verticalization with or without combined movement of the lower limbs in patients in a vegetative state or a minimally conscious state. In particular, we aimed to study whether, in the group with combined movement, there was better tolerance to verticalization. This was a randomized trial conducted in a neurorehabilitation hospital. Twelve patients with vegetative state and minimally conscious state 3-18 months after acute acquired brain injuries were included. Patients were randomized into A and B treatment groups. Study group A underwent verticalization with a tilt table at 65° and movimentation of the lower limbs with a robotic system for 30 min three times a week for 24 sessions. Control group B underwent the same rehabilitation treatment, with a robotic verticalization system, but an inactive lower-limb movement system. Systolic and diastolic blood pressure and heart rate were determined. Robotic movement of the lower limbs can reduce the occurrence of orthostatic hypotension in hemodynamically unstable patients. Despite the small number of patients involved (only eight patients completed the trial), our results indicate that blood pressures and heart rate can be stabilized better (with) by treatment with passive leg movements in hemodynamically unstable patients.

A two-dimensional hydrodynamic model of turbulent transfer of CO2 and H2O over a heterogeneous land surface

NASA Astrophysics Data System (ADS)

Mukhartova, Yu. V.; Krupenko, A. S.; Mangura, P. A.; Levashova, N. T.

2018-01-01

A two-dimensional hydrodynamic model was developed and applied to describe turbulent fluxes of CO2 and H2O within the atmospheric surface layer over a heterogeneous land surface featuring mosaic vegetation and complex topography. Numerical experiments were carried out with a 4.5-km profile that crosses a hilly region in the central part of European Russia, with the diverse land-use patterns (bare soil, crop areas, grasslands, and forests). The results showed very strong variability of the vertical and horizontal turbulent CO2 and H2O fluxes. The standard deviations of the vertical fluxes were estimated for separate profile sections with uniform vegetation cover for daylight conditions in summer, and they were comparable with the mean vertical fluxes for corresponding sections. The highest horizontal turbulent fluxes occurred at the boundaries between different plant communities and at irregularities in surface profile. In some cases, these fluxes reached 10-20% of the absolute values of the mean vertical fluxes for corresponding profile sections. Significant errors in estimating the local and integrated fluxes e.g. when using the eddy covariance technique, can result from ignoring the surface topography, even in the case of relatively large plots with uniform vegetation cover.

African Savanna-Forest Boundary Dynamics: A 20-Year Study

PubMed Central

Cuni-Sanchez, Aida; White, Lee J. T.; Calders, Kim; Jeffery, Kathryn J.; Abernethy, Katharine; Burt, Andrew; Disney, Mathias; Gilpin, Martin; Gomez-Dans, Jose L.; Lewis, Simon L.

2016-01-01

Recent studies show widespread encroachment of forest into savannas with important consequences for the global carbon cycle and land-atmosphere interactions. However, little research has focused on in situ measurements of the successional sequence of savanna to forest in Africa. Using long-term inventory plots we quantify changes in vegetation structure, above-ground biomass (AGB) and biodiversity of trees ≥10 cm diameter over 20 years for five vegetation types: savanna; colonising forest (F1), monodominant Okoume forest (F2); young Marantaceae forest (F3); and mixed Marantaceae forest (F4) in Lopé National Park, central Gabon, plus novel 3D terrestrial laser scanning (TLS) measurements to assess forest structure differences. Over 20 years no plot changed to a new stage in the putative succession, but F1 forests strongly moved towards the structure, AGB and diversity of F2 forests. Overall, savanna plots showed no detectable change in structure, AGB or diversity using this method, with zero trees ≥10 cm diameter in 1993 and 2013. F1 and F2 forests increased in AGB, mainly as a result of adding recruited stems (F1) and increased Basal Area (F2), whereas F3 and F4 forests did not change substantially in structure, AGB or diversity. Critically, the stability of the F3 stage implies that this stage may be maintained for long periods. Soil carbon was low, and did not show a successional gradient as for AGB and diversity. TLS vertical plant profiles showed distinctive differences amongst the vegetation types, indicating that this technique can improve ecological understanding. We highlight two points: (i) as forest colonises, changes in biodiversity are much slower than changes in forest structure or AGB; and (ii) all forest types store substantial quantities of carbon. Multi-decadal monitoring is likely to be required to assess the speed of transition between vegetation types. PMID:27336632

African Savanna-Forest Boundary Dynamics: A 20-Year Study.

PubMed

Cuni-Sanchez, Aida; White, Lee J T; Calders, Kim; Jeffery, Kathryn J; Abernethy, Katharine; Burt, Andrew; Disney, Mathias; Gilpin, Martin; Gomez-Dans, Jose L; Lewis, Simon L

2016-01-01

Recent studies show widespread encroachment of forest into savannas with important consequences for the global carbon cycle and land-atmosphere interactions. However, little research has focused on in situ measurements of the successional sequence of savanna to forest in Africa. Using long-term inventory plots we quantify changes in vegetation structure, above-ground biomass (AGB) and biodiversity of trees ≥10 cm diameter over 20 years for five vegetation types: savanna; colonising forest (F1), monodominant Okoume forest (F2); young Marantaceae forest (F3); and mixed Marantaceae forest (F4) in Lopé National Park, central Gabon, plus novel 3D terrestrial laser scanning (TLS) measurements to assess forest structure differences. Over 20 years no plot changed to a new stage in the putative succession, but F1 forests strongly moved towards the structure, AGB and diversity of F2 forests. Overall, savanna plots showed no detectable change in structure, AGB or diversity using this method, with zero trees ≥10 cm diameter in 1993 and 2013. F1 and F2 forests increased in AGB, mainly as a result of adding recruited stems (F1) and increased Basal Area (F2), whereas F3 and F4 forests did not change substantially in structure, AGB or diversity. Critically, the stability of the F3 stage implies that this stage may be maintained for long periods. Soil carbon was low, and did not show a successional gradient as for AGB and diversity. TLS vertical plant profiles showed distinctive differences amongst the vegetation types, indicating that this technique can improve ecological understanding. We highlight two points: (i) as forest colonises, changes in biodiversity are much slower than changes in forest structure or AGB; and (ii) all forest types store substantial quantities of carbon. Multi-decadal monitoring is likely to be required to assess the speed of transition between vegetation types.

Differentiation characteristics and source analysis of heavy metals in typical brown soil under different vegetation

NASA Astrophysics Data System (ADS)

Dong, Zhicheng; Zhang, Lina; Li, Xueshuang; Lv, Shuangyan; He, Shijie; Liu, Ying; Ma, Xuanxuan

2017-08-01

Anomalous enrichment of soil elements (especially heavy metals) has aroused popular attention in China. In order to discuss distribution characteristics and analyze sources of elements in brown soil, field investigation and sample collection were carried out under different vegetation (cherry, apple, bamboos and pine) in Qixia, a typical apple production base in China. Element contents, pH, electrical conductivity (EC) and magnetic susceptibility (MS) were tested. Results showed that element concentrations were about roughly 2.48 times as China’s background values, while significantly lower than the class ii of National soil Environment Quality Standard (Ni excepted). Meanwhile, vertical distribution and accumulation characteristics of elements in typical brown soil were significantly different under different vegetation. In detail, elements (Zn excepted) of Pine soil accumulated in surface, while they (Cd, Arsenic excepted) increased with depth under other vegetation. Moreover, pH and EC changed like elements, while MS was exactly opposite. It was found that those differences above were mainly caused by human activities (such as improper use of fertilizer, pesticide and inadequate use of organic fertilizer, etc.). Additionally, differences in composition and decomposition rate of vegetation litter also resulted in vertical differentiations of soil elements under different vegetation.

Short-chain chlorinated paraffins in the soils of two different Chinese cities: Occurrence, homologue patterns and vertical migration.

PubMed

Huang, Yumei; Chen, Laiguo; Feng, Yongbin; Ye, Zhixiang; He, Qiusheng; Feng, Qianhua; Qing, Xian; Liu, Ming; Gao, Bo

2016-07-01

Short-chain chlorinated paraffins (SCCPs) are candidate persistent organic pollutants (POPs) that are under review by the Stockholm Convention. China is currently the largest producer and consumer of chlorinated paraffins (CPs). To study the environmental behavior and fate of SCCPs in the soils of urban and suburban regions, the SCCP concentrations in 88 topsoils and 15 soil columns from land of different use types (e.g., woodland, vegetable field, paddy field and greenbelt) from Guangzhou and Chengdu have been determined. The SCCP concentrations in topsoils from Guangzhou (range: 1.45-25.5ngg(-1) dry weight (dw), average: 10.3ngg(-1) dw) were much higher than those from Chengdu (range: 0.218-3.26ngg(-1) dw, average: 1.43ngg(-1) dw). When compared to previously reported SCCP levels for topsoils from other areas, the SCCP concentrations measured in the present work were quite low. Much higher SCCP concentrations were observed in the greenbelt topsoils from Chengdu relative to the values measured from woodlands and vegetable and paddy fields. The composition profiles suggest that C10Cl6-10 and C11-13Cl6-8 were the major groups of SCCPs in topsoils from the woodlands and vegetable and paddy fields in Guangzhou and Chengdu. Vertical variations of the SCCP concentrations in the soil columns suggest that less chlorinated SCCPs (Cl5-6-SCCPs) are more capable of migrating to the deeper-layer soils than more chlorinated ones (Cl9-10-SCCPs). The SCCP concentrations displayed little dependence on organic matter (OM) for most topsoils (p>0.05), indicating that OM is not the controlling factor in the distribution of SCCPs in the soils. This study analyzed the occurrence, homologue patterns and vertical migration of SCCPs in the topsoils of two Chinese cities with different industrial structures and climate conditions. Copyright © 2016 Elsevier B.V. All rights reserved.

Vegetation Disturbance and Recovery Following a Rare Windthrow Event in the Great Smoky Mountains National Park

NASA Astrophysics Data System (ADS)

Bernardes, S.; Madden, M.

2016-06-01

The tornado outbreak of April 2011 in the Southeastern United States caused major damage to property and natural ecosystems. During the outbreak, the Great Smoky Mountains National Park (GRSM) was hit by an EF4 tornado, resulting in a long strip of broken branches and toppled old-growth forest trees. Little is known of the consequences of extreme windthrow events, partly due to limitations in characterizing and monitoring wind-driven vegetation disturbance and recovery over large areas and over time. This work analyzed vegetation damage in the GRSM resulting from the 2011 tornado outbreak and monitored vegetation recovery in the region over a four-year period. Anomalies of the Enhanced Vegetation Index (EVI) calculated using Landsat scenes showed that the 2011 tornado affected 21.38 km2 of forest, including submesic to mesic oak/hardwoods, Southern Appalachian cove hardwood forests and montane alluvial forests. Tornado damage severity was mapped and investigated by using anomalies of EVI over space and time and showed track discontinuity and significant variation in damage intensity along the tornado track, suggesting vortex-topography interactions. Temporal profiles and spatial representations of EVI anomalies for the period 2011-2015 indicated that EVI in 2015 was above pre-event values, indicating homogeneous canopy and lack of vertical structure during regrowth.

Play behavior of the golden-headed lion tamarin in Brazilian cocoa agroforests.

PubMed

Monteiro de Almeida Rocha, Juliana; Pedreira Dos Reis, Paula; de Carvalho Oliveira, Leonardo

2014-01-01

During play, primates may become more vulnerable to predation. Our goal was to examine the potential role of predation risk on the play behavior of 3 groups of golden-headed lion tamarin, Leontopithecus chrysomelas, in shaded cocoa agroforest (cabruca) of Southern Bahia, Brazil. We identified the preferred (and safer) locations on vertical strata during playtime and investigated if frequency and duration of play differed according to group size. All groups preferred to play on the lower levels of vertical strata, which may be perceived as either a safer environment or as a more suitable location for play due to the vegetation structure. The smallest group played less than the others, while the largest group played more and for longer periods. Our data suggest that predation risk can influence where play takes place as well as its frequency and length.

Evaluating the role of green infrastructures on near-road pollutant dispersion and removal: Modelling and measurement.

PubMed

Morakinyo, Tobi Eniolu; Lam, Yun Fat; Hao, Song

2016-11-01

To enhance the quality of human life in a rapidly urbanized world plagued with high transportation, the masterful contribution of improved urban and local air quality cannot be overemphasized. In order to reduce human exposure to near-road air pollution, several approaches including the installation of roadside structural barriers especially in open street areas, such as city entrances are being applied. In the present study, the air quality around real world and idealized green infrastructures was investigated by means of numerical simulation and a short field measurement campaign. Fair agreement was found between ENVI-met modelled and measured particulate matter's concentration data around a realistic vegetation barrier indicating a fair representation of reality in the model. Several numerical experiments were conducted to investigate the influence of barrier type (vegetation/hedge and green wall) and dimensions on near-road air quality. The results show different horizontal/vertical patterns and magnitudes of upwind and downwind relative concentration (with and without a barrier) depending on wind condition, barrier type and dimension. Furthermore, an integrated dispersion-deposition approach was employed to assess the impact on air quality of near-road vegetation barrier. At last, recommendations to city and urban planners on the implementation of roadside structural barriers were made. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of canopy architectural variation on transpiration and thermoregulation

NASA Astrophysics Data System (ADS)

Linn, R.; Banerjee, T.

2017-12-01

One of the major scientific questions identified by the NGEE - Tropics campaign is the effect of disturbances such as forest fires, vegetation thinning and land use change on carbon, water and energy fluxes. Answers to such questions can help develop effective forest management strategies and shape policies to mitigate damages under natural and anthropogenic climate change. The absence of horizontal and vertical variation of forest canopy structure in current models is a major source of uncertainty in answering these questions. The current work addresses this issue through a bottom up process based modeling approach to systematically investigate the effect of forest canopy architectural variation on plant physiological response as well as canopy level fluxes. A plant biophysics formulation is used which is based on the following principles: (1) a model for the biochemical demand for CO2 as prescribed by photosynthesis models. This model can differentiate between photosynthesis under light-limited and nutrient-limited scenarios. (2) A Fickian mass transfer model including transfer through the laminar boundary layer on leaves that may be subjected to forced or free convection depending upon the mean velocity and the radiation load; (3) an optimal leaf water use strategy that maximizes net carbon gain for a given transpiration rate to describe the stomatal aperture variation; (4) a leaf-level energy balance to accommodate evaporative cooling. Such leaf level processes are coupled to solutions of atmospheric flow through vegetation canopies. In the first test case, different scenarios of top heavy and bottom heavy (vertical) foliage distributions are investigated within a one-dimensional framework where no horizontal heterogeneity of canopy structure is considered. In another test case, different spatial distributions (both horizontal and vertical) of canopy geometry (land use) are considered, where flow solutions using large eddy simulations (LES) are coupled to the aforementioned leaf level physiological model. The systematic differences observed across these simulated scenarios provide a clear insight of disturbance effects of forest-atmosphere interaction.

The Effect of Vegetation on Soil Water Infiltration and Retention Capacity by Improving Soil Physiochemical Property in Semi-arid Grassland

NASA Astrophysics Data System (ADS)

A, Y.; Wang, G.

2017-12-01

Water shortage is the main limiting factor for semi-arid grassland development. However, the grassland are gradually degraded represented by species conversion, biomass decrease and ecosystem structure simplification under the influence of human activity. Soil water characteristics such as moisture, infiltration and conductivity are critical variables affecting the interactions between soil parameters and vegetation. In this study, Cover, Height, Shannon-Wiener diversity index, Pielou evenness index and Richness index are served as indexes of vegetation productivity and community structure. And saturated hydraulic conductivity (Ks) and soil moisture content are served as indexes of soil water characters. The interaction between vegetation and soil water is investigated through other soil parameters, such as soil organic matter content at different vertical depths and in different degradation area (e.g., initial, transition and degraded plots). The results show that Ks significantly controlled by soil texture other than soil organic matter content. So the influence of vegetation on Ks through increasing soil organic content (SOM) might be slight. However, soil moisture content (SMC) appeared significantly positive relationship with SOM and silt content and negative relationship with sand content at all depth, significantly. This indicated that capacity of soil water storage was influenced both by soil texture and organic matter. In addition, the highest correlation coefficient of SMC was with SOM at the sub-surficial soil layer (20 40 cm). At the depth of 20 40 cm, the soil water content was relatively steady which slightly influenced by precipitation and evaporation. But it significantly influenced by soil organic matter content which related to vegetation. The correlation coefficient between SOM and SMC at topsoil layer (0 20 cm) was lowest (R2=0.36, p<0.01), which indicated the influence of vegetation on soil water content not only by soil organic matter content but also the other influential factors, such as the root water uptake, precipitation and evaporation.

Synergy of agroforestry and bottomland hardwood afforestation

USGS Publications Warehouse

Twedt, D.J.; Portwood, J.; Clason, Terry R.

2003-01-01

Afforestation of bottomland hardwood forests has historically emphasized planting heavy-seeded tree species such as oak (Quercus spp.) and pecan (Caryaillinoensis) with little or no silvicultural management during stand development. Slow growth of these tree species, herbivory, competing vegetation, and limited seed dispersal, often result in restored sites that are slow to develop vertical vegetation structure and have limited tree diversity. Where soils and hydrology permit, agroforestry can provide transitional management that mitigates these historical limitations on converting cropland to forests. Planting short-rotation woody crops and intercropping using wide alleyways are two agroforestry practices that are well suited for transitional management. Weed control associated with agroforestry systems benefits planted trees by reducing competition. The resultant decrease in herbaceous cover suppresses small mammal populations and associated herbivory of trees and seeds. As a result, rapid vertical growth is possible that can 'train' under-planted, slower-growing, species and provide favorable environmental conditions for naturally invading trees. Finally, annual cropping of alleyways or rotational pulpwood harvest of woody crops provides income more rapidly than reliance on future revenue from traditional silviculture. Because of increased forest diversity, enhanced growth and development, and improved economic returns, we believe that using agroforestry as a transitional management strategy during afforestation provides greater benefits to landowners and to the environment than does traditional bottomland hardwood afforestation.

Investigation of the scaling characteristics of LANDSAT temperature and vegetation data: a wavelet-based approach

NASA Astrophysics Data System (ADS)

Rathinasamy, Maheswaran; Bindhu, V. M.; Adamowski, Jan; Narasimhan, Balaji; Khosa, Rakesh

2017-10-01

An investigation of the scaling characteristics of vegetation and temperature data derived from LANDSAT data was undertaken for a heterogeneous area in Tamil Nadu, India. A wavelet-based multiresolution technique decomposed the data into large-scale mean vegetation and temperature fields and fluctuations in horizontal, diagonal, and vertical directions at hierarchical spatial resolutions. In this approach, the wavelet coefficients were used to investigate whether the normalized difference vegetation index (NDVI) and land surface temperature (LST) fields exhibited self-similar scaling behaviour. In this study, l-moments were used instead of conventional simple moments to understand scaling behaviour. Using the first six moments of the wavelet coefficients through five levels of dyadic decomposition, the NDVI data were shown to be statistically self-similar, with a slope of approximately -0.45 in each of the horizontal, vertical, and diagonal directions of the image, over scales ranging from 30 to 960 m. The temperature data were also shown to exhibit self-similarity with slopes ranging from -0.25 in the diagonal direction to -0.20 in the vertical direction over the same scales. These findings can help develop appropriate up- and down-scaling schemes of remotely sensed NDVI and LST data for various hydrologic and environmental modelling applications. A sensitivity analysis was also undertaken to understand the effect of mother wavelets on the scaling characteristics of LST and NDVI images.

Canopy Height and Vertical Structure from Multibaseline Polarimetric InSAR: First Results of the 2016 NASA/ESA AfriSAR Campaign

NASA Astrophysics Data System (ADS)

Lavalle, M.; Hensley, S.; Lou, Y.; Saatchi, S. S.; Pinto, N.; Simard, M.; Fatoyinbo, T. E.; Duncanson, L.; Dubayah, R.; Hofton, M. A.; Blair, J. B.; Armston, J.

2016-12-01

In this paper we explore the derivation of canopy height and vertical structure from polarimetric-interferometric SAR (PolInSAR) data collected during the 2016 AfriSAR campaign in Gabon. AfriSAR is a joint effort between NASA and ESA to acquire multi-baseline L- and P-band radar data, lidar data and field data over tropical forests and savannah sites to support calibration, validation and algorithm development in preparation for the NISAR, GEDI and BIOMASS missions. Here we focus on the L-band UAVSAR dataset acquired over the Lope National Park in Central Gabon to demonstrate mapping of canopy height and vertical structure using PolInSAR and tomographic techniques. The Lope site features a natural gradient of forest biomass from the forest-savanna boundary (< 100 Mg/ha) to dense undisturbed humid tropical forests (> 400 Mg/ha). Our dataset includes 9 long-baseline, full-polarimetric UAVSAR acquisitions along with field and lidar data from the Laser Vegetation Ice Sensor (LVIS). We first present a brief theoretical background of the PolInSAR and tomographic techniques. We then show the results of our PolInSAR algorithms to create maps of canopy height generated via inversion of the random-volume-over-ground (RVOG) and random-motion-over-ground (RVoG) models. In our approach multiple interferometric baselines are merged incoherently to maximize the interferometric sensitivity over a broad range of tree heights. Finally we show how traditional tomographic algorithms are used for the retrieval of the full vertical canopy profile. We compare our results from the different PolInSAR/tomographic algorithms to validation data derived from lidar and field data.

Vertical patterns and controls of soil nutrients in alpine grassland: Implications for nutrient uptake.

PubMed

Tian, Liming; Zhao, Lin; Wu, Xiaodong; Fang, Hongbing; Zhao, Yonghua; Yue, Guangyang; Liu, Guimin; Chen, Hao

2017-12-31

Vertical patterns and determinants of soil nutrients are critical to understand nutrient cycling in high-altitude ecosystems; however, they remain poorly understood in the alpine grassland due to lack of systematic field observations. In this study, we examined vertical distributions of soil nutrients and their influencing factors within the upper 1m of soil, using data of 68 soil profiles surveyed in the alpine grassland of the eastern Qinghai-Tibet Plateau. Soil organic carbon (SOC) and total nitrogen (TN) stocks decreased with depth in both alpine meadow (AM) and alpine steppe (AS), but remain constant along the soil profile in alpine swamp meadow (ASM). Total phosphorus, Ca 2+ , and Mg 2+ stocks slightly increased with depth in ASM. K + stock decreased with depth, while Na + stock increased slightly with depth among different vegetation types; however, SO 4 2- and Cl - stocks remained relatively uniform throughout different depth intervals in the alpine grassland. Except for SOC and TN, soil nutrient stocks in the top 20cm soils were significantly lower in ASM compared to those in AM and AS. Correlation analyses showed that SOC and TN stocks in the alpine grassland positively correlated with vegetation coverage, soil moisture, clay content, and silt content, while they negatively related to sand content and soil pH. However, base cation stocks revealed contrary relationships with those environmental variables compared to SOC and TN stocks. These correlations varied between vegetation types. In addition, no significant relationship was detected between topographic factors and soil nutrients. Our findings suggest that plant cycling and soil moisture primarily control vertical distributions of soil nutrients (e.g. K) in the alpine grassland and highlight that vegetation types in high-altitude permafrost regions significantly affect soil nutrients. Copyright © 2017 Elsevier B.V. All rights reserved.

Complex of solonetzes and vertic chestnut soils in the manych-gudilo depression

NASA Astrophysics Data System (ADS)

Kovda, I. V.; Morgun, E. P.; Il'ina, L. P.

2013-01-01

Morphological, physicochemical, and isotopic properties of a two-member soil complex developed under dry steppe have been studied in the central part of the Manych Depression. The soils are formed on chocolate-colored clayey sediments, and have pronounced microrelief and the complex vegetation pattern. A specific feature of the studied soil complex is the inverse position of its components: vertic chestnut soil occupies the microhigh, while solonetz is in the microlow. The formation of such complexes is explained by the biological factor, i.e., by the destruction of the solonetzic horizon under the impact of vegetation and earth-burrowing animals with further transformation under steppe plants and dealkalinization of the soil in the microhighs. The manifestation of vertic features and shrink-swell process in soils of the complex developing in dry steppe are compared with those in the vertic soils of the Central Pre-Caucasus formed under more humid environment. It is supposed that slickensides in the investigated vertic chestnut soil are relict feature inherited from the former wetter stage of the soil development and are subjected to a gradual degradation at present. In the modern period, vertic processes are weak and cannot be distinctly diagnosed. However, their activation may take place upon an increase of precipitation or the rise in the groundwater level.

Estimation of in-canopy flux distributions of reactive nitrogen and sulfur within a mixed hardwood forest in southern Appalachia

EPA Science Inventory

Estimating the source/sink distribution and vertical fluxes of air pollutants within and above forested canopies is critical for understanding biological, physical, and chemical processes influencing the soil-vegetation-atmosphere exchange. The vertical source-sink profiles of re...

Total vertical sediment flux and PM10 emissions from disturbed Chihuahuan Desert Surfaces

USDA-ARS?s Scientific Manuscript database

Desert surfaces are typically stable and represent some of the oldest landforms on Earth. For surfaces without vegetation, the evolution of a desert pavements of gravel protects the surface from erosive forces and vegetation further protects the surface in arid and semi-arid rangelands. The suscep...

Forest Biomass Mapping from Prism Triplet, Palsar and Landsat Data

NASA Astrophysics Data System (ADS)

Ranson, J.; Sun, G.; Ni, W.

2014-12-01

The loss of sensitivity at higher biomass levels is a common problem in biomass mapping using optical multi-spectral data or radar backscattering data due to the lack of information on canopy vertical structure. Studies have shown that adding implicit information of forest vertical structure improves the performance of forest biomass mapping from optical reflectance and radar backscattering data. LiDAR, InSAR and stereo imager are the data sources for obtaining forest structural information. The potential of providing information on forest vertical structure by stereoscopic imagery data has drawn attention recently due to the availability of high-resolution digital stereo imaging from space and the advances of digital stereo image processing software. The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) onboard the Advanced Land Observation Satellite (ALOS) has acquired multiple global coverage from June 2006 to April 2011 providing a good data source for regional/global forest studies. In this study, five PRISM triplets acquired on June 14, 2008, August 19 and September 5, 2009; PALSAR dual-pol images acquired on July 12, 2008 and August 30, 2009; and LANDSAT 5 TM images acquired on September 5, 2009 and the field plot data collected in 2009 and 2010 were used to map forest biomass at 50m pixel in an area of about 4000 km2in Maine, USA ( 45.2 deg N 68.6 deg W). PRISM triplets were used to generate point cloud data at 2m pixel first and then the average height of points above NED (National Elevation Dataset) within a 50m by 50m pixel was calculated. Five images were mosaicked and used as canopy height information in the biomass estimation along with the PALSAR HH, HV radar backscattering and optical reflectance vegetation indices from L-5 TM data. A small portion of this region was covered by the Land Vegetation and Ice Sensor (LVIS) in 2009. The biomass maps from the LVIS data was used to evaluate the results from combined use of PRISM, PALSAR and LANDSAT data. The results show that the canopy height index from PRISM stereo images significantly improves the biomass mapping accuracy and extends the saturation level of biomass, and results in a biomass map comparable with those generated from LVIS data.

Livestock grazing supports native plants and songbirds in a California annual grassland.

PubMed

Gennet, Sasha; Spotswood, Erica; Hammond, Michele; Bartolome, James W

2017-01-01

Over eight years we measured the effects of plant community composition, vegetation structure, and livestock grazing on occurrence of three grassland bird species-Western Meadowlark (Sturnella neglecta), Horned Lark (Eremophila alpestris), and Grasshopper Sparrow (Ammodramus savannarum)-at sites in central California during breeding season. In California's Mediterranean-type climatic region, coastal and inland grassland vegetation is dominated by exotic annual grasses with occasional patches of native bunchgrass and forbs. Livestock grazing, primarily with beef cattle, is the most widely used management tool. Compared with ungrazed plots, grazed plots had higher bare ground, native plant cover, and vertically heterogeneous vegetation. Grazed plots also had less plant litter and shorter vegetation. Higher native plant cover, which is predominantly composed of bunchgrasses in our study area, was associated with livestock grazing and north-facing aspects. Using an information theoretic approach, we found that all three bird species had positive associations with native plant abundance and neutral (Western Meadowlark, Grasshopper Sparrow) or positive (Horned Lark) association with livestock grazing. All species favored flatter areas. Horned Larks and Western Meadowlark occurred more often where there were patches of bare ground. Western Meadowlarks and Grasshopper Sparrows were most common on north-facing slopes, suggesting that these species may be at risk from projected climate change. These findings demonstrate that livestock grazing is compatible with or supports grassland bird conservation in Mediterranean-type grasslands, including areas with high levels of exotic annual grass invasion, in part because grazing supports the persistence of native plants and heterogeneity in vegetation structure. However, conservation of low-lying grasslands with high native species presence, and active management to increase the abundance of native plant species are also likely to be important for sustaining grassland birds long-term.

Linking vegetation structure, function and physiology through spectroscopic remote sensing

NASA Astrophysics Data System (ADS)

Serbin, S.; Singh, A.; Couture, J. J.; Shiklomanov, A. N.; Rogers, A.; Desai, A. R.; Kruger, E. L.; Townsend, P. A.

2015-12-01

Terrestrial ecosystem process models require detailed information on ecosystem states and canopy properties to properly simulate the fluxes of carbon (C), water and energy from the land to the atmosphere and assess the vulnerability of ecosystems to perturbations. Current models fail to adequately capture the magnitude, spatial variation, and seasonality of terrestrial C uptake and storage, leading to significant uncertainties in the size and fate of the terrestrial C sink. By and large, these parameter and process uncertainties arise from inadequate spatial and temporal representation of plant traits, vegetation structure, and functioning. With increases in computational power and changes to model architecture and approaches, it is now possible for models to leverage detailed, data rich and spatially explicit descriptions of ecosystems to inform parameter distributions and trait tradeoffs. In this regard, spectroscopy and imaging spectroscopy data have been shown to be invaluable observational datasets to capture broad-scale spatial and, eventually, temporal dynamics in important vegetation properties. We illustrate the linkage of plant traits and spectral observations to supply key data constraints for model parameterization. These constraints can come either in the form of the raw spectroscopic data (reflectance, absorbtance) or physiological traits derived from spectroscopy. In this presentation we highlight our ongoing work to build ecological scaling relationships between critical vegetation characteristics and optical properties across diverse and complex canopies, including temperate broadleaf and conifer forests, Mediterranean vegetation, Arctic systems, and agriculture. We focus on work at the leaf, stand, and landscape scales, illustrating the importance of capturing the underlying variability in a range of parameters (including vertical variation within canopies) to enable more efficient scaling of traits related to functional diversity of ecosystems.

Tropical forest heterogeneity from TanDEM-X InSAR and lidar observations in Indonesia

NASA Astrophysics Data System (ADS)

De Grandi, Elsa Carla; Mitchard, Edward

2016-10-01

Fires exacerbated during El Niño Southern Oscillation are a serious threat in Indonesia leading to the destruction and degradation of tropical forests and emissions of CO2 in the atmosphere. Forest structural changes which occurred due to the 1997-1998 El Niño Southern Oscillation in the Sungai Wain Protection Forest (East Kalimantan, Indonesia), a previously intact forest reserve have led to the development of a range of landcover from secondary forest to areas dominated by grassland. These structural differences can be appreciated over large areas by remote sensing instruments such as TanDEM-X and LiDAR that provide information that are sensitive to vegetation vertical and horizontal structure. One-point statistics of TanDEM-X coherence (mean and CV) and LiDAR CHM (mean, CV) and derived metrics such as vegetation volume and canopy cover were tested for the discrimination between 4 landcover classes. Jeffries-Matusita (JM) separability was high between forest classes (primary or secondary forest) and non-forest (grassland) while, primary and secondary forest were not separable. The study tests the potential and the importance of potential of TanDEM-X coherence and LiDAR observations to characterize structural heterogeneity based on one-point statistics in tropical forest but requires improved characterization using two-point statistical measures.

[Position of Betula ermanii population ecotone in Changbai Mountains].

PubMed

Zou, Chunjing; Wang, Xiaochun; Han, Shijie

2004-12-01

The vegetation on the northern slope of Changbai Mountains forms a vertical zone due to the vertical differentiation of moisture and heat conditions. Ecotones are obviously existed between different vegetation zones, but it is difficult to decide their positions. In the area from 1400 m to 2200 m elevation, we adopted the methods of gradient sampling, fractal analysis, population pattern analysis, and interspecific competition index analysis to describe Betula ermanii population ecotone. The results showed that there was a forest ecotone between Betula ermanii and Picea-Abies forest near elevation 1650 m, and there was a forest line ecotone between Betula ermanii and alpine tundra near elevation 2080 m.

Polarimetric and Structural Properties of a Boreal Forest at P-Band and L-Band

NASA Astrophysics Data System (ADS)

Tebaldini, S.; Rocca, F.

2010-12-01

With this paper we investigate the structural and polarimetric of the boreal forest within the Krycklan river catchment, Northern Sweden, basing on multi-polarimetric and multi-baseline SAR surveys at P-Band and L-Band collected in the framework of the ESA campaign BioSAR 2008. The analysis has been carried out by applying the Algebraic Synthesis (AS) technique, recently introduced in literature, which provides a theoretical framework for the decomposition of the backscattered signal into ground-only and volume-only contributions, basing on both baseline and polarization diversity. The availability of multiple baselines allows the formation of a synthetic aperture not only along the azimuth direction but also in elevation. Accordingly, the backscattered echoes can be focused not only in the slant range, azimuth plane, but in the whole 3D space. This is the rationale of the SAR Tomography (T-SAR) concept, which has been widely considered in the literature of the last years. It follows that, as long as the penetration in the scattering volume is guaranteed, the vertical profile of the vegetation layer is retrieved by separating backscatter contributions along the vertical direction, which is the main reason for the exploitation of Tomographic techniques at longer wavelengths. Still, the capabilities of T-SAR are limited to imaging the global vertical structure of the electromagnetic scattering in a certain polarization. It then becomes important to develop methodologies for the investigation of the vertical structure of different Scattering Mechanisms (SMs), such as ground and volume scattering, in such a way as to derive information that can be delivered also outside the field of Radar processing. This is an issue that may become relevant at longer wavelengths, such as P-Band, where the presence of multiple scattering arising from the interaction with terrain could hinder the correct reconstruction of the forest structure. The availability of multiple polarizations allows to overcome this limitation, thus providing a way to obtain the vertical structures associated with volume-only contributions. Experimental results will be provided showing the following. At P-Band the most relevant scattering contributions are observed at the ground level, not only in the co-polar channels, but also in HV, consistently with he first BioSAR campaign. L-Band data have shown a remarkable difference, resulting in a more uniform distribution of the backscattered power along the vertical direction. Volume top height has been observed to be substantially invariant to the choice of the solution for volume-only scattering. These results underline the validity of modeling a forest scenario as being constituted by volume and ground (or rather ground-locked) scattering, and the importance of forest top height as the most robust indicator of the forest structure as imaged through microwaves measurements. Nevertheless, it has also been shown that different solutions for volume scattering correspond to dramatically different vertical structures. In this framework, tomography represents a powerful tool for investigating the potential solutions, as it allows to see what kind of vertical structure has been retrieved. On this basis, a solution has been proposed as a criterion to emphasize volume contributions at P-Band.

Terrestrial salamander abundance on reclaimed mountaintop removal mines

USGS Publications Warehouse

Wood, Petra Bohall; Williams, Jennifer M.

2013-01-01

Mountaintop removal mining, a large-scale disturbance affecting vegetation, soil structure, and topography, converts landscapes from mature forests to extensive grassland and shrubland habitats. We sampled salamanders using drift-fence arrays and coverboard transects on and near mountaintop removal mines in southern West Virginia, USA, during 2000–2002. We compared terrestrial salamander relative abundance and species richness of un-mined, intact forest with habitats on reclaimed mountaintop removal mines (reclaimed grassland, reclaimed shrubland, and fragmented forest). Salamanders within forests increased in relative abundance with increasing distance from reclaimed mine edge. Reclaimed grassland and shrubland habitats had lower relative abundance and species richness than forests. Characteristics of reclaimed habitats that likely contributed to lower salamander abundance included poor soils (dry, compacted, little organic matter, high rock content), reduced vertical structure of vegetation and little tree cover, and low litter and woody debris cover. Past research has shown that salamander populations reduced by clearcutting may rebound in 15–24 years. Time since disturbance was 7–28 years in reclaimed habitats on our study areas and salamander populations had not reached levels found in adjacent mature forests.

Exploring the role of trees in the evolution of meander bends: The Tagliamento River, Italy

NASA Astrophysics Data System (ADS)

Zen, Simone; Gurnell, Angela M.; Zolezzi, Guido; Surian, Nicola

2017-07-01

To date, the role of riparian trees in the formation of scroll bars, ridges, and swales during the evolution of meandering channels has been inferred largely from field observations with support from air photographs. In situ field observations are usually limited to relatively short periods of time, whereas the evolution of these morphological features may take decades. By combining field observations of inner bank morphology and overlying riparian woodland structure with a detailed historical analysis of airborne LiDAR data, panchromatic, and color images, we reconstruct the spatial and temporal evolution of the morphology and vegetation across four meander bends of the Tagliamento River, Italy. Specifically we reveal (i) the appearance of deposited trees and elongated vegetated patches on the inner bank of meander bends following flood events; (ii) temporal progression from deposited trees, through small to larger elongated vegetated patches (pioneer islands), to their coalescence into long, linear vegetated features that eventually become absorbed into the continuous vegetation cover of the riparian forest; and (iii) a spatial correspondence between the resulting scrolls and ridge and swale topography, and tree cover development and persistence. We provide a conceptual model of the mechanisms by which vegetation can contribute to the formation of sequence of ridges and swales on the convex bank of meander bends. We discuss how these insights into the biomorphological processes that control meander bends advance can inform modeling activities that aim to describe the lateral and vertical accretion of the floodplain during the evolution of vegetated river meanders.

Patterns in woody vegetation structure across African savannas

NASA Astrophysics Data System (ADS)

Axelsson, Christoffer R.; Hanan, Niall P.

2017-07-01

Vegetation structure in water-limited systems is to a large degree controlled by ecohydrological processes, including mean annual precipitation (MAP) modulated by the characteristics of precipitation and geomorphology that collectively determine how rainfall is distributed vertically into soils or horizontally in the landscape. We anticipate that woody canopy cover, crown density, crown size, and the level of spatial aggregation among woody plants in the landscape will vary across environmental gradients. A high level of woody plant aggregation is most distinct in periodic vegetation patterns (PVPs), which emerge as a result of ecohydrological processes such as runoff generation and increased infiltration close to plants. Similar, albeit weaker, forces may influence the spatial distribution of woody plants elsewhere in savannas. Exploring these trends can extend our knowledge of how semi-arid vegetation structure is constrained by rainfall regime, soil type, topography, and disturbance processes such as fire. Using high-spatial-resolution imagery, a flexible classification framework, and a crown delineation method, we extracted woody vegetation properties from 876 sites spread over African savannas. At each site, we estimated woody cover, mean crown size, crown density, and the degree of aggregation among woody plants. This enabled us to elucidate the effects of rainfall regimes (MAP and seasonality), soil texture, slope, and fire frequency on woody vegetation properties. We found that previously documented increases in woody cover with rainfall is more consistently a result of increasing crown size than increasing density of woody plants. Along a gradient of mean annual precipitation from the driest (< 200 mm yr-1) to the wettest (1200-1400 mm yr-1) end, mean estimates of crown size, crown density, and woody cover increased by 233, 73, and 491 % respectively. We also found a unimodal relationship between mean crown size and sand content suggesting that maximal savanna tree sizes do not occur in either coarse sands or heavy clays. When examining the occurrence of PVPs, we found that the same factors that contribute to the formation of PVPs also correlate with higher levels of woody plant aggregation elsewhere in savannas and that rainfall seasonality plays a key role for the underlying processes.

Satellites observed widespread greening of Earth and increase of woody biomass

NASA Astrophysics Data System (ADS)

Chen, C.; Park, T.; Myneni, R.; Xu, L.; Saatchi, S. S.; Liu, Y.; Knyazikhin, Y.

2017-12-01

Global terrestrial vegetation is an important modulator of the planetary climate system that alters Earth's hydrology, atmosphere and energy circulations through biophysical and biochemical processes. Yet the internal structural change of the vegetation is not well understood. Leaf area index (LAI), unlike radiometric parameters (e.g. NDVI), is a well-defined and ground-measurable biophysical variable, which can better represent the greenness of vegetation. We evaluate 17-year (2000-2016) satellite-derived LAI from two MODIS sensors onboard Terra and Aqua. Results show that the global annual-averaged LAI has an increasing trend at 0.036 m2m-2 per decade (2.3% per decade). The widespread greening takes up 32.5% of the vegetated area, while only 5.2% of such exhibits browning. We further investigate the biome- and regional-specific patterns of the evolution of LAI: 1) Croplands (0.062 m2m-2 per decade) and forests (0.044 m2m-2 per decade) are the paramount contributors of the greening; 2) Temperate vegetation (0.052 m2m-2 per decade) greening outperform other regions, followed by high-latitude vegetation (0.031 m2m-2 per decade), and tropical vegetation (0.025 m2m-2 per decade) at the minimum. Two independent satellite-observed datasets from multiple bandwidths (optical, thermal and microwave) provide evidence that this large-scale LAI trend is mainly owing to the spatiotemporal transition of woody biomass and the change of canopy structure. The greening (browning) at the global scale is concordant with the increase (decrease) of tree cover and vegetation optical depth (VOD), while little correlation is found for herbaceous biomass (i.e. non-tree cover). The observed greening and expansion of woody biomass will lead to a smaller land surface diurnal temperature range (DTR) due to the increase of a) the evapotranspiration, b) the water storage (higher the specific heat capacity) and c) the aerodynamic resistance (vertical mixture) of the canopy. a) and c) can augment daytime cooling, while b) and c) can boost nighttime warming. We find, consistently, the MODIS observed land surface DTR decreases over greening regions, and increases over browning regions.

Integration of remote sensing and geophysical techniques for coastal monitoring

NASA Astrophysics Data System (ADS)

Simoniello, T.; Carone, M. T.; Loperte, A.; Satriani, A.; Imbrenda, V.; D'Emilio, M.; Guariglia, A.

2009-04-01

Coastal areas are of great environmental, economic, social, cultural and recreational relevance; therefore, the implementation of suitable monitoring and protection actions is fundamental for their preservation and for assuring future use of this resource. Such actions have to be based on an ecosystem perspective for preserving coastal environment integrity and functioning and for planning sustainable resource management of both the marine and terrestrial components (ICZM-EU initiative). We implemented an integrated study based on remote sensing and geophysical techniques for monitoring a coastal area located along the Ionian side of Basilicata region (Southern Italy). This area, between the Bradano and Basento river mouths, is mainly characterized by a narrow shore (10-30 m) of fine sandy formations and by a pine forest planted in the first decade of 50's in order to preserve the coast and the inland cultivated areas. Due to drought and fire events and saltwater intrusion phenomena, such a forest is affected by a strong decline with consequent environmental problems. Multispectral satellite data were adopted for evaluating the spatio-temporal features of coastal vegetation and the structure of forested patterns. The increase or decrease in vegetation activity was analyzed from trends estimated on a time series of NDVI (Normalized Difference Vegetation Index) maps. The fragmentation/connection levels of vegetated patterns was assessed form a set of landscape ecology metrics elaborated at different structure scales (patch, class and landscape) on satellite cover classifications. Information on shoreline changes were derived form a multi-source data set (satellite data, field-GPS surveys and Aerial Laser Scanner acquisitions) by taking also into account tidal effects. Geophysical campaigns were performed for characterizing soil features and limits of salty water infiltrations. Form vertical resistivity soundings (VES), soil resistivity maps at different a deeps (0.5-1.0-1.5m) were obtained; in addition electrical resistivity tomographies (ERT) were acquired with different orientations and lengths. The analysis of vegetation activity from satellite data identified large patches affected by vegetation decline and fragmentation processes, where geophysical measurements highlighted a salt water infiltration. Moreover, they showed that such a phenomenon has not only a horizontal distribution, but also a vertical diffusion interesting the layer active for plant roots. Since a severe shoreline regression (up to 90m) was observed along the investigated coast, erosional process could have increased the saltwater intrusion process during the last 20 years. On the whole, the obtained results suggest that the integration of remote sensing peculiarities (synoptic view, multi-temporal availability) with those of geophysical techniques (local details, non-invasive soundings) can be a suitable support tool for planning and management activities in coastal areas (e.g., the identification of the most appropriated sites for ecological interventions or for barrage and earthen block construction).

Bed site selection by neonate deer in grassland habitats on the northern Great Plains

USGS Publications Warehouse

Grovenburg, T.W.; Jacques, C.N.; Klaver, R.W.; Jenks, J.A.

2010-01-01

Bed site selection is an important behavioral trait influencing neonate survival. Vegetation characteristics of bed sites influence thermal protection of neonates and concealment from predators. Although previous studies describe bed site selection of neonatal white-tailed deer (Odocoileus virginianus) in regions of forested cover, none determined microhabitat effects on neonate bed site selection in the Northern Great Plains, an area of limited forest cover. During summers 2007–2009, we investigated bed site selection (n  =  152) by 81 radiocollared neonate white-tailed deer in north-central South Dakota, USA. We documented 80 (52.6%) bed sites in tallgrass–Conservation Reserve Program lands, 35 (23.0%) bed sites in forested cover, and 37 (24.3%) in other habitats (e.g., pasture, alfalfa, wheat). Bed site selection varied with age and sex of neonate. Tree canopy cover (P < 0.001) and tree basal area (P < 0.001) decreased with age of neonates, with no bed sites observed in forested cover after 18 days of age. Male neonates selected sites with less grass cover (P < 0.001), vertical height of understory vegetation (P < 0.001), and density of understory vegetation (P < 0.001) but greater bare ground (P  =  0.047), litter (P  =  0.028), and wheat (P  =  0.044) than did females. Odds of bed site selection increased 3.5% (odds ratio  =  1.035, 95% CI  =  1.008–1.062) for every 1-cm increase in vertical height of understory vegetation. Management for habitat throughout the grasslands of South Dakota that maximizes vertical height of understory vegetation would enhance cover characteristics selected by neonates.

Vertical distribution and retention mechanism of nitrogen and phosphorus in soils with different macrophytes of a natural river mouth wetland.

PubMed

Huang, Wei; Chen, Qiuwen; Ren, Kuixiao; Chen, Kaining

2015-03-01

Wetland vegetation can improve water quality through several processes including direct assimilation and the indirect effects of sedimentation and mineralization. This research takes the Zhucao River mouth of Daxi reservoir as a study case to investigate the vertical distribution of nitrogen and phosphorus in the soil of a natural wetland covered by different plants prior to any restoration action. There are four native emergent macrophytes (Typha latifolia L., Polygonum hydropiper L., Juncus effuses L., Phragmites communis L.) in the wetland. The total nitrogen (TN) and nitrate contents decreased with the soil depth for all vegetation types, and the mean TN and nitrate concentrations were higher in vegetative soil than in bare ground. The maximum TN concentration was found in the surface soil (0-2 cm) covered by P. communis. Ammonium decreased with the soil depth in vegetative areas, while it increased with soil depth in bare ground. The rank order of P fractions was organic P (OP) > P associated with Ca (Ca-P) > P associated with Fe/Al (Fe/Al-P). Total phosphorus (TP) and OP showed vertical profiles similar to that of TN. The mean concentrations of TP, Ca-P and Fe/Al-P were higher in vegetative soil than in bare ground. The maximum mean TP was also found in soil covered by P. communis. Loss on ignition (LOI) was significantly correlated with TN and TP (P < 0.05). Organic matter accumulation may be the main pathway to retain nitrogen and phosphorus in the wetland. Nitrogen and phosphorus sequestration in P. communis soil was the highest of the four dominant plants. The results could support the restoration of other degraded river mouth wetlands of the reservoir.

Balancing Aggradation and Progradation on a Vegetated Delta: The Importance of Fluctuating Discharge in Depositional Systems

NASA Astrophysics Data System (ADS)

Piliouras, Anastasia; Kim, Wonsuck; Carlson, Brandee

2017-10-01

Vegetation is an important component of constructional landscapes, as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss. We conducted two sets of laboratory experiments using alfalfa (Medicago sativa) to determine the effects of plants on channel organization and large-scale delta dynamics. In the first set, we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport. A second set of experiments used discharge fluctuations between flood and base flow (or interflood). Interfloods were critical for reworking the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization. These low-flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline. Floods decreased relief by filling channels with sediment, resulting in periods of rapid progradation and enhanced aggradation over the topset surface, which was amplified by vegetation. The combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation. We conclude that plants can inhibit channelization in depositional systems and that discharge fluctuations encourage channel network organization to naturally balance against aggradation. Thus, variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems, and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth.

Response of bird species densities to habitat structure and fire history along a Midwestern open-forest gradient

USGS Publications Warehouse

Grundel, R.; Pavlovic, N.B.

2007-01-01

Oak savannas were historically common but are currently rare in the Midwestern United States. We assessed possible associations of bird species with savannas and other threatened habitats in the region by relating fire frequency and vegetation characteristics to seasonal densities of 72 bird species distributed across an open-forest gradient in northwestern Indiana. About one-third of the species did not exhibit statistically significant relationships with any combination of seven vegetation characteristics that included vegetation cover in five vertical strata, dead tree density, and tree height. For 40% of the remaining species, models best predicting species density incorporated tree density. Therefore, management based solely on manipulating tree density may not be an adequate strategy for managing bird populations along this open-forest gradient. Few species exhibited sharp peaks in predicted density under habitat conditions expected in restored savannas, suggesting that few savanna specialists occur among Midwestern bird species. When fire frequency, measured over fifteen years, was added to vegetation characteristics as a predictor of species density, it was incorporated into models for about one-quarter of species, suggesting that fire may modify habitat characteristics in ways that are important for birds but not captured by the structural habitat variables measured. Among those species, similar numbers had peaks in predicted density at low, intermediate, or high fire frequency. For species suggested by previous studies to have a preference for oak savannas along the open-forest gradient, estimated density was maximized at an average fire return interval of about one fire every three years. ?? The Cooper Ornithological Society 2007.

Urban land use of the Sao Paulo metropolitan area by automatic analysis of LANDSAT data

NASA Technical Reports Server (NTRS)

Parada, N. D. J. (Principal Investigator); Niero, M.; Foresti, C.

1983-01-01

The separability of urban land use classes in the metropolitan area of Sao Paulo was studied by means of automatic analysis of MSS/LANDSAT digital data. The data were analyzed using the media K and MAXVER classification algorithms. The land use classes obtained were: CBD/vertical growth area, residential area, mixed area, industrial area, embankment area type 1, embankment area type 2, dense vegetation area and sparse vegetation area. The spectral analysis of representative samples of urban land use classes was done using the "Single Cell" analysis option. The classes CBD/vertical growth area, residential area and embankment area type 2 showed better spectral separability when compared to the other classes.

ICESat Lidar and Global Digital Elevation Models: Application to DESDynI

NASA Technical Reports Server (NTRS)

Carabajal, Claudia C.; Harding, David J.; Suchdeo, Vijay P.

2010-01-01

Geodetic control is extremely important in the production and quality control of topographic data sets, enabling elevation results to be referenced to an absolute vertical datum. Global topographic data with improved geodetic accuracy achieved using global Ground Control Point (GCP) databases enable more accurate characterization of land topography and its change related to solid Earth processes, natural hazards and climate change. The multiple-beam lidar instrument that will be part of the NASA Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) mission will provide a comprehensive, global data set that can be used for geodetic control purposes. Here we illustrate that potential using data acquired by NASA's Ice, Cloud and land Elevation Satellite (ICEsat) that has acquired single-beam, globally distributed laser altimeter profiles (+/-86deg) since February of 2003 [1, 2]. The profiles provide a consistently referenced elevation data set with unprecedented accuracy and quantified measurement errors that can be used to generate GCPs with sub-decimeter vertical accuracy and better than 10 m horizontal accuracy. Like the planned capability for DESDynI, ICESat records a waveform that is the elevation distribution of energy reflected within the laser footprint from vegetation, where present, and the ground where illuminated through gaps in any vegetation cover [3]. The waveform enables assessment of Digital Elevation Models (DEMs) with respect to the highest, centroid, and lowest elevations observed by ICESat and in some cases with respect to the ground identified beneath vegetation cover. Using the ICESat altimetry data we are developing a comprehensive database of consistent, global, geodetic ground control that will enhance the quality of a variety of regional to global DEMs. Here we illustrate the accuracy assessment of the Shuttle Radar Topography Mission (SRTM) DEM produced for Australia, documenting spatially varying elevation biases of several meters in magnitude.

Lidar Altimeter Measurements of Canopy Structure: Methods and Validation for Closed Canopy, Broadleaf Forests

NASA Technical Reports Server (NTRS)

Harding, D. J.; Lefsky, M. A.; Parker, G. G.; Blair, J. B.

1999-01-01

Lidar altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne lidar altimeter data was acquired using the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) for a successional sequence of four, closed-canopy, deciduous forest stands in eastern Maryland. The four stands were selected so as to include a range of canopy structures of importance to forest ecosystem function, including variation in the height and roughness of the outer-most canopy surface and the vertical organization of canopy stories and gaps. The character of the SLICER backscatter signal is described and a method is developed that accounts for occlusion of the laser energy by canopy surfaces, transforming the backscatter signal to a canopy height profile (CHP) that quantitatively represents the relative vertical distribution of canopy surface area. The transformation applies an increased weighting to the backscatter amplitude as a function of closure through the canopy and assumes a horizontally random distribution of the canopy components. SLICER CHPs, averaged over areas of overlap where lidar ground tracks intersect, are shown to be highly reproducible. CHP transects across the four stands reveal spatial variations in vegetation, at the scale of the individual 10 m diameter laser footprints, within and between stands. Averaged SLICER CHPs are compared to analogous height profile results derived from ground-based sightings to plant intercepts measured on plots within the four stands. Tbe plots were located on the segments of the lidar ground tracks from which averaged SLICER CHPs were derived, and the ground observations were acquired within two weeks of the SLICER data acquisition to minimize temporal change. The differences in canopy structure between the four stands is similarly described by the SLICER and ground-based CHP results, however a Chi-square test of similarity documents differences that are statistically significant. The differences are discussed in terms of measurement properties that define the smoothness of the resulting CHPs and Lidar Altimeter Measurements of Canopy Structure - Harding et al. canopy properties that may vertically bias the CHP representations of canopy structure. The statistical differences are most likely due to the more noisy character of the ground-based CHPs, especially high in the canopy where ground-based sightings are rare resulting in an underestimate of canopy surface area and height, and to departures from the assumption of horizontal randomness which bias the CHPs toward the observer (upward for SLICER and downward for ground-based CHPs). The results demonstrate that the SLICER observations reliably provide a measure of canopy structure that reveals ecologically interesting structural variations such as those characterizing a successional sequence of closed-canopy, broadleaf forest stands.

Fire Impacts on Mixed Pine-oak Forests Assessed with High Spatial Resolution Imagery, Imaging Spectroscopy, and LiDAR

NASA Astrophysics Data System (ADS)

Meng, R.; Wu, J.; Zhao, F. R.; Kathy, S. L.; Dennison, P. E.; Cook, B.; Hanavan, R. P.; Serbin, S.

2016-12-01

As a primary disturbance agent, fire significantly influences forest ecosystems, including the modification or resetting of vegetation composition and structure, which can then significantly impact landscape-scale plant function and carbon stocks. Most ecological processes associated with fire effects (e.g. tree damage, mortality, and vegetation recovery) display fine-scale, species specific responses but can also vary spatially within the boundary of the perturbation. For example, both oak and pine species are fire-adapted, but fire can still induce changes in composition, structure, and dominance in a mixed pine-oak forest, mainly because of their varying degrees of fire adaption. Evidence of post-fire shifts in dominance between oak and pine species has been documented in mixed pine-oak forests, but these processes have been poorly investigated in a spatially explicit manner. In addition, traditional field-based means of quantifying the response of partially damaged trees across space and time is logistically challenging. Here we show how combining high resolution satellite imagery (i.e. Worldview-2,WV-2) and airborne imaging spectroscopy and LiDAR (i.e. NASA Goddard's Lidar, Hyperspectral and Thermal airborne imager, G-LiHT) can be effectively used to remotely quantify spatial and temporal patterns of vegetation recovery following a top-killing fire that occurred in 2012 within mixed pine-oak forests in the Long Island Central Pine Barrens Region, New York. We explore the following questions: 1) what are the impacts of fire on species composition, dominance, plant health, and vertical structure; 2) what are the recovery trajectories of forest biomass, structure, and spectral properties for three years following the fire; and 3) to what extent can fire impacts be captured and characterized by multi-sensor remote sensing techniques from active and passive optical remote sensing.

Stereophotogrammetry in studies of riparian vegetation dynamics

NASA Astrophysics Data System (ADS)

Hortobagyi, Borbala; Vautier, Franck; Corenblit, Dov; Steiger, Johannes

2014-05-01

Riparian vegetation responds to hydrogeomorphic disturbances and also controls sediment deposition and erosion. Spatio-temporal riparian vegetation dynamics within fluvial corridors have been quantified in many studies using aerial photographs and GIS. However, this approach does not allow the consideration of woody vegetation growth rates (i.e. vertical dimension) which are fundamental when studying feedbacks between the processes of fluvial landform construction and vegetation establishment and succession. We built 3D photogrammetric models of vegetation height based on aerial argentic and digital photographs from sites of the Allier and Garonne Rivers (France). The models were realized at two different spatial scales and with two different methods. The "large" scale corresponds to the reach of the river corridor on the Allier river (photograph taken in 2009) and the "small" scale to river bars of the Allier (photographs taken in 2002, 2009) and Garonne Rivers (photographs taken in 2000, 2002, 2006 and 2010). At the corridor scale, we generated vegetation height models using an automatic procedure. This method is fast but can only be used with digital photographs. At the bar scale, we constructed the models manually using a 3D visualization on the screen. This technique showed good results for digital and also argentic photographs but is very time-consuming. A diachronic study was performed in order to investigate vegetation succession by distinguishing three different classes according to the vegetation height: herbs (<1 m), shrubs (1-4 m) or trees (>4 m). Both methods, i.e. automatic and manual, were employed to study the evolution of the three vegetation classes and the recruitment of new vegetation patches. A comparison was conducted between the vegetation height given by models (automatic and manual) and the vegetation height measured in the field. The manually produced models (small scale) were of a precision of 0.5-1 m, allowing the quantification of woody vegetation growth rates. Thus, our results show that the manual method we developed is accurate to quantify vegetation growth rates at small scales, whereas the less accurate automatic method is appropriate to study vegetation succession at the corridor scale. Both methods are complementary and will contribute to a further exploration of the mutual relationships between hydrogeomorphic processes, topography and vegetation dynamics within alluvial systems, adding the quantification of the vertical dimension of riparian vegetation to their spatio-temporal characteristics.

Balancing aggradation and progradation on a vegetated delta: The importance of fluctuating discharge in depositional systems

DOE PAGES

Piliouras, Anastasia; Kim, Wonsuck; Carlson, Brandee

2017-10-04

Vegetation is an important component of constructional landscapes, as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss. We conducted two sets of laboratory experiments using alfalfa ( Medicago sativa) to determine the effects of plants on channel organization and large-scale delta dynamics. In the first set, we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport. A second set of experiments used discharge fluctuations between flood and base flow (or interflood). Interfloods were critical for reworkingmore » the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization. These low flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline. Floods decreased relief by filling channels with sediment, resulting in periods of rapid progradation and enhanced aggradation over the topset surface, which was amplified by vegetation. The combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation. We conclude that plants can inhibit channelization in depositional systems, and that discharge fluctuations encourage channel network organization to naturally balance against aggradation. Furthermore, variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems, and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth.« less

Balancing aggradation and progradation on a vegetated delta: The importance of fluctuating discharge in depositional systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piliouras, Anastasia; Kim, Wonsuck; Carlson, Brandee

Vegetation is an important component of constructional landscapes, as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss. We conducted two sets of laboratory experiments using alfalfa ( Medicago sativa) to determine the effects of plants on channel organization and large-scale delta dynamics. In the first set, we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport. A second set of experiments used discharge fluctuations between flood and base flow (or interflood). Interfloods were critical for reworkingmore » the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization. These low flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline. Floods decreased relief by filling channels with sediment, resulting in periods of rapid progradation and enhanced aggradation over the topset surface, which was amplified by vegetation. The combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation. We conclude that plants can inhibit channelization in depositional systems, and that discharge fluctuations encourage channel network organization to naturally balance against aggradation. Furthermore, variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems, and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth.« less

Spaceborne Potential for Examining Taiga-Tundra Ecotone Form and Vulnerability

NASA Technical Reports Server (NTRS)

Montesano, Paul M.; Sun, Guoqing; Dubayah, Ralph O.; Ranson, K. Jon

2016-01-01

In the taiga-tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, variable and widespread vegetation change warrants the application of spaceborne data including high-resolution (less than 5m) spaceborne imagery (HRSI) across broad scales for examining TTE form and predicting dynamics. This study analyzes forest structure at the patch-scale in the TTE to provide a means to examine both vertical and horizontal components of ecotone form. We demonstrate the potential of spaceborne data for integrating forest height and density to assess TTE form at the scale of forest patches across the circumpolar biome by (1) mapping forest patches in study sites along the TTE in northern Siberia with a multi-resolution suite of spaceborne data, and (2) examining the uncertainty of forest patch height from this suite of data across sites of primarily diffuse TTE forms. Results demonstrate the opportunities for improving patch-scale spaceborne estimates of forest height, the vertical component of TTE form, with HRSI. The distribution of relative maximum height uncertainty based on prediction intervals is centered at approximately 40%, constraining the use of height for discerning differences in forest patches. We discuss this uncertainty in light of a conceptual model of general ecotone forms, and highlight how the uncertainty of spaceborne estimates of height can contribute to the uncertainty in identifying TTE forms. A focus on reducing the uncertainty of height estimates in forest patches may improve depiction of TTE form, which may help explain variable forest responses in the TTE to climate change and the vulnerability of portions of the TTE to forest structure change. structural changes.

Effect of water table fluctuations on phreatophytic root distribution.

PubMed

Tron, Stefania; Laio, Francesco; Ridolfi, Luca

2014-11-07

The vertical root distribution of riparian vegetation plays a relevant role in soil water balance, in the partition of water fluxes into evaporation and transpiration, in the biogeochemistry of hyporheic corridors, in river morphodynamics evolution, and in bioengineering applications. The aim of this work is to assess the effect of the stochastic variability of the river level on the root distribution of phreatophytic plants. A function describing the vertical root profile has been analytically obtained by coupling a white shot noise representation of the river level variability to a description of the dynamics of root growth and decay. The root profile depends on easily determined parameters, linked to stream dynamics, vegetation and soil characteristics. The riparian vegetation of a river characterized by a high variability turns out to have a rooting system spread over larger depths, but with shallower mean root depths. In contrast, a lower river variability determines root profiles with higher mean root depths. Copyright © 2014 Elsevier Ltd. All rights reserved.

The influence of atmospheric particles on the elemental content of vegetables in urban gardens of Sao Paulo, Brazil.

PubMed

Amato-Lourenco, Luís Fernando; Moreira, Tiana Carla Lopes; de Oliveira Souza, Vanessa Cristina; Barbosa, Fernando; Saiki, Mitiko; Saldiva, Paulo Hilário Nascimento; Mauad, Thais

2016-09-01

Although urban horticulture provides multiple benefits to society, the extent to which these vegetables are contaminated by the absorption of chemical elements derived from atmospheric deposition is unclear. This study was designed to evaluate the influence of air pollution on leafy vegetables in community gardens of Sao Paulo, Brazil. Vegetable seedlings of Brassica oleracea var. acephala (collard greens) and Spinacia oleracea (spinach) obtained in a non-polluted rural area and growing in vessels containing standard uncontaminated soil were exposed for three consecutive periods of 30, 60 and 90 days in 10 community gardens in Sao Paulo and in one control site. The concentrations of 17 chemical elements (traffic-related elements and those essential to plant biology) were quantified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Tillandsia usneoides L. specimens were used as air plant biomonitors. The concentrations of As, Cd, Cr and Pb found in vegetables were compared to the recommended values for consumption. Principal Component Analysis (PCA) was used to cluster the elemental concentrations, and Generalized Linear Models (GLMs) were employed to evaluate the association of the factor scores from each PCA component with variables such as local weather, traffic burden and vertical barriers adjacent to the gardens. We found significant differences in the elemental concentrations of the vegetables in the different community gardens. These differences were related to the overall traffic burden, vertical obstacles and local weather. The Pb and Cd concentrations in both vegetables exceeded the limit values for consumption after 60 days of exposure. A strong correlation was observed between the concentration of traffic-related elements in vegetables and in Tillandsia usneoides L. An exposure response was observed between traffic burden and traffic-derived particles absorbed in the vegetables. Traffic-derived air pollution directly influences the absorption of chemical elements in leafy vegetables, and the levels of these elements may exceed the recommended values for consumption. Copyright © 2016 Elsevier Ltd. All rights reserved.

Quantitative Estimation of Above Ground Crop Biomass using Ground-based, Airborne and Spaceborne Low Frequency Polarimetric Synthetic Aperture Radar

NASA Astrophysics Data System (ADS)

Koyama, C.; Watanabe, M.; Shimada, M.

2016-12-01

Estimation of crop biomass is one of the important challenges in environmental remote sensing related to agricultural as well as hydrological and meteorological applications. Usually passive optical data (photographs, spectral data) operating in the visible and near-infrared bands is used for such purposes. The virtue of optical remote sensing for yield estimation, however, is rather limited as the visible light can only provide information about the chemical characteristics of the canopy surface. Low frequency microwave signals with wavelength longer 20 cm have the potential to penetrate through the canopy and provide information about the whole vertical structure of vegetation from the top of the canopy down to the very soil surface. This phenomenon has been well known and exploited to detect targets under vegetation in the military radar application known as FOPEN (foliage penetration). With the availability of polarimetric interferometric SAR data the use PolInSAR techniques to retrieve vertical vegetation structures has become an attractive tool. However, PolInSAR is still highly experimental and suitable data is not yet widely available. In this study we focus on the use of operational dual-polarization L-band (1.27 GHz) SAR which is since the launch of Japan's Advanced Land Observing Satellite (ALOS, 2006-2011) available worldwide. Since 2014 ALOS-2 continues to deliver such kind of partial polarimetric data for the entire land surface. In addition to these spaceborne data sets we use airborne L-band SAR data acquired by the Japanese Pi-SAR-L2 as well as ultra-wideband (UWB) ground based SAR data operating in the frequency range from 1-4 GHz. By exploiting the complex dual-polarization [C2] Covariance matrix information, the scattering contributions from the canopy can be well separated from the ground reflections allowing for the establishment of semi-empirical relationships between measured radar reflectivity and the amount of fresh-weight above-ground biomass. The proposed methods are validated against independent in situ measurements for a variety of crops including winter wheat, rice, corn, and soy beans. Our results demonstrate the suitability of the approach to estimate biomass with an error smaller than 15%.

Parameterized approximation of lacunarity functions derived from airborne laser scanning point clouds of forested areas

NASA Astrophysics Data System (ADS)

Székely, Balázs; Kania, Adam; Varga, Katalin; Heilmeier, Hermann

2017-04-01

Lacunarity, a measure of the spatial distribution of the empty space is found to be a useful descriptive quantity of the forest structure. Its calculation, based on laser-scanned point clouds, results in a four-dimensional data set. The evaluation of results needs sophisticated tools and visualization techniques. To simplify the evaluation, it is straightforward to use approximation functions fitted to the results. The lacunarity function L(r), being a measure of scale-independent structural properties, has a power-law character. Previous studies showed that log(log(L(r))) transformation is suitable for analysis of spatial patterns. Accordingly, transformed lacunarity functions can be approximated by appropriate functions either in the original or in the transformed domain. As input data we have used a number of laser-scanned point clouds of various forests. The lacunarity distribution has been calculated along a regular horizontal grid at various (relative) elevations. The lacunarity data cube then has been logarithm-transformed and the resulting values became the input of parameter estimation at each point (point of interest, POI). This way at each POI a parameter set is generated that is suitable for spatial analysis. The expectation is that the horizontal variation and vertical layering of the vegetation can be characterized by this procedure. The results show that the transformed L(r) functions can be typically approximated by exponentials individually, and the residual values remain low in most cases. However, (1) in most cases the residuals may vary considerably, and (2) neighbouring POIs often give rather differing estimates both in horizontal and in vertical directions, of them the vertical variation seems to be more characteristic. In the vertical sense, the distribution of estimates shows abrupt changes at places, presumably related to the vertical structure of the forest. In low relief areas horizontal similarity is more typical, in higher relief areas horizontal similarity fades out in short distances. Some of the input data have been acquired in the framework of the ChangeHabitats2 project financed by the European Union. BS contributed as an Alexander von Humboldt Research Fellow.

Vertical Structure of Phyllosphere Fungal Communities in a Tropical Forest in Thailand Uncovered by High-Throughput Sequencing.

PubMed

Izuno, Ayako; Kanzaki, Mamoru; Artchawakom, Taksin; Wachrinrat, Chongrak; Isagi, Yuji

2016-01-01

Phyllosphere fungi harbor a tremendous species diversity and play important ecological roles. However, little is known about their distribution patterns within forest ecosystems. We examined how species diversity and community composition of phyllosphere fungi change along a vertical structure in a tropical forest in Thailand. Fungal communities in 144 leaf samples from 19 vertical layers (1.28-34.4 m above ground) of 73 plant individuals (27 species) were investigated by metabarcoding analysis using Ion Torrent sequencing. In total, 1,524 fungal operational taxonomic units (OTUs) were detected among 890,710 reads obtained from the 144 leaf samples. Taxonomically diverse fungi belonging to as many as 24 orders of Ascomycota and 21 orders of Basidiomycota were detected, most of which inhabited limited parts of the lowest layers closest to the forest floor. Species diversity of phyllosphere fungi was the highest in the lowest layers closest to the forest floor, decreased with increasing height, and lowest in the canopy; 742 and 55 fungal OTUs were detected at the lowest and highest layer, respectively. On the layers close to the forest floor, phyllosphere fungal communities were mainly composed of low frequency OTUs and largely differentiated among plant individuals. Conversely, in the canopy, fungal communities consisted of similar OTUs across plant individuals, and as many as 86.1%-92.7% of the OTUs found in the canopy (≥22 m above ground) were also distributed in the lower layers. Overall, our study showed the variability of phyllosphere fungal communities along the vertical gradient of plant vegetation and environmental conditions, suggesting the significance of biotic and abiotic variation for the species diversity of phyllosphere fungi.

Structural effects of liana presence in secondary tropical dry forests using ground LiDAR

NASA Astrophysics Data System (ADS)

Sánchez-Azofeifa, A.; Portillo-Quintero, C.; Durán, S. M.

2015-10-01

Lianas, woody vines, are a key component of tropical forest because they may reduce carbon storage potential. Lianas are increasing in density and biomass in tropical forests, but it is unknown what the potential consequences of these increases are for forest dynamics. Lianas may proliferate in disturbed areas, such as regenerating forests, but little is known about the role of lianas in secondary succession. In this study, we evaluated the potential of the ground LiDAR to detect differences in the vertical structure of stands of different ages with and without lianas in tropical dry forests. Specifically, we used a terrestrial laser scanner called VEGNET to assess whether liana presence influences the vertical signature of stands of different ages, and whether successional trajectories as detected by the VEGNET could be altered by liana presence. We deployed the VEGNET ground LiDAR system in 15 secondary forests of different ages early (21 years old since land abandonment), intermediate (32-35 years old) and late stages (> 80 years old) with and without lianas. We compared laser-derived vegetation components such as Plant Area Index (PAI), plant area volume density (PAVD), and the radius of gyration (RG) across forest stands between liana and no-liana treatments. In general forest stands without lianas show a clearer distinction of vertical strata and the vertical height of accumulated PAVD. A significant increase of PAI was found from intermediate to late stages in stands without lianas, but in stands where lianas were present there was not a significant trend. This suggests that lianas may be influencing successional trajectories in secondary forests, and these effects can be captured by terrestrial laser scanners such as the VEGNET. This research contributes to estimate the potential effects of lianas in secondary dry forests and highlight the role of ground LiDAR to monitor structural changes in tropical forests due to liana presence.

Effects of Deepwater Horizon Oil on the Movement and Survival of Marsh Periwinkle Snails (Littoraria irrorata).

PubMed

Garner, T Ross; Hart, Michael A; Sweet, Lauren E; Bagheri, Hanna T J; Morris, Jeff; Stoeckel, James A; Roberts, Aaron P

2017-08-01

The Deepwater Horizon (DWH) oil spill resulted in the release of millions of barrels of oil into the Gulf of Mexico, and some marsh shorelines experienced heavy oiling including vegetation laid over under the weight of oil. Periwinkle snails (Littoraria irrorata) are a critical component of these impacted habitats, and population declines following oil spills, including DWH, have been documented. This study determined the effects of oil on marsh periwinkle movement and survivorship following exposure to oil. Snails were placed in chambers containing either unoiled or oiled laid over vegetation to represent a heavily impacted marsh habitat, with unoiled vertical structure at one end. In the first movement assay, snail movement to standing unoiled vegetation was significantly lower in oiled chambers (oil thickness ≈ 1 cm) compared to unoiled chambers, as the majority (∼75%) of snails in oiled habitats never reached standing unoiled vegetation after 72 h. In a second movement assay, there was no snail movement standing unoiled structure in chambers with oil thicknesses of 0.1 and 0.5 cm, while 73% of snails moved in unoiled chambers after 4h. A toxicity assay was then conducted by exposing snails to oil coated Spartina stems in chambers for periods up to 72 h, and mortality was monitored for 7 days post exposure. Snail survival decreased with increasing exposure time, and significant mortality (∼35%) was observed following an oil exposure of less than 24 h. Here, we have shown that oil impeded snail movement to clean habitat over a short distance and resulted in oil-exposure times that decreased survival. Taken together, along with declines documented by others in field surveys, these results suggest that marsh periwinkle snails may have been adversely affected following exposure to DWH oil.

A model for microwave emission from vegetation-covered fields

NASA Technical Reports Server (NTRS)

Mo, T.; Choudhury, B. J.; Schmugge, T. J.; Wang, J. R.; Jackson, T. J.

1982-01-01

The measured brightness temperatures over vegetation-covered fields are simulated by a radiative transfer model which treats the vegetation as a uniform canopy with a constant temperature, over a moist soil which emits polarized microwave radiation. The analytic formula for the microwave emission has four parameters: roughness height, polarization mixing factor, effective canopy optical thickness, and single scattering albedo. A good representation has been obtained with the model for both the horizontally and vertically polarized brightness temperatures at 1.4 and 5 GHz frequencies, over fields covered with grass, soybean and corn. A directly proportional relation is found between effective canopy optical thickness and the amount of water present in the vegetation canopy. The effective canopy single scattering albedo depends on vegetation type.

Plant Growth Research for Food Production: Development and Testing of Expandable Tuber Growth Module

NASA Technical Reports Server (NTRS)

Cordova, Brennan A.

2017-01-01

Controlled and reliable growth of a variety of vegetable crops is an important capability for manned deep space exploration systems for providing nutritional supplementation and psychological benefits to crew members. Because current systems have been limited to leafy vegetables that require minimal root space, a major goal for these systems is to increase their ability to grow new types of crops, including tuber plants and root vegetables that require a large root space. An expandable root zone module and housing was developed to integrate this capability into the Vegetable Production System (Veggie). The expandable module uses a waterproof, gas-permeable bag with a structure that allows for root space to increase vertically throughout the growth cycle to accommodate for expanding tuber growth, while minimizing the required media mass. Daikon radishes were chosen as an ideal tuber crop for their subterraneous tuber size and rapid growth cycle, and investigations were done to study expanding superabsorbent hydrogels as a potential growth media. These studies showed improved water retention, but restricted oxygen availability to roots with pure gel media. It was determined that these hydrogels could be integrated in lower proportions into standard soil to achieve media expansion and water retention desired. Using the constructed module prototype and ideal gel and soil media mixture, daikon radishes are being grown in the system to test the capability and success of the system through a full growth cycle.

Analysis of Synthetic Aperture Radar data acquired over a variety of land cover

NASA Technical Reports Server (NTRS)

Wu, S. T.

1983-01-01

An analysis has been conducted of two-look-angle, multipolarization X-band SAR results. On the basis of the variety of land covers studied, the vertical-vertical polarization (VV) data is judged to contain the highest degree of contrast, while the horizontal-vertical (HV) polarization contained the least. VV polarization data is accordingly recommended for forest vegetation classification in those cases where only one data channel is available. The inclusion of horizontal-horizontal polarization data, however, is noted to be capable of delineating special surface features.

A simple graphical approach to quantitative monitoring of rangelands

USGS Publications Warehouse

Riginos, C.; Herrick, J.E.; Sundaresan, S.R.; Farley, C.; Belnap, J.

2011-01-01

The article reviews graphical interpretation of the four monitoring methods that can be used to generate a variety of indicators of rangeland ecosystem function. Data for all four of the monitoring methods can be recorded on a single data sheet that is designed to be usable by somebody with minimal literacy. Indicators of plant and ground cover are central to most long-term monitoring systems. Plant and ground-cover data inform managers about forage availability, plant community composition and structure, and risk of runoff and erosion. The spatial arrangement of plants at a site in addition to the percent of the ground that is covered by plants is an important determinant of erosion potential. Vertical vegetation structure can be monitored by capturing data on maximum plant height at each stick location. Plant density method can provide an early indicator of future changes in plant cover, forage, quality, and habitat structure.

Research on Inversion Models for Forest Height Estimation Using Polarimetric SAR Interferometry

NASA Astrophysics Data System (ADS)

Zhang, L.; Duan, B.; Zou, B.

2017-09-01

The forest height is an important forest resource information parameter and usually used in biomass estimation. Forest height extraction with PolInSAR is a hot research field of imaging SAR remote sensing. SAR interferometry is a well-established SAR technique to estimate the vertical location of the effective scattering center in each resolution cell through the phase difference in images acquired from spatially separated antennas. The manipulation of PolInSAR has applications ranging from climate monitoring to disaster detection especially when used in forest area, is of particular interest because it is quite sensitive to the location and vertical distribution of vegetation structure components. However, some of the existing methods can't estimate forest height accurately. Here we introduce several available inversion models and compare the precision of some classical inversion approaches using simulated data. By comparing the advantages and disadvantages of these inversion methods, researchers can find better solutions conveniently based on these inversion methods.

Cellular responses in the cyanobacterial symbiont during its vertical transfer between plant generations in the Azolla microphylla symbiosis.

PubMed

Zheng, Weiwen; Bergman, Birgitta; Chen, Bin; Zheng, Siping; Guan, Xiong; Xiang, Guan; Rasmussen, Ulla

2009-01-01

The nitrogen-fixing symbiosis between cyanobacteria and the water fern Azolla microphylla is, in contrast to other cyanobacteria-plant symbioses, the only one of a perpetual nature. The cyanobacterium is vertically transmitted between the plant generations, via vegetative fragmentation of the host or sexually within megasporocarps. In the latter process, subsets of the cyanobacterial population living endophytically in the Azolla leaves function as inocula for the new plant generations. Using electron microscopy and immunogold-labeling, the fate of the cyanobacterium during colonization and development of the megasporocarp was revealed. On entering the indusium chamber of the megasporocarps as small-celled motile cyanobacterial filaments (hormogonia), these differentiated into large thick-walled akinetes (spores) in a synchronized manner. This process was accompanied by cytoplasmic reorganizations and the release of numerous membrane vesicles, most of which contained DNA, and the formation of a highly structured biofilm. Taken together the data revealed complex adaptations in the cyanobacterium during its transition between plant generations.

Forest edges: Effects on vegetation, environmental gradients and local avian communities in the Sierra Juarez, Oaxaca, Mexico

NASA Astrophysics Data System (ADS)

Burcsu, Theresa Katherine

Edge effects are among the most serious threats to forest integrity because as global forest cover decreases overall, forest edge influence increases proportionally, driving habitat change and loss. Edge effects occur at the division between adjacent habitat types. Our understanding of edge effects comes mainly from tropical wet, temperate and boreal forests. Because forest structure in moisture-limited forests differs from wetter forest types, edge dynamics are likely to differ as well. Moreover, dry forests in the tropics have been nearly eliminated or exist only as forest fragments, making edge influence an important conservation and management concern for remaining dry forests. This study addresses this gap in the edge influence knowledge by examining created, regenerating edges associated with forest management in a seasonally dry pine-oak forest of Oaxaca, creating a new data point in edge effects research. In this study I used Landsat TM imagery and a modified semivariance analysis to estimate the distance of edge influence for vegetation. I also used field methods to characterize forest structure and estimate edge influence on canopy and subcanopy vegetation. To finalize the project I extended the study to bird assemblages to identify responses and habitat preferences to local-scale changes associated with regenerating edges created by group-selection timber harvest. Remote sensing analysis estimated that the distance of edge influence was 30-90 m from the edge. Vegetation analysis suggested that edge effects were weak relative to wetter forest types and that remote sensing data did not provide an estimate that was directly applicable to field-measured vegetative edge effects. The bird assemblages likewise responded weakly to habitat change associated with edge effect. Open canopy structure, simple vertical stratigraphy, and topographic variation create forest conditions in which small openings do not create a high contrast to undisturbed forest. Thus, in this seasonally dry, open forest, vegetation and bird communities respond less to small openings than they do in wetter, more closed-canopy forests. Management practices and historical land-use interact and interfere with the detectability of edge influence in our study area. These results support hypotheses proposed for open forest types and suggest that patterns in edge influence in wet forest types may not be applicable to dry sites.

Marine Riparian Vegetation Communities of Puget Sound

DTIC Science & Technology

2007-02-01

species . In areas of frequent disturbance, early successional trees , such as red alder and maple, dominated coastal forests. Douglas fir is currently...sea level to the mountain tops), forest types are broken into zones, represented by the dominant canopy ( tree ) species , or cli- max community, with...Within each zone, there is also vertical stratification of vegetation types, including dominant canopy tree species , understory trees and shrubs, and

Nest Records of Wreathed Hornbill (Rhyticeros undulates) in Gunung Gentong Station, Mount Ungaran Central Java

NASA Astrophysics Data System (ADS)

Rahayuningsih, M.; Kartijomo, NE; Retnaningsih, A.; Munir, M.; Dahlan, J.

2017-04-01

The remaining forest of Mount Ungaran, Central Javais the suitable habitat of Wreathed Hornbill (Rhyticeros undulatus), especially for a nesting site. The objective of the study was to analyse the nest record and characteristics of habitat around the nest, especially in Gunung Gentong station. The research was conducted from 2010-2016 using exploration method. The methodhabitat profile of the vertical structure tree canopy was taken by plot size 60 × 20 m. Measurements were taken to the standing of vegetation, canopy closure, the direction of the canopy, height canopy, a former branch of the vegetation height, and stem diameter. The Result of the study showed that Gunung Gentong is one of the research station that we have been recorded for nesting site on 2010-2015. Atotal of the nest record on Gunung Genting station was 10 nests. Estimate the elevation of nest location between 939-1240 AMSL. The tree species that used for nesting was Syzygium glabatrum, Syzygium antisepticum, Ceratoxylon formosum, and Ficus sp

Effects of plant phenology and vertical height on accuracy of radio-telemetry locations

USGS Publications Warehouse

Grovenburg, Troy W.; Jacques, Christopher N.; Klaver, Robert W.; DePerno, Christopher S.; Lehman, Chad P.; Brinkman, Todd J.; Robling, Kevin A.; Rupp, Susan P.; Jenks, Jonathan A.

2013-01-01

The use of very high frequency (VHF) radio-telemetry remains wide-spread in studies of wildlife ecology and management. However, few studies have evaluated the influence of vegetative obstruction on accuracy in differing habitats with varying transmitter types and heights. Using adult and fawn collars at varying heights above the ground (0, 33, 66 and 100 cm) to simulate activities (bedded, feeding and standing) and ages (neonate, juvenile and adult) of deer Odocoileus spp., we collected 5,767 bearings and estimated 1,424 locations (28-30 for each of 48 subsamples) in three habitat types (pasture, grassland and forest), during two stages of vegetative growth (spring and late summer). Bearing error was approximately twice as large at a distance of 900 m for fawn (9.9°) than for adult deer collars (4.9°). Of 12 models developed to explain the variation in location error, the analysis of covariance model (HT*D + C*D + HT*TBA + C*TBA) containing interactions of height of collar above ground (HT), collar type (C), vertical height of understory vegetation (D) and tree basal area (TBA) was the best model (wi = 0.92) and explained ∼ 71% of the variation in location error. Location error was greater for both collar types at 0 and 33 cm above the ground compared to 66 and 100 cm above the ground; however, location error was less for adult than fawn collars. Vegetation metrics influenced location error, which increased with greater vertical height of understory vegetation and tree basal area. Further, interaction of vegetation metrics and categorical variables indicated significant effects on location error. Our results indicate that researchers need to consider study objectives, life history of the study animal, signal strength of collar (collar type), distance from transmitter to receiver, topographical changes in elevation, habitat composition and season when designing telemetry protocols. Bearing distances in forested habitat should be decreased (approximately 23% in our study) compared to bearing distances in open habitat to maintain a consistent bearing error across habitats. Additionally, we believe that field biologists monitoring neonate ungulates for habitat selection should rely on visual locations rather than using VHF-collars and triangulation.

Spaceborne potential for examining taiga-tundra ecotone form and vulnerability

NASA Astrophysics Data System (ADS)

Montesano, Paul M.; Sun, Guoqing; Dubayah, Ralph O.; Ranson, K. Jon

2016-07-01

In the taiga-tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density, and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, variable, and widespread vegetation change warrants the application of spaceborne data including high-resolution (< 5 m) spaceborne imagery (HRSI) across broad scales for examining TTE form and predicting dynamics. This study analyzes forest structure at the patch scale in the TTE to provide a means to examine both vertical and horizontal components of ecotone form. We demonstrate the potential of spaceborne data for integrating forest height and density to assess TTE form at the scale of forest patches across the circumpolar biome by (1) mapping forest patches in study sites along the TTE in northern Siberia with a multi-resolution suite of spaceborne data and (2) examining the uncertainty of forest patch height from this suite of data across sites of primarily diffuse TTE forms. Results demonstrate the opportunities for improving patch-scale spaceborne estimates of forest height, the vertical component of TTE form, with HRSI. The distribution of relative maximum height uncertainty based on prediction intervals is centered at ˜ 40 %, constraining the use of height for discerning differences in forest patches. We discuss this uncertainty in light of a conceptual model of general ecotone forms and highlight how the uncertainty of spaceborne estimates of height can contribute to the uncertainty in identifying TTE forms. A focus on reducing the uncertainty of height estimates in forest patches may improve depiction of TTE form, which may help explain variable forest responses in the TTE to climate change and the vulnerability of portions of the TTE to forest structure change.

Simulation of Surface Energy Fluxes and Snow Interception Using a Higher Order Closure Multi-Layer Soil-Vegetation-Atmospheric Model: The Effect of Canopy Shape and Structure

NASA Astrophysics Data System (ADS)

McGowan, L. E.; Dahlke, H. E.; Paw U, K. T.

2015-12-01

Snow cover is a critical driver of the Earth's surface energy budget, climate change, and water resources. Variations in snow cover not only affect the energy budget of the land surface but also represent a major water supply source. In California, US estimates of snow depth, extent, and melt in the Sierra Nevada are critical to estimating the amount of water available for both California agriculture and urban users. However, accurate estimates of snow cover and snow melt processes in forested area still remain a challenge. Canopy structure influences the vertical and spatiotemporal distribution of snow, and therefore ultimately determines the degree and extent by which snow alters both the surface energy balance and water availability in forested regions. In this study we use the Advanced Canopy-Atmosphere-Soil algorithm (ACASA), a multi-layer soil-vegetation-atmosphere numerical model, to simulate the effect of different snow-covered canopy structures on the energy budget, and temperature and other scalar profiles within different forest types in the Sierra Nevada, California. ACASA incorporates a higher order turbulence closure scheme which allows the detailed simulation of turbulent fluxes of heat and water vapor as well as the CO2 exchange of several layers within the canopy. As such ACASA can capture the counter gradient fluxes within canopies that may occur frequently, but are typically unaccounted for, in most snow hydrology models. Six different canopy types were modeled ranging from coniferous forests (e.g. most biomass near the ground) to top-heavy (e.g. most biomass near the top of the crown) deciduous forests to multi-layered forest canopies (e.g. mixture of young and mature trees). Preliminary results indicate that the canopy shape and structure associated with different canopy types fundamentally influence the vertical scalar profiles (including those of temperature, moisture, and wind speed) in the canopy and thus alter the interception and snow melt dynamics in forested land surfaces. The turbulent transport dynamics, including counter-gradient fluxes, and radiation features including land surface albedo, are discussed in the context of the snow energy balance.

Quantifying seasonal dynamics of canopy structure and function using inexpensive narrowband spectral radiometers

NASA Astrophysics Data System (ADS)

Vierling, L. A.; Garrity, S. R.; Campbell, G.; Coops, N. C.; Eitel, J.; Gamon, J. A.; Hilker, T.; Krofcheck, D. J.; Litvak, M. E.; Naupari, J. A.; Richardson, A. D.; Sonnentag, O.; van Leeuwen, M.

2011-12-01

Increasing the spatial and temporal density of automated environmental sensing networks is necessary to quantify shifts in plant structure (e.g., leaf area index) and function (e.g., photosynthesis). Improving detection sensitivity can facilitate a mechanistic understanding by better linking plant processes to environmental change. Spectral radiometer measurements can be highly useful for tracking plant structure and function from diurnal to seasonal time scales and calibrating and validating satellite- and aircraft-based spectral measurements. However, dense ground networks of such instruments are challenging to establish due to the cost and complexity of automated instrument deployment. We therefore developed simple to operate, lightweight and inexpensive narrowband (~10nm bandwidth) spectral instruments capable of continuously measuring four to six discrete bands that have proven capacity to describe key physiological processes and structural features of plant canopies. These bands are centered at 530, 570, 675, 800, 880, and 970 nm to enable calculation of the physiological reflectance index (PRI), normalized difference vegetation index (NDVI), green NDVI (gNDVI), and water band index (WBI) collected above and within vegetation canopies. To date, measurements have been collected above grassland, semi-arid shrub steppe, piñon-juniper woodland, dense conifer forest, mixed deciduous-conifer forest, and cropland canopies, with additional measurements collected along vertical transects through a temperate conifer rainforest. Findings from this work indicate not only that key shifts in plant phenology, physiology, and structure can be captured using such instruments, but that the temporally dense nature of the measurements can help to disentangle heretofore unreported complexities of simultaneous phenological and structural change on canopy reflectance.

Summer Harvest in Saratov, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

Russia's Saratov Oblast (province) is located in the southeastern portion of the East-European plain, in the Lower Volga River Valley. Southern Russia produces roughly 40 percent of the country's total agricultural output, and Saratov Oblast is the largest producer of grain in the Volga region. Vegetation changes in the province's agricultural lands between spring and summer are apparent in these images acquired on May 31 and July 18, 2002 (upper and lower image panels, respectively) by the Multi-angle Imaging SpectroRadiometer (MISR).

The left-hand panels are natural color views acquired by MISR's vertical-viewing (nadir) camera. Less vegetation and more earth tones (indicative of bare soils) are apparent in the summer image (lower left). Farmers in the region utilize staggered sowing to help stabilize yields, and a number of different stages of crop maturity can be observed. The main crop is spring wheat, cultivated under non-irrigated conditions. A short growing season and relatively low and variable rainfall are the major limitations to production. Saratov city is apparent as the light gray pixels on the left (west) bank of the Volga River. Riparian vegetation along the Volga exhibits dark green hues, with some new growth appearing in summer.

The right-hand panels are multi-angle composites created with red band data from MISR's 60-degree backward, nadir and 60-degree forward-viewing cameras displayed as red, green and blue respectively. In these images, color variations serve as a proxy for changes in angular reflectance, and the spring and summer views were processed identically to preserve relative variations in brightness between the two dates. Urban areas and vegetation along the Volga banks look similar in the two seasonal multi-angle composites. The agricultural areas, on the other hand, look strikingly different. This can be attributed to differences in brightness and texture between bare soil and vegetated land. The chestnut-colored soils in this region are brighter in MISR's red band than the vegetation. Because plants have vertical structure, the oblique cameras observe a greater proportion of vegetation relative to the nadir camera, which sees more soil. In spring, therefore, the scene is brightest in the vertical view and thus appears with an overall greenish hue. In summer, the soil characteristics play a greater role in governing the appearance of the scene, and the angular reflectance is now brighter at the oblique view angles (displayed as red and blue), thus imparting a pink color to much of the farmland and a purple color to areas along the banks of several narrow rivers. The unusual appearance of the clouds is due to geometric parallax which splits the imagery into spatially separated components as a consequence of their elevation above the surface.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and views almost the entire globe every 9 days. These images are a portion of the data acquired during Terra orbits 13033 and 13732, and cover an area of about 173 kilometers x 171 kilometers. They utilize data from blocks 49 to 50 within World Reference System-2 path 170.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Impact of vegetation on the hydrodynamics and morphological changes of the Wax Lake Delta during hurricanes

NASA Astrophysics Data System (ADS)

Xing, F.; Kettner, A. J.; Syvitski, J. P.; Ye, Q.; Bevington, A.; Twilley, R.; Atkinson, J. H.

2013-12-01

Coastal wetlands are natural barriers for storms, but have become more vulnerable especially when considering sea level rise and intensification of hurricanes due to global climate change. We use the numerical model Delft3D, which incorporates a newly developed vegetation routine to analyze the impact of natural vegetation on the morphological changes of coastal wetlands. The vegetation routine takes into account: 1) the influence of vertically oriented stems of plants as well as horizontally oriented stems (bent or broken but still attached to the belowground roots and rhizomes) on the flow turbulence as well as flow momentum, and 2) the influence of plant roots on the submerged soil strength. The model is applied to the Wax Lake Delta, a river-dominated delta that is part of the larger Mississippi River Delta system, during extreme events (hurricane Katrina and Rita (2005)). Hydrodynamic components as well as waves and salinity are included in the Delft3D model simulation. Results reveal that the submerged aboveground plant stems significantly decrease flow velocity and protect the wetland from erosion. When flow velocity exceeds a critical value, plant stems start to orient horizontally and lie on the bed, which changes the 3D vertical flow structure to free water condition (log profile), and also increases the bed roughness on the wetlands. Roots help to increase the soil strength, reducing erosion of the wetlands. However, roots can also intensify erosion if they got pulled out of the soil during storm events. Typically the whole root system of plants will be pulled out together, leading to a mat of soil that is eroded. This process has been observed for some parts of the Mississippi Delta during severe hurricanes like hurricane Katrina. Storm surges generated by hurricanes can push a large amount of saline water into the freshwater wetlands. The high salinity water increases flocculation and therefore sedimentation. Overall, plants have a complex impact on the hydrodynamic and morphological changes of coastal wetlands, which are not yet fully understood. This study shows that plants have to be taken into consideration when studying morphological processes of wetlands, especially during extreme events, such as hurricanes.

Monitoring global vegetation using Nimbus-7 37 GHz data - Some empirical relations

NASA Technical Reports Server (NTRS)

Choudhury, B. J.; Tucker, C. J.

1987-01-01

The difference of the vertically and horizontally polarized brightness temperatures observed by the 37 GHz channel of the SMMR on board the Nimbus-7 satellite are correlated temporally with three indicators of vegetation density, namely the temporal variation of the atmospheric CO2 concentration at Mauna Loa (Hawaii), rainfall over the Sahel and the normalized difference vegetation index derived from the AVHRR on board the NOAA-7 satellite. SMMR 37 GHz and AVHRR provide complementary data sets for monitoring global vegetation, the 37 GHz data being more suitable for arid and semiarid regions as these data are more sensitive to changes in sparse vegetation. The 37-GHz data might be useful for understanding desertification and indexing Co2 exchange between the biosphere and the atmosphere.

Determination of strength behaviour of slope supported by vegetated crib walls using centrifuge model testing

NASA Astrophysics Data System (ADS)

Sudan Acharya, Madhu

2010-05-01

The crib retaining structures made of wooden/bamboo logs with live plants inside are called vegetative crib walls which are now becoming popular due to their advantages over conventional civil engineering walls. Conventionally, wooden crib walls were dimensioned based on past experiences. At present, there are several guidelines and design standards for machine finished wooden crib walls, but only few guidelines for the design and construction of vegetative log crib walls are available which are generally not sufficient for an economic engineering design of such walls. Analytical methods are generally used to determine the strength of vegetated crib retaining walls. The crib construction is analysed statically by satisfying the condition of static equilibrium with acceptable level of safety. The crib wall system is checked for internal and external stability using conventional monolithic and silo theories. Due to limitations of available theories, the exact calculation of the strength of vegetated wooden/bamboo crib wall cannot be made in static calculation. Therefore, experimental measurements are generally done to verify the static analysis. In this work, a model crib construction (1:20) made of bamboo elements is tested in the centrifuge machine to determine the strength behaviour of the slope supported by vegetated crib retaining wall. A geotechnical centrifuge is used to conduct model tests to study geotechnical problems such as the strength, stiffness and bearing capacity of different structures, settlement of embankments, stability of slopes, earth retaining structures etc. Centrifuge model testing is particularly well suited to modelling geotechnical events because the increase in gravitational force creates stresses in the model that are equivalent to the much larger prototype and hence ensures that the mechanisms of ground movements observed in the tests are realistic. Centrifuge model testing provides data to improve our understanding of basic mechanisms of deformation and failure and provides benchmarks useful for verification of numerical models. In this case this test is mainly carried out to verify the stability analysis and deformation characteristics of a bamboo crib wall. Models of crib wall of dimensions 37x13x10 cm and 37x13x14cm were placed inside a Plexiglas box of internal dimensions of 42.5x42.5x30 cm and slope was formed leaving a space about 10 cm in the front. The model crib wall tests were all performed at 40-70 times earth's gravity. This means that the 5 mm diameters bamboo rods in model used represents a prototype diameter of 20-35 cm. The horizontal and vertical displacements were measured with the help of three displacements sensor fixed horizontally and one sensor fixed vertically at the top of the model crib wall. All together nine tests were carried out with varying model parameters. Standard medium sand and coarse sand were used as fill material in the testing. Two wall heights variations and three slopes variations were used in the testing. The test model was constructed either compacted or uncompacted. The compaction in the model was carried out by hand to about 90% of the Proctor density. Three slopes inclinations were used. For flat slope the slope angle was less than 25° , and for steep slope it was 25° -35° and for extremely steep slope it was > 35° . The test results and conclusions are presented in this paper.

Advances in animal ecology from 3D ecosystem mapping with LiDAR

NASA Astrophysics Data System (ADS)

Davies, A.; Asner, G. P.

2015-12-01

The advent and recent advances of Light Detection and Ranging (LiDAR) have enabled accurate measurement of 3D ecosystem structure. Although the use of LiDAR data is widespread in vegetation science, it has only recently (< 14 years) been applied to animal ecology. Despite such recent application, LiDAR has enabled new insights in the field and revealed the fundamental importance of 3D ecosystem structure for animals. We reviewed the studies to date that have used LiDAR in animal ecology, synthesising the insights gained. Structural heterogeneity is most conducive to increased animal richness and abundance, and increased complexity of vertical vegetation structure is more positively influential than traditionally measured canopy cover, which produces mixed results. However, different taxonomic groups interact with a variety of 3D canopy traits and some groups with 3D topography. LiDAR technology can be applied to animal ecology studies in a wide variety of environments to answer an impressive array of questions. Drawing on case studies from vastly different groups, termites and lions, we further demonstrate the applicability of LiDAR and highlight new understanding, ranging from habitat preference to predator-prey interactions, that would not have been possible from studies restricted to field based methods. We conclude with discussion of how future studies will benefit by using LiDAR to consider 3D habitat effects in a wider variety of ecosystems and with more taxa to develop a better understanding of animal dynamics.

Microwave propagation constant for a vegetation canopy with vertical stalks

NASA Technical Reports Server (NTRS)

Ulaby, Fawwaz T.; Tavakoli, Ahad; Senior, Thomas B. A.

1987-01-01

An equivalent-medium model is developed to relate the propagation constant gamma, associated with propagation of the mean field through a vegetation canopy, to the geometrical and dielectric parameters of the canopy constituents. The model is intended for media containing vertical cylinders, representing the stalks, and randomly oriented disks, representing the leaves. The formulation accounts for both absorption and scattering by the cylinders, but uses a quasi-static approximation with respect to the leaves. The model was found to be in good agreement with experimental results at 1.62 and 4.75 GHz, but underestimates the extinction loss at 10.2 GHz. The experimental component of the study included measurements of the attenuation loss for horizontally polarized and vertically polarized waves transmitted through a fully grown corn canopy, and of the phase difference between the two transmitted waves. The measurements were made at incidence angles of 20, 40, 60, and 90 deg relative to normal incidence. The major conclusion of this study is that the proposed model is suitable for corn-like canopies, provided the leaves are smaller than lambda in size.

Forest structure analysis combining laser scanning with digital airborne photogrammetry

NASA Astrophysics Data System (ADS)

Lissak, Candide; Onda, Yuichi; Kato, Hiroaki

2017-04-01

The interest of Light Detection and Ranging (LiDAR) for vegetation structure analysis has been demonstrated in several research context. Indeed, airborne or ground Lidar surveys can provide detailed three-dimensional data of the forest structure from understorey forest to the canopy. To characterize at different timescale the vegetation components in dense cedar forests we can combine several sources point clouds from Lidar survey and photogrammetry data. For our study, Terrestrial Laser Scanning (TLS-Leica ScanStation C10 processed with Cyclone software) have been lead in three forest areas (≈ 200m2 each zone) mainly composed of japanese cedar (Japonica cryptomeria), in the region of Fukushima (Japan). The study areas are characterized by various vegetation densities. For the 3 areas, Terrestrial laser scanning has been performed from several location points and several heights. Various floors shootings (ground, 4m, 6m and 18m high) were able with the use of a several meters high tower implanted to study the canopy evolution following the Fukushima Daiishi nuclear power plant accident. The combination of all scanners provides a very dense 3D point cloud of ground and canopy structure (average 300 000 000 points). For the Tochigi forest area, a first test of a low-cost Unmanned Aerial Vehicle (UAV) photogrammetry has been lead and calibrated by ground GPS measurements to determine the coordinates of points. TLS combined to UAV photogrammetry make it possible to obtain information on vertical and horizontal structure of the Tochigi forest. This combination of technologies will allow the forest structure mapping, morphometry analysis and the assessment of biomass volume evolution from multi-temporal point clouds. In our research, we used a low-cost UAV 3 Advanced (200 m2 cover, 1300 pictures...). Data processing were performed using PotoScan Pro software to obtain a very dense point clouds to combine to TLS data set. This low-cost UAV photogrammetry data has been successfully used to derive information on the canopy cover. The purpose of this poster is to present the usability of combined remote sensing methods for forest structure analysis and 3D model reconstitution for a trend analysis of the forest changes.

Primary Succession on a Hawaiian Dryland Chronosequence

DOE PAGES

Kinney, Kealohanuiopuna M.; Asner, Gregory P.; Cordell, Susan; ...

2015-06-12

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature nativemore » shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. In conclusion, this work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.« less

Primary Succession on a Hawaiian Dryland Chronosequence

PubMed Central

Kinney, Kealohanuiopuna M.; Asner, Gregory P.; Cordell, Susan; Chadwick, Oliver A.; Heckman, Katherine; Hotchkiss, Sara; Jeraj, Marjeta; Kennedy-Bowdoin, Ty; Knapp, David E.; Questad, Erin J.; Thaxton, Jarrod M.; Trusdell, Frank; Kellner, James R.

2015-01-01

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands. PMID:26066334

Characterizing 3D Vegetation Structure from Space: Mission Requirements

NASA Technical Reports Server (NTRS)

Hall, Forrest G.; Bergen, Kathleen; Blair, James B.; Dubayah, Ralph; Houghton, Richard; Hurtt, George; Kellndorfer, Josef; Lefsky, Michael; Ranson, Jon; Saatchi, Sasan;

Quantifying the Interactions Between Soil Thermal Characteristics, Soil Physical Properties, Hydro-geomorphological Conditions and Vegetation Distribution in an Arctic Watershed

NASA Astrophysics Data System (ADS)

Dafflon, B.; Leger, E.; Robert, Y.; Ulrich, C.; Peterson, J. E.; Soom, F.; Biraud, S.; Tran, A. P.; Hubbard, S. S.

2017-12-01

Improving understanding of Arctic ecosystem functioning and parameterization of process-rich hydro-biogeochemical models require advances in quantifying ecosystem properties, from the bedrock to the top of the canopy. In Arctic regions having significant subsurface heterogeneity, understanding the link between soil physical properties (incl. fraction of soil constituents, bedrock depth, permafrost characteristics), thermal behavior, hydrological conditions and landscape properties is particularly challenging yet is critical for predicting the storage and flux of carbon in a changing climate. This study takes place in Seward Peninsula Watersheds near Nome AK and Council AK, which are characterized by an elevation gradient, shallow bedrock, and discontinuous permafrost. To characterize permafrost distribution where the top of permafrost cannot be easily identified with a tile probe (due to rocky soil and/or large thaw layer thickness), we developed a novel technique using vertically resolved thermistor probes to directly sense the temperature regime at multiple depths and locations. These measurements complement electrical imaging, seismic refraction and point-scale data for identification of the various thermal behavior and soil characteristics. Also, we evaluate linkages between the soil physical-thermal properties and the surface properties (hydrological conditions, geomorphic characteristics and vegetation distribution) using UAV-based aerial imaging. Data integration and analysis is supported by numerical approaches that simulate hydrological and thermal processes. Overall, this study enables the identification of watershed structure and the links between various subsurface and landscape properties in representative Arctic watersheds. Results show very distinct trends in vertically resolved soil temperature profiles and strong lateral variations over tens of meters that are linked to zones with various hydrological conditions, soil properties and vegetation types. The interaction between these zones is of strong interest to understand the evolution of the landscape and the permafrost distribution. The obtained information is expected to be useful for improving predictions of Arctic ecosystem feedbacks to climate.

Turbulent Structures in a Pine Forest with a Deep and Sparse Trunk Space: Stand and Edge Regions

NASA Astrophysics Data System (ADS)

Dupont, Sylvain; Irvine, Mark R.; Bonnefond, Jean-Marc; Lamaud, Eric; Brunet, Yves

2012-05-01

Forested landscapes often exhibit large spatial variability in vertical and horizontal foliage distributions. This variability may affect canopy-atmosphere exchanges through its action on the development of turbulent structures. Here we investigate in neutral stratification the turbulent structures encountered in a maritime pine forest characterized by a high, dense foliated layer associated with a deep and sparse trunk space. Both stand and edge regions are considered. In situ measurements and the results of large-eddy simulations are used and analyzed together. In stand conditions, far from the edge, canopy-top structures appear strongly damped by the dense crown layer. Turbulent wind fluctuations within the trunk space, where the momentum flux vanishes, are closely related to these canopy-top structures through pressure diffusion. Consequently, autocorrelation and spectral analyses are not quite appropriate to characterize the vertical scale of coherent structures in this type of canopy, as pressure diffusion enhances the actual scale of structures. At frequencies higher than those associated with canopy-top structures, wind fluctuations related to wake structures developing behind tree stems are observed within the trunk space. They manifest themselves in wind velocity spectra as secondary peaks in the inertial subrange region, confirming the hypothesis of spectral short-cuts in vegetation canopies. In the edge region specific turbulent structures develop just below the crown layer, in addition to canopy-top structures. They are generated by the wind shear induced by the sub-canopy wind jet that forms at the edge. These structures provide a momentum exchange mechanism similar to that observed at the canopy top but in the opposite direction and with a lower magnitude. They may develop as in plane mixing-layer flows, with some perturbations induced by canopy-top structures. Wake structures are also observed within the trunk space in the edge region.

Representing Northern Peatland Hydrology and Biogeochemistry with ALM Land Surface Model

NASA Astrophysics Data System (ADS)

Shi, X.; Ricciuto, D. M.; Thornton, P. E.; Hanson, P. J.; Xu, X.; Mao, J.; Warren, J.; Yuan, F.; Norby, R. J.; Sebestyen, S.; Griffiths, N.; Weston, D. J.; Walker, A.

2017-12-01

Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pool and vulnerability to hydrological change. Predictive understanding of northern peatland hydrology is a necessary precursor to understanding the fate of massive carbon stores in these systems under the influence of present and future climate change. Current models have begun to address microtopographic controls on peatland hydrology, but none have included a prognostic calculation of peatland water table depth for a vegetated wetland, independent of prescribed regional water tables. Firstly, we introduce a new configuration of the land model (ALM) of Accelerated Climate model for Energy (ACME), which includes a fully prognostic water table calculation for a vegetated peatland. Secondly, we couple our new hydrology treatment with vertically structured soil organic matter pool, and the addition of components from methane biogeochemistry. Thirdly, we introduce a new PFT for mosses and implement the water content dynamics and physiology of mosses. We inform and test our model based on SPRUCE experiment to get the reasonable results for the seasonal dynamics water table depths, water content dynamics and physiology of mosses, and correct soil carbon profiles. Then, we use our new model structure to test the how the water table depth and CH4 emission will respond to elevated CO2 and different warming scenarios.

Detection of underground structures using UAV and field spectroscopy for defence and security in Cyprus

NASA Astrophysics Data System (ADS)

Melillos, George; Themistocleous, Kyriacos; Prodromou, Maria; Hadjimitsis, Diofantos G.

2017-10-01

The purpose of this paper is to present the results obtained from unmanned aerial vehicle (UAV) and field spectroscopy campaigns for detecting underground structures. Underground structures can affect their surrounding landscapes in different ways, such as soil moisture content, soil composition and vegetation vigor. The last is often observed on the ground as a crop mark; a phenomenon which can be used as a proxy to denote the presence of underground non-visible structures. A number of vegetation indices such as the Normalized Difference Vegetation Index (NDVI), Simple Ratio (SR), Difference Vegetation Index (DVI) and Soil Adjusted Vegetation Index (SAVI) were utilized for the development of a vegetation index-based procedure aiming at the detection of underground military structures by using existing vegetation indices or other in-band algorithms. The measurements were taken at the following test areas such as: (a) vegetation area covered with the vegetation (barley), in the presence of an underground military structure (b) vegetation area covered with the vegetation (barley), in the absence of an underground military structure.

Airborne Laser Scanning - based vegetation classification in grasslands: a feasibility study

NASA Astrophysics Data System (ADS)

Zlinszky, András; Vári, Ágnes; Deák, Balázs; Mücke, Werner; Székely, Balázs

2013-04-01

Airborne Laser Scanning is traditionally used for topography mapping, exploiting its ability to map terrain elevation under vegetation cover. Parallel to this, the application of ALS for vegetation classification and mapping of ecological variables is rapidly emerging. Point clouds surveyed by ALS provide accurate representations of vegetation structure and are therefore considered suitable for mapping vegetation classes as long as their vertical structure is characteristic. For this reason, most ALS-based vegetation mapping studies have been carried out in forests, with some rare applications for shrublands or tall grass vegetation such as reeds. The use of remote-sensing derived vegetation maps is widespread in ecological research and is also gaining importance in practical conservation. There is an increasing demand for reliable, high-resolution datasets covering large protected areas. ALS can provide both the coverage and the high resolution, and can prove to be an economical solution due to the potential for automatic processing and the wide range of uses that allows spreading costs. Grasslands have a high importance in nature conservation as due to the drastical land use changes (arable lands, afforestation, fragmentation by linear structures) in the last centuries the extent of these habitats have been considerably reduced. Among the habitat types protected by the Habitat Directive of the Natura 2000 system, several grassland habitat types (e.g. hay meadows, dry grasslands harbouring rare Orchid species) have special priority for conservation. For preserving these habitat types application of a proper management - including mowing or grazing - has a crucial role. Therefore not only the mapping of the locations of habitats but the way of management is needed for representing the natural processes. The objective of this study was to test the applicability of airborne laser scanning for ecological vegetation mapping in and around grasslands. The study site is situated in the Sopron mountains (Western Hungary), in the Soproni-hegység Natura 2000 site which has an area of 52 km2 protected under Natura 2000. While the Natura 2000 site is dominated by forests, it also holds several grassland habitats: lowland and mountain hay meadows, dry grasslands, fringe communities and disturbed secondary grasslands in the forest clearings. In the framework of the Changehabitats2 project, ALS surveys of the area were carried out, under leaf-on conditions in July 2012 and March 2011, with a full-waveform sensor (Riegl LMS-Q680i) operating at 1550 nm. The resulting point density was 12.8 echoes/m2. 10 grasslands were selected from the study site varying in size between 0.1 and 3 km2. The ALS datasets of these sites were processed in OPALS software to a set of rasters representing different variables of the leaf-on and leaf-off point cloud, each with a raster size of 0.5 m * 0.5 m. Echo amplitude for single echoes was calibrated to reflectance using estimated reflectivity of an asphalt surface. A Digital Terrain Model was created using hierarchical robust filtering in SCOP++ software, and normalized digital surface models were calculated by subtracting this from the local surface models. Echo width and surface roughness were also calculated in OPALS. Surface openness was measured in order to distinguish circular and linear features, such as sedge clumps and ploughing marks. Finally, all these rasters were stacked in ENVI software, resulting in a pseudo-image, where each pseudo-channel corresponded to a different ALS-derived variable. Reference datasets were collected in the field using differential GNSS. Habitat type, dominant vegetation species and other features of interest were noted in the point attributes, and a set of 90 circular plots was recorded. These were overlain on the pseudo-image to create regions of interest (ROI), resulting in 100-4000 ROI pixels for each vegetation category. Multivariate statistics were then used in order to analyse the trends in the data: interdependence of the ALS-derived variables was tested by calculating covariance matrices and the separability of the vegetation categories was tested by the Jeffries-Matusita index. The results of the multivariate analysis were used for merging and excluding classes from the initial 24 to find those where the accuracy was sufficient and the results were relevant for conservation. Results show that a large number of variables can be derived from leaf-on and leaf-off ALS surveys that are statistically independent from each other and thus provide a good basis for classification. With appropriate calculation methods, a number of pseudo-bands comparable to multispectral imagery can be reached. These categories are of course not equally relevant for vegetation mapping. Not surprisingly, the categories with the strongest separability are those closely linked to vegetation height or texture. Mown grasslands can be well separated from abandoned grasslands; tussock-forming grasses from more uniform textured tall herbs. While quality control is still in progress and the trade-off between the number of categories and the classification accuracy is evident, it is expected that for a limited range of vegetation classes, the reliability of the method will be comparable to passive optical image processing. Using a classification method slightly different from the conventional ALS-based vegetation mapping approach, encouraging results have been obtained for an area where the vertical structure of the vegetation is limited. The present state of the art of ALS sensors including full waveform processing and calibration of surface reflectance allows vegetation mapping even in grasslands. It is expected that the further development of waveform digitization and the ever-increasing scanning frequencies will further support such studies in the future.

The relative importance of vertical soil nutrient heterogeneity, and mean and depth-specific soil nutrient availabilities for tree species richness in tropical forests and woodlands.

PubMed

Shirima, Deo D; Totland, Ørjan; Moe, Stein R

2016-11-01

The relative importance of resource heterogeneity and quantity on plant diversity is an ongoing debate among ecologists, but we have limited knowledge on relationships between tree diversity and heterogeneity in soil nutrient availability in tropical forests. We expected tree species richness to be: (1) positively related to vertical soil nutrient heterogeneity; (2) negatively related to mean soil nutrient availability; and (3) more influenced by nutrient availability in the upper than lower soil horizons. Using a data set from 60, 20 × 40-m plots in a moist forest, and 126 plots in miombo woodlands in Tanzania, we regressed tree species richness against vertical soil nutrient heterogeneity, both depth-specific (0-15, 15-30, and 30-60 cm) and mean soil nutrient availability, and soil physical properties, with elevation and measures of anthropogenic disturbance as co-variables. Overall, vertical soil nutrient heterogeneity was the best predictor of tree species richness in miombo but, contrary to our prediction, the relationships between tree species richness and soil nutrient heterogeneity were negative. In the moist forest, mean soil nutrient availability explained considerable variations in tree species richness, and in line with our expectations, these relationships were mainly negative. Soil nutrient availability in the top soil layer explained more of the variation in tree species richness than that in the middle and lower layers in both vegetation types. Our study shows that vertical soil nutrient heterogeneity and mean availability can influence tree species richness at different magnitudes in intensively utilized tropical vegetation types.

Geomorphic and ecological effects of Hurricanes Katrina and Rita on coastal Louisiana marsh communities

USGS Publications Warehouse

Piazza, Sarai C.; Steyer, Gregory D.; Cretini, Kari F.; Sasser, Charles E.; Visser, Jenneke M.; Holm, Guerry O.; Sharp, Leigh A.; Evers, D. Elaine; Meriwether, John R.

2011-01-01

Hurricanes Katrina and Rita made landfall in 2005, subjecting the coastal marsh communities of Louisiana to various degrees of exposure. We collected data after the storms at 30 sites within fresh (12), brackish/intermediate (12), and saline (6) marshes to document the effects of saltwater storm surge and sedimentation on marsh community dynamics. The 30 sites were comprised of 15 pairs. Most pairs contained one site where data collection occurred historically (that is, prestorms) and one Coastwide Reference Monitoring System site. Data were collected from spring 2006 to fall 2007 on vegetative species composition, percentage of vegetation cover, aboveground and belowground biomass, and canopy reflectance, along with discrete porewater salinity, hourly surface-water salinity, and water level. Where available, historical data acquired before Hurricanes Katrina and Rita were used to compare conditions and changes in ecological trajectories before and after the hurricanes. Sites experiencing direct and indirect hurricane influences (referred to in this report as levels of influence) were also identified, and the effects of hurricane influence were tested on vegetation and porewater data. Within fresh marshes, porewater salinity was greater in directly impacted areas, and this heightened salinity was reflected in decreased aboveground and belowground biomass and increased cover of disturbance species in the directly impacted sites. At the brackish/intermediate marsh sites, vegetation variables and porewater salinity were similar in directly and indirectly impacted areas, but porewater salinity was higher than expected throughout the study. Interestingly, directly impacted saline marsh sites had lower porewater salinity than indirectly impacted sites, but aboveground biomass was greater at the directly impacted sites. Because of the variable and site-specific nature of hurricane influences, we present case studies to help define postdisturbance baseline conditions in fresh, brackish/ intermediate, and saline marshes. In fresh marshes, the mechanism of hurricane influence varied across the landscape. In the western region, saltwater storm surge inundated freshwater marshes and remained for weeks, effectively causing damage that reset the vegetation community. This is in contrast to the direct physical disturbance of the storm surge in the eastern region, which flipped and relocated marsh mats, thereby stressing the vegetation communities and providing an opportunity for disturbance species to colonize. In the brackish/intermediate marsh, disturbance species took advantage of the opportunity provided by shifting species composition caused by physical and saltwater-induced perturbations, although this shift is likely to be short lived. Saline marsh sites were not negatively impacted to a severe degree by the hurricanes. Species composition of vegetation in saline marshes was not affected, and sediment deposition appeared to increase vegetative productivity. The coastal landscape of Louisiana is experiencing high rates of land loss resulting from natural and anthropogenic causes and is experiencing subsidence rates greater than 10.0 millimeters per year (mm yr-1); therefore, it is important to understand how hurricanes influence sedimentation and soil properties. We document long-term vertical accretion rates and accumulation rates of organic matter, bulk density, carbon and nitrogen. Analyses using caesium-137 to calculate long-term vertical accretion rates suggest that accretion under impounded conditions is less than in nonimpounded conditions in the brackish marsh of the chenier plain. Our data also support previous studies indicating that accumulation rates of organic matter explain much of the variability associated with vertical accretion in brackish/intermediate and saline marshes. In fresh marshes, more of the variability associated with vertical accretion was explained by mineral accumulation than in the other mars

[Seasonal dynamics and vertical distribution pattern of bud bank in different erosion environments on hilly-gully Loess Plateau of Northwest China].

PubMed

Du, Hua-Dong; Jiao, Ju-Ying; Kou, Meng; Wang, Ning

2013-05-01

This paper studied the vegetation composition, bud composition, and the seasonal dynamics and vertical distribution pattern of bud bank in five erosion environments (sunny gully slope, sunny hilly slope, hilltop, shady hilly slope, and shady gully slope) on the hilly-gully Loess Plateau of North Shaanxi. In the study area, the perennial species with perennial bud bank accounted for 80.3% of the total species, while the annual species with seasonal bud bank took up 19.7% of the total. In vegetation turning-green season, there was a relatively large perennial bud bank stock on the sunny hilly-gully slope where serious erosion occurred, while seasonal bud bank showed a higher bud bank density in blossom and fruit-setting season on the hilltop and two shady slopes where soil erosion intensity was relatively gentle. The proportion of underground bud bank to total perennial bud bank in different erosion environments was relatively stable. On the land surface, the perennial bud bank stock was larger on the sunny slope where the soil disturbance often occurred, whereas the seasonal bud bank stock was larger on the shady slope and hilltop. Due to the different species composition of plant communities in different erosion environments, in addition to the disturbance of soil erosion and the seasonal plant regeneration, the seasonal dynamics and vertical distribution pattern of bud bank changed. It was suggested that bud bank played an important role in the vegetation regeneration after the disturbance of soil erosion on the hilly-gully Loess Plateau of North Shaanxi.

Fusion of multi-temporal Airborne Snow Observatory (ASO) lidar data for mountainous vegetation ecosystems studies.

NASA Astrophysics Data System (ADS)

Ferraz, A.; Painter, T. H.; Saatchi, S.; Bormann, K. J.

2016-12-01

Fusion of multi-temporal Airborne Snow Observatory (ASO) lidar data for mountainous vegetation ecosystems studies The NASA Jet Propulsion Laboratory developed the Airborne Snow Observatory (ASO), a coupled scanning lidar system and imaging spectrometer, to quantify the spatial distribution of snow volume and dynamics over mountains watersheds (Painter et al., 2015). To do this, ASO weekly over-flights mountainous areas during snowfall and snowmelt seasons. In addition, there are additional flights in snow-off conditions to calculate Digital Terrain Models (DTM). In this study, we focus on the reliability of ASO lidar data to characterize the 3D forest vegetation structure. The density of a single point cloud acquisition is of nearly 1 pt/m2, which is not optimal to properly characterize vegetation. However, ASO covers a given study site up to 14 times a year that enables computing a high-resolution point cloud by merging single acquisitions. In this study, we present a method to automatically register ASO multi-temporal lidar 3D point clouds. Although flight specifications do not change between acquisition dates, lidar datasets might have significant planimetric shifts due to inaccuracies in platform trajectory estimation introduced by the GPS system and drifts of the IMU. There are a large number of methodologies that address the problem of 3D data registration (Gressin et al., 2013). Briefly, they look for common primitive features in both datasets such as buildings corners, structures like electric poles, DTM breaklines or deformations. However, they are not suited for our experiment. First, single acquisition point clouds have low density that makes the extraction of primitive features difficult. Second, the landscape significantly changes between flights due to snowfall and snowmelt. Therefore, we developed a method to automatically register point clouds using tree apexes as keypoints because they are features that are supposed to experience little change during winter season. We applied the method to 14 lidar datasets (12 snow-on and 2 snow-off) acquired over the Tuolumne River Basin (California) in the year of 2014. To assess the reliability of the merged point cloud, we analyze the quality of vegetation related products such as canopy height models (CHM) and vertical vegetation profiles.

The Use of Sun Elevation Angle for Stereogrammetric Boreal Forest Height in Open Canopies

NASA Technical Reports Server (NTRS)

Montesano, Paul M.; Neigh, Christopher; Sun, Guoqing; Duncanson, Laura Innice; Van Den Hoek, Jamon; Ranson, Kenneth Jon

2017-01-01

Stereogrammetry applied to globally available high resolution spaceborne imagery (HRSI; less than 5 m spatial resolution) yields fine-scaled digital surface models (DSMs) of elevation. These DSMs may represent elevations that range from the ground to the vegetation canopy surface, are produced from stereoscopic image pairs (stereo pairs) that have a variety of acquisition characteristics, and have been coupled with lidar data of forest structure and ground surface elevation to examine forest height. This work explores surface elevations from HRSI DSMs derived from two types of acquisitions in open canopy forests. We (1) apply an automated mass-production stereogrammetry workflow to along-track HRSI stereo pairs, (2) identify multiple spatially coincident DSMs whose stereo pairs were acquired under different solar geometry, (3) vertically co-register these DSMs using coincident spaceborne lidar footprints (from ICESat-GLAS) as reference, and(4) examine differences in surface elevations between the reference lidar and the co-registered HRSI DSMs associated with two general types of acquisitions (DSM types) from different sun elevation angles. We find that these DSM types, distinguished by sun elevation angle at the time of stereo pair acquisition, are associated with different surface elevations estimated from automated stereogrammetry in open canopy forests. For DSM values with corresponding reference ground surface elevation from spaceborne lidar footprints in open canopy northern Siberian Larix forests with slopes less than10, our results show that HRSI DSM acquired with sun elevation angles greater than 35deg and less than 25deg (during snow-free conditions) produced characteristic and consistently distinct distributions of elevation differences from reference lidar. The former include DSMs of near-ground surfaces with root mean square errors less than 0.68 m relative to lidar. The latter, particularly those with angles less than 10deg, show distributions with larger differences from lidar that are associated with open canopy forests whose vegetation surface elevations are captured. Terrain aspect did not have a strong effect on the distribution of vegetation surfaces. Using the two DSM types together, the distribution of DSM-differenced heights in forests (6.0 m, sigma = 1.4 m) was consistent with the distribution of plot-level mean tree heights (6.5m, sigma = 1.2 m). We conclude that the variation in sun elevation angle at time of stereo pair acquisition can create illumination conditions conducive for capturing elevations of surfaces either near the ground or associated with vegetation canopy. Knowledge of HRSI acquisition solar geometry and snow cover can be used to understand and combine stereogrammetric surface elevation estimates to co-register rand difference overlapping DSMs, providing a means to map forest height at fine scales, resolving the vertical structure of groups of trees from spaceborne platforms in open canopy forests.

Modification of Soil Temperature and Moisture Budgets by Snow Processes

NASA Astrophysics Data System (ADS)

Feng, X.; Houser, P.

2006-12-01

Snow cover significantly influences the land surface energy and surface moisture budgets. Snow thermally insulates the soil column from large and rapid temperature fluctuations, and snow melting provides an important source for surface runoff and soil moisture. Therefore, it is important to accurately understand and predict the energy and moisture exchange between surface and subsurface associated with snow accumulation and ablation. The objective of this study is to understand the impact of land surface model soil layering treatment on the realistic simulation of soil temperature and soil moisture. We seek to understand how many soil layers are required to fully take into account soil thermodynamic properties and hydrological process while also honoring efficient calculation and inexpensive computation? This work attempts to address this question using field measurements from the Cold Land Processes Field Experiment (CLPX). In addition, to gain a better understanding of surface heat and surface moisture transfer process between land surface and deep soil involved in snow processes, numerical simulations were performed at several Meso-Cell Study Areas (MSAs) of CLPX using the Center for Ocean-Land-Atmosphere (COLA) Simplified Version of the Simple Biosphere Model (SSiB). Measurements of soil temperature and soil moisture were analyzed at several CLPX sites with different vegetation and soil features. The monthly mean vertical profile of soil temperature during October 2002 to July 2003 at North Park Illinois River exhibits a large near surface variation (<5 cm), reveals a significant transition zone from 5 cm to 25 cm, and becomes uniform beyond 25cm. This result shows us that three soil layers are reasonable in solving the vertical variation of soil temperature at these study sites. With 6 soil layers, SSiB also captures the vertical variation of soil temperature during entire winter season, featuring with six soil layers, but the bare soil temperature is underestimated and root-zone soil temperature is overestimated during snow melting; which leads to overestimated temperature variations down to 20 cm. This is caused by extra heat loss from upper soil level and insufficient heat transport from the deep soil. Further work will need to verify if soil temperature displays similar vertical thermal structure for different vegetation and soil types during snow season. This study provides insight to the surface and subsurface thermodynamic and hydrological processes involved in snow modeling which is important for accurate snow simulation.

Validation of the ASTER Global Digital Elevation Model Version 2 over the conterminous United States

USGS Publications Warehouse

Gesch, Dean B.; Oimoen, Michael J.; Zhang, Zheng; Meyer, David J.; Danielson, Jeffrey J.

2012-01-01

The ASTER Global Digital Elevation Model Version 2 (GDEM v2) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009. The absolute vertical accuracy of GDEM v2 was calculated by comparison with more than 18,000 independent reference geodetic ground control points from the National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v2 is 8.68 meters. This compares with the RMSE of 9.34 meters for GDEM v1. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v2 mean error of -0.20 meters is a significant improvement over the GDEM v1 mean error of -3.69 meters. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover to examine the effects of cover types on measured errors. The GDEM v2 mean errors by land cover class verify that the presence of aboveground features (tree canopies and built structures) cause a positive elevation bias, as would be expected for an imaging system like ASTER. In open ground classes (little or no vegetation with significant aboveground height), GDEM v2 exhibits a negative bias on the order of 1 meter. GDEM v2 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v2 has elevations that are higher in the canopy than SRTM.

Plant Growth Research for Food Production: Development and Testing of Expandable Tuber Growth Module

NASA Technical Reports Server (NTRS)

Cordova, Brennan A.

2017-01-01

Controlled and reliable growth of a variety of vegetable crops is an important capability for manned deep space exploration systems for providing nutritional supplementation and psychological benefits to crew members. Because current systems have been limited to leafy vegetables that require minimal root space, a major goal for these systems is to increase their ability to grow new types of crops, including tuber plants and root vegetables that require a large root space. An expandable root zone module and housing was developed to integrate this capability into the Veggie growth system. The expandable module uses a waterproof, gas-permeable bag with a structure that allows for root space to increase vertically throughout the growth cycle to accommodate for expanding tuber growth, while minimizing the required media mass. Daikon radishes were chosen as an ideal tuber crop for their subterraneous tuber size and rapid growth cycle, and investigations were done to study expanding superabsorbent hydrogels as a potential growth media. These studies showed improved water retention, but restricted oxygen availability to roots with pure gel media. It was determined that these hydrogels could be integrated in lower proportions into standard soil to achieve media expansion and water retention desired. Using the constructed module prototype and ideal gel and soil media mixture, Daikon radishes were grown in the system to test the capability and success of the system through a full growth cycle.

Vertical structure use by the Stout Iguana (Cyclura pinguis) on Guana Island, BVI

USGS Publications Warehouse

Cheek, Christopher A.; Hlavaty, Shay; Perkins, Rebecca N.; Peyton, Mark A.; Ryan, Caitlin N.; Zavaleta, Jennifer C.; Boal, Clint W.; Perry, Gad

2013-01-01

The Stout Iguana (Cyclura pinguis) is a critically endangered species endemic to the Puerto Rico Bank and currently restricted to the British Virgin Islands (BVI). Our study on Guana Island, BVI, focused on vertical structure use. Based on previous incidental observations, we hypothesized that Stout Iguanas use vertical structures and that adults and juveniles use such structures differently. In October 2011, we documented movement and vertical structure use by adult (n = 4) and juvenile (n = 11) iguanas with tracking bobbins. We recorded structure types used, heights attained on structures, distances between structures, and structure sizes. We found that Stout Iguanas used vertical structure more than previously documented. Trees comprised a significantly greater (P < 0.001) proportion of structures used by juveniles than by adults, whereas rocks comprised the greatest proportion of structures used by adults. In addition to differential structure use, juveniles climbed significantly higher (2.4 vs. 0.9 m on average; P < 0.001) than adults. We found no difference in the diameter or distance between structures used by adults and juveniles. Our results suggest that vertical structure use may be an important habitat element for free-ranging juvenile Stout Iguanas. Habitat management that provides vertical structure may be advantageous for the conservation of this species.

Shade treatment affects structure and recovery of invasive C4 African grass Echinochloa pyramidalis.

PubMed

López Rosas, Hugo; Moreno-Casasola, Patricia; Espejel González, Verónica E

2015-03-01

Echinochloa pyramidalis (Lam.) Hitchc. & Chase is an African grass with C4 photosynthesis, high biomass production, and high vegetative propagation that is tolerant to grazing and able to grow in flooded and dry conditions. Thus, it is highly invasive in tropical freshwater marshes where it is intentionally planted by ranchers to increase cattle production. This invasion is reducing plant biodiversity by increasing the invader's aerial coverage, changing wetland hydrology and causing soil physicochemical changes such as vertical accretion. Reducing the dominance of this species and increasing the density of native wetland species is a difficult, expensive, and time-consuming process. We applied a series of disturbance treatments aimed at eliminating E. pyramidalis and recovering the native vegetation of a partially invaded freshwater marsh. Treatments included physical (cutting, soil disking, transplanting individuals of the key native species Sagittaria lancifolia subsp. media (Micheli) Bogin, and/or reducing light with shade mesh) and/or chemical (spraying Round-Up™ herbicide) disturbances. At the end of the experiment, four of the five treatments used were effective in increasing the cover and biomass of native species and reducing that of E. pyramidalis. The combination of these treatments should be used to generate a proposal for the restoration of tropical wetlands invaded by non-native grasses. A promising treatment is using soil disked to soften the soil and destroy belowground structures such as roots and rhizomes. This treatment would be more promising if combined with the use of shade cloth. If it is desirable not to impact the soil or if there is not enough budget to make an effort to include active restoration disking soil, the use of shade cloth will suffice, although the recovery of native vegetation will be slower.

Shade treatment affects structure and recovery of invasive C4 African grass Echinochloa pyramidalis

PubMed Central

López Rosas, Hugo; Moreno-Casasola, Patricia; Espejel González, Verónica E

2015-01-01

Echinochloa pyramidalis (Lam.) Hitchc. & Chase is an African grass with C4 photosynthesis, high biomass production, and high vegetative propagation that is tolerant to grazing and able to grow in flooded and dry conditions. Thus, it is highly invasive in tropical freshwater marshes where it is intentionally planted by ranchers to increase cattle production. This invasion is reducing plant biodiversity by increasing the invader's aerial coverage, changing wetland hydrology and causing soil physicochemical changes such as vertical accretion. Reducing the dominance of this species and increasing the density of native wetland species is a difficult, expensive, and time-consuming process. We applied a series of disturbance treatments aimed at eliminating E. pyramidalis and recovering the native vegetation of a partially invaded freshwater marsh. Treatments included physical (cutting, soil disking, transplanting individuals of the key native species Sagittaria lancifolia subsp. media (Micheli) Bogin, and/or reducing light with shade mesh) and/or chemical (spraying Round-Up™ herbicide) disturbances. At the end of the experiment, four of the five treatments used were effective in increasing the cover and biomass of native species and reducing that of E. pyramidalis. The combination of these treatments should be used to generate a proposal for the restoration of tropical wetlands invaded by non-native grasses. A promising treatment is using soil disked to soften the soil and destroy belowground structures such as roots and rhizomes. This treatment would be more promising if combined with the use of shade cloth. If it is desirable not to impact the soil or if there is not enough budget to make an effort to include active restoration disking soil, the use of shade cloth will suffice, although the recovery of native vegetation will be slower. PMID:25859337

Dimensions of landscape preferences from pairwise comparisons

Treesearch

F. González Bernaldez; F. Parra

1979-01-01

Analysis of landscape preferences allows the detection of major dimensions as:(1) the opposition between "natural and humanized", (comprising features like vegetation cover, cultivation, pattern of landscape elements, artifacts, excavations, etc.); (2) polarity "precision/ambiguity" (involving opposition between: predominance of straight, vertical...

The constructed catchment Chicken Creek as Critical Zone Observatory under transition

NASA Astrophysics Data System (ADS)

Gerwin, Werner; Schaaf, Wolfgang; Elmer, Michael; Hinz, Christoph

2014-05-01

The constructed catchment Chicken Creek was established in 2005 as an experimental landscape laboratory for ecosystem research. The 6 ha area with clearly defined horizontal as well as vertical boundary conditions was left for an unrestricted primary succession. All Critical Zone elements are represented at this site, which allows the study of most processes occurring at the interface of bio-, pedo-, geo- and hydrosphere. It provides outstanding opportunities for investigating interactions and feedbacks between different evolving compartments during ecosystem development. The catchment is extensively instrumented since 2005 in order to detect transition stages of the ecosystem. Data recorded with a high spatial and temporal resolution include hydrological, geomorphological, pedological, limnological as well as biological parameters. In contrast to other Critical Zone Observatories, this site offers the unique situation of an early stage ecosystem with highly dynamic system properties. The first years of development were characterized by a fast formation of geomorphological structures due to massive erosion processes at the initially non-vegetated surface. Hydrological processes led to the establishment of a local groundwater body within 5 years. In the following years the influence of biological structures like vegetation patterns gained an increasing importance. Feedbacks between developing vegetation and e.g. hydrological features became more and more dominant. As a result, different phases of ecosystem development could be distinguished until now. This observatory offers manifold possibilities to identify and disentangle complex interactions between Critical Zone processes in situ under natural conditions. The originally low complexity of the system is growing with time facilitating the identification of influences of newly developing structures on system functions. Thus, it is possible to study effects of small-scale processes on the whole system at the landscape scale. In addition, the highly dynamic initial system properties allow the observation of multifaceted changes of Critical Zone properties and functions within short periods of time. Chicken Creek could complement the existing network of Critical Zone Observatories which are usually established at ecosystems in a mature state.

Increasing of Urban Radiation due to Climate Change and Reduction Strategy using Vegetation

NASA Astrophysics Data System (ADS)

Park, C.; Lee, D.; Heo, H. K.; Ahn, S.

2017-12-01

Urban Heat Island (UHI) which means urban air temperature is higher than suburban area is one of the most important environmental issues in Urban. High density of buildings and high ratio of impervious surfaces increases the radiation fluxes in urban canopy. Furthermore, climate change is expected to make UHI even more seriously in the future. Increased irradiation and air temperature cause high amount of short wave and long wave radiation, respectively. This increases net radiation negatively affects heat condition of pedestrian. UHI threatens citizen's health by increasing violence and heat related diseases. For this reason, understanding how much urban radiation will increase in the future, and exploring radiation reduction strategies is important for reducing UHI. In this research, we aim to reveal how the radiation flux in the urban canyon will change as the climate change and determine how much of urban vegetation will be needed to cover this degradation. The study area is a commercial district in Seoul where highly populated area. Due to the high density of buildings and lack of urban vegetation, this area has a poor thermal condition in summer. In this research, we simulate the radiation flux on the ground using multi-layer urban canopy model. Unlike conventionally used urban canopy model to simulate radiation transfer using vertically single layer, the multi-layer model we used here, enables to consider the vertical heterogeneous of buildings and urban vegetation. As a result, net radiation of urban ground will be increase 2.1 W/m² in the 2050s and 2.7 W/m² in the 2100s. And to prevent the increase of radiation, it is revealed that the urban vegetation should by increased by 10%. This research will be valuable in establishing greening planning as a strategy to reduce UHI effect.

Using Lidar and Radar measurements to constrain predictions of forest ecosystem structure and function.

PubMed

Antonarakis, Alexander S; Saatchi, Sassan S; Chazdon, Robin L; Moorcroft, Paul R

2011-06-01

Insights into vegetation and aboveground biomass dynamics within terrestrial ecosystems have come almost exclusively from ground-based forest inventories that are limited in their spatial extent. Lidar and synthetic-aperture Radar are promising remote-sensing-based techniques for obtaining comprehensive measurements of forest structure at regional to global scales. In this study we investigate how Lidar-derived forest heights and Radar-derived aboveground biomass can be used to constrain the dynamics of the ED2 terrestrial biosphere model. Four-year simulations initialized with Lidar and Radar structure variables were compared against simulations initialized from forest-inventory data and output from a long-term potential-vegtation simulation. Both height and biomass initializations from Lidar and Radar measurements significantly improved the representation of forest structure within the model, eliminating the bias of too many large trees that arose in the potential-vegtation-initialized simulation. The Lidar and Radar initializations decreased the proportion of larger trees estimated by the potential vegetation by approximately 20-30%, matching the forest inventory. This resulted in improved predictions of ecosystem-scale carbon fluxes and structural dynamics compared to predictions from the potential-vegtation simulation. The Radar initialization produced biomass values that were 75% closer to the forest inventory, with Lidar initializations producing canopy height values closest to the forest inventory. Net primary production values for the Radar and Lidar initializations were around 6-8% closer to the forest inventory. Correcting the Lidar and Radar initializations for forest composition resulted in improved biomass and basal-area dynamics as well as leaf-area index. Correcting the Lidar and Radar initializations for forest composition and fine-scale structure by combining the remote-sensing measurements with ground-based inventory data further improved predictions, suggesting that further improvements of structural and carbon-flux metrics will also depend on obtaining reliable estimates of forest composition and accurate representation of the fine-scale vertical and horizontal structure of plant canopies.

Digital structural interpretation of mountain-scale photogrammetric 3D models (Kamnik Alps, Slovenia)

NASA Astrophysics Data System (ADS)

Dolžan, Erazem; Vrabec, Marko

2015-04-01

From the earliest days of geological science, mountainous terrains with their extreme topographic relief and sparse to non-existent vegetation were utilized to a great advantage for gaining 3D insight into geological structure. But whereas Alpine vistas may offer perfect panoramic views of geology, the steep mountain slopes and vertical cliffs make it very time-consuming and difficult (if not impossible) to acquire quantitative mapping data such as precisely georeferenced traces of geological boundaries and attitudes of structural planes. We faced this problem in mapping the central Kamnik Alps of northern Slovenia, which are built up from Mid to Late Triassic succession of carbonate rocks. Polyphase brittle tectonic evolution, monotonous lithology and the presence of temporally and spatially irregular facies boundary between bedded platform carbonates and massive reef limestones considerably complicate the structural interpretation of otherwise perfectly exposed, but hardly accessible massif. We used Agisoft Photoscan Structure-from-Motion photogrammetric software to process a series of overlapping high-resolution (~0.25 m ground resolution) vertical aerial photographs originally acquired by the Geodetic Authority of the Republic of Slovenia for surveying purposes, to derive very detailed 3D triangular mesh models of terrain and associated photographic textures. Phototextures are crucial for geological interpretation of the models as they provide additional levels of detail and lithological information which is not resolvable from geometrical mesh models alone. We then exported the models to Paradigm Gocad software to refine and optimize the meshing. Structural interpretation of the models, including mapping of traces and surfaces of faults and stratigraphic boundaries and determining dips of structural planes, was performed in MVE Move suite which offers a range of useful tools for digital mapping and interpretation. Photogrammetric model was complemented by georeferenced geological field data acquired along mountain trail transects, mainly using the MVE Field Move software application. In our experience, vertical aerophotos were sufficient to generate precise surface models in all but the steepest mountain cliffs. Therefore, using existing vertical photoimagery (where available) is a very cost-effective alternative to organizing shooting campaigns with rented aircraft. For handling reasonably large models (cca 3 x 3 km, up to 10 million triangles), a low-end computer workstation with mid-range professional 3D graphic card is sufficient. The biggest bottleneck is the photogrammetric processing step which is time-consuming (10s of hrs) and has large RAM requirements, although those can be offset by dividing models into smaller parts. The major problem with geological modeling software like Gocad or Move is that it at present does not handle well projecting of phototextures. Whereas Photoscan-generated orthophotos can be vertically projected onto mesh models, this results in unacceptable distortions and gaps in subvertical or overhanging parts of the mountain cliff models. A real 3D UV texture mapping method, such as implemented in Photoscan, would be required to realistically model such areas. This limitations notwithstanding, digital geological mapping of photogrammetric models of mountains is a very promising, cost- and time-effective method for rapid structural interpretation and mapping of barren mountainous terrains, particularly when it is complemented by field measurements and observations.

The influence of vegetation and relief heterogeneity on turbulent exchange of CO2 between land surface and the atmosphere

NASA Astrophysics Data System (ADS)

Mukhartova, Juliya; Levashova, Natalia; Volkova, Elena; Olchev, Alexander

2016-04-01

The possible effect of spatial heterogeneity of vegetation cover and relief on horizontal and vertical turbulent exchange of CO2 was described using a process-based two-dimensional (2D) turbulent exchange models (Mukhartova et al. 2015). As a key area for this modeling study the hilly territory situated at the boundary between broadleaf forest and steppe zones in European part of Russia (Tula region) was selected. The vegetation cover in the study region is represented by complex mosaic of crop areas, grasslands, pastures, mires and groves. The very heterogeneous vegetation cover and complex dissected relief make very difficult an adequate determining the local and regional CO2 fluxes using experimental methods only. The two-dimensional model based on solution of the Navier-Stokes and continuity equations using well-known one-and-a-half order (TKE) closure scheme is applied. For description of the plant canopy photosynthesis and respiration rates the model uses an aggregated approach based on the model of Ball et al (1987) in Leuning modification (1990, 1995), the Beer-Lambert equation for the description of solar radiation penetration within a plant canopy (Monsi, Saeki 1953), and also an algorithm describing the response of stomatal conductance of the leaves to incoming photosynthetically active radiation. All necessary input parameters describing the photosynthesis and respiration properties of different plants and soil types in the study region were measured in the field or taken from the literature. The system of differential equations in the model is numerically solved by the finite-difference method. It is assumed that the influence of ground surface heterogeneities at the upper boundary of computing domain is very low and the pressure excess can be therefore considered as zero. The concentration of CO2 at the upper boundary of computing domain is assumed to be equal to some background value. It is also assumed that all boundaries between different vegetation and land-use types are situated far enough from the domain boundaries. It enabled us to assume that near these boundaries the values of vertical and horizontal wind components are independent on x coordinate. To quantify the possible effects of relief and vegetation heterogeneity on CO2 fluxes the three transects crossing the study area were chosen. For each transect the 2D patterns of wind speed components, turbulent exchange coefficients, CO2 concentrations and fluxes were calculated. The modeled vertical CO2 fluxes were compared with the fluxes calculated without allowing for turbulent disturbances due to relief and vegetation heterogeneity. All modeling experiments were provided for different weather conditions. The results of modeling experiments for different transects under various meteorological conditions showed that relief and vegetation heterogeneity have a significant impact on CO2 fluxes within the atmospheric surface layer and their ignoring can results in uncertainties in flux estimations. This study was supported by the Russian Science Foundation (Grant 14-14-00956).

Persistence of triclopyr in Alaska subarctic environments

USDA-ARS?s Scientific Manuscript database

Field dissipation and vertical mobility of the butoxyethyl ester of triclopyr was assessed in two distinct geographic locations within the state of Alaska. Interior sites near Delta Junction included vegetated plots within highway rights-of-way (ROW) and Conservation Reserve Program (CRP) fields and...

Bird use of reforestation sites: Influence of location and vertical structure

USGS Publications Warehouse

Twedt, Daniel J.; Cooper, Robert

2005-01-01

In the Lower Mississippi Valley, more than 300,000 acres of agricultural land have been reforested in the last 10 years. Planning decisions on how and where to restore forest are complex and usually reflect landowner objectives. However, initial planning decisions may have a large influence on the value of restored stands for birds and other wildlife.Reforestation of small, isolated tracts will likely result in mature forests where reproductive output of breeding birds does not compensate for adult mortality (sink habitats). This may be due to factors such as lower reproductive success near edges (edge effects), insufficient area of habitat to attract colonizing birds (area effects), or restricted population mixing and mating opportunities because of limited dispersal among tracts (isolation effects).Conversely, reforestation adjacent to existing forest increases contiguous forest area and provides areas buffered from agricultural or urban habitats (interior forest core).Bottomland reforestation has historically focused on planting relatively slow-growing tree species, particularly oaks (Quercus spp.). Thus, restoration sites are often dominated by grasses and forbs for up to a decade after tree planting. Grassland birds are the first birds to colonize reforested sites. However, abundance and productivity of grassland birds is generally poor on sites associated with woody vegetation, such as sites adjacent to mature forest.As woody vegetation develops on reforested sites, birds preferring shrub-scrub habitat displace grassland species (Twedt et al. 2002) (fig. 1). Planting faster-growing trees compresses the time for colonization by shrub-scrub birds and the increased vertical stature of these trees attracts forest birds (Twedt and Portwood 1996). Additionally, planting next to existing mature forests creates transitional edges that reduce the detrimental effects of abrupt forest-agriculture interfaces.

Catchment-scale redistribution of lithogenic solutes and black carbon over three years following wildfire in the Jemez Mountains, New Mexico, USA

NASA Astrophysics Data System (ADS)

Pohlmann, M. A.; Root, R.; Abrell, L.; Schwartz, C. J.; Chorover, J.

2017-12-01

Wildfire represents a disturbance that is becoming more prevalent as climate shifts to hotter and drier conditions in the southwestern US. It has profound and potentially long-term effects on the physical, chemical and microbiological properties of soil, including immediate surface deposition of lithogenic elements and incompletely combusted organic matter (i.e., black carbon or BC) previously held in biomass. The long residence time of BC mitigates oxidative release of carbon to the atmosphere and thus has implications for long-term climate forcing. Immediately following the 2013 Thompson Ridge wildfire in the Jemez River Basin Critical Zone Observatory, we sampled 22 soil profiles across a zero order basin at finely resolved depth intervals to 40 cm. Samples were collected again 12 and 24 months following the fire to assess redistribution of solutes and BC in the two years following fire. Water extractable anions, cations and carbon were measured for each sample and maps were generated by geostatistical interpolation. Additionally, the benzene polycarboxylic acid (BPCA) molecular marker method was employed for a selection of samples to quantify and characterize the BC content of the existing soil organic carbon pool as a function of landscape position and time. The `pulsed' deposition of water-soluble ions and BC followed pre-fire vegetation structure as indicated by solution chemistry data for years one and two displaying elevated solute concentrations in surface depths proximal to dense vegetation. Vertical and lateral redistribution of the water extractable elements and BC were consistent with wetting front propagation and topographic trends (driven by erosion, overland flow and lateral subsurface flow). BC depth profiles indicate vertical infiltration and lateral transport with burial, the latter associated with surface erosion of sediment, as mechanisms for redistribution.

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.

1996-01-01

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography

NASA Technical Reports Server (NTRS)

Treuhaft, Robert N.

1996-01-01

Drawing from recently submitted work, this paper first gives a heuristic description of the sensitivity of interferometric synthetic aperture radar (INSAR) to vertical vegetation distribution and under laying surface topography. A parameter estimation scenario is then described in which the INSAR cross correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of INSAR observations for single baseline, single frequency, single incidence-angle, single polarization INSAR. Using ancillary ground truth data to compensate for the under determination of the parameters, forest depths are estimated from the INSAR data. A recently analyzed multi-baseline data set is also discussed and the potential for stand alone INSAR parameter estimation is assessed. The potential of combining the information content of INSAR with that of infrared/optical remote sensing data is briefly discussed.

Impacts of the Deepwater Horizon oil spill on the salt marsh vegetation of Louisiana.

PubMed

Hester, Mark W; Willis, Jonathan M; Rouhani, Shahrokh; Steinhoff, Marla A; Baker, Mary C

2016-09-01

The coastal wetland vegetation component of the Deepwater Horizon oil spill Natural Resource Damage Assessment documented significant injury to the plant production and health of Louisiana salt marshes exposed to oiling. Specifically, marsh sites experiencing trace or greater vertical oiling of plant tissues displayed reductions in cover and peak standing crop relative to reference (no oiling), particularly in the marsh edge zone, for the majority of this four year study. Similarly, elevated chlorosis of plant tissue, as estimated by a vegetation health index, was detected for marsh sites with trace or greater vertical oiling in the first two years of the study. Key environmental factors, such as hydrologic regime, elevation, and soil characteristics, were generally similar across plant oiling classes (including reference), indicating that the observed injury to plant production and health was the result of plant oiling and not potential differences in environmental setting. Although fewer significant impacts to plant production and health were detected in the latter years of the study, this is due in part to decreased sample size occurring as a result of erosion (shoreline retreat) and resultant loss of plots, and should not be misconstrued as indicating full recovery of the ecosystem. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

New Orleans, LA, District: Report of the Secretary of the Army on Civil Works Activities for FY 2011

DTIC Science & Technology

2011-01-01

side slopes, and protective vegetation. The sandfill berm slopes from an elevation of 8.5 feet, NGVD, at the toe of the dune 150 feet gulfward to an...and vegetated dune constructive with a geotextile tube core extending the length of Grand Isle’s gulf shore and a jetty to stabilize the western end...of the island at Caminada Pass. The dune has a 10-foot-wide crown at an elevation of 13.5 feet, National Geodetic Vertical Datum (NGVD), 1 on 5

Integration of ALS and TLS for calibration and validation of LAI profiles from large footprint lidar

NASA Astrophysics Data System (ADS)

Armston, J.; Tang, H.; Hancock, S.; Hofton, M. A.; Dubayah, R.; Duncanson, L.; Fatoyinbo, T. E.; Blair, J. B.; Disney, M.

2016-12-01

The Global Ecosystem Dynamics Investigation (GEDI) is designed to provide measurements of forest vertical structure and above-ground biomass density (AGBD) over tropical and temperate regions. The GEDI is a multi-beam waveform lidar that will acquire transects of forest canopy vertical profiles in conditions of up to 99% canopy cover. These are used to produce a number of canopy height and profile metrics to model habitat suitability and AGBD. These metrics include vertical leaf area index (LAI) profiles, which require some pre-launch refinement of large-footprint waveform processing methods for separating canopy and ground returns and estimation of their reflectance. Previous research developments in modelling canopy gap probability to derive canopy and ground reflectance from waveforms have primarily used data from small-footprint instruments, however development of a generalized spatial model with uncertainty will be useful for interpreting and modelling waveforms from large-footprint instruments such as the NASA Land Vegetation and Ice Sensor (LVIS) with a view to implementation for GEDI. Here we present an analysis of waveform lidar data from the NASA Land Vegetation and Ice Sensor (LVIS), which were acquired in Gabon in February 2016 to support the NASA/ESA AfriSAR campaign. AfriSAR presents a unique opportunity to test refined methods for retrieval of LAI profiles in high above-ground biomass rainforests (up to 600 Mg/ha) with dense canopies (>90% cover), where the greatest uncertainty exists. Airborne and Terrestrial Laser Scanning data (TLS) were also collected, enabling quantification of algorithm performance in plots of dense canopy cover. Refinement of canopy gap probability and LAI profile modelling from large-footprint lidar was based on solving for canopy and ground reflectance parameters spatially by penalized least-squares. The sensitivities of retrieved cover and LAI profiles to variation in canopy and ground reflectance showed improvement compared to assuming a constant ratio. We evaluated the use of spatially proximate simple waveforms to interpret more complex waveforms with poor separation of canopy and ground returns. This work has direct implications for GEDI algorithm refinement.

The application of remotely sensed data in support of emergency rehabilitation of wildfire-damage areas. [Bridge Creek fire area, Deschutes National Forest, Oregon

NASA Technical Reports Server (NTRS)

Isaacson, D. L.; Smith, H. G.; Alexander, C. J. (Principal Investigator)

1980-01-01

The depth, texture, and water holding capacity of the soil before the fire in the Bridge Creek area of Deschutes National Forest (1979) were determined from available aerial photography and LANDSAT MSS digital data. Three days after the fire was out, complete coverage of the burned area was acquired on 35 mm color infrared film from a near vertical or low oblique perspective. These photographs were used in assessing the condition of vegetation, and in predicting the likelihood of survival. Negatives from vertical natural photography obtained during the same flight were used to produce 3R prints from which large scale mosaics of the entire burned area were obtained. LANDSAT MSS data obtained on the day the fire was under control were used to evaluate vegetative vigor (by calculating a band 7/band 5 ratio value for each spectral class) and to determine the boundary between altered and unaltered land.

Quantifying Biomass and Bare Earth Changes from the Hayman Fire Using Multi-temporal Lidar

NASA Astrophysics Data System (ADS)

Stoker, J. M.; Kaufmann, M. R.; Greenlee, S. K.

2007-12-01

Small-footprint multiple-return lidar data collected in the Cheesman Lake property prior to the 2002 Hayman fire in Colorado provided an excellent opportunity to evaluate Lidar as a tool to predict and analyze fire effects on both soil erosion and overstory structure. Re-measuring this area and applying change detection techniques allowed for analyses at a high level of detail. Our primary objectives focused on the use of change detection techniques using multi-temporal lidar data to: (1) evaluate the effectiveness of change detection to identify and quantify areas of erosion or deposition caused by post-fire rain events and rehab activities; (2) identify and quantify areas of biomass loss or forest structure change due to the Hayman fire; and (3) examine effects of pre-fire fuels and vegetation structure derived from lidar data on patterns of burn severity. While we were successful in identifying areas where changes occurred, the original error bounds on the variation in actual elevations made it difficult, if not misleading to quantify volumes of material changed on a per pixel basis. In order to minimize these variations in the two datasets, we investigated several correction and co-registration methodologies. The lessons learned from this project highlight the need for a high level of flight planning and understanding of errors in a lidar dataset in order to correctly estimate and report quantities of vertical change. Directly measuring vertical change using only lidar without ancillary information can provide errors that could make quantifications confusing, especially in areas with steep slopes.

An update on remote measurement of soil moisture over vegetation using infrared temperature measurements: A FIFE perspective

NASA Technical Reports Server (NTRS)

Carlson, Toby N.

1988-01-01

Using model development, image analysis and micrometeorological measurements, the object is to push beyond the present limitations of using the infrared temperature method for remotely determining surface energy fluxes and soil moisture over vegetation. Model development consists of three aspects: (1) a more complex vegetation formulation which is more flexible and realistic; (2) a method for modeling the fluxes over patchy vegetation cover; and (3) a method for inferring a two-layer soil vertical moisture gradient from analyses of horizontal variations in surface temperatures. HAPEX and FIFE satellite data will be used along with aircraft thermal infrared and solar images as input for the models. To test the models, moisture availability and bulk canopy resistances will be calculated from data collected locally at the Rock Springs experimental field site and, eventually, from the FIFE project.

Effects of a large wildfire on vegetation structure in a variable fire mosaic.

PubMed

Foster, C N; Barton, P S; Robinson, N M; MacGregor, C I; Lindenmayer, D B

2017-12-01

Management guidelines for many fire-prone ecosystems highlight the importance of maintaining a variable mosaic of fire histories for biodiversity conservation. Managers are encouraged to aim for fire mosaics that are temporally and spatially dynamic, include all successional states of vegetation, and also include variation in the underlying "invisible mosaic" of past fire frequencies, severities, and fire return intervals. However, establishing and maintaining variable mosaics in contemporary landscapes is subject to many challenges, one of which is deciding how the fire mosaic should be managed following the occurrence of large, unplanned wildfires. A key consideration for this decision is the extent to which the effects of previous fire history on vegetation and habitats persist after major wildfires, but this topic has rarely been investigated empirically. In this study, we tested to what extent a large wildfire interacted with previous fire history to affect the structure of forest, woodland, and heath vegetation in Booderee National Park in southeastern Australia. In 2003, a summer wildfire burned 49.5% of the park, increasing the extent of recently burned vegetation (<10 yr post-fire) to more than 72% of the park area. We tracked the recovery of vegetation structure for nine years following the wildfire and found that the strength and persistence of fire effects differed substantially between vegetation types. Vegetation structure was modified by wildfire in forest, woodland, and heath vegetation, but among-site variability in vegetation structure was reduced only by severe fire in woodland vegetation. There also were persistent legacy effects of the previous fire regime on some attributes of vegetation structure including forest ground and understorey cover, and woodland midstorey and overstorey cover. For example, woodland midstorey cover was greater on sites with higher fire frequency, irrespective of the severity of the 2003 wildfire. Our results show that even after a large, severe wildfire, underlying fire histories can contribute substantially to variation in vegetation structure. This highlights the importance of ensuring that efforts to reinstate variation in vegetation fire age after large wildfires do not inadvertently reduce variation in vegetation structure generated by the underlying invisible mosaic. © 2017 by the Ecological Society of America.

Assessing the Performance of LVIS Waveform Lidar Topography and Canopy Structure Measurements in Gabon

NASA Astrophysics Data System (ADS)

Hofton, M. A.; Blair, J. B.; Rabine, D.; Brooks, C.; Cornejo, H.; Story, S.

2016-12-01

In February-March 2016, NASA's Land, Vegetation and Ice Sensor (LVIS) was used to image sub-canopy topography, canopy topography and structure at several sites in Gabon. Data were collected as part of the NASA and ESA Afrisar Campaign, a joint remote sensing mission involving multiple airborne and ground-based data collection activities that support the calibration and validation of future spaceborne missions, particularly GEDI, NISAR and BIOMASS, as well as other investigations. LVIS is a wide-swath, medium-footprint, waveform recording laser altimeter (lidar) sensor that can collect contiguous data within a 2 km-wide swath using 20m wide footprints from 10km altitude. For the Gabon deployment, the sensor was mounted in the NASA Langley King Air aircraft and flown at 8 km altitude over five, 70x15km-wide areas and along multiple country-wide transects. Data products include footprint-level canopy height, ground topography and canopy metrics, as well as vertically and horizontally-geolocated lidar return waveforms that enable end users to produce additional georeferenced data products as needed. We present a summary of the data products from the campaign, as well as a performance assessment of the ground and canopy structure data using available airborne and ground based data. Uses of the data include the simulation of GEDI-like data and the derivation of canopy height and profile metric algorithms for implementation in GEDI level2 products, as well as to improve our understanding of ground-finding errors in dense vegetation environments from waveform lidar.

Linking Vegetation Structure and Spider Diversity in Riparian and Adjacent Habitats in Two Rivers of Central Argentina: An Analysis at Two Conceptual Levels.

PubMed

Griotti, Mariana; Muñoz-Escobar, Christian; Ferretti, Nelson E

2017-08-01

The link between vegetation structure and spider diversity has been well explored in the literature. However, few studies have compared spider diversity and its response to vegetation at two conceptual levels: assemblage (species diversity) and ensemble (guild diversity). Because of this, we studied spider diversity in riparian and adjacent habitats of a river system from the Chacoan subregion in central Argentina and evaluated their linkage with vegetation structure at these two levels. To assess vegetation structure, we measured plant species richness and vegetation cover in the herb and shrub - tree layers. We collected spiders for over 6 months by using vacuum netting, sweep netting and pitfall traps. We collected 3,808 spiders belonging to 119 morphospecies, 24 families and 9 guilds. At spider assemblage level, SIMPROF analysis showed significant differences among studied habitats. At spider ensemble level, nevertheless, we found no significant differences among habitats. Concerning the linkage with vegetation structure, BIOENV test showed that spider diversity at either assemblage or ensemble level was not significantly correlated with the vegetation variables assessed. Our results indicated that spider diversity was not affected by vegetation structure. Hence, even though we found a pattern in spider assemblages among habitats, this could not be attributed to vegetation structure. In this study, we show that analyzing a community at two conceptual levels will be useful for recognizing different responses of spider communities to vegetation structure in diverse habitat types. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Attribution and Characterisation of Sclerophyll Forested Landscapes Over Large Areas

NASA Astrophysics Data System (ADS)

Jones, Simon; Soto-Berelov, Mariela; Suarez, Lola; Wilkes, Phil; Woodgate, Will; Haywood, Andrew

2016-06-01

This paper presents a methodology for the attribution and characterisation of Sclerophyll forested landscapes over large areas. First we define a set of woody vegetation data primitives (e.g. canopy cover, leaf area index (LAI), bole density, canopy height), which are then scaled-up using multiple remote sensing data sources to characterise and extract landscape woody vegetation features. The advantage of this approach is that vegetation landscape features can be described from composites of these data primitives. The proposed data primitives act as building blocks for the re-creation of past woody characterisation schemes as well as allowing for re-compilation to support present and future policy and management and decision making needs. Three main research sites were attributed; representative of different sclerophyll woody vegetated systems (Box Iron-bark forest; Mountain Ash forest; Mixed Species foothills forest). High resolution hyperspectral and full waveform LiDAR data was acquired over the three research sites. At the same time, land management agencies (Victorian Department of Environment, Land Water and Planning) and researchers (RMIT, CRC for Spatial Information and CSIRO) conducted fieldwork to collect structural and functional measurements of vegetation, using traditional forest mensuration transects and plots, terrestrial lidar scanning and high temporal resolution in-situ autonomous laser (VegNet) scanners. Results are presented of: 1) inter-comparisons of LAI estimations made using ground based hemispherical photography, LAI 2200 PCA, CI-110 and terrestrial and airborne laser scanners; 2) canopy height and vertical canopy complexity derived from airborne LiDAR validated using ground observations; and, 3) time-series characterisation of land cover features. 1. Accuracy targets for remotely sensed LAI products to match within ground based estimates are ± 0.5 LAI or a 20% maximum (CEOS/GCOS) with new aspirational targets of 5%). In this research we conducted a total of 67 ground-based method-to-method pairwise comparisons across 11 plots in five sites, incorporating the previously mentioned LAI methods. Out of the 67 comparisons, 29 had an RMSE ≥ 0.5 LAIe. This has important implications for the validation of remotely sensed products since ground based techniques themselves exhibit LAI variations greater than internationally recommended guidelines for satellite product accuracies. 2. Two methods of canopy height derivation are proposed and tested over a large area (4 Million Ha). 99th percentile maximum height achieved a RMSE of 6.6%, whilst 95th percentile dominant height a RMSE = 10.3%. Vertical canopy complexity (i.e. the number of forest layers of strata) was calculated as the local maxima of vegetation density within the LiDAR canopy profile and determined using a cubic spline smoothing of Pgap. This was then validated against in-situ and LiDAR observations of canopy strata with an RMSE 0.39 canopy layers. 3. Preliminary results are presented of landcover characterisation using LandTrendr analysis of Landsat LEDAPS data. kNN is then used to link these features to a dense network of 800 field plots sites.

Development of a coupled wave-flow-vegetation interaction model

USGS Publications Warehouse

Beudin, Alexis; Kalra, Tarandeep S.; Ganju, Neil K.; Warner, John C.

2017-01-01

Emergent and submerged vegetation can significantly affect coastal hydrodynamics. However, most deterministic numerical models do not take into account their influence on currents, waves, and turbulence. In this paper, we describe the implementation of a wave-flow-vegetation module into a Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system that includes a flow model (ROMS) and a wave model (SWAN), and illustrate various interacting processes using an idealized shallow basin application. The flow model has been modified to include plant posture-dependent three-dimensional drag, in-canopy wave-induced streaming, and production of turbulent kinetic energy and enstrophy to parameterize vertical mixing. The coupling framework has been updated to exchange vegetation-related variables between the flow model and the wave model to account for wave energy dissipation due to vegetation. This study i) demonstrates the validity of the plant posture-dependent drag parameterization against field measurements, ii) shows that the model is capable of reproducing the mean and turbulent flow field in the presence of vegetation as compared to various laboratory experiments, iii) provides insight into the flow-vegetation interaction through an analysis of the terms in the momentum balance, iv) describes the influence of a submerged vegetation patch on tidal currents and waves separately and combined, and v) proposes future directions for research and development.

Linking sediment structure, hydrological functioning and biogeochemical cycling in disturbed coastal saltmarshes and implications for vegetation development

NASA Astrophysics Data System (ADS)

Spencer, Kate; Harvey, Gemma; James, Tempest; Simon, Carr; Michelle, Morris

2014-05-01

Saltmarsh restoration undoubtedly provides environmental enhancement, with vegetation quickly re-establishing following the breach of sea walls and subsequent tidal inundation of previously defended areas. Yet evidence increasingly suggests that the restored saltmarshes do not have the same biological characteristics as their natural counterparts (Mossman et al. 2012) and this may be in part be due to physicochemical parameters at the site including anoxia and poor drainage. Hence, restored saltmarshes may not offer the range and quality of ecosystem services anticipated. These environments will have been 'disturbed' by previous land use and there is little understanding of the impacts of this disturbance on the wider hydrogeomorphic and biogeochemical functioning in restored saltmarshes and the implications for saltmarsh vegetation development. This study examines linkages between physical sediment characteristics, sediment structure (using X-ray microtomography), sub-surface hydrology (using pressure transducers and time series analysis), and sediment and porewater geochemistry (major and trace elements, major anions) in sediment cores collected from undisturbed saltmarshes and those restored by de-embankment. Sub-surface sediments in restored saltmarshes have lower organic matter content, lower moisture content and higher bulk density than undisturbed sites. Using X-ray tomography a clear horizon can be observed which separates relict agricultural soils at depth with less dense and structureless sediments deposited since de-embankment. Ratios of open to closed pore space suggest that while undisturbed saltmarshes have the highest porosity, restored saltmarshes have larger void spaces, but limited pore connectivity. Sub-surface hydrological response to tidal flooding was subdued in the restored compared to the undisturbed site, suggesting that porewater flow may be impeded. Time series analysis indicated that flow pathways differ in restored saltmarsh sediments with preferential horizontal flows. The undisturbed saltmarsh displayed typical vertical geochemical sediment profiles. However, in the restored sites total Fe and Mn are elevated at depth indicating an absence of diagenetic cycling, whilst porewater sulphate and nitrate increased at depth suggesting that vertical solute transport is impeded in restored sites. In surface sediments, though total Hg concentrations are similar, Hg methylation rates are significantly higher than in the undisturbed saltmarsh suggesting that surface anoxia and poor drainage may result in increased mobilization and bioavailability of Hg. These findings have implications for the wider biogeochemical ecosystem services offered by saltmarsh restoration and the water-logged, anoxic conditions produced are unsuitable for seedling germination and plant growth. This highlights the need for integrated understanding of physical and biogeochemical processes.

Multi-Scale Associations between Vegetation Cover and Woodland Bird Communities across a Large Agricultural Region

PubMed Central

Ikin, Karen; Barton, Philip S.; Stirnemann, Ingrid A.; Stein, John R.; Michael, Damian; Crane, Mason; Okada, Sachiko; Lindenmayer, David B.

2014-01-01

Improving biodiversity conservation in fragmented agricultural landscapes has become an important global issue. Vegetation at the patch and landscape-scale is important for species occupancy and diversity, yet few previous studies have explored multi-scale associations between vegetation and community assemblages. Here, we investigated how patch and landscape-scale vegetation cover structure woodland bird communities. We asked: (1) How is the bird community associated with the vegetation structure of woodland patches and the amount of vegetation cover in the surrounding landscape? (2) Do species of conservation concern respond to woodland vegetation structure and surrounding vegetation cover differently to other species in the community? And (3) Can the relationships between the bird community and the woodland vegetation structure and surrounding vegetation cover be explained by the ecological traits of the species comprising the bird community? We studied 103 woodland patches (0.5 - 53.8 ha) over two time periods across a large (6,800 km2) agricultural region in southeastern Australia. We found that both patch vegetation and surrounding woody vegetation cover were important for structuring the bird community, and that these relationships were consistent over time. In particular, the occurrence of mistletoe within the patches and high values of woody vegetation cover within 1,000 ha and 10,000 ha were important, especially for bird species of conservation concern. We found that the majority of these species displayed similar, positive responses to patch and landscape vegetation attributes. We also found that these relationships were related to the foraging and nesting traits of the bird community. Our findings suggest that management strategies to increase both remnant vegetation quality and the cover of surrounding woody vegetation in fragmented agricultural landscapes may lead to improved conservation of bird communities. PMID:24830684

Multi-scale associations between vegetation cover and woodland bird communities across a large agricultural region.

PubMed

Ikin, Karen; Barton, Philip S; Stirnemann, Ingrid A; Stein, John R; Michael, Damian; Crane, Mason; Okada, Sachiko; Lindenmayer, David B

2014-01-01

Improving biodiversity conservation in fragmented agricultural landscapes has become an important global issue. Vegetation at the patch and landscape-scale is important for species occupancy and diversity, yet few previous studies have explored multi-scale associations between vegetation and community assemblages. Here, we investigated how patch and landscape-scale vegetation cover structure woodland bird communities. We asked: (1) How is the bird community associated with the vegetation structure of woodland patches and the amount of vegetation cover in the surrounding landscape? (2) Do species of conservation concern respond to woodland vegetation structure and surrounding vegetation cover differently to other species in the community? And (3) Can the relationships between the bird community and the woodland vegetation structure and surrounding vegetation cover be explained by the ecological traits of the species comprising the bird community? We studied 103 woodland patches (0.5 - 53.8 ha) over two time periods across a large (6,800 km(2)) agricultural region in southeastern Australia. We found that both patch vegetation and surrounding woody vegetation cover were important for structuring the bird community, and that these relationships were consistent over time. In particular, the occurrence of mistletoe within the patches and high values of woody vegetation cover within 1,000 ha and 10,000 ha were important, especially for bird species of conservation concern. We found that the majority of these species displayed similar, positive responses to patch and landscape vegetation attributes. We also found that these relationships were related to the foraging and nesting traits of the bird community. Our findings suggest that management strategies to increase both remnant vegetation quality and the cover of surrounding woody vegetation in fragmented agricultural landscapes may lead to improved conservation of bird communities.

Surface ground contamination and soil vertical distribution of 137Cs around two underground nuclear explosion sites in the Asian Arctic, Russia.

PubMed

Ramzaev, Valery; Mishine, Arkady; Golikov, Vladislav; Brown, Justin Emrys; Strand, Per

2007-01-01

Vertical distributions of 137Cs have been determined in vegetation-soil cores obtained from 30 different locations around two underground nuclear explosion sites--"Crystal" (event year - 1974) and "Kraton-3" (event year - 1978) in the Republic of Sakha (Yakutia), Russia. In 2001-2002, background levels of 137Cs surface contamination densities on control forest plots varied from 0.73 to 0.97 kBq m(-2) with an average of 0.84+/-0.10 kBq m(-2) and a median of 0.82 kBq m(-2). 137Cs ground contamination densities at the "Crystal" site ranged from 1.3 to 64 kBq m(-2); the activity gradually decreased with distance from the borehole. For "Kraton-3", residual surface contamination density of radiocaesium varied drastically from 1.7 to 6900 kBq m(-2); maximal 137Cs depositions were found at a "decontaminated" plot. At all forest plots, radiocaesium activity decreased throughout the whole vertical soil profile. Vertical distributions of 137Cs in soil for the majority of the plots sampled (n=18) can be described using a simple exponential function. Despite the fact that more than 20 years have passed since the main fallout events, more than 80% of the total deposited activity was found in the first 5 cm of the vegetation-soil cores from most of the forested landscapes. The low annual temperatures, clay-rich soil type with neutral pH, and presence of thick lichen-moss carpet are the factors which may hinder 137Cs transport down the soil profile.

Maryland: La Plata

Atmospheric Science Data Center

2014-05-15

article title:  Tornado Cuts Through La Plata, Maryland     View Larger Image A category F4 tornado tore through La Plata, Maryland on April 28, 2002, killing 5 and ... illustrates the strip of flattened vegetation left by the tornado. The lower image was acquired by MISR's nadir (vertical-viewing) ...

A comparison of cover pole with standard vegetation monitoring methods

USDA-ARS?s Scientific Manuscript database

The ability of resource managers to make informed decisions regarding wildlife habitat could be improved with the use of existing datasets and the use of cost effective, standardized methods to simultaneously quantify vertical and horizontal cover. The objectives of this study were to (1) characteri...

Hydrologic scenarios for floodplain building in a vertically accreting, suspended sediment river

NASA Astrophysics Data System (ADS)

Alexander, J. S.; Scott, M. L.; Schmidt, J. C.

2006-12-01

Recent advances in dendrogeomorphology allow for precise age constraint on rates of floodplain building. We applied these techniques in our effort to evaluate the relative roles of flow regulation and invasive riparian vegetation in accelerating the rate of vertical accretion and channel narrowing of the dam-regulated upper Green River in Dinosaur National Monument, Colorado and Utah. Four large trenches were excavated into alluvial deposits that are now inundated by either common post-dam floods or rare post-dam high releases. We dated individual stratigraphic units using the recently developed stem-burial method (Friedman et al. 2005), as well as traditional cross-dating methods. These excavations indicate that episodic large floods with pre- dam recurrences of 5 to 10 years may vertically aggrade floodplains by up to 1.0 m. Smaller, more frequent, floods progressively create inset alluvial deposits that are subsequently colonized by native or non-native woody shrubs and trees. These lower elevation deposits serve as growing surfaces for both native and non- native riparian plants as well as stable platforms for deposition during occasional large post-dam floods that exceed the capacity of the dam's power plant. This style of floodplain building results in channel narrowing and loss of aquatic habitats. In the case of the upper Green River, the majority of channel narrowing occurred during two isolated events: (1) a rare basin-wide flood in late winter 1962, shortly before completion of Flaming Gorge Dam and (2) the largest post-dam bypass flood in 1983. Thick deposits of these ages occur in each trench, and this pattern correlates with the sequence of channel narrowing described by Allred and Schmidt (1999) 320 km downstream at the USGS gage near Green River, Utah. Our results suggest infrequent, controlled, high-magnitude dam releases may be an ineffective means of channel rejuvenation and vegetation control along vertically accreting, suspended sediment rivers. Where post-dam rivers are in a condition of sediment surplus, large floods may further isolate unwanted riparian vegetation from lower, more frequently disturbed hydrologic environments by increasing the elevation of the higher alluvial deposits.

Patterns of in-soil methane production and atmospheric emission among different land covers of a Lake Erie estuarine wetland

NASA Astrophysics Data System (ADS)

Rey Sanchez, C.; Morin, T. H.; Stefanik, K. C.; Angle, J.; Wrighton, K. C.; Bohrer, G.

2017-12-01

Wetland soils store a great amount of carbon, but also accumulate and emit methane (CH4), a powerful greenhouse gas. To better understand the vertical and horizontal spatial variability of CH4 emissions, we monitored production and fluxes of CH4 in Old Woman Creek, an estuarine wetland of Lake Erie, Ohio, during the growing seasons of 2015 and 2016. Our combined observation methods targeted three different scales: 1) the eddy covariance technique provided continuous high frequency observations integrated over a large spatial footprint; 2) monthly chamber measurements provided sparse point measurements of fluxes in four distinct land-cover types in the wetland: open water, emergent vegetation (Typha spp.), floating vegetation (Nelumbo spp.) and mud flats; and 3) in-situ porewater dialysis samplers, "peepers", provided vertical CH4 concentration data in the soil at the same locations and temporal time steps as the chambers. In addition, we studied gene transcripts to quantify methanogenesis activity along the vertical soil profile. Using integrated chamber and EC measurements, we found an average surface emission rate from Typha, the most abundant vegetated land cover, of 219.4 g CH4-C m-2 y-1, which was much higher than rates reported in similar emergent vegetation types in other wetlands. There was large spatial variation of flux rates, with mud flats having the highest rates of CH4 emission, followed by Nelumbo and Typha patches, and with open water having the lowest emissions. Within the soil column, we applied a numerical model to convert soil methane concentrations to emissions rates. We found that, contrary to current ideas of methane production, most methane was being produced in the well-oxygenated surface soils, probably in anoxic microsites within the oxic layer. Our metatranscriptomic data supported these findings, clearly showing nine times greater methanogenic activity in oxic surface soils relative to deeper anoxic soils. Combined, our results provide important insights for the representation of processes of methane production and consumption in models, which can largely affect the estimates of methane emission from wetlands.

Lidar aboveground vegetation biomass estimates in shrublands: Prediction, uncertainties and application to coarser scales

USGS Publications Warehouse

Li, Aihua; Dhakal, Shital; Glenn, Nancy F.; Spaete, Luke P.; Shinneman, Douglas; Pilliod, David S.; Arkle, Robert; McIlroy, Susan

2017-01-01

Our study objectives were to model the aboveground biomass in a xeric shrub-steppe landscape with airborne light detection and ranging (Lidar) and explore the uncertainty associated with the models we created. We incorporated vegetation vertical structure information obtained from Lidar with ground-measured biomass data, allowing us to scale shrub biomass from small field sites (1 m subplots and 1 ha plots) to a larger landscape. A series of airborne Lidar-derived vegetation metrics were trained and linked with the field-measured biomass in Random Forests (RF) regression models. A Stepwise Multiple Regression (SMR) model was also explored as a comparison. Our results demonstrated that the important predictors from Lidar-derived metrics had a strong correlation with field-measured biomass in the RF regression models with a pseudo R2 of 0.76 and RMSE of 125 g/m2 for shrub biomass and a pseudo R2 of 0.74 and RMSE of 141 g/m2 for total biomass, and a weak correlation with field-measured herbaceous biomass. The SMR results were similar but slightly better than RF, explaining 77–79% of the variance, with RMSE ranging from 120 to 129 g/m2 for shrub and total biomass, respectively. We further explored the computational efficiency and relative accuracies of using point cloud and raster Lidar metrics at different resolutions (1 m to 1 ha). Metrics derived from the Lidar point cloud processing led to improved biomass estimates at nearly all resolutions in comparison to raster-derived Lidar metrics. Only at 1 m were the results from the point cloud and raster products nearly equivalent. The best Lidar prediction models of biomass at the plot-level (1 ha) were achieved when Lidar metrics were derived from an average of fine resolution (1 m) metrics to minimize boundary effects and to smooth variability. Overall, both RF and SMR methods explained more than 74% of the variance in biomass, with the most important Lidar variables being associated with vegetation structure and statistical measures of this structure (e.g., standard deviation of height was a strong predictor of biomass). Using our model results, we developed spatially-explicit Lidar estimates of total and shrub biomass across our study site in the Great Basin, U.S.A., for monitoring and planning in this imperiled ecosystem.

14 CFR 25.519 - Jacking and tie-down provisions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... structure must be designed for a vertical load of 1.33 times the vertical static reaction at each jacking point acting singly and in combination with a horizontal load of 0.33 times the vertical static reaction...: (i) The airplane structure must be designed for a vertical load of 1.33 times the vertical reaction...

14 CFR 25.519 - Jacking and tie-down provisions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... structure must be designed for a vertical load of 1.33 times the vertical static reaction at each jacking point acting singly and in combination with a horizontal load of 0.33 times the vertical static reaction...: (i) The airplane structure must be designed for a vertical load of 1.33 times the vertical reaction...

14 CFR 25.519 - Jacking and tie-down provisions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... structure must be designed for a vertical load of 1.33 times the vertical static reaction at each jacking point acting singly and in combination with a horizontal load of 0.33 times the vertical static reaction...: (i) The airplane structure must be designed for a vertical load of 1.33 times the vertical reaction...

14 CFR 25.519 - Jacking and tie-down provisions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... structure must be designed for a vertical load of 1.33 times the vertical static reaction at each jacking point acting singly and in combination with a horizontal load of 0.33 times the vertical static reaction...: (i) The airplane structure must be designed for a vertical load of 1.33 times the vertical reaction...

14 CFR 25.519 - Jacking and tie-down provisions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... structure must be designed for a vertical load of 1.33 times the vertical static reaction at each jacking point acting singly and in combination with a horizontal load of 0.33 times the vertical static reaction...: (i) The airplane structure must be designed for a vertical load of 1.33 times the vertical reaction...

Analysing the influence of different street vegetation on traffic-induced particle dispersion using microscale simulations.

PubMed

Wania, Annett; Bruse, Michael; Blond, Nadège; Weber, Christiane

2012-02-01

Urban vegetation can be viewed as compensation to the environmental drawbacks of urbanisation. However, its ecosystem function is not well-known and, for urban planning, vegetation is mainly considered as an element of urban design. This article argues that planning practice needs to re-examine the impact of vegetation cover in the urban fabric given our evaluation of vegetation's effects on air quality, including the dispersion of traffic-induced particles at street level. Using the three-dimensional microclimate model ENVI-met®, we evaluate these effects regarding the height-to-width ratio of streets flanked by buildings and the vertical and horizontal density of street vegetation. Our results reveal vegetation's effect on particle dispersion through its influence on street ventilation. In general, vegetation was found to reduce wind speed, causing inhibition of canyon ventilation and, consequently, an increase in particle concentrations. Vegetation was also found to reduce wind speed at crown-height and to disrupt the flow field in close vicinity to the canopy. With increasing height-to-width ratio of street canyons, wind speed reduction increases and the disturbance of the flow impacts across a canyon's entire width. We also found that the effect is more pronounced in configurations with poor ventilation, such as the low wind speed, perpendicular inflow direction, and in deep canyons cases. Copyright © 2011 Elsevier Ltd. All rights reserved.

Relationships among vegetation structure, canopy composition, and avian richness patterns across an aspen-conifer forest gradient

Treesearch

Charles E. Swift; Kerri T. Vierling; Andrew T. Hudak; Lee A. Vierling

2017-01-01

Ecologists have a long-term interest in understanding the relative influence of vegetation composition and vegetation structure on avian diversity. LiDAR remote sensing is useful in studying local patterns of avian diversity because it characterizes fine-scale vegetation structure across broad extents. We used LiDAR, aerial and satellite imagery, and avian field data...

Impact of small-scale vegetation structure on tephra layer preservation

PubMed Central

Cutler, Nick A.; Shears, Olivia M.; Streeter, Richard T.; Dugmore, Andrew J.

2016-01-01

The factors that influence tephra layer taphonomy are poorly understood, but vegetation cover is likely to play a role in the preservation of terrestrial tephra deposits. The impact of vegetation on tephra layer preservation is important because: 1) the morphology of tephra layers could record key characteristics of past land surfaces and 2) vegetation-driven variability in tephra thickness could affect attempts to infer eruption and dispersion parameters. We investigated small- (metre-) scale interactions between vegetation and a thin (<10 cm), recent tephra layer. We conducted surveys of vegetation structure and tephra thickness at two locations which received a similar tephra deposit, but had contrasting vegetation cover (moss vs shrub). The tephra layer was thicker and less variable under shrub cover. Vegetation structure and layer thickness were correlated on the moss site but not under shrub cover, where the canopy reduced the influence of understory vegetation on layer morphology. Our results show that vegetation structure can influence tephra layer thickness on both small and medium (site) scales. These findings suggest that some tephra layers may carry a signal of past vegetation cover. They also have implications for the sampling effort required to reliably estimate the parameters of initial deposits. PMID:27845415

Assessing the carbon benefit of saltmarsh restoration

NASA Astrophysics Data System (ADS)

Taylor, Benjamin; Paterson, David; Hanley, Nicholas

2016-04-01

The quantification of carbon sequestration rates in coastal ecosystems is required to better realise their potential role in climate change mitigation. Through accurate valuation this service can be fully appreciated and perhaps help facilitate efforts to restore vulnerable ecosystems such as saltmarshes. Vegetated coastal ecosystems are suggested to account for approximately 50% of oceanic sedimentary carbon despite their 2% areal extent. Saltmarshes, conservatively estimated to store 430 ± 30 Tg C in surface sediment deposits, have experienced extensive decline in the recent past; through processes such as land use change and coastal squeeze. Saltmarsh habitats offer a range of services that benefit society and the natural world, making their conservation meaningful and beneficial. The associated costs of restoration projects could, in part, be subsidised through payment for ecosystem services, specifically Blue carbon. Additional storage is generated through the (re)vegetation of mudflat areas leading to an altered ecosystem state and function; providing similar benefits to natural saltmarsh areas. The Eden Estuary, Fife, Scotland has been a site of saltmarsh restoration since 2000; providing a temporal and spatial scale to evaluate these additional benefits. The study is being conducted to quantify the carbon benefit of restoration efforts and provide an insight into the evolution of this benefit through sites of different ages. Seasonal sediment deposition and settlement rates are measured across the estuary in: mudflat, young planted saltmarsh, old planted saltmarsh and extant high marsh areas. Carbon values being derived from loss on ignition organic content values. Samples are taken across a tidal cycle on a seasonal basis; providing data on tidal influence, vegetation condition effects and climatic factors on sedimentation and carbon sequestration rates. These data will inform on the annual characteristics of sedimentary processes in the estuary and be used in concert with further data of vertical accretion, vegetation structure and vegetation carbon storage; facilitating the estimation of the total additionality offered by restoration and so its potential value as a subsidy.

Do multiple fires interact to affect vegetation structure in temperate eucalypt forests?

PubMed

Haslem, Angie; Leonard, Steve W J; Bruce, Matthew J; Christie, Fiona; Holland, Greg J; Kelly, Luke T; MacHunter, Josephine; Bennett, Andrew F; Clarke, Michael F; York, Alan

2016-12-01

Fire plays an important role in structuring vegetation in fire-prone regions worldwide. Progress has been made towards documenting the effects of individual fire events and fire regimes on vegetation structure; less is known of how different fire history attributes (e.g., time since fire, fire frequency) interact to affect vegetation. Using the temperate eucalypt foothill forests of southeastern Australia as a case study system, we examine two hypotheses about such interactions: (1) post-fire vegetation succession (e.g., time-since-fire effects) is influenced by other fire regime attributes and (2) the severity of the most recent fire overrides the effect of preceding fires on vegetation structure. Empirical data on vegetation structure were collected from 540 sites distributed across central and eastern Victoria, Australia. Linear mixed models were used to examine these hypotheses and determine the relative influence of fire and environmental attributes on vegetation structure. Fire history measures, particularly time since fire, affected several vegetation attributes including ground and canopy strata; others such as low and sub-canopy vegetation were more strongly influenced by environmental characteristics like rainfall. There was little support for the hypothesis that post-fire succession is influenced by fire history attributes other than time since fire; only canopy regeneration was influenced by another variable (fire type, representing severity). Our capacity to detect an overriding effect of the severity of the most recent fire was limited by a consistently weak effect of preceding fires on vegetation structure. Overall, results suggest the primary way that fire affects vegetation structure in foothill forests is via attributes of the most recent fire, both its severity and time since its occurrence; other attributes of fire regimes (e.g., fire interval, frequency) have less influence. The strong effect of environmental drivers, such as rainfall and topography, on many structural features show that foothill forest vegetation is also influenced by factors outside human control. While fire is amenable to human management, results suggest that at broad scales, structural attributes of these forests are relatively resilient to the effects of current fire regimes. Nonetheless, the potential for more frequent severe fires at short intervals, associated with a changing climate and/or fire management, warrant further consideration. © 2016 by the Ecological Society of America.

Study on a Dynamic Vegetation Model for Simulating Land Surface Flux Exchanges at Lien-Hua-Chih Flux Observation Site in Taiwan

NASA Astrophysics Data System (ADS)

Yeh, T. Y.; Li, M. H.; Chen, Y. Y.; Ryder, J.; McGrath, M.; Otto, J.; Naudts, K.; Luyssaert, S.; MacBean, N.; Bastrikov, V.

2016-12-01

Dynamic vegetation model ORCHIDEE (Organizing Carbon and Hydrology In Dynamic EcosystEms) is a state of art land surface component of the IPSL (Institute Pierre Simon Laplace) Earth System Model. It has been used world-wide to investigate variations of water, carbon, and energy exchanges between the land surface and the atmosphere. In this study we assessed the applicability of using ORCHIDEE-CAN, a new feature with 3-D CANopy structure (Naudts et al., 2015; Ryder et al., 2016), to simulate surface fluxes measured at tower-based eddy covariance fluxes at the Lien-Hua-Chih experimental watershed in Taiwan. The atmospheric forcing including radiation, air temperature, wind speed, and the dynamics of vertical canopy structure for driving the model were obtained from the observations site. Suitable combinations of default plant function types were examined to meet in-situ observations of soil moisture and leaf area index from 2009 to 2013. The simulated top layer soil moisture was ranging from 0.1 to 0.4 and total leaf area was ranging from 2.2 to 4.4, respectively. A sensitivity analysis was performed to investigate the sensitive of model parameters and model skills of ORCHIDEE-CAN on capturing seasonal variations of surface fluxes. The most sensitive parameters were suggested and calibrated by an automatic data assimilation tool ORCHDAS (ORCHIDEE Data Assimilation Systems; http://orchidas.lsce.ipsl.fr/). Latent heat, sensible heat, and carbon fluxes simulated by the model were compared with long-term observations at the site. ORCHIDEE-CAN by making use of calibrated surface parameters was used to study variations of land-atmosphere interactions on a variety of temporal scale in associations with changes in both land and atmospheric conditions. Ref: Naudts, K., et al.,: A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes, Geoscientific Model Development, 8, 2035-2065, doi:10.5194/gmd-8-2035-2015,2015. Ryder, J., et al. : A multi-layer land surface energy budget model for implicit coupling with global atmospheric simulations, Geoscientific Model Development, 9, 223-245, doi:10.5194/gmd-9-223-2016, 2016.

Variability in vegetation effects on density and nesting success of grassland birds

USGS Publications Warehouse

Winter, Maiken; Johnson, Douglas H.; Shaffer, Jill A.

2005-01-01

The structure of vegetation in grassland systems, unlike that in forest systems, varies dramatically among years on the same sites, and among regions with similar vegetation. The role of this variation in vegetation structure on bird density and nesting success of grassland birds is poorly understood, primarily because few studies have included sufficiently large temporal and spatial scales to capture the variation in vegetation structure, bird density, or nesting success. To date, no large-scale study on grassland birds has been conducted to investigate whether grassland bird density and nesting success respond similarly to changes in vegetation structure. However, reliable management recommendations require investigations into the distribution and nesting success of grassland birds over larger temporal and spatial scales. In addition, studies need to examine whether bird density and nesting success respond similarly to changing environmental conditions. We investigated the effect of vegetation structure on the density and nesting success of 3 grassland-nesting birds: clay-colored sparrow (Spizella pallida), Savannah sparrow (Passerculus sandwichensis), and bobolink (Dolichonyx oryzivorus) in 3 regions of the northern tallgrass prairie in 1998-2001. Few vegetation features influenced the densities of our study species, and each species responded differently to those vegetation variables. We could identify only 1 variable that clearly influenced nesting success of 1 species: clay-colored sparrow nesting success increased with increasing percentage of nest cover from the surrounding vegetation. Because responses of avian density and nesting success to vegetation measures varied among regions, years, and species, land managers at all times need to provide grasslands with different types of vegetation structure. Management guidelines developed from small-scale, short-term studies may lead to misrepresentations of the needs of grassland-nesting birds.

Linking models and data on vegetation structure

NASA Astrophysics Data System (ADS)

Hurtt, G. C.; Fisk, J.; Thomas, R. Q.; Dubayah, R.; Moorcroft, P. R.; Shugart, H. H.

2010-06-01

For more than a century, scientists have recognized the importance of vegetation structure in understanding forest dynamics. Now future satellite missions such as Deformation, Ecosystem Structure, and Dynamics of Ice (DESDynI) hold the potential to provide unprecedented global data on vegetation structure needed to reduce uncertainties in terrestrial carbon dynamics. Here, we briefly review the uses of data on vegetation structure in ecosystem models, develop and analyze theoretical models to quantify model-data requirements, and describe recent progress using a mechanistic modeling approach utilizing a formal scaling method and data on vegetation structure to improve model predictions. Generally, both limited sampling and coarse resolution averaging lead to model initialization error, which in turn is propagated in subsequent model prediction uncertainty and error. In cases with representative sampling, sufficient resolution, and linear dynamics, errors in initialization tend to compensate at larger spatial scales. However, with inadequate sampling, overly coarse resolution data or models, and nonlinear dynamics, errors in initialization lead to prediction error. A robust model-data framework will require both models and data on vegetation structure sufficient to resolve important environmental gradients and tree-level heterogeneity in forest structure globally.

Spatial patterns in the effects of fire on savanna vegetation three-dimensional structure.

PubMed

Levick, Shaun R; Asner, Gregory P; Smit, Izak P J

2012-12-01

Spatial variability in the effects of fire on savanna vegetation structure is seldom considered in ecology, despite the inherent heterogeneity of savanna landscapes. Much has been learned about the effects of fire on vegetation structure from long-term field experiments, but these are often of limited spatial extent and do not encompass different hillslope catena elements. We mapped vegetation three-dimensional (3-D) structure over 21 000 ha in nine savanna landscapes (six on granite, three on basalt), each with contrasting long-term fire histories (higher and lower fire frequency), as defined from a combination of satellite imagery and 67 years of management records. Higher fire frequency areas contained less woody canopy cover than their lower fire frequency counterparts in all landscapes, and woody cover reduction increased linearly with increasing difference in fire frequency (r2 = 0.58, P = 0.004). Vegetation height displayed a more heterogeneous response to difference in fire frequency, with taller canopies present in the higher fire frequency areas of the wetter sites. Vegetation 3-D structural differences between areas of higher and lower fire frequency differed between geological substrates and varied spatially across hillslopes. Fire had the greatest relative impact on vegetation structure on nutrient-rich basalt substrates, and it imparted different structural responses upon vegetation in upland, midslope, and lowland topographic positions. These results highlight the complexity of fire vegetation relationships in savanna systems, and they suggest that underlying landscape heterogeneity needs more explicit incorporation into fire management policies.

Terrestrial laser scanning to quantify above-ground biomass of structurally complex coastal wetland vegetation

NASA Astrophysics Data System (ADS)

Owers, Christopher J.; Rogers, Kerrylee; Woodroffe, Colin D.

2018-05-01

Above-ground biomass represents a small yet significant contributor to carbon storage in coastal wetlands. Despite this, above-ground biomass is often poorly quantified, particularly in areas where vegetation structure is complex. Traditional methods for providing accurate estimates involve harvesting vegetation to develop mangrove allometric equations and quantify saltmarsh biomass in quadrats. However broad scale application of these methods may not capture structural variability in vegetation resulting in a loss of detail and estimates with considerable uncertainty. Terrestrial laser scanning (TLS) collects high resolution three-dimensional point clouds capable of providing detailed structural morphology of vegetation. This study demonstrates that TLS is a suitable non-destructive method for estimating biomass of structurally complex coastal wetland vegetation. We compare volumetric models, 3-D surface reconstruction and rasterised volume, and point cloud elevation histogram modelling techniques to estimate biomass. Our results show that current volumetric modelling approaches for estimating TLS-derived biomass are comparable to traditional mangrove allometrics and saltmarsh harvesting. However, volumetric modelling approaches oversimplify vegetation structure by under-utilising the large amount of structural information provided by the point cloud. The point cloud elevation histogram model presented in this study, as an alternative to volumetric modelling, utilises all of the information within the point cloud, as opposed to sub-sampling based on specific criteria. This method is simple but highly effective for both mangrove (r2 = 0.95) and saltmarsh (r2 > 0.92) vegetation. Our results provide evidence that application of TLS in coastal wetlands is an effective non-destructive method to accurately quantify biomass for structurally complex vegetation.

Homogenization of vegetation structure across residential neighborhoods: effects of climate, urban morphology, and socio-economics

EPA Science Inventory

Climate is a key driver regulating vegetation structure across rural ecosystems. In urban ecosystems, multiple interactions between humans and the environment can have homogenizing influences, confounding the relationship between vegetation structure and climate. In fact, vegetat...

Vertically aligned nanostructure scanning probe microscope tips

DOEpatents

Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

2006-12-19

Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

[Vertical distribution and community diversity of butterflies in Yaoluoping National Nature Reserve, Anhui, China].

PubMed

Wang, Song; Bao, Fang-yin; Mei, Bai-mao; Ding, Shi-chao

2009-09-01

By the methods of fixed point, line intercept, and random investigation, the vertical distribution and community diversity of butterflies in Yaoluoping National Nature Reserve were investigated from 2005 to 2008. A total of 3681 specimen were collected, belonging to 111 species, 69 genera, and 10 families, among which, Nymphalidae had the higher species number, individual's number, and diversity index than the other families. The butterflies in the study area were a mixture of Oriental and Palaearetic species, with the Oriental species diminished gradually and the Palaearetic components increased gradually with increasing altitude. Among the three vertical zones ( <800 m, 800-1200 m, and >1200 m in elevation), that of 800-1200 m had the most abundant species of butterflies; and among the six habitat types (deciduous broad-leaved forest, evergreen conifer forest, conifer-broad leaf mixed forest, bush and secondary forest, farmland, and residential area), bush and secondary forest had the higher species number, individual's number, and diversity index of butterflies, while farmland had the lowest diversity index. The similarity coefficient of butterfly species between the habitats was mainly dependent on vegetation type, i.e., the more the difference of vegetation type, the lesser the species similarity coefficient between the habitats, which was the highest (0.61) between conifer-broad leaf mixed forest and bush and secondary forest, and the lowest (0. 20) between evergreen conifer forest and bush and secondary forest.

Dynamics of volcanic ash remobilisation by wind through the Patagonian steppe after the eruption of Cordón Caulle, 2011

PubMed Central

Panebianco, Juan E.; Mendez, Mariano J.; Buschiazzo, Daniel E.; Bran, Donaldo; Gaitán, Juan J.

2017-01-01

Wind erosion of freshly-deposited volcanic ash causes persistent storms, strongly affecting ecosystems and human activity. Wind erosion of the volcanic ash was measured up to 17 months after the ash deposition, at 7 sites located within the ash-deposition area. The mass flux was measured up to 1.5 m above ground level. Mass transport rates were over 125 times the soil wind-erosion rates observed before the ash deposition, reaching up to 6.3 kg m−1 day−1. Total mass transport of ash during the 17 months ranged between 113.6 and 969.9 kg m−1 depending on topographic location and wind exposure. The vertical distribution of the mass flux at sites with higher vegetation cover was generally inverted as compared to sites with lower vegetation cover. This situation lasted 7 months and then a shift towards a more uniform vertical distribution was observed, in coincidence with the beginning of the decline of the mass transport rates. Decay rates differed between sites. Despite changes over time, an inverse linear correlation between the mass transports and the mass-flux gradients was found. Both the mass-flux gradients and the average mass-transport rates were not linked with shear-stress partition parameters, but with the ratio: ash-fall thickness to total vegetation cover. PMID:28349929

Dynamics of volcanic ash remobilisation by wind through the Patagonian steppe after the eruption of Cordón Caulle, 2011.

PubMed

Panebianco, Juan E; Mendez, Mariano J; Buschiazzo, Daniel E; Bran, Donaldo; Gaitán, Juan J

2017-03-28

Wind erosion of freshly-deposited volcanic ash causes persistent storms, strongly affecting ecosystems and human activity. Wind erosion of the volcanic ash was measured up to 17 months after the ash deposition, at 7 sites located within the ash-deposition area. The mass flux was measured up to 1.5 m above ground level. Mass transport rates were over 125 times the soil wind-erosion rates observed before the ash deposition, reaching up to 6.3 kg m -1 day -1 . Total mass transport of ash during the 17 months ranged between 113.6 and 969.9 kg m -1 depending on topographic location and wind exposure. The vertical distribution of the mass flux at sites with higher vegetation cover was generally inverted as compared to sites with lower vegetation cover. This situation lasted 7 months and then a shift towards a more uniform vertical distribution was observed, in coincidence with the beginning of the decline of the mass transport rates. Decay rates differed between sites. Despite changes over time, an inverse linear correlation between the mass transports and the mass-flux gradients was found. Both the mass-flux gradients and the average mass-transport rates were not linked with shear-stress partition parameters, but with the ratio: ash-fall thickness to total vegetation cover.

Vegetation Coverage Mapping and Soil Effect Correction in Estimating Vegetation Water Content and Dry Biomass from Satellites

NASA Astrophysics Data System (ADS)

Huang, J.; Chen, D.

2005-12-01

Vegetation water content (VWC) attracts great research interests in hydrology research in recent years. As an important parameter describing the horizontal expansion of vegetation, vegetation coverage is essential to implement soil effect correction for partially vegetated fields to estimate VWC accurately. Ground measurements of corn and soybeans in SMEX02 resulted in an identical expolinear relationship between vegetation coverage and leaf area index (LAI), which is used for vegetation coverage mapping. Results illustrated two parts of LAI growth quantitatively: the horizontal expansion of leaf coverage and the vertical accumulation of leaf layers. It is believed that the former part contributes significantly to LAI growth at initial vegetation growth stage and the latter is more dominant after vegetation coverage reaches a certain level. The Normalized Difference Water Index (NDWI) using short-wave infrared bands is convinced for its late saturation at high LAI values, in contrast to the Normalized Difference Vegetation Index (NDVI). NDWI is then utilized to estimate LAI, via another expolinear relationship, which is evidenced having vegetation species independency in study of corn and soybeans in SMEX02 sites. It is believed that the surface reflectance measured at satellites spectral bands are the mixed results of signals reflected from vegetation and bare soil, especially at partially vegetated fields. A simple linear mixture model utilizing vegetation coverage information is proposed to correct soil effect in such cases. Surface reflectance fractions for -rpure- vegetation are derived from the model. Comparing with ground measurements, empirical models using soil effect corrected vegetation indices to estimate VWC and dry biomass (DB) are generated. The study enhanced the in-depth understanding of the mechanisms how vegetation growth takes effect on satellites spectral reflectance with and without soil effect, which are particularly useful for modeling in hydrology, agriculture, forestry and meteorology etc.

Will fluctuations in salt marsh–mangrove dominance alter vulnerability of a subtropical wetland to sea‐level rise?

USGS Publications Warehouse

Mckee, Karen L.; Vervaeke, William

2018-01-01

To avoid submergence during sea-level rise, coastal wetlands build soil surfaces vertically through accumulation of inorganic sediment and organic matter. At climatic boundaries where mangroves are expanding and replacing salt marsh, wetland capacity to respond to sea-level rise may change. To compare how well mangroves and salt marshes accommodate sea-level rise, we conducted a manipulative field experiment in a subtropical plant community in the subsiding Mississippi River Delta. Experimental plots were established in spatially equivalent positions along creek banks in monospecific stands of Spartina alterniflora (smooth cordgrass) or Avicennia germinans (black mangrove) and in mixed stands containing both species. To examine the effect of disturbance on elevation dynamics, vegetation in half of the plots was subjected to freezing (mangrove) or wrack burial (salt marsh), which caused shoot mortality. Vertical soil development was monitored for 6 years with the surface elevation table-marker horizon system. Comparison of land movement with relative sea-level rise showed that this plant community was experiencing an elevation deficit (i.e., sea level was rising faster than the wetland was building vertically) and was relying on elevation capital (i.e., relative position in the tidal frame) to survive. Although Avicennia plots had more elevation capital, suggesting longer survival, than Spartina or mixed plots, vegetation type had no effect on rates of accretion, vertical movement in root and sub-root zones, or net elevation change. Thus, these salt marsh and mangrove assemblages were accreting sediment and building vertically at equivalent rates. Small-scale disturbance of the plant canopy also had no effect on elevation trajectories—contrary to work in peat-forming wetlands showing elevation responses to changes in plant productivity. The findings indicate that in this deltaic setting with strong physical influences controlling elevation (sediment accretion, subsidence), mangrove replacement of salt marsh, with or without disturbance, will not necessarily alter vulnerability to sea-level rise.

Retrieval of Vertical LAI Profiles Over Tropical Rain Forests using Waveform Lidar at La Selva, Costa Rica

NASA Technical Reports Server (NTRS)

Tang, Hao; Dubayah, Ralph; Swatantra, Anu; Hofton, Michelle; Sheldon, Sage; Clark, David B.; Blair, Bryan

2012-01-01

This study explores the potential of waveform lidar in mapping the vertical and spatial distributions of leaf area index (LAI) over the tropical rain forest of La Selva Biological Station in Costa Rica. Vertical profiles of LAI were derived at 0.3 m height intervals from the Laser Vegetation Imaging Sensor (LVIS) data using the Geometric Optical and Radiative Transfer (GORT) model. Cumulative LAI profiles obtained from LVIS were validated with data from 55 ground to canopy vertical transects using a modular field tower to destructively sample all vegetation. Our results showed moderate agreement between lidar and field derived LAI (r2=0.42, RMSE=1.91, bias=-0.32), which further improved when differences between lidar and tower footprint scales (r2=0.50, RMSE=1.79, bias=0.27) and distance of field tower from lidar footprint center (r2=0.63, RMSE=1.36, bias=0.0) were accounted for. Next, we mapped the spatial distribution of total LAI across the landscape and analyzed LAI variations over different land cover types. Mean values of total LAI were 1.74, 5.20, 5.41 and 5.62 over open pasture, secondary forests, regeneration forests after selective-logging and old-growth forests respectively. Lastly, we evaluated the sensitivities of our LAI retrieval model to variations in canopy/ground reflectance ratio and to waveform noise such as induced by topographic slopes. We found for both, that the effects were not significant for moderate LAI values (about 4). However model derivations of LAI might be inaccurate in areas of high-slope and high LAI (about 8) if ground return energies are low. This research suggests that large footprint waveform lidar can provide accurate vertical LAI profile estimates that do not saturate even at the high LAI levels in tropical rain forests and may be a useful tool for understanding the light transmittance within these canopies.

The Vertical Structure of Urban Soils and Their Convergence Across Cities

EPA Science Inventory

The theoretical patterns for vertical soil structure (e.g., A-B-C ordering of horizons) are a basis for research methods and our understanding of ecosystem structure and function in general. A general understanding of how urban soils differ from non-urban soils vertically is need...

A structural classification for inland northwest forest vegetation.

Treesearch

Kevin L. O' Hara; Penelope A. Latham; Paul Hessburg; Bradley G. Smith

1996-01-01

Existing approaches to vegetation classification range from those bassed on potential vegetation to others based on existing vegetation composition, or existing structural or physiognomic characteristics. Examples of these classifications are numerous, and in some cases, date back hundreds of years (Mueller-Dumbois and Ellenberg 1974). Small-scale or stand level...

Investigating error structure of shuttle radar topography mission elevation data product

NASA Astrophysics Data System (ADS)

Becek, Kazimierz

2008-08-01

An attempt was made to experimentally assess the instrumental component of error of the C-band SRTM (SRTM). This was achieved by comparing elevation data of 302 runways from airports all over the world with the shuttle radar topography mission data product (SRTM). It was found that the rms of the instrumental error is about +/-1.55 m. Modeling of the remaining SRTM error sources, including terrain relief and pixel size, shows that downsampling from 30 m to 90 m (1 to 3 arc-sec pixels) worsened SRTM vertical accuracy threefold. It is suspected that the proximity of large metallic objects is a source of large SRTM errors. The achieved error estimates allow a pixel-based accuracy assessment of the SRTM elevation data product to be constructed. Vegetation-induced errors were not considered in this work.

Inflatable Aeroponic System

NASA Technical Reports Server (NTRS)

Pelt, Jennifer Van

2005-01-01

Aeroponics Internationals (AI) innovation is a self-contained, self-supporting, flexible low mass aeroponic crop production unit with integral environmental systems for the control and delivery of a nutrient mist to the roots. This FLEX Aeroponic System model was developed for commercialization as a result of the NASA SBIR Phase I contract for the research and development of a low-mass, Inflatable Aeroponic System (IAS) for producing pesticide-free lettuces, grains, peppers, tomatoes and other vegetables. The innovation addresses the needs of water and nutrient delivery systems technologies for food production in space. The inflatable nature of the innovation makes it lightweight, allowing it to be deflated so it takes up less volume during transportation and storage. It improves upon AI's current aeroponic system design that uses more rigid structures and takes advantage of vertical inclines to increase bio-mass production by over 600%.

The Dual Role of Vegetation as a Constraint on Mass and Energy Flux into the Critical Zone and as an Emergent Property of Geophysical Critical Zone Structure

NASA Astrophysics Data System (ADS)

Brooks, P. D.; Swetnam, T. L.; Barnard, H. R.; Singha, K.; Harpold, A.; Litvak, M. E.

2017-12-01

Spatial patterns in vegetation long have been used to scale both landsurface-atmosphere exchanges of water and carbon as well as to infer subsurface structure. These pursuits typical proceed in isolation and rarely do inferences gained from one community propagate to related efforts in another. Perhaps more importantly, vegetation often is treated as an emergent property of landscape-climate interactions rather than an active modifier of both critical zone structure and energy fluxes. We posit that vegetation structure and activity are under utilized as a tool towards understanding landscape evolution and present examples that begin to disentangle the role of vegetation as both an emergent property and an active control on critical zone structure and function. As climate change, population growth, and land use changes threaten water resources worldwide, the need for the new insights vegetation can provide becomes not just a basic science priority, but a pressing applied science question with clear societal importance. This presentation will provide an overview of recent efforts to address the dual role of vegetation in both modifying and reflecting critical zone structure in the western North American forests. For example, interactions between topography and stand scale vegetation structure influence both solar radiation and turbulence altering landscape scale partitioning of evaporation vs transpiration with major impacts of surface water supply. Similarly, interactions between topographic shading, lateral redistribution of plant available water, and subsurface storage create a mosaic of drought resistance and resilience across complex terrain. These complex interactions between geophysical and vegetation components of critical zone structure result in predictable patterns in catchment scale hydrologic partitioning within individual watersheds while simultaneously suggesting testable hypotheses for why catchments under similar climate regimes respond so differently to drought stress.

Studying urban land-atmospheric interactions by coupling an urban canopy model with a single column atmospheric models

NASA Astrophysics Data System (ADS)

Song, J.; Wang, Z.

2013-12-01

Studying urban land-atmospheric interactions by coupling an urban canopy model with a single column atmospheric models Jiyun Song and Zhi-Hua Wang School of Sustainable Engineering and the Built Environment, Arizona State University, PO Box 875306, Tempe, AZ 85287-5306 Landuse landcover changes in urban area will modify surface energy budgets, turbulent fluxes as well as dynamic and thermodynamic structures of the overlying atmospheric boundary layer (ABL). In order to study urban land-atmospheric interactions, we coupled a single column atmospheric model (SCM) to a cutting-edge single layer urban canopy model (SLUCM). Modification of surface parameters such as the fraction of vegetation and engineered pavements, thermal properties of building and pavement materials, and geometrical features of street canyon, etc. in SLUCM dictates the evolution of surface balance of energy, water and momentum. The land surface states then provide lower boundary conditions to the overlying atmosphere, which in turn modulates the modification of ABL structure as well as vertical profiles of temperature, humidity, wind speed and tracer gases. The coupled SLUCM-SCM model is tested against field measurements of surface layer fluxes as well as profiles of temperature and humidity in the mixed layer under convective conditions. After model test, SLUCM-SCM is used to simulate the effect of changing urban land surface conditions on the evolution of ABL structure and dynamics. Simulation results show that despite the prescribed atmospheric forcing, land surface states impose significant impact on the physics of the overlying vertical atmospheric layer. Overall, this numerical framework provides a useful standalone modeling tool to assess the impacts of urban land surface conditions on the local hydrometeorology through land-atmospheric interactions. It also has potentially far-reaching implications to urban ecohydrological services for cities under future expansion and climate challenges.

Intercomparison of clumping index estimates from POLDER, MODIS, and MISR satellite data over reference sites

NASA Astrophysics Data System (ADS)

Pisek, Jan; Govind, Ajit; Arndt, Stefan K.; Hocking, Darren; Wardlaw, Timothy J.; Fang, Hongliang; Matteucci, Giorgio; Longdoz, Bernard

2015-03-01

Clumping index is the measure of foliage grouping relative to a random distribution of leaves in space. It is a key structural parameter of plant canopies that influences canopy radiation regimes and controls canopy photosynthesis and other land-atmosphere interactions. The Normalized Difference between Hotspot and Darkspot (NDHD) index has been previously used to retrieve global clumping index maps from POLarization and Directionality of the Earth's Reflectances (POLDER) data at ˜6 km resolution and the Bidirectional Reflectance Distribution Function (BRDF) product from Moderate Resolution Imaging Spectroradiometer (MODIS) at 500 m resolution. Most recently the algorithm was also applied with Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m resolution over selected areas. In this study for the first time we characterized and compared the three products over a set of sites representing diverse biomes and different canopy structures. The products were also directly validated with both in-situ vertical profiles and available seasonal trajectories of clumping index over several sites. We demonstrated that the vertical distribution of foliage and especially the effect of understory need to be taken into account while validating foliage clumping products from remote sensing products with values measured in the field. Satellite measurements responded to the structural effects near the top of canopies, while ground measurements may be biased by the lower vegetation layers. Additionally, caution should be taken regarding the misclassification in land cover maps as their errors can propagate into the foliage clumping maps. Our results indicate that MODIS data and MISR data, with 275 m in particular, can provide good quality clumping index estimates at spatial scales pertinent for modeling local carbon and energy fluxes.

Linking boundary-layer circulations and surface processes during FIFE89. Part 1: Observational analysis

NASA Technical Reports Server (NTRS)

Smith, Eric A.; Wai, Mickey M.-K.; Cooper, Harry J.; Rubes, Michael T.; Hsu, Ann

1994-01-01

Surface, aircraft, and satellite observations are analyzed for the 21-day 1989 intensive field campaign of the First ISLSCP Field Experiment (FIFE) to determine the effect of precipitation, vegetation, and soil moisture distributions on the thermal properties of the surface including the heat and moisture fluxes, and the corresponding response in the boundary-layer circulation. Mean and variance properties of the surface variables are first documented at various time and space scales. These calculations are designed to set the stage for Part 2, a modeling study that will focus on how time-space dependent rainfall distribution influences the intensity of the feedback between a vegetated surface and the atmospheric boundary layer. Further analysis shows strongly demarked vegetation and soil moisture gradients extending across the FIFE experimental site that were developed and maintained by the antecedent and ongoing spatial distribution of rainfall over the region. These gradients are shown to have a pronounced influence on the thermodynamic properties of the surface. Furthermore, perturbation surface wind analysis suggests for both short-term steady-state conditions and long-term averaged conditions that the gradient pattern maintained a diurnally oscillating local direct circulation with perturbation vertical velocities of the same order as developing cumulus clouds. Dynamical and scaling considerations suggest that the embedded perturbation circulation is driven by surface heating/cooling gradients and terrain ef fects rather than the manifestation of an inertial oscillation. The implication is that at even relatively small scales (less than 30 km), the differential evolution in vegetation density and soil moisture distribution over a relatively homogenous ecotone can give rise to preferential boundary-layer circulations capable of modifying local-scale horizontal and vertical motions.

Functional units and lead topologies: a hierarchical framework for observing and modeling the interplay of structures, storage dynamics and integral mass and energy flows in lower mesoscale catchments

NASA Astrophysics Data System (ADS)

Zehe, Erwin; Jackisch, Conrad; Blume, Theresa; Haßler, Sibylle; Allroggen, Niklas; Tronicke, Jens

2013-04-01

The CAOS Research Unit recently proposed a hierarchical classification scheme to subdivide a catchment into what we vaguely name classes of functional entities that puts the gradients driving mass and energy flows and their controls on top of the hierarchy and the arrangement of landscape attributes controlling flow resistances along these driving gradients (for instance soil types and apparent preferential pathways) at the second level. We name these functional entities lead topology classes, to highlight that they are characterized by a spatially ordered arrangement of landscape elements along a superordinate driving gradient. Our idea is that these lead topology classes have a distinct way how their structural and textural architecture controls the interplay of storage dynamics and integral response behavior that is typical for all members of a class, but is dissimilar between different classes. This implies that we might gain exemplary understanding of the typical dynamic behavior of the class, when thoroughly studying a few class members. We propose that the main integral catchment functions mass export and drainage, mass redistribution and storage, energy exchange with the atmosphere, as well as energy redistribution and storage - result from spatially organized interactions of processes within lead topologies that operate at different scale levels and partly dominate during different conditions. We distinguish: 1) Lead topologies controlling the land surface energy balance during radiation driven conditions at the plot/pedon scale level. In this case energy fluxes dominate and deplete a vertical temperature gradient that is build up by depleting a gradient in radiation fluxes. Water is a facilitator in this concert due to the high specific heat of vaporization. Slow vertical water fluxes in soil dominate, which are driven by vertical gradients in atmospheric water potential, chemical potential in the plant and in soil hydraulic potentials. 2) Lead topologies controlling fast drainage and generation stream flow during rainfall events at the hillslope scale level: Fast vertical and lateral mass fluxes dominate. They are driven by vertical and lateral gradients in pressure heads which build up by depleting the kinetic energy/velocity gradient of rainfall when it hits the ground or of vertical subsurface flows that "hit" a layer of low permeability. 3) Lead topologies controlling slow drainage and its supply, and thus creating memory at the catchment scale level: These are the groundwater system and the stream including the riparian zone. Permanent lateral water flows dominate that are driven by permanently active lateral gradients in pressure heads. Event scale stream flow generation and energy exchange with the atmospheric boundary layer are organized by the first two types of lead topologies, and their dominance changes with prevailing type of boundary conditions. We furthermore propose that lead topologies at the plot and the hillslope scale levels can be further subdivided into least functional entities we name call classes of elementary functional units. These classes of elementary functional units co-evolved being exposed to similar superordinate vertical gradients in a self-reinforcing manner. Being located either at the hilltop (sediment source area), midslope (sediment transport area) or hillfoot/riparian zone (sediment deposit area) they experienced similar weathering processes (past water, energy and nutrient flows), causing formation of similar soil texture in different horizons. This implies, depending on hillslope position and aspect, formation of distinct niches (with respect to water, nutrient and sun light availability) and thus "similar filters" to select distinct natural communities of animal and vegetation species. This in turn implies similarity with respect to formation of biotic flow networks (ant-, worm-, mole- and whole burrow systems, as well as root systems), which feeds back on vertical and lateral water/mass and thermal energy flows and so on. The idea is that members of EFU classes interact within lead topologies along a hierarchy of driving potential gradients and that these interactions are mediated by a hierarchy of connected flow networks like macropores, root networks or lateral pipe systems. We hypothesize that members of a functional unit class are similar with respect to the time invariant controls of the vertical gradients (soil hydraulic potentials, soil temperature, plant water potential) and the flow resistances in vertical direction (plant and soil albedo, soil hydraulic and thermal conductivity, vertical macropore networks). This implies that members of an EFU class behave functionally similar at least with respect to vertical flows of water and heat: we may gain exemplary understanding of the typical dynamic behavior of the class, by thoroughly studying a few class members. In the following we will thus use the term "elementary functional units, EFUs" and "elementary functional unit class, EFU class" as synonyms. We propose that a thorough understanding of the behavior of a few representatives of the most important EFU classes and of their interactions within a hierarchy of lead topology classes is sufficient for understanding and distributed modeling of event scale stream flow production under rainfall driven conditions and energy exchange with the atmosphere under radiation driven conditions. Good and not surprising news is that lead topologies controlling stream flow contribution, are an interconnected, ordered arrangement of the lead topologies that control energy exchange. We suggests that a combination of the related model approaches which simplified but physical based approaches to simulate dynamics in the saturated zone, riparian zone and the river network results in a structurally more adequate model framework for catchments of organized complexity. The feasibility of this concept is currently tested in the Attert catchment by setting up pseudo replica of field experiments and a distributed monitoring network in several members of first guess EFUs and superordinate lead topology classes. We combine geophysical and soil physical survey, artificial tracer tests and analysis of stable isotopes and ecological survey with distributed sensor clusters that permanently monitor meteorological variables, soil moisture and matric potential, piezometric heads etc. Within the proposed study we will present first results especially from the sensor clusters and geophysical survey. By using geostatistical methods we will work out to which extend members within a candidate EFU class are similar with respect to subsurface structures like depth to bedrock and soil properties as well as with respect to soil moisture/storage dynamics. Secondly, we will work out whether structurally similar hillslopes produce a similar event scale stream flow contribution, which of course is dependent on the degree of similarity of a) the rainfall forcing they receive and b) of their wetness state. To this end we will perform virtual experiments with the physically based model CATFLOW by perturbing behavioral model structures. These have been shown to portray system behavior and its architecture in a sense that they reproduce distributed observations of soil moisture and subsurface storm flow and represent the observed structural and textural signatures of soils, flow networks and vegetation.

A Methodology for Surface Soil Moisture and Vegetation Optical Depth Retrieval Using the Microwave Polarization Difference Index

NASA Technical Reports Server (NTRS)

Owe, Manfred; deJeu, Richard; Walker, Jeffrey; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz brightness temperature observations from the Scanning Multichannel Microwave Radiometer over several test sites in Illinois. Results using only nighttime data are presented at this time, due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a non-linear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness. Surface temperature is derived by a procedure using high frequency vertically polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and is totally independent of wavelength. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors.

The use of color infrared photography for wetlands mapping with special reference to shoreline and waterfowl habitat assessment

NASA Technical Reports Server (NTRS)

1973-01-01

Evaluation of low altitude oblique photography obtained by hand-held cameras was useful in determining specifications of operational mission requirements for conventional smaller-scaled vertical photography. Remote sensing techniques were used to assess the rapid destruction of marsh areas at Pointe Mouillee. In an estuarian environment where shoreline features change yearly, there is a need for revision in existing area maps. A land cover inventory, mapped from aerial photography, provided essential data necessary for determining adjacent lands suitable for marshland development. To quantitatively assess the wetlands environment, a detailed inventory of vegetative communities (19 categories) was made using color infrared photography and intensive ground truth. A carefully selected and well laid-out transect was found to be a key asset to photointerpretation and to the analysis of vegetative conditions. Transect data provided the interpreter with locally representative areas of various vegetative types. This facilitated development of a photointerpretation key. Additional information on vegetative conditions in the area was also obtained by evaluating the transect data.

Vegetative resistance to flow in South Florida; summary of vegetation sampling at sites NESRS3 and P33, Shark River slough, April 1996

USGS Publications Warehouse

Carter, Virginia; Ruhl, H.; Rybicki, N.B.; Reel, J.T.; Gammon, P.T.

1999-01-01

The U.S. Geological Survey is one of many agencies participating in the effort to restore the south Florida Everglades. We are sampling and characterizing the vegetation at selected sites in the Everglades as part of a study to quantify vegetative flow resistance. The objectives of the vegetative sampling are (1) to provide detailed information on species composition, vegetative characteristics, vegetative structure, and biomass for quantification of vegetative resistance to flow, and (2) to use this information to classify the vegetation and to improve existing vegetation maps for use with numerical models of surface-water flow. Vegetative sampling was conducted in the Shark River Slough in April, 1996. The data collected and presented here include live, dead, and periphyton biomass, vegetation characteristics and structure, and leaf area index.

Aboveground Biomass and Dynamics of Forest Attributes using LiDAR Data and Vegetation Model

NASA Astrophysics Data System (ADS)

V V L, P. A.

2015-12-01

In recent years, biomass estimation for tropical forests has received much attention because of the fact that regional biomass is considered to be a critical input to climate change. Biomass almost determines the potential carbon emission that could be released to the atmosphere due to deforestation or conservation to non-forest land use. Thus, accurate biomass estimation is necessary for better understating of deforestation impacts on global warming and environmental degradation. In this context, forest stand height inclusion in biomass estimation plays a major role in reducing the uncertainty in the estimation of biomass. The improvement in the accuracy in biomass shall also help in meeting the MRV objectives of REDD+. Along with the precise estimate of biomass, it is also important to emphasize the role of vegetation models that will most likely become an important tool for assessing the effects of climate change on potential vegetation dynamics and terrestrial carbon storage and for managing terrestrial ecosystem sustainability. Remote sensing is an efficient way to estimate forest parameters in large area, especially at regional scale where field data is limited. LIDAR (Light Detection And Ranging) provides accurate information on the vertical structure of forests. We estimated average tree canopy heights and AGB from GLAS waveform parameters by using a multi-regression linear model in forested area of Madhya Pradesh (area-3,08,245 km2), India. The derived heights from ICESat-GLAS were correlated with field measured tree canopy heights for 60 plots. Results have shown a significant correlation of R2= 74% for top canopy heights and R2= 57% for stand biomass. The total biomass estimation 320.17 Mt and canopy heights are generated by using random forest algorithm. These canopy heights and biomass maps were used in vegetation models to predict the changes biophysical/physiological characteristics of forest according to the changing climate. In our study we have used Dynamic Global Vegetation Model to understand the possible vegetation dynamics in the event of climate change. The vegetation represents a biogeographic regime. Simulations were carried out for 70 years time period. The model produced leaf area index and biomass for each plant functional type and biome for each grid in that region.

Supplement Analysis for the Transmission System Vegetation Management Program FEIS (DOE/EIS-0285/SA-62) - Rocky Reach - Maple Valley

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Mark A.

2002-04-16

Vegetation Management along the Rocky Reach – Maple Valley No. 1 Transmission Line ROW from structure 98/2 to structure 110/1. The transmission line is a 500 kV line. BPA proposes to clear targeted vegetation along access roads and around tower structures that may impede the operation and maintenance of the subject transmission line. BPA plans to conduct vegetation management along existing access road and around structure landings for the purpose of maintaining access to structures site. All work will be in accordance with the National Electrical Safety Code and BPA standards.

Relating vegetation condition to grazing management systems in the central Keiskamma catchment, Eastern Cape Province, South Africa

NASA Astrophysics Data System (ADS)

Kakembo, Vincent; Ndou, Naledzani

2017-04-01

An investigation of the temporal changes in vegetation condition across the communal villages of the central Keiskamma catchment, Eastern Cape Province, in relation to local grazing management systems was conducted. Landsat TM images of 1984 and 1999, in conjunction with SPOT imagery of 2011 were used to assess the spatial trends in vegetation. Information regarding the functionality of local grazing management structures was obtained through structured interviews. Vegetation condition was related to grazing management systems using the logistic regression in Idrisi Selva remote sensing software. Analysis of vegetation condition trends revealed a consistent deterioration of vegetation condition in villages with weak grazing management systems. A statistically significant correlation between vegetation condition and grazing management systems was identified. High levels of vegetation degradation were associated with villages that did not adhere to sound grazing management practices. The introduction of another layer governance in the form of elected municipal committees weakened traditional village management structures. Strengthening traditional management committees should be the point of departure for vegetation restoration.

Thermal remote sensing approach combined with field spectroscopy for detecting underground structures intended for defence and security purposes in Cyprus

NASA Astrophysics Data System (ADS)

Melillos, George; Themistocleous, Kyriacos; Hadjimitsis, Diofantos G.

2018-04-01

The purpose of this paper is to present the results obtained from unmanned aerial vehicle (UAV) using multispectral with thermal imaging sensors and field spectroscopy campaigns for detecting underground structures. Airborne thermal prospecting is based on the principle that there is a fundamental difference between the thermal characteristics of underground structures and the environment in which they are structure. This study aims to combine the flexibility and low cost of using an airborne drone with the accuracy of the registration of a thermal digital camera. This combination allows the use of thermal prospection for underground structures detection at low altitude with high-resolution information. In addition vegetation indices such as the Normalized Difference Vegetation Index (NDVI) and Simple Ratio (SR), were utilized for the development of a vegetation index-based procedure aiming at the detection of underground military structures by using existing vegetation indices or other in-band algorithms. The measurements were taken at the following test areas such as: (a) vegetation area covered with the vegetation (barley), in the presence of an underground military structure (b) vegetation area covered with the vegetation (barley), in the absence of an underground military structure. It is important to highlight that this research is undertaken at the ERATOSTHENES Research Centre which received funding to be transformed to an EXcellence Research Centre for Earth SurveiLlance and Space-Based MonItoring Of the EnviRonment (Excelsior) from the HORIZON 2020 Widespread-04-2017: Teaming Phase 1(Grant agreement no: 763643).

Dispersion and Deposition of Fine Particulates, Heavy Metals and Nitrogen in Urban Landscapes

NASA Astrophysics Data System (ADS)

Whitlow, T. H.; Tong, Z.

2015-12-01

Cities are characterized by networks of heavily trafficked roads, abrupt environmental gradients and local sources of airborne pollutants. Because urban dwellers are inevitably in close proximity to near ground pollution, there has been recent interest in using trees and green roofs to reduce human exposure yet there have been few empirical studies documenting the effect of vegetation and spatial heterogeneity on pollution concentration, human exposure and food safety. In this paper we describe the results of 2 studies in the New York metropolitan area. The first describes the effect of roadside trees on the concentration of fine particulates downwind of a major highway. The second examines vertical attenuation of fine particulates between street level and a rooftop vegetable farm and the deposition of nitrogen and heavy metals to vegetables and soil on the roof.

Ground-Vegetation Clutter Affects Phyllostomid Bat Assemblage Structure in Lowland Amazonian Forest.

PubMed

Marciente, Rodrigo; Bobrowiec, Paulo Estefano D; Magnusson, William E

2015-01-01

Vegetation clutter is a limiting factor for bats that forage near ground level, and may determine the distribution of species and guilds. However, many studies that evaluated the effects of vegetation clutter on bats have used qualitative descriptions rather than direct measurements of vegetation density. Moreover, few studies have evaluated the effect of vegetation clutter on a regional scale. Here, we evaluate the influence of the physical obstruction of vegetation on phyllostomid-bat assemblages along a 520 km transect in continuous Amazonian forest. We sampled bats using mist nets in eight localities during 80 nights (3840 net-hours) and estimated the ground-vegetation density with digital photographs. The total number of species, number of animalivorous species, total number of frugivorous species, number of understory frugivorous species, and abundance of canopy frugivorous bats were negatively associated with vegetation clutter. The bat assemblages showed a nested structure in relation to degree of clutter, with animalivorous and understory frugivorous bats distributed throughout the vegetation-clutter gradient, while canopy frugivores were restricted to sites with more open vegetation. The species distribution along the gradient of vegetation clutter was not closely associated with wing morphology, but aspect ratio and wing load differed between frugivores and animalivores. Vegetation structure plays an important role in structuring assemblages of the bats at the regional scale by increasing beta diversity between sites. Differences in foraging strategy and diet of the guilds seem to have contributed more to the spatial distribution of bats than the wing characteristics of the species alone.

Definitions and codes for seral status and structure of vegetation.

Treesearch

Frederick C. Hall; Larry Bryant; Rod Clausnitzer; Kathy Geier-Hayes; Robert Keane; Jane Kertis; Ayn Shlisky; Robert Steel

1995-01-01

Definitions and codes for identifying vegetation seral status and structure are desired for land management planning, appraising wildlife habitat, and prescribing vegetation treatment. Codes are only presented; they are not a system for determining seral status or stand structure. Terms defined are climax, potential natural community (PNC), succession, seral status,...

Novel characterization of landscape-level variability in historical vegetation structure

Treesearch

Brandon M. Collins; Jamie M. Lydersen; Richard G. Everett; Danny L. Fry; Scott L. Stephens

2015-01-01

We analyzed historical timber inventory data collected systematically across a large mixed-conifer-dominated landscape to gain insight into the interaction between disturbances and vegetation structure and composition prior to 20th century land management practices. Using records from over 20 000 trees, we quantified historical vegetation structure and composition for...

Understanding patterns of vegetation structure and distribution across Great Smoky Mountains National Park using LiDAR and meteorology data

NASA Astrophysics Data System (ADS)

Kumar, J.; Hargrove, W. W.; Norman, S. P.; Hoffman, F. M.

2017-12-01

Great Smoky Mountains National Park (GSMNP) in Tennessee is a biodiversity hotspot and home to a large number of plant, animal and bird species. Driven by gradients of climate (ex. temperature, precipitation regimes), topography (ex. elevation, slope, aspect), geology (ex. soil types, textures, depth), hydrology (ex. drainage, moisture availability) etc. GSMNP offers a diverse composition and distribution of vegetation which in turn supports an array of wildlife. Understanding the vegetation canopy structure is critical to understand, monitor and manage the complex forest ecosystems like the Great Smoky Mountain National Park (GSMNP). Vegetation canopies not only help understand the vegetation, but are also a critically important habitat characteristics of many threatened and endangered animal and bird species that GSMNP is home to. Using airborne Light Detection and Ranging (LiDAR) we characterize the three-dimensional structure of the vegetation. LiDAR based analysis gives detailed insight in the canopy structure (overstory and understory) and its spatial variability within and across forest types. Vegetation structure and spatial distribution show strong correlation with climate, topographic, and edaphic variables and our multivariate analysis not just mines rich and large LiDAR data but presents ecological insights and data for vegetation within the park that can be useful to forest managers in their management and conservation efforts.

Novel characterization of landscape-level variability in historical vegetation structure.

PubMed

Collins, Brandon M; Lydersen, Jamie M; Everett, Richard G; Fry, Danny L; Stephens, Scott L

2015-07-01

We analyzed historical timber inventory data collected systematically across a large mixed-conifer-dominated landscape to gain insight into the interaction between disturbances and vegetation structure and composition prior to 20th century land management practices. Using records from over 20 000 trees, we quantified historical vegetation structure and composition for nine distinct vegetation groups. Our findings highlight some key aspects of forest structure under an intact disturbance regime: (1) forests were low density, with mean live basal area and tree density ranging from 8-30 m2 /ha and 25-79 trees/ha, respectively; (2) understory and overstory structure and composition varied considerably across the landscape; and (3) elevational gradients largely explained variability in forest structure over the landscape. Furthermore, the presence of large trees across most of the surveyed area suggests that extensive stand-replacing disturbances were rare in these forests. The vegetation structure and composition characteristics we quantified, along with evidence of largely elevational control on these characteristics, can provide guidance for restoration efforts in similar forests.

Chapter 8 - Mapping existing vegetation composition and structure for the LANDFIRE Prototype Project

Treesearch

Zhiliang Zhu; James Vogelmann; Donald Ohlen; Jay Kost; Xuexia Chen; Brian Tolk

2006-01-01

The Landscape Fire and Resource Management Planning Tools Prototype Project, or LANDFIRE Prototype Project, required the mapping of existing vegetation composition (cover type) and structural stages at a 30-m spatial resolution to provide baseline vegetation data for the development of wildland fuel maps and for comparison to simulated historical vegetation reference...

Vertical structures in vibrated wormlike micellar solutions

NASA Astrophysics Data System (ADS)

Epstein, Tamir; Deegan, Robert

2008-11-01

Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.

Vegetative resistance to flow in south Florida; summary of vegetation sampling at sites NESRS3 and P33, Shark River slough, November, 1996

USGS Publications Warehouse

Carter, Virginia; Reel, J.T.; Rybicki, N.B.; Ruhl, H.; Gammon, P.T.; Lee, J.K.

1999-01-01

The U.S. Geological Survey is one of many agencies participating in the effort to restore the South Florida Everglades. We are sampling and characterizing the vegetation at selected sites in the Everglades as part of a study to quantify vegetative flow resistance. The objectives of the vegetation sampling are (1) to provide detailed information on species composition, vegetation characteristics, vegetation structure, and biomass for quantification of vegetative resistance to flow, and (2) to use this information to classify the vegetation and to improve existing vegetation maps for use with numerical models of surface-water flow. Vegetation was sampled at two sites in the Shark River Slough in November, 1996. The data collected and presented here include those for live and dead standing sawgrass, other dead material, periphyton biomass, vegetation characteristics and structure, and leaf area index.

Impacts of Seed Dispersal on Future Vegetation Structure under Changing Climates

NASA Astrophysics Data System (ADS)

Lee, E.; Schlosser, C. A.; Gao, X.; Prinn, R. G.

2011-12-01

As the impacts between land cover change, future climates and ecosystems are expected to be substantial, there are growing needs for improving the capability of simulating the global vegetation structure and landscape as realistically as possible. Current DGVMs assume ubiquitous availability of seeds and do not consider any seed dispersal mechanisms in plant migration process, which may influence the assessment of impacts to the ecosystem that rely on the vegetation structure changes (i.e., change in albedo, runoff, and terrestrial carbon sequestration capacity). This study incorporates time-varying wind-driven seed dispersal (i.e., the SEED configuration) as a dynamic constraint to the migration process of natural vegetation in the Community Land Model (CLM)-DGVM. The SEED configuration is validated using a satellite-derived tree cover dataset. Then the configuration is applied to project future vegetation structures and their implications for carbon fluxes, albedo, and hydrology under two climate mitigation scenarios (No-policy vs. 450ppm CO2 stabilization) for the 21st century. Our results show that regional changes of vegetation structure under changing climates are expected to be significant. For example, Alaska and Siberia are expected to experience substantial shifts of forestry structure, characterized by expansion of needle-leaf boreal forest and shrinkage of C3 grass Arctic. A suggested vulnerability assessment shows that vegetation structures in Alaska, Greenland, Central America, southern South America, East Africa and East Asia are susceptible to changing climates, regardless of the two climate mitigation scenarios. Regions such as Greenland, Tibet, South Asia and Northern Australia, however, may substantially alleviate their risks of rapid change in vegetation structure, given a robust greenhouse gas stabilization target. Proliferation of boreal forests in the high latitudes is expected to amplify the warming trend (i.e., a positive feedback to climate), if no mitigation policy is implemented. In contrast, under the 450ppm scenario, vegetation structure may buffer the warming trend, which is a negative feedback to climate. Moreover, runoff changes due to vegetation shifts may offset or complement runoff changes under anthropogenic climate warming.

Braided fluvial sedimentation in the lower paleozoic cape basin, South Africa

NASA Astrophysics Data System (ADS)

Vos, Richard G.; Tankard, Anthony J.

1981-07-01

Lower Paleozoic braided stream deposits from the Piekenier Formation in the Cape Province, South Africa, provide information on lateral and vertical facies variability in an alluvial plain complex influenced by a moderate to high runoff. Four braided stream facies are recognized on the basis of distinct lithologies and assemblages of sedimentary structures. A lower facies, dominated by upward-fining conglomerate to sandstone and mudstone channel fill sequences, is interpreted as a middle to lower alluvial plain deposit with significant suspended load sedimentation in areas of moderate to low gradients. These deposits are succeeded by longitudinal conglomerate bars which are attributed to middle to upper alluvial plain sedimentation with steeper gradients. This facies is in turn overlain by braid bar complexes of large-scale transverse to linguoid dunes consisting of coarse-grained pebbly sandstones with conglomerate lenses. These bar complexes are compared with environments of the Recent Platte River. They represent a middle to lower alluvial plain facies with moderate gradients and no significant suspended load sedimentation or vegetation to stabilize channels. These bar complexes interfinger basinward with plane bedded medium to coarse-grained sandstones interpreted as sheet flood deposits over the distal portions of an alluvial plain with low gradients and lacking fine-grained detritus or vegetation.

Chapter 4. Monitoring vegetation composition and structure as habitat attributes

Treesearch

Thomas E. DeMeo; Mary M. Manning; Mary M. Rowland; Christina D. Vojta; Kevin S. McKelvey; C. Kenneth Brewer; Rebecca S.H. Kennedy; Paul A. Maus; Bethany Schulz; James A. Westfall; Timothy J. Mersmann

2013-01-01

Vegetation composition and structure are key components of wildlife habitat (Mc- Comb et al. 2010, Morrison et al. 2006) and are, therefore, essential components of all wildlife habitat monitoring. The objectives of this chapter are to describe common habitat attributes derived from vegetation composition and structure and to provide guidance for obtaining and using...

The transformation of vegetation vertical zonality affected by anthropogenic impact in East Fennoscandia (Russia)

NASA Astrophysics Data System (ADS)

Sidorik, Vadim; Miulgauzen, Daria

2017-04-01

Ecosystems of East Fennoscandia have been affected by intensive anthropogenic influence that resulted in their significant transformation. Study of ecosystems in the framework of vegetation vertical zonality disturbance as well as its recovery allows to understand the trends of anthropogenically induced changes. The aim of the present research is the comparative analysis of vegetation vertical zonality of the two uplands in East Fennoscandia which may be considered as unaffected and affected by anthropogenic impact. The objects of key studies carried out in the north-west of Kola Peninsula in the vicinity of the Pechenganikel Mining and Metallurgical Plant are represented by ecosystems of Kalkupya (h 357 m) and Hangaslachdenvara (h 284 m) uplands. They are characterized by the similarity in sequence of altitudinal belts due to the position on the northern taiga - forest-tundra boundary. Plant communities of Kalkupya upland have no visible signs of anthropogenic influence, therefore, they can be considered as model ecosystems of the area. The sequence of altitudinal belts is the following: - up to 200 m - pine subshrub and green moss ("zonal") forest replaced by mixed pine and birch forest near the upper boundary; - 200-300 m - birch crooked subshrub wood; - above 300 m - tundra subshrub and lichen communities. Ecosystems of Hangaslachdenvara upland have been damaged by air pollution (SO2, Ni, Cu emissions) of the Pechenganikel Plant. This impact has led to plant community suppression and formation of barren lands. Besides the soil cover was significantly disturbed, especially upper horizons. Burying of soil profiles, represented by Podzols (WRB, 2015), also manifested itself in the exploited part of the area. The vegetation cover of Hangaslachdenvara upland is the following: - up to 130 m - birch and aspen subshrub and grass forest instead of pine forest ("zonal"); - 130-200 m - barren lands instead of pine forest ("zonal"); - above 200 m - barren lands instead of birch crooked subshrub wood, which stretched to the north-east, proving the leading role of prevailing southwestern winds in pollution spreading in the area. As the anthropogenic impact decreases due to the Plant's emissions decline, there have been identified signs of ecosystem restoration. The beginning restoration helps parvifoliate forests to grow in barren lands, including the above-mentioned birch and aspen forest on Hangaslachdenvara upland. Reductive processes of soil formation are responsible for the development of soddy or raw humus horizons in the substrate overlaying the well-developed Podzols. Nevertheless, there is no restoration above 130 m on Hangaslachdenvara upland owing to the barrier effect, in other words, intensive deposition and accumulation of air pollutants on the upland's top. Thus, there has been defined that the anthropogenic impact led to total vegetation vertical zonality modification and physical disturbance of soil cover in East Fennoscandia. The typical taiga scheme of "coniferous forest - birch crooked wood - tundra subshrub and lichen communities" altitudinal belts was replaced by that of "parvifoliate forest - barren land" altitudinal belts. However, after the reduction of anthropogenic influence "zonal" plant communities begin to restore gradually and weak developed soils are forming.

Potential of Sentinel-1 Radar Data for the Assessment of Soil and Cereal Cover Parameters.

PubMed

Bousbih, Safa; Zribi, Mehrez; Lili-Chabaane, Zohra; Baghdadi, Nicolas; El Hajj, Mohammad; Gao, Qi; Mougenot, Bernard

2017-11-14

The main objective of this study is to analyze the potential use of Sentinel-1 (S1) radar data for the estimation of soil characteristics (roughness and water content) and cereal vegetation parameters (leaf area index (LAI), and vegetation height (H)) in agricultural areas. Simultaneously to several radar acquisitions made between 2015 and 2017, using S1 sensors over the Kairouan Plain (Tunisia, North Africa), ground measurements of soil roughness, soil water content, LAI and H were recorded. The NDVI (normalized difference vegetation index) index computed from Landsat optical images revealed a strong correlation with in situ measurements of LAI. The sensitivity of the S1 measurements to variations in soil moisture, which has been reported in several scientific publications, is confirmed in this study. This sensitivity decreases with increasing vegetation cover growth (NDVI), and is stronger in the VV (vertical) polarization than in the VH cross-polarization. The results also reveal a similar increase in the dynamic range of radar signals observed in the VV and VH polarizations as a function of soil roughness. The sensitivity of S1 measurements to vegetation parameters (LAI and H) in the VV polarization is also determined, showing that the radar signal strength decreases when the vegetation parameters increase. No vegetation parameter sensitivity is observed in the VH polarization, probably as a consequence of volume scattering effects.

Potential of Sentinel-1 Radar Data for the Assessment of Soil and Cereal Cover Parameters

PubMed Central

Bousbih, Safa; Lili-Chabaane, Zohra; El Hajj, Mohammad; Gao, Qi

2017-01-01

The main objective of this study is to analyze the potential use of Sentinel-1 (S1) radar data for the estimation of soil characteristics (roughness and water content) and cereal vegetation parameters (leaf area index (LAI), and vegetation height (H)) in agricultural areas. Simultaneously to several radar acquisitions made between 2015 and 2017, using S1 sensors over the Kairouan Plain (Tunisia, North Africa), ground measurements of soil roughness, soil water content, LAI and H were recorded. The NDVI (normalized difference vegetation index) index computed from Landsat optical images revealed a strong correlation with in situ measurements of LAI. The sensitivity of the S1 measurements to variations in soil moisture, which has been reported in several scientific publications, is confirmed in this study. This sensitivity decreases with increasing vegetation cover growth (NDVI), and is stronger in the VV (vertical) polarization than in the VH cross-polarization. The results also reveal a similar increase in the dynamic range of radar signals observed in the VV and VH polarizations as a function of soil roughness. The sensitivity of S1 measurements to vegetation parameters (LAI and H) in the VV polarization is also determined, showing that the radar signal strength decreases when the vegetation parameters increase. No vegetation parameter sensitivity is observed in the VH polarization, probably as a consequence of volume scattering effects. PMID:29135929

Relationship between vegetation dynamics and dune mobility in an arid transgressive coastal system, Maspalomas, Canary Islands

NASA Astrophysics Data System (ADS)

Hernández-Cordero, Antonio I.; Hernández-Calvento, Luis; Espino, Emma Pérez-Chacón

2015-06-01

This paper explores the relationship between vegetation dynamics and dune mobility in an arid transgressive coastal dune system, specifically the dune field of Maspalomas (Gran Canaria, Canary Islands). The aim is to understand the strategies of colonization and survival that plant communities have developed in slacks that face dune advance. The relationship between plant colonization and dune migration was performed by following Tamarix canariensis and Traganum moquinii plants for several years. Morphological data about each individual as well as the distance of each plant to the dune were measured. A study of the colonization patterns developed by T. moquinii, T. canariensis, Cyperus laevigatus and Launaea arborescens communities was performed by analyzing the evolution of consolidated plant patches and adult plants in relation to the dune advance. This was achieved using digital orthophotos and spatial analysis from geographic information systems. Initiation of plant colonization over transgressive dunes occurs on both wet and dry slacks. The results show that both plant colonization and development of adult plants are largely related to dune mobility. Thus, survival of T. moquinii and T. canariensis plants under dune migration conditions is related to both distance to the dune front and plant height at the moment of burial. Distance from the dune front and plant height increases chance of survival. The dynamics of adult plants is also related to dune displacement rates. Thus, each community has different thresholds of resistance to mobility rates. The T. canariensis community withstands average rates higher than 3 m/year. Its arboreal structure allows this species to grow high enough to resist the advance of the dunes and burial. For the T. moquinii community, the population decreases gradually to eventually disappear when dune mobility rates exceed 4 m/year. The C. laevigatus community develops at dune mobility rates lower than 3 m/year, decreasing its surface area at higher rates. The L. arborescens community endures dune migration rates of at least 1.8 m/year. However, different distances between the dune front and the vegetated area also significant factor, because these can compensate for the effects of displacement rates. Thus, the closer a vegetated area is to a dune front, the lower the rates of displacement must be to produce a greater reduction in the surface vegetation. Plant communities present two patterns of plant colonization to resist burial by sand, one vertical and the other horizontal. The horizontal pattern is employed by C. laevigatus and L. arborescens communities and consists of locating new generations of plants in progressive alignment with the dune front migration. The vertical pattern is employed by the T. canariensis community, and consists of increasing the heights of the plants. The T. moquinii community can utilize both patterns because it reacts positively to some degree of burial since it is located in areas where the dunes reach different heights.

Sexual differences in microhabitat selection of breeding little bustards Tetrax tetrax: Ecological segregation based on vegetation structure

NASA Astrophysics Data System (ADS)

Morales, M. B.; Traba, J.; Carriles, E.; Delgado, M. P.; de la Morena, E. L. García

2008-11-01

We examined sexual differences in patterns of vegetation structure selection in the sexually dimorphic little bustard. Differences in vegetation structure between male, female and non-used locations during reproduction were examined and used to build a presence/absence model for each sex. Ten variables were measured in each location, extracting two PCA factors (PC1: a visibility-shelter gradient; PC2: a gradient in food availability) used as response variables in GLM explanatory models. Both factors significantly differed between female, male and control locations. Neither study site nor phenology was significant. Logistic regression was used to model male and female presence/absence. Female presence was positively associated to cover of ground by vegetation litter, as well as overall vegetation cover, and negatively to vegetation density over 30 cm above ground. Male presence was positively related to litter cover and short vegetation and negatively to vegetation density over 30 cm above ground. Models showed good global performance and robustness. Female microhabitat selection and distribution seems to be related to the balance between shelter and visibility for surveillance. Male microhabitat selection would be related mainly to the need of conspicuousness for courtship. Accessibility to food resources seems to be equally important for both sexes. Differences suggest ecological sexual segregation resulting from different ecological constraints. These are the first detailed results on vegetation structure selection in both male and female little bustards, and are useful in designing management measures addressing vegetation structure irrespective of landscape composition. Similar microhabitat approaches can be applied to manage the habitat of many declining farmland birds.

Role of habitat complexity in predator-prey dynamics between an introduced fish and larval Long-toed Salamanders (Ambystoma macrodactylum)

USGS Publications Warehouse

Kenison, Erin K; Litt, Andrea R.; Pilliod, David S.; McMahon, Tom E

2016-01-01

Predation by nonnative fishes has reduced abundance and increased extinction risk for amphibian populations worldwide. Although rare, fish and palatable amphibians have been observed to coexist where aquatic vegetation and structural complexity provide suitable refugia. We examined whether larval long-toed salamanders (Ambystoma macrodactylum Baird, 1849) increased use of vegetation cover in lakes with trout and whether adding vegetation structure could reduce predation risk and nonconsumptive effects (NCEs), such as reductions in body size and delayed metamorphosis. We compared use of vegetation cover by larval salamanders in lakes with and without trout and conducted a field experiment to investigate the influence of added vegetation structure on salamander body morphology and life history. The probability of catching salamanders in traps in lakes with trout was positively correlated with the proportion of submerged vegetation and surface cover. Growth rates of salamanders in enclosures with trout cues decreased as much as 85% and the probability of metamorphosis decreased by 56%. We did not find evidence that adding vegetation reduced NCEs in experimental enclosures, but salamanders in lakes with trout utilized more highly-vegetated areas which suggests that adding vegetation structure at the scale of the whole lake may facilitate coexistence between salamanders and introduced trout.

EXCHANGE PROCESSES OF VOLATILE ORGANIC COMPOUNDS ABOVE A TROPICAL RAIN FOREST: IMPLICATIONS FOR MODELING TROPOSPHERIC CHEMISTRY ABOVE DENSE VEGETATION

EPA Science Inventory

Measurements of bi-directional ammonia exchange over a fertilized soybean canopy are presented for an 8 week period during the summer of 2002. This modified Bowen-ratio approach was used to determine fluxes from vertical NH3 and temperature gradients in combination with eddy cova...

Chapter 13: Effects of fuel and vegetation management activities on nonnative invasive plants

Treesearch

Erik J. Martinson; Molly E. Hunter; Jonathan P. Freeman; Philip N. Omi

2008-01-01

Twentieth century land use and management practices have increased the vertical and horizontal continuity of fuels over expansive landscapes. Thus the likelihood of large, severe wildfires has increased, especially in forest types that previously experienced more frequent, less severe fire (Allen and others 2002). Disturbances such as fire may promote nonnative plant...

Ground-Vegetation Clutter Affects Phyllostomid Bat Assemblage Structure in Lowland Amazonian Forest

PubMed Central

Marciente, Rodrigo; Bobrowiec, Paulo Estefano D.; Magnusson, William E.

2015-01-01

Vegetation clutter is a limiting factor for bats that forage near ground level, and may determine the distribution of species and guilds. However, many studies that evaluated the effects of vegetation clutter on bats have used qualitative descriptions rather than direct measurements of vegetation density. Moreover, few studies have evaluated the effect of vegetation clutter on a regional scale. Here, we evaluate the influence of the physical obstruction of vegetation on phyllostomid-bat assemblages along a 520 km transect in continuous Amazonian forest. We sampled bats using mist nets in eight localities during 80 nights (3840 net-hours) and estimated the ground-vegetation density with digital photographs. The total number of species, number of animalivorous species, total number of frugivorous species, number of understory frugivorous species, and abundance of canopy frugivorous bats were negatively associated with vegetation clutter. The bat assemblages showed a nested structure in relation to degree of clutter, with animalivorous and understory frugivorous bats distributed throughout the vegetation-clutter gradient, while canopy frugivores were restricted to sites with more open vegetation. The species distribution along the gradient of vegetation clutter was not closely associated with wing morphology, but aspect ratio and wing load differed between frugivores and animalivores. Vegetation structure plays an important role in structuring assemblages of the bats at the regional scale by increasing beta diversity between sites. Differences in foraging strategy and diet of the guilds seem to have contributed more to the spatial distribution of bats than the wing characteristics of the species alone. PMID:26066654

3D numerical modelling of a willow vegetated river/floodplain system

NASA Astrophysics Data System (ADS)

Wilson, C. A. M. E.; Yagci, O.; Rauch, H.-P.; Olsen, N. R. B.

2006-07-01

SummaryUsing a three-dimensional finite volume code with standard k- ɛ turbulence closure the hydraulic impact of willow stands ( Salix alba and Salix fragilis) on the velocity distribution was modelled. The additional hydraulic resistance of the willow stands was modelled separately to the bed resistance using a drag force term that was introduced into the Navier-Stokes equations. Two flood events of varying magnitude and stages of plant development were simulated using this approach. The river comprises an asymmetric compound channel with vegetated floodplain of reach length 170 m. The willow development has been monitored annually and this information was used to define the density of the willow stands (average number per m 2) and its variation as a function of stand height. During both flood events the willow stands were submerged and in pronation. The willow stands were modelled in bending as well as in their undisturbed vertical state. Modelling the willow stands as vertical or in bending was found to have a major impact on the computed velocity profiles. The impact of using a drag-force approach based on a non-uniform projected area distribution was found to be greater when the plants are modelled vertically than when the plants are modelled in high degrees of bending. In field studies involving flexible plants without leaves, the determination of the drag coefficient is of less importance compared to the need to quantify the degree by which plants are in pronation.

Estimation of Nitrogen Vertical Distribution by Bi-Directional Canopy Reflectance in Winter Wheat

PubMed Central

Huang, Wenjiang; Yang, Qinying; Pu, Ruiliang; Yang, Shaoyuan

2014-01-01

Timely measurement of vertical foliage nitrogen distribution is critical for increasing crop yield and reducing environmental impact. In this study, a novel method with partial least square regression (PLSR) and vegetation indices was developed to determine optimal models for extracting vertical foliage nitrogen distribution of winter wheat by using bi-directional reflectance distribution function (BRDF) data. The BRDF data were collected from ground-based hyperspectral reflectance measurements recorded at the Xiaotangshan Precision Agriculture Experimental Base in 2003, 2004 and 2007. The view zenith angles (1) at nadir, 40° and 50°; (2) at nadir, 30° and 40°; and (3) at nadir, 20° and 30° were selected as optical view angles to estimate foliage nitrogen density (FND) at an upper, middle and bottom layer, respectively. For each layer, three optimal PLSR analysis models with FND as a dependent variable and two vegetation indices (nitrogen reflectance index (NRI), normalized pigment chlorophyll index (NPCI) or a combination of NRI and NPCI) at corresponding angles as explanatory variables were established. The experimental results from an independent model verification demonstrated that the PLSR analysis models with the combination of NRI and NPCI as the explanatory variables were the most accurate in estimating FND for each layer. The coefficients of determination (R2) of this model between upper layer-, middle layer- and bottom layer-derived and laboratory-measured foliage nitrogen density were 0.7335, 0.7336, 0.6746, respectively. PMID:25353983

Estimation of nitrogen vertical distribution by bi-directional canopy reflectance in winter wheat.

PubMed

Huang, Wenjiang; Yang, Qinying; Pu, Ruiliang; Yang, Shaoyuan

2014-10-28

Timely measurement of vertical foliage nitrogen distribution is critical for increasing crop yield and reducing environmental impact. In this study, a novel method with partial least square regression (PLSR) and vegetation indices was developed to determine optimal models for extracting vertical foliage nitrogen distribution of winter wheat by using bi-directional reflectance distribution function (BRDF) data. The BRDF data were collected from ground-based hyperspectral reflectance measurements recorded at the Xiaotangshan Precision Agriculture Experimental Base in 2003, 2004 and 2007. The view zenith angles (1) at nadir, 40° and 50°; (2) at nadir, 30° and 40°; and (3) at nadir, 20° and 30° were selected as optical view angles to estimate foliage nitrogen density (FND) at an upper, middle and bottom layer, respectively. For each layer, three optimal PLSR analysis models with FND as a dependent variable and two vegetation indices (nitrogen reflectance index (NRI), normalized pigment chlorophyll index (NPCI) or a combination of NRI and NPCI) at corresponding angles as explanatory variables were established. The experimental results from an independent model verification demonstrated that the PLSR analysis models with the combination of NRI and NPCI as the explanatory variables were the most accurate in estimating FND for each layer. The coefficients of determination (R2) of this model between upper layer-, middle layer- and bottom layer-derived and laboratory-measured foliage nitrogen density were 0.7335, 0.7336, 0.6746, respectively.

The application of LiDAR to investigate foredune morphology and vegetation

NASA Astrophysics Data System (ADS)

Doyle, Thomas B.; Woodroffe, Colin D.

2018-02-01

LiDAR (Light Detection and Ranging) has been used to investigate coastal landform morphology, evolution, and change for almost a decade. Repeated airborne LiDAR surveys can provide the scientific community with significant observations of how shorelines have evolved, which may then enable forecasts of future patterns of change. However, there have been few studies that have considered the application of this new technology to the specific study of foredune morphology and vegetation. The accuracy and appropriateness of airborne LiDAR needs to be assessed, particularly where the density of vegetation may obscure the underlying topography, prior to interpreting derived geomorphic features. This study: i) tests the vertical accuracy of airborne LiDAR in 37 foredune systems along the coast of south-eastern Australia, and ii) demonstrates that it can be used to describe foredune morphology and vegetation in considerable detail. There was a strong correlation between the remotely-sensed LiDAR-derived elevation and field topographic and vegetation surveys (R2 = 0.96). A protocol for obtaining foredune geomorphic and botanical parameters is described. It enables widespread biogeomorphic characterisation along coasts for which LiDAR data is available, which can benefit both coastal managers and researchers alike.

Analysis of photonic spot profile converter and bridge structure on SOI platform for horizontal and vertical integration

NASA Astrophysics Data System (ADS)

Majumder, Saikat; Jha, Amit Kr.; Biswas, Aishik; Banerjee, Debasmita; Ganguly, Dipankar; Chakraborty, Rajib

2017-08-01

Horizontal spot size converter required for horizontal light coupling and vertical bridge structure required for vertical integration are designed on high index contrast SOI platform in order to form more compact integrated photonic circuits. Both the structures are based on the concept of multimode interference. The spot size converter can be realized by successive integration of multimode interference structures with reducing dimension on horizontal plane, whereas the optical bridge structure consists of a number of vertical multimode interference structure connected by single mode sections. The spot size converter can be modified to a spot profile converter when the final single mode waveguide is replaced by a slot waveguide. Analysis have shown that by using three multimode sections in a spot size converter, an Gaussian input having spot diameter of 2.51 μm can be converted to a spot diameter of 0.25 μm. If the output single mode section is replaced by a slot waveguide, this input profile can be converted to a flat top profile of width 50 nm. Similarly, vertical displacement of 8μm is possible by using a combination of two multimode sections and three single mode sections in the vertical bridge structure. The analyses of these two structures are carried out for both TE and TM modes at 1550 nm wavelength using the semi analytical matrix method which is simple and fast in computation time and memory. This work shows that the matrix method is equally applicable for analysis of horizontally as well as vertically integrated photonic circuit.

Supplement Analysis for the Transmission System Vegetation Management Program FEIS (DOE/EIS-0285/SA-60) - Rocky Reach - Maple Valley No. 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Mark A.

2002-04-15

Vegetation Management along the Rocky Reach – Maple Valley No. 1 Transmission Line ROW from structure 110/1 to the Maple Valley Substation. The transmission line is a 500 kV line. BPA proposes to clear targeted vegetation along access roads and around tower structures that may impede the operation and maintenance of the subject transmission line. BPA plans to conduct vegetation management along existing access road and around structure landings for the purpose of maintaining access to structures site. All work will be in accordance with the National Electrical Safety Code and BPA standards.

Southern Quebec in Late Winter

NASA Technical Reports Server (NTRS)

2002-01-01

These images of Canada's Quebec province were acquired by the Multi-angle Imaging SpectroRadiometer on March 4, 2001. The region's forests are a mixture of coniferous and hardwood trees, and 'sugar-shack' festivities are held at this time of year to celebrate the beginning of maple syrup production. The large river visible in the images is the northeast-flowing St. Lawrence. The city of Montreal is located near the lower left corner, and Quebec City, at the upper right, is near the mouth of the partially ice-covered St. Lawrence Seaway.

Both spectral and angular information are retrieved for every scene observed by MISR. The left-hand image was acquired by the instrument's vertical-viewing (nadir) camera, and is a false-color spectral composite from the near-infrared, red, and blue bands. The right-hand image is a false-color angular composite using red band data from the 60-degree backward-viewing, nadir, and 60-degree forward-viewing cameras. In each case, the individual channels of data are displayed as red, green, and blue, respectively.

Much of the ground remains covered or partially covered with snow. Vegetation appears red in the left-hand image because of its high near-infrared brightness. In the multi-angle composite, vegetated areas appear in shades of green because they are brighter at nadir, possibly as a result of an underlying blanket of snow which is more visible from this direction. Enhanced forward scatter from the smooth water surface results in bluer hues, whereas urban areas look somewhat orange, possibly due to the effect of vertical structures which preferentially backscatter sunlight.

The data were acquired during Terra orbit 6441, and cover an area measuring 275 kilometers x 310 kilometers.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Geometric processing workflow for vertical and oblique hyperspectral frame images collected using UAV

NASA Astrophysics Data System (ADS)

Markelin, L.; Honkavaara, E.; Näsi, R.; Nurminen, K.; Hakala, T.

2014-08-01

Remote sensing based on unmanned airborne vehicles (UAVs) is a rapidly developing field of technology. UAVs enable accurate, flexible, low-cost and multiangular measurements of 3D geometric, radiometric, and temporal properties of land and vegetation using various sensors. In this paper we present a geometric processing chain for multiangular measurement system that is designed for measuring object directional reflectance characteristics in a wavelength range of 400-900 nm. The technique is based on a novel, lightweight spectral camera designed for UAV use. The multiangular measurement is conducted by collecting vertical and oblique area-format spectral images. End products of the geometric processing are image exterior orientations, 3D point clouds and digital surface models (DSM). This data is needed for the radiometric processing chain that produces reflectance image mosaics and multiangular bidirectional reflectance factor (BRF) observations. The geometric processing workflow consists of the following three steps: (1) determining approximate image orientations using Visual Structure from Motion (VisualSFM) software, (2) calculating improved orientations and sensor calibration using a method based on self-calibrating bundle block adjustment (standard photogrammetric software) (this step is optional), and finally (3) creating dense 3D point clouds and DSMs using Photogrammetric Surface Reconstruction from Imagery (SURE) software that is based on semi-global-matching algorithm and it is capable of providing a point density corresponding to the pixel size of the image. We have tested the geometric processing workflow over various targets, including test fields, agricultural fields, lakes and complex 3D structures like forests.

Installing artificial macropores in degraded soils to enhance vertical infiltration and increase soil carbon content

NASA Astrophysics Data System (ADS)

Mori, Yasushi; Fujihara, Atsushi; Yamagishi, Kazuto

2014-12-01

Of all terrestrial media (including vegetation and the atmosphere), soil is the largest store of carbon. Soils also have important functions such as water storage and plant support roles. However, at present, these characteristics do not fully function, because of, for example, climate-change-induced heavy rainfall would wash away the organic-rich surface soils. In this study, artificial macropores were introduced into exposed soil plots for the purpose of enhancing infiltration, and fibrous material was inserted to reinforce the macropore structure. As expected, the capillary force caused by the fibers drew surface water deeper into the soil profile before saturation. Additionally, the same capillary force promoted vertical transport, while micropores (matrix) enhanced horizontal flow. Our results show that infiltration was more effective in the fiber-containing macropores than in empty macropores. Additionally, our column experiments showed that artificial macropores reduced surface runoff when the rainfall intensities were 2, 4, and 20 mm · h-1 but not for 80 mm · h-1. In field experiments, soil moisture sensors installed at depths of 10, 30, and 50 cm responded well to rainfall, showing that artificial macropores were able to successfully introduce surface water into the soil profile. One year after the artificial macropores were installed, a field survey carried out to assess soil organic matter and plant growth showed that plant biomass had doubled and that there was a significant increase in soil carbon. This novel technique has many advantages as it mimics natural processes, is low cost, and has a simple structure.

The interactive effects of fire and diversity on short-term responses of ecosystem processes in experimental mediterranean grasslands.

PubMed

Dimitrakopoulos, Panayiotis G; Siamantziouras, Akis-Stavros D; Galanidis, Alexandros; Mprezetou, Irene; Troumbis, Andreas Y

2006-06-01

We conducted a field experiment using constructed communities to test whether species richness contributed to the maintenance of ecosystem processes under fire disturbance. We studied the effects of diversity components (i.e., species richness and species composition) upon productivity, structural traits of vegetation, decomposition rates, and soil nutrients between burnt and unburnt experimental Mediterranean grassland communities. Our results demonstrated that fire and species richness had interactive effects on aboveground biomass production and canopy structure components. Fire increased biomass production of the highest-richness communities. The effects of fire on aboveground biomass production at different levels of species richness were derived from changes in both vertical and horizontal canopy structure of the communities. The most species-rich communities appeared to be more resistant to fire in relation to species-poor ones, due to both compositional and richness effects. Interactive effects of fire and species richness were not important for belowground processes. Decomposition rates increased with species richness, related in part to increased levels of canopy structure traits. Fire increased soil nutrients and long-term decomposition rate. Our results provide evidence that composition within richness levels had often larger effects on the stability of aboveground ecosystem processes in the face of fire disturbance than species richness per se.

A case study of air quality above an urban roof top vegetable farm.

PubMed

Tong, Zheming; Whitlow, Thomas H; Landers, Andrew; Flanner, Benjamin

2016-01-01

The effect of elevation and rooftop configuration on local air quality was investigated at the Brooklyn Grange rooftop farm during a short-term observational campaign. Using multiple particle counters and sonic anemometers deployed along vertical gradients, we found that PM2.5 concentration decayed with height above the street. Samples adjacent to the street had the highest average PM2.5 concentration and frequent stochastic spikes above background. Rooftop observations 26 m above ground showed 7-33% reductions in average PM2.5 concentration compared with the curbside and had far fewer spikes. A relationship between the vertical extinction rate of PM2.5 and atmospheric stability was found whereby less unstable atmosphere and greater wind shear led to greater PM2.5 extinction due to damped vertical motion of air. Copyright © 2015 Elsevier Ltd. All rights reserved.

Geodetic Imaging Lidar: Applications for high-accuracy, large area mapping with NASA's upcoming high-altitude waveform-based airborne laser altimetry Facility

NASA Astrophysics Data System (ADS)

Blair, J. B.; Rabine, D.; Hofton, M. A.; Citrin, E.; Luthcke, S. B.; Misakonis, A.; Wake, S.

2015-12-01

Full waveform laser altimetry has demonstrated its ability to capture highly-accurate surface topography and vertical structure (e.g. vegetation height and structure) even in the most challenging conditions. NASA's high-altitude airborne laser altimeter, LVIS (the Land Vegetation, and Ice Sensor) has produced high-accuracy surface maps over a wide variety of science targets for the last 2 decades. Recently NASA has funded the transition of LVIS into a full-time NASA airborne Facility instrument to increase the amount and quality of the data and to decrease the end-user costs, to expand the utilization and application of this unique sensor capability. Based heavily on the existing LVIS sensor design, the Facility LVIS instrument includes numerous improvements for reliability, resolution, real-time performance monitoring and science products, decreased operational costs, and improved data turnaround time and consistency. The development of this Facility instrument is proceeding well and it is scheduled to begin operations testing in mid-2016. A comprehensive description of the LVIS Facility capability will be presented along with several mission scenarios and science applications examples. The sensor improvements included increased spatial resolution (footprints as small as 5 m), increased range precision (sub-cm single shot range precision), expanded dynamic range, improved detector sensitivity, operational autonomy, real-time flight line tracking, and overall increased reliability and sensor calibration stability. The science customer mission planning and data product interface will be discussed. Science applications of the LVIS Facility include: cryosphere, territorial ecology carbon cycle, hydrology, solid earth and natural hazards, and biodiversity.

NEMA, a functional-structural model of nitrogen economy within wheat culms after flowering. II. Evaluation and sensitivity analysis.

PubMed

Bertheloot, Jessica; Wu, Qiongli; Cournède, Paul-Henry; Andrieu, Bruno

2011-10-01

Simulating nitrogen economy in crop plants requires formalizing the interactions between soil nitrogen availability, root nitrogen acquisition, distribution between vegetative organs and remobilization towards grains. This study evaluates and analyses the functional-structural and mechanistic model of nitrogen economy, NEMA (Nitrogen Economy Model within plant Architecture), developed for winter wheat (Triticum aestivum) after flowering. NEMA was calibrated for field plants under three nitrogen fertilization treatments at flowering. Model behaviour was investigated and sensitivity to parameter values was analysed. Nitrogen content of all photosynthetic organs and in particular nitrogen vertical distribution along the stem and remobilization patterns in response to fertilization were simulated accurately by the model, from Rubisco turnover modulated by light intercepted by the organ and a mobile nitrogen pool. This pool proved to be a reliable indicator of plant nitrogen status, allowing efficient regulation of nitrogen acquisition by roots, remobilization from vegetative organs and accumulation in grains in response to nitrogen treatments. In our simulations, root capacity to import carbon, rather than carbon availability, limited nitrogen acquisition and ultimately nitrogen accumulation in grains, while Rubisco turnover intensity mostly affected dry matter accumulation in grains. NEMA enabled interpretation of several key patterns usually observed in field conditions and the identification of plausible processes limiting for grain yield, protein content and root nitrogen acquisition that could be targets for plant breeding; however, further understanding requires more mechanistic formalization of carbon metabolism. Its strong physiological basis and its realistic behaviour support its use to gain insights into nitrogen economy after flowering.

A Robust Gold Deconvolution Approach for LiDAR Waveform Data Processing to Characterize Vegetation Structure

NASA Astrophysics Data System (ADS)

Zhou, T.; Popescu, S. C.; Krause, K.; Sheridan, R.; Ku, N. W.

2014-12-01

Increasing attention has been paid in the remote sensing community to the next generation Light Detection and Ranging (lidar) waveform data systems for extracting information on topography and the vertical structure of vegetation. However, processing waveform lidar data raises some challenges compared to analyzing discrete return data. The overall goal of this study was to present a robust de-convolution algorithm- Gold algorithm used to de-convolve waveforms in a lidar dataset acquired within a 60 x 60m study area located in the Harvard Forest in Massachusetts. The waveform lidar data was collected by the National Ecological Observatory Network (NEON). Specific objectives were to: (1) explore advantages and limitations of various waveform processing techniques to derive topography and canopy height information; (2) develop and implement a novel de-convolution algorithm, the Gold algorithm, to extract elevation and canopy metrics; and (3) compare results and assess accuracy. We modeled lidar waveforms with a mixture of Gaussian functions using the Non-least squares (NLS) algorithm implemented in R and derived a Digital Terrain Model (DTM) and canopy height. We compared our waveform-derived topography and canopy height measurements using the Gold de-convolution algorithm to results using the Richardson-Lucy algorithm. Our findings show that the Gold algorithm performed better than the Richardson-Lucy algorithm in terms of recovering the hidden echoes and detecting false echoes for generating a DTM, which indicates that the Gold algorithm could potentially be applied to processing of waveform lidar data to derive information on terrain elevation and canopy characteristics.

Relationship of multispectral satellite data to land surface evaporation from the Australian continent

NASA Technical Reports Server (NTRS)

Smith, R. C. G.; Choudhury, B. J.

1990-01-01

Based on NOAA-9 AVHRR and Nimbus-7 SMMR satellite data, satellite indices of vegetation from the Australian continent are calculated for the period of May 1986 to April 1987. Visible (VIS) and near infrared (NIR) reflectances and the normalized difference (ND) vegetation index are calculated from the AVHRR sensor. The microwave polarization difference (PD) is also calculated as the difference between the vertically and horizontally polarized brightness temperatures at 37 GHz. ND, PD, VIS, and NIR indices were plotted against rainfall and water balance estimates of evaporation. It is concluded that direct satellite monitoring of annual evaporation across the Australian continent using PD or VIS satellite indices of vegetation biomass appears possible for areas with evaporation less than 600 mm/y and that use of the ND relationship at continental scale may underpredict monthly evaporation of forests relative to agriculture.

Uprooting of flexible riparian vegetation: field and laboratory observations

NASA Astrophysics Data System (ADS)

Solari, L.; Calvani, G.; Francalanci, S.

2017-12-01

Vegetation is a key element in fluvial systems, controlling river corridor form and dynamics. Plants actively interact with fluvial processes; their aboveground biomass can affect the flow field and sediment transport and therefore river morphological evolution, whereas their belowground biomass modifies the hydraulic and mechanical properties of the substrate, and consequently the moisture regime and erodibility of the soil (Gurnell, 2014; Solari et al., 2015). Vegetation biomass can either increase over time or can die through the mechanism of uprooting. Despite its important implications in river morphodynamics, vegetation uprooting due to sediment transport during flood events have been poorly investigated (Edmaier et al., 2011). Most of previous research focused on the mechanism of root breakage and on measuring the vegetation resistance to uprooting in the vertical direction (Bywater-Reyes et al., 2015, among others). In this work, we focus on the uprooting of flexible juvenile seedlings vegetation due to flow and to bed erosion. First, we derive a physics-based model for the prediction of vegetation uprooting for given root geometry, soil strength characteristics, flow bed shear stress and bed erosion. The model is then tested in a laboratory flume using two different species of vegetation: Avena sativa and Salix purpurea. Various experiments were run considering increasing flow discharges and a quasi- parallel bed erosion. The vegetation model is then applied to a sediment bar in the Ombrone Pistoiese river where we observed the removal of Salix Purpurea during the flood of November 2016. We implemented a 2D hydraulic model to reconstruct the pattern of bed shear stresses on the bar and we compared the prediction of the vegetation model with the field surveys of Salix purpurea before and after the flood. Results suggest that juvenile seedlings can be easily removed by the flow provided sediment transport takes place.

Remote sensing of vegetation 3-D structure for biodiversity and habitat: Review and implications for lidar and radar spaceborne missions

Treesearch

K.M. Bergen; S.J. Goetz; R.O. Dubayah; G.M. Henebry; C.T. Hunsaker; M.L. Imhoff; R.F. Nelson; G.G. Parker; V.C. Radeloff

2009-01-01

Biodiversity and habitat face increasing pressures due to human and natural influences that alter vegetation structure. Because of the inherent difficulty of measuring forested vegetation three-dimensional (3-D) structure on the ground, this important component of biodiversity and habitat has been, until recently, largely restricted to local measurements, or at larger...

High precision detector robot arm system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shu, Deming; Chu, Yong

A method and high precision robot arm system are provided, for example, for X-ray nanodiffraction with an X-ray nanoprobe. The robot arm system includes duo-vertical-stages and a kinematic linkage system. A two-dimensional (2D) vertical plane ultra-precision robot arm supporting an X-ray detector provides positioning and manipulating of the X-ray detector. A vertical support for the 2D vertical plane robot arm includes spaced apart rails respectively engaging a first bearing structure and a second bearing structure carried by the 2D vertical plane robot arm.

Supplement Analysis for the Transmission System Vegetation Management Program FEIS (DOE/EIS-0285/SA-127- Eugene-Alvey#2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sherer, Brett M.

2003-02-19

BPA proposes to remove unwanted vegetation along the right-of-way, access roads, and around tower structures of the subject transmission line corridor that may impede the operation and maintenance of the identified transmission lines. BPA plans to conduct vegetation control with the goal of removing tall growing vegetation that is currently or will soon be a hazard to the transmission line. BPA’s overall goal is to have low-growing plant communities along the rights-of-way to control the development of potentially threatening vegetation. Vegetation Management for the Eugene-Alvey 115 kV transmission line from structure 7/1 through structure 12/2m, and along portions of themore » following adjacent transmission lines: Hawkins-Alvey 115KV and Alvey-Lane 115KV.« less

The vertical geography of urban soils and its convergence across cities

EPA Science Inventory

The theoretical patterns for vertical soil structure (e.g., A-B-C ordering of horizons) are a basis for research methods and our understanding of ecosystem structure and function in general. A general understanding of how urban soils differ from non-urban soils vertically is need...

Combined effects of climate and land management on watershed vegetation dynamics in an arid environment.

PubMed

Liu, Peilong; Hao, Lu; Pan, Cen; Zhou, Decheng; Liu, Yongqiang; Sun, Ge

2017-07-01

Leaf area index (LAI) is a key parameter to characterize vegetation dynamics and ecosystem structure that determines the ecosystem functions and services such as clean water supply and carbon sequestration in a watershed. However, linking LAI dynamics and environmental controls (i.e., coupling biosphere, atmosphere, and anthroposphere) remains challenging and such type of studies have rarely been done at a watershed scale due to data availability. The present study examined the spatial and temporal variations of LAI for five ecosystem types within a watershed with a complex topography in the Upper Heihe River Basin, a major inland river in the arid and semi-arid western China. We integrated remote sensing-based GLASS (Global Land Surface Satellite) LAI products, interpolated climate data, watershed characteristics, and land management records for the period of 2001-2012. We determined the relationships among LAI, topography, air temperature and precipitation, and grazing history by five ecosystem types using several advanced statistical methods. We show that long-term mean LAI distribution had an obvious vertical pattern as controlled by precipitation and temperature in a hilly watershed. Overall, watershed-wide mean LAI had an increasing trend overtime for all ecosystem types during 2001-2012, presumably as a result of global warming and a wetting climate. However, the fluctuations of observed LAI at a pixel scale (1km) varied greatly across the watershed. We classified the vegetation changes within the watershed as 'Improved', 'Stabilized', and 'Degraded' according their respective LAI changes. We found that climate was not the only driver for temporal vegetation changes for all land cover types. Grazing partially contributed to the decline of LAI in some areas and masked the positive climate warming effects in other areas. Extreme weathers such as cold spells and droughts could substantially affect inter-annual variability of LAI dynamics. We concluded that temporal and spatial LAI dynamics were rather complex and were affected by both climate variations and human disturbances in the study basin. Future monitoring studies should focus on the functional interactions among vegetation dynamics, climate variations, land management, and human disturbances. Published by Elsevier B.V.

A multi-sensor method for in-situ quantification of multiple biodiversity and ecosystem service indicators in wetland vegetation

NASA Astrophysics Data System (ADS)

Zlinszky, András; Prager, Katharina; Koma, Zsófia

2017-04-01

Biodiversity and ecosystem services are in the focus of biogeosciences research and conservation management worldwide. However, their quantification is notoriously difficult. Since full coverage of biodiversity and/or ecosystem services is unfeasible due to their complexity, indicators are recommended: biophysical quantities that are measureable and are expected to be closely related to biodiversity or to ecosystem processes. Nevertheless, many biodiversity and ecosystem service assessments are based on upscaling very few (if any) in-situ measurements using models driven by basic land cover data. Also, many assessments select only a single or very few indicators, which then does not enable analysis of trade-offs and interconnections. Here we propose a system of simple yet reliable field measurements, based on basic sensors, measurements, imaging and sampling technology, suitable for quantitatively representing many components of biodiversity and ecosystem services in emergent wetland vegetation. Along a transect from open water to the shore, sampling stations are laid out that include water temperature, air temperature and humidity sensors, zenith facing photographs and pole contact counts of vegetation in height intervals. Additionally, for some of these stations, small quadrats of vegetation are harvested, separated to individual species and weighed in height intervals above ground/water. Underwater surface of vegetation is estimated by counting stalks and registering average diameter. Finally, decomposition is quantified by leaving a standard amount of biomass in a plastic net bag and re-weighing it a year later. This system allows measuring alpha and beta diversity together with vertical structural diversity, leaf area (as a proxy of shading and pollution absorbtion), biomass (as a proxy of carbon sequestration), underwater surface (as a proxy of fish population sustaining), microclimate influence and soil provision. The necessary tools are temperature and humidity sensors, field scales, pruning shears, plastic net bags, measuring poles (for water depth), a digital camera and a GPS; all small and lightweight enough to be carried and operated by one person under wetland field conditions. Additionally, such measurements are suitable for remote sensing-based direct upscaling of biophysical parameters to create area-covering maps of biodiversity and ecosystem service indicators.

The Effects of Land Surface Heating And Roughness Elements on the Structure and Scaling Laws of Atmospheric Boundary Layer Turbulence

NASA Astrophysics Data System (ADS)

Ghannam, Khaled

The atmospheric boundary-layer is the lowest 500-2000 m of the Earth's atmosphere where much of human life and ecosystem services reside. This layer responds to land surface (e.g. buoyancy and roughness elements) and slowly evolving free tropospheric (e.g. temperature and humidity lapse rates) conditions that arguably mediate and modulate biosphere-atmosphere interactions. Such response often results in spatially- and temporally-rich turbulence scales that continue to be the subject of inquiry given their significance to a plethora of applications in environmental sciences and engineering. The work here addresses key aspects of boundary layer turbulence with a focus on the role of roughness elements (vegetation canopies) and buoyancy (surface heating) in modifying the well-studied picture of shear-dominated wall-bounded turbulence. A combination of laboratory channel experiments, field experiments, and numerical simulations are used to explore three distinct aspects of boundary layer turbulence. These are: • The concept of ergodicity in turbulence statistics within canopies: It has been long-recognized that homogeneous and stationary turbulence is ergodic, but less is known about the effects of inhomogeneity introduced by the presence of canopies on the turbulence statistics. A high resolution (temporal and spatial) flume experiment is used here to test the convergence of the time statistics of turbulent scalar concentrations to their ensemble (spatio-temporal) counterpart. The findings indicate that within-canopy scalar statistics have a tendency to be ergodic, mostly in shallow layers (close to canopy top) where the sweeping flow events appear to randomize the statistics. Deeper layers within the canopy are dominated by low-dimensional (quasi-deterministic) von Karman vortices that tend to break ergodicity. • Scaling laws of turbulent velocity spectra and structure functions in near-surface atmospheric turbulence: the existence of a logarithmic scaling in the structure function of the longitudinal and vertical velocity components is examined using five experimental data sets that span the roughness sub-layer above vegetation canopies, the atmospheric surface-layer above a lake and a grass field, and an open channel experiment. The results indicate that close to the wall/surface, this scaling exists in the longitudinal velocity structure function only, with the vertical velocity counterpart exhibiting a much narrower extent of this range due to smaller separation of scales. Phenomenological aspects of the large-scale eddies show that the length scale formed by the friction velocity and energy dissipation acts as a dominant similarity length scale in collapsing experimental data at different heights, mainly due to the imbalance between local production and dissipation of turbulence kinetic energy. • Nonlocal heat transport in the convective atmospheric boundary-layer: Failure of the mean gradient-diffusion (K-theory) in the convective boundary-layer is explored. Using large eddy simulation runs for the atmospheric boundary layer spanning weakly to strongly convective conditions, a generic diagnostic framework that encodes the role of third-order moments in nonlocal heat transport is developed and tested. The premise is that these nonlocal effects are responsible for the inherent asymmetry in vertical transport, and hence the necessary non-Gaussian nature of the joint probability density function (JPDF) of vertical velocity and potential temperature must account for these effects. Conditional sampling (quadrant analysis) of this function and the imbalance between the flow mechanisms of ejections and sweeps are used to characterize this asymmetry, which is then linked to the third-order moments using a cumulant-discard method for the Gram-Charlier expansion of the JPDF. The connection between the ejection-sweep events and the third-order moments shows that the concepts of bottom-up/top-down diffusion, or updraft/downdraft models, are accounted for by various quadrants of this joint probability density function. To this end, future research directions that build upon this work are also discussed.

In-depth Analysis of Land Surface Emissivity using Microwave Polarization Difference Index to Improve Satellite QPE

NASA Astrophysics Data System (ADS)

Zheng, Y.; Kirstetter, P. E.; Hong, Y.; Wen, Y.; Turk, J.; Gourley, J. J.

2015-12-01

One of primary uncertainties in satellite overland quantitative precipitation estimates (QPE) from passive sensors such as radiometers is the impact on the brightness temperatures by the surface land emissivity. The complexity of surface land emissivity is linked to its temporal variations (diurnal and seasonal) and spatial variations (subsurface vertical profiles of soil moisture, vegetation structure and surface temperature) translating into sub-pixel heterogeneity within the satellite field of view (FOV). To better extract the useful signal from hydrometeors, surface land emissivity needs to be determined and filtered from the satellite-measured brightness temperatures. Based on the dielectric properties of surface land cover constitutes, Microwave Polarization Differential index (MPDI) is expected to carry the composite effect of surface land properties on land surface emissivity, with a higher MPDI indicating a lower emissivity. This study analyses the dependence of MPDI to soil moisture, vegetation and surface skin temperature over 9 different land surface types. Such analysis is performed using the normalized difference vegetation index (NDVI) from MODIS, the near surface air temperature from the RAP model and ante-precedent precipitation accumulation from the Multi-Radar Multi-Sensor as surrogates for the vegetation, surface skin temperature and shallow layer soil moisture, respectively. This paper provides 1) evaluations of brightness temperature-based MPDI from the TRMM and GPM Microwave Imagers in both raining and non-raining conditions to test the dependence of MPDI to precipitation; 2) comparisons of MPDI categorized into instantly before, during and immediately after selected precipitation events to examine the impact of modest-to-heavy precipitation on the spatial pattern of MPDI; 3) inspections of relationship between MPDI versus rain fraction and rain rate within the satellite sensors FOV to investigate the behaviors of MPDI in varying precipitation conditions; 4) analysis of discrepancies of MPDI over 10.65, 19.35, 37 and 85.8 GHz to identify the sensitivity of MPDS to microwave wavelengths.

Cellular behavior controlled by bio-inspired and geometry-tunable nanohairs.

PubMed

Heo, Chaejeong; Jeong, Chanho; Im, Hyeon Seong; Kim, Jong Uk; Woo, Juhyun; Lee, Ji Yeon; Park, Byeonghak; Suh, Minah; Kim, Tae-Il

2017-11-23

A cicada wing has a biocidal feature of rupturing the membrane of cells, while the cactus spine can transmit a water drop to the stem of the plant. Both of these properties have evolved from their respective unique structures. Here, we endeavor to develop geometry-controllable nanohairs that mimic the cicada's wing-like vertical hairs and the cactus spine-like stooped hairs, and to quantitatively characterize the cell migration behavior of the hairy structures. It was found that the neuroblastoma cells are highly sensitive to the variation of surfaces: flat, vertical, and stooped nanohairs (100 nm diameter and 900 nm height). The cells on the vertical hairs showed significantly decreased proliferation. It was found that the behavior of cells cultured on stooped nanohairs is strongly influenced by the direction of the stooped pattern of hairs when we quantitatively measured the migration of cells on flat, vertical, and stooped structures. However, the cells on the flat structures showed random movement and the cells on the vertical nanohairs restricted the nanohair movement. Cells on the stooped structure showed higher forward migration preference compared to that of the other structures. Furthermore, we found that these cellular behaviors on the different patterns of nanohairs were affected by intracellular actin flament change. Consistent with these results, the vertical and stooped structures can facilitate the control of cell viability and guide directional migration for biomedical applications such as organogenesis.

The role of feedback mechanisms in historic channel changes of the lower Rio Grande in the Big Bend region

NASA Astrophysics Data System (ADS)

Dean, David J.; Schmidt, John C.

2011-03-01

Over the last century, large-scale water development of the upper Rio Grande in the U.S. and Mexico, and of the Rio Conchos in Mexico, has resulted in progressive channel narrowing of the lower Rio Grande in the Big Bend region. We used methods operating at multiple spatial and temporal scales to analyze the rate, magnitude, and processes responsible for channel narrowing. These methods included: hydrologic analysis of historic stream gage data, analysis of notes of measured discharges, historic oblique and aerial photograph analysis, and stratigraphic and dendrogeomorphic analysis of inset floodplain deposits. Our analyses indicate that frequent large floods between 1900 and the mid-1940s acted as a negative feedback mechanism and maintained a wide, sandy, multi-threaded river. Declines in mean and peak flow in the mid-1940s resulted in progressive channel narrowing. Channel narrowing has been temporarily interrupted by occasional large floods that widened the channel, however, channel narrowing has always resumed. After large floods in 1990 and 1991, the active channel width of the lower Rio Grande has narrowed by 36-52%. Narrowing has occurred by the vertical accretion of fine-grained deposits on top of sand and gravel bars, inset within natural levees. Channel narrowing by vertical accretion occurred simultaneously with a rapid invasion of non-native riparian vegetation ( Tamarix spp., Arundo donax) which created a positive feedback and exacerbated the processes of channel narrowing and vertical accretion. In two floodplain trenches, we measured 2.75 and 3.5 m of vertical accretion between 1993 and 2008. In some localities, nearly 90% of bare, active channel bars were converted to vegetated floodplain during the same period. Upward shifts of stage-discharge relations occurred resulting in over-bank flooding at lower discharges, and continued vertical accretion despite a progressive reduction in stream flow. Thus, although the magnitude of the average annual flood was reduced between 40 and 50%, over-bank flooding continued. These changes reflect a shift in the geomorphic nature of the Rio Grande from a wide, laterally unstable, multi-thread river, to a laterally stable, single-thread channel with cohesive, vertical banks, and few active in-channel bars.

Quiescent Prominence Structure and Dynamics: a new View From the Hinode/SOT

NASA Astrophysics Data System (ADS)

Berger, T.; Okamoto, J.; Slater, G.; Magara, T.; Tarbell, T.; Tsuneta, S.; Hurlburt, N.

2008-05-01

To date the Hinode/Solar Optical Telescope (SOT) has produced over a dozen sub-arcsecond, multi-hour movies of quiescent solar prominences in both the Ca II 396.8~nm H-line and the H-alpha 656.3~nm line. These datasets have revealed new details of the structure and dynamics of quiescent prominences including a new form of mass transport in the form of buoyant plume upflows from the chromosphere. We review the SOT prominence datasets to show that quiescent prominences appear in two major morphological categories: "vertically" and "horizontally" structured. The vertically structured prominences all show ubiquitous downflows in 400--700~km wide "streams" with velocities of approximately 10~km~s-1. Most of the vertically structured prominences also show episodic upflows in the form of dark turbulent plumes with typical velocities of 20~km~s-1. Large-scale oscillations are frequently seen in vertical prominences with periods on the order of 10 min and upward propagation speeds of approximately 10~km~s-1. In addition, "bubble" events in which large voids 10--30~Mm across inflate and then burst are seen in some of the vertical prominences. In contrast, the horizontally structured quiescent prominences exhibit only limited flows along the horizontal filaments. We speculate on the origin of the distinction between the vertically and horizontally structured prominences, taking into account viewing angle and the underlying photospheric magnetic flux density. We also discuss the nature of the mysterious dark plumes and bubble expansions and their implications for prominence mass balance in light of recent models of prominence magnetic structure that find vertical flows along some field lines.

Root strength changes after logging in southeast Alaska

Treesearch

R. R. Ziemer; D. N. Swanston

1977-01-01

Abstract - A crucial factor in the stability of steep forested slopes is the role of plant roots in maintaining the shear strength of soil mantles. Roots add strength to the soil by vertically anchoring through the soil mass into failures in the bedrock and by laterally tying the slope together across zones of weakness or instability. Once the covering vegetation is...

Quantification of the vertical translocation rate of soil solid-phase material by the magnetic tracer method

NASA Astrophysics Data System (ADS)

Zhidkin, A. P.; Gennadiev, A. N.

2016-07-01

Approaches to the quantification of the vertical translocation rate of soil solid-phase material by the magnetic tracer method have been developed; the tracer penetration depth and rate have been determined, as well as the radial distribution of the tracer in chernozems (Chernozems) and dark gray forest soils (Luvisols) of Belgorod oblast under natural steppe and forest vegetation and in arable lands under agricultural use of different durations. It has been found that the penetration depth of spherical magnetic particles (SMPs) during their 150-year-occurrence in soils of a forest plot is 68 cm under forest, 58 cm on a 100-year old plowland, and only 49 cm on a 150-year-old plowland. In the chernozems of the steppe plot, the penetration depth of SMPs exceeds the studied depth of 70 cm both under natural vegetation and on the plowlands. The penetration rates of SMPs deep into the soil vary significantly among the key plots: 0.92-1.32 mm/year on the forest plot and 1.47-1.63 mm/year on the steppe plot, probably because of the more active recent turbation activity of soil animals.

Multi-Stage Metering Mechanism for Transplanting of Vegetable Seedlings in Paper Pots

NASA Astrophysics Data System (ADS)

Nandede, B. M.; Raheman, H.

2015-12-01

A multi-stage rotating cup type metering mechanism was developed for transplanting of vegetable seedlings of tomato, brinjal and chili raised in paper pots. The developed setup consisted of a seedling feeding wheel, metering wheel, fixed slotted plate, seedling delivery tube, furrow opener, furrow closer and a power transmission system. Its evaluation was carried out with pot seedlings of tomato, brinjal and chili of 8-11 cm height at five forward speeds (0.6, 0.9, 1.2, 2.2 and 3.2 km/h) and two plant spacings (45 and 60 cm) in controlled soil bin condition. The mean values of feeding efficiency, conveying efficiency, planting efficiency and overall efficiency of the multistage metering unit were observed to be higher than 90 % for forward speeds of 0.6 to 2.2 km/h. With further increase in speed to 3.2 km/h, the feeding and conveying efficiency were observed to be higher than 90 %, whereas, the planting efficiency drastically reduced to around 50 % due to the problem in getting the pot seedlings vertically in the furrow. Also the seedlings were falling into the furrow at an angle greater than 70° to the vertical, hence not suitable for transplanting.

Relating use of effective responsive, structure, and non-directive control vegetable parenting practices to subscales from the Model of Goal Directed Behavior

USDA-ARS?s Scientific Manuscript database

Parents may positively influence children's vegetable consumption through effective vegetable parenting practices (VPP). Research has demonstrated three dimensions of effective VPP: Effective Responsiveness, Structure, and Non-Directive Control, but there is limited research investigating each separ...

Predicting use of ineffective responsive, structure and control vegetable parenting practices with the Model of Goal Directed Behavior

USDA-ARS?s Scientific Manuscript database

This study reports the modeling of three categories of ineffective vegetable parenting practices (IVPP) separately (responsive, structure, and control vegetable parenting practices). An internet survey was employed for a cross sectional assessment of parenting practices and cognitive-emotional varia...

Radiative transfer theory for active remote sensing of a layer of small ellipsoidal scatterers. [of vegetation

NASA Technical Reports Server (NTRS)

Tsang, L.; Kubacsi, M. C.; Kong, J. A.

1981-01-01

The radiative transfer theory is applied within the Rayleigh approximation to calculate the backscattering cross section of a layer of randomly positioned and oriented small ellipsoids. The orientation of the ellipsoids is characterized by a probability density function of the Eulerian angles of rotation. The radiative transfer equations are solved by an iterative approach to first order in albedo. In the half space limit the results are identical to those obtained via the approach of Foldy's and distorted Born approximation. Numerical results of the theory are illustrated using parameters encountered in active remote sensing of vegetation layers. A distinctive characteristic is the strong depolarization shown by vertically aligned leaves.

Scattering and Emission from Inhomogeneous Vegetation Canopy and Alien Target by Using Three-Dimensional Vector Radiative Transfer (3D-VRT) Equation

NASA Astrophysics Data System (ADS)

Jin, Ya-Qiu; Liang, Zichang

2005-01-01

To solve 3D-VRT equation for the model of spatially inhomogeneous scatter media, the finite enclosure of the scatter media is geometrically divided, in both the vertical z and horizontal (x,y) directions, to form very thin multi-boxes. The zero-th order emission, first-order Mueller matrix of each thin box and an iterative approach of high-order radiative transfer are applied to deriving high-order scattering and emission of whole inhomogeneous scatter media. Numerical results of polarized brightness temperature at microwave frequency and under different radiometer's resolutions from inhomogeneous scatter model such as vegetation canopy and embedded alien target are simulated and discussed.

Estimation of Spatial Trends in LAI in Heterogeneous Semi-arid Ecosystems using Full Waveform Lidar

NASA Astrophysics Data System (ADS)

Glenn, N. F.; Ilangakoon, N.; Spaete, L.; Dashti, H.

2017-12-01

Leaf area index (LAI) is a key structural trait that is defined by the plant functional type (PFT) and controlled by prevailing climate- and human-driven ecosystem stresses. Estimates of LAI using remote sensing techniques are limited by the uncertainties of vegetation inter and intra-gap fraction estimates; this is especially the case in sparse, low stature vegetated ecosystems. Small footprint full waveform lidar digitizes the total amount of return energy with the direction information as a near continuous waveform at a high vertical resolution (1 ns). Thus waveform lidar provides additional data matrices to capture vegetation gaps as well as PFTs that can be used to constrain the uncertainties of LAI estimates. In this study, we calculated a radiometrically calibrated full waveform parameter called backscatter cross section, along with other data matrices from the waveform to estimate vegetation gaps across plots (10 m x 10 m) in a semi-arid ecosystem in the western US. The LAI was then estimated using empirical relationships with directional gap fraction. Full waveform-derived gap fraction based LAI showed a high correlation with field observed shrub LAI (R2 = 0.66, RMSE = 0.24) compared to discrete return lidar based LAI (R2 = 0.01, RMSE = 0.5). The data matrices derived from full waveform lidar classified a number of deciduous and evergreen tree species, shrub species, and bare ground with an overall accuracy of 89% at 10 m. A similar analysis was performed at 1m with overall accuracy of 80%. The next step is to use these relationships to map the PFTs LAI at 10 m spatial scale across the larger study regions. The results show the exciting potential of full waveform lidar to identify plant functional types and LAI in low-stature vegetation dominated semi-arid ecosystems, an ecosystem in which many other remote sensing techniques fail. These results can be used to assess ecosystem state, habitat suitability as well as to constrain model uncertainties in vegetation dynamic models with a combination of other remote sensing techniques. Multi-spatial resolution (1 m and 10 m) studies provide basic information on the applicability and detection thresholds of future global satellite sensors designed at coarser spatial resolutions (e.g. GEDI, ICESat-2) in semi-arid ecosystems.

Evaluation of Aesthetic Function and Thermal Modification of Vertical Greenery at Bogor City, Indonesia

NASA Astrophysics Data System (ADS)

Sulistyantara, B.; Sesara, R.

2017-10-01

Bogor city currently develops vertical greenery due to counter the decreasing of green space quantity. Vertical greenery is a planting method using vertical structure similar to retaining walls. There are some benefits of vertical greenery, such as providing aesthetics value of the landscape, to protect from the heat, to reduce noise, and to reduce pollution. The purpose of this study were to identify thermal modification by vertical greenery in Bogor city, to assess the aesthetics value from vertical greenery, and to provide a recommendation in attempt to manage and improve the quality of vertical greenery in Bogor city. The study was conducted using Scenic Beauty Estimation method, and was done by providing questionnaires to the respondents in order to assess the aesthetics value of vertical greenery. Infrared thermometer was also used to measure the surface’s temperature to evaluate thermal modification function of the vertical greenery. The result of study proved that vertical greenery in the Bogor city has considerably good aesthetic. It also showed that there is a decreasing in surface temperature of the vertical greenery structure.

The role of root distribution in eco-hydrological modeling in semi-arid regions

NASA Astrophysics Data System (ADS)

Sivandran, G.; Bras, R. L.

2010-12-01

In semi arid regions, the rooting strategies employed by vegetation can be critical to its survival. Arid regions are characterized by high variability in the arrival of rainfall, and species found in these areas have adapted mechanisms to ensure the capture of this scarce resource. Niche separation, through rooting strategies, is one manner in which different species coexist. At present, land surface models prescribe rooting profiles as a function of only the plant functional type of interest with no consideration for the soil texture or rainfall regime of the region being modeled. These models do not incorporate the ability of vegetation to dynamically alter their rooting strategies in response to transient changes in environmental forcings and therefore tend to underestimate the resilience of many of these ecosystems. A coupled, dynamic vegetation and hydrologic model, tRIBS+VEGGIE, was used to explore the role of vertical root distribution on hydrologic fluxes. Point scale simulations were carried out using two vertical root distribution schemes: (i) Static - a temporally invariant root distribution; and (ii) Dynamic - a temporally variable allocation of assimilated carbon at any depth within the root zone in order to minimize the soil moisture-induced stress on the vegetation. The simulations were forced with a stochastic climate generator calibrated to weather stations and rain gauges in the semi-arid Walnut Gulch Experimental Watershed in Arizona. For the static root distribution scheme, a series of simulations were carried out varying the shape of the rooting profile. The optimal distribution for the simulation was defined as the root distribution with the maximum mean transpiration over a 200 year period. This optimal distribution was determined for 5 soil textures and using 2 plant functional types, and the results varied from case to case. The dynamic rooting simulations allow vegetation the freedom to adjust the allocation of assimilated carbon to different rooting depths in response to changes in stress caused by the redistribution and uptake of soil moisture. The results obtained from these experiments elucidate the strong link between plant functional type, soil texture and climate and highlight the potential errors in the modeling of hydrologic fluxes from imposing a static root profile.

The influence of Vegetation Water Content (VWC) dynamics on microwave observations of a corn canopy during SMAPVEX16-IA

NASA Astrophysics Data System (ADS)

Steele-Dunne, Susan; Polo Bermejo, Jaime; Judge, Jasmeet; Bongiovanni, Tara; Chakrabarti, Subit; Liu, Pang-Wei; Bragdon, James; Hornbuckle, Brian

2017-04-01

Vegetation cover confounds soil moisture retrieval from both active and passive microwave remote sensing observations. Vegetation attenuates the signal from the soil as well as contributing to emission and scattering. The goal of this study was to characterize the vertical distribution of moisture within an agricultural canopy, to examine how this varies during the growing season and to determine the influence these changes have on emission and backscatter from the surface. To this end, an extensive campaign of destructive sampling was conducted in a rain-fed corn field at Buckeye, Iowa within the SMAPVEX16-IA study domain. The experiment duration extended from the beginning of IOP1 to the end of IOP2, i.e. from May 18 to August 16 2016. Destructive vegetation sampling was performed on most days upon which SMAP had both an ascending and a descending pass. On these days, destructive samples were collected at 6pm and 6pm unless the weather conditions were prohibitive. In addition to measuring the bulk vegetation water content for comparison to the SMAP retrieved VWC, the samples were split into leaves and stems. To study the vertical profiles, leaf moisture content was measured as a function of collar height and the stem was cut into 10cm sections. The influence of plant development on the bulk and profile VWC was clearly discernible in the observations. Diurnal variations in bulk VWC were relatively small due to moisture availability in the root zone. SMAP brightness temperatures, and tower-based observations from the University of Florida radiometer and radar systems were analyzed to investigate the impact of VWC variations on emission and backscatter. Dynamic variations in SMAP retrieved soil moisture were notably larger than those observed in-situ, particularly during the early growing season. This may be attributed to the difference between observed VWC and that used in the SMAP retrieval during the early growing season. Backscatter (and RVI) increased, as expected, in response to accumulating biomass, though retaining some sensitivity to soil moisture variations. Polarization-dependent diurnal differences of up to 2dB were observed in the backscatter from the fully grown corn canopy.

Early vegetation development on an exposed reservoir: implications for dam removal.

PubMed

Auble, Gregor T; Shafroth, Patrick B; Scott, Michael L; Roelle, James E

2007-06-01

The 4-year drawdown of Horsetooth Reservoir, Colorado, for dam maintenance, provides a case study analog of vegetation response on sediment that might be exposed from removal of a tall dam. Early vegetation recovery on the exposed reservoir bottom was a combination of (1) vegetation colonization on bare, moist substrates typical of riparian zones and reservoir sediment of shallow dams and (2) a shift in moisture status from mesic to the xeric conditions associated with the pre-impoundment upland position of most of the drawdown zone. Plant communities changed rapidly during the first four years of exposure, but were still substantially different from the background upland plant community. Predictions from the recruitment box model about the locations of Populus deltoides subsp. monilifera (plains cottonwood) seedlings relative to the water surface were qualitatively confirmed with respect to optimum locations. However, the extreme vertical range of water surface elevations produced cottonwood seed regeneration well outside the predicted limits of drawdown rate and height above late summer stage. The establishment and survival of cottonwood at high elevations and the differences between the upland plant community and the community that had developed after four years of exposure suggest that vegetation recovery following tall dam removal will follow a trajectory very different from a simple reversal of the response to dam construction, involving not only long time scales of establishment and growth of upland vegetation, but also possibly decades of persistence of legacy vegetation established during the reservoir to upland transition.

Early vegetation development on an exposed reservoir: Implications for dam removal

USGS Publications Warehouse

Auble, G.T.; Shafroth, P.B.; Scott, M.L.; Roelle, J.E.

2007-01-01

The 4-year drawdown of Horsetooth Reservoir, Colorado, for dam maintenance, provides a case study analog of vegetation response on sediment that might be exposed from removal of a tall dam. Early vegetation recovery on the exposed reservoir bottom was a combination of (1) vegetation colonization on bare, moist substrates typical of riparian zones and reservoir sediment of shallow dams and (2) a shift in moisture status from mesic to the xeric conditions associated with the pre-impoundment upland position of most of the drawdown zone. Plant communities changed rapidly during the first four years of exposure, but were still substantially different from the background upland plant community. Predictions from the recruitment box model about the locations of Populus deltoides subsp. monilifera (plains cottonwood) seedlings relative to the water surface were qualitatively confirmed with respect to optimum locations. However, the extreme vertical range of water surface elevations produced cottonwood seed regeneration well outside the predicted limits of drawdown rate and height above late summer stage. The establishment and survival of cottonwood at high elevations and the differences between the upland plant community and the community that had developed after four years of exposure suggest that vegetation recovery following tall dam removal will follow a trajectory very different from a simple reversal of the response to dam construction, involving not only long time scales of establishment and growth of upland vegetation, but also possibly decades of persistence of legacy vegetation established during the reservoir to upland transition. ?? 2007 Springer Science+Business Media, LLC.

Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

NASA Astrophysics Data System (ADS)

Moffett, Kevan B.; Gorelick, Steven M.

2016-03-01

Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

Rethinking the role of edaphic condition in halophyte vegetation degradation on salt marshes due to coastal defense structure

NASA Astrophysics Data System (ADS)

Xie, Tian; Cui, Baoshan; Bai, Junhong; Li, Shanze; Zhang, Shuyan

2018-02-01

Determining how human disturbance affects plant community persistence and species conservation is one of the most pressing ecological challenges. The large-scale disturbance form defense structures usually have a long-term and potential effect on phytocommunity in coastal saltmarshes. Coastal defense structures usually remove the effect of tidal wave on tidal salt marshes. As a consequence, edaphic factors such as the salinity and moisture contents are disturbed by tidal action blocking. However, few previous studies have explicitly addressed the response of halophyte species persistence and dynamics to the changing edaphic conditions. The understanding of the response of species composition in seed banks and aboveground vegetation to the stress is important to identify ecological effect of coastal defense structures and provide usefully insight into restoration. Here, we conducted a field study to distinguish the density, species composition and relationships of seed bank with aboveground vegetation between tidal flat wetlands with and without coastal defense structures. We also addressed the role of edaphic condition in vegetation degradation caused by coastal defense structures in combination with field monitor and greenhouse experiments. Our results showed the density of the seed bank and aboveground vegetation in the tidal flat without coastal defense structures was significantly lower than the surrounded flat with coastal defense structures. A total of 14 species were founded in the surrounded flat seed bank and 11 species in the tidal flat, but three species were only recorded in aboveground vegetation of the tidal flat which was much lower than 24 aboveground species in the surrounded flat. The absent of species in aboveground vegetation contributed to low germination rate which depend on the edaphic condition. The germination of seeds in the seed bank were inhabited by high soil salinity in the tidal flat and low soil moisture in the surrounded flat. Our study supported the hypothesis that the change of edaphic condition caused by coastal defense structures was the main reason for the difference of the species composition similarity between aboveground vegetation and the soil seed bank between the tidal and surrounded flats. Therefore, mitigating the hydrological disturbance and maintaining the original state of edaphic factors would be useful implications for reducing the ecological effect of defense structure to vegetation communities in coastal salt marshes.

Large-Diameter InGaAs/AlGaAs Vertical-Cavity Surface-Emitting Lasers with Low Threshold Current Density Fabricated Using a Simple Chemical Etch Process

DTIC Science & Technology

1994-03-01

Epitaxial structure of vertical cavity surface - emitting laser ( VCSEL ...diameter (75 tum < d< 150 prm) vertical - cavity surface - emitting lasers fabricated from an epitaxial structure containing a single In0 .2Ga 8.,As quantum...development of vertical - cavity surface - emitting lasers ( VCSELs ) [1] has enabled III-V semiconductor technology to be applied to cer- tain optical

THE VERTICAL X-SHAPED STRUCTURE IN THE MILKY WAY: EVIDENCE FROM A SIMPLE BOXY BULGE MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhaoyu; Shen Juntai, E-mail: jshen@shao.ac.cn

2012-09-20

A vertical X-shaped structure in the Galactic bulge was recently reported. Here, we present evidence of a similar X-shaped structure in the Shen et al. 2010 bar/boxy bulge model that simultaneously matches the stellar kinematics successfully. The X-shaped structure is found in the central region of our bar/boxy bulge model and is qualitatively consistent with the observed one in many aspects. End-to-end separations of the X-shaped structure in the radial and vertical directions are roughly 3 kpc and 1.8 kpc, respectively. The X-shaped structure contains about 7% of light in the boxy bulge region, but it is significant enough tomore » be identified in observations. An X-shaped structure naturally arises in the formation of bar/boxy bulges and is mainly associated with orbits trapped around the vertically extended x{sub 1} family. Like the bar in our model, the X-shaped structure tilts away from the Sun-Galactic center line by 20 Degree-Sign . The X-shaped structure becomes increasingly symmetric about the disk plane, so the observed symmetry may indicate that it formed at least a few billion years ago. The existence of the vertical X-shaped structure suggests that the formation of the Milky Way bulge is shaped mainly by internal disk dynamical instabilities.« less

Quantifying the Hydraulic Roughness of Vegetation using Physical Modelling and Through-Water Terrestrial Laser Scanning.

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Leyland, J.; Nield, J. M.

2016-12-01

Plants function as large-scale, flexible obstacles that exert additional drag on water flows, affecting local scale turbulence and the structure of the boundary layer. Hence, vegetation plays a significant role controlling surface water flows and modulating geomorphic change. This makes it an important, but often under considered, component when undertaking flood or erosion control actions, or designing river restoration strategies. Vegetative drag varies depending on flow conditions and the associated vegetation structure and temporary reconfiguration of the plant. Whilst several approaches have been developed to describe this relationship, they have been limited due to the difficulty of accurately and precisely characterising the vegetation itself, especially when it is submerged in flow. In practice, vegetative drag is commonly expressed through bulk parameters that are typically derived from lookup tables. Terrestrial Laser Scanning (TLS) has the ability to capture the surface of in situ objects as 3D point clouds, at high resolution (mm), precision and accuracy, even when submerged in water. This allows for the development of workflows capable of quantifying vegetation structure in 3D from dense TLS point cloud data. A physical modelling experiment investigated the impact of a series of structurally variable plants on flow at three different velocities. Acoustic Doppler Velocimetry (ADV) was employed to measure the velocity field and the corresponding fluvial drag of the vegetation was estimated using a bulk roughness function calculated from precise measurements of the water surface slope. Simultaneously, through-water TLS was employed to capture snapshots of plant deformation and distinguish plant structure during flow, using a porosity approach. Although plant type is important, we find a good relationship between plant structure, drag and adjustments of the velocity field.

Variations of deep soil moisture under different vegetation types and influencing factors in a watershed of the Loess Plateau, China

NASA Astrophysics Data System (ADS)

Fang, Xuening; Zhao, Wenwu; Wang, Lixin; Feng, Qiang; Ding, Jingyi; Liu, Yuanxin; Zhang, Xiao

2016-08-01

Soil moisture in deep soil layers is a relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the variations in deep soil moisture and its influencing factors at a moderate watershed scale is important to ensure the sustainability of vegetation restoration efforts. In this study, we focus on analyzing the variations and factors that influence the deep soil moisture (DSM) in 80-500 cm soil layers based on a soil moisture survey of the Ansai watershed in Yan'an in Shanxi Province. Our results can be divided into four main findings. (1) At the watershed scale, higher variations in the DSM occurred at 120-140 and 480-500 cm in the vertical direction. At the comparable depths, the variation in the DSM under native vegetation was much lower than that in human-managed vegetation and introduced vegetation. (2) The DSM in native vegetation and human-managed vegetation was significantly higher than that in introduced vegetation, and different degrees of soil desiccation occurred under all the introduced vegetation types. Caragana korshinskii and black locust caused the most serious desiccation. (3) Taking the DSM conditions of native vegetation as a reference, the DSM in this watershed could be divided into three layers: (i) a rainfall transpiration layer (80-220 cm); (ii) a transition layer (220-400 cm); and (iii) a stable layer (400-500 cm). (4) The factors influencing DSM at the watershed scale varied with vegetation types. The main local controls of the DSM variations were the soil particle composition and mean annual rainfall; human agricultural management measures can alter the soil bulk density, which contributes to higher DSM in farmland and apple orchards. The plant growth conditions, planting density, and litter water holding capacity of introduced vegetation showed significant relationships with the DSM. The results of this study are of practical significance for vegetation restoration strategies, especially for the choice of vegetation types, planting zones, and proper human management measures.

Arbuscular mycorrhizal fungi in two vertical-flow wetlands constructed for heavy metal-contaminated wastewater bioremediation.

PubMed

Xu, Zhouying; Wu, Yang; Jiang, Yinghe; Zhang, Xiangling; Li, Junli; Ban, Yihui

2018-05-01

Over the last three decades, the presence of arbuscular mycorrhizal fungi (AMF) in wetland habitats had been proven, and their roles played in wetland ecosystems and potential functions in wastewater bioremediation technical installations are interesting issues. To increase knowledge on the functions of AMF in the plant-based bioremediation of wastewater, we constructed two vertical-flow wetlands planting with Phragmites australis and investigated AMF distribution in plant roots and their roles played in purification of wastewater polluted by heavy metals (HMs), utilizing the Illumina sequencing technique. A total of 17 operational taxonomic units (OTUs) from 33,031 AMF sequences were obtained, with Glomus being the most dominant. P. australis living in the two vertical-flow constructed wetlands (CWs) harbored diverse AMF comparable with the AM fungal communities in upland habitats. The AMF composition profiles of CW1 (vegetated with non-inoculated plants) and CW2 (vegetated with mycorrhizal plants inoculated with Rhizophagus intraradices) were significantly different. CW1 (15 OTUs) harbored more diverse AMF than CW2 (7 OTUs); however, CW2 harbored much more OTU13 than CW1. In addition, a zipf species abundance distribution (SAD), which might due to the heavy overdominance of OTU13, was observed across AM fugal taxa in P. australis roots of the two CWs. CW1 and CW2 showed high (> 70%) removal capacity of HMs. CW2 exhibited significant higher Cd and Zn removal efficiencies than CW1 (CK) (p = 0.005 and p = 0.008, respectively). It was considered that AMF might play a role in HM removal in CWs.

Application of transilient turbulent theory to study interactions between the atmospheric boundary layer and forest canopies

NASA Astrophysics Data System (ADS)

Inclán, M. G.; Forkel, R.; Dlugi, R.; Stull, R. B.

1996-06-01

The new Forest-Land-Atmosphere ModEl called FLAME is presented. The first-order, nonlocal turbulence closure called transilient turbulence theory (Stull, 1993) is applied to study the interactions between a forested land-surface and the atmospheric boundary layer (ABL). The transilient scheme is used for unequal vertical grid spacing and includes the effects of drag, wake turbulence, and interference to vertical mixing by plant elements. Radiation transfer within the vegetation and the equations for the energy balance at the leaf surface have been taken from Norman (1979). Among others, the model predicts profiles of air temperature, humidity and wind velocity within the ABL, sensible and latent heat fluxes from the soil and the vegetation, the stomata and aerodynamic resistances, as well as profiles of temperature and water content in the soil. Preliminary studies carried out for a cloud free day and idealized initial conditions are presented. The canopy height is 30 m within a vertical domain of 3 km. The model is able to capture some of the effects usually observed within and above forested areas, including the relative wind speed maximum in the trunk space and the counter gradient-fluxes in the lower part of the plant stand. Of special interest is the determination of the location and magnitude of the turbulent mixing between model layers, which permits one to identify the effects of large eddies transporting momentum and scalar quantities into the canopy. A comparison between model simulations and field measurements will be presented in a future paper.

Assessing the vertical structure of baroclinic tidal currents in a global model

NASA Astrophysics Data System (ADS)

Timko, Patrick; Arbic, Brian; Scott, Robert

2010-05-01

Tidal forcing plays an important role in many aspects of oceanography. Mixing, transport of particulates and internal wave generation are just three examples of local phenomena that may depend on the strength of local tidal currents. Advances in satellite altimetry have made an assessment of the global barotropic tide possible. However, the vertical structure of the tide may only be observed by deployment of instruments throughout the water column. Typically these observations are conducted at pre-determined depths based upon the interest of the observer. The high cost of such observations often limits both the number and the length of the observations resulting in a limit to our knowledge of the vertical structure of tidal currents. One way to expand our insight into the baroclinic structure of the ocean is through the use of numerical models. We compare the vertical structure of the global baroclinic tidal velocities in 1/12 degree HYCOM (HYbrid Coordinate Ocean Model) to a global database of current meter records. The model output is a subset of a 5 year global simulation that resolves the eddying general circulation, barotropic tides and baroclinic tides using 32 vertical layers. The density structure within the simulation is both vertically and horizontally non-uniform. In addition to buoyancy forcing the model is forced by astronomical tides and winds. We estimate the dominant semi-diurnal (M2), and diurnal (K1) tidal constituents of the model data using classical harmonic analysis. In regions where current meter record coverage is adequate, the model skill in replicating the vertical structure of the dominant diurnal and semi-diurnal tidal currents is assessed based upon the strength, orientation and phase of the tidal ellipses. We also present a global estimate of the baroclinic tidal energy at fixed depths estimated from the model output.

Estimation of In-canopy Flux Distributions of Reactive Nitrogen and Sulfur within a Mixed Hardwood Forest in Southern Appalachia

NASA Astrophysics Data System (ADS)

Wu, Z.; Walker, J. T.; Chen, X.; Oishi, A. C.; Duman, T.

2017-12-01

Estimating the source/sink distribution and vertical fluxes of air pollutants within and above forested canopies is critical for understanding biological, physical, and chemical processes influencing the soil-vegetation-atmosphere exchange. The vertical source-sink profiles of reactive nitrogen and sulfur were examined using multiple inverse modeling methods in a mixed hardwood forest in the southern Appalachian Mountains where the ecosystem is highly sensitive to loads of pollutant from atmospheric depositions. Measurements of the vertical concentration profiles of ammonia (NH3), nitric acid (HNO3), sulfur dioxide (SO2), and ammonium (NH4+), nitrate (NO3-), and sulfate (SO42-) in PM2.5 were measured during five study periods between May 2015 and August 2016. The mean concentration of NH3 decreased with height in the upper canopy and increased below the understory toward the forest floor, indicating that the canopy was a sink for NH3 but the forest floor was a source. All other species exhibited patterns of monotonically decreasing concentration from above the canopy to the forest floor. Using the measured concentration profiles, we simulated the within-canopy flow fields and estimated the vertical source-sink flux profiles using three inverse approaches: a Eulerian high-order closure model (EUL), a Lagrangian localized near-field (LNF) model, and a new full Lagrangian stochastic model (LSM). The models were evaluated using the within- and above-canopy eddy covariance flux measurements of heat, CO2 and H2O. Differences between models were analyzed and the flux profiles were used to investigate the origin and fate of reactive nitrogen and sulfur compounds within the canopy. The knowledge gained in this study will benefit the development of soil-vegetation-atmosphere models capable of partitioning canopy-scale deposition of nitrogen and sulfur to specific ecosystem compartments.

Wind erosion in semiarid landscapes: Predictive models and remote sensing methods for the influence of vegetation

NASA Technical Reports Server (NTRS)

Musick, H. Brad

1993-01-01

The objectives of this research are: to develop and test predictive relations for the quantitative influence of vegetation canopy structure on wind erosion of semiarid rangeland soils, and to develop remote sensing methods for measuring the canopy structural parameters that determine sheltering against wind erosion. The influence of canopy structure on wind erosion will be investigated by means of wind-tunnel and field experiments using structural variables identified by the wind-tunnel and field experiments using model roughness elements to simulate plant canopies. The canopy structural variables identified by the wind-tunnel and field experiments as important in determining vegetative sheltering against wind erosion will then be measured at a number of naturally vegetated field sites and compared with estimates of these variables derived from analysis of remotely sensed data.

Discriminating crop, weeds and soil surface with a terrestrial LIDAR sensor.

PubMed

Andújar, Dionisio; Rueda-Ayala, Victor; Moreno, Hugo; Rosell-Polo, Joan Ramón; Escolá, Alexandre; Valero, Constantino; Gerhards, Roland; Fernández-Quintanilla, César; Dorado, José; Griepentrog, Hans-Werner

2013-10-29

In this study, the evaluation of the accuracy and performance of a light detection and ranging (LIDAR) sensor for vegetation using distance and reflection measurements aiming to detect and discriminate maize plants and weeds from soil surface was done. The study continues a previous work carried out in a maize field in Spain with a LIDAR sensor using exclusively one index, the height profile. The current system uses a combination of the two mentioned indexes. The experiment was carried out in a maize field at growth stage 12-14, at 16 different locations selected to represent the widest possible density of three weeds: Echinochloa crus-galli (L.) P.Beauv., Lamium purpureum L., Galium aparine L.and Veronica persica Poir.. A terrestrial LIDAR sensor was mounted on a tripod pointing to the inter-row area, with its horizontal axis and the field of view pointing vertically downwards to the ground, scanning a vertical plane with the potential presence of vegetation. Immediately after the LIDAR data acquisition (distances and reflection measurements), actual heights of plants were estimated using an appropriate methodology. For that purpose, digital images were taken of each sampled area. Data showed a high correlation between LIDAR measured height and actual plant heights (R2 = 0.75). Binary logistic regression between weed presence/absence and the sensor readings (LIDAR height and reflection values) was used to validate the accuracy of the sensor. This permitted the discrimination of vegetation from the ground with an accuracy of up to 95%. In addition, a Canonical Discrimination Analysis (CDA) was able to discriminate mostly between soil and vegetation and, to a far lesser extent, between crop and weeds. The studied methodology arises as a good system for weed detection, which in combination with other principles, such as vision-based technologies, could improve the efficiency and accuracy of herbicide spraying.

Discriminating Crop, Weeds and Soil Surface with a Terrestrial LIDAR Sensor

PubMed Central

Andújar, Dionisio; Rueda-Ayala, Victor; Moreno, Hugo; Rosell-Polo, Joan Ramón; Escolà, Alexandre; Valero, Constantino; Gerhards, Roland; Fernández-Quintanilla, César; Dorado, José; Griepentrog, Hans-Werner

2013-01-01

In this study, the evaluation of the accuracy and performance of a light detection and ranging (LIDAR) sensor for vegetation using distance and reflection measurements aiming to detect and discriminate maize plants and weeds from soil surface was done. The study continues a previous work carried out in a maize field in Spain with a LIDAR sensor using exclusively one index, the height profile. The current system uses a combination of the two mentioned indexes. The experiment was carried out in a maize field at growth stage 12–14, at 16 different locations selected to represent the widest possible density of three weeds: Echinochloa crus-galli (L.) P.Beauv., Lamium purpureum L., Galium aparine L.and Veronica persica Poir.. A terrestrial LIDAR sensor was mounted on a tripod pointing to the inter-row area, with its horizontal axis and the field of view pointing vertically downwards to the ground, scanning a vertical plane with the potential presence of vegetation. Immediately after the LIDAR data acquisition (distances and reflection measurements), actual heights of plants were estimated using an appropriate methodology. For that purpose, digital images were taken of each sampled area. Data showed a high correlation between LIDAR measured height and actual plant heights (R2 = 0.75). Binary logistic regression between weed presence/absence and the sensor readings (LIDAR height and reflection values) was used to validate the accuracy of the sensor. This permitted the discrimination of vegetation from the ground with an accuracy of up to 95%. In addition, a Canonical Discrimination Analysis (CDA) was able to discriminate mostly between soil and vegetation and, to a far lesser extent, between crop and weeds. The studied methodology arises as a good system for weed detection, which in combination with other principles, such as vision-based technologies, could improve the efficiency and accuracy of herbicide spraying. PMID:24172283

Vertical biomass distribution drives flow through vegetation: An experiment under unidirectional currents

NASA Astrophysics Data System (ADS)

Villanueva, Raul; Paul, Maike; Vogt, Miriam; Schlurmann, Torsten

2017-04-01

Seagrass meadows are one of many soft measures of coastal protection nowadays not in focus of modern soft coastal protection attempts, despite their steady decline during the last decades. Accurate quantitative prediction of the effectiveness of seagrass meadows as a measure of coastal protection has not yet been achieved. Additionally, restoration attempts have proven difficult due to the bolstered hydrodynamic conditions found on non-vegetated areas, which do not allow resettlement of seeds; consequently no growth can take place. The industry has applied artificial vegetation as a measure of scour-protection for pipelines; such applications, however, rely on high-density meadows to achieve maximized sediment capture, thus leaving no place for regrowth of actual vegetation. Nevertheless, this suggests a solution through the deployment of artificial meadows which emulate the effect of vegetation on hydrodynamic conditions, thus supporting sedimentation, seed resettlement and a resultant sprouting of vegetation. This study aims to assess the interaction between currents and artificial seagrass resembling the characteristics of Zostera marina, one of the most common species of seagrass found in the European North Atlantic, as well as the Baltic Sea, in order to evaluate the possibility of optimizing and utilizing artificial meadows as means of restoration of actual seagrass. The effect of artificial elements emulating vegetation on flow is measured in a circular track flume of maximum 1 m depth and 1 m width. Sedimentation is measured within the flume with the help pf a mobile sand bed. An Acoustic Doppler Velocimeter (ADV) is then utilized to measure velocity profiles in front, within and behind the meadows in different submergence depths to capture the characteristic flow profiles induced by vegetation. The tests include velocities ranging from 0.1 - 0.9 m/s, which are tested individually, allowing to provide an insight into the changes in the velocity profile affected throughout the meadow. Additionally, pressure sensors on the base of individual shoots are used to obtain the drag force induced by the current. Ultrasonic sensors are also deployed in order to measure any height fluctuations within the flume as an effect of vegetation. An efficient artificial plant setup for energy dissipation is assessed by using a constant biomass, but varying vertical distributions. The experiment shows the sheltering and filtering capacities of the artificial seagrass at a density similar to that found in nature. It allows assessment of the protection of settling seeds and sprouts, but also the availability of space for them to grow - thus fulfilling the restoration objectives. Drag measurements prove that the chosen material can hold the tested hydrodynamic conditions, which in turn proves the feasibility of the chosen base layer and anchoring systems. Artificial seagrass meadows prove to be a means of sedimentation good enough for restoration purposes. Results will be further used to inform a study on wave effects comparable to real conditions on northern European coasts.

PALADYN v1.0, a comprehensive land surface-vegetation-carbon cycle model of intermediate complexity

NASA Astrophysics Data System (ADS)

Willeit, Matteo; Ganopolski, Andrey

2016-10-01

PALADYN is presented; it is a new comprehensive and computationally efficient land surface-vegetation-carbon cycle model designed to be used in Earth system models of intermediate complexity for long-term simulations and paleoclimate studies. The model treats in a consistent manner the interaction between atmosphere, terrestrial vegetation and soil through the fluxes of energy, water and carbon. Energy, water and carbon are conserved. PALADYN explicitly treats permafrost, both in physical processes and as an important carbon pool. It distinguishes nine surface types: five different vegetation types, bare soil, land ice, lake and ocean shelf. Including the ocean shelf allows the treatment of continuous changes in sea level and shelf area associated with glacial cycles. Over each surface type, the model solves the surface energy balance and computes the fluxes of sensible, latent and ground heat and upward shortwave and longwave radiation. The model includes a single snow layer. Vegetation and bare soil share a single soil column. The soil is vertically discretized into five layers where prognostic equations for temperature, water and carbon are consistently solved. Phase changes of water in the soil are explicitly considered. A surface hydrology module computes precipitation interception by vegetation, surface runoff and soil infiltration. The soil water equation is based on Darcy's law. Given soil water content, the wetland fraction is computed based on a topographic index. The temperature profile is also computed in the upper part of ice sheets and in the ocean shelf soil. Photosynthesis is computed using a light use efficiency model. Carbon assimilation by vegetation is coupled to the transpiration of water through stomatal conductance. PALADYN includes a dynamic vegetation module with five plant functional types competing for the grid cell share with their respective net primary productivity. PALADYN distinguishes between mineral soil carbon, peat carbon, buried carbon and shelf carbon. Each soil carbon type has its own soil carbon pools generally represented by a litter, a fast and a slow carbon pool in each soil layer. Carbon can be redistributed between the layers by vertical diffusion and advection. For the vegetated macro surface type, decomposition is a function of soil temperature and soil moisture. Carbon in permanently frozen layers is assigned a long turnover time which effectively locks carbon in permafrost. Carbon buried below ice sheets and on flooded ocean shelves is treated differently. The model also includes a dynamic peat module. PALADYN includes carbon isotopes 13C and 14C, which are tracked through all carbon pools. Isotopic discrimination is modelled only during photosynthesis. A simple methane module is implemented to represent methane emissions from anaerobic carbon decomposition in wetlands (including peatlands) and flooded ocean shelf. The model description is accompanied by a thorough model evaluation in offline mode for the present day and the historical period.

Vegetation dynamics at the upper elevational limit of vascular plants in Himalaya.

PubMed

Dolezal, Jiri; Dvorsky, Miroslav; Kopecky, Martin; Liancourt, Pierre; Hiiesalu, Inga; Macek, Martin; Altman, Jan; Chlumska, Zuzana; Rehakova, Klara; Capkova, Katerina; Borovec, Jakub; Mudrak, Ondrej; Wild, Jan; Schweingruber, Fritz

2016-05-04

A rapid warming in Himalayas is predicted to increase plant upper distributional limits, vegetation cover and abundance of species adapted to warmer climate. We explored these predictions in NW Himalayas, by revisiting uppermost plant populations after ten years (2003-2013), detailed monitoring of vegetation changes in permanent plots (2009-2012), and age analysis of plants growing from 5500 to 6150 m. Plant traits and microclimate variables were recorded to explain observed vegetation changes. The elevation limits of several species shifted up to 6150 m, about 150 vertical meters above the limit of continuous plant distribution. The plant age analysis corroborated the hypothesis of warming-driven uphill migration. However, the impact of warming interacts with increasing precipitation and physical disturbance. The extreme summer snowfall event in 2010 is likely responsible for substantial decrease in plant cover in both alpine and subnival vegetation and compositional shift towards species preferring wetter habitats. Simultaneous increase in summer temperature and precipitation caused rapid snow melt and, coupled with frequent night frosts, generated multiple freeze-thaw cycles detrimental to subnival plants. Our results suggest that plant species responses to ongoing climate change will not be unidirectional upward range shifts but rather multi-dimensional, species-specific and spatially variable.

Lateral vegetation growth rates exert control on coastal foredune hummockiness and coalescing time

NASA Astrophysics Data System (ADS)

Goldstein, Evan B.; Moore, Laura J.; Durán Vinent, Orencio

2017-08-01

Coastal foredunes form along sandy, low-sloped coastlines and range in shape from continuous dune ridges to hummocky features, which are characterized by alongshore-variable dune crest elevations. Initially scattered dune-building plants and species that grow slowly in the lateral direction have been implicated as a cause of foredune hummockiness. Our goal in this work is to explore how the initial configuration of vegetation and vegetation growth characteristics control the development of hummocky coastal dunes including the maximum hummockiness of a given dune field. We find that given sufficient time and absent external forcing, hummocky foredunes coalesce to form continuous dune ridges. Model results yield a predictive rule for the timescale of coalescing and the height of the coalesced dune that depends on initial plant dispersal and two parameters that control the lateral and vertical growth of vegetation, respectively. Our findings agree with previous observational and conceptual work - whether or not hummockiness will be maintained depends on the timescale of coalescing relative to the recurrence interval of high-water events that reset dune building in low areas between hummocks. Additionally, our model reproduces the observed tendency for foredunes to be hummocky along the southeast coast of the US where lateral vegetation growth rates are slower and thus coalescing times are likely longer.

Vegetation dynamics at the upper elevational limit of vascular plants in Himalaya

NASA Astrophysics Data System (ADS)

Dolezal, Jiri; Dvorsky, Miroslav; Kopecky, Martin; Liancourt, Pierre; Hiiesalu, Inga; Macek, Martin; Altman, Jan; Chlumska, Zuzana; Rehakova, Klara; Capkova, Katerina; Borovec, Jakub; Mudrak, Ondrej; Wild, Jan; Schweingruber, Fritz

2016-05-01

A rapid warming in Himalayas is predicted to increase plant upper distributional limits, vegetation cover and abundance of species adapted to warmer climate. We explored these predictions in NW Himalayas, by revisiting uppermost plant populations after ten years (2003-2013), detailed monitoring of vegetation changes in permanent plots (2009-2012), and age analysis of plants growing from 5500 to 6150 m. Plant traits and microclimate variables were recorded to explain observed vegetation changes. The elevation limits of several species shifted up to 6150 m, about 150 vertical meters above the limit of continuous plant distribution. The plant age analysis corroborated the hypothesis of warming-driven uphill migration. However, the impact of warming interacts with increasing precipitation and physical disturbance. The extreme summer snowfall event in 2010 is likely responsible for substantial decrease in plant cover in both alpine and subnival vegetation and compositional shift towards species preferring wetter habitats. Simultaneous increase in summer temperature and precipitation caused rapid snow melt and, coupled with frequent night frosts, generated multiple freeze-thaw cycles detrimental to subnival plants. Our results suggest that plant species responses to ongoing climate change will not be unidirectional upward range shifts but rather multi-dimensional, species-specific and spatially variable.

Vegetation dynamics at the upper elevational limit of vascular plants in Himalaya

PubMed Central

Dolezal, Jiri; Dvorsky, Miroslav; Kopecky, Martin; Liancourt, Pierre; Hiiesalu, Inga; Macek, Martin; Altman, Jan; Chlumska, Zuzana; Rehakova, Klara; Capkova, Katerina; Borovec, Jakub; Mudrak, Ondrej; Wild, Jan; Schweingruber, Fritz

2016-01-01

A rapid warming in Himalayas is predicted to increase plant upper distributional limits, vegetation cover and abundance of species adapted to warmer climate. We explored these predictions in NW Himalayas, by revisiting uppermost plant populations after ten years (2003–2013), detailed monitoring of vegetation changes in permanent plots (2009–2012), and age analysis of plants growing from 5500 to 6150 m. Plant traits and microclimate variables were recorded to explain observed vegetation changes. The elevation limits of several species shifted up to 6150 m, about 150 vertical meters above the limit of continuous plant distribution. The plant age analysis corroborated the hypothesis of warming-driven uphill migration. However, the impact of warming interacts with increasing precipitation and physical disturbance. The extreme summer snowfall event in 2010 is likely responsible for substantial decrease in plant cover in both alpine and subnival vegetation and compositional shift towards species preferring wetter habitats. Simultaneous increase in summer temperature and precipitation caused rapid snow melt and, coupled with frequent night frosts, generated multiple freeze-thaw cycles detrimental to subnival plants. Our results suggest that plant species responses to ongoing climate change will not be unidirectional upward range shifts but rather multi-dimensional, species-specific and spatially variable. PMID:27143226

Effects of past burning frequency on plant species structure and composition in dry dipterocarp forest

NASA Astrophysics Data System (ADS)

Wanthongchai, Dr.; Bauhus, Prof.; Goldammer, Prof.

2009-04-01

Anthropogenic burning in dry dipterocarp forests (DDF) has become a common phenomenon throughout Thailand. It is feared that too frequent fires may affect vegetation structure and composition and thus impact on ecosystem productivity. The aim of this study was to quantify the effects of prescribed fires on sites with different past burning regimes on vegetation structure and composition in the Huay Kha Khaeng Wildlife Sanctuary (HKK), Thailand. Fire frequency was determined from satellite images and ranged from frequent, infrequent, rare and unburned with fire occurrences of 7, 2, 1 and 0 out of the past 10 years, respectively. The pre-burn fuel loads, the overstorey and understorey vegetation structure and composition were determined to investigate the effects of the contrasting past burning regimes. The burning experiment was carried out, applying a three-strip head-fire burning technique. The vegetation structure and composition were sampled again one year after the fire to assess the fire impacts. Aboveground fine fuel loads increased with the length of fire-free interval. The woody plant structures of the frequently burned stand differed from those of the other less frequently burned stands. The species composition of the overstorey on the frequently burned site, in particular that of small sized trees (4.5-10 cm dbh), also differed significantly from that of the other sites. Whilst the ground vegetation including shrubs and herbs did not differ between the past burning regimes, frequent burning obviously promoted the proliferation of graminoid vegetation. There was no clear evidence showing that the prescribed fires affected the mortality of trees (dbh> 4.5 cm) on the sites of the different past burning regimes. The effects of prescribed burning on the understorey vegetation structures varied between the past burning regimes and the understorey vegetation type. Therefore, it is recommended that the DDF at HKK should be subjected to a prescribed fire frequency not shorter than every 6-7 years, or 1-2 fires per decade, to maintain ecosystem structure and function. Variation in time and space in this way, the biodiversity of the landscape may be maintained for the long-term. Keywords: Prescribed burning, burning history, burning frequency, plant species, vegetation structure, dry dipterocarp forest, Huay Kha Khaeng wildlife Sanctuary

[Green space vegetation quantity in workshop area of Wuhan Iron and Steel Company].

PubMed

Chen, Fang; Zhou, Zhixiang; Wang, Pengcheng; Li, Haifang; Zhong, Yingfei

2006-04-01

Aimed at the complex community structure and higher fragmentation of urban green space, and based on the investigation of synusia structure and its coverage, this paper studied the vegetation quantity of ornamental green space in the workshop area of Wuhan Iron and Steel Company, with the help of GIS. The results showed that different life forms of ornamental plants in this area had a greater difference in their single leaf area and leaf area index (LAI), and the LAI was not only depended on single leaf area, but also governed by the shape of tree crown and the intensive degree of branches and leaves. The total vegetation quantity was 1 694.2 hm2, with the average LAI being 7.75, and the vegetation quantity of arbor-shrub-herb and arbor-shrub communities accounted for 79.7% and 92.3% of the total, respectively, reflecting that the green space structure was dominated by arbor species and by arbor-shrub-herb and arbor-shrub community types. Single layer-structured lawn had a less percentage, while the vegetation quantity of herb synusia accounted for 22.9% of the total, suggesting an afforestation characteristic of "making use of every bit of space" in the workshop area. The vegetation quantity of urban ornamental green space depended on the area of green space, its synusia structure, and the LAI and coverage of ornamental plants. In enlarging urban green space, ornamental plant species with high LAI should be selected, and community structure should be improved to have a higher vegetation quantity in urban area. To quantify the vegetation quantity of urban ornamental green space more accurately, synusia should be taken as the unit to measure the LAI of typical species, and the synusia structure and its coverage of different community types should be investigated with the help of remote sensing images and GIS.

Impact of vegetation feedback at subseasonal & seasonal timescales on precipitation over North America

NASA Astrophysics Data System (ADS)

Kim, Y.; Wang, G.

2006-05-01

Soil moisture-vegetation-precipitation feedbacks tend to enhance soil moisture memory in some areas of the globe, which contributes to the subseasonal and seasonal climate prediction skill. In this study, the impact of vegetation on precipitation over North America is investigated using a coupled land-atmosphere model CAM3- CLM3. The coupled model has been modified to include a predictive vegetation phenology scheme and validated against the MODIS data. Vegetation phenology is modeled by updating the leaf area index (LAI) daily in response to cumulative and concurrent hydrometeorological conditions. First, driven with the climatological SST, a large group of 5-member ensembles of simulations from the late spring and summer to the end of year are generated with the different initial conditions of soil moisture. The impact of initial soil moisture anomalies on subsequent precipitation is examined with the predictive vegetation phenology scheme disabled/enabled ("SM"/"SM_Veg" ensembles). The simulated climate differences between "SM" and "SM_Veg" ensembles represent the role of vegetation in soil moisture-vegetation- precipitation feedback. Experiments in this study focus on how the response of precipitation to initial soil moisture anomalies depends on their characteristics, including the timing, magnitude, spatial coverage and vertical depth, and further how it is modified by the interactive vegetation. Our results, for example, suggest that the impact of late spring soil moisture anomalies is not evident in subsequent precipitation until early summer when local convective precipitation dominates. With the summer wet soil moisture anomalies, vegetation tends to enhance the positive feedback between soil moisture and precipitation, while vegetation tends to suppress such positive feedback with the late spring anomalies. Second, the impact of vegetation feedback is investigated by driving the model with the inter-annually varying monthly SST (1983-1994). With the predictive vegetation phenology disabled/enabled ("SM"/"SM_Veg" ensembles), the simulated climates are compared with the observation. This will present the role of an interactive or predictive vegetation phenology scheme in subseasonal and seasonal climate prediction. Specifically, the extreme climate events such as drought in 1988 and flood in 1993 over the Midwestern United States will be the focus of results analyses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. J. Appel

This cleanup verification package documents completion of remedial action for the 118-F-3, Minor Construction Burial Ground waste site. This site was an open field covered with cobbles, with no vegetation growing on the surface. The site received irradiated reactor parts that were removed during conversion of the 105-F Reactor from the Liquid 3X to the Ball 3X Project safety systems and received mostly vertical safety rod thimbles and step plugs.

Accuracy of a high-resolution lidar terrain model under a conifer forest canopy

Treesearch

S.E. Reutebuch; R.J. McGaughey; H.-E. Andersen; W.W. Carson

2003-01-01

Airborne laser scanning systems can provide terrain elevation data for open areas with a vertical accuracy of 15 cm. In this study, a high-resolution digital terrain model (DTM) was produced from high-density lidar data. Vegetation in the 500-ha mountainous study area varied from bare ground to dense 70-year-old conifer forest. Conventional ground survey methods were...

An Evaluation System for Foodservice Equipment

DTIC Science & Technology

1985-10-01

flat beater, dough hook, wire whip, wing whip, pastry knife, and sweet dough hook. Some power takeoff attachments available are: vegetable sli er...used extensively for heavy doughs will place a greater stress on motor ana gear assemblies. Select a heavy shock absorbing system, and motor size 1/2...Doughrut Sugaring Machine Doughnut Glazer Blunder x\\utomatic Cookie Dropper Vertical Cutter Mixer Maat Chopper/Grinder Automatic Meat Marinator

Estimating COCOM Natural Background Dormancy

DTIC Science & Technology

2015-04-01

Goode and Espenshade 1953). Maps from Goode’s World Atlas included natural vegetation, agricultural regions, and soils . Clark University provided...and shallow, high mountain soils (Chambers 1967). The vertical stripes indi- cate a probability of more than two weeks of snow cover during the month...needle-leaf evergreen and deciduous trees during dormant or dry season, and desert alluvial deposits, sand, and thin mountain soils 6 Needle-leaf

Proof of the Post-drought Effect of Amazonian Forests from Space

NASA Astrophysics Data System (ADS)

Yang, Y.; Saatchi, S. S.; Xu, L.; Yu, Y.; Myneni, R. B.; Knyazikhin, Y.; CHOI, S.

2015-12-01

In 2005, the tropical forests in Amazonia went through a severe drought event across the entire basin. There have been conflict reports on the drought impact on vegetation and the issue was never settled due to limited ground truth. Remote sensing data have been used but often questioned for signal saturation, data quality, or atmosphere contamination. The quantification of carbon changes in this vast terrestrial carbon pool, especially the post-drought effect, is difficult but essential. Lidar measurements, which are regarded as the accurate retrieval of canopy vertical structure, give us the opportunity to quantify the carbon changes for this severe event. Here, we use the lidar waveforms measured from the GLAS sensor from 2004 to 2007 to calculate the vertical profiles of Amazonian forests and their associated carbon stock. After careful quality-filtering, removal of seasonal effect, as well as uncertainty reduction through spatial averaging and random sampling, we find that the mean canopy height in Amazon has much higher reduction from 2006 to 2007 compared to either the drought year from 2004 to 2005, or the immediate post-drought change from 2005 to 2006, demonstrating a lagged effect of drought. Our estimation of carbon loss from model calculation also show that 2005 drought had an significant impact on the carbon exchange, and emissions from post drought disturbance may match the emissions of annual deforestation from Amazonia.

Spatial-structural analysis of leafless woody riparian vegetation for hydraulic considerations

NASA Astrophysics Data System (ADS)

Weissteiner, Clemens; Jalonen, Johanna; Järvelä, Juha; Rauch, Hans Peter

2013-04-01

Woody riparian vegetation is a vital element of riverine environments. On one hand woody riparian vegetation has to be taken into account from a civil engineering point of view due to boundary shear stress and vegetation drag. On the other hand it has to be considered from a river ecological point of view due to shadowing effects and as a source of organic material for aquatic habitats. In hydrodynamic and hydro-ecological studies the effects of woody riparian vegetation on flow patterns are usually investigated on a very detailed level. On the contrary vegetation elements and their spatial patterns are generally analysed and discussed on the basis of an integral approach measuring for example basal diameters, heights and projected plant areas. For a better understanding of the influence of woody riparian vegetation on turbulent flow and on river ecology, it is essential to record and analyse plant data sets on the same level of quality as for hydrodynamic or hydro-ecologic purposes. As a result of the same scale of the analysis it is possible to incorporate riparian vegetation as a sub-model in the hydraulic analysis. For plant structural components, such as branches on different topological levels it is crucial to record plant geometrical parameters describing the habitus of the plant on branch level. An exact 3D geometrical model of real plants allows for an extraction of various spatial-structural plant parameters. In addition, allometric relationships help to summarize and describe plant traits of riparian vegetation. This paper focuses on the spatial-structural composition of leafless riparia woddy vegetation. Structural and spatial analyses determine detailed geometric properties of the structural components of the plants. Geometrical and topological parameters were recorded with an electro-magnetic scanning device. In total, 23 plants (willows, alders and birches) were analysed in the study. Data were recorded on branch level, which allowed for the development of a 3D geometric plant model. The results are expected to improve knowledge on how the architectural system and allometric relationships of the plants relate to ecological and hydrodynamic properties.

Relationships between forest cutting and understory vegetation: an overview of eastern hardwood stands

Treesearch

Hewlette S. Crawford

1976-01-01

The impacts of forest cutting upon understory vegetation were evaluated for Ozark oak-hickory and Appalachian oak-pine stands. These findings were related to similar information from other eastern forest types. Production of understory vegetation is related to stand type, stand structure, stand disturbance, and site. Stand type, structure, and site operate together to...

Differentiate responses of soil structure to natural vegetation and artificial plantation in landslide hazard region of the West Qinling Mountains, China

NASA Astrophysics Data System (ADS)

Wang, X.; Huang, Z.; Zhao, Y.; Hong, M.

2017-12-01

Natural vegetation and artificial plantation are the most important measures for ecological restoration in soil erosion and landslide hazard-prone regions of China. Previous studies have demonstrated that both measures can significantly change the soil structure and decrease soil and water erosion. Few reports have compared the effects of the two contrasting measures on mechanical and hydrological properties and further tested the differentiate responses of soil structure. In the study areas, two vegetation restoration measures-natural vegetation restoration (NVR) and artificial plantation restoration (APR) compared with control site, with similar topographical and geological backgrounds were selected to investigate the different effects on soil structure based on eight-year ecological restoration projects. The results showed that the surface vegetation played an important role in releasing soil erosion and enhance soil structure stability through change the soil aggregates (SA) and total soil porosity (TSP). The SA<0.25mm content in NVR (36.13%) was higher than that in APR (32.14%). The study indicated that SA and TSP were the principal components (PCs) related to soil structure variation. Soil organic carbon, soil water retention, clay and vegetation biomass were more strongly correlated with the PCs in NVR than those in APR. The study indicated that NVR was more beneficial for soil structure stability than APR. These findings will provide a theoretical basis for the decisions around reasonable land use for ecological restoration and conservation in geological hazard-prone regions.

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

NASA Astrophysics Data System (ADS)

Yáñez-Serrano, A. M.; Nölscher, A. C.; Bourtsoukidis, E.; Derstroff, B.; Zannoni, N.; Gros, V.; Lanza, M.; Brito, J.; Noe, S. M.; House, E.; Hewitt, C. N.; Langford, B.; Nemitz, E.; Behrendt, T.; Williams, J.; Artaxo, P.; Andreae, M. O.; Kesselmeier, J.

2016-09-01

Methyl ethyl ketone (MEK) enters the atmosphere following direct emission from vegetation and anthropogenic activities, as well as being produced by the gas-phase oxidation of volatile organic compounds (VOCs) such as n-butane. This study presents the first overview of ambient MEK measurements at six different locations, characteristic of forested, urban and marine environments. In order to understand better the occurrence and behaviour of MEK in the atmosphere, we analyse diel cycles of MEK mixing ratios, vertical profiles, ecosystem flux data, and HYSPLIT back trajectories, and compare with co-measured VOCs. MEK measurements were primarily conducted with proton-transfer-reaction mass spectrometer (PTR-MS) instruments. Results from the sites under biogenic influence demonstrate that vegetation is an important source of MEK. The diel cycle of MEK follows that of ambient temperature and the forest structure plays an important role in air mixing. At such sites, a high correlation of MEK with acetone was observed (e.g. r2 = 0.96 for the SMEAR Estonia site in a remote hemiboreal forest in Tartumaa, Estonia, and r2 = 0.89 at the ATTO pristine tropical rainforest site in central Amazonia). Under polluted conditions, we observed strongly enhanced MEK mixing ratios. Overall, the MEK mixing ratios and flux data presented here indicate that both biogenic and anthropogenic sources contribute to its occurrence in the global atmosphere.

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

NASA Astrophysics Data System (ADS)

Yáñez-Serrano, A. M.; Nöslcher, A.; Bourtsoukidis, E.; Derstroff, B.; Zannoni, N.; Gros, V.; Matteo, L.; Brito, J.; Noe, S.; House, E. R.; Hewitt, C. N.; Langford, B.; Nemitz, E.; Behrendt, T.; Williams, J.; Artaxo, P.; Andreae, M. O.; Kesselmeier, J.

2016-12-01

Methyl ethyl ketone (MEK) enters the atmosphere following direct emission from vegetation and anthropogenic activities, as well as being produced by the gas-phase oxidation of volatile organic compounds (VOCs) such as n-butane. This study presents the first overview of ambient MEK measurements at six different locations, characteristic of forested, urban and marine environments. In order to understand better the occurrence and behaviour of MEK in the atmosphere, we analyse diel cycles of MEK mixing ratios, vertical profiles, ecosystem flux data, and HYSPLIT back trajectories, and compare with co-measured VOCs. MEK measurements were primarily conducted with proton transfer reaction - mass spectrometer (PTR-MS) instruments. Results from the sites under biogenic influence demonstrate that vegetation is an important source of MEK. The diel cycle of MEK follows that of ambient temperature and the forest structure plays an important role in air mixing. At such sites a high correlation of MEK with acetone was observed (e.g. r2 = 0.96 for the SMEAR-Estonia site in a remote hemi-boreal forest in Tartumaa, Estonia, and r2 = 0.89 at the ATTO pristine tropical rainforest site in central Amazonia). Under polluted conditions, we observed strongly enhanced MEK mixing ratios. Overall, the MEK mixing ratios and flux data presented here indicate that both biogenic and anthropogenic sources contribute to its occurrence in the global atmosphere.

Ecosystem engineering by a colonial mammal: how prairie dogs structure rodent communities.

PubMed

VanNimwegen, Ron E; Kretzer, Justin; Cully, Jack F

2008-12-01

As ecosystem engineers, prairie dogs (Cynomys spp.) physically alter their environment, but the mechanism by which these alterations affect associated faunal composition is not well known. We examined how rodent and vegetation communities responded to prairie dog colonies and landcover at the Cimarron National Grassland in southwest Kansas, USA. We trapped rodents and measured vegetation structure on and off colonies in 2000 and 2003. We plotted two separate ordinations of trapping grids: one based on rodent counts and a second based on vegetation variables. We regressed three factors on each ordination: (1) colony (on-colony and off-colony), (2) cover (shortgrass and sandsage), and (3) habitat (factorial cross of colony x cover). Rodent communities differed by colony but not cover. Vegetation differed across both gradients. Rodent responses to habitat reflected those of colony and cover, but vegetation was found to differ across cover only in the sandsage prairie. This interaction suggested that rodent composition responded to prairie dog colonies, but independently of vegetation differences. We conclude that burrowing and soil disturbance are more important than vegetation cropping in structuring rodent communities.

The Biomass mission: a step forward in quantifying forest biomass and structure

NASA Astrophysics Data System (ADS)

LE Toan, T.

2015-12-01

The primary aim of the ESA BIOMASS mission is to determine, for the first time and in a consistent manner, the global distribution of above-ground forest biomass (AGB) in order to provide greatly improved quantification of the size and distribution of the terrestrial carbon pool, and improved estimates of terrestrial carbon fluxes. Specifically, BIOMASS will measure forest carbon stock, as well as forest height, from data provided by a single satellite giving a biomass map covering tropical, temperate and boreal forests at a resolution of around 200 m every 6 months throughout the five years of the mission. BIOMASS will use a long wavelength SAR (P-band) providing three mutually supporting measurement techniques, namely polarimetric SAR (PolSAR), polarimetric interferometric SAR (PolInSAR) and tomographic SAR (TomoSAR). The combination of these techniques will significantly reduce the uncertainties in biomass retrievals by yielding complementary information on biomass properties. Horizontal mapping: For a forest canopy, the P-band radar waves penetrate deep into the canopy, and their interaction with the structure of the forest will be exploited to map above ground biomass (AGB), as demonstrated from airborne data for temperate, boreal forests and tropical forest. Height mapping: By repeat revisits to the same location, the PolInSAR measurements will be used to estimate the height of scattering in the forest canopy. The long wavelength used by BIOMASS is crucial for the temporal coherence to be preserved over much longer timescales than at L-band, for example. 3D mapping: The P-band frequency used by BIOMASS is low enough to ensure penetration through the entire canopy, even in dense tropical forests. As a consequence, resolution of the vertical structure of the forest will be possible using tomographic methods from the multi-baseline acquisitions. This is the concept of SAR tomography, which will be implemented in the BIOMASS mission. The improvement in the quantification of the vegetation structure, will have an important impact in many aspects of ecosystem function, such as carbon cycling and biodiversity. For example, areas of forest loss or degradation and areas of growth or recovery, can be determined by the vegetation structure and its temporal change.

Assessing the drivers shaping global patterns of urban vegetation landscape structure.

PubMed

Dobbs, C; Nitschke, C; Kendal, D

2017-08-15

Vegetation is one of the main resources involve in ecosystem functioning and providing ecosystem services in urban areas. Little is known on the landscape structure patterns of vegetation existing in urban areas at the global scale and the drivers of these patterns. We studied the landscape structure of one hundred cities around the globe, and their relation to demography (population), socioeconomic factors (GDP, Gini Index), climate factors (temperature and rain) and topographic characteristics (altitude, variation in altitude). The data revealed that the best descriptors of landscape structure were amount, fragmentation and spatial distribution of vegetation. Populated cities tend to have less, more fragmented, less connected vegetation with a centre of the city with low vegetation cover. Results also provided insights on the influence of socioeconomics at a global scale, as landscape structure was more fragmented in areas that are economically unequal and coming from emergent economies. This study shows the effects of the social system and climate on urban landscape patterns that gives useful insights for the distribution in the provision of ecosystem services in urban areas and therefore the maintenance of human well-being. This information can support local and global policy and planning which is committing our cities to provide accessible and inclusive green space for all urban inhabitants. Copyright © 2017 Elsevier B.V. All rights reserved.

An analysis of the vertical structure equation for arbitrary thermal profiles

NASA Technical Reports Server (NTRS)

Cohn, Stephen E.; Dee, Dick P.

1989-01-01

The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

An analysis of the vertical structure equation for arbitrary thermal profiles

NASA Technical Reports Server (NTRS)

Cohn, Stephen E.; Dee, Dick P.

1987-01-01

The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

Deciphering structural and temporal interplays during the architectural development of mango trees.

PubMed

Dambreville, Anaëlle; Lauri, Pierre-Éric; Trottier, Catherine; Guédon, Yann; Normand, Frédéric

2013-05-01

Plant architecture is commonly defined by the adjacency of organs within the structure and their properties. Few studies consider the effect of endogenous temporal factors, namely phenological factors, on the establishment of plant architecture. This study hypothesized that, in addition to the effect of environmental factors, the observed plant architecture results from both endogenous structural and temporal components, and their interplays. Mango tree, which is characterized by strong phenological asynchronisms within and between trees and by repeated vegetative and reproductive flushes during a growing cycle, was chosen as a plant model. During two consecutive growing cycles, this study described vegetative and reproductive development of 20 trees submitted to the same environmental conditions. Four mango cultivars were considered to assess possible cultivar-specific patterns. Integrative vegetative and reproductive development models incorporating generalized linear models as components were built. These models described the occurrence, intensity, and timing of vegetative and reproductive development at the growth unit scale. This study showed significant interplays between structural and temporal components of plant architectural development at two temporal scales. Within a growing cycle, earliness of bud burst was highly and positively related to earliness of vegetative development and flowering. Between growing cycles, flowering growth units delayed vegetative development compared to growth units that did not flower. These interplays explained how vegetative and reproductive phenological asynchronisms within and between trees were generated and maintained. It is suggested that causation networks involving structural and temporal components may give rise to contrasted tree architectures.

Rapid mapping of ultrafine fault zone topography with structure from motion

USGS Publications Warehouse

Johnson, Kendra; Nissen, Edwin; Saripalli, Srikanth; Arrowsmith, J. Ramón; McGarey, Patrick; Scharer, Katherine M.; Williams, Patrick; Blisniuk, Kimberly

2014-01-01

Structure from Motion (SfM) generates high-resolution topography and coregistered texture (color) from an unstructured set of overlapping photographs taken from varying viewpoints, overcoming many of the cost, time, and logistical limitations of Light Detection and Ranging (LiDAR) and other topographic surveying methods. This paper provides the first investigation of SfM as a tool for mapping fault zone topography in areas of sparse or low-lying vegetation. First, we present a simple, affordable SfM workflow, based on an unmanned helium balloon or motorized glider, an inexpensive camera, and semiautomated software. Second, we illustrate the system at two sites on southern California faults covered by existing airborne or terrestrial LiDAR, enabling a comparative assessment of SfM topography resolution and precision. At the first site, an ∼0.1 km2 alluvial fan on the San Andreas fault, a colored point cloud of density mostly >700 points/m2 and a 3 cm digital elevation model (DEM) and orthophoto were produced from 233 photos collected ∼50 m above ground level. When a few global positioning system ground control points are incorporated, closest point vertical distances to the much sparser (∼4 points/m2) airborne LiDAR point cloud are mostly 530 points/m2 and a 2 cm DEM and orthophoto were produced from 450 photos taken from ∼60 m above ground level. Closest point vertical distances to existing terrestrial LiDAR data of comparable density are mostly <6 cm. Each SfM survey took ∼2 h to complete and several hours to generate the scene topography and texture. SfM greatly facilitates the imaging of subtle geomorphic offsets related to past earthquakes as well as rapid response mapping or long-term monitoring of faulted landscapes.

Combining structure-from-motion derived point clouds from satellites and unmanned aircraft systems images with ground-truth data to create high-resolution digital elevation models

NASA Astrophysics Data System (ADS)

Palaseanu, M.; Thatcher, C.; Danielson, J.; Gesch, D. B.; Poppenga, S.; Kottermair, M.; Jalandoni, A.; Carlson, E.

2016-12-01

Coastal topographic and bathymetric (topobathymetric) data with high spatial resolution (1-meter or better) and high vertical accuracy are needed to assess the vulnerability of Pacific Islands to climate change impacts, including sea level rise. According to the Intergovernmental Panel on Climate Change reports, low-lying atolls in the Pacific Ocean are extremely vulnerable to king tide events, storm surge, tsunamis, and sea-level rise. The lack of coastal topobathymetric data has been identified as a critical data gap for climate vulnerability and adaptation efforts in the Republic of the Marshall Islands (RMI). For Majuro Atoll, home to the largest city of RMI, the only elevation dataset currently available is the Shuttle Radar Topography Mission data which has a 30-meter spatial resolution and 16-meter vertical accuracy (expressed as linear error at 90%). To generate high-resolution digital elevation models (DEMs) in the RMI, elevation information and photographic imagery have been collected from field surveys using GNSS/total station and unmanned aerial vehicles for Structure-from-Motion (SfM) point cloud generation. Digital Globe WorldView II imagery was processed to create SfM point clouds to fill in gaps in the point cloud derived from the higher resolution UAS photos. The combined point cloud data is filtered and classified to bare-earth and georeferenced using the GNSS data acquired on roads and along survey transects perpendicular to the coast. A total station was used to collect elevation data under tree canopies where heavy vegetation cover blocked the view of GNSS satellites. A subset of the GPS / total station data was set aside for error assessment of the resulting DEM.

Examining the sensitivity of modelled evapotranspiration to vegetation structural characteristics within boreal peatlands, riparian ecosystems and upland mixedwood forest

NASA Astrophysics Data System (ADS)

Petrone, R. M.; Chasmer, L. E.; Brown, S. M.; Mendoza, C. A.; Diiwu, J.; Quinton, W. L.; Hopkinson, C.; Devito, K. J.

2010-12-01

The Western Boreal Plain (WBP) of northern Alberta is comprised of a complex mosaic of small ponds, riparian buffer zones, and upland aspen dominated mixedwood forests surrounded by low-lying peatlands. The hydrology of the WBP is strongly influenced by climatic drivers and geology, whereby water budgets are often controlled by vertical fluxes. During most years, potential evapotranspiration (PET) exceeds precipitation (P), and changes in P as a result of climatic change will likely alter actual evapotranspiration (AET) and regional water balances. In recent years, the WBP has also undergone intense anthropogenic disturbance via oil and gas exploration and extraction, and silvicultural and forest harvesting activities. The extent to which changes in land cover types/characteristics affect estimates of PET and AET is currently unknown. This study examines the sensitivity of PET using a simple estimate of equilibrium ET (Priestley-Taylor) and AET (Penman-Monteith variant) to variability in canopy structural and ground surface characteristics at 12 sites throughout the 2008 growing season (June, July, August). Energy balance meteorological stations are deployed within four peatland ecosystems, four riparian buffer zones, two regenerating upland mixedwood forests and two mature upland mixedwood forests. Airborne Light Detection and Ranging (LiDAR) is used to derive metrics of canopy height, leaf area index (LAI), uplands and lowlands, elevation, zero plane displacement, roughness length governing momentum, roughness length governing heat and vapour, and understory vegetation characteristics. LiDAR land surface metrics and energy balance measurements are used to model evapotranspiration for classified land cover types throughout the larger basin. Sensitivity of potential and actual estimates to changes in land cover characteristics within each of the three land cover types (peatland, riparian and upland) is quantified.

Scattering and emission from inhomogeneous vegetation canopy and alien target beneath by using three-dimensional vector radiative transfer (3D-VRT) equation

NASA Astrophysics Data System (ADS)

Jin, Ya-Qiu; Liang, Zichang

2005-05-01

To solve the 3D-VRT equation for the model of spatially inhomogeneous scatter media, the finite enclosure of the scatter media is geometrically divided, in both vertical z and transversal (x,y) directions, to form very thin multi-boxes. The zeroth order emission, first-order Mueller matrix of each thin box and an iterative approach of high-order radiative transfer are applied to derive high-order scattering and emission of whole inhomogeneous scatter media. Numerical results of polarized brightness temperature at microwave frequency and under different radiometer resolutions from inhomogeneous scatter model such as vegetation canopy and alien target beneath canopy are simulated and discussed.

Defining the ecogeomorphic succession of land building for freshwater, intertidal wetlands in Wax Lake Delta, Louisiana

NASA Astrophysics Data System (ADS)

Olliver, Elizabeth A.; Edmonds, Douglas A.

2017-09-01

Land building in deltaic environments occurs when sediment discharged from a river mouth is deposited subaqueously and transitions to subaerial land. The transition from subaqueous deposition to subaerial land is a critical process that marks the creation of relatively stable land, yet it is unclear what controls the speed and style of this transition. We define how this transition, herein termed the land building succession, varies in time and space for the freshwater, intertidal wetlands in Wax Lake Delta, LA. Using remote sensing and field data we classify land cover into sediment, water, or vegetation classes at maximum and minimum biomass. We see two succession patterns within Wax Lake Delta. Deltaic islands near the apex are initially covered by sediment and open water. Through time, open water and sediment coverage decreases as vegetation coverage increases. On the other hand, distal islands show little sediment exposure through time. In both cases, all deltaic islands become covered with vegetation by 2015. As vegetation colonizes the island, the topography organizes into two platforms vertically separated by ∼0.35 m. The lower, intertidal platform occurs in the island interiors and is commonly inundated by water and dominated by subaqueous or floating vegetation. The upper, subaerial platform occurs along island edges and is dominated by a variety of vegetation species including Salix nigra, Colocasia esculenta, and Polygonum punctatum. It takes an average of ∼10 years for the intertidal platform to transition to the subaerial platform. These two platforms are separated by the tidal range measured in Atchafalaya Bay, and the different vegetation communities occupying each platform suggest they are a manifestation of multiple stable states and arise due to vegetation and sedimentation feedbacks.

Improvement of the Raman detection system for pesticide residues on/in fruits and vegetables

NASA Astrophysics Data System (ADS)

Li, Yan; Peng, Yankun; Zhai, Chen; Chao, Kuanglin; Qin, Jianwei

2017-05-01

Pesticide residue is one of the major challenges to fruits safety, while the traditional detection methods of pesticide residue on fruits and vegetables can't afford the demand of rapid detection in actual production because of timeconsuming. Thus rapid identification and detection methods for pesticide residue are urgently needed at present. While most Raman detection systems in the market are spot detection systems, which limits the range of application. In the study, our lab develops a Raman detection system to achieve area-scan thorough the self-developed spot detection Raman system with a control software and two devices. In the system, the scanning area is composed of many scanning spots, which means every spot needs to be detected and more time will be taken than area-scan Raman system. But lower detection limit will be achieved in this method. And some detection device is needed towards fruits and vegetables in different shape. Two detection devices are developed to detect spherical fruits and leaf vegetables. During the detection, the device will make spherical fruit rotate along its axis of symmetry, and leaf vegetables will be pressed in the test surface smoothly. The detection probe will be set to keep a proper distance to the surface of fruits and vegetables. It should make sure the laser shins on the surface of spherical fruit vertically. And two software are used to detect spherical fruits and leaf vegetables will be integrated to one, which make the operator easier to switch. Accordingly two detection devices for spherical fruits and leaf vegetables will also be portable devices to make it easier to change. In the study, a new way is developed to achieve area-scan result by spot-scan Raman detection system.

Effect of vertical canopy architecture on transpiration, thermoregulation and carbon assimilation

DOE PAGES

Banerjee, Tirtha; Linn, Rodman Ray

2018-04-11

Quantifying the impact of natural and anthropogenic disturbances such as deforestation, forest fires and vegetation thinning among others on net ecosystem—atmosphere exchanges of carbon dioxide, water vapor and heat—is an important aspect in the context of modeling global carbon, water and energy cycles. The absence of canopy architectural variation in horizontal and vertical directions is a major source of uncertainty in current climate models attempting to address these issues. This work demonstrates the importance of considering the vertical distribution of foliage density by coupling a leaf level plant biophysics model with analytical solutions of wind flow and light attenuation inmore » a horizontally homogeneous canopy. It is demonstrated that plant physiological response in terms of carbon assimilation, transpiration and canopy surface temperature can be widely different for two canopies with the same leaf area index (LAI) but different leaf area density distributions, under several conditions of wind speed, light availability, soil moisture availability and atmospheric evaporative demand.« less

Effect of vertical canopy architecture on transpiration, thermoregulation and carbon assimilation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Tirtha; Linn, Rodman Ray

Quantifying the impact of natural and anthropogenic disturbances such as deforestation, forest fires and vegetation thinning among others on net ecosystem—atmosphere exchanges of carbon dioxide, water vapor and heat—is an important aspect in the context of modeling global carbon, water and energy cycles. The absence of canopy architectural variation in horizontal and vertical directions is a major source of uncertainty in current climate models attempting to address these issues. This work demonstrates the importance of considering the vertical distribution of foliage density by coupling a leaf level plant biophysics model with analytical solutions of wind flow and light attenuation inmore » a horizontally homogeneous canopy. It is demonstrated that plant physiological response in terms of carbon assimilation, transpiration and canopy surface temperature can be widely different for two canopies with the same leaf area index (LAI) but different leaf area density distributions, under several conditions of wind speed, light availability, soil moisture availability and atmospheric evaporative demand.« less

Modeling Aeolian Transport of Contaminated Sediments at Los Alamos National Laboratory, Technical Area 54, Area G: Sensitivities to Succession, Disturbance, and Future Climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whicker, Jeffrey J.; Kirchner, Thomas B.; Breshears, David D.

2012-03-27

The Technical Area 54 (TA-54) Area G disposal facility is used for the disposal of radioactive waste at Los Alamos National Laboratory (LANL). U.S. Department of Energy (DOE) Order 435.1 (DOE, 2001) requires that radioactive waste be managed in a manner that protects public health and safety and the environment. In compliance with that requirement, DOE field sites must prepare and maintain site-specific radiological performance assessments for facilities that receive waste after September 26, 1988. Sites are also required to conduct composite analyses for facilities that receive waste after this date; these analyses account for the cumulative impacts of allmore » waste that has been (and will be) disposed of at the facilities and other sources of radioactive material that may interact with these facilities. LANL issued Revision 4 of the Area G performance assessment and composite analysis in 2008. In support of those analyses, vertical and horizontal sediment flux data were collected at two analog sites, each with different dominant vegetation characteristics, and used to estimate rates of vertical resuspension and wind erosion for Area G. The results of that investigation indicated that there was no net loss of soil at the disposal site due to wind erosion, and suggested minimal impacts of wind on the long-term performance of the facility. However, that study did not evaluate the potential for contaminant transport caused by the horizontal movement of soil particles over long time frames. Since that time, additional field data have been collected to estimate wind threshold velocities for initiating sediment transport due to saltation and rates of sediment transport once those thresholds are reached. Data such as these have been used in the development of the Vegetation Modified Transport (VMTran) model. This model is designed to estimate patterns and long-term rates of contaminant redistribution caused by winds at the site, taking into account the impacts of plant succession and environmental disturbance. Aeolian, or wind-driven, sediment transport drives soil erosion, affects biogeochemical cycles, and can lead to the transport of contaminants. Rates of aeolian sediment transport depend in large part on the type, amount, and spatial pattern of vegetation. In particular, the amount of cover from trees and shrubs, which act as roughness elements, alters rates of aeolian sediment transport. The degree to which the understory is disturbed and the associated spacing of bare soil gaps further influence sediment transport rates. Changes in vegetation structure and patterns over periods of years to centuries may have profound impacts on rates of wind-driven transport. For recently disturbed areas, succession is likely to occur through a series of vegetation communities. Area G currently exhibits a mosaic of vegetation cover, with patches of grass and forbs over closed disposal units, and bare ground in heavily used portions of the site. These areas are surrounded by less disturbed regions of shrubland and pinon-juniper woodland; some ponderosa pine forest is also visible in the canyon along the road. The successional trajectory for the disturbed portions of Area G is expected to proceed from grasses and forbs (which would be established during site closure), to shrubs such as chamisa, to a climax community of pinon-juniper woodland. Although unlikely under current conditions, a ponderosa pine forest could develop over the site if the future climate is wetter. In many ecosystems, substantial and often periodic disturbances such as fire or severe drought can rapidly alter vegetation patterns. Such disturbances are likely to increase in the southwestern US where projections call for a warmer and drier climate. With respect to Area G, the 3 most likely disturbance types are surface fire, crown fire, and drought-induced tree mortality. Each type of disturbance has a different frequency or likelihood of occurrence, but all 3 tend to reset the vegetation succession cycle to earlier stages. The Area G performance assessment and composite analysis evaluate the impacts of disposing of radioactive waste over a period of hundreds to thousands of years. An assessment of aeolian sediment transport over this timeframe needs to account for the impacts of changes in vegetation structure and other surface conditions that occur under normal circumstances and as a result of environmental disturbance. Recent aeolian sediment transport studies undertaken in diverse dryland systems on both undisturbed and disturbed lands have yielded a suite of empirical measurements. These studies do not take into account changes in long-term conditions at the sites being investigated. Although studies of dune systems have begun to account for different types of vegetation due to succession and the effects of disturbance under current and projected climate, similar information for drylands that are not dominated by dunes is almost entirely lacking.« less

Fluvial islands: First stage of development from nonmigrating (forced) bars and woody-vegetation interactions

NASA Astrophysics Data System (ADS)

Wintenberger, Coraline L.; Rodrigues, Stéphane; Bréhéret, Jean-Gabriel; Villar, Marc

2015-10-01

Fluvial islands can develop from the channel bed by interactions between pioneer trees and bars. Although vegetation recruitment and survival is possible on all bar types, it is easier for trees to survive on nonmigrating bars developed from a change in channel geometry or to the presence of a steady perturbation. This field study details the first stages of development of a vegetated mid-channel, nonmigrating (or forced) bar and its evolution toward an island form. Over six years, analysis of bed topographical changes, vegetation density and roughness, scour and fill depths, sediment grain size and architecture, and excess bed shear stress highlighted a specific signature of trees on topography and grain size segregation. Two depositional processes combining the formation of obstacle marks and upstream-shifting deposition of sediments led to the vertical accretion of the vegetated bar. During the first stage of the bar accretion, bedload sediment supply coming from surrounding channels during floods was identified as a key process modulated by the presence of woody vegetation and a deflection effect induced by the preexisting topography. Grain size segregation between vegetated and bare areas was also highlighted and interpreted as an important process affecting the development of surrounding channels and the degree of disconnection (and hence the speed of development) of a growing island. The heterogeneity of bedload supply can explain why sediment deposition and density of trees are not strictly related. A general conceptual model detailing the first stages of evolution from a bar to an established island is proposed for relatively large lowland rivers.

Coevolution of hydraulic, soil and vegetation processes in estuarine wetlands

NASA Astrophysics Data System (ADS)

Trivisonno, Franco; Rodriguez, Jose F.; Riccardi, Gerardo; Saco, Patricia; Stenta, Hernan

2014-05-01

Estuarine wetlands of south eastern Australia, typically display a vegetation zonation with a sequence mudflats - mangrove forest - saltmarsh plains from the seaward margin and up the topographic gradient. Estuarine wetlands are among the most productive ecosystems in the world, providing unique habitats for fish and many terrestrial species. They also have a carbon sequestration capacity that surpasess terrestrial forest. Estuarine wetlands respond to sea-level rise by vertical accretion and horizontal landward migration, in order to maintain their position in the tidal frame. In situations in which buffer areas for landward migration are not available, saltmarsh can be lost due to mangrove encroachment. As a result of mangrove invasion associated in part with raising estuary water levels and urbanisation, coastal saltmarsh in parts of south-eastern Australia has been declared an endangered ecological community. Predicting estuarine wetlands response to sea-level rise requires modelling the coevolving dynamics of water flow, soil and vegetation. This paper presents preliminary results of our recently developed numerical model for wetland dynamics in wetlands of the Hunter estuary of NSW. The model simulates continuous tidal inflow into the wetland, and accounts for the effect of varying vegetation types on flow resistance. Coevolution effects appear as vegetation types are updated based on their preference to prevailing hydrodynamic conditions. The model also considers that accretion values vary with vegetation type. Simulations are driven using local information collected over several years, which includes estuary water levels, accretion rates, soil carbon content, flow resistance and vegetation preference to hydraulic conditions. Model results predict further saltmarsh loss under current conditions of moderate increase of estuary water levels.

Relative abundance and lengths of Kendall Warm Springs dace captured from different habitats in a specially designed trap

USGS Publications Warehouse

Gryska, A.D.; Hubert, W.A.; Gerow, K.G.

1998-01-01

A trap was designed to capture endangered Kendall Warm Springs dace Rhinichthys osculus thermalis (a subspecies of speckled dace Rhinichthys osculus) without being destructive to the habitat of the fish in Kendall Warm Springs Creek, Wyoming. Four experiments were conducted to determine differences in catch per unit effort (CPUE) and length frequencies of fish among differing habitat types. The CPUE was highest in channel habitats with current, and one experiment indicated that it was particularly high at vertical interfaces with vegetation. Longer fish were captured in channel habitats away from vegetation than in vegetated areas. The CPUE was significantly greater during the day than at night during one experiment, but no significant differences were observed among the other three experiments. The traps were easy and inexpensive to construct, could be used in a variety of stream habitats, and may have applications in other small streams for sampling small, benthic fishes.

Relating geomorphic change and grazing to avian communities in riparian forests

USGS Publications Warehouse

Scott, M.L.; Skagen, S.K.; Merligliano, M.F.

2003-01-01

Avian conservation in riparian or bottomland forests requires an understanding of the physical and biotic factors that sustain the structural complexity of riparian vegetation. Riparian forests of western North America are dependent upon flow-related geomorphic processes necessary for establishment of new cottonwood and willow patches. In June 1995, we examined how fluvial geomorphic processes and long-term grazing influence the structural complexity of riparian vegetation and the abundance and diversity of breeding birds along the upper Missouri River in central Montana, a large, flow-regulated, and geomorphically constrained reach. Use by breeding birds was linked to fluvial geomorphic processes that influence the structure of these patches. Species richness and bird diversity increased with increasing structural complexity of vegetation (F1,32 = 75.49, p < 0.0001; F1,32 = 79.76, p < 0.0001, respectively). Bird species composition was significantly correlated with vegetation strata diversity (rs,33 = 0.98, p < 0.0001). Bird abundance in canopy and tall-shrub foraging guilds increased significantly with increasing tree cover and tall-shrub cover (F1,22 = 34.68, p < 0.0001; F1,20 = 22.22, p < 0.0001, respectively). Seventeen bird species, including five species of concern (e.g., Red-eyed Vireo [Vireo olivaceus]), were significantly associated (p < 0.10) with structurally complex forest patches, whereas only six bird species were significantly associated with structurally simple forest patches. We related the structural complexity of 34 riparian vegetation patches to geomorphic change, woody vegetation establishment, and grazing history over a 35-year post-dam period (1953–1988). The structural complexity of habitat patches was positively related to recent sediment accretion (t33 = 3.31, p = 0.002) and vegetation establishment (t20.7 = −3.63, p = 0.002) and negatively related to grazing activity (t19.6 = 3.75, p = 0.001). Avian conservation along rivers like the upper Missouri requires maintenance of the geomorphic processes responsible for tree establishment and management of land-use activities in riparian forests.

An efficient, self-orienting, vertical-array, sand trap

NASA Astrophysics Data System (ADS)

Hilton, Michael; Nickling, Bill; Wakes, Sarah; Sherman, Douglas; Konlechner, Teresa; Jermy, Mark; Geoghegan, Patrick

2017-04-01

There remains a need for an efficient, low-cost, portable, passive sand trap, which can provide estimates of vertical sand flux over topography and within vegetation and which self-orients into the wind. We present a design for a stacked vertical trap that has been modelled (computational fluid dynamics, CFD) and evaluated in the field and in the wind tunnel. The 'swinging' trap orients to within 10° of the flow in the wind tunnel at 8 m s-1, and more rapidly in the field, where natural variability in wind direction accelerates orientation. The CFD analysis indicates flow is steered into the trap during incident wind flow. The trap has a low profile and there is only a small decrease in mass flow rate for multiple traps, poles and rows of poles. The efficiency of the trap was evaluated against an isokinetic sampler and found to be greater than 95%. The centre pole is a key element of the design, minimally decreasing trap efficiency. Finally, field comparisons with the trap of Sherman et al. (2014) yielded comparable estimates of vertical sand flux. The trap described in this paper provides accurate estimates of sand transport in a wide range of field conditions.

MC1: a dynamic vegetation model for estimating the distribution of vegetation and associated carbon, nutrients, and water—technical documentation. Version 1.0.

Treesearch

Dominique Bachelet; James M. Lenihan; Christopher Daly; Ronald P. Neilson; Dennis S. Ojima; William J. Parton

2001-01-01

Assessments of vegetation response to climate change have generally been made only by equilibrium vegetation models that predict vegetation composition under steady-state conditions. These models do not simulate either ecosystem biogeochemical processes or changes in ecosystem structure that may, in turn, act as feedbacks in determining the dynamics of vegetation...

Small mammal abundance in Mediterranean post-fire habitats: a role for predators?

NASA Astrophysics Data System (ADS)

Torre, I.; Díaz, M.

2004-05-01

We studied patterns of small mammal abundance and species richness in post-fire habitats by sampling 33 plots (225 m 2 each) representing different stages of vegetation recovery after fire. Small mammal abundance was estimated by live trapping during early spring 1999 and vegetation structure was sampled by visual estimation at the same plots. Recently-burnt areas were characterised by shrubby and herbaceous vegetation with low structural variability, and unburnt areas were characterised by well developed forest cover with high structural complexity. Small mammal abundance and species richness decreased with time elapsed since the last fire (from 5 to at least 50 years), and these differences were associated to the decreasing cover of short shrubs as the post-fire succession of plant communities advanced. However, relationships between vegetation structure and small mammals differed among areas burned in different times, with weak or negative relationship in recently burnt areas and positive and stronger relationship in unburnt areas. Furthermore, the abundance of small mammals was larger than expected from vegetation structure in plots burned recently whereas the contrary pattern was found in unburned areas. We hypothesised that the pattern observed could be related to the responses of small mammal predators to changes in vegetation and landscape structure promoted by fire. Fire-related fragmentation could have promoted the isolation of forest predators (owls and carnivores) in unburned forest patches, a fact that could have produced a higher predation pressure for small mammals. Conversely, small mammal populations would have been enhanced in early post-fire stages by lower predator numbers combined with better predator protection in areas covered by resprouting woody vegetation.

Sources of scattering in vegetarian and other surfaces and objects

NASA Technical Reports Server (NTRS)

Moore, R. K.

1988-01-01

The sources of scattering in vegetation and other surfaces and objects were studied. A special radar, SOURCESCAT, that could resolve a cylindrical volume 18 cm in diameter and 11 cm long was built. This system provided the first really fine-resolution measurements of radar backscatter from vegetation. The measurements showed that many of the assumptions used previously in modeling vegetation backscatter were false. Vegetation studied included various field crops, prairie grass, and various trees. Major differences were found in the roles of leaves, branches, stems, and trunks for different species. An artificial tree was studied in the laboratory using the systems. The most significant findings were that the average radar volume scattering coefficient is independent of azimuth, and that slanting of the polarization vector can give useful information not available with ordinary vertical and horizontal polarization. A model for scattering from a single leaf was developed. This model, for the first time, took into account the presence of veins in leaves. The pattern of scatter from a leaf was shown quite different from that for which the veins are ignored. A list of publications and presentations resulting from this project are attached.

Detecting emergence, growth, and senescence of wetland vegetation with polarimetric synthetic aperture radar (SAR) data

USGS Publications Warehouse

Gallant, Alisa L.; Kaya, Shannon G.; White, Lori; Brisco, Brian; Roth, Mark F.; Sadinski, Walter J.; Rover, Jennifer

2014-01-01

Wetlands provide ecosystem goods and services vitally important to humans. Land managers and policymakers working to conserve wetlands require regularly updated information on the statuses of wetlands across the landscape. However, wetlands are challenging to map remotely with high accuracy and consistency. We investigated the use of multitemporal polarimetric synthetic aperture radar (SAR) data acquired with Canada’s Radarsat-2 system to track within-season changes in wetland vegetation and surface water. We speculated, a priori, how temporal and morphological traits of different types of wetland vegetation should respond over a growing season with respect to four energy-scattering mechanisms. We used ground-based monitoring data and other ancillary information to assess the limits and consistency of the SAR data for tracking seasonal changes in wetlands. We found the traits of different types of vertical emergent wetland vegetation were detected well with the SAR data and corresponded with our anticipated backscatter responses. We also found using data from Landsat’s optical/infrared sensors in conjunction with SAR data helped remove confusion of wetland features with upland grasslands. These results suggest SAR data can provide useful monitoring information on the statuses of wetlands over time.

Hydrologic and Vegetative Removal of Cryptosporidium parvum, Giardia lamblia, and Toxoplasma gondii Surrogate Microspheres in Coastal Wetlands

PubMed Central

Hogan, Jennifer N.; Daniels, Miles E.; Watson, Fred G.; Oates, Stori C.; Miller, Melissa A.; Conrad, Patricia A.; Shapiro, Karen; Hardin, Dane; Dominik, Clare; Melli, Ann; Jessup, David A.

2013-01-01

Constructed wetland systems are used to reduce pollutants and pathogens in wastewater effluent, but comparatively little is known about pathogen transport through natural wetland habitats. Fecal protozoans, including Cryptosporidium parvum, Giardia lamblia, and Toxoplasma gondii, are waterborne pathogens of humans and animals, which are carried by surface waters from land-based sources into coastal waters. This study evaluated key factors of coastal wetlands for the reduction of protozoal parasites in surface waters using settling column and recirculating mesocosm tank experiments. Settling column experiments evaluated the effects of salinity, temperature, and water type (“pure” versus “environmental”) on the vertical settling velocities of C. parvum, G. lamblia, and T. gondii surrogates, with salinity and water type found to significantly affect settling of the parasites. The mesocosm tank experiments evaluated the effects of salinity, flow rate, and vegetation parameters on parasite and surrogate counts, with increased salinity and the presence of vegetation found to be significant factors for removal of parasites in a unidirectional transport wetland system. Overall, this study highlights the importance of water type, salinity, and vegetation parameters for pathogen transport within wetland systems, with implications for wetland management, restoration efforts, and coastal water quality. PMID:23315738

Dimensions of vegetable parenting practices among preschoolers.

PubMed

Baranowski, Tom; Chen, Tzu-An; O'Connor, Teresia; Hughes, Sheryl; Beltran, Alicia; Frankel, Leslie; Diep, Cassandra; Baranowski, Janice C

2013-10-01

The objective of this study was to determine the factor structure of 31 effective and ineffective vegetable parenting practices used by parents of preschool children based on three theoretically proposed factors: responsiveness, control and structure. The methods employed included both corrected item-total correlations and confirmatory factor analysis. Acceptable fit was obtained only when effective and ineffective parenting practices were analyzed separately. Among effective items the model included one second order factor (effectiveness) and the three proposed first order factors. The same structure was revealed among ineffective items, but required correlated paths be specified among items. A theoretically specified three factor structure was obtained among 31 vegetable parenting practice items, but likely to be effective and ineffective items had to be analyzed separately. Research is needed on how these parenting practices factors predict child vegetable intake. Copyright © 2013 Elsevier Ltd. All rights reserved.

The importance of vegetation density for tourists' wildlife viewing experience and satisfaction in African savannah ecosystems.

PubMed

Arbieu, Ugo; Grünewald, Claudia; Schleuning, Matthias; Böhning-Gaese, Katrin

2017-01-01

Southern African protected areas (PAs) harbour a great diversity of animals, which represent a large potential for wildlife tourism. In this region, global change is expected to result in vegetation changes, such as bush encroachment and increases in vegetation density. However, little is known on the influence of vegetation structure on wildlife tourists' wildlife viewing experience and satisfaction. In this study, we collected data on vegetation structure and perceived mammal densities along 196 road transects (each 5 km long) and conducted a social survey with 651 questionnaires across four PAs in three Southern African countries. Our objectives were 1) to assess visitors' attitude towards vegetation, 2) to test the influence of perceived mammal density and vegetation structure on the easiness to spot animals, and 3) on visitors' satisfaction during their visit to PAs. Using a Boosted Regression Tree procedure, we found mostly negative non-linear relationships between vegetation density and wildlife tourists' experience, and positive relationships between perceived mammal densities and wildlife tourists' experience. In particular, wildlife tourists disliked road transects with high estimates of vegetation density. Similarly, the easiness to spot animals dropped at thresholds of high vegetation density and at perceived mammal densities lower than 46 individuals per road transect. Finally, tourists' satisfaction declined linearly with vegetation density and dropped at mammal densities smaller than 26 individuals per transect. Our results suggest that vegetation density has important impacts on tourists' wildlife viewing experience and satisfaction. Hence, the management of PAs in savannah landscapes should consider how tourists perceive these landscapes and their mammal diversity in order to maintain and develop a sustainable wildlife tourism.

The importance of vegetation density for tourists’ wildlife viewing experience and satisfaction in African savannah ecosystems

PubMed Central

Grünewald, Claudia; Schleuning, Matthias; Böhning-Gaese, Katrin

2017-01-01

Southern African protected areas (PAs) harbour a great diversity of animals, which represent a large potential for wildlife tourism. In this region, global change is expected to result in vegetation changes, such as bush encroachment and increases in vegetation density. However, little is known on the influence of vegetation structure on wildlife tourists’ wildlife viewing experience and satisfaction. In this study, we collected data on vegetation structure and perceived mammal densities along 196 road transects (each 5 km long) and conducted a social survey with 651 questionnaires across four PAs in three Southern African countries. Our objectives were 1) to assess visitors’ attitude towards vegetation, 2) to test the influence of perceived mammal density and vegetation structure on the easiness to spot animals, and 3) on visitors’ satisfaction during their visit to PAs. Using a Boosted Regression Tree procedure, we found mostly negative non-linear relationships between vegetation density and wildlife tourists’ experience, and positive relationships between perceived mammal densities and wildlife tourists’ experience. In particular, wildlife tourists disliked road transects with high estimates of vegetation density. Similarly, the easiness to spot animals dropped at thresholds of high vegetation density and at perceived mammal densities lower than 46 individuals per road transect. Finally, tourists’ satisfaction declined linearly with vegetation density and dropped at mammal densities smaller than 26 individuals per transect. Our results suggest that vegetation density has important impacts on tourists’ wildlife viewing experience and satisfaction. Hence, the management of PAs in savannah landscapes should consider how tourists perceive these landscapes and their mammal diversity in order to maintain and develop a sustainable wildlife tourism. PMID:28957420

Dip and anisotropy effects on flow using a vertically skewed model grid.

PubMed

Hoaglund, John R; Pollard, David

2003-01-01

Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 < or = theta < or = 90) and gradient directions (0 < or = phi < or = 360). The equations can be coded into ground water models (e.g., MODFLOW) that can use a skewed Cartesian coordinate system to simulate flow in structural terrain with deformed bedding planes. Models modified with these equations will require input arrays of strike and dip, and a solver that can handle off-diagonal hydraulic conductivity terms.

Forest Canopy Processes in a Regional Chemical Transport Model

NASA Astrophysics Data System (ADS)

Makar, Paul; Staebler, Ralf; Akingunola, Ayodeji; Zhang, Junhua; McLinden, Chris; Kharol, Shailesh; Moran, Michael; Robichaud, Alain; Zhang, Leiming; Stroud, Craig; Pabla, Balbir; Cheung, Philip

2016-04-01

Forest canopies have typically been absent or highly parameterized in regional chemical transport models. Some forest-related processes are often considered - for example, biogenic emissions from the forests are included as a flux lower boundary condition on vertical diffusion, as is deposition to vegetation. However, real forest canopies comprise a much more complicated set of processes, at scales below the "transport model-resolved scale" of vertical levels usually employed in regional transport models. Advective and diffusive transport within the forest canopy typically scale with the height of the canopy, and the former process tends to dominate over the latter. Emissions of biogenic hydrocarbons arise from the foliage, which may be located tens of metres above the surface, while emissions of biogenic nitric oxide from decaying plant matter are located at the surface - in contrast to the surface flux boundary condition usually employed in chemical transport models. Deposition, similarly, is usually parameterized as a flux boundary condition, but may be differentiated between fluxes to vegetation and fluxes to the surface when the canopy scale is considered. The chemical environment also changes within forest canopies: shading, temperature, and relativity humidity changes with height within the canopy may influence chemical reaction rates. These processes have been observed in a host of measurement studies, and have been simulated using site-specific one-dimensional forest canopy models. Their influence on regional scale chemistry has been unknown, until now. In this work, we describe the results of the first attempt to include complex canopy processes within a regional chemical transport model (GEM-MACH). The original model core was subdivided into "canopy" and "non-canopy" subdomains. In the former, three additional near-surface layers based on spatially and seasonally varying satellite-derived canopy height and leaf area index were added to the original model structure. Process methodology for deposition, biogenic emissions, shading, vertical diffusion, advection, chemical reactive environment and particle microphysics were modified to account for expected conditions within the forest canopy and the additional layers. The revised and original models were compared for a 10km resolution domain covering North America, for a one-month duration simulation. The canopy processes were found to have a very significant impact on model results. We will present a comparison to network observations which suggests that forest canopy processes may account for previously unexplained local and regional biases in model ozone predictions noted in GEM-MACH and other models. The impact of the canopy processes on NO2, PM2.5, and SO2 performance will also be presented and discussed.

A remote sensing based vegetation classification logic for global land cover analysis

USGS Publications Warehouse

Running, Steven W.; Loveland, Thomas R.; Pierce, Lars L.; Nemani, R.R.; Hunt, E. Raymond

1995-01-01

This article proposes a simple new logic for classifying global vegetation. The critical features of this classification are that 1) it is based on simple, observable, unambiguous characteristics of vegetation structure that are important to ecosystem biogeochemistry and can be measured in the field for validation, 2) the structural characteristics are remotely sensible so that repeatable and efficient global reclassifications of existing vegetation will be possible, and 3) the defined vegetation classes directly translate into the biophysical parameters of interest by global climate and biogeochemical models. A first test of this logic for the continental United States is presented based on an existing 1 km AVHRR normalized difference vegetation index database. Procedures for solving critical remote sensing problems needed to implement the classification are discussed. Also, some inferences from this classification to advanced vegetation biophysical variables such as specific leaf area and photosynthetic capacity useful to global biogeochemical modeling are suggested.

Multiple Scales of Control on the Structure and Spatial Distribution of Woody Vegetation in African Savanna Watersheds

PubMed Central

Vaughn, Nicholas R.; Asner, Gregory P.; Smit, Izak P. J.; Riddel, Edward S.

2015-01-01

Factors controlling savanna woody vegetation structure vary at multiple spatial and temporal scales, and as a consequence, unraveling their combined effects has proven to be a classic challenge in savanna ecology. We used airborne LiDAR (light detection and ranging) to map three-dimensional woody vegetation structure throughout four savanna watersheds, each contrasting in geologic substrate and climate, in Kruger National Park, South Africa. By comparison of the four watersheds, we found that geologic substrate had a stronger effect than climate in determining watershed-scale differences in vegetation structural properties, including cover, height and crown density. Generalized Linear Models were used to assess the spatial distribution of woody vegetation structural properties, including cover, height and crown density, in relation to mapped hydrologic, topographic and fire history traits. For each substrate and climate combination, models incorporating topography, hydrology and fire history explained up to 30% of the remaining variation in woody canopy structure, but inclusion of a spatial autocovariate term further improved model performance. Both crown density and the cover of shorter woody canopies were determined more by unknown factors likely to be changing on smaller spatial scales, such as soil texture, herbivore abundance or fire behavior, than by our mapped regional-scale changes in topography and hydrology. We also detected patterns in spatial covariance at distances up to 50–450 m, depending on watershed and structural metric. Our results suggest that large-scale environmental factors play a smaller role than is often attributed to them in determining woody vegetation structure in southern African savannas. This highlights the need for more spatially-explicit, wide-area analyses using high resolution remote sensing techniques. PMID:26660502

Multiple Scales of Control on the Structure and Spatial Distribution of Woody Vegetation in African Savanna Watersheds.

PubMed

Vaughn, Nicholas R; Asner, Gregory P; Smit, Izak P J; Riddel, Edward S

2015-01-01

Factors controlling savanna woody vegetation structure vary at multiple spatial and temporal scales, and as a consequence, unraveling their combined effects has proven to be a classic challenge in savanna ecology. We used airborne LiDAR (light detection and ranging) to map three-dimensional woody vegetation structure throughout four savanna watersheds, each contrasting in geologic substrate and climate, in Kruger National Park, South Africa. By comparison of the four watersheds, we found that geologic substrate had a stronger effect than climate in determining watershed-scale differences in vegetation structural properties, including cover, height and crown density. Generalized Linear Models were used to assess the spatial distribution of woody vegetation structural properties, including cover, height and crown density, in relation to mapped hydrologic, topographic and fire history traits. For each substrate and climate combination, models incorporating topography, hydrology and fire history explained up to 30% of the remaining variation in woody canopy structure, but inclusion of a spatial autocovariate term further improved model performance. Both crown density and the cover of shorter woody canopies were determined more by unknown factors likely to be changing on smaller spatial scales, such as soil texture, herbivore abundance or fire behavior, than by our mapped regional-scale changes in topography and hydrology. We also detected patterns in spatial covariance at distances up to 50-450 m, depending on watershed and structural metric. Our results suggest that large-scale environmental factors play a smaller role than is often attributed to them in determining woody vegetation structure in southern African savannas. This highlights the need for more spatially-explicit, wide-area analyses using high resolution remote sensing techniques.

Firestorms

DTIC Science & Technology

1982-04-15

Morton 1957)#]. Tropical rainforests in Vietnam are characterized by prevailing relative humidity of 80%; also, dead vegetation decays so rapidly that...wind for the onset of a firestorm raises several points. Tropical cyclones form in environments in which there is little vertical wind shear to cause...of 18-19 April 1965 as a case of a fire occurring in the warm sector of an extra- tropical cyclone (winds of 8-10 m/s, with gusts of 15; airmass

Chapter 6 - Developing the LANDFIRE Vegetation and Biophysical Settings Map Unit Classifications for the LANDFIRE Prototype Project

Treesearch

Jennifer L. Long; Melanie Miller; James P. Menakis; Robert E. Keane

2006-01-01

The Landscape Fire and Resource Management Planning Tools Prototype Project, or LANDFIRE Prototype Project, required a system for classifying vegetation composition, biophysical settings, and vegetation structure to facilitate the mapping of vegetation and wildland fuel characteristics and the simulation of vegetation dynamics using landscape modeling. We developed...

The Geoscience Laser Altimeter System (GLAS) for the ICESAT Mission

NASA Technical Reports Server (NTRS)

Abshire, James B.; Sun, Xia-Li; Ketchum, Eleanor A.; Afzal, Robert S.; Millar, Pamela S.; Smith, David E. (Technical Monitor)

2000-01-01

The Laser In space Technology Experiment, Shuttle Laser Altimeter and the Mars Observer Laser Altimeter have demonstrated accurate measurements of atmospheric backscatter and Surface heights from space. The recent MOLA measurements of the Mars surface have 40 cm vertical resolution and have reduced the global uncertainty in Mars topography from a few km to about 5 m. The Geoscience Laser Altimeter System (GLAS) is a next generation lidar for Earth orbit being developed as part of NASA's Icesat Mission. The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, establish a grid of accurate height profiles of the Earth's land topography, and profile the vertical backscatter of clouds and aerosols on a global scale. GLAS is being developed to fly on a small dedicated spacecraft in a polar orbit with a 590 630 km altitude at inclination of 94 degrees. GLAS is scheduled to launch in the summer 2001 and to operate continuously for a minimum of 3 years with a goal of 5 years. The primary mission for GLAS is to measure the seasonal and annual changes in the heights of the Greenland and Antarctic ice sheets. GLAS will continuously measure the vertical distance from orbit to the Earth's surface with 1064 nm pulses from a ND:YAG laser at a 40 Hz rate. Each 5 nsec wide laser pulse is used to produce a single range measurement, and the laser spots have 66 m diameter and about 170 m center-center spacings. When over land GLAS will profile the heights of the topography and vegetation. The GLAS receiver uses a 1 m diameter telescope and a Si APD detector. The detector signal is sampled by an all digital receiver which records each surface echo waveform with I nsec resolution and a stored echo record lengths of either 200, 400, or 600 samples. Analysis of the echo waveforms within the instrument permits discrimination between cloud and surface echoes. Ground based echo analysis permits precise ranging, determining the roughness or slopes of the surface as well as the vertical distributions of vegetation illuminated by the laser. Accurate knowledge of the laser beam's pointing angle is needed to prevent height biases when over sloped surfaces. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam's centroid to about 8 urad is needed to achieve 10 cm height accuracy. GLAS uses a stellar reference system (SRS) to determine the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith and a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser is measured pulse relative to the star camera with a laser reference system (LRS). Optically measuring each laser far field pattern relative to the orientation of the star camera and gyroscope permits the precise pointing angle of each laser pulse to be determined. GLAS will also determine the vertical distributions of clouds and aerosols by measuring the vertical profile of laser energy backscattered by the atmosphere at both 1064 and 532 nm. The 1064 nm measurements use the Si APD detector and profile the height and vertical structure of thicker clouds. The measurements at 532 nm use new highly sensitive photon counting, detectors, and measure the height distributions of very thin Clouds and aerosol layers. With averaging these can be used to determine the height of the planetary boundary layer. The instrument design and expected performance will be discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, R.D.; Black, R.A.

Growth of vegetative and reproductive structures in Artemisia tridentata is temporally separated during the growing season; vegetative growth occurs during spring and early summer when soil moisture is most abundant, while reproductive growth occurs during summer and fall when soil moisture may be limiting. Vegetative and reproductive structures may exhibit contrasting efficiencies of resource acquisition and investment resulting from temporal differences in resource availability. The effect of water stress on growth, photosynthesis, and resource investment for vegetative and reproductive modules of Artemisia tridentata was examined by applying supplemental water. No differences were observed in vegetative biomass in the two wateringmore » treatments. Growth of vegetative structures occurred in the spring when water was not limiting, and shrubs in both treatments exerted little stomatal control over water loss. Conversely, supplemental watering increased reproductive growth. Shrubs conserved water during summer by abscising leaves and lowering stomatal conductance potential and increases in evaporative demand. In florescences are capable of positive photosynthetic rates comparable to vegetative leaves. Water stress did not alter tissue construction costs or carbon and nitrogen contents for either vegetative or reproductive modules. Resource limitations were reflected in the efficiency of water use during tissue construction; floral leaves and floral heads of shrubs not receiving supplemental water were produced with higher water-use efficiency. Conservative use of water during production of vegetative modules would offer no advantage because neighboring species are also most active at this time. Reproductive growth in A. tridentata occurs during summer when neighboring species are largely dormant, and so efficient use of water may allow development of reproductive structures to continue throughout the summer even with limited supplies of water. 66 refs., 8 figs., 3 tabs.« less

Predictive mapping of forest composition and structure with direct gradient analysis and nearest neighbor imputation in coastal Oregon, U.S.A.

Treesearch

Janet L. Ohmann; Matthew J. Gregory

2002-01-01

Spatially explicit information on the species composition and structure of forest vegetation is needed at broad spatial scales for natural resource policy analysis and ecological research. We present a method for predictive vegetation mapping that applies direct gradient analysis and nearest-neighbor imputation to ascribe detailed ground attributes of vegetation to...

Small clusters of fast-growing trees enhance forest structure on restored bottomland sites

USGS Publications Warehouse

Twedt, D.J.

2006-01-01

Despite the diversity of trees in bottomland forests, restoration on bottomland sites is often initiated by planting only a few species of slow-growing, hard mast?producing trees. Although successful at establishing trees, these young forests are slow to develop vertical structure, which is a key predictor of forest bird colonization. Furthermore, when natural seed sources are few, restored sites may be depauperate in woody species. To increase richness of woody species, maximum tree height, and total stem density, I supplemented traditional plantings on each of 40 bottomland restoration sites by planting 96 Eastern cottonwood (Populus deltoides) and American sycamore (Platanus occidentalis) in eight clusters of 12 trees. First year survival of cottonwood stem cuttings (25%) and sycamore seedlings (47%) was poor, but survival increased when afforded protection from competition with weeds. After five growing seasons, 165 of these 320 supplemental tree clusters had at least one surviving tree. Vegetation surrounding surviving clusters of supplemental trees harbored a greater number of woody species, increased stem density, and greater maximum tree height than was found on paired restoration sites without supplemental trees. These increases were primarily accounted for by the supplemental trees.

A Laboratory Study of Vortical Structures in Rotating Convection Plumes

NASA Astrophysics Data System (ADS)

Fu, Hao; Sun, Shiwei; Wang, Yuan; Zhou, Bowen; Thermal Turbulence Research Team

2015-11-01

A laboratory study of the columnar vortex structure in rotating Rayleigh-Bénard convection is conducted. A rectangular water tank is uniformly heated from below and cooled from above, with Ra = (6 . 35 +/- 0 . 77) ×107 , Ta = 9 . 84 ×107 , Pr = 7 . 34 . The columnar vortices are vertically aligned and quasi steady. Two 2D PIV systems were used to measure velocity field. One system performs horizontal scans at 9 different heights every 13.6s, covering 62% of the total depth. The other system scans vertically to obtain the vertical velocity profile. The measured vertical vorticity profiles of most vortices are quasi-linear with height while the vertical velocities are nearly uniform with only a small curvature. A simple model to deduce vertical velocity profile from vertical vorticity profile is proposed. Under quasi-steady and axisymmetric conditions, a ``vortex core'' assumption is introduced to simplify vertical vorticity equation. A linear ODE about vertical velocity is obtained whenever a vertical vorticity profile is given and solved with experimental data as input. The result is approximately in agreement with the measurement. This work was supported by Undergraduates Training Project (J1103410).

Determining the vertical carbon dioxide source/sink distribution in a mountain pine beetle attacked forest: A comparison of eddy-covariance and ecophysiological approaches

NASA Astrophysics Data System (ADS)

Emmel, C.; Bowler, R.; Black, T. A.; Christen, A.

2012-12-01

Disturbance of forests caused by insect attacks, such as the mountain pine beetle (Dendroctonus ponderosae, MPB) outbreak in Western North America may lead to a conversion of affected forests from a net carbon dioxide (CO2) sink to a net source. Informed management of forests can help reduce the associated CO2 emissions. The objective of this study is to determine the vertical distribution of sources and sinks of CO2 in an open MPB attacked lodgepole pine (Pinus contorta var. latifolia) canopy (stand height h = 17 m, leaf areas index LAI = 0.55 m2 m-2) in the Interior of British Columbia. The stand has a considerable living secondary structure with a maximum height of 12 m while 99% of the mature pine trees composing the upper canopy are dead. We compared two different methods to accomplish the goal of determining the vertical divergence of the CO2 flux and relate it to the different vegetation layers. Data from a field campaign in July / August 2010 were used. The first method employs eddy-covariance (EC) measurements to determine the vertical source/sink distribution within and above the canopy. The instrumentation included open-path infrared gas analyzers and 3D ultrasonic anemometers. With simultaneous EC measurements at seven heights (z/h = 0.05, 0.15, 0.40, 0.60, 0.85, 1.05 and 1.30) we determined the CO2 uptake or release of the layers between the measurement levels by calculating the flux density divergence and the CO2 storage change in the air of each layer. The second method uses an ecophysiological approach developing a canopy CO2 exchange model. CO2 exchange was directly measured on tree boles and the soil using a portable non-steady-state CO2 chamber system and on leaves using a LI-COR LI-6400 photosynthesis system. Measurements were made during different times of the day and under varying temperature and moisture conditions over the course of the campaign. Airborne light detection and ranging (LIDAR) measurements, and vertical, horizontal and species-specific LAI measurements provided necessary information about the stand structure. We combined this information with measurements of photosynthetically active radiation (PAR) at 6 levels, soil moisture and temperature measurements to model the vertical CO2 source/sink distribution over the course of the campaign. In earlier research, it was found that this stand made the transition from a carbon source to a sink faster than expected (Brown et al., 2010, Agric For Meteorol 150, 254-264). The flux profile showed substantial daytime CO2 uptake below z/h = 0.5, while in the upper canopy there was respiratory CO2 loss. PAR penetrates deep into the canopy with on average almost 60% reaching the ground level (z/h = 0.05). Our study demonstrates that the secondary structure is responsible for significant CO2 uptake, while the understory together with the soil and the dead lodgepole pine trees in the upper canopy are weak CO2 sources, resulting in the stand being a carbon sink. We will discuss the strengths and weaknesses of the two proposed methods with regard to technical challenges and uncertainties, and how the two methods compared overall.

Morchella tomentosa: a unique belowground structure and a new clade of morels

Treesearch

Franck O.P. Stefani; Serge Sokolski; Trish L. Wurtz; Yves Piché; Richard C. Hamelin; J. André Fortin; Jean A. Bérubé

2010-01-01

Mechanisms involved in post-fire morel fructification remain unclear. A new undescribed belowground vegetative structure of Marchella tomentosa in a burned boreal forest was investigated north of Fairbanks, Alaska. The name "radiscisclerotium" is proposed to define this peculiar and elaborate belowground vegetative structure of ...

How Efficient is Vegetation in Reducing Wind Erosion and Emission of Health-Threatening Fine Dust PM10? - A Wind Tunnel Approach

NASA Astrophysics Data System (ADS)

Burri, K.; Graf, F.

2009-04-01

World wide, wind erosion and desertification are most alarming processes of environmental degradation. Not only do they cause tremendous losses of fertile soil, but they also seriously affect human health. Pulmonary tuberculosis (silicosis) is one of the major diseases that have been linked to mineral fine dust (PM10) in the atmosphere. It is widely accepted that the re-establishment of an intact vegetation cover is the most effective measure against wind erosion. However, despite numerous investigations, the mechanisms responsible for the protective effect of vegetation are still not completely understood. Since the phenomenon involves highly variable interactions between soil, plants and atmosphere, it is particularly difficult to quantify the efficiency of vegetation in reducing wind erosion. As an alternative to field investigations, wind tunnel experiments offer the advantage to control specific parameters within this highly complex system. In this study, a series of wind tunnel experiments was performed including measurements of sediment transport and PM10 emission in differently dense grass canopies of Lolium perenne (91, 24, 5 and 0 plants per square meter). The novelty of the present wind tunnel study is the use of living plants instead of artificial imitations or dead plant parts. Although more and more sophisticated imitations of vegetation have been used in recent studies, the behaviour of living plants is likely to differ significantly. Coloured quartz sand was used for visualizing sand erosion and deposition patterns. The vertical profiles of aeolian sediment flux were analysed with a stackable sediment sampler composed of 60 collecting boxes, each with a height of 1 cm. The results of this study confirm that both sediment transport and PM10 emission strongly decrease with increasing plant cover. The protective effect of the plants was found to be linked to characteristic changes in the vertical profile of aeolian sediment flux and to specific spatial patterns of sediment deposition. Furthermore, observations indicate that the performance of plants in wind erosion control strongly depends on plant species specific characteristics, particularly growth form and stiffness, as well as on their physiological state. The use of living plants in wind tunnel experiments offers the possibility to study a wide range of more specific aspects of biological wind erosion control. As a next step it is planned to test the effect of mycorrhizal fungi on the wind erodibility of vegetated soil systems.

Advantages of a Vertical High-Resolution Distributed-Temperature-Sensing System Used to Evaluate the Thermal Behavior of Green Roofs

NASA Astrophysics Data System (ADS)

Hausner, M. B.; Suarez, F. I.; Cousiño, J. A.; Victorero, F.; Bonilla, C. A.; Gironas, J. A.; Vera, S.; Bustamante, W.; Rojas, V.; Leiva, E.; Pasten, P.

2015-12-01

Technological innovations used for sustainable urban development, green roofs offer a range of benefits, including reduced heat island effect, rooftop runoff, roof surface temperatures, energy consumption, and noise levels inside buildings, as well as increased urban biodiversity. Green roofs feature layered construction, with the most important layers being the vegetation and the substrate layers located above the traditional roof. These layers provide both insulation and warm season cooling by latent heat flux, reducing the thermal load to the building. To understand and improve the processes driving this thermal energy reduction, it is important to observe the thermal dynamics of a green roof at the appropriate spatial and temporal scales. Traditionally, to observe the thermal behavior of green roofs, a series of thermocouples have been installed at discrete depths within the layers of the roof. Here, we present a vertical high-resolution distributed-temperature-sensing (DTS) system installed in different green roof modules of the Laboratory of Vegetated Infrastructure for Buildings (LIVE -its acronym in Spanish) of the Pontifical Catholic University of Chile. This DTS system allows near-continuous measurement of the thermal profile at spatial and temporal resolutions of approximately 1 cm and 30 s, respectively. In this investigation, the temperature observations from the DTS system are compared with the measurements of a series of thermocouples installed in the green roofs. This comparison makes it possible to assess the value of thermal observations at better spatial and temporal resolutions. We show that the errors associated with lower resolution observations (i.e., from the thermocouples) are propagated in the calculations of the heat fluxes through the different layers of the green roof. Our results highlight the value of having a vertical high-resolution DTS system to observe the thermal dynamics in green roofs.

Stratigraphic, sedimentologic, and dendrogeomorphic analyses of rapid floodplain formation along the Rio Grande in Big Bend National Park, Texas

USGS Publications Warehouse

Dean, D.J.; Scott, M.L.; Shafroth, P.B.; Schmidt, J.C.

2011-01-01

The channel of the lower Rio Grande in the Big Bend region rapidly narrows during years of low mean and peak flow. We conducted stratigraphic, sedimentologic, and dendrogeomorphic analyses within two long floodplain trenches to precisely reconstruct the timing and processes of recent floodplain formation. We show that the channel of the Rio Grande narrowed through the oblique and vertical accretion of inset floodplains following channel-widening floods in 1978 and 1990-1991. Vertical accretion occurred at high rates, ranging from 16 to 35 cm/yr. Dendrogeomorphic analyses show that the onset of channel narrowing occurred during low-flow years when channel bars obliquely and vertically accreted fine sediment. This initial stage of accretion occurred by both bedload and suspended-load deposition within the active channel. Vegetation became established on top of these fine-grained deposits during years of low peak flow and stabilized these developing surfaces. Subsequent deposition by moderate floods (between 1.5 and 7 yr recurrence intervals) caused additional accretion at rapid rates. Suspended-sediment deposition was dominant in the upper deposits, resulting in the formation of natural levees at the channel margins and the deposition of horizontally bedded, fining-upward deposits in the floodplain trough. Overall, channel narrowing and floodplain formation occurred through an evolution from active-channel to floodplain depositional processes. High-resolution dendrogeomorphic analyses provide the ability to specifically correlate the flow record to the onset of narrowing, the establishment of riparian vegetation, the formation of natural levees, and ultimately, the conversion of portions of the active channel to floodplains. ?? 2011 Geological Society of America.

The role of the implementation angle of cuttings of Phyllanthus sellowianus as a reference for a soil protection measure against surface erosion

NASA Astrophysics Data System (ADS)

Rauch, H. P.; Sutili, F. J.; Aschbacher, M.; Müller, B.

2009-04-01

Cutting plantation is a very common method of soil bioengineering techniques. The potential of vegetative reproduction is used to install a vegetation cover on eroded slopes to prevent surface erosion. The development of above and below biomass from parts of the stock plant in a very short time and the fast and easy propagation are one of the most important advantages of this soil bioengineering type. Several handbooks (Schiechtl, 1992; Florineth, 2004 and Zeh, 2007) suggest potential plants for vegetative reproduction and describe the procedure of plantation in detail. It is recommended that the cuttings are not driven vertically into the ground. A flat implementation angle guarantees a more uniform rooting of the cutting part driven into the soil, however there are no systematically investigations of the impact of the implementation angle on the biomass performance and consequently on the performance as a surface erosion protection measure. This paper shows results from field investigations focusing on the problem of the impact of the implementation angle of cuttings. In sum 75 specimens of the species of Phyllanthus sellowianus. The plant species was recommended as a native potential soil bioengineering plant by Sutili (s. Sutili, 2006). The cuttings were planted with an average length of 50 cm and diameter of 2 cm. The implementation angle differences between 90 (vertical) 45 and 10 degree. Two months after plantation all plants were excavated and the relevant plant data sets were collected in order to analyse the biomass performance. The field investigations are part of an integrated research project of the University of Natural Resources and Applied Life Sciences, Vienna and the Federal University of Santa Maria, Rio Grande do Sul - Brazil.

Prokaryotes in salt marsh sediments of Ria de Aveiro: Effects of halophyte vegetation on abundance and diversity

NASA Astrophysics Data System (ADS)

Oliveira, Vanessa; Santos, Ana L.; Aguiar, Claúdia; Santos, Luisa; Salvador, Ângelo C.; Gomes, Newton C. M.; Silva, Helena; Rocha, Sílvia M.; Almeida, Adelaide; Cunha, Ângela

2012-09-01

The aim of this study was to investigate the influence of monospecific colonization of sediment stands by Spartina maritima or Halimione portulacoides on benthic prokaryote assemblages in a salt marsh located in Ria de Aveiro (Portugal). The distribution of Bacteria, Archaea and sulfate-reducing bacteria (SRB) in sediments with monospecific plant stands and in unvegetated sediments was characterized by Fluorescence In Situ Hybridization (FISH). Total prokaryote abundance (0.4 × 109-1.7 × 109 cells gdw-1) was highest in sediments from the surface layer. The domain Bacteria comprised approximately 40% of total prokaryote communities with the highest percentages occurring in the surface layer. Archaeal cells corresponded to an average of 25% of total prokaryote population, with higher abundance in the vegetation banks, and displaying homogeneous vertical distribution. The relative abundance of SRB represented approximately 3% of total 4', 6-diamidino-2-phenylindole dihydrochloride (DAPI) stained cells at unvegetated sediment and H. portulacoides stand and 7% at S. maritima stand. Headspace solid-phase microextraction (HS-SPME) combined with Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry (GC × GC-ToFMS) was used to analyse the volatile and semi-volatile fraction of root exudates. A total of 171 compounds were identified and Principal Component Analysis showed a clear separation between the chemical composition (volatile and semi-volatile organic compounds) of the exudates of the two plants. The patterns of vertical distribution and differences in the proportion of SRB and Archaea in the prokaryote communities developing in sediments colonized by Spartina maritima or Halimione portulacoides suggest the existence of plant-specific interactions between halophyte vegetation and estuarine sediment bacteria in Ria de Aveiro salt marshes, exerted via sediment lithology and root-derived exudates.

Organizing the pantry: cache management improves quality of overwinter food stores in a montane mammal

USGS Publications Warehouse

Jakopak, Rhiannon P.; Hall, L. Embere; Chalfoun, Anna D.

2017-01-01

Many mammals create food stores to enhance overwinter survival in seasonal environments. Strategic arrangement of food within caches may facilitate the physical integrity of the cache or improve access to high-quality food to ensure that cached resources meet future nutritional demands. We used the American pika (Ochotona princeps), a food-caching lagomorph, to evaluate variation in haypile (cache) structure (i.e., horizontal layering by plant functional group) in Wyoming, United States. Fifty-five percent of 62 haypiles contained at least 2 discrete layers of vegetation. Adults and juveniles layered haypiles in similar proportions. The probability of layering increased with haypile volume, but not haypile number per individual or nearby forage diversity. Vegetation cached in layered haypiles was also higher in nitrogen compared to vegetation in unlayered piles. We found that American pikas frequently structured their food caches, structured caches were larger, and the cached vegetation in structured piles was of higher nutritional quality. Improving access to stable, high-quality vegetation in haypiles, a critical overwinter food resource, may allow individuals to better persist amidst harsh conditions.

Mapping Vegetation Structure in Kakadu National Park: An AIRSAR and GIS Application in Conservation

NASA Technical Reports Server (NTRS)

Imhoff, Marc L.; Sisk, Thomas D.; Hampton, Haydee; Milne, Anthony K.

1999-01-01

Airborne Synthetic Aperture Radar (AIRSAR) data were used to map vegetation structure in Kakadu National Park Australia as part of the PACRIM project. SAR data were co-registered with Landsat TM, aerial photos, and map data in a geographic information system for a small test area consisting of mangrove, floodplain grasslands, lowland tropical evergreen forest and upland mixed deciduous and evergreen tropical forest near the South Alligator River. Landsat (Thematic Mapper) TM very clearly showed the floristic composition and burn scars from the previous years fires and the AIRSAR data provided a profile of vegetation structure. Extensive field data on vegetation species composition and structure were collected across a series of transects in cooperation with a survey of avifauna in an effort to link the habitat edge structure with bird species responses. A test site was found that contained two types of habitat edges: 1) A structure specific edge - characterized by the appearance of a very strong structural change in the forest canopy occurring in the absence of a substantial turnover in floristics. 2) Floristic edge - a sharp transition in vegetation genetic composition with a mixed set of structural changes. Specific polarization combinations were selected that were highly correlated to a set of desired structural parameters found in the field data. Classification routines were employed to group radar pixels into 3 structural classes based on: the Surface Area to Volume ratio (SA/V) of the stems, the SA/V of the branches, and the leaf area index of the canopy. Separate canopy structure maps were then entered into the GIS and bird responses were observed relative to the classes and their boundaries. Follow-on work will consist of extending this approach to neighboring areas, generating structure maps, predicting bird responses across the edges, and make accuracy assessments.

Effects of riparian vegetation on topographic change during a large flood event, Rio Puerco, New Mexico, USA

USGS Publications Warehouse

Perignon, M. C.; Tucker, G.E.; Griffin, Eleanor R.; Friedman, Jonathan M.

2013-01-01

The spatial distribution of riparian vegetation can strongly influence the geomorphic evolution of dryland rivers during large floods. We present the results of an airborne lidar differencing study that quantifies the topographic change that occurred along a 12 km reach of the Lower Rio Puerco, New Mexico, during an extreme event in 2006. Extensive erosion of the channel banks took place immediately upstream of the study area, where tamarisk and sandbar willow had been removed. Within the densely vegetated study reach, we measure a net volumetric change of 578,050 ± ∼ 490,000 m3, with 88.3% of the total aggradation occurring along the floodplain and channel and 76.7% of the erosion focusing on the vertical valley walls. The sediment derived from the devegetated reach deposited within the first 3.6 km of the study area, with depth decaying exponentially with distance downstream. Elsewhere, floodplain sediments were primarily sourced from the erosion of valley walls. Superimposed on this pattern are the effects of vegetation and valley morphology on sediment transport. Sediment thickness is seen to be uniform among sandbar willows and highly variable within tamarisk groves. These reach-scale patterns of sedimentation observed in the lidar differencing likely reflect complex interactions of vegetation, flow, and sediment at the scale of patches to individual plants.

The Dependence of Peat Soil Hydraulic Conductivity on Dominant Vegetation Type in Mountain Fens

NASA Astrophysics Data System (ADS)

Crockett, A. C.; Ronayne, M. J.; Cooper, D. J.

2014-12-01

The peat soil within fen wetlands provides water storage that can substantially influence the hydrology of mountain watersheds. In this study, we investigated the relationship between hydraulic conductivity and vegetation type for fens occurring in Rocky Mountain National Park (RMNP), Colorado, USA. Vegetation in RMNP fens can be dominated by woody plants and shrubs, such as willows; by mosses; or by herbaceous plants such as sedges. Fens dominated by each vegetation type were selected for study. Six fens were investigated, all of which are in the Colorado River watershed on the west side of RMNP. For each site, soil hydraulic conductivity was measured at multiple locations using a single-ring infiltrometer. As a result of the shallow water table in these fens (the water table was always within 10 cm of the surface), horizontal hydraulic gradients were produced during the field tests. The measured infiltration rates were analyzed using the numerical model HYDRUS. In order to determine the hydraulic conductivity, a parameter estimation problem was solved using HYDRUS as the forward simulator. Horizontal flow was explicitly accounted for in the model. This approach produced more accurate estimates of hydraulic conductivity than would be obtained using an analytical solution that assumes strictly vertical flow. Significant differences in hydraulic properties between fens appear to result at least in part from the effects of different dominant vegetation types on peat soil formation.

Lunar vertical-shaft mining system

NASA Technical Reports Server (NTRS)

Introne, Steven D. (Editor); Krause, Roy; Williams, Erik; Baskette, Keith; Martich, Frederick; Weaver, Brad; Meve, Jeff; Alexander, Kyle; Dailey, Ron; White, Matt

1994-01-01

This report proposes a method that will allow lunar vertical-shaft mining. Lunar mining allows the exploitation of mineral resources imbedded within the surface. The proposed lunar vertical-shaft mining system is comprised of five subsystems: structure, materials handling, drilling, mining, and planning. The structure provides support for the exploration and mining equipment in the lunar environment. The materials handling subsystem moves mined material outside the structure and mining and drilling equipment inside the structure. The drilling process bores into the surface for the purpose of collecting soil samples, inserting transducer probes, or locating ore deposits. Once the ore deposits are discovered and pinpointed, mining operations bring the ore to the surface. The final subsystem is planning, which involves the construction of the mining structure.

A vegetation mapping strategy for conifer forests by combining airborne LiDAR data and aerial imagery

Treesearch

Yanjun Su; Qinghua Guo; Danny L. Fry; Brandon M. Collins; Maggi Kelly; Jacob P. Flanagan; John J. Battles

2016-01-01

Abstract. Accurate vegetation mapping is critical for natural resources management, ecological analysis, and hydrological modeling, among other tasks. Remotely sensed multispectral and hyperspectral imageries have proved to be valuable inputs to the vegetation mapping process, but they can provide only limited vegetation structure...

Hydroecological factors governing surface water flow on a low-gradient floodplain

USGS Publications Warehouse

Harvey, J.W.; Schaffranek, R.W.; Noe, G.B.; Larsen, L.G.; Nowacki, D.J.; O'Connor, B.L.

2009-01-01

Interrelationships between hydrology and aquatic ecosystems are better understood in streams and rivers compared to their surrounding floodplains. Our goal was to characterize the hydrology of the Everglades ridge and slough floodplain ecosystem, which is valued for the comparatively high biodiversity and connectivity of its parallel-drainage features but which has been degraded over the past century in response to flow reductions associated with flood control. We measured flow velocity, water depth, and wind velocity continuously for 3 years in an area of the Everglades with well-preserved parallel-drainage features (i.e., 200-m wide sloughs interspersed with slightly higher elevation and more densely vegetated ridges). Mean daily flow velocity averaged 0.32 cm s-1 and ranged between 0.02 and 0.79 cm s-1. Highest sustained velocities were associated with flow pulses caused by water releases from upstream hydraulic control structures that increased flow velocity by a factor of 2-3 on the floodplain for weeks at a time. The highest instantaneous measurements of flow velocity were associated with the passage of Hurricane Wilma in 2005 when the inverse barometric pressure effect increased flow velocity up to 5 cm s-1 for several hours. Time-averaged flow velocities were 29% greater in sloughs compared to ridges because of marginally higher vegetative drag in ridges compared to sloughs, which contributed modestly (relative to greater water depth and flow duration in sloughs compared to ridges) to the predominant fraction (86%) of total discharge through the landscape occurring in sloughs. Univariate scaling relationships developed from theory of flow through vegetation, and our field data indicated that flow velocity increases with the square of water surface slope and the fourth power of stem diameter, decreases in direct proportion with increasing frontal area of vegetation, and is unrelated to water depth except for the influence that water depth has in controlling the submergence height of vegetation that varies vertically in its architectural characteristics. In the Everglades the result of interactions among controlling variables was that flow velocity was dominantly controlled by water surface slope variations responding to flow pulses more than spatial variation in vegetation characteristics or fluctuating water depth. Our findings indicate that floodplain managers could, in addition to managing water depth, manipulate the frequency and duration of inflow pulses to manage water surface slope, which would add further control over flow velocities, water residence times, sediment settling, biogeochemical transformations, and other processes that are important to floodplain function. ?? 2009 by American Geophysical Union.

Functional and Structural Optimality in Plant Growth: A Crop Modelling Case Study

NASA Astrophysics Data System (ADS)

Caldararu, S.; Purves, D. W.; Smith, M. J.

2014-12-01

Simple mechanistic models of vegetation processes are essential both to our understanding of plant behaviour and to our ability to predict future changes in vegetation. One concept that can take us closer to such models is that of plant optimality, the hypothesis that plants aim to achieve an optimal state. Conceptually, plant optimality can be either structural or functional optimality. A structural constraint would mean that plants aim to achieve a certain structural characteristic such as an allometric relationship or nutrient content that allows optimal function. A functional condition refers to plants achieving optimal functionality, in most cases by maximising carbon gain. Functional optimality conditions are applied on shorter time scales and lead to higher plasticity, making plants more adaptable to changes in their environment. In contrast, structural constraints are optimal given the specific environmental conditions that plants are adapted to and offer less flexibility. We exemplify these concepts using a simple model of crop growth. The model represents annual cycles of growth from sowing date to harvest, including both vegetative and reproductive growth and phenology. Structural constraints to growth are represented as an optimal C:N ratio in all plant organs, which drives allocation throughout the vegetative growing stage. Reproductive phenology - i.e. the onset of flowering and grain filling - is determined by a functional optimality condition in the form of maximising final seed mass, so that vegetative growth stops when the plant reaches maximum nitrogen or carbon uptake. We investigate the plants' response to variations in environmental conditions within these two optimality constraints and show that final yield is most affected by changes during vegetative growth which affect the structural constraint.

Multispectral imaging with vertical silicon nanowires

PubMed Central

Park, Hyunsung; Crozier, Kenneth B.

2013-01-01

Multispectral imaging is a powerful tool that extends the capabilities of the human eye. However, multispectral imaging systems generally are expensive and bulky, and multiple exposures are needed. Here, we report the demonstration of a compact multispectral imaging system that uses vertical silicon nanowires to realize a filter array. Multiple filter functions covering visible to near-infrared (NIR) wavelengths are simultaneously defined in a single lithography step using a single material (silicon). Nanowires are then etched and embedded into polydimethylsiloxane (PDMS), thereby realizing a device with eight filter functions. By attaching it to a monochrome silicon image sensor, we successfully realize an all-silicon multispectral imaging system. We demonstrate visible and NIR imaging. We show that the latter is highly sensitive to vegetation and furthermore enables imaging through objects opaque to the eye. PMID:23955156

On the Vertical Structure of Seasonal, Interannual and Intraseasonal Flows

DTIC Science & Technology

1992-12-01

regions. Extensive use is made of a primitive equation (PE) model, as a diagnostic tool, to explore the extent to which tropical heating might influence ...vertical modes, while Wiin-Nielsen (1971a and b) studied the time 2 behaviour of long waves for various vertical structures. More recent investigations...nonlinear three-leve PE model, are used to determine the influence of tropical heating on extratropica wave response. In Chapter 4, the interannual changes

Territory and nest site selection patterns by Grasshopper Sparrows in southeastern Arizona

USGS Publications Warehouse

Ruth, Janet M.; Skagen, Susan K.

2017-01-01

Grassland bird populations are showing some of the greatest rates of decline of any North American birds, prompting measures to protect and improve important habitat. We assessed how vegetation structure and composition, habitat features often targeted for management, affected territory and nest site selection by Grasshopper Sparrows (Ammodramus savannarum ammolegus) in southeastern Arizona. To identify features important to males establishing territories, we compared vegetation characteristics of known territories and random samples on 2 sites over 5 years. We examined habitat selection patterns of females by comparing characteristics of nest sites with territories over 3 years. Males selected territories in areas of sparser vegetation structure and more tall shrubs (>2 m) than random plots on the site with low shrub densities. Males did not select territories based on the proportion of exotic grasses. Females generally located nest sites in areas with lower small shrub (1–2 m tall) densities than territories overall when possible and preferentially selected native grasses for nest construction. Whether habitat selection was apparent depended upon the range of vegetation structure that was available. We identified an upper threshold above which grass structure seemed to be too high and dense for Grasshopper Sparrows. Our results suggest that some management that reduces vegetative structure may benefit this species in desert grasslands at the nest and territory scale. However, we did not assess initial male habitat selection at a broader landscape scale where their selection patterns may be different and could be influenced by vegetation density and structure outside the range of values sampled in this study.

Arthropod vertical stratification in temperate deciduous forests: Implications for conservation oriented management

Treesearch

Ulyshen Michael

2011-01-01

Studies on the vertical distribution patterns of arthropods in temperate deciduous forests reveal highly stratified (i.e., unevenly vertically distributed) communities. These patterns are determined by multiple factors acting simultaneously, including: (1) time (forest age, season, time of day); (2) forest structure (height, vertical foliage complexity, plant surface...

Simulation study of disruption characteristics in KSTAR

NASA Astrophysics Data System (ADS)

Lee, Jongkyu; Kim, J. Y.; Kessel, C. E.; Poli, F.

2012-10-01

A detailed simulation study of disruption in KSTAR had been performed using the Tokamak Simulation Code(TSC) [1] during the initial design phase of KSTAR [2]. Recently, however, a partial modification in the structure of passive plate was made in relation to reduce eddy current and increase the efficiency of control of vertical position. A substantial change can then occur in disruption characteristics and plasma behavior during disruption due to changes in passive plate structure. Because of this, growth rate of vertical instability is expected to be increased and eddy current and its associated electomagnetic force are expected to be reduced. To check this in more detail, a new simulation study is here given with modified passive plate structure of KSTAR. In particular, modeling of vertical disruption that is vertical displacement event (VDE) was carried out. We calculated vertical growth rate for a drift phase of plasma and electromagnetic force acting on PFC structures and compared the results between in a new model and an old model. [4pt] [1] S.C. Jardin, N. Pomphrey and J. Delucia, J. Comp. Phys. 66, 481 (1986).[0pt] [2] J.Y. Kim, S.Y. Cho and KSTAR Team, Disruption load analysis on KSTAR PFC structures, J. Accel. Plasma Res. 5, 149 (2000).

The influence of roadside solid and vegetation barriers on near-road air quality

NASA Astrophysics Data System (ADS)

Ghasemian, Masoud; Amini, Seyedmorteza; Princevac, Marko

2017-12-01

The current study evaluates the influence of roadside solid and vegetation barriers on the near-road air quality. Reynolds Averaged Navier-Stokes (RANS) technique coupled with the k - ε realizable turbulence model is utilized to investigate the flow pattern and pollutant concentration. A scalar transport equation is solved for a tracer gas to represent the roadway pollutant emissions. In addition, a broad range of turbulent Schmidt numbers are tested to calibrate the scalar transport equation. Three main scenarios including flat terrain, solid barrier, and vegetative barrier are studied. To validate numerical methodology, predicted pollutant concentration is compared with published wind tunnel data. Results show that the solid barrier induces an updraft motion and lofts the vehicle emission plume. Therefore, the ground-level pollutant concentration decreases compared to the flat terrain. For the vegetation barrier, different sub-scenarios with different vegetation densities ranging from approximately flat terrain to nearly solid barrier are examined. Dense canopies act in a similar manner as a solid barrier and mitigate the pollutant concentration through vertical mixing. On the other hand, the high porosity vegetation barriers reduce the wind speed and lead to a higher pollutant concentration. As the vegetation density increases, i.e. the barrier porosity decreases, the recirculation zone behind the canopy becomes larger and moves toward the canopy. The dense plant canopy with LAD = 3.33m-2m3 can improve the near-road air quality by 10% and high porosity canopy with LAD = 1m-2m3 deteriorates near-road air quality by 15%. The results of this study can be implemented as green infrastructure design strategies by urban planners and forestry organizations.

Riparian vegetation and its water use during 1995 along the Mojave River, Southern California

USGS Publications Warehouse

Lines, Gregory C.; Bilhorn, Thomas W.

1996-01-01

The extent and areal density of riparian vegetation, including both phreatophytes and hydrophytes, were mapped along the 100-mile main stem of the Mojave River during 1995. Mapping was aided by vertical false-color infrared and low-level oblique photographs. However, positive identification of plant species and plant physiological stress required field examination. The consumptive use of ground water and surface water by different areal densities of riparian plant communities along the main stem of the Mojave River was estimated using water-use data from a select group of studies in the southwestern United States. In the Alto subarea of the Mojave basin management area, consumptive water use during 1995 by riparian vegetation was estimated to be about 5,000 acre-feet upstream from the Lower Narrows and about 6,000 acre-feet downstream in the transition zone. In the Centro and Baja subareas, consumptive water use was estimated to be about 3,000 acre-feet and 2,000 acre-feet, respectively, during 1995. Consumptive water use by riparian vegetation in the Afton area, downstream from the Baja subarea, was estimated to be about 600 acre-feet during 1995. Consumptive water use by riparian vegetation during 1995 is considered representative of "normal" hydrologic conditions along the Mojave River. Barring major changes in the areal extent and density of riparian vegetation, the 1995 consumptive-use estimates should be fairly representative of riparian vegetation water use during most years. Annual consumptive use, however, could vary from the 1995 estimates as much as plus or minus 50 percent because of extreme hydrologic conditions (periods of high water table following extraordinarily large runoff in the Mojave River or periods of extended drought).

The national fire and fire surrogate study: vegetation changes over 11 years of fuel reduction treatments in the southern Appalachian Mountains

Treesearch

Thomas A. Waldrop; Helen H. Mohr; Ross J. Phillips; Dean M. Simon

2014-01-01

At the Appalachian site of the National Fire and Fire Surrogate Study, prescribed burning was repeated three times and chainsaw felling of shrubs was done twice between 2002 and 2012. Goals were to reduce fuel loading and to promote restoration of an open woodland community. Chainsaw felling created a vertical fuel break, but the effect was temporary, and no...

Remote sensing of vegetation 3-D structure for biodiversity and habitat: Review and implications for lidar and radar spaceborne missions

NASA Astrophysics Data System (ADS)

Bergen, K. M.; Goetz, S. J.; Dubayah, R. O.; Henebry, G. M.; Hunsaker, C. T.; Imhoff, M. L.; Nelson, R. F.; Parker, G. G.; Radeloff, V. C.

2009-06-01

Biodiversity and habitat face increasing pressures due to human and natural influences that alter vegetation structure. Because of the inherent difficulty of measuring forested vegetation three-dimensional (3-D) structure on the ground, this important component of biodiversity and habitat has been, until recently, largely restricted to local measurements, or at larger scales to generalizations. New lidar and radar remote sensing instruments such as those proposed for spaceborne missions will provide the capability to fill this gap. This paper reviews the state of the art for incorporatinginformation on vegetation 3-D structure into biodiversity and habitat science and management approaches, with emphasis on use of lidar and radar data. First we review relationships between vegetation 3-D structure, biodiversity and habitat, and metrics commonly used to describe those relationships. Next, we review the technical capabilities of new lidar and radar sensors and their application to biodiversity and habitat studies to date. We then define variables that have been identified as both useful and feasible to retrieve from spaceborne lidar and radar observations and provide their accuracy and precision requirements. We conclude with a brief discussion of implications for spaceborne missions and research programs. The possibility to derive vegetation 3-D measurements from spaceborne active sensors and to integrate them into science and management comes at a critical juncture for global biodiversity conservation and opens new possibilities for advanced scientific analysis of habitat and biodiversity.

Canopy structure on forest lands in western Oregon: differences among forest types and stand ages

Treesearch

Anne C.S. McIntosh; Andrew N. Gray; Steven L. Garman

2009-01-01

Canopy structure is an important attribute affecting economic and ecological values of forests in the Pacific Northwest. However, canopy cover and vertical layering are rarely measured directly; they are usually inferred from other forest measurements. In this study, we quantified and compared vertical and horizontal patterns of tree canopy structure and understory...

The influence of vertical and horizontal habitat structure on nationwide patterns of avian biodiversity

Treesearch

Patrick D. Culbert; Volker C. Radeloff; Curtis H. Flather; Josef M. Kellndorfer; Chadwick D. Rittenhouse; Anna M. Pidgeon

2013-01-01

With limited resources for habitat conservation, the accurate identification of high-value avian habitat is crucial. Habitat structure affects avian biodiversity but is difficult to quantify over broad extents. Our goal was to identify which measures of vertical and horizontal habitat structure are most strongly related to patterns of avian biodiversity across the...

Light Competition and Carbon Partitioning-Allocation in an improved Forest Ecosystem Model

NASA Astrophysics Data System (ADS)

Collalti, Alessio; Santini, Monia; Valentini Valentini, Riccardo

2010-05-01

In Italy about 100.000 km2 are covered by forests. This surface is the 30% of the whole national land and this shows how the forests are important both for socio-economic and for environmental aspects. Forests changes affect a delicate balance that involve not only vegetation components but also bio-geochemical cycles and global climate. The knowledge of the amount of Carbon sequestered by forests represents a precious information for their sustainable management in the framework of climate changes. Primary studies in terms of model about this important issue, has been done through Forest Ecosystem Model (FEM), well known and validated as 3PG (Landsberg et Waring, 1997; Sands 2004). It is based on light use efficiency approach at the canopy level. The present study started from the original model 3PG, producing an improved version that uses many of explicit formulations of all relevant ecophysiological processes but makes it able to be applied for natural forests. The mutual interaction of forest growth and light conditions causes vertical and horizontal differentiation in the natural forest mosaic. Only ecophysiological parameters which can be either directly measured or estimates with reasonable certainty are used. The model has been written in C language and has been created considering a tri-dimensional cell structure with different vertical layers depending on the forest type that has to be simulated. This 3PG 'improved' version enable to work on multi-layer and multi-species forests type with cell resolution of one hectare for the typical Italian forest species. The multi-layer version is the result of the implementation and development of Lambert-Beer law for the estimation of intercepted, absorbed and transmitted light through different storeys of the forest. It is possible estimates, for each storey, a Par value (Photosynthetic Active Radiation) through Leaf Area Index (LAI), Light Extinction Coefficient and cell Canopy Cover using a "Big Leaf" approach. Hence, the presence of a cohort in a storey determines the amount of light received for the photosynthetic processes. The population density (numbers of trees per cell) represents a good competition index for determining the tree crown structure and tree crown dimension within a forest population. The tree crown tend to branch out horizontally to intercept as much light as possible. The model assess the structure of the tree crown both vertically and horizontally on the base of the population density and it up-scales the result to the whole stand. The canopy depth and the percentage of horizontal coverage determines moreover a crowding competition index that lead to a specific biomass partitioning-allocation ratio among the different tree components (foliage, roots and stem) and especially for the stem affecting Height-Diameter (at breast height) ratio. In this model, Height-Diameter ratio is used as an alternative competition index in determining the vigour and the strength of competition on free growth status of trees. The forest dominant vegetative cover affects moreover the presence of a dominated layer, it influences its yield and its Carbon stocking capacity and hence it influences the forest ecosystem CO2 carbon balance. From this model it is possible to simulate the impact of Climate Change on forests, the feedback of one or more dominated layers in terms of CO2 uptake in a forest stand and the effects of forest management activities for the next years.

Taxel-addressable matrix of vertical nanowire piezotronic transistors

DOEpatents

Wang, Zhong Lin; Wu, Wenzhuo; Wen, Xiaonan

2015-05-05

A tactile sensing matrix includes a substrate, a first plurality of elongated electrode structures, a plurality of vertically aligned piezoelectric members, an insulating layer infused into the piezoelectric members and a second plurality of elongated electrode structures. The first plurality of elongated electrode structures is disposed on the substrate along a first orientation. The vertically aligned piezoelectric members is disposed on the first plurality of elongated electrode structures and form a matrix having columns of piezoelectric members disposed along the first orientation and rows of piezoelectric members disposed along a second orientation that is transverse to the first orientation. The second plurality of elongated electrode structures is disposed on the insulating layer along the second orientation. The elongated electrode structures form a Schottky contact with the piezoelectric members. When pressure is applied to the piezoelectric members, current flow therethrough is modulated.

Characterizing Woody Vegetation Spectral and Structural Parameters with a 3-D Scene Model

NASA Astrophysics Data System (ADS)

Qin, W.; Yang, L.

2004-05-01

Quantification of structural and biophysical parameters of woody vegetation is of great significance in understanding vegetation condition, dynamics and functionality. Such information over a landscape scale is crucial for global and regional land cover characterization, global carbon-cycle research, forest resource inventories, and fire fuel estimation. While great efforts and progress have been made in mapping general land cover types over large area, at present, the ability to quantify regional woody vegetation structural and biophysical parameters is limited. One approach to address this research issue is through an integration of physically based 3-D scene model with multiangle and multispectral remote sensing data and in-situ measurements. The first step of this work is to model woody vegetation structure and its radiation regime using a physically based 3-D scene model and field data, before a robust operational algorithm can be developed for retrieval of important woody vegetation structural/biophysical parameters. In this study, we use an advanced 3-D scene model recently developed by Qin and Gerstl (2000), based on L-systems and radiosity theories. This 3-D scene model has been successfully applied to semi-arid shrubland to study structure and radiation regime at a regional scale. We apply this 3-D scene model to a more complicated and heterogeneous forest environment dominated by deciduous and coniferous trees. The data used in this study are from a field campaign conducted by NASA in a portion of the Superior National Forest (SNF) near Ely, Minnesota during the summers of 1983 and 1984, and supplement data collected during our revisit to the same area of SNF in summer of 2003. The model is first validated with reflectance measurements at different scales (ground observations, helicopter, aircraft, and satellite). Then its ability to characterize the structural and spectral parameters of the forest scene is evaluated. Based on the results from this study and the current multi-spectral and multi-angular satellite data (MODIS, MISR), a robust retrieval system to estimate woody vegetation structural/biophysical parameters is proposed.

Landsat 8 and ICESat-2: Performance and potential synergies for quantifying dryland ecosystem vegetation cover and biomass

USGS Publications Warehouse

Glenn, Nancy F.; Neuenschwander, Amy; Vierling, Lee A.; Spaete, Lucas; Li, Aihua; Shinneman, Douglas; Pilliod, David S.; Arkle, Robert; McIlroy, Susan

2016-01-01

To estimate the potential synergies of OLI and ICESat-2 we used simulated ICESat-2 photon data to predict vegetation structure. In a shrubland environment with a vegetation mean height of 1 m and mean vegetation cover of 33%, vegetation photons are able to explain nearly 50% of the variance in vegetation height. These results, and those from a comparison site, suggest that a lower detection threshold of ICESat-2 may be in the range of 30% canopy cover and roughly 1 m height in comparable dryland environments and these detection thresholds could be used to combine future ICESat-2 photon data with OLI spectral data for improved vegetation structure. Overall, the synergistic use of Landsat 8 and ICESat-2 may improve estimates of above-ground biomass and carbon storage in drylands that meet these minimum thresholds, increasing our ability to monitor drylands for fuel loading and the potential to sequester carbon.

Dimensions of vegetable parenting practices among preschoolers

USDA-ARS?s Scientific Manuscript database

The objective of this study was to determine the factor structure of 31 effective and ineffective vegetable parenting practices used by parents of preschool children based on three theoretically proposed factors: responsiveness, control, and structure. The methods employed included both corrected it...

Vegetation Change in Blue Oak Woodlands in California

Treesearch

Barbara A. Holzman; Barbara H. Allen-Diaz

1991-01-01

A preliminary report of a statewide project investigating vegetation change in blue oak (Quercus douglasii) woodlands in California is presented. Vegetation plots taken in the 1930s, as part of a statewide vegetation mapping project, were relocated and surveyed. Species composition, cover and tree stand structure data from the earlier study were...

Dynamics of Vegetatin Indices in Tropical and Subtropical Savannas Defined by Ecoregions and Moderate Resolution Imaging Spectoradiometer (MODIS) Land Cover

NASA Technical Reports Server (NTRS)

Hill, Michael J.; Roman, Miguel O.; Schaaf, Crytal B.

2011-01-01

In this study, we explored the capacity of vegetation indices derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance products to characterize global savannas in Australia, Africa and South America. The savannas were spatially defined and subdivided using the World Wildlife Fund (WWF) global ecoregions and MODIS land cover classes. Average annual profiles of Normalized Difference Vegetation Index, shortwave infrared ratio (SWIR32), White Sky Albedo (WSA) and the Structural Scattering Index (SSI) were created. Metrics derived from average annual profiles of vegetation indices were used to classify savanna ecoregions. The response spaces between vegetation indices were used to examine the potential to derive structural and fractional cover measures. The ecoregions showed distinct temporal profiles and formed groups with similar structural properties, including higher levels of woody vegetation, similar forest savanna mixtures and similar grassland predominance. The potential benefits from the use of combinations of indices to characterize savannas are discussed.

Sidewall patterning—a new wafer-scale method for accurate patterning of vertical silicon structures

NASA Astrophysics Data System (ADS)

Westerik, P. J.; Vijselaar, W. J. C.; Berenschot, J. W.; Tas, N. R.; Huskens, J.; Gardeniers, J. G. E.

2018-01-01

For the definition of wafer scale micro- and nanostructures, in-plane geometry is usually controlled by optical lithography. However, options for precisely patterning structures in the out-of-plane direction are much more limited. In this paper we present a versatile self-aligned technique that allows for reproducible sub-micrometer resolution local modification along vertical silicon sidewalls. Instead of optical lithography, this method makes smart use of inclined ion beam etching to selectively etch the top parts of structures, and controlled retraction of a conformal layer to define a hard mask in the vertical direction. The top, bottom or middle part of a structure could be selectively exposed, and it was shown that these exposed regions can, for example, be selectively covered with a catalyst, doped, or structured further.

MARS: A protein family involved in the formation of vertical skeletal elements.

PubMed

Abehsera, Shai; Peles, Shani; Tynyakov, Jenny; Bentov, Shmuel; Aflalo, Eliahu D; Li, Shihao; Li, Fuhua; Xiang, Jianhai; Sagi, Amir

2017-05-01

Vertical organizations of skeletal elements are found in various vertebrate teeth and invertebrate exoskeletons. The molecular mechanism behind the development of such structural organizations is poorly known, although it is generally held that organic matrix proteins play an essential role. While most crustacean cuticular organizations exhibit horizontal chitinous layering, a typical vertical organization is found towards the surface of the teeth in the mandibles of the crayfish Cherax quadricarinatus. Candidate genes encoding for mandible-forming structural proteins were mined in C. quadricarinatus molt-related transcriptomic libraries by using a binary patterning approach. A new protein family, termed the Mandible Alanine Rich Structural (MARS) protein family, with a modular sequence design predicted to form fibers, was found. Investigations of spatial and temporal expression of the different MARS genes suggested specific expression in the mandibular teeth-forming epithelium, particularly during the formation of the chitinous vertical organization. MARS loss-of-function RNAi experiments resulted in the collapse of the organization of the chitin fibers oriented vertically to the surface of the crayfish mandibular incisor tooth. A general search of transcriptomic libraries suggested conservation of MARS proteins across a wide array of crustaceans. Our results provide a first look into the molecular mechanism used to build the complex crustacean mandible and into the specialized vertical structural solution that has evolved in skeletal elements. Copyright © 2017 Elsevier Inc. All rights reserved.

Integrated vegetation management (IVM) for INDOT roadsides.

DOT National Transportation Integrated Search

2014-03-01

With over 90,000 miles of road in Indiana, it is important that adjoining vegetation be maintained for safety concerns, road structure : maintenance and aesthetics. Mowing is currently the main form of vegetation management on INDOT (Indiana Departme...

Data and methods comparing social structure and vegetation structure of urban neighborhoods in Baltimore, Maryland

Treesearch

J. Morgan Grove; Mary L. Cadenasso; William R., Jr. Burch; Steward T. Pickett; Kirsten Schwarz; Jarlath O' Neil-Dunne; Matthew Wilson; Austin Troy; Christopher Boone

2006-01-01

Recent advances in remote sensing and the adoption of geographic information systems (GIS) have greatly increased the availibility of high-resolution spatial and attribute data for examing the relationship between social and vegetation structure in urban areas. There are several motivations for understanding this relationship. First, the United States has experienced a...

Health professionals' and dietetics practitioners' perceived effectiveness of fruit and vegetable parenting practices across six countries.

PubMed

O'Connor, Teresia; Watson, Kathy; Hughes, Sheryl; Beltran, Alicia; Hingle, Melanie; Baranowski, Janice; Campbell, Karen; Canal, Dolors Juvinyà; Lizaur, Ana Bertha Pérez; Zacarías, Isabel; González, Daniela; Nicklas, Theresa; Baranowski, Tom

2010-07-01

Fruit and vegetable intake may reduce the risk of some chronic diseases. However, many children consume less-than-recommended amounts of fruit and vegetables. Because health professionals and dietetics practitioners often work with parents to increase children's fruit and vegetable intake, assessing their opinions about the effectiveness of parenting practices is an important step in understanding how to promote fruit and vegetable intake among preschool-aged children. Using a cross-sectional design, collaborators from six countries distributed an Internet survey to health and nutrition organization members. A self-selected sample reported their perceptions of the effectiveness of 39 parenting practices intended to promote fruit and vegetable consumption in preschool-aged children from May 18, 2008, to September 16, 2008. A total of 889 participants (55% United States, 22.6% Mexico, 10.9% Australia, 4.4% Spain, 3.3% Chile, 2.2% United Kingdom, and 1.6% other countries) completed the survey. The fruit and vegetable intake-related parenting practices items were categorized into three dimensions (structure, responsiveness, and control) based on a parenting theory conceptual framework and dichotomized as effective/ineffective based on professional perceptions. The theoretically derived factor structures for effective and ineffective parenting practices were evaluated using separate confirmatory factor analyses and demonstrated acceptable fit. Fruit and vegetable intake-related parenting practices that provide external control were perceived as ineffective or counterproductive, whereas fruit and vegetable intake-related parenting practices that provided structure, nondirective control, and were responsive were perceived as effective in getting preschool-aged children to consume fruit and vegetables. Future research needs to develop and validate a parent-reported measure of these fruit and vegetable intake-related parenting practices and to empirically evaluate the effect of parental use of the parenting practices on child fruit and vegetable consumption. Copyright 2010 American Dietetic Association. Published by Elsevier Inc. All rights reserved.

The Geoscience Laser Altimeter System (GLAS) for the ICESAT Mission

NASA Technical Reports Server (NTRS)

Abshire, James B.; Sun, Xiao-Li; Ketchum, Eleanor A.; Afzal, Robert S.; Millar, Pamela S.

1999-01-01

Accurate measurements of surface heights and atmospheric backscatter have been demonstrated with the SLA, MOLA and LITE space lidar. Recent MOLA measurements of the Mars surface have 40 cm resolution and have reduced the global uncertainty in Mars topography from a few km to approx. 10 m. GLAS is a next generation lidar being developed as part of NASA's Icesat Mission for Earth orbit . The GLAS design combines a 10 cm precision surface lidar with a sensitive dual wavelength cloud and aerosol lidar. GLAS will precisely measure the heights of the Earth's polar ice sheets, determine the height profiles of the Earth's land topography, and profile the vertical backscatter of clouds and aerosols on a global scale. GLAS will fly on a small dedicated spacecraft in a polar orbit at 598 km altitude with an inclination of 94 degrees. GLAS is scheduled to launch in summer 2001 and to operate continuously for a minimum of 3 years with a goal of 5 years. The primary mission for GLAS is to measure the seasonal and annual changes in the heights of the Greenland and Antarctic ice sheets. GLAS will measure the vertical distance to the ice sheet from orbit with 1064 nm pulses from a Nd:Yag laser at 40 Hz. Each 5 nsec wide laser pulse is used for a single range measurement. When over land GLAS will profile the heights of the topography and vegetation. The GLAS receiver uses a I m diameter telescope and a Si APD detector. The detector signal is sampled by an all digital receiver which records each surface echo waveform with I nsec resolution and a stored echo record lengths of either 200, 400, or 600 samples. Analysis of the echo waveforms within the instrument permits discrimination between cloud and surface echoes. Ground based echo analysis permits precise ranging, determining the roughness or slopes of the surface as well as the vertical distributions of vegetation illuminated by the laser, Errors in knowledge of the laser beam pointing angle can bias height measurements of sloped surfaces. For surfaces with 2 deg. slopes, knowledge of pointing angle of the beam centroid to about 8 urad is required to achieve 10 cm height accuracy. GLAS uses a stellar reference system (SRS) to determine the pointing angle of each laser firing relative to inertial space. The SRS uses a high precision star camera oriented toward local zenith whose measurements are combined with a gyroscope to determine the inertial orientation of the SRS optical bench. The far field pattern of each laser pulse is measured with a laser reference system (LRS). Optically measuring each laser far field pattern relative to the star camera and gyroscope permits the angular offsets of each laser pulse to be determined. GLAS will also determine the vertical distributions of clouds and aerosols by measuring atmospheric backscatter profiles at both 1064 and 532 nm. The 1064 nm measurements use an analog detector and profile the height and vertical structure of thicker clouds. Measurements at 532 nm use new highly sensitive photon counting detectors, and measure the height distributions of very thin clouds and aerosol layers. With averaging these can be used to determine the height of the planetary boundary layer. The instrument design and expected performance will be discussed.

Simulations of Seasonal and Latitudinal Variations in Leaf Inclination Angle Distribution: Implications for Remote Sensing

NASA Technical Reports Server (NTRS)

Huemmrich, Karl F.

2013-01-01

The leaf inclination angle distribution (LAD) is an important characteristic of vegetation canopy structure affecting light interception within the canopy. However, LADs are difficult and time consuming to measure. To examine possible global patterns of LAD and their implications in remote sensing, a model was developed to predict leaf angles within canopies. Canopies were simulated using the SAIL radiative transfer model combined with a simple photosynthesis model. This model calculated leaf inclination angles for horizontal layers of leaves within the canopy by choosing the leaf inclination angle that maximized production over a day in each layer. LADs were calculated for five latitude bands for spring and summer solar declinations. Three distinct LAD types emerged: tropical, boreal, and an intermediate temperate distribution. In tropical LAD, the upper layers have a leaf angle around 35 with the lower layers having horizontal inclination angles. While the boreal LAD has vertical leaf inclination angles throughout the canopy. The latitude bands where each LAD type occurred changed with the seasons. The different LADs affected the fraction of absorbed photosynthetically active radiation (fAPAR) and Normalized Difference Vegetation Index (NDVI) with similar relationships between fAPAR and leaf area index (LAI), but different relationships between NDVI and LAI for the different LAD types. These differences resulted in significantly different relationships between NDVI and fAPAR for each LAD type. Since leaf inclination angles affect light interception, variations in LAD also affect the estimation of leaf area based on transmittance of light or lidar returns.

Analysis of vortical structures in turbulent natural convection

NASA Astrophysics Data System (ADS)

Park, Sangro; Lee, Changhoon

2014-11-01

Natural convection of fluid within two parallel walls, Rayleigh-Bénard convection, is studied by direct numerical simulation using a spectral method. The flow is in soft turbulence regime with Rayleigh number 106, 107, 108, Prandtl number 0 . 7 and aspect ratio 4. We investigate the relations between thermal plumes and vortical structures through manipulating the evolution equations of vorticity and velocity gradient tensor. According to simulation results, horizontal vorticity occurs near the wall and changes into vertical vorticity by vertical stretching of fluid element which is caused by vertical movement of the thermal plume. Additionally, eigenvalues, eigenvectors and invariants of velocity gradient tensor show the topologies of vortical structures, including how vortical structures are tilted or stretched. Difference of velocity gradient tensor between inside thermal plumes and background region is also investigated, and the result indicates that thermal plumes play an important role in changing the distribution of vortical structures. The results of this study are consistent with other researches which suggest that vertical vorticity is stronger in high Rayleigh number flows. Details will be presented in the meeting.

Quantification of LiDAR measurement uncertainty through propagation of errors due to sensor sub-systems and terrain morphology

NASA Astrophysics Data System (ADS)

Goulden, T.; Hopkinson, C.

2013-12-01

The quantification of LiDAR sensor measurement uncertainty is important for evaluating the quality of derived DEM products, compiling risk assessment of management decisions based from LiDAR information, and enhancing LiDAR mission planning capabilities. Current quality assurance estimates of LiDAR measurement uncertainty are limited to post-survey empirical assessments or vendor estimates from commercial literature. Empirical evidence can provide valuable information for the performance of the sensor in validated areas; however, it cannot characterize the spatial distribution of measurement uncertainty throughout the extensive coverage of typical LiDAR surveys. Vendor advertised error estimates are often restricted to strict and optimal survey conditions, resulting in idealized values. Numerical modeling of individual pulse uncertainty provides an alternative method for estimating LiDAR measurement uncertainty. LiDAR measurement uncertainty is theoretically assumed to fall into three distinct categories, 1) sensor sub-system errors, 2) terrain influences, and 3) vegetative influences. This research details the procedures for numerical modeling of measurement uncertainty from the sensor sub-system (GPS, IMU, laser scanner, laser ranger) and terrain influences. Results show that errors tend to increase as the laser scan angle, altitude or laser beam incidence angle increase. An experimental survey over a flat and paved runway site, performed with an Optech ALTM 3100 sensor, showed an increase in modeled vertical errors of 5 cm, at a nadir scan orientation, to 8 cm at scan edges; for an aircraft altitude of 1200 m and half scan angle of 15°. In a survey with the same sensor, at a highly sloped glacial basin site absent of vegetation, modeled vertical errors reached over 2 m. Validation of error models within the glacial environment, over three separate flight lines, respectively showed 100%, 85%, and 75% of elevation residuals fell below error predictions. Future work in LiDAR sensor measurement uncertainty must focus on the development of vegetative error models to create more robust error prediction algorithms. To achieve this objective, comprehensive empirical exploratory analysis is recommended to relate vegetative parameters to observed errors.

Physics Parameterization for Seasonal Prediction

DTIC Science & Technology

2013-09-30

particularly the Madden Julian Oscillation (MJO). We are continuing our participation in the project “Vertical Structure and Diabatic Processes of...Results are shown for: a) TRMM rainfall, b) NAVGEM 20-year run submitted for the YOTC/GEWEX project “Vertical Structure and Diabatic Processes of the MJO

The influence of air-filled structures on wave propagation and beam formation of a pygmy sperm whale (Kogia breviceps) in horizontal and vertical planes.

PubMed

Song, Zhongchang; Zhang, Yu; Thornton, Steven W; Li, Songhai; Dong, Jianchen

2017-10-01

The wave propagation, sound field, and transmission beam pattern of a pygmy sperm whale (Kogia breviceps) were investigated in both the horizontal and vertical planes. Results suggested that the signals obtained at both planes were similarly characterized with a high peak frequency and a relatively narrow bandwidth, close to the ones recorded from live animals. The sound beam measured outside the head in the vertical plane was narrower than that of the horizontal one. Cases with different combinations of air-filled structures in both planes were used to study the respective roles in controlling wave propagation and beam formation. The wave propagations and beam patterns in the horizontal and vertical planes elucidated the important reflection effect of the spermaceti and vocal chambers on sound waves, which was highly significant in forming intensive forward sound beams. The air-filled structures, the forehead soft tissues and skull structures formed wave guides in these two planes for emitted sounds to propagate forward.

Characterization and classification of vegetation canopy structure and distribution within the Great Smoky Mountains National Park using LiDAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Jitendra; HargroveJr., William Walter; Norman, Steven P

Vegetation canopy structure is a critically important habit characteristic for many threatened and endangered birds and other animal species, and it is key information needed by forest and wildlife managers for monitoring and managing forest resources, conservation planning and fostering biodiversity. Advances in Light Detection and Ranging (LiDAR) technologies have enabled remote sensing-based studies of vegetation canopies by capturing three-dimensional structures, yielding information not available in two-dimensional images of the landscape pro- vided by traditional multi-spectral remote sensing platforms. However, the large volume data sets produced by airborne LiDAR instruments pose a significant computational challenge, requiring algorithms to identify andmore » analyze patterns of interest buried within LiDAR point clouds in a computationally efficient manner, utilizing state-of-art computing infrastructure. We developed and applied a computationally efficient approach to analyze a large volume of LiDAR data and to characterize and map the vegetation canopy structures for 139,859 hectares (540 sq. miles) in the Great Smoky Mountains National Park. This study helps improve our understanding of the distribution of vegetation and animal habitats in this extremely diverse ecosystem.« less

Vertical distributions of fluorescent aerosol over the Eastern U.S.

NASA Astrophysics Data System (ADS)

Perring, A. E.; Robinson, E. S.; Schwarz, J. P.; Gao, R. S.

2016-12-01

The prevalence of bioaerosol in the atmosphere is relevant to atmospheric chemistry, microbial ecology and climate. These particles can act as effective cloud condensation nuclei (CCN) and ice nuclei (IN), representing a potential feedback between vegetation and precipitation. As bioaerosol frequently account for a substantial fraction of coarse mode aerosol in the boundary layer, they may have significant impacts on mixed-phase and/or cirrus cloud formation and climate. Very few measurements are available, however, to constrain loadings of bioaerosol in the free troposphere. Here we present vertical profiles of fluorescent aerosol concentration as a proxy for bioaerosol. The data were obtained over the eastern U.S. during the summer of 2016 using a Wide Band Integrated Bioaerosol Sensor (WIBS) installed aboard a NOAA Twin Otter research aircraft. The airspeed and inlet configuration were chosen to permit efficient sampling of aerosol with diameters of up to 10 μm. Vertical profiles extend from 1000 to 17,500 feet AGL, spanning a temperature range relevant to ice formation. 100 hours of data cover a latitude range from 30N to 46N and target a variety of potential bioaerosol source regions including forests, croplands, the Gulf of Mexico, and Lake Michigan. Observed vertical profiles are compared to expected loadings based on current model parameterizations and implications are discussed.

Evaluating Vegetation in the National Wetland Condition Assessment

EPA Science Inventory

Vegetation is a key biotic indicator of wetland ecological condition and forms a critical element of the USEPA 2011 National Wetland Condition Assessment. Data describing plant species composition and abundance, vegetation structure, and ground surface characteristics were colle...

Conserving herbivorous and predatory insects in urban green spaces.

PubMed

Mata, Luis; Threlfall, Caragh G; Williams, Nicholas S G; Hahs, Amy K; Malipatil, Mallik; Stork, Nigel E; Livesley, Stephen J

2017-01-19

Insects are key components of urban ecological networks and are greatly impacted by anthropogenic activities. Yet, few studies have examined how insect functional groups respond to changes to urban vegetation associated with different management actions. We investigated the response of herbivorous and predatory heteropteran bugs to differences in vegetation structure and diversity in golf courses, gardens and parks. We assessed how the species richness of these groups varied amongst green space types, and the effect of vegetation volume and plant diversity on trophic- and species-specific occupancy. We found that golf courses sustain higher species richness of herbivores and predators than parks and gardens. At the trophic- and species-specific levels, herbivores and predators show strong positive responses to vegetation volume. The effect of plant diversity, however, is distinctly species-specific, with species showing both positive and negative responses. Our findings further suggest that high occupancy of bugs is obtained in green spaces with specific combinations of vegetation structure and diversity. The challenge for managers is to boost green space conservation value through actions promoting synergistic combinations of vegetation structure and diversity. Tackling this conservation challenge could provide enormous benefits for other elements of urban ecological networks and people that live in cities.

Conserving herbivorous and predatory insects in urban green spaces

PubMed Central

Mata, Luis; Threlfall, Caragh G.; Williams, Nicholas S. G.; Hahs, Amy K.; Malipatil, Mallik; Stork, Nigel E.; Livesley, Stephen J.

2017-01-01

Insects are key components of urban ecological networks and are greatly impacted by anthropogenic activities. Yet, few studies have examined how insect functional groups respond to changes to urban vegetation associated with different management actions. We investigated the response of herbivorous and predatory heteropteran bugs to differences in vegetation structure and diversity in golf courses, gardens and parks. We assessed how the species richness of these groups varied amongst green space types, and the effect of vegetation volume and plant diversity on trophic- and species-specific occupancy. We found that golf courses sustain higher species richness of herbivores and predators than parks and gardens. At the trophic- and species-specific levels, herbivores and predators show strong positive responses to vegetation volume. The effect of plant diversity, however, is distinctly species-specific, with species showing both positive and negative responses. Our findings further suggest that high occupancy of bugs is obtained in green spaces with specific combinations of vegetation structure and diversity. The challenge for managers is to boost green space conservation value through actions promoting synergistic combinations of vegetation structure and diversity. Tackling this conservation challenge could provide enormous benefits for other elements of urban ecological networks and people that live in cities. PMID:28102333

Quantifying Vegetation Structure with Lightweight, Rapid-Scanning Terrestrial Lidar

NASA Astrophysics Data System (ADS)

Paynter, I.; Genest, D.; Saenz, E. J.; Strahler, A. H.; Li, Z.; Peri, F.; Schaaf, C.

2016-12-01

Light Detection and Ranging (lidar) is proving a competent technology for observing vegetation structure. Terrestrial laser scanners (TLS) are ground-based instruments which utilize hundreds of thousands to millions of lidar observations to provide detailed structural and reflective information of their surroundings. TLS has enjoyed initial success as a validation tool for satellite and airborne estimates of vegetation structure, and are producing independent estimates with increasing accuracy. Reconstruction techniques for TLS observations of vegetation have also improved rapidly, especially for trees. However, uncertainties and challenges still remain in TLS modelling of vegetation structure, especially in geometrically complex ecosystems such as tropical forests (where observation extent and density is hampered by occlusion) and highly temporally dynamic coastal ecosystems (such as saltmarshes and mangroves), where observations may be restricted to narrow microstates. Some of these uncertainties can be mitigated, and challenges met, through the use of lidar instruments optimized for favorable deployment logistics through low weight, rapid scanning, and improved durability. We have conducted studies of vegetation structure in temperate and tropical forests, saltmarshes and mangroves, utilizing a highly portable TLS with considerable deployment flexibility, the Compact Biomass Lidar (CBL). We show results from studies in the temperate Long Term Ecological Research site of Harvard Forest (MA, USA); the tropical forested long-term Carbono sites of La Selva Biological Station (Sarapiqui, Costa Rica); and the saltmarsh LTER of Plum Island (MA, USA). These results demonstrate the improvements to observations in these ecosystems which are facilitated by the specifications of the CBL (and similar TLS) which are optimized for favorable deployment logistics and flexibility. We show the benefits of increased numbers of scanning positions, and specialized deployment platforms to meet ecosystem challenges.

Beyond habitat structure: Landscape heterogeneity explains the monito del monte (Dromiciops gliroides) occurrence and behavior at habitats dominated by exotic trees.

PubMed

Salazar, Daniela A; Fontúrbel, Francisco E

2016-09-01

Habitat structure determines species occurrence and behavior. However, human activities are altering natural habitat structure, potentially hampering native species due to the loss of nesting cavities, shelter or movement pathways. The South American temperate rainforest is experiencing an accelerated loss and degradation, compromising the persistence of many native species, and particularly of the monito del monte (Dromiciops gliroides Thomas, 1894), an arboreal marsupial that plays a key role as seed disperser. Aiming to compare 2 contrasting habitats (a native forest and a transformed habitat composed of abandoned Eucalyptus plantations and native understory vegetation), we assessed D. gliroides' occurrence using camera traps and measured several structural features (e.g. shrub and bamboo cover, deadwood presence, moss abundance) at 100 camera locations. Complementarily, we used radio telemetry to assess its spatial ecology, aiming to depict a more complete scenario. Moss abundance was the only significant variable explaining D. gliroides occurrence between habitats, and no structural variable explained its occurrence at the transformed habitat. There were no differences in home range, core area or inter-individual overlapping. In the transformed habitats, tracked individuals used native and Eucalyptus-associated vegetation types according to their abundance. Diurnal locations (and, hence, nesting sites) were located exclusively in native vegetation. The landscape heterogeneity resulting from the vicinity of native and Eucalyptus-associated vegetation likely explains D. gliroides occurrence better than the habitat structure itself, as it may be use Eucalyptus-associated vegetation for feeding purposes but depend on native vegetation for nesting. © 2016 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd.

Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling

PubMed Central

Rogiers, Suzy Y.; Clarke, Simon J.

2013-01-01

Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled. PMID:24244839

Discharge of swine wastes risks water quality and food safety: Antibiotics and antibiotic resistance genes from swine sources to the receiving environments.

PubMed

He, Liang-Ying; Ying, Guang-Guo; Liu, You-Sheng; Su, Hao-Chang; Chen, Jun; Liu, Shuang-Shuang; Zhao, Jian-Liang

2016-01-01

Swine feedlots are widely considered as a potential hotspot for promoting the dissemination of antibiotic resistance genes (ARGs) in the environment. ARGs could enter the environment via discharge of animal wastes, thus resulting in contamination of soil, water, and food. We investigated the dissemination and diversification of 22 ARGs conferring resistance to sulfonamides, tetracyclines, chloramphenicols, and macrolides as well as the occurrence of 18 corresponding antibiotics from three swine feedlots to the receiving water, soil environments and vegetables. Most ARGs and antibiotics survived the on-farm waste treatment processes in the three swine farms. Elevated diversity of ARGs was observed in the receiving environments including river water and vegetable field soils when compared with respective controls. The variation of ARGs along the vertical soil profiles of vegetable fields indicated enrichment and migration of ARGs. Detection of various ARGs and antibiotic residues in vegetables fertilized by swine wastes could be of great concern to the general public. This research demonstrated the contribution of swine wastes to the occurrence and development of antibiotic resistance determinants in the receiving environments and potential risks to food safety and human health. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of dominant species on vegetation change in Carolina bay wetlands following a multi-year drought

Treesearch

John M. Mulhouse; Diane De Steven; Robert F. Lide; Rebecca R. Sharitz

2005-01-01

Wetland vegetation is strongly dependent upon climate-influenced hydrologic conditions, and plant composition responds in generally consistent ways to droughts. However, the extent of species composition change during drought may be influenced by the pre-existing structure of wetland vegetation. We characterized the vegetation of ten herbaceous Carolina bay wetlands on...

LANDFIRE 2015 Remap – Utilization of Remotely Sensed Data to Classify Existing Vegetation Type and Structure to Support Strategic Planning and Tactical Response

USGS Publications Warehouse

Picotte, Joshua J.; Long, Jordan; Peterson, Birgit; Nelson, Kurtis

2017-01-01

The LANDFIRE Program produces national scale vegetation, fuels, fire regimes, and landscape disturbance data for the entire U.S. These data products have been used to model the potential impacts of fire on the landscape [1], the wildfire risks associated with land and resource management [2, 3], and those near population centers and accompanying Wildland Urban Interface zones [4], as well as many other applications. The initial LANDFIRE National Existing Vegetation Type (EVT) and vegetation structure layers, including vegetation percent cover and height, were mapped circa 2001 and released in 2009 [5]. Each EVT is representative of the dominant plant community within a given area. The EVT layer has since been updated by identifying areas of landscape change and modifying the vegetation types utilizing a series of rules that consider the disturbance type, severity of disturbance, and time since disturbance [6, 7]. Non-disturbed areas were adjusted for vegetation growth and succession. LANDFIRE vegetation structure layers also have been updated by using data modeling techniques [see 6 for a full description]. The subsequent updated versions of LANDFIRE include LANDFIRE 2008, 2010, 2012, and LANDFIRE 2014 is being incrementally released, with all data being released in early 2017. Additionally, a comprehensive remap of the baseline data, LANDFIRE 2015 Remap, is being prototyped, and production is tentatively planned to begin in early 2017 to provide a more current baseline for future updates.

Breaking the GaN material limits with nanoscale vertical polarisation super junction structures: A simulation analysis

NASA Astrophysics Data System (ADS)

Unni, Vineet; Sankara Narayanan, E. M.

2017-04-01

This is the first report on the numerical analysis of the performance of nanoscale vertical superjunction structures based on impurity doping and an innovative approach that utilizes the polarisation properties inherent in III-V nitride semiconductors. Such nanoscale vertical polarisation super junction structures can be realized by employing a combination of epitaxial growth along the non-polar crystallographic axes of Wurtzite GaN and nanolithography-based processing techniques. Detailed numerical simulations clearly highlight the limitations of a doping based approach and the advantages of the proposed solution for breaking the unipolar one-dimensional material limits of GaN by orders of magnitude.

Combinatorial evaluation of systems including decomposition of a system representation into fundamental cycles

DOEpatents

Oliveira, Joseph S [Richland, WA; Jones-Oliveira, Janet B [Richland, WA; Bailey, Colin G [Wellington, NZ; Gull, Dean W [Seattle, WA

2008-07-01

One embodiment of the present invention includes a computer operable to represent a physical system with a graphical data structure corresponding to a matroid. The graphical data structure corresponds to a number of vertices and a number of edges that each correspond to two of the vertices. The computer is further operable to define a closed pathway arrangement with the graphical data structure and identify each different one of a number of fundamental cycles by evaluating a different respective one of the edges with a spanning tree representation. The fundamental cycles each include three or more of the vertices.

Canopy BRF simulation of forest with different crown shape and height in larger scale based on Radiosity method

NASA Astrophysics Data System (ADS)

Song, Jinling; Qu, Yonghua; Wang, Jindi; Wan, Huawei; Liu, Xiaoqing

2007-06-01

Radiosity method is based on the computer simulation of 3D real structures of vegetations, such as leaves, branches and stems, which are composed by many facets. Using this method we can simulate the canopy reflectance and its bidirectional distribution of the vegetation canopy in visible and NIR regions. But with vegetations are more complex, more facets to compose them, so large memory and lots of time to calculate view factors are required, which are the choke points of using Radiosity method to calculate canopy BRF of lager scale vegetation scenes. We derived a new method to solve the problem, and the main idea is to abstract vegetation crown shapes and to simplify their structures, which can lessen the number of facets. The facets are given optical properties according to the reflectance, transmission and absorption of the real structure canopy. Based on the above work, we can simulate the canopy BRF of the mix scenes with different species vegetation in the large scale. In this study, taking broadleaf trees as an example, based on their structure characteristics, we abstracted their crowns as ellipsoid shells, and simulated the canopy BRF in visible and NIR regions of the large scale scene with different crown shape and different height ellipsoids. Form this study, we can conclude: LAI, LAD the probability gap, the sunlit and shaded surfaces are more important parameter to simulate the simplified vegetation canopy BRF. And the Radiosity method can apply us canopy BRF data in any conditions for our research.

Structural classification of marshes with Polarimetric SAR highlighting the temporal mapping of marshes exposed to oil

USGS Publications Warehouse

Ramsey, Elijah W.; Rangoonwala, Amina; Jones, Cathleen E.

2015-01-01

Empirical relationships between field-derived Leaf Area Index (LAI) and Leaf Angle Distribution (LAD) and polarimetric synthetic aperture radar (PolSAR) based biophysical indicators were created and applied to map S. alterniflora marsh canopy structure. PolSAR and field data were collected near concurrently in the summers of 2010, 2011, and 2012 in coastal marshes, and PolSAR data alone were acquired in 2009. Regression analyses showed that LAI correspondence with the PolSAR biophysical indicator variables equaled or exceeded those of vegetation water content (VWC) correspondences. In the final six regressor model, the ratio HV/VV explained 49% of the total 77% explained LAI variance, and the HH-VV coherence and phase information accounted for the remainder. HV/HH dominated the two regressor LAD relationship, and spatial heterogeneity and backscatter mechanism followed by coherence information dominated the final three regressor model that explained 74% of the LAD variance. Regression results applied to 2009 through 2012 PolSAR images showed substantial changes in marsh LAI and LAD. Although the direct cause was not substantiated, following a release of freshwater in response to the 2010 Deepwater Horizon oil spill, the fairly uniform interior marsh structure of 2009 was more vertical and dense shortly after the oil spill cessation. After 2010, marsh structure generally progressed back toward the 2009 uniformity; however, the trend was more disjointed in oil impact marshes.             

Percent canopy cover and stand structure statistics from the Forest Vegetation Simulator

Treesearch

Nicholas L. Crookston; Albert R. Stage

1999-01-01

Estimates of percent canopy cover generated by the Forest Vegetation Simulator (FVS) are corrected for crown overlap using an equation presented in this paper. A comparison of the new cover estimate to some others is provided. The cover estimate is one of several describing stand structure. The structure descriptors also include major species, ranges of diameters, tree...

Impacts of deer herbivory on vegetation in Rock Creek Park, 2001-2009

USGS Publications Warehouse

Kraft, Cairn C.; Hatfield, Jeff S.

2011-01-01

Starting in 2001, vegetation data have been collected annually in 16 study modules consisting of paired (1x4 m) fenced plots and unfenced control plots located in the upland forests of Rock Creek Park, Washington, D.C. Vegetation data collected from 2001-2009 have been analyzed to determine impacts of deer herbivory on vegetation in the park. Differences between fenced plots and unfenced control plots were analyzed for the following variables: cover provided by various groups of species (woody, herbaceous, native, non-native, trees, shrubs, and woody vines), as well as by individual dominant species, vegetation thickness (a measure of percent cover projected horizontally that provides information on the vertical distribution of vegetation), and species richness overall and for groups of species (woody, herbaceous, native, non-native, trees, shrubs, and woody vines). The analyses were performed using repeated measures analysis of variance (ANOVA) and associated tests. Vegetation in plots protected from deer herbivory for 9 years showed significantly greater vegetative cover compared to plots not protected from deer herbivory. This effect was most pronounced for woody and shrub cover. Cover by the dominant species was not significantly greater in the fenced plots compared to the unfenced control plots, indicating that the significant differences observed for groups were not driven by single species within those groups. With respect to vegetation thickness, results indicate that protection from deer herbivory produced significantly higher levels of vegetation in the fenced plots compared to the unfenced control plots for both the Low (0-30 cm) and Middle (30-110 cm) height classes. Protection from deer herbivory has led to higher overall species richness and higher species richness for woody species, natives, and shrubs compared to plots not receiving protection. There is also evidence that plots protected from deer herbivory and those not receiving this protection are diverging over time with respect to a number of variables such as cover by woody and shrub species, cover in the lowest height class, and species richness of woody and native species. Recommendations were made regarding future sampling.

Effects of Vegetation Structure on the Location of Lion Kill Sites in African Thicket.

PubMed

Davies, Andrew B; Tambling, Craig J; Kerley, Graham I H; Asner, Gregory P

2016-01-01

Predator-prey relationships are integral to ecosystem stability and functioning. These relationships are, however, difficult to maintain in protected areas where large predators are increasingly being reintroduced and confined. Where predators make kills has a profound influence on their role in ecosystems, but the relative importance of environmental variables in determining kill sites, and how these might vary across ecosystems is poorly known. We investigated kill sites for lions in South Africa's thicket biome, testing the importance of vegetation structure for kill site locations compared to other environmental variables. Kill sites were located over four years using GPS telemetry and compared to non-kill sites that had been occupied by lions, as well as to random sites within lion ranges. Measurements of 3D vegetation structure obtained from Light Detection and Ranging (LiDAR) were used to calculate the visible area (viewshed) around each site and, along with wind and moonlight data, used to compare kill sites between lion sexes, prey species and prey sexes. Viewshed area was the most important predictor of kill sites (sites in dense vegetation were twice as likely to be kill sites compared to open areas), followed by wind speed and, less so, moonlight. Kill sites for different prey species varied with vegetation structure, and male prey were killed when wind speeds were higher compared to female prey of the same species. Our results demonstrate that vegetation structure is an important component of predator-prey interactions, with varying effects across ecosystems. Such differences require consideration in terms of the ecological roles performed by predators, and in predator and prey conservation.

Forest structure affects trophic linkages: How silvicultural disturbance impacts bats and their insect prey

USGS Publications Warehouse

Dodd, L.E.; Lacki, M.J.; Britzke, E.R.; Buehler, D.A.; Keyser, P.D.; Larkin, J.L.; Rodewald, A.D.; Wigley, T.B.; Wood, P.B.; Rieske, L.K.

2012-01-01

Vertebrate insectivores such as bats are a pervasive top-down force on prey populations in forest ecosystems. Conservation focusing on forest-dwelling bats requires understanding of community-level interactions between these predators and their insect prey. Our study assessed bat activity and insect occurrence (abundance and diversity) across a gradient of forest disturbance and structure (silvicultural treatments) in the Central Appalachian region of North America. We conducted acoustic surveys of bat echolocation concurrent with insect surveys using blacklight and malaise traps over 2 years. Predator activity, prey occurrence and prey biomass varied seasonally and across the region. The number of bat echolocation pulses was positively related with forest disturbance, whereas prey demonstrated varied trends. Lepidopteran abundance was negatively related with disturbance, while dipteran abundance and diversity was positively related with disturbance. Coleoptera were unaffected. Neither bat nor insect response variables differed between plot interiors and edges. Correlations between bat activity and vegetative structure reflected differences in foraging behavior among ensembles. Activity of myotine bats was correlated with variables describing sub-canopy vegetation, whereas activity of lasiurine bats was more closely correlated with canopy-level vegetation. Lepidopteran abundance was correlated with variables describing canopy and sub-canopy vegetation, whereas coleopteran and dipteran occurrence were more closely correlated with canopy-level vegetative structure. Our study demonstrates regional variation in bat activity and prey occurrence across a forested disturbance gradient. Land management and conservation efforts should consider the importance of vegetation structure and plant species richness to sustain forest-dwelling bats and their insect prey.

Off-Nadir Hyperspectral Sensing for Estimation of Vertical Profile of Leaf Chlorophyll Content within Wheat Canopies.

PubMed

Kong, Weiping; Huang, Wenjiang; Casa, Raffaele; Zhou, Xianfeng; Ye, Huichun; Dong, Yingying

2017-11-23

Monitoring the vertical profile of leaf chlorophyll (Chl) content within winter wheat canopies is of significant importance for revealing the real nutritional status of the crop. Information on the vertical profile of Chl content is not accessible to nadir-viewing remote or proximal sensing. Off-nadir or multi-angle sensing would provide effective means to detect leaf Chl content in different vertical layers. However, adequate information on the selection of sensitive spectral bands and spectral index formulas for vertical leaf Chl content estimation is not yet available. In this study, all possible two-band and three-band combinations over spectral bands in normalized difference vegetation index (NDVI)-, simple ratio (SR)- and chlorophyll index (CI)-like types of indices at different viewing angles were calculated and assessed for their capability of estimating leaf Chl for three vertical layers of wheat canopies. The vertical profiles of Chl showed top-down declining trends and the patterns of band combinations sensitive to leaf Chl content varied among different vertical layers. Results indicated that the combinations of green band (520 nm) with NIR bands were efficient in estimating upper leaf Chl content, whereas the red edge (695 nm) paired with NIR bands were dominant in quantifying leaf Chl in the lower layers. Correlations between published spectral indices and all NDVI-, SR- and CI-like types of indices and vertical distribution of Chl content showed that reflectance measured from 50°, 30° and 20° backscattering viewing angles were the most promising to obtain information on leaf Chl in the upper-, middle-, and bottom-layer, respectively. Three types of optimized spectral indices improved the accuracy for vertical leaf Chl content estimation. The optimized three-band CI-like index performed the best in the estimation of vertical distribution of leaf Chl content, with R² of 0.84-0.69, and RMSE of 5.37-5.56 µg/cm² from the top to the bottom layers, while the optimized SR-like index was recommended for the bottom Chl estimation due to its simple and universal form. We suggest that it is necessary to take into account the penetration characteristic of the light inside the canopy for different Chl absorption regions of the spectrum and the formula used to derive spectral index when estimating the vertical profile of leaf Chl content using off-nadir hyperspectral data.

Coupling of Water and Carbon Cycles in Boreal Ecosystems at Watershed and National Scales

NASA Astrophysics Data System (ADS)

Chen, J. M.; Ju, W.; Govind, A.; Sonnentag, O.

2009-05-01

The boreal landscapes is relatively flat giving the impression of spatial homogeneity. However, glacial activities have left distinct fingerprints on the vegetation distribution on moderately rolling terrains over the boreal landscape. Upland or lowland forests types or wetlands having various degrees of hydrological connectivitiy to the surrounding terrain are typical of the boreal landscape. The nature of the terrain creates unique hydrological conditions affecting the local-scale ecophysiological and biogeochemical processes. As part of the Canadian Carbon Program, we investigated the importance of lateral water redistribution through surface and subsurface flows in the spatial distribution of the vertical fluxes of water and carbon. A spatially explicit hydroecological model (BEPS-TerrainLab) has been developed and tested in forested and wetland watersheds . Remotely sensed vegetation parameters along with other spatial datasets are used to run this model, and tower flux data are used for partial validation. It is demonstrated in both forest and wetland watersheds that ignoring the lateral water redistribution over the landscape, commonly done in 1-dimensional bucket models, can cause considerable biases in the vertical carbon and water flux estimation, in addition to the distortion of the spatial patterns of these fluxes. The biases in the carbon flux are considerably larger than those in the water flux. The significance of these findings in national carbon budget estimation is demonstrated by separate modeling of 2015 watersheds over the Canadian landmass.

Do state-of-the-art CMIP5 ESMs accurately represent observed vegetation-rainfall feedbacks? Focus on the Sahel

NASA Astrophysics Data System (ADS)

Notaro, M.; Wang, F.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.

2017-12-01

The semi-arid Sahel ecoregion is an established hotspot of land-atmosphere coupling. Ocean-land-atmosphere interactions received considerable attention by modeling studies in response to the devastating 1970s-90s Sahel drought, which models suggest was driven by sea-surface temperature (SST) anomalies and amplified by local vegetation-atmosphere feedbacks. Vegetation affects the atmosphere through biophysical feedbacks by altering the albedo, roughness, and transpiration and thereby modifying exchanges of energy, momentum, and moisture with the atmosphere. The current understanding of these potentially competing processes is primarily based on modeling studies, with biophysical feedbacks serving as a key uncertainty source in regional climate change projections among Earth System Models (ESMs). In order to reduce this uncertainty, it is critical to rigorously evaluate the representation of vegetation feedbacks in ESMs against an observational benchmark in order to diagnose systematic biases and their sources. However, it is challenging to successfully isolate vegetation's feedbacks on the atmosphere, since the atmospheric control on vegetation growth dominates the atmospheric feedback response to vegetation anomalies and the atmosphere is simultaneously influenced by oceanic and terrestrial anomalies. In response to this challenge, a model-validated multivariate statistical method, Stepwise Generalized Equilibrium Feedback Assessment (SGEFA), is developed, which extracts the forcing of a slowly-evolving environmental variable [e.g. SST or leaf area index (LAI)] on the rapidly-evolving atmosphere. By applying SGEFA to observational and remotely-sensed data, an observational benchmark is established for Sahel vegetation feedbacks. In this work, the simulated responses in key atmospheric variables, including evapotranspiration, albedo, wind speed, vertical motion, temperature, stability, and rainfall, to Sahel LAI anomalies are statistically assessed in Coupled Model Intercomparison Project Phase 5 (CMIP5) ESMs through SGEFA. The dominant mechanism, such as albedo feedback, moisture recycling, or momentum feedback, in each ESM is evaluated against the observed benchmark. SGEFA facilitates a systematic assessment of model biases in land-atmosphere interactions.

Vegetation Water Content (VWC) dynamics in during SMAPVEX16

NASA Astrophysics Data System (ADS)

Steele-Dunne, S. C.; Polo Bermejo, J.; Judge, J.; Bongiovanni, T. E.; Chakrabarti, S.; Liu, P. W.; Bragdon, J.; Hornbuckle, B. K.

2016-12-01

Vegetation water content has a confounding effect on the retrieval of soil moisture from microwave brightness temperatures. The presence of water in the overlying canopy influences the emission from the canopy itself and attenuates the emission from the soil. The purpose of this study is to gain insight into the dynamics of vegetation water content in the context of microwave remote sensing. The key questions are: (1) How is moisture distributed in an agricultural canopy? (2) How does that vertical distribution change in time? (3) How do these dynamics influence the observed brightness temperature? To address these questions, a detailed sampling campaign was undertaken in one corn field and one soybean field at an intensively monitored site near Buckeye, Iowa within the SMAPVEX16 domain. The experiment duration extends from the beginning of IOP1 to the end of IOP2, i.e. from May 18 to August 16 2016. Vegetation sampling was performed on days upon which SMAP had both an ascending and a descending pass. On these days, destructive vegetation samples were generally collected at 6pm and 6pm unless the weather conditions were bad. In addition to measuring the bulk vegetation water content for comparison to the SMAP retrieved VWC, the samples were split into leaves and stems. For the corn plants, leaf moisture content was also measured as a function of height and the stem was cut into 10cm sections. Results will be presented to show the changes in VWC associated with plant development through the vegetative and reproductive stages as well as diurnal variations associated with water availability in the root zone and variations in evaporative demand. In addition, fresh biomass, dry biomass and vegetation water content will be related to brightness temperature observations from (1) the SMAP and SMOS satellite missions, (2) the PALS instrument flown during the SMAPVEX16 IOPs in Iowa (3) the tower-based radiometers located at the soybean and corn fields.

Using Small Drone (UAS) Imagery to Bridge the Gap Between Field- and Satellite-Based Measurements of Vegetation Structure and Change

NASA Astrophysics Data System (ADS)

Mayes, M. T.; Estes, L. D.; Gago, X.; Debats, S. R.; Caylor, K. K.; Manfreda, S.; Oudemans, P.; Ciraolo, G.; Maltese, A.; Nadal, M.; Estrany, J.

2016-12-01

Leaf area is an important ecosystem variable that relates to vegetation biomass, productivity, water and nutrient use in natural and agricultural systems globally. Since the 1980s, optical satellite image-based estimates of leaf area based on indices such as Normalized Difference Vegetation Index (NDVI) have greatly improved understanding of vegetation structure, function, and responses to disturbance at landscape (10^3 km2) to continental (10^6 km2) spatial scales. However, at landscape scales, satellites have failed to capture many leaf area patterns indicative of vegetation succession, crop types, stress and other conditions important for ecological processes. Small drones (UAS - unmanned aerial systems) offer new means for assessing leaf area and vegetation structure at higher spatial resolutions (<1 m) and land cover features such as substrate exposure that may affect estimates of vegetation structure in satellite data. Yet it is unclear how differences in spatial and spectral resolution between UAS and satellite data affect their relationships to each other, and to common field measurements of leaf area (e.g. LiCOR photosensors) and land cover. Constraining these relationships is important for leveraging UAS data to improve scaling of field data on leaf area and biomass to satellite data from Landsat, Sentinel-2, and increasing numbers of commercial sensors. Here, we quantify relationships among field, UAS and satellite estimates of vegetation leaf area and biomass in three case study landscapes spanning semi-arid Mediterranean (Matera, Southern Italy and Mallorca, Spain) and North American temperate ecosystems (New Jersey, USA). We assess how land cover and sensor spectral characteristics affect UAS and satellite-derived NDVI, leaf-area and biomass estimates. Then, we assess the fidelity of UAS, WorldView-2, and Landsat leaf-area and biomass estimates to field-measured landscape changes and variability, including vegetation recovery from fire (Mallorca), and leaf-area and biomass variability due to orchard type and agro-ecosystem management (Matera, New Jersey). Finally, we highlight promising ways forward for improving field data collection and the use of UAS observations to monitor vegetation leaf-area and biomass change at landscape scales in natural and agricultural systems.

Coherence Effects in L-Band Active and Passive Remote Sensing of Quasi-Periodic Corn Canopies

NASA Technical Reports Server (NTRS)

Utku, Cuneyt; Lang, Roger H.

2011-01-01

Due to their highly random nature, vegetation canopies can be modeled using the incoherent transport theory for active and passive remote sensing applications. Agricultural vegetation canopies however are generally more structured than natural vegetation. The inherent row structure in agricultural canopies induces coherence effects disregarded by the transport theory. The objective of this study is to demonstrate, via Monte-Carlo simulations, these coherence effects on L-band scattering and thermal emission from corn canopies consisting of only stalks.

Revisiting salt marsh resilience to sea level rise: Are ponds responsible for permanent land loss?

NASA Astrophysics Data System (ADS)

Mariotti, G.

2016-12-01

Ponds are un-vegetated rounded depressions commonly present on marsh platforms. The role of ponds on the long-term morphological evolution of tidal marshes is unclear - at times ponds expand but eventually recover the marsh platform, at other times ponds never recover and lead to permanent marsh loss. Existing field observations indicate that episodic disturbances of the marsh vegetation cause the formation of small (1-10 m) isolated ponds, even if the vegetated platform keeps pace with Relative Sea Level Rise (RSLR), and that isolated ponds tend to deepen and enlarge until they eventually connect to the channel network. Here I implement a simple model to study the vertical and planform evolution of a single connected pond. A newly connected pond recovers if its bed lies above the limit for marsh plant growth, or if the inorganic deposition rate is larger than the RSLR rate. A pond that cannot accrete faster than RSLR will deepen and enlarge, eventually entering a runaway erosion by wave edge retreat. A large tidal range, a large sediment supply, and a low rate of RSLR favor pond recovery. The model suggests that inorganic sediment deposition alone controls pond recovery, even in marshes where organic matter dominates accretion of the vegetated platform. As such, halting permanent marsh loss by pond collapse requires to increase inorganic sediment deposition. Because pond collapse is possible even if the vegetated platform keeps pace with RSLR, I conclude that marsh resilience to RSLR is less than previously quantified.

Numerical analysis of the cylindrical rigidity of the vertical steel tank shell

NASA Astrophysics Data System (ADS)

Chirkov, Sergey; Tarasenko, Alexander; Chepur, Petr

2017-10-01

The paper deals with the study of rigidity of a vertical steel cylindrical tank and its structural elements with the development of inhomogeneous subsidence in ANSYS software complex. The limiting case is considered in this paper: a complete absence of a base sector that varies along an arc of a circle. The subsidence zone is modeled by the parameter n. A finite-element model of vertical 20000 m3 steel tank has been created, taking into account all structural elements of tank metal structures, including the support ring, beam frame and roof sheets. Various combinations of vertical steel tank loading are analyzed. For operational loads, the most unfavorable combination is considered. Calculations were performed for the filled and emptied tank. Values of the maximum possible deformations of the outer contour of the bottom are obtained with the development of inhomogeneous base subsidence for the given tank size. The obtained parameters of intrinsic rigidity (deformability) of vertical steel tank can be used in the development of new regulatory and technical documentation for tanks.

Two-age silviculture: an innovative tool for enhancing species diversity and vertical structure in Appalachian hardwoods

Treesearch

Gary W. Miller; Petra B. Wood; Jeffrey V. Nichols; Jeffrey V. Nichols

1995-01-01

Silvicultural practices that promote a two-age stand structure provide an opportunity to maintain diversity of woody species and vertical structure for extended periods of time in Appalachian hardwoods. Data from four two-age stands initiated by deferment cutting in West Virginia are summarized for the first 10 to 15 years after treatment. Results indicated that 15...

Supplemental Planting of Early Successional Tree Species During Bottomland Hardwood Afforestation

Treesearch

Daniel J. Twedt; R. Randy Wilson

2002-01-01

Reforestation of former bottomland hardwood forests that have been cleared for agriculture (i.e., afforestation) has historically emphasized planting heavy-seeded oaks (Quercus spp.) and pecans (Carya spp.). These species are slow to develop vertical forest structure. However, vertical forest structure is key to colonization of...

Identification and Simulation of Subsurface Soil patterns using hidden Markov random fields and remote sensing and geophysical EMI data sets

NASA Astrophysics Data System (ADS)

Wang, Hui; Wellmann, Florian; Verweij, Elizabeth; von Hebel, Christian; van der Kruk, Jan

2017-04-01

Lateral and vertical spatial heterogeneity of subsurface properties such as soil texture and structure influences the available water and resource supply for crop growth. High-resolution mapping of subsurface structures using non-invasive geo-referenced geophysical measurements, like electromagnetic induction (EMI), enables a characterization of 3D soil structures, which have shown correlations to remote sensing information of the crop states. The benefit of EMI is that it can return 3D subsurface information, however the spatial dimensions are limited due to the labor intensive measurement procedure. Although active and passive sensors mounted on air- or space-borne platforms return 2D images, they have much larger spatial dimensions. Combining both approaches provides us with a potential pathway to extend the detailed 3D geophysical information to a larger area by using remote sensing information. In this study, we aim at extracting and providing insights into the spatial and statistical correlation of the geophysical and remote sensing observations of the soil/vegetation continuum system. To this end, two key points need to be addressed: 1) how to detect and recognize the geometric patterns (i.e., spatial heterogeneity) from multiple data sets, and 2) how to quantitatively describe the statistical correlation between remote sensing information and geophysical measurements. In the current study, the spatial domain is restricted to shallow depths up to 3 meters, and the geostatistical database contains normalized difference vegetation index (NDVI) derived from RapidEye satellite images and apparent electrical conductivities (ECa) measured from multi-receiver EMI sensors for nine depths of exploration ranging from 0-2.7 m. The integrated data sets are mapped into both the physical space (i.e. the spatial domain) and feature space (i.e. a two-dimensional space framed by the NDVI and the ECa data). Hidden Markov Random Fields (HMRF) are employed to model the underlying heterogeneities in spatial domain and finite Gaussian mixture models are adopted to quantitatively describe the statistical patterns in terms of center vectors and covariance matrices in feature space. A recently developed parallel stochastic clustering algorithm is adopted to implement the HMRF models and the Markov chain Monte Carlo based Bayesian inference. Certain spatial patterns such as buried paleo-river channels covered by shallow sediments are investigated as typical examples. The results indicate that the geometric patterns of the subsurface heterogeneity can be represented and quantitatively characterized by HMRF. Furthermore, the statistical patterns of the NDVI and the EMI data from the soil/vegetation-continuum system can be inferred and analyzed in a quantitative manner.

Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

DOEpatents

Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

2015-01-13

Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and Meridional Transport of Dust and Water.

NASA Technical Reports Server (NTRS)

Kahre, M. A.

2015-01-01

The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric circulation, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net meridional transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net meridional transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

76 FR 13546 - Airworthiness Directives; The Boeing Company Model MD-90-30 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-14

...We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs=52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This proposed AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and a cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are proposing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

76 FR 41651 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-15

...We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs = 52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and a cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are issuing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

76 FR 35342 - Airworthiness Directives; The Boeing Company Model MD-90-30 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-17

...We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs=52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are issuing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

Classical r matrix of the su(2 vertical bar 2) super Yang-Mills spin chain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Torrielli, Alessandro

2007-05-15

In this note we straightforwardly derive and make use of the quantum R matrix for the su(2 vertical bar 2) super Yang-Mills spin chain in the manifest su(1 vertical bar 2)-invariant formulation, which solves the standard quantum Yang-Baxter equation, in order to obtain the correspondent (undressed) classical r matrix from the first order expansion in the 'deformation' parameter 2{pi}/{radical}({lambda}) and check that this last solves the standard classical Yang-Baxter equation. We analyze its bialgebra structure, its dependence on the spectral parameters, and its pole structure. We notice that it still preserves an su(1 vertical bar 2) subalgebra, thereby admitting anmore » expression in terms of a combination of projectors, which spans only a subspace of su(1 vertical bar 2)xsu(1 vertical bar 2). We study the residue at its simple pole at the origin and comment on the applicability of the classical Belavin-Drinfeld type of analysis.« less

Vertical Structure of Radiation-pressure-dominated Thin Disks: Link between Vertical Advection and Convective Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Hong-Yu; Gu, Wei-Min, E-mail: guwm@xmu.edu.cn

2017-04-20

In the classic picture of standard thin accretion disks, viscous heating is balanced by radiative cooling through the diffusion process, and the radiation-pressure-dominated inner disk suffers convective instability. However, recent simulations have shown that, owing to the magnetic buoyancy, the vertical advection process can significantly contribute to energy transport. In addition, in comparing the simulation results with the local convective stability criterion, no convective instability has been found. In this work, following on from simulations, we revisit the vertical structure of radiation-pressure-dominated thin disks and include the vertical advection process. Our study indicates a link between the additional energy transportmore » and the convectively stable property. Thus, the vertical advection not only significantly contributes to the energy transport, but it also plays an important role in making the disk convectively stable. Our analyses may help to explain the discrepancy between classic theory and simulations on standard thin disks.« less

Classification of American metropolitan areas by ecoregion and potential natural vegetation

Treesearch

Ralph A. Sanders; Rowan A. Rowntree

1983-01-01

This publication classifies 279 American metropolitan areas by ecoregion and potential natural vegetation. The classification forms a baseline of expected vegetation structure and composition that can assist scientists and policy makers in making urban forestry generalizations about classes of cities.

Understanding Large Wind Farm Impacts on Regional Climate and Vegetation Growth from Observational and Modeling Perspectives

NASA Astrophysics Data System (ADS)

Xia, Geng

In the most recent decade, wind energy has experienced exponential growth worldwide and this rapid increase is expected to continue, particularly over farmlands in the United States. This poses an important question regarding whether the widespread deployment of wind turbines (WTs) will influence surface/near-surface microclimate and vegetation growth. In this dissertation, I investigate the potential wind farm (WF) impacts on regional climate and vegetation growth from both observational and modeling perspectives. High resolution satellite, radiosonde and field observations are used to determine the magnitude and variability of WF-induced changes on surface/near-surface temperatures while the Weather Research and Forecasting (WRF) model is used to simulate these changes in real-world WFs at regional scales and to uncover the physical processes behind the simulated temperature changes. First, the primary physical mechanisms controlling the seasonal and diurnal variations of WF impacts on land surface temperature (LST) are investigated by analyzing both satellite data and field observations. It is found that the turbine-induced turbulent kinetic energy (TKE) relative to the background TKE determines the magnitude and variability of such impacts. In addition, atmospheric stability also matters in determining the sign and strength of the net downward heat transport as well as the magnitude of the background TKE. Second, the WRF's ability in simulating the observed WF impacts on LST is examined by conducting real-world WF experiments driven by realistic initial and boundary conditions. Overall, the WRF model can moderately reproduce the observed spatiotemporal variations of the background LST but has difficulties in reproducing such variations for the turbine-induced LST change signals at pixel levels. However, the model is still able to reproduce the coherent and consistent responses of the observed WF-induced LST changes at regional scales. Third, the spatiotemporal characteristics of the simulated temperature changes as well as the relevant physical processes responsible for such changes are further investigated using the WRF model. It is found that (i) the WF-induced sensible heat flux change is the dominant surface forcing responsible for the simulated temperature changes; (ii) the WF-induced temperature changes are not only restricted at the surface but also can extend vertically to the hub-height level and horizontally spread 60 km in the downwind direction; (iii) the vertical divergence of heat flux from the planetary boundary layer scheme and the resolved temperature advection are the two most likely physical processes behind the simulated temperature changes. Finally, the possible WF impacts on vegetation growth are also investigated using high resolution ( 250m) satellite derived vegetation indices (VI) over two well-studied large WF regions. Results indicate that the WFs have insignificant or no detectable impacts on local vegetation growth. At the pixel level, the VI changes demonstrate a random nature and have no spatial coupling with the WF layout. At the regional level, there is no systematic shift in vegetation greenness between the pre- and post-turbine periods. At interannual and seasonal time scales, there are no confident vegetation changes over wind farm pixels relative to non-wind farm pixels. Most importantly, the majority of the VI changes are within the data uncertainty, suggesting that the WF impacts on vegetation, if any, cannot be separated confidently from the data noise.

Physically-based Canopy Reflectance Model Inversion of Vegetation Biophysical-Structural Information from Terra-MODIS Imagery in Boreal and Mountainous Terrain for Ecosystem, Climate and Carbon Models using the BIOPHYS-MFM Algorithm

NASA Astrophysics Data System (ADS)

Peddle, D. R.; Hall, F.

2009-12-01

The BIOPHYS algorithm provides innovative and flexible methods for the inversion of canopy reflectance models (CRM) to derive essential biophysical structural information (BSI) for quantifying vegetation state and disturbance, and for input to ecosystem, climate and carbon models. Based on spectral, angular, temporal and scene geometry inputs that can be provided or automatically derived, the BIOPHYS Multiple-Forward Mode (MFM) approach generates look-up tables (LUTs) that comprise reflectance data, structural inputs over specified or computed ranges, and the associated CRM output from forward mode runs. Image pixel and model LUT spectral values are then matched. The corresponding BSI retrieved from the LUT matches is output as the BSI results. BIOPHYS-MFM has been extensively used with agencies in Canada and the USA over the past decade (Peddle et al 2000-09; Soenen et al 2005-09; Gamon et al 2004; Cihlar et al 2003), such as CCRS, CFS, AICWR, NASA LEDAPS, BOREAS and MODIS Science Teams, and for the North American Carbon Program. The algorithm generates BSI products such as land cover, biomass, stand volume, stem density, height, crown closure, leaf area index (LAI) and branch area, crown dimension, productivity, topographic correction, structural change from harvest, forest fires and mountain pine beetle damage, and water / hydrology applications. BIOPHYS-MFM has been applied in different locations in Canada (six provinces from Newfoundland to British Columbia) and USA (NASA COVER, MODIS and LEDAPS sites) using 7 different CRM models and a variety of imagery (e.g. MODIS, Landsat, SPOT, IKONOS, airborne MSV, MMR, casi, Probe-1, AISA). In this paper we summarise the BIOPHYS-MFM algorithm and results from Terra-MODIS imagery from MODIS validation sites at Kananaskis Alberta in the Canadian Rocky Mountains, and from the Boreal Ecosystem Atmosphere Study (BOREAS) in Saskatchewan Canada. At the montane Rocky Mountain site, BIOPHYS-MFM density estimates were within ±380 stems/hectare (ha), with horizontal crown radius (HCR) ±0.4m, vertical crown radius (VCR) ±0.6m, and height (HGT) ±0.8m. At the BOREAS site, analysis of single-date MODIS imagery yielded density estimates within ±210 stems/ha, HCR ±0.3m, VCR ±0.5m, and HGT ±0.9m. Higher accuracies at BOREAS compared to the Rocky Mountain site were attributed primarily to the more complex terrain in the mountains, for which good results were obtained given the steep environmental, ecosystem, terrain and biophysical gradients. Further analysis of multiple BOREAS MODIS scenes with different view zenith angles provided convergence of BSI results, with improvements found for density (±42 stems/ha) and HCR (±0.2m). We concluded that good results from MODIS were obtained for both boreal and montane ecosystems. From this and other studies, BIOPHYS-MFM is well suited for large-area, multi-temporal applications involving multiple image sets and mosaics for assessing vegetation disturbance and quantifying vegetation dynamics for carbon and other models. It is also suitable for integration with forest inventory, monitoring and update needs, and other programs.

Helical structures in vertically aligned dust particle chains in a complex plasma

NASA Astrophysics Data System (ADS)

Hyde, Truell W.; Kong, Jie; Matthews, Lorin S.

2013-05-01

Self-assembly of structures from vertically aligned, charged dust particle bundles within a glass box placed on the lower, powered electrode of a Gaseous Electronics Conference rf reference cell were produced and examined experimentally. Self-organized formation of one-dimensional vertical chains, two-dimensional zigzag structures, and three-dimensional helical structures of triangular, quadrangular, pentagonal, hexagonal, and heptagonal symmetries are shown to occur. System evolution is shown to progress from a one-dimensional chain structure, through a zigzag transition to a two-dimensional, spindlelike structure, and then to various three-dimensional, helical structures exhibiting multiple symmetries. Stable configurations are found to be dependent upon the system confinement, γ2=ω0h/ω0v2 (where ω0h,v are the horizontal and vertical dust resonance frequencies), the total number of particles within a bundle, and the rf power. For clusters having fixed numbers of particles, the rf power at which structural phase transitions occur is repeatable and exhibits no observable hysteresis. The critical conditions for these structural phase transitions as well as the basic symmetry exhibited by the one-, two-, and three-dimensional structures that subsequently develop are in good agreement with the theoretically predicted configurations of minimum energy determined employing molecular dynamics simulations for charged dust particles confined in a prolate, spheroidal potential as presented theoretically by Kamimura and Ishihara [Kamimura and Ishihara, Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.85.016406 85, 016406 (2012)].

Three-dimensional Numerical Analysis on Blade Response of Vertical Axis Tidal Current Turbine Under Operational Condition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Ye; Karri, Naveen K.; Wang, Qi

Tidal power as a large-scale renewable source of energy has been receiving significant attention recently because of its advantages over the wind and other renewal energy sources. The technology used to harvest energy from tidal current is called a tidal current turbine. Though some of the principles of wind turbine design are applicable to tidal current turbines, the design of latter ones need additional considerations like cavitation damage, corrosion etc. for the long-term reliability of such turbines. Depending up on the orientation of axis, tidal current turbines can be classified as vertical axis turbines or horizontal axis turbines. Existing studiesmore » on the vertical axis tidal current turbine focus more on the hydrodynamic aspects of the turbine rather than the structural aspects. This paper summarizes our recent efforts to study the integrated hydrodynamic and structural aspects of the vertical axis tidal current turbines. After reviewing existing methods in modeling tidal current turbines, we developed a hybrid approach that combines discrete vortex method -finite element method that can simulate the integrated hydrodynamic and structural response of a vertical axis turbine. This hybrid method was initially employed to analyze a typical three-blade vertical axis turbine. The power coefficient was used to evaluate the hydrodynamic performance, and critical deflection was considered to evaluate the structural reliability. A sensitivity analysis was also conducted with various turbine height-to-radius ratios. The results indicate that both the power output and failure probability increase with the turbine height, suggesting a necessity for optimal design. An attempt to optimize a 3-blade vertical axis turbine design with hybrid method yielded a ratio of turbine height to radius (H/R) about 3.0 for reliable maximum power output.« less

Intercomparison of vertical structure of storms revealed by ground-based (NMQ) and spaceborne radars (CloudSat-CPR and TRMM-PR).

PubMed

Fall, Veronica M; Cao, Qing; Hong, Yang

2013-01-01

Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR) and Ku-band Precipitation Radar (PR), which are onboard NASA's CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE). This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ) system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors' type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR) reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts.

Intercomparison of Vertical Structure of Storms Revealed by Ground-Based (NMQ) and Spaceborne Radars (CloudSat-CPR and TRMM-PR)

PubMed Central

Fall, Veronica M.; Hong, Yang

2013-01-01

Spaceborne radars provide great opportunities to investigate the vertical structure of clouds and precipitation. Two typical spaceborne radars for such a study are the W-band Cloud Profiling Radar (CPR) and Ku-band Precipitation Radar (PR), which are onboard NASA's CloudSat and TRMM satellites, respectively. Compared to S-band ground-based radars, they have distinct scattering characteristics for different hydrometeors in clouds and precipitation. The combination of spaceborne and ground-based radar observations can help in the identification of hydrometeors and improve the radar-based quantitative precipitation estimation (QPE). This study analyzes the vertical structure of the 18 January, 2009 storm using data from the CloudSat CPR, TRMM PR, and a NEXRAD-based National Mosaic and Multisensor QPE (NMQ) system. Microphysics above, within, and below the melting layer are studied through an intercomparison of multifrequency measurements. Hydrometeors' type and their radar scattering characteristics are analyzed. Additionally, the study of the vertical profile of reflectivity (VPR) reveals the brightband properties in the cold-season precipitation and its effect on the radar-based QPE. In all, the joint analysis of spaceborne and ground-based radar data increases the understanding of the vertical structure of storm systems and provides a good insight into the microphysical modeling for weather forecasts. PMID:24459424

The impact of lidar elevation uncertainty on mapping intertidal habitats on barrier islands

USGS Publications Warehouse

Enwright, Nicholas M.; Wang, Lei; Borchert, Sinéad M.; Day, Richard H.; Feher, Laura C.; Osland, Michael J.

2018-01-01

While airborne lidar data have revolutionized the spatial resolution that elevations can be realized, data limitations are often magnified in coastal settings. Researchers have found that airborne lidar can have a vertical error as high as 60 cm in densely vegetated intertidal areas. The uncertainty of digital elevation models is often left unaddressed; however, in low-relief environments, such as barrier islands, centimeter differences in elevation can affect exposure to physically demanding abiotic conditions, which greatly influence ecosystem structure and function. In this study, we used airborne lidar elevation data, in situ elevation observations, lidar metadata, and tide gauge information to delineate low-lying lands and the intertidal wetlands on Dauphin Island, a barrier island along the coast of Alabama, USA. We compared three different elevation error treatments, which included leaving error untreated and treatments that used Monte Carlo simulations to incorporate elevation vertical uncertainty using general information from lidar metadata and site-specific Real-Time Kinematic Global Position System data, respectively. To aid researchers in instances where limited information is available for error propagation, we conducted a sensitivity test to assess the effect of minor changes to error and bias. Treatment of error with site-specific observations produced the fewest omission errors, although the treatment using the lidar metadata had the most well-balanced results. The percent coverage of intertidal wetlands was increased by up to 80% when treating the vertical error of the digital elevation models. Based on the results from the sensitivity analysis, it could be reasonable to use error and positive bias values from literature for similar environments, conditions, and lidar acquisition characteristics in the event that collection of site-specific data is not feasible and information in the lidar metadata is insufficient. The methodology presented in this study should increase efficiency and enhance results for habitat mapping and analyses in dynamic, low-relief coastal environments.

Geological factors affecting CO2 plume distribution

USGS Publications Warehouse

Frailey, S.M.; Leetaru, H.

2009-01-01

Understanding the lateral extent of a CO2 plume has important implications with regards to buying/leasing pore volume rights, defining the area of review for an injection permit, determining the extent of an MMV plan, and managing basin-scale sequestration from multiple injection sites. The vertical and lateral distribution of CO2 has implications with regards to estimating CO2 storage volume at a specific site and the pore pressure below the caprock. Geologic and flow characteristics such as effective permeability and porosity, capillary pressure, lateral and vertical permeability anisotropy, geologic structure, and thickness all influence and affect the plume distribution to varying degrees. Depending on the variations in these parameters one may dominate the shape and size of the plume. Additionally, these parameters do not necessarily act independently. A comparison of viscous and gravity forces will determine the degree of vertical and lateral flow. However, this is dependent on formation thickness. For example in a thick zone with injection near the base, the CO2 moves radially from the well but will slow at greater radii and vertical movement will dominate. Generally the CO2 plume will not appreciably move laterally until the caprock or a relatively low permeability interval is contacted by the CO2. Conversely, in a relatively thin zone with the injection interval over nearly the entire zone, near the wellbore the CO2 will be distributed over the entire vertical component and will move laterally much further with minimal vertical movement. Assuming no geologic structure, injecting into a thin zone or into a thick zone immediately under a caprock will result in a larger plume size. With a geologic structure such as an anticline, CO2 plume size may be restricted and injection immediately below the caprock may have less lateral plume growth because the structure will induce downward vertical movement of the CO2 until the outer edge of the plume reaches a spill point within the structure. ?? 2009 Elsevier Ltd. All rights reserved.

Does habitat fragmentation influence nest predation in the shortgrass prairie?

USGS Publications Warehouse

Howard, M.N.; Skagen, S.K.; Kennedy, P.L.

2001-01-01

We examined the effects of habitat fragmentation and vegetation structure of shortgrass prairie and Conservation Reserve Program (CRP) lands on predation rates of artificial and natural nests in northeastern Colorado. The CRP provides federal payments to landowners to take highly erodible cropland out of agricultural production. In our study area, CRP lands have been reseeded primarily with non-native grasses, and this vegetation is taller than native shortgrass prairie. We measured three indices of habitat fragmentation (patch size, degree of matrix fragmentation, and distance from edge), none of which influenced mortality rates of artificial or natural nests. Vegetation structure did influence predation rates of artificial nests; daily mortality decreased significantly with increasing vegetation height. Vegetation structure did not influence predation rates of natural nests. CRP lands and shortgrass sites did not differ with respect to mortality rates of artificial nests. Our study area is only moderately fragmented; 62% of the study area is occupied by native grassland. We conclude that the extent of habitat fragmentation in our study area does not result in increased predation in remaining patches of shortgrass prairie habitat.

Understory structure by season following uneven-aged reproduction cutting: a comparison of selected measures 2 and 6 years after treatment

Treesearch

Victor A. Rudis; Ronald E. Thill; James H. Gramann; Joseph Picone; Nirmala Kalidindi; Philip A. Tappe

1999-01-01

Deciding among cutting practices requires knowledge of forest structure, understory vegetation change, rates of recovery, and resource impacts. The authors used two field devices (a screenometer and a density board) and digital images of 35 mm photographs to compare measures and document the change in understory vegetation structure in forests following reproduction...

Repeatability and implementation of a forest vegetation indicator.

Treesearch

Andrew N. Gray; David L. Azuma

2005-01-01

The composition, diversity, and structure of vascular plants are important indicators of forest health. Changes in species diversity, structural diversity, and the abundance of non-native species are common national concerns, and are part of the international criteria for assessing sustainability of forestry practices. The vegetation indicator for the national Forest...

A geostatistical analysis of small-scale spatial variability in bacterial abundance and community structure in salt marsh creek bank sediments

NASA Technical Reports Server (NTRS)

Franklin, Rima B.; Blum, Linda K.; McComb, Alison C.; Mills, Aaron L.

2002-01-01

Small-scale variations in bacterial abundance and community structure were examined in salt marsh sediments from Virginia's eastern shore. Samples were collected at 5 cm intervals (horizontally) along a 50 cm elevation gradient, over a 215 cm horizontal transect. For each sample, bacterial abundance was determined using acridine orange direct counts and community structure was analyzed using randomly amplified polymorphic DNA fingerprinting of whole-community DNA extracts. A geostatistical analysis was used to determine the degree of spatial autocorrelation among the samples, for each variable and each direction (horizontal and vertical). The proportion of variance in bacterial abundance that could be accounted for by the spatial model was quite high (vertical: 60%, horizontal: 73%); significant autocorrelation was found among samples separated by 25 cm in the vertical direction and up to 115 cm horizontally. In contrast, most of the variability in community structure was not accounted for by simply considering the spatial separation of samples (vertical: 11%, horizontal: 22%), and must reflect variability from other parameters (e.g., variation at other spatial scales, experimental error, or environmental heterogeneity). Microbial community patch size based upon overall similarity in community structure varied between 17 cm (vertical) and 35 cm (horizontal). Overall, variability due to horizontal position (distance from the creek bank) was much smaller than that due to vertical position (elevation) for both community properties assayed. This suggests that processes more correlated with elevation (e.g., drainage and redox potential) vary at a smaller scale (therefore producing smaller patch sizes) than processes controlled by distance from the creek bank. c2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.