Abundance of Green Tree Frogs and Insects in Artificial Canopy Gaps in a Bottomland Hardwood Forest.

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

Horn, Scott; Hanula, James, L.; Ulyshen, Michael D.

2005-04-01

ABSTRACT - We found more green tree frogs ( Hyla cinerea) n canopv gaps than in closed canopy forest. Of the 331 green tree frogs observed, 88% were in canopv gaps. Likewise, higher numbers and biomasses of insects were captured in the open gap habitat Flies were the most commonlv collected insect group accounting for 54% of the total capture. These data suggest that one reason green tree frogs were more abundant in canopy gaps was the increased availability of prey and that small canopy gaps provide early successional habitats that are beneficial to green tree frog populations.

Understory plant development in artificial canopy gaps in an 81-year-old forest stand on Chichagof Island, southeast Alaska

Treesearch

Scott Harris; Jeffrey Barnard

2017-01-01

This study assesses the understory plant response and associated effects on forage resources available to Sitka black-tailed deer (Odocoileus hemionus sitkensis), to the creation of artificial canopy gaps in a young-growth forest stand in the coastal temperate rain forest of southeast Alaska. The forest stand was approximately 58 years old when gaps were created and...

Photosynthetic Potential Of Laurel Oak Seedlings Following Canopy Manipulation

Treesearch

K.W. McLeod

2004-01-01

Abstract The theory of forest gap dynamics predicts that replacement individuals are those that can most fully use the light environment of a gap. Along the Coosawhatchie River in South Carolina, 12 canopy gaps were identified in a bottomland hardwood forest dominated by laurel oak (Quercus laurifolia Michaux). Each gap was...

Landscape-scale effects of fire severity on mixed-conifer and red fir forest structure in Yosemite National Park

USGS Publications Warehouse

Kane, Van R.; Lutz, James A.; Roberts, Susan L.; Smith, Douglas F.; McGaughey, Robert J.; Povak, Nicholas A.; Brooks, Matthew L.

2013-01-01

While fire shapes the structure of forests and acts as a keystone process, the details of how fire modifies forest structure have been difficult to evaluate because of the complexity of interactions between fires and forests. We studied this relationship across 69.2 km2 of Yosemite National Park, USA, that was subject to 32 fires ⩾40 ha between 1984 and 2010. Forests types included ponderosa pine (Pinus ponderosa), white fir-sugar pine (Abies concolor/Pinus lambertiana), and red fir (Abies magnifica). We estimated and stratified burned area by fire severity using the Landsat-derived Relativized differenced Normalized Burn Ratio (RdNBR). Airborne LiDAR data, acquired in July 2010, measured the vertical and horizontal structure of canopy material and landscape patterning of canopy patches and gaps. Increasing fire severity changed structure at the scale of fire severity patches, the arrangement of canopy patches and gaps within fire severity patches, and vertically within tree clumps. Each forest type showed an individual trajectory of structural change with increasing fire severity. As a result, the relationship between estimates of fire severity such as RdNBR and actual changes appears to vary among forest types. We found three arrangements of canopy patches and gaps associated with different fire severities: canopy-gap arrangements in which gaps were enclosed in otherwise continuous canopy (typically unburned and low fire severities); patch-gap arrangements in which tree clumps and gaps alternated and neither dominated (typically moderate fire severity); and open-patch arrangements in which trees were scattered across open areas (typically high fire severity). Compared to stands outside fire perimeters, increasing fire severity generally resulted first in loss of canopy cover in lower height strata and increased number and size of gaps, then in loss of canopy cover in higher height strata, and eventually the transition to open areas with few or no trees. However, the estimated fire severities at which these transitions occurred differed for each forest type. Our work suggests that low severity fire in red fir forests and moderate severity fire in ponderosa pine and white fir-sugar pine forests would restore vertical and horizontal canopy structures believed to have been common prior to the start of widespread fire suppression in the early 1900s. The fusion of LiDAR and Landsat data identified post-fire structural conditions that would not be identified by Landsat alone, suggesting a broad applicability of combining Landsat and LiDAR data for landscape-scale structural analysis for fire management.

Spatial scale and sampling resolution affect measures of gap disturbance in a lowland tropical forest: implications for understanding forest regeneration and carbon storage

PubMed Central

Lobo, Elena; Dalling, James W.

2014-01-01

Treefall gaps play an important role in tropical forest dynamics and in determining above-ground biomass (AGB). However, our understanding of gap disturbance regimes is largely based either on surveys of forest plots that are small relative to spatial variation in gap disturbance, or on satellite imagery, which cannot accurately detect small gaps. We used high-resolution light detection and ranging data from a 1500 ha forest in Panama to: (i) determine how gap disturbance parameters are influenced by study area size, and the criteria used to define gaps; and (ii) to evaluate how accurately previous ground-based canopy height sampling can determine the size and location of gaps. We found that plot-scale disturbance parameters frequently differed significantly from those measured at the landscape-level, and that canopy height thresholds used to define gaps strongly influenced the gap-size distribution, an important metric influencing AGB. Furthermore, simulated ground surveys of canopy height frequently misrepresented the true location of gaps, which may affect conclusions about how relatively small canopy gaps affect successional processes and contribute to the maintenance of diversity. Across site comparisons need to consider how gap definition, scale and spatial resolution affect characterizations of gap disturbance, and its inferred importance for carbon storage and community composition. PMID:24452032

Seedfall and seed viability within artificial canopy gaps in a western Washington douglas-fir forest

Treesearch

Warren D. Devine; Timothy B. Harrington

2015-01-01

Seedfall of coast Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco var. menziesii) has been studied at the forest edge-clearcut interface and in small canopy gaps, but it has not been evaluated in gap sizes that would be typical of a group-selection method of regeneration. In a mature Douglas-fir forest in the Puget Sound...

Regeneration in bottomland forest canopy gaps six years after variable retention harvests to enhance wildlife habitat

USGS Publications Warehouse

Twedt, Daniel J.; Somershoe, Scott G.; Guldin, James M.

2013-01-01

To promote desired forest conditions that enhance wildlife habitat in bottomland forests, managers prescribed and implemented variable-retention harvest, a.k.a. wildlife forestry, in four stands on Tensas River National Wildlife Refuge, LA. These treatments created canopy openings (gaps) within which managers sought to regenerate shade-intolerant trees. Six years after prescribed harvests, we assessed regeneration in 41 canopy gaps and 4 large (>0.5-ha) patch cut openings that resulted from treatments and in 21 natural canopy gaps on 2 unharvested control stands. Mean gap area of anthropogenic gaps (582 m²) was greater than that of natural gaps (262 m²). Sweetgum (Liquidambar styraciflua) and red oaks (Quercus nigra, Q. nuttallii, and Q. phellos) were common in anthropogenic gaps, whereas elms (Ulmus spp.) and sugarberry (Celtis laevigata) were numerous in natural gaps. We recommend harvest prescriptions include gaps with diameter >25 m, because the proportion of shade-intolerant regeneration increased with gap area up to 500 m². The proportion of shade-intolerant definitive gap fillers (individuals likely to occupy the canopy) increased with gap area: 35 percent in natural gaps, 54 percent in anthropogenic gaps, and 84 percent in patch cuts. Sweetgum, green ash (Fraxinus pennsylvanica), and red oaks were common definitive gap fillers.

A long-term study of tree seedling recruitment in Southern Appalachian forests: the effects of canopy gaps and shrub understories

Treesearch

Brian Beckage; James S. Clark; Barton D. Clinton; Bruce L. Haines

2000-01-01

We examined the importance of intermediate-sized gaps and a dense shrub layer on tree seedling recruitment in a Southern Appalachian deciduous forest. We created 12 canopy gaps under two contrasting understory conditions: 6 gaps were dominated by the dense, shade-producing shrub, Rhododendron maximum L., while the remaining gaps were relatively open...

Regeneration Patterns in Canopy Gaps of Mixed-oak Forests of the Southern Appalachians: Influences of Topographic Position and Evergreen Understory

Treesearch

Barton D. Clinton; Lindsay R. Boring; Wayne T. Swank

1994-01-01

Canopy gaps in southern Appalachian mixed-oak forests were assessed for the effects of topographic, gap and stand variables on density of wood seedlings. Seedling density was significantly correlated with percent slope and positively with gap age (l-5 yr). Density varied substantially among topographic positions and increased with gap size. Species richness...

Canopy gap replacement failure in a Pennsylvania forest preserve subject to extreme deer herbivory

Treesearch

Brian S. Pedersen; Angela M. Wallis

2003-01-01

While research has demonstrated the adverse effects of deer herbivory on forest regeneration in forests managed for timber production, less study has been devoted to the long term effects of deer on the dynamics of forests set aside as natural areas. At sufficiently high population densities, deer could interrupt the typical cycle of canopy gap formation and...

Survival of tree seedligns across space and time: estimates from long-term count data

Treesearch

Brian Beckage; Michael Lavina; James S. Clark

2005-01-01

Tree diversity in forests may be maintained by variability in seedling recruitment. Although forest ecologists have emphasized the importance of canopy gaps in generating spatial variability that might promote tree regeneration, the effects of canopy gaps on seedling recruitment may be offset by dense forest understories.Large annual...

Canopy gap size influences niche partitioning of the ground-layer plant community in a northern temperate forest

Treesearch

Christel C. Kern; Rebecca A. Montgomery; Peter B. Reich; Terry F. Strong

2013-01-01

The Gap Partitioning Hypothesis (GPH) posits that gaps create heterogeneity in resources crucial for tree regeneration in closed-canopy forests, allowing trees with contrasting strategies to coexist along resource gradients. Few studies have examined gap partitioning of temperate, ground-layer vascular plants. We used a ground-layer plant community of a temperate...

Comparing terrestrial laser scanning and unmanned aerial vehicle structure from motion to assess top of canopy structure in tropical forests

PubMed Central

Bartholomeus, Harm

2018-01-01

Terrestrial laser scanning (TLS) and unmanned aerial vehicles (UAVs) equipped with digital cameras have attracted much attention from the forestry community as potential tools for forest inventories and forest monitoring. This research fills a knowledge gap about the viability and dissimilarities of using these technologies for measuring the top of canopy structure in tropical forests. In an empirical study with data acquired in a Guyanese tropical forest, we assessed the differences between top of canopy models (TCMs) derived from TLS measurements and from UAV imagery, processed using structure from motion. Firstly, canopy gaps lead to differences in TCMs derived from TLS and UAVs. UAV TCMs overestimate canopy height in gap areas and often fail to represent smaller gaps altogether. Secondly, it was demonstrated that forest change caused by logging can be detected by both TLS and UAV TCMs, although it is better depicted by the TLS. Thirdly, this research shows that both TLS and UAV TCMs are sensitive to the small variations in sensor positions during data collection. TCMs rendered from UAV data acquired over the same area at different moments are more similar (RMSE 0.11–0.63 m for tree height, and 0.14–3.05 m for gap areas) than those rendered from TLS data (RMSE 0.21–1.21 m for trees, and 1.02–2.48 m for gaps). This study provides support for a more informed decision for choosing between TLS and UAV TCMs to assess top of canopy in a tropical forest by advancing our understanding on: (i) how these technologies capture the top of the canopy, (ii) why their ability to reproduce the same model varies over repeated surveying sessions and (iii) general considerations such as the area coverage, costs, fieldwork time and processing requirements needed. PMID:29503719

Comparing terrestrial laser scanning and unmanned aerial vehicle structure from motion to assess top of canopy structure in tropical forests.

PubMed

Roşca, Sabina; Suomalainen, Juha; Bartholomeus, Harm; Herold, Martin

2018-04-06

Terrestrial laser scanning (TLS) and unmanned aerial vehicles (UAVs) equipped with digital cameras have attracted much attention from the forestry community as potential tools for forest inventories and forest monitoring. This research fills a knowledge gap about the viability and dissimilarities of using these technologies for measuring the top of canopy structure in tropical forests. In an empirical study with data acquired in a Guyanese tropical forest, we assessed the differences between top of canopy models (TCMs) derived from TLS measurements and from UAV imagery, processed using structure from motion. Firstly, canopy gaps lead to differences in TCMs derived from TLS and UAVs. UAV TCMs overestimate canopy height in gap areas and often fail to represent smaller gaps altogether. Secondly, it was demonstrated that forest change caused by logging can be detected by both TLS and UAV TCMs, although it is better depicted by the TLS. Thirdly, this research shows that both TLS and UAV TCMs are sensitive to the small variations in sensor positions during data collection. TCMs rendered from UAV data acquired over the same area at different moments are more similar (RMSE 0.11-0.63 m for tree height, and 0.14-3.05 m for gap areas) than those rendered from TLS data (RMSE 0.21-1.21 m for trees, and 1.02-2.48 m for gaps). This study provides support for a more informed decision for choosing between TLS and UAV TCMs to assess top of canopy in a tropical forest by advancing our understanding on: (i) how these technologies capture the top of the canopy, (ii) why their ability to reproduce the same model varies over repeated surveying sessions and (iii) general considerations such as the area coverage, costs, fieldwork time and processing requirements needed.

Canopy gaps affect long-term patterns of tree growth and mortality in mature and old-growth forests in the Pacific Northwest

Treesearch

Andrew N. Gray; Thomas A. Spies; Robert J. Pabst

2012-01-01

Canopy gaps created by tree mortality can affect the speed and trajectory of vegetation growth. Species’ population dynamics, and spatial heterogeneity in mature forests. Most studies focus on plant development within gaps, yet gaps also affect the mortality and growth of surrounding trees, which influence shading and root encroachment into gaps and determine whether,...

Identification of Lightning Gaps in Mangrove Forests Using Airborne LIDAR Measurements

NASA Astrophysics Data System (ADS)

Zhang, K.

2006-12-01

Mangrove forests are highly dynamic ecosystems and change frequently due to tropical storms, frost, and lightning. These factors can cause gaps in mangrove forests by damaging trees. Compared to gaps generated by storms and frost, gaps caused by lightning strikes are small, ranging from 50 to 300 m2. However, these small gaps may play a critical role in mangrove forest dynamics because of the frequent occurrence of lightning in tropical areas. It has been hypothesized that the turnover of mangrove forests is mainly due to the death and regeneration of trees in lightning gaps. However, there is a lack of data for gap occurrence in mangrove forests to verify this hypothesis. It is impractical to measure gaps through a field survey on a large scale because of the logistic difficulties of muddy mangrove forests. Airborne light detection and ranging (LIDAR) technology is an effective alternative because it provides direct measurements of ground and canopy elevations remotely. This study developed a method to identify lightning gaps in mangrove forests in terms of LIDAR measurements. First, LIDAR points are classified into vegetation and ground measurements using the progressive morphological filter. Second, a digital canopy model (DCM) is generated by subtracting a digital terrain model (DTM) from a digital surface model (DSM). The DSM is generated by interpolating raw LIDAR measurements, and DTM is produced by interpolating ground measurements. Third, a black top-hat mathematical morphological transformation is used to identify canopy gaps. Comparison of identified gap polygons with raw LIDAR measurements and field surveys shows that the proposed method identifies lightning gaps in mangrove forests successfully. The area of lightning gaps in mangrove forests in Everglades National Park is about 3% of total forest area, which verifies that lightning gaps play a critical role in mangrove forest turnover.

Seasonal Abundance of Groud-Occurring Macroarthropods in Forest and Canopy Gaps in the Southern Appalachians

Treesearch

Cathryn H. Greenberg; T.G. Forrest

2003-01-01

Arthropods compose a large proportion of biological diversity and play important ecological roles as decomposers, pollinators, predators, prey, and nutrient cyclers. We sampled ground-occurring macroarthropods in intact gaps created by wind disturbance, in salvage-logged gaps, and in closed canopy mature forest (controls) during June 1998-May 1999 using drift fences...

Mapping forest canopy gaps using air-photo interpretation and ground surveys

USGS Publications Warehouse

Fox, T.J.; Knutson, M.G.; Hines, R.K.

2000-01-01

Canopy gaps are important structural components of forested habitats for many wildlife species. Recent improvements in the spatial accuracy of geographic information system tools facilitate accurate mapping of small canopy features such as gaps. We compared canopy-gap maps generated using ground survey methods with those derived from air-photo interpretation. We found that maps created from high-resolution air photos were more accurate than those created from ground surveys. Errors of omission were 25.6% for the ground-survey method and 4.7% for the air-photo method. One variable of inter est in songbird research is the distance from nests to gap edges. Distances from real and simulated nests to gap edges were longer using the ground-survey maps versus the air-photo maps, indicating that gap omission could potentially bias the assessment of spatial relationships. If research or management goals require location and size of canopy gaps and specific information about vegetation structure, we recommend a 2-fold approach. First, canopy gaps can be located and the perimeters defined using 1:15,000-scale or larger aerial photographs and the methods we describe. Mapped gaps can then be field-surveyed to obtain detailed vegetation data.

Regeneration in bottomland forest canopy gaps 6 years after variable retention harvests to enhance wildlife habitat

Treesearch

Daniel J. Twedt; Scott G. Somershoe

2013-01-01

To promote desired forest conditions that enhance wildlife habitat in bottomland forests, managers prescribed and implemented variable-retention harvest, a.k.a. wildlife forestry, in four stands on Tensas River National Wildlife Refuge, LA. These treatments created canopy openings (gaps) within which managers sought to regenerate shade-intolerant trees. Six years after...

Seasonal diets of insectivorous birds using canopy gaps in a bottomland forest

Treesearch

Christopher E. Moorman; Liessa T. Bowen; John C. Kilgo; Clyde E. Sorenson; James L. Hanula; Scott Horn; Mike D. Ulyshen

2007-01-01

Little is known about how insectivorous bird diets are influenced by arthropod availability and about how these relationships vary seasonally. We captured birds in forest-canopy gaps and adjacent mature forest during 2001 and 2002 at the Savannah River Site in Barnwell County, South Carolina, and flushed their crops to gather information about arthropods eaten during...

Influences of Herbivory and Canopy Opening Size on Forest Regeneration in a Southern Bottomland Hardwood Forest

Treesearch

Steven B. Castleberry; W. Mark Ford; Carl V. Miller; Winston P. Smith

2000-01-01

We examined the effects of white-tailed deer (Odocoileus virginianus) browsing and canopy opening size on relative abundance and diversity of woody and herbaceous regeneration in various sized forest openings in a southern, bottomland hardwood forest over three growing seasons (1995-1997). We created 36 canopy openings (gaps), ranging from 7 to 40m...

Guidelines and sample protocol for sampling forest gaps.

Treesearch

J.R. Runkle

1992-01-01

A protocol for sampling forest canopy gaps is presented. Methods used in published gap studies are reviewed. The sample protocol will be useful in developing a broader understanding of forest structure and dynamics through comparative studies across different forest ecosystems.

Assessing fire effects on forest spatial structure using a fusion of Landsat and airborne LiDAR data in Yosemite National Park

USGS Publications Warehouse

Kane, Van R.; North, Malcolm P.; Lutz, James A.; Churchill, Derek J.; Roberts, Susan L.; Smith, Douglas F.; McGaughey, Robert J.; Kane, Jonathan T.; Brooks, Matthew L.

2014-01-01

Mosaics of tree clumps and openings are characteristic of forests dominated by frequent, low- and moderate-severity fires. When restoring these fire-suppressed forests, managers often try to reproduce these structures to increase ecosystem resilience. We examined unburned and burned forest structures for 1937 0.81 ha sample areas in Yosemite National Park, USA. We estimated severity for fires from 1984 to 2010 using the Landsat-derived Relativized differenced Normalized Burn Ratio (RdNBR) and measured openings and canopy clumps in five height strata using airborne LiDAR data. Because our study area lacked concurrent field data, we identified methods to allow structural analysis using LiDAR data alone. We found three spatial structures, canopy-gap, clump-open, and open, that differed in spatial arrangement and proportion of canopy and openings. As fire severity increased, the total area in canopy decreased while the number of clumps increased, creating a patchwork of openings and multistory tree clumps. The presence of openings > 0.3 ha, an approximate minimum gap size needed to favor shade-intolerant pine regeneration, increased rapidly with loss of canopy area. The range and variation of structures for a given fire severity were specific to each forest type. Low- to moderate-severity fires best replicated the historic clump-opening patterns that were common in forests with frequent fire regimes. Our results suggest that managers consider the following goals for their forest restoration: 1) reduce total canopy cover by breaking up large contiguous areas into variable-sized tree clumps and scattered large individual trees; 2) create a range of opening sizes and shapes, including ~ 50% of the open area in gaps > 0.3 ha; 3) create multistory clumps in addition to single story clumps; 4) retain historic densities of large trees; and 5) vary treatments to include canopy-gap, clump-open, and open mosaics across project areas to mimic the range of patterns found for each forest type in our study.

Spatial and temporal dynamics of forest canopy gaps following selective logging in the eastern Amazon.

Treesearch

GREGORY P. ASNER; MICHAEL KELLER; JOSEN M. SILVA

2004-01-01

Selective logging is a dominant form of land use in the Amazon basin and throughout the humid tropics, yet little is known about the spatial variability of forest canopy gap formation and closure following timber harvests. We established chronosequences of large-area (14–158 ha) selective logging sites spanning a 3.5-year period of forest regeneration and two distinct...

Short-Term Responses of Ground Beetles to Forest Changes Caused by Early Stages of Emerald Ash Borer (Coleoptera: Buprestidae)-Induced Ash Mortality.

PubMed

Perry, Kayla I; Herms, Daniel A

2016-04-22

Emerald ash borer (Agrilus planipennis Fairmaire), an invasive wood-boring beetle native to Asia, has killed hundreds of millions of ash trees since its accidental introduction into North America, resulting in widespread formation of canopy gaps and accumulations of coarse woody debris (CWD) in forests. The objective was to quantify effects of canopy gaps and CWD caused by early stages of emerald ash borer-induced ash mortality, and their interaction on ground beetle assemblages. The impact of canopy gaps and CWD varied, as gaps affected beetle assemblages in 2011, while effects of CWD were only observed in 2012. Gaps decreased beetle activity-abundance, and marginally decreased richness, driving changes in species composition, but evenness and diversity were unaffected. Effects of the CWD treatment alone were minimal, but CWD interacted with the canopy treatment, resulting in an increase in activity-abundance of ground beetles in canopy gaps without CWD, and a marginal increase in species richness in canopy gaps with CWD. Although there were some initial changes in species composition, these were ephemeral, suggesting that ground beetle assemblages may be resilient to disturbance caused by emerald ash borer. This study contributes to our understanding of the cascading ecological impacts of biological invasions on forest ecosystems. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Forest Gaps Alter the Total Phenol Dynamics in Decomposing Litter in an Alpine Fir Forest

PubMed Central

Li, Han; Xu, Liya; Wu, Fuzhong; Yang, Wanqin; Ni, Xiangyin; He, Jie; Tan, Bo; Hu, Yi

2016-01-01

The total phenol content in decomposing litter not only acts as a crucial litter quality indicator, but is also closely related to litter humification due to its tight absorption to clay particles. However, limited attention has been focused on the total phenol dynamics in foliar litter in relation to forest gaps. Here, the foliar litter of six representative tree species was incubated on the forest floor from the gap center to the closed canopy of an alpine Minjiang fir (Abies faxoniana) forest in the upper reaches of the Yangtze River and eastern Tibetan Plateau. The dynamics of total phenol concentration in the incubated litter was measured from November 2012 to October 2014. Over two-year incubation, 78.22% to 94.06% of total phenols were lost from the foliar litter, but 52.08% to 86.41% of this occurred in the first year. Forest gaps accelerated the loss of total phenols in the foliar litter in the winter, although they inhibited the loss of total phenols during the growing season in the first year. In comparison with the effects of forest gaps, the variations of litter quality among different species were much stronger on the dynamics of total phenols in the second year. Overall, the loss of total phenols in the foliar litter was slightly higher in both the canopy gap and the expanded gap than in the gap center and under the closed canopy. The results suggest that the predicted decline in snow cover resulting from winter warming or vanishing gaps caused by forest regeneration will retard the loss of total phenol content in the foliar litter of alpine forest ecosystems, especially in the first decomposition year. PMID:26849120

Harvest-created canopy gaps increase species and functional trait diversity of the forest ground-layer community

Treesearch

Christel C. Kern; Rebecca A. Montgomery; Peter B. Reich; Terry F. Strong

2014-01-01

Biodiversity conservation within managed forests depends, in part, on management practices that restore or maintain plant community diversity and function. Because many plant communities are adapted to natural disturbances, gap-based management has potential to meet this need by using the historical range of variation in canopy disturbances to guide elements of harvest...

Variability in snowpack accumulation and ablation associated with mountain pine beetle infestation in western forests

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Harpold, A. A.; Gochis, D. J.; Reed, D.; Brooks, P. D.

2010-12-01

Seasonal snowcover is a primary source of water to urban and agricultural regions in the western United States, where Mountain Pine Beetle (MPB) has caused rapid and extensive changes to vegetation in montane forests. Levels of MPB infestation in these seasonally snow-covered systems are unprecedented, and it is unknown how this will affect water yield, especially in changing climate conditions. To address this unknown we ask: How does snow accumulation and ablation vary across forest with differing levels of impact? Our study areas in the Rocky Mountains of CO and WY are similar in latitude, elevation and forest structure before infestation, but they vary in the intensity and timing of beetle infestation and tree mortality. We present a record for winter 2010 that includes continuous snow depth as well as stand-scale snow surveys at maximum accumulation. Additional measurements include snowfall, net radiation, temperature and wind speed as well as characterization of forest structure by leaf area index. In a stand uninfested by MPB, maximum snow depth was fairly uniform under canopy (mean = 86 cm, coefficient of variation = 0.021), while canopy gaps showed greater and more variable depth (mean = 117 cm, CV = 0.111). This is consistent with several studies demonstrating that snowfall into canopy gaps depends upon gap size, orientation, wind speed and storm size. In a stand impacted in 2007, snow depth under canopy was less uniform, and there were smaller differences in both mean depth and variability between canopy (mean = 93 cm, CV = 0.072) and gaps (mean = 97 cm, CV = 0.070), consistent with decreased canopy density. In a more recently infested (2009) stand with an intermediate level of MPB impact, mean snow depths were similar between canopy (96 cm, CV = 0.016) and gaps (95 cm, CV = 0.185) but gaps showed much greater variability, suggesting controls similar to those in effect in the uninfested stand. We further use these data to model snow accumulation and ablation as a function of vegetation, topography and fine-scale climate variability, with preliminary results presented at the meeting.

Reversing legacy effects in the understory of an oak-dominated forest

Treesearch

Melissa Thomas-Van Gundy; James Rentch; Mary Beth Adams; Walter Carson

2014-01-01

Current forests developed under conditions different from original forests, with higher deer densities, reduced fire frequency, denser canopies, and smaller canopy gaps. These alterations have led to understories dominated by species simultaneously browse tolerant, shade tolerant, and fire sensitive leading to difficulties in the regeneration of oak species (...

Spatial Variation In Growing Season Heat Sums Within Northern Hardwood Forest Canopy Gaps

Treesearch

Brian E. Potter; Paul J. Croft

2000-01-01

When a gap forms in a forest canopy, the first and most immediate effect on the exposed area is an increase in radiative exchange near the ground. More sunlight reaches the ground during the daytime, and at nighttime the ground is more exposed to longwave radiation influences from the sky. These changes in radiation lead directly to a different near-ground temperature...

Leaf-on canopy closure in broadleaf deciduous forests predicted during winter

USGS Publications Warehouse

Twedt, Daniel J.; Ayala, Andrea J.; Shickel, Madeline R.

2015-01-01

Forest canopy influences light transmittance, which in turn affects tree regeneration and survival, thereby having an impact on forest composition and habitat conditions for wildlife. Because leaf area is the primary impediment to light penetration, quantitative estimates of canopy closure are normally made during summer. Studies of forest structure and wildlife habitat that occur during winter, when deciduous trees have shed their leaves, may inaccurately estimate canopy closure. We estimated percent canopy closure during both summer (leaf-on) and winter (leaf-off) in broadleaf deciduous forests in Mississippi and Louisiana using gap light analysis of hemispherical photographs that were obtained during repeat visits to the same locations within bottomland and mesic upland hardwood forests and hardwood plantation forests. We used mixed-model linear regression to predict leaf-on canopy closure from measurements of leaf-off canopy closure, basal area, stem density, and tree height. Competing predictive models all included leaf-off canopy closure (relative importance = 0.93), whereas basal area and stem density, more traditional predictors of canopy closure, had relative model importance of ≤ 0.51.

Gap characteristics of southeastern Ohio second-growth forests

Treesearch

David M. Hix; Katherine K. Helfrich

2003-01-01

Transect sampling was used to assess the features of 30 gaps encountered in upland oak stands on the Wayne National Forest. Tip-ups caused the most canopy gaps (52 percent), two-thirds of which were small (

A Multi-temporal Analysis of Logging Impacts on Tropical Forest Structure Using Airborne Lidar Data

NASA Astrophysics Data System (ADS)

Keller, M. M.; Pinagé, E. R.; Duffy, P.; Longo, M.; dos-Santos, M. N.; Leitold, V.; Morton, D. C.

2017-12-01

The long-term impacts of selective logging on carbon cycling and ecosystem function in tropical-forests are still uncertain. Despite improvements in selective logging detection using satellite data, quantifying changes in forest structure from logging and recovery following logging is difficult using orbital data. We analyzed the dynamics of forest structure comparing logged and unlogged forests in the Eastern Brazilian Amazon (Paragominas Municipality, Pará State) using small footprint discrete return airborne lidar data acquired in 2012 and 2014. Logging operations were conducted at the 1200 ha study site from 2006 through 2013 using reduced impact logging techniques—management practices that minimize canopy and ground damage compared to more common conventional logging. Nevertheless, logging still reduced aboveground biomass by 10% to 20% in logged areas compared to intact forests. We aggregated lidar point-cloud data at spatial scales ranging from 50 m to 250 m and developed a binomial classification model based on the height distribution of lidar returns in 2012 and validated the model against the 2014 lidar acquisition. We accurately classified intact and logged forest classes compared with field data. Classification performance improved as spatial resolution increased (AUC = 0.974 at 250 m). We analyzed the differences in canopy gaps, understory damage (based on a relative density model), and biomass (estimated from total canopy height) of intact and logged classes. As expected, logging greatly increased both canopy gap formation and understory damage. However, while the area identified as canopy gap persisted for at least 8 years (from the oldest logging treatments in 2006 to the most recent lidar acquisition in 2014), the effects of ground damage were mostly erased by vigorous understory regrowth after about 5 years. The rate of new gap formation was 6 to 7 times greater in recently logged forests compared to undisturbed forests. New gaps opened at a rate of 1.8 times greater than background even 8 years following logging demonstrating the occurrence of delayed tree mortality. Our study showed that even low-intensity anthropogenic disturbances can cause persistent changes in tropical forest structure and dynamics.

Forests and Their Canopies: Achievements and Horizons in Canopy Science.

PubMed

Nakamura, Akihiro; Kitching, Roger L; Cao, Min; Creedy, Thomas J; Fayle, Tom M; Freiberg, Martin; Hewitt, C N; Itioka, Takao; Koh, Lian Pin; Ma, Keping; Malhi, Yadvinder; Mitchell, Andrew; Novotny, Vojtech; Ozanne, Claire M P; Song, Liang; Wang, Han; Ashton, Louise A

2017-06-01

Forest canopies are dynamic interfaces between organisms and atmosphere, providing buffered microclimates and complex microhabitats. Canopies form vertically stratified ecosystems interconnected with other strata. Some forest biodiversity patterns and food webs have been documented and measurements of ecophysiology and biogeochemical cycling have allowed analyses of large-scale transfer of CO 2 , water, and trace gases between forests and the atmosphere. However, many knowledge gaps remain. With global research networks and databases, and new technologies and infrastructure, we envisage rapid advances in our understanding of the mechanisms that drive the spatial and temporal dynamics of forests and their canopies. Such understanding is vital for the successful management and conservation of global forests and the ecosystem services they provide to the world. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Avian distribution in treefall gaps and understorey of terra firme forest in the lowland Amazon

Treesearch

JR WUNDERLE; MICHAEL R. WILLIG; LUIZA MAGALLI PINTO HENRIQUES

2005-01-01

We compared the bird distributions in the understorey of treefall gaps and sites with intact canopy in Amazonian terra firme forest in Brazil. We compiled 2216 mist-net captures (116 species) in 32 gap and 32 forest sites over 22.3 months. Gap habitats differed from forest habitats in having higher capture rates, total captures, species richness and diversity....

Measuring spatiotemporal variation in snow optical grain size under a subalpine forest canopy using contact spectroscopy

NASA Astrophysics Data System (ADS)

Molotch, Noah P.; Barnard, David M.; Burns, Sean P.; Painter, Thomas H.

2016-09-01

The distribution of forest cover exerts strong controls on the spatiotemporal distribution of snow accumulation and snowmelt. The physical processes that govern these controls are poorly understood given a lack of detailed measurements of snow states. In this study, we address one of many measurement gaps by using contact spectroscopy to measure snow optical grain size at high spatial resolution in trenches dug between tree boles in a subalpine forest. Trenches were collocated with continuous measurements of snow depth and vertical profiles of snow temperature and supplemented with manual measurements of snow temperature, geometric grain size, grain type, and density from trench walls. There was a distinct difference in snow optical grain size between winter and spring periods. In winter and early spring, when facetted snow crystal types were dominant, snow optical grain size was 6% larger in canopy gaps versus under canopy positions; a difference that was smaller than the measurement uncertainty. By midspring, the magnitude of snow optical grain size differences increased dramatically and patterns of snow optical grain size became highly directional with 34% larger snow grains in areas south versus north of trees. In winter, snow temperature gradients were up to 5-15°C m-1 greater under the canopy due to shallower snow accumulation. However, in canopy gaps, snow depths were greater in fall and early winter and therefore more significant kinetic growth metamorphism occurred relative to under canopy positions, resulting in larger snow grains in canopy gaps. Our findings illustrate the novelty of our method of measuring snow optical grain size, allowing for future studies to advance the understanding of how forest and meteorological conditions interact to impact snowpack evolution.

Seed Regeneration Potential of Canopy Gaps at Early Formation Stage in Temperate Secondary Forests, Northeast China

PubMed Central

Yan, Qiao-Ling; Zhu, Jiao-Jun; Yu, Li-Zhong

2012-01-01

Promoting the seed regeneration potential of secondary forests undergoing gap disturbances is an important approach for achieving forest restoration and sustainable management. Seedling recruitment from seed banks strongly determines the seed regeneration potential, but the process is poorly understood in the gaps of secondary forests. The objectives of the present study were to evaluate the effects of gap size, seed availability, and environmental conditions on the seed regeneration potential in temperate secondary forests. It was found that gap formation could favor the invasion of more varieties of species in seed banks, but it also could speed up the turnover rate of seed banks leading to lower seed densities. Seeds of the dominant species, Fraxinus rhynchophylla, were transient in soil and there was a minor and discontinuous contribution of the seed bank to its seedling emergence. For Quercus mongolica, emerging seedling number was positively correlated with seed density in gaps (R = 0.32, P<0.01), especially in medium and small gaps (<500 m2). Furthermore, under canopies, there was a positive correlation between seedling number and seed density of Acer mono (R = 0.43, P<0.01). Gap formation could promote seedling emergence of two gap-dependent species (i.e., Q. mongolica and A. mono), but the contribution of seed banks to seedlings was below 10% after gap creation. Soil moisture and temperature were the restrictive factors controlling the seedling emergence from seeds in gaps and under canopies, respectively. Thus, the regeneration potential from seed banks is limited after gap formation. PMID:22745771

Differential effects of understory and overstory gaps on tree regeneration

Treesearch

Brian Beckage; Brian D. Kloppel; J. Alan Yenkley; Sharon F. Taylor; David C. Coleman

2008-01-01

Gaps in the forest canopy can increase the diversity of tree regeneration. Understory shrubs also compete with tree seedlings for limited resources and may depress tree recruitment We compared effects of shrub removal and canopy windthrow gups on seedling recruitment and understory resource levels. Shrub removal, with the canopy left intact, was associated with...

Seasonal relationships between birds and arthropods in bottomland forest canopy gaps.

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

Bowen, Liessa, Thomas

2004-12-31

Bowen, Liessa, Thomas. 2004. Seasonal relationships between birds and arthropods in bottomland forest canopy gaps. PhD Dissertation. North Carolina State University. Raleigh, North Carolina. 98pp. I investigated the influence of arthropod availability and vegetation structure on avian habitat use at the center, edge, and adjacent to forest canopy gaps in 2001 and 2002. I used mist-netting and plot counts to estimate abundance of birds using three sizes (0.13, 0.26, and 0.5 ha) of 7-8 year old group-selection timber harvest openings during four seasons (spring migration, breeding, post-breeding, and fall migration) in a bottomland hardwood forest in the Upper Coastal Plainmore » of South Carolina. I used foliage clipping, Malaise trapping, and pitfall trapping to determine arthropod abundance within each habitat, and I used a warm water crop-flush on captured birds to gather information about arthropods eaten. I observed more birds, including forest interior species, forest-edge spedge species, and several individual species, in early-successional canopy gap and gap-edge habitats than in surrounding mature forest during all seasons. I found a significant interaction between season and habitat type for several groups and individual species, suggesting a seasonal shift in habitat use. Captures of all birds, insectivorous birds, foliage- gleaners, ground-gleaners, aerial salliers, Hooded Warbler (Wilsonia citrina), Northern Cardinal (Cardinalis cardinalis), White-eyed Vireo (Vireo griseus), and Black-throated Blue Warbler (Dendroica caerulescens) were positively correlated with understory vegetation density during two or more seasons. I found relationships between insectivorous birds and leaf-dwelling Lepidoptera, insectivorous birds and ground-dwelling arthropods, foliage-gleaning birds and foliage-dwelling arthropods, and aerial salliers and flying arthropods, as well as between individual bird species and arthropods. Relationships were inconsistent, however, with many species being negatively correlated with arthropod abundance. Coleopteran, Lepidopteran, and Aranid prey items represented the greatest proportions of crop-flush samples during all seasons. Proportional consumption of Coleopteran and Hemipteran prey items was higher than their proportional availability, and consumption of Aranid and Hymenopteran prey items was lower than their proportional availability during all seasons. Individual bird species and guilds consistently consumed similar proportions of certain groups of arthropods from spring through fall migration, with no apparent seasonal shift in diet composition. My research suggests that many species of birds selectively choose mid-successional gap and gap-edge habitat over surrounding mature forest during the non-breeding season, and the creation of small canopy gaps within a mature forest may increase local bird species richness. It is less obvious how arthropod availability affects bird habitat use across seasons. A structurally diverse mosaic of habitat types, including regenerating canopy gaps within a mature forest, may provide valuable habitat for birds and a variety of arthropod prey items across multiple seasons.« less

[Response of forest bird communities to forest gap in winter in southwestern China].

PubMed

Zhao, Dong-Dong; Wu, Ying-Huan; Lu, Zhou; Jiang, Guang-Wei; Zhou, Fang

2013-06-01

Although forest gap ecology is an important field of study, research remains limited. By plot setting and point counted observation, the response of birds to forest gaps in winter as well as bird distribution patterns in forest gaps and intact canopies were studied in a north tropical monsoon forest of southwestern China from November 2011 to February 2012 in the Fangcheng Golden Camellia National Nature Reserve, Guangxi. The regression equation of bird species diversity to habitat factor was Y1=0.611+0.002 X13+0.043 X2+0.002 X5-0.003 X8+0.006 X10+0.008 X1 and the regression equation of bird species dominance index to habitat factor was Y3=0.533+0.001 X13+0.019 X2+0.002 X3-0.017 X4+0.002 X1. There were 45 bird species (2 orders and 13 families) recorded in the forest gap, accounting for 84.9% of all birds (n=45), with an average of 9.6 species (range: 2-22). Thirty-nine bird species (5 orders and 14 families) were recorded in non-gap areas, accounting for 73.6% of all birds (n=39), with an average of 5.3 species (range: 1-12). These results suggested that gap size, arbor average height (10 m from gap margin), arbor quantity (10 m from gap margin), shrub quantity (10 m from gap margin), herbal average coverage (1 m from gap margin) and bare land ratio were the key forest gap factors that influenced bird diversities. On the whole, bird diversity in the forest gap was greater than in the intact canopy. Spatial distributions in the forest gaps were also observed in the bird community. Most birds foraged in the "middle" and "canopy" layers in the vertical stratification. In addition, "nearly from" and "close from" contained more birds in relation to horizontal stratification. Feeding niche differentiation was suggested as the main reason for these distribution patterns.

Thirty-two years of change in an old-growth Ohio beech-maple forest.

PubMed

Runkle, James R

2013-05-01

Old-growth forests dominated by understory-tolerant tree species are among forest types most likely to be in equilibrium. However, documentation of the degree to which they are in equilibrium over decades-long time periods is lacking. Changes in climate, pathogens, and land use all are likely to impact stand characteristics and species composition, even in these forests. Here, 32 years of vegetation changes in an old-growth beech (Fagus grandifolia)-sugar maple (Acer saccharum) forest in Hueston Woods, southwest Ohio, USA, are summarized. These changes involve canopy composition and structure, turnover in snags, and development of vegetation in treefall gaps. Stand basal area and canopy density have changed little in 32 years. However, beech has decreased in canopy importance (49% to 32%) while sugar maple has increased (32% to 47%). Annual mortality was about 1.3% throughout the study period. Mortality rates increased with stem size, but the fraction of larger stems increased due to ingrowth from smaller size classes. Beech was represented by more very large stems than small canopy stems: over time, death of those larger stems with inadequate replacement has caused the decrease in beech importance. Sugar maple was represented by more small canopy stems whose growth has increased its importance. The changes in beech and sugar maple relative importance are hypothesized to be due to forest fragmentation mostly from the early 1800s with some possible additional effects associated with the formation of the state park. Snag densities (12-16 snags/ha) and formation rates (1-3 snags.ha(-1).yr(-1)) remained consistent. The treefall gaps previously studied are closing, with a few, large stems remaining. Death of gap border trees occurs consistently enough to favor species able to combine growth in gaps and survival in the understory.

Relating bat species presence to simple habitat measures in a central Appalachian forest

Treesearch

W. Mark Ford; Michael A. Menzel; Jane L. Rodrigue; Jennifer M. Menzel; Joshua B. Johnson; Joshua B. Johnson

2005-01-01

We actively sampled the bat community at 63 sites using detection and non- detection metrics on the Fernow Experimental Forest (FEF) in the central Appalachians of West Virginia using Anabat acoustical equipment May-June 2001-2003 to relate species presence to simple habitat measures such as proximity to riparian areas, forest canopy cover, forest canopy gap width, and...

Nitrogen dynamics across silvicultural canopy gaps in young forests of western Oregon

USGS Publications Warehouse

Thiel, A.L.; Perakis, S.S.

2009-01-01

Silvicultural canopy gaps are emerging as an alternative management tool to accelerate development of complex forest structure in young, even-aged forests of the Pacific Northwest. The effect of gap creation on available nitrogen (N) is of concern to managers because N is often a limiting nutrient in Pacific Northwest forests. We investigated patterns of N availability in the forest floor and upper mineral soil (0-10 cm) across 6-8-year-old silvicultural canopy gaps in three 50-70-year-old Douglas-fir forests spanning a wide range of soil N capital in the Coast Range and Cascade Mountains of western Oregon. We used extractable ammonium (NH4+) and nitrate (NO3-) pools, net N mineralization and nitrification rates, and NH4+ and NO3- ion exchange resin (IER) concentrations to quantify N availability along north-south transects run through the centers of 0.4 and 0.1 ha gaps. In addition, we measured several factors known to influence N availability, including litterfall, moisture, temperature, and decomposition rates. In general, gap-forest differences in N availability were more pronounced in the mineral soil than in the forest floor. Mineral soil extractable NH4+ and NO3- pools, net N mineralization and nitrification rates, and NH4+ and NO3- IER concentrations were all significantly elevated in gaps relative to adjacent forest, and in several cases exhibited significantly greater spatial variability in gaps than forest. Nitrogen availability along the edges of gaps more often resembled levels in the adjacent forest than in gap centers. For the majority of response variables, there were no significant differences between northern and southern transect positions, nor between 0.4 and 0.1 ha gaps. Forest floor and mineral soil gravimetric percent moisture and temperature showed few differences along transects, while litterfall carbon (C) inputs and litterfall C:N ratios in gaps were significantly lower than in the adjacent forest. Reciprocal transfer incubations of mineral soil samples between gap and forest positions revealed that soil originating from gaps had greater net nitrification rates than forest samples, regardless of incubation environment. Overall, our results suggest that increased N availability in 6-8-year-old silvicultural gaps in young western Oregon forests may be due more to the quality and quantity of litterfall inputs resulting from early-seral species colonizing gaps than by changes in temperature and moisture conditions caused by gap creation.

Light, temperature, and soil moisture responses to elevation, evergreen understory, and small canopy gaps in the southern Appalachians

Treesearch

Barton D. Clinton

2003-01-01

Small canopy openings often alter understory microclimate, leading to changes in forest structure and composition. It is generally accepted that physical changes in the understory (i.e., microclimatic) due to canopy removal drive changes in basic forest processes, particularly seedling recruitment which is intrinsically linked to soil moisture availability, light and,...

Response of a boreal forest to canopy opening: assessing vertical and lateral tree growth with multi-temporal lidar data.

PubMed

Vepakomma, Udayalakshmi; St-Onge, Benoit; Kneeshaw, Daniel

2011-01-01

Fine-scale height-growth response of boreal trees to canopy openings is difficult to measure from the ground, and there are important limitations in using stereophotogrammetry in defining gaps and determining individual crowns and height. However, precise knowledge on height growth response to different openings is critical for refining partial harvesting techniques. In this study, we question whether conifers and hardwoods respond equally in terms of sapling growth or lateral growth to openings. We also ask to what distance gaps affect tree growth into the forest. We use multi-temporal lidar to characterize tree/sapling height and lateral growth responses over five years to canopy openings and high resolution images to identify conifers and hardwoods. Species-class-wise height-growth patterns of trees/saplings in various neighborhood contexts were determined across a 6-km matrix of Canadian boreal mixed deciduous coniferous forests. We then use statistical techniques to probe how these growth responses vary by spatial location with respect to the gap edge. Results confirm that both mechanisms of gap closure contribute to the closing of canopies at a rate of 1.2% per annum. Evidence also shows that both hardwood and conifer gap edge trees have a similar lateral growth (average of 22 cm/yr) and similar rates of height growth irrespective of their location and initial height. Height growth of all saplings, however, was strongly dependent on their position within the gap and the size of the gap. Results suggest that hardwood and softwood saplings in gaps have greatest growth rates at distances of 0.5-2 m and 1.5-4 m from the gap edge and in openings smaller than 800 m2 and 250 m2, respectively. Gap effects on the height growth of trees in the intact forest were evident up to 30 m and 20 m from gap edges for hardwood and softwood overstory trees, respectively. Our results thus suggest that foresters should consider silvicultural techniques that create many small openings in mixed coniferous deciduous boreal forests to maximize the growth response of both residual and regenerating trees.

Influence of Canopy Density on Ground Vegetation in a Bottomland Hardwood Forest

Treesearch

Sarah E. Billups

1999-01-01

We investigated the influence of canopy density on ground vegetation in naturally formed gap and non-gap habitats (environments) in a blackwater river floodplain. Tree seedlings were more important (relatively more abundant) in the non-gap habitat, and grass was more important in the gap habitat, but there were elevation x habitat interactions. Also, there was an...

Regional-scale drivers of forest structure and function in northwestern Amazonia.

PubMed

Higgins, Mark A; Asner, Gregory P; Anderson, Christopher B; Martin, Roberta E; Knapp, David E; Tupayachi, Raul; Perez, Eneas; Elespuru, Nydia; Alonso, Alfonso

2015-01-01

Field studies in Amazonia have found a relationship at continental scales between soil fertility and broad trends in forest structure and function. Little is known at regional scales, however, about how discrete patterns in forest structure or functional attributes map onto underlying edaphic or geological patterns. We collected airborne LiDAR (Light Detection and Ranging) data and VSWIR (Visible to Shortwave Infrared) imaging spectroscopy measurements over 600 km2 of northwestern Amazonian lowland forests. We also established 83 inventories of plant species composition and soil properties, distributed between two widespread geological formations. Using these data, we mapped forest structure and canopy reflectance, and compared them to patterns in plant species composition, soils, and underlying geology. We found that variations in soils and species composition explained up to 70% of variation in canopy height, and corresponded to profound changes in forest vertical profiles. We further found that soils and plant species composition explained more than 90% of the variation in canopy reflectance as measured by imaging spectroscopy, indicating edaphic and compositional control of canopy chemical properties. We last found that soils explained between 30% and 70% of the variation in gap frequency in these forests, depending on the height threshold used to define gaps. Our findings indicate that a relatively small number of edaphic and compositional variables, corresponding to underlying geology, may be responsible for variations in canopy structure and chemistry over large expanses of Amazonian forest.

Comparative physiology of a central hardwood old-growth forest canopy and forest gap

Treesearch

A. R. Gillespie; J. Waterman; K. Saylors

1993-01-01

Concerns of poor oak regeneration, changing climate, biodiversity patterns, and carbon cycling in the Central Hardwoods have prompted ecological and physiological studies of old-growth forests and their role in maintaining the landscape. To examine the effects of old-growth canopy structure on the physiological productivity of overstory and understory species, we...

Spatial and temporal patterns of beetles associated with coarse woody debris in managed bottomland hardwood forests

Treesearch

Michael D. Ulyshen; James L. Hanula; Scott Horn; John C. Kilgo; Christopher E. Moorman

2004-01-01

Malaise traps were used to sample beetles in artificial canopy gaps of different size (0.13 ha, 0.26 ha, and 0.50 ha) and age in a South Carolina bottomland hardwood forest. Traps were placed at the center, edge, and in the surrounding forest of each gap. Young gaps (~1 year) had large amounts of coarse woody debris compared to the surrounding forest, while older gaps...

Gap-phase regeneration inlongleaf pine wiregrass ecosystems

Treesearch

D.G. Brockway; K.W. Outcalt

1998-01-01

Naturally regenerated seedlings of longleaf pine are typically observed to cluster in the center of tree fall canopy gaps and be encircled by a wide zone from which they are generally excluded. Twelve representative canopy gaps distributed across 600 ha of a naturally regenerated uneven-agedlongleaf pine forest in the sandhills of north central Florida were examined to...

Arthropod abundance and seasonal bird use of bottomland forest harvest gaps

Treesearch

Christopher E. Moorman; Liessa T. Woen; John C. Kilgo; James L. Hanula; Scott Horn; Michael D. Ulyshen

2012-01-01

We investigated the influence of arthropod abundance and vegetation structure on shifts in avian use of canopy gap, gap edge, and surrounding forest understory in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. We compared captures of foliage-gleaning birds among locations during four periods (spring migration, breeding, post-breeding, and...

Bat activity in selection harvests and intact forest canopy gaps at Indiana state forests

Treesearch

Scott Haulton; Kathryn L. DeCosta

2014-01-01

Forest managers often prescribe silvicultural methods based on how effectively they mimic the natural disturbance agents that have historically shaped the forests they manage. On Indiana state forests, selection systems are used on most harvested acreage and appear to structurally mimic the effects of naturally occurring, gap-forming disturbances affecting individual...

The shifting nature of vegetation controls on peak snowpack with varying slope and aspect

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Harpold, A. A.; Broxton, P. D.; Brooks, P. D.

2012-12-01

The controls on peak seasonal snowpack are known to shift between forested and open environments as well as with slope and aspect. Peak snowpack is predicted well by interception models under uniformly dense canopy, while topography, wind and radiation are strong predictors in open areas. However, many basins have complex mosaics of forest canopy and small gaps, where snowpack controls involve complex interactions among climate, topography and forest structure. In this presentation we use a new fully distributed tree-scale model to investigate vegetation controls on snowpack for a range of slope and aspect, and we evaluate the energy balance in forest canopy and gap environments. The model is informed by airborne LiDAR and ground-based observations of climate, vegetation and snowpack. It represents interception, snow distribution by wind, latent and sensible heat fluxes, and radiative fluxes above and below the canopy at a grid scale of 1 m square on an hourly time step. First, the model is minimally calibrated using continuous records of snow depth and snow water equivalent (SWE). Next, the model is evaluated using distributed observations at peak accumulation. Finally, the domain is synthetically altered to introduce ranges of slope and aspect. Northerly aspects accumulate greater peak SWE than southerly aspects (e.g. 275 mm vs. 250 mm at a slope of 28 %) but show lower spatial variability (e. g. CV = 0.14 vs. CV = 0.17 at slope of 28 %). On northerly aspects, most of the snowpack remains shaded by vegetation, whereas on southerly aspects the northern portions of gaps and southern forest edges receive direct insolation during late winter. This difference in net radiation makes peak SWE in forest gaps and adjacent forest edges more sensitive to topography than SWE in areas under dense canopy. Tree-scale modeling of snow dynamics over synthetic terrain offers extensive possibilities to test interactions among vegetation and topographic controls.

Dynamics of composition and structure in an old Sequoia sempervirens forest

USGS Publications Warehouse

Busing, R.T.; Fujimori, T.

2002-01-01

Dynamics of a Sequoia sempervirens forest in northern California were studied with long-term plot data (1.44 ha) and recent transect data. The study was conducted in an old stand (> 1100 yr) on alluvial flats. Over three decades (1972-2001), changes in the composition and structure of the tree stratum were minor. Sequoia maintained a broad distribution of stem diameters throughout the period. Annual rates of Sequoia mortality (0.0029) and ingrowth (0.0029) were low, reflecting the great longevity of Sequoia and the slow canopy turnover of the study forest. Transect data also indicated a low frequency of canopy gap disturbance (??? 0.4% of total land area per yr), but gap size was potentially large (> 0.1 ha) and the fraction of area in gaps (ca. 20%) was similar to other temperate forests. Regeneration quadrats sampled along transects, in gap centers, and on logs revealed that Sequoia regeneration is elevated at gap edges. The longevity of Sequoia and its response to gap disturbances ensure that it will remain a dominant species in the study forest.

The transient behavior of whole-canopy fluxes during dynamic light conditions for midlatitude and tropical forests

NASA Astrophysics Data System (ADS)

Fitzjarrald, D. R.; Kivalov, S. N.

2017-12-01

Cloud shadows lead to alternating light and dark periods at the surface. Understanding how clouds affect whole-canopy fluxes suffer from two knowledge gaps that limit scaling from leaf to canopy scales, an effort currently done by assertion alone. First, there is a lack a clear quantitative definition of the incident light time series that occur on specific types of cloudy days. Second, the characteristic time scales for leaves to respond to for stomatal opening and closing is 1-10 minutes, a period too short to allow accurate eddy fluxes. We help to close the first gap by linking the durations of alternating light and dark periods statistically to conventional meteorological sky types at a midlatitude mixed deciduous forest (Harvard Forest, MA, USA: 42.53N, 72.17W) and in a tropical rain forest (Tapajós National Forest, Brazil; 2.86S, 54.96W). The second gap is narrowed by measuring the dynamic response whole canopy exchanges in the flux footprint at intervals of only a few seconds using the classical ensemble average method, keying on step changes in light intensity. Combining light and shadow periods of different lengths we estimate ensemble fluxes sensible heat (H), net ecosystem exchange (NEE), and latent heat (LE) fluxes initiated by abrupt radiation changes at intervals of 30 s over 20 minutes. We present composite results of the transient behavior of whole-canopy fluxes at each forest, showing distinct features of each forest type. Observed time constants and transient flux parameterizations are then used to force a simple model to yield NEE, LE, WUE, and Bowen ratio extrema under periodic shadow-light conditions and given cloud amount. We offer the hypothesis that, at least on certain types of cloudy days, the well-known correlation between diffuse light and WUE does not represent a causal connection at the canopy scale.

Regional-Scale Drivers of Forest Structure and Function in Northwestern Amazonia

PubMed Central

Higgins, Mark A.; Asner, Gregory P.; Anderson, Christopher B.; Martin, Roberta E.; Knapp, David E.; Tupayachi, Raul; Perez, Eneas; Elespuru, Nydia; Alonso, Alfonso

2015-01-01

Field studies in Amazonia have found a relationship at continental scales between soil fertility and broad trends in forest structure and function. Little is known at regional scales, however, about how discrete patterns in forest structure or functional attributes map onto underlying edaphic or geological patterns. We collected airborne LiDAR (Light Detection and Ranging) data and VSWIR (Visible to Shortwave Infrared) imaging spectroscopy measurements over 600 km2 of northwestern Amazonian lowland forests. We also established 83 inventories of plant species composition and soil properties, distributed between two widespread geological formations. Using these data, we mapped forest structure and canopy reflectance, and compared them to patterns in plant species composition, soils, and underlying geology. We found that variations in soils and species composition explained up to 70% of variation in canopy height, and corresponded to profound changes in forest vertical profiles. We further found that soils and plant species composition explained more than 90% of the variation in canopy reflectance as measured by imaging spectroscopy, indicating edaphic and compositional control of canopy chemical properties. We last found that soils explained between 30% and 70% of the variation in gap frequency in these forests, depending on the height threshold used to define gaps. Our findings indicate that a relatively small number of edaphic and compositional variables, corresponding to underlying geology, may be responsible for variations in canopy structure and chemistry over large expanses of Amazonian forest. PMID:25793602

The effects of gap size on some microclimate variables during late summer and autumn in a temperate broadleaved deciduous forest.

PubMed

Abd Latif, Zulkiflee; Blackburn, George Alan

2010-03-01

The creation of gaps can strongly influence forest regeneration and habitat diversity within forest ecosystems. However, the precise characteristics of such effects depend, to a large extent, upon the way in which gaps modify microclimate and soil water content. Hence, the aim of this study was to understand the effects of gap creation and variations in gap size on forest microclimate and soil water content. The study site, in North West England, was a mixed temperate broadleaved deciduous forest dominated by mature sessile oak (Quercus petraea), beech (Fagus sylvatica) and ash (Fraxinus excelsior) with some representatives of sycamore (Acer pseudoplatanus). Solar radiation (I), air temperature (T(A)), soil temperature (T(S)), relative humidity (h), wind speed (v) and soil water content (Psi) were measured at four natural treefall gaps created after a severe storm in 2006 and adjacent sub-canopy sites. I, T(A), T(S), and Psi increased significantly with gap size; h was consistently lower in gaps than the sub-canopy but did not vary with gap size, while the variability of v could not be explained by the presence or size of gaps. There were systematic diurnal patterns in all microclimate variables in response to gaps, but no such patterns existed for Psi. These results further our understanding of the abiotic and consequent biotic responses to gaps in broadleaved deciduous forests created by natural treefalls, and provide a useful basis for evaluating the implications of forest management practices.

Seasonal diets of insectivorous birds using canopy gaps in a bottomland forest.

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

Moorman, Christopher, E.; Bowen, Liessa, T.; Kilgo, John, C.

2007-07-01

ABSTRACT. Little is known about how insectivorous bird diets are influenced by arthropod availability and about how these relationships vary seasonally. We captured birds in forest-canopy gaps and adjacent mature forest during 2001 and 2002 at the Savannah River Site in Barnwell County, South Carolina, and flushed their crops to gather information about arthropods eaten during four periods: spring migration, breeding, postbreeding, and fall migration. Arthropod availability for foliage- and ground-gleaning birds was examined by leaf clipping and pitfall trapping. Coleopterans and Hemipterans were used by foliage- and ground-gleaners more than expected during all periods, whereas arthropods in the ordersmore » Araneae and Hymenoptera were used as, or less than, expected based on availability during all periods. Ground-gleaning birds used Homopterans and Lepidopterans in proportions higher than availability during all periods. Arthropod use by birds was consistent from spring through all migration, with no apparent seasonal shift in diet. Based on concurrent studies, heavily used orders of arthropods were equally abundant or slightly less abundant in canopy gaps than in the surrounding mature forest, but bird species were most frequently detected in gaps. Such results suggest that preferential feeding on arthropods by foliage-gleaning birds in p p habitats reduced arthropod densities or, alternatively, that bird use of gap and forest habitat was not determined y food resources. The abundance of arthropods across the stand may have allowed birds to remain in the densely vegetated gaps where thick cover provides protection from predators.« less

Canopy rainfall partitioning across an urbanization gradient in forest structure as characterized by terrestrial LiDAR

NASA Astrophysics Data System (ADS)

Mesta, D. C.; Van Stan, J. T., II; Yankine, S. A.; Cote, J. F.; Jarvis, M. T.; Hildebrandt, A.; Friesen, J.; Maldonado, G.

2017-12-01

As urbanization expands, greater forest area is shifting from natural stand structures to urban stand structures, like forest fragments and landscaped tree rows. Changes in forest canopy structure have been found to drastically alter the amount of rainwater reaching the surface. However, stormwater management models generally treat all forest structures (beyond needle versus broadleaved) similarly. This study examines the rainfall partitioning of Pinus spp. canopies along a natural-to-urban forest gradient and compares these to canopy structural measurements using terrestrial LiDAR. Throughfall and meteorological observations were also used to estimate parameters of the commonly-used Gash interception model. Preliminary findings indicate that as forest structure changed from natural, closed canopy conditions to semi-closed canopy fragments and, ultimately, to exposed urban landscaping tree rows, the interchange between throughfall and rainfall interception also changed. This shift in partitioning between throughfall and rainfall interception may be linked to intuitive parameters, like canopy closure and density, as well as more complex metrics, like the fine-scale patterning of gaps (ie, lacunarity). Thus, results indicate that not all forests of the same species should be treated the same by stormwater models. Rather, their canopy structural characteristics should be used to vary their hydrometeorological interactions.

Frankia and Alnus rubra canopy roots: an assessment of genetic diversity, propagule availability, and effects on soil nitrogen.

PubMed

Kennedy, Peter G; Schouboe, Jesse L; Rogers, Rachel H; Weber, Marjorie G; Nadkarni, Nalini M

2010-02-01

The ecological importance of microbial symbioses in terrestrial soils is widely recognized, but their role in soils that accumulate in forest canopies is almost entirely unknown. To address this gap, this study investigated the Frankia-Alnus rubra symbiosis in canopy and forest floor roots at Olympic National Park, WA, USA. Sixteen mature A. rubra trees were surveyed and Frankia genetic diversity in canopy and forest floor nodules was assessed with sequence-based nifH analyses. A seedling bioassay experiment was conducted to determine Frankia propagule availability in canopy and forest floor soils. Total soil nitrogen from both environments was also quantified. Nodules were present in the canopies of nine of the 16 trees sampled. Across the study area, Frankia canopy and forest floor assemblages were similar, with both habitats containing the same two genotypes. The composition of forest floor and canopy genotypes on the same tree was not always identical, however, suggesting that dispersal was not a strictly local phenomenon. Frankia seedling colonization was similar in canopy soils regardless of the presence of nodules as well as in forest floor soils, indicating that dispersal was not likely to be a major limiting factor. The total soil nitrogen of canopy soils was higher than that of forest floor soils, but the presence of Frankia nodules in canopy soils did not significantly alter soil nitrogen levels. Overall, this study indicates that the Frankia-A. rubra symbiosis is similar in canopy and forest floor environments. Because canopy roots are exposed to different environmental conditions within very small spatial areas and because those areas can be easily manipulated (e.g., fertilizer or watering treatments), they present microbial ecologists with a unique arena to examine root-microbe interactions.

A data-led comparison of simple canopy radiative transfer models for the boreal forest

NASA Astrophysics Data System (ADS)

Reid, T.; Essery, R.; Rutter, N.; King, M.

2012-12-01

Given the computational complexity of numerical weather and climate models, it is worthwhile developing very simple parameterizations for processes such as the transmission of radiation through forest canopies. For this reason, the land surface schemes in global models, and most snow hydrological models, tend to use simple one-dimensional approaches based on Beer's Law or two-stream approximations. Such approaches assume a continuous canopy structure that may not be suitable for the varied, heterogeneous forest cover in boreal regions, especially in winter when snow in the canopy and on the ground may either block radiation or produce multiple reflections between the ground and the trees. There is great benefit in comparing models to real transmissivity values calculated from radiation measurements below and above Arctic canopies. In particular, there is a lack of data for leafless boreal deciduous forests, where canopy gaps are prevalent even at low solar elevation angles near the horizon. In this study, models are compared to radiation data collected in an area of boreal birch forest near Abisko, Sweden in March/April 2011 and mixed conifer forest at Sodankylä, Finland in March/April 2012. Arrays comprising ten shortwave pyranometers were deployed for periods of up to 50 days, under forest plots of varying canopy structures and densities. In addition, global and diffuse shortwave irradiances were recorded at nearby open sites representing the top-of-canopy conditions. A model is developed that explicitly accounts for both diffuse radiation and direct beam transmission on a 5-minute timestep, by using upward-looking hemispherical photographs taken from every pyranometer site. This model reproduces measured transmissivity, although with a slight underestimation, especially at low solar elevations - this could be attributed to multiple reflections that are not accounted for in the model. On the other hand, models based on Beer's Law tend to underestimate the canopy transmissivity significantly, especially for leafless birch canopies where the required assumption of a continuous canopy breaks down. These findings are important for the often sparse, heterogeneous forest cover in boreal regions, where forest edges and canopy gaps are plentiful. They could also have an impact on estimations of overall land surface albedo. Moreover, all models are sensitive to the partitioning of top-of-canopy radiation into its direct and diffuse components, which is complicated by the low solar elevations in the Arctic. More research is required to decide the best way of quantifying the diffuse fraction, using data alongside both physical and empirical models.

A Forest Tent Caterpillar Outbreak Increased Resource Levels and Seedling Growth in a Northern Hardwood Forest.

PubMed

Rozendaal, Danaë M A; Kobe, Richard K

2016-01-01

In closed-canopy forests, gap formation and closure are thought to be major drivers of forest dynamics. Crown defoliation by insects, however, may also influence understory resource levels and thus forest dynamics. We evaluate the effect of a forest tent caterpillar outbreak on understory light availability, soil nutrient levels and tree seedling height growth in six sites with contrasting levels of canopy defoliation in a hardwood forest in northern lower Michigan. We compared resource levels and seedling growth of six hardwood species before, during and in the three years after the outbreak (2008-2012). Canopy openness increased strongly during the forest tent caterpillar outbreak in the four moderately and severely defoliated sites, but not in lightly defoliated sites. Total inorganic soil nitrogen concentrations increased in response to the outbreak in moderately and severely defoliated sites. The increase in total inorganic soil nitrogen was driven by a strong increase in soil nitrate, and tended to become stronger with increasing site defoliation. Seedling height growth increased for all species in the moderately and severely defoliated sites, but not in lightly defoliated sites, either during the outbreak year or in the year after the outbreak. Growth increases did not become stronger with increasing site defoliation, but were strongest in a moderately defoliated site with high soil nutrient levels. Growth increases tended to be strongest for the shade intolerant species Fraxinus americana and Prunus serotina, and the shade tolerant species Ostrya virginiana. The strong growth response of F. americana and P. serotina suggests that recurring forest tent caterpillar outbreaks may facilitate the persistence of shade intolerant species in the understory in the absence of canopy gaps. Overall, our results suggest that recurrent canopy defoliation resulting from cyclical forest insect outbreaks may be an additional driver of dynamics in temperate closed-canopy forests.

A Forest Tent Caterpillar Outbreak Increased Resource Levels and Seedling Growth in a Northern Hardwood Forest

PubMed Central

Rozendaal, Danaë M. A.; Kobe, Richard K.

2016-01-01

In closed-canopy forests, gap formation and closure are thought to be major drivers of forest dynamics. Crown defoliation by insects, however, may also influence understory resource levels and thus forest dynamics. We evaluate the effect of a forest tent caterpillar outbreak on understory light availability, soil nutrient levels and tree seedling height growth in six sites with contrasting levels of canopy defoliation in a hardwood forest in northern lower Michigan. We compared resource levels and seedling growth of six hardwood species before, during and in the three years after the outbreak (2008–2012). Canopy openness increased strongly during the forest tent caterpillar outbreak in the four moderately and severely defoliated sites, but not in lightly defoliated sites. Total inorganic soil nitrogen concentrations increased in response to the outbreak in moderately and severely defoliated sites. The increase in total inorganic soil nitrogen was driven by a strong increase in soil nitrate, and tended to become stronger with increasing site defoliation. Seedling height growth increased for all species in the moderately and severely defoliated sites, but not in lightly defoliated sites, either during the outbreak year or in the year after the outbreak. Growth increases did not become stronger with increasing site defoliation, but were strongest in a moderately defoliated site with high soil nutrient levels. Growth increases tended to be strongest for the shade intolerant species Fraxinus americana and Prunus serotina, and the shade tolerant species Ostrya virginiana. The strong growth response of F. americana and P. serotina suggests that recurring forest tent caterpillar outbreaks may facilitate the persistence of shade intolerant species in the understory in the absence of canopy gaps. Overall, our results suggest that recurrent canopy defoliation resulting from cyclical forest insect outbreaks may be an additional driver of dynamics in temperate closed-canopy forests. PMID:27870897

Challenges facing gap-based silviculture and possible solutions for mesic northern forests in North America

Treesearch

Christel C. Kern; Julia I. Burton; Patricia Raymond; Anthony W. D' Amato; William S. Keeton; Alex Royo; Michael B. Walters; Christopher R. Webster; John L. Willis

2017-01-01

Gap-based silvicultural systems were developed under the assumption that richness, and diversity of tree species and other biota positively respond to variation in size of harvest-created canopy gaps. However, varying gap size alone often does not meet diversity objectives and broader goals to address contemporary forest conditions. Recent research highlights the need...

Landscape Scale Assessment of Predominant Pine Canopy Height for Red-cockaded Woodpecker Habitat Assessment Using Light Detection and Ranging (LIDAR) Data

DTIC Science & Technology

2011-03-26

forest patches extracted from GAP landcover for Fort Bragg study area...7 7 Individual pine forest patches extracted from GAP landcover for Fort Bragg...University for their assis- tance in acquiring Gap Analysis Program (GAP) landcover maps for the study regions. Natalie Myers and James Westervelt of U.S

Forest Gaps Inhibit Foliar Litter Pb and Cd Release in Winter and Inhibit Pb and Cd Accumulation in Growing Season in an Alpine Forest

PubMed Central

He, Jie; Yang, Wanqin; Li, Han; Xu, Liya; Ni, Xiangyin; Tan, Bo; Zhao, Yeyi; Wu, Fuzhong

2015-01-01

Aims The release of heavy metals (such as Pb and Cd) from foliar litter play an important role in element cycling in alpine forest ecosystems. Although natural forest gaps could play important roles in the release of heavy metals from foliar litter by affecting the snow cover during the winter and solar irradiation during the growing season, few studies have examined these potential roles. The objectives of this study were to document changes in Pb and Cd dynamics during litter decomposition in the center of gaps and under closed canopies and to investigate the factors that controlled these changes during the winter and growing seasons. Methods Senesced foliar litter from six dominant species, including Kangding willow (Salix paraplesia), Masters larch (Larix mastersiana), Mingjiang fir (Abies faxoniana), Alpine azalea (Rhododendron lapponicum), Red birch (Betula albosinensis) and Mourning cypress (Sabina saltuaria), was placed in litterbags and incubated between the gap center and closed canopy conditions in an alpine forest in the eastern region of the Tibetan Plateau. The litterbags were sampled at the snow formation stage, snow coverage stage, snow melt stage and during the growing season. The Pb and Cd concentrations in the sampled foliar litter were determined by acid digestion (HNO3/HClO4). Important findings Over one year of decomposition, Pb accumulation and Cd release from the foliar litter occurred, regardless of the foliar litter species. However, Pb and Cd were both released from the foliar litter during the winter and accumulated during the growing season. Compared with the gap center and the canopy gap edge, the extended gap edge and the closed canopy showed higher Pb and Cd release rates in winter and higher Pb and Cd accumulation rates during the growing season, respectively. Statistical analyses indicate that the dynamics of Pb were significantly influenced by frequent freeze–thaw cycles in winter and appropriate hydrothermal conditions during the growing season, the dynamics of Cd were strongly influenced by species and the presence of a forest gap at different decomposition stages. These results show that forest gaps could inhibit Pb and Cd release from foliar litter in the alpine forest of western Sichuan. In addition, a decrease in the snow depth in the winter warming scenario would promote the release of Pb during foliar litter decomposition. There exist some difference that may be influenced by litter quality, microenvironment and microtopography during litter decomposition. PMID:26115012

Forest Gaps Inhibit Foliar Litter Pb and Cd Release in Winter and Inhibit Pb and Cd Accumulation in Growing Season in an Alpine Forest.

PubMed

He, Jie; Yang, Wanqin; Li, Han; Xu, Liya; Ni, Xiangyin; Tan, Bo; Zhao, Yeyi; Wu, Fuzhong

2015-01-01

The release of heavy metals (such as Pb and Cd) from foliar litter play an important role in element cycling in alpine forest ecosystems. Although natural forest gaps could play important roles in the release of heavy metals from foliar litter by affecting the snow cover during the winter and solar irradiation during the growing season, few studies have examined these potential roles. The objectives of this study were to document changes in Pb and Cd dynamics during litter decomposition in the center of gaps and under closed canopies and to investigate the factors that controlled these changes during the winter and growing seasons. Senesced foliar litter from six dominant species, including Kangding willow (Salix paraplesia), Masters larch (Larix mastersiana), Mingjiang fir (Abies faxoniana), Alpine azalea (Rhododendron lapponicum), Red birch (Betula albosinensis) and Mourning cypress (Sabina saltuaria), was placed in litterbags and incubated between the gap center and closed canopy conditions in an alpine forest in the eastern region of the Tibetan Plateau. The litterbags were sampled at the snow formation stage, snow coverage stage, snow melt stage and during the growing season. The Pb and Cd concentrations in the sampled foliar litter were determined by acid digestion (HNO3/HClO4). Over one year of decomposition, Pb accumulation and Cd release from the foliar litter occurred, regardless of the foliar litter species. However, Pb and Cd were both released from the foliar litter during the winter and accumulated during the growing season. Compared with the gap center and the canopy gap edge, the extended gap edge and the closed canopy showed higher Pb and Cd release rates in winter and higher Pb and Cd accumulation rates during the growing season, respectively. Statistical analyses indicate that the dynamics of Pb were significantly influenced by frequent freeze-thaw cycles in winter and appropriate hydrothermal conditions during the growing season, the dynamics of Cd were strongly influenced by species and the presence of a forest gap at different decomposition stages. These results show that forest gaps could inhibit Pb and Cd release from foliar litter in the alpine forest of western Sichuan. In addition, a decrease in the snow depth in the winter warming scenario would promote the release of Pb during foliar litter decomposition. There exist some difference that may be influenced by litter quality, microenvironment and microtopography during litter decomposition.

Gap-based silviculture in a sierran mixed-conifer forest: effects of gap size on early survival and 7-year seedling growth

Treesearch

Robert A. York; John J. Battles; Robert C. Heald

2007-01-01

Experimental canopy gaps ranging in size from 0.1 to 1.0 ha (0.25 to 2.5 acres) were created in a mature mixed conifer forest at Blodgett Forest Research Station, California. Following gap creation, six species were planted in a wagon-wheel design and assessed for survival after two growing seasons. Study trees were measured after seven years to describe the effect of...

Response of reptile and amphibian communities to canopy gaps created by wind disturbance in the Southern Appalachians

Treesearch

Cathryn H. Greenberg

2001-01-01

Reptile and amphibian communities were sampled in intact gaps created by wind disturbance, salvage-logged gaps, and closed canopy mature forest (controls). Sampling was conducted during June–October in 1997 and 1998 using drift fences with pitfall and funnel traps. Basal area of live trees, shade, leaf litter coverage, and litter depth was highest in controls and...

Tree seedlings respond to both light and soil nutrients in a Patagonian evergreen-deciduous forest.

PubMed

Promis, Alvaro; Allen, Robert B

2017-01-01

Seedlings of co-occurring species vary in their response to resource availability and this has implications for the conservation and management of forests. Differential shade-tolerance is thought to influence seedling performance in mixed Nothofagus betuloides-Nothofagus pumilio forests of Patagonia. However, these species also vary in their soil nutrient requirements. To determine the effects of light and soil nutrient resources on small seedlings we examined responses to an experimental reduction in canopy tree root competition through root trenching and restricting soil nutrient depletion through the addition of fertilizer. To understand the effect of light these treatments were undertaken in small canopy gaps and nearby beneath undisturbed canopy with lower light levels. Seedling diameter growth was greater for N. pumilio and height growth was greater for N. betuloides. Overall, diameter and height growth were greater in canopy gaps than beneath undisturbed canopy. Such growths were also greater with fertilizer and root trenching treatments, even beneath undisturbed canopy. Seedling survival was lower under such treatments, potentially reflecting thinning facilitated by resource induced growth. Finally, above-ground biomass did not vary among species although the less shade tolerant N. pumilio had higher below-ground biomass and root to shoot biomass ratio than the more shade tolerant N. betuloides. Above- and below-ground biomass were higher in canopy gaps so that the root to shoot biomass ratio was similar to that beneath undisturbed canopy. Above-ground biomass was also higher with fertilizer and root trenching treatments and that lowered the root to shoot biomass ratio. Restricting soil nutrient depletion allowed seedlings of both species to focus their responses above-ground. Our results support a view that soil nutrient resources, as well as the more commonly studied light resources, are important to seedlings of Nothofagus species occurring on infertile soils.

Snowy backgrounds enhance the absorption of visible light in forest canopies

NASA Astrophysics Data System (ADS)

Pinty, B.; Widlowski, J.-L.; Verstraete, M. M.; Andredakis, I.; Arino, O.; Clerici, M.; Kaminski, T.; Taberner, M.

2011-03-01

The fraction of radiation absorbed in the canopy depends on the amount and angular distribution of the solar irradiance reaching the top of the canopy as well as the fraction of this irradiance that is transmitted through the canopy gaps and reflected back to the vegetation by the background. This contribution shows that the presence of snow on forest floors enhances the fraction of absorbed Photosynthetically Active Radiation (PAR). A global analysis of satellite-derived products reveals that this enhancement affects evergreen and deciduous forests of the boreal zone. This snow-related effect may usefully contribute to the photosynthesis process in evergreen forests especially during spring time when radiation conditions are marginal but other physiological constraints (such as temperature) permit the necessary biochemical functions to take place.

Disturbance and diversity of wood-inhabiting fungi: effects of canopy gaps and downed woody debris

Treesearch

Nicholas J. Brazee; Daniel L. Lindner; Anthony W. D' Amato; Shawn Fraver; Jodi A. Forrester; David J. Mladenoff

2014-01-01

Experimental canopy gap formation and additions of coarse woody debris (CWD) are techniques intended to mimic the disturbance regime and accelerate the development of northern hardwood forests. The effects of these techniques on biodiversity and ecosystem functioning were investigated by surveying the abundance and diversity of wood-inhabiting fungi in six treatments...

Gap locations influence the release of carbon, nitrogen and phosphorus in two shrub foliar litter in an alpine fir forest

PubMed Central

He, Wei; Wu, Fuzhong; Yang, Wanqin; Zhang, Danju; Xu, Zhenfeng; Tan, Bo; Zhao, Yeyi; Justine, Meta Francis

2016-01-01

Gap formation favors the growth of understory plants and affects the decomposition process of plant debris inside and outside of gaps. Little information is available regarding how bioelement release from shrub litter is affected by gap formation during critical periods. The release of carbon (C), nitrogen (N), and phosphorus (P) in the foliar litter of Fargesia nitida and Salix paraplesia in response to gap locations was determined in an alpine forest of the eastern Qinghai-Tibet Plateau via a 2-year litter decomposition experiment. The daily release rates of C, N, and P increased from the closed canopy to the gap centers during the two winters, the two later growing seasons and the entire 2 years, whereas this trend was reversed during the two early growing seasons. The pairwise ratios among C, N, and P converged as the litter decomposition proceeded. Compared with the closed canopy, the gap centers displayed higher C:P and N:P ratio but a lower C:N ratio as the decomposition proceeded. Alpine forest gaps accelerate the release of C, N, and P in decomposing shrub litter, implying that reduced snow cover resulting from vanishing gaps may inhibit the release of these elements in alpine forests. PMID:26906762

Disturbance and canopy gaps as indicators of forest health in the Blue Mountains of Oregon.

Treesearch

Jerome S. Beatty; Brian W. Geils; John E. Lundquist

1995-01-01

Disturbance profiles, indices based on both spatial and non-spatial statistics, are used to examine how small-scale disturbances and the resulting canopy gaps disrupt ecosystem patterns and processes in selected stands in the Blue Mountains of Oregon. The biological meaning of many indices remains undefined for small scale disturbance phenomena, but their disturbance...

Predation on Artificial Nests in Hurricane-Created Gaps and Adjacent Forest of the Southern Appalachians

Treesearch

Cathryn H. Greenberg; C. Reed Rossell; David B. Johnson

2002-01-01

Predation rates were compared during three 7-day trials on 742 artificial ground nests located in 10 hurricane-created canopy gaps and IO adjacent closed-canopy controls in the southern Appalachian mountains of North Carolina. White northern bobwhite (Colinus virginianus) eggs were used in trials 1 and 2, but brown-speckled Japanese Quail (...

Harvest-related edge effects on prey availability and foraging of hooded warblers in a bottomland hardwood forest

Treesearch

John C. Kilgo

2005-01-01

The effects of harvest-created canopy gaps in bottomland hardwood forests on arthropod abundance and, hence, the foraging ecology of birds are poorly understood. I predicted that arthropod abundance would be high near edges of group-selection harvest gaps and lower in the surrounding forest, and that male Hooded Warblers (Wilsonia citrina) foraging...

Demographic disequilibrium caused by canopy gap expansion and recruitment failure triggers forest cover loss

Treesearch

Martin Barrette; Louis Bélanger; Louis De Grandpré; Alejandro A. Royo

2017-01-01

In the absence of large-scale stand replacing disturbances, boreal forests can remain in the old-growth stage over time because of a dynamic equilibrium between small-scale mortality and regeneration processes. Although this gap paradigm has been a cornerstone of forest dynamics theory and practice for decades, evidence suggests that it could be disrupted, threatening...

Regenerating oak-dominated forests using irregular, gap-based silvicultural systems

Treesearch

John M. Lhotka; Michael R. Saunders; John M. Kabrick; Daniel C. Dey

2013-01-01

Throughout the Eastern United States, practitioners have primarily focused on using uniformly applied even-aged approaches to regenerate oak species. Irregular, gap-based silvicultural systems offer an alternative that retains continuous canopy cover, creates heterogeneous forest structure, and provides multiple income flows over a rotation. Although commonly used in...

Effects of Late Stages of Emerald Ash Borer (Coleoptera: Buprestidae)-Induced Ash Mortality on Forest Floor Invertebrate Communities

PubMed Central

Herms, Daniel A

2017-01-01

Abstract Emerald ash borer (EAB; Agrilus planipennis Fairmaire) is an invasive wood-borer causing rapid, widespread ash tree mortality, formation of canopy gaps, and accumulation of coarse woody debris (CWD) in forest ecosystems. The objective of this study was to quantify the effects of canopy gaps and ash CWD on forest floor invertebrate communities during late stages of EAB-induced ash mortality, when the effects of gaps are predicted to be smallest and effects of CWD are predicted to be greatest, according to the model proposed by Perry and Herms 2016a. A 2-year study was conducted in forest stands that had experienced nearly 100% ash mortality in southeastern Michigan, USA, near where EAB first established in North America. In contrast to patterns documented during early stages of the EAB invasion, effects of gaps were minimal during late stages of ash mortality, but invertebrate communities were affected by accumulation and decomposition of CWD. Invertebrate activity-abundance, evenness, and diversity were highest near minimally decayed logs (decay class 1), but diverse taxon-specific responses to CWD affected community composition. Soil moisture class emerged as an important factor structuring invertebrate communities, often mediating the strength and direction of their responses to CWD and stages of decomposition. The results of this study were consistent with the predictions that the effects of CWD on invertebrate communities would be greater than those of canopy gaps during late stages of EAB-induced ash mortality. This research contributes to understanding of the cascading and long-term ecological impacts of invasive species on native forest ecosystems.

Soricid response to canopy gaps created by wind disturbance in the Southern Appalachians

Treesearch

Cathryn H. Greenberg; Stanlee Miller

2004-01-01

We used drift fences with pitfall traps to compare soricid abundance, richness, and demographic parameters among intact multiple-tree windthrow gaps, salvaged gaps, and mature forest in a xeric southern Appalachian forest type during 1997-1999. We also tested whether capture rates were correlated with rainfall, and whether similar-sized species did not co-occur as...

Numerical Study of the Response of an Atmospheric Surface Layer to a Spatially Nonuniform Plant Canopy

NASA Astrophysics Data System (ADS)

Qiu, J.; Gu, Z. L.; Wang, Z. S.

2008-05-01

High-accuracy large-eddy simulations of neutral atmospheric surface-layer flow over a gapped plant canopy strip have been performed. Subgrid-scale (SGS) motions are parameterized by the Sagaut mixed length SGS model, with a modification to compute the SGS characteristic length self-adaptively. Shaw’s plant canopy model, taking the vertical variation of leaf area density into account, is applied to study the response of the atmospheric surface layer to the gapped dense forest strip. Differences in the region far away from the gap and in the middle of the gap are investigated, according to the instantaneous velocity magnitude, the zero-plane displacement, the potential temperature and the streamlines. The large-scale vortex structure, in the form of a roll vortex, is revealed in the region far away from the gap. The nonuniform spatial distribution of plants appears to cause the formation of the coherent structure. The roll vortex starts in the wake of the canopy, and results in strong fluctuations throughout the entire canopy region. Wind sweeps and ejections in the plant canopy are also attributed to the large vortex structure.

Enhanced light use efficiency as a mechanism for forest carbon storage resilience following disturbance

NASA Astrophysics Data System (ADS)

Gough, C. M.; Hardiman, B. S.; Bohrer, G.; Maurer, K.; Nave, L. E.; Vogel, C. S.; Curtis, P.; University of Michigan Biological Station Forest Ecosystem STudy (FEST) Team

2011-12-01

Disturbances to forests such as those caused by herbivory, wind, pathogens, and age-related mortality may subtly alter canopy structure, with variable consequences for carbon (C) cycling. Forest C storage resilience following disturbance in which only a fraction of the canopy is defoliated may depend upon canopy structural shifts that compensate for lost leaf area by improving the efficiency of light-use by the altered canopy. In a forest at the University of Michigan Biological Station that is regionally representative of the northern Great Lakes, we initiated an experiment that examines forest C storage following subtle canopy disturbance. The Forest Accelerated Succession ExperimenT (FASET), in which >6,700 aspen and birch trees (~35 % LAI) were stem girdled within a 39 ha area, is investigating how C storage changes as Great Lakes forests broadly undergo a transition in which early successional canopy trees die and give way to an assemblage of later successional canopy dominants. The experiment employs a suite of paired C cycling measurements within separate treatment and control meteorological flux tower footprints. Forest carbon storage, quantified as annual net ecosystem production (NEP) and net primary production (NPP), was resilient to partial canopy defoliation, with rapid structural changes improving canopy light-use efficiency (LUE). Declining aspen and birch leaf area was offset by new foliar growth from later successional species already present in the canopy; however, the distribution of foliage within the canopy became more heterogeneous following disturbance as patchy aspen and birch mortality produced gaps and the vertical structure of the forest diversified. These canopy structural alterations prompted by small-scale patchy disturbance may have permitted deeper light penetration into the canopy, decreasing the fraction of absorbed photosynthetically active radiation (PAR) while increasing the efficiency in which absorbed light was used to drive canopy C uptake. The result was little change in forest C storage in the first several years following disturbance. We conclude that forest C storage resilience depends not only on replacement of lost leaf area, but also on shifts in forest structure that permit greater efficiency of light-use to drive C storage. These findings suggest that structural changes in the canopy should be considered in addition to trajectories of leaf area recovery when predicting the extent and duration of disturbance-related shifts in forest C storage.

Tracking the Creation of Tropical Forest Canopy Gaps with UAV Computer Vision Remote Sensing

NASA Astrophysics Data System (ADS)

Dandois, J. P.

2015-12-01

The formation of canopy gaps is fundamental for shaping forest structure and is an important component of ecosystem function. Recent time-series of airborne LIDAR have shown great promise for improving understanding of the spatial distribution and size of forest gaps. However, such work typically looks at gap formation across multiple years and important intra-annual variation in gap dynamics remains unknown. Here we present findings on the intra-annual dynamics of canopy gap formation within the 50 ha forest dynamics plot of Barro Colorado Island (BCI), Panama based on unmanned aerial vehicle (UAV) remote sensing. High-resolution imagery (7 cm GSD) over the 50 ha plot was obtained regularly (≈ every 10 days) beginning October 2014 using a UAV equipped with a point and shoot camera. Imagery was processed into three-dimensional (3D) digital surface models (DSMs) using automated computer vision structure from motion / photogrammetric methods. New gaps that formed between each UAV flight were identified by subtracting DSMs between each interval and identifying areas of large deviation. A total of 48 new gaps were detected from 2014-10-02 to 2015-07-23, with sizes ranging from less than 20 m2 to greater than 350 m2. The creation of new gaps was also evaluated across wet and dry seasons with 4.5 new gaps detected per month in the dry season (Jan. - May) and 5.2 per month outside the dry season (Oct. - Jan. & May - July). The incidence of gap formation was positively correlated with ground-surveyed liana stem density (R2 = 0.77, p < 0.001) at the 1 hectare scale. Further research will consider the role of climate in predicting gap formation frequency as well as site history and other edaphic factors. Future satellite missions capable of observing vegetation structure at greater extents and frequencies than airborne observations will be greatly enhanced by the high spatial and temporal resolution bridging scale made possible by UAV remote sensing.

Arthropod abundance and seasonal bird use of bottomland forest harvest gaps.

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

Moorman, Christopher, E.; Bowen, Liessa T.; Kilgo, John, C.

2012-03-01

We investigated the influence of arthropod abundance and vegetation structure on shifts in avian use of canopy gap, gap edge, and surrounding forest understory in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. We compared captures of foliage-gleaning birds among locations during four periods (spring migration, breeding, post-breeding, and fall migration). Foliage arthropod densities were greatest in the forest understory in all four seasons, but understory vegetation density was greatest in gaps. Foliage-gleaning bird abundance was positively associated with foliage-dwelling arthropods during the breeding (F = 18.5, P < 0.001) and post-breeding periods (F = 9.4,more » P = 0.004), and negatively associated with foliage-dwelling arthropods during fall migration (F = 5.4, P = 0.03). Relationships between birds and arthropods were inconsistent, but the arthropod prey base seemed to be least important during migratory periods. Conversely, bird captures were positively correlated with understory vegetation density during all four periods (P < 0.001). Our study suggests high bird abundance associated with canopy gaps during the non-breeding period resulted less from high arthropod food resource availability than from complex understory and midstory vegetation structure.« less

Throughfall-mediated alterations to soil microbial community structure in a forest plot of homogenous soil texture, litter, and plant species composition

NASA Astrophysics Data System (ADS)

Van Stan, John; Rosier, Carl; Moore, Leslie; Gay, Trent; Reichard, James; Wu, Tiehang; Kan, Jinjun

2015-04-01

Identifying spatiotemporal influences on soil microbial community (SMC) structure is critical to our understanding of patterns in biogeochemical cycling and related ecological services (e.g., plant community structure, water quality, response to environmental change). Since forest canopy structure alters the spatiotemporal patterning of precipitation water and solute supplies to soils (via "throughfall"), is it possible that changes in SMC structure could arise from modifications in canopy elements? Our study investigates this question by monitoring throughfall water and dissolved ion supply to soils beneath a continuum of canopy structure: from large gaps (0% cover), to bare Quercus virginiana Mill. (southern live oak) canopy (~50-70%), to heavy Tillandsia usneoides L. (Spanish moss) canopy (>90% cover). Throughfall water supply diminished with increasing canopy cover, yet increased washoff/leaching of Na+, Cl-, PO43-, and SO42- from the canopy to the soils. Presence of T. usneoides diminished throughfall NO3-, but enhanced NH4+, concentrations supplied to subcanopy soils. The mineral soil horizon (0-10 cm) sampled in triplicate from locations receiving throughfall water and solutes from canopy gaps, bare canopy, and T. usneoides-laden canopy significantly differed in soil chemistry parameters (pH, Ca2+, Mg2+, CEC). Polymerase Chain Reaction-Denaturant Gradient Gel Electrophoresis (PCR-DGGE) banding patterns beneath similar canopy covers (experiencing similar throughfall dynamics) also produced high similarities per ANalyses Of SIMilarity (ANO-SIM), and clustered together when analyzed by Nonmetric Multidimensional Scaling (NMDS). These results suggest that modifications of forest canopy structures are capable of affecting mineral-soil horizon SMC structure via throughfall when canopies' biomass distribution is highly heterogeneous. As SMC structure, in many instances, relates to functional diversity, we suggest that future research seek to identify functional diversity shifts (e.g., nitrogen transformation) in response to canopy structural alterations of throughfall water/solute concentration

Forest canopy structural controls over throughfall affect soil microbial community structure in an epiphyte-laden maritime oak stand

NASA Astrophysics Data System (ADS)

Van Stan, J. T., II; Rosier, C. L.; Schrom, J. O.; Wu, T.; Reichard, J. S.; Kan, J.

2014-12-01

Identifying spatiotemporal influences on soil microbial community (SMC) structure is critical to understanding of patterns in nutrient cycling and related ecological services. Since forest canopy structure alters the spatiotemporal patterning of precipitation water and solute supplies to soils (via the "throughfall" mechanism), is it possible changes in SMC structure variability could arise from modifications in canopy elements? Our study investigates this question by monitoring throughfall water and dissolved ion supply to soils beneath a continuum of canopy structure: from a large gap (0% cover) to heavy Tillandsia usneoides L. (Spanish moss) canopy (>90% cover). Throughfall water supply diminished with increasing canopy cover, yet increased washoff/leaching of Na+, Cl-, PO43-, and SO42- from the canopy to the soils (p < 0.01). Presence of T. usneoides diminished throughfall NO3-, but enhanced NH4+, concentrations supplied to subcanopy soils. The mineral soil horizon (0-10 cm) from canopy gaps, bare canopy, and T. usneoides-laden canopy significantly differed (p < 0.05) in soil chemistry parameters (pH, Ca2+, Mg2+, CEC). PCR-DGGE banding patterns beneath similar canopy covers (experiencing similar throughfall dynamics) also produced high similarities per ANalyses Of SIMilarity (ANO-SIM), and clustered together when analyzed by Nonmetric Multidimensional Scaling (NMDS). Correlation analysis of DGGE banding patterns, throughfall dynamics, and soil chemistry yielded significant correlations (p < 0.05) between fungal communities and soil chemical properties significantly differing between canopy cover types (pH: r2 = 0.50; H+ %-base saturation: r2 = 0.48; Ca2+ %-base saturation: r2 = 0.43). Bacterial community structure correlated with throughfall NO3-, NH4+, and Ca2+ concentrations (r2 = 0.37, p = 0.16). These results suggest that modifications of forest canopy structures are capable of affecting mineral-soil horizon SMC structure via the throughfall mechanism when canopies' biomass distribution is highly heterogeneous.

Response of pin cherry to fire, canopy disturbance, and deer herbivory on the Westvaco Wildlife and Ecosystem Research Forest

Treesearch

David W. McGill; Rachel J. Collins; Walter P. Carson

2003-01-01

We studied the impact of fire, canopy disturbance, and deer herbivory on the germination and development of pin cherry in four Appalachian hardwood stands located on the Westvaco Wildlife and Ecosystem Research Forest in Randolph County, West Virginia. Plots with simulated gaps and woven-wire fences were used to evaluate impacts of light and deer on regeneration. All...

The Legacy of Episodic Climatic Events in Shaping Temperate, Broadleaf Forests

NASA Technical Reports Server (NTRS)

Pederson, Neil; Dyer, James M.; McEwan, Ryan W.; Hessl, Amy E.; Mock, Cary J.; Orwig, David A.; Rieder, Harald E.; Cook, Benjamin I.

2015-01-01

In humid, broadleaf-dominated forests where gap dynamics and partial canopy mortality appears to dominate the disturbance regime at local scales, paleoecological evidence shows alteration at regional-scales associated with climatic change. Yet, little evidence of these broad-scale events exists in extant forests. To evaluate the potential for the occurrence of large-scale disturbance, we used 76 tree-ring collections spanning approx. 840 000 sq km and 5327 tree recruitment dates spanning approx. 1.4 million sq km across the humid eastern United States. Rotated principal component analysis indicated a common growth pattern of a simultaneous reduction in competition in 22 populations across 61 000 km2. Growth-release analysis of these populations reveals an intense and coherent canopy disturbance from 1775 to 1780, peaking in 1776. The resulting time series of canopy disturbance is so poorly described by a Gaussian distribution that it can be described as ''heavy tailed,'' with most of the years from 1775 to 1780 comprising the heavy-tail portion of the distribution. Historical documents provide no evidence that hurricanes or ice storms triggered the 1775-1780 event. Instead, we identify a significant relationship between prior drought and years with elevated rates of disturbance with an intense drought occurring from 1772 to 1775. We further find that years with high rates of canopy disturbance have a propensity to create larger canopy gaps indicating repeated opportunities for rapid change in species composition beyond the landscape scale. Evidence of elevated, regional-scale disturbance reveals how rare events can potentially alter system trajectory: a substantial portion of old-growth forests examined here originated or were substantially altered more than two centuries ago following events lasting just a few years. Our recruitment data, comprised of at least 21 species and several shade-intolerant species, document a pulse of tree recruitment at the subcontinental scale during the late-1600s suggesting that this event was severe enough to open large canopy gaps. These disturbances and their climatic drivers support the hypothesis that punctuated, episodic, climatic events impart a legacy in broadleaf-dominated forests centuries after their occurrence. Given projections of future drought, these results also reveal the potential for abrupt, meso- to large-scale forest change in broadleaf-dominated forests over future decades.

Detection and Distribution of Natural Gaps in Tropical Rainforest

NASA Astrophysics Data System (ADS)

Goulamoussène, Y.; Linguet, L.; Hérault, B.

2014-12-01

Forest management is important to assess biodiversity and ecological processes. Requirements for disturbance information have also been motivated by the scientific community. Therefore, understanding and monitoring the distribution frequencies of treefall gaps is relevant to better understanding and predicting the carbon budget in response to global change and land use change. In this work we characterize and quantify the frequency distribution of natural canopy gaps. We observe then interaction between environment variables and gap formation across tropical rainforest of the French Guiana region by using high resolution airborne Light Detection and Ranging (LiDAR). We mapped gaps with canopy model distribution on 40000 ha of forest. We used a Bayesian modelling framework to estimate and select useful covariate model parameters. Topographic variables are included in a model to predict gap size distribution. We discuss results from the interaction between environment and gap size distribution, mainly topographic indexes. The use of both airborne and space-based techniques has improved our ability to supply needed disturbance information. This work is an approach at plot scale. The use of satellite data will allow us to work at forest scale. The inclusion of climate variables in our model will let us assess the impact of global change on tropical rainforest.

Contrasting Patterns of Damage and Recovery in Logged Amazon Forests From Small Footprint LiDAR Data

NASA Technical Reports Server (NTRS)

Morton, D. C.; Keller, M.; Cook, B. D.; Hunter, Maria; Sales, Marcio; Spinelli, L.; Victoria, D.; Andersen, H.-E.; Saleska, S.

2012-01-01

Tropical forests ecosystems respond dynamically to climate variability and disturbances on time scales of minutes to millennia. To date, our knowledge of disturbance and recovery processes in tropical forests is derived almost exclusively from networks of forest inventory plots. These plots typically sample small areas (less than or equal to 1 ha) in conservation units that are protected from logging and fire. Amazon forests with frequent disturbances from human activity remain under-studied. Ongoing negotiations on REDD+ (Reducing Emissions from Deforestation and Forest Degradation plus enhancing forest carbon stocks) have placed additional emphasis on identifying degraded forests and quantifying changing carbon stocks in both degraded and intact tropical forests. We evaluated patterns of forest disturbance and recovery at four -1000 ha sites in the Brazilian Amazon using small footprint LiDAR data and coincident field measurements. Large area coverage with airborne LiDAR data in 2011-2012 included logged and unmanaged areas in Cotriguacu (Mato Grosso), Fiona do Jamari (Rondonia), and Floresta Estadual do Antimary (Acre), and unmanaged forest within Reserva Ducke (Amazonas). Logging infrastructure (skid trails, log decks, and roads) was identified using LiDAR returns from understory vegetation and validated based on field data. At each logged site, canopy gaps from logging activity and LiDAR metrics of canopy heights were used to quantify differences in forest structure between logged and unlogged areas. Contrasting patterns of harvesting operations and canopy damages at the three logged sites reflect different levels of pre-harvest planning (i.e., informal logging compared to state or national logging concessions), harvest intensity, and site conditions. Finally, we used multi-temporal LiDAR data from two sites, Reserva Ducke (2009, 2012) and Antimary (2010, 2011), to evaluate gap phase dynamics in unmanaged forest areas. The rates and patterns of canopy gap formation at these sites illustrate potential issues for separating logging damages from natural forest disturbances over longer time scales. Multi-temporal airborne LiDAR data and coincident field measurements provide complementary perspectives on disturbance and recovery processes in intact and degraded Amazon forests. Compared to forest inventory plots, the large size of each individual site permitted analyses of landscape-scale processes that would require extremely high investments to study using traditional forest inventory methods.

Microclimatic and soil moisture responses to gap formation in coastal Douglas-fir forests

Treesearch

Andrew N Gray; Thomas A Spies; Mark J Easter

2002-01-01

The effects of gap formation on solar radiation, soil and air temperature, and soil moisture were studied in mature coniferous forests of the Pacific Northwest, U.S.A. Measurements were taken over a 6-year period in closed-canopy areas and recently created gaps in four stands of mature (90–140 years) and old-growth (>400 years) Douglas-fir (Pseudotsuga...

BOREAS TE-6 Multiband Vegetation Imager Data

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Kucharik, Christopher J.

2000-01-01

The BOREAS TE-6 team collected data in support of its efforts to examine the influence of vegetation and climate on the major carbon fluxes in boreal tree species. A newly developed ground-based canopy imaging system called an MVI was tested and used by the BOREAS TE-06 team to collect measurements of the canopy crap fraction (sky fraction), canopy gap-size distribution (size and frequency of gaps between foliage in canopy), branch architecture, and leaf angle distribution (fraction of leaf area in specific leaf inclination classes assuming azimuthal symmetry). Measurements of the canopy gap-size distribution are used to derive canopy clumping indices that can be used to adjust indirect LAI measurements made in nonrandom forests. These clumping factors will also help to describe the radiation penetration in clumped canopies more accurately by allowing for simple adjustments to Beer's law. Measurements of the above quantities were obtained at BOREAS NSA-OJP site in IFC-2 in 1994, at the SSA-OA in July 1995, and at the SSA-OBS and SSA-OA sites in IFC-2 in 1996. Modeling studies were also performed to further validate MVI measurements and to gain a more complete understanding of boreal forest canopy architecture. By using MVI measurements and Monte Carlo simulations, clumping indices as a function of zenith angle were derived for the three main boreal species studied during BOREAS. The analyzed data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distrobuted Activity Archive Center (DAAC).

Light-driven growth in Amazon evergreen forests explained by seasonal variations of vertical canopy structure.

PubMed

Tang, Hao; Dubayah, Ralph

2017-03-07

Light-regime variability is an important limiting factor constraining tree growth in tropical forests. However, there is considerable debate about whether radiation-induced green-up during the dry season is real, or an apparent artifact of the remote-sensing techniques used to infer seasonal changes in canopy leaf area. Direct and widespread observations of vertical canopy structures that drive radiation regimes have been largely absent. Here we analyze seasonal dynamic patterns between the canopy and understory layers in Amazon evergreen forests using observations of vertical canopy structure from a spaceborne lidar. We discovered that net leaf flushing of the canopy layer mainly occurs in early dry season, and is followed by net abscission in late dry season that coincides with increasing leaf area of the understory layer. Our observations of understory development from lidar either weakly respond to or are not correlated to seasonal variations in precipitation or insolation, but are strongly related to the seasonal structural dynamics of the canopy layer. We hypothesize that understory growth is driven by increased light gaps caused by seasonal variations of the canopy. This light-regime variability that exists in both spatial and temporal domains can better reveal the drought-induced green-up phenomenon, which appears less obvious when treating the Amazon forests as a whole.

High-resolution LIDAR and ground observations of snow cover in a complex forested terrain in the Sierra Nevada - implications for optical remote sensing of seasonal snow.

NASA Astrophysics Data System (ADS)

Kostadinov, T. S.; Harpold, A.; Hill, R.; McGwire, K.

2017-12-01

Seasonal snow cover is a key component of the hydrologic regime in many regions of the world, especially those in temperate latitudes with mountainous terrain and dry summers. Such regions support large human populations which depend on the mountain snowpack for their water supplies. It is thus important to quantify snow cover accurately and continuously in these regions. Optical remote-sensing methods are able to detect snow and leverage space-borne spectroradiometers with global coverage such as MODIS to produce global snow cover maps. However, snow is harder to detect accurately in mountainous forested terrain, where topography influences retrieval algorithms, and importantly - forest canopies complicate radiative transfer and obfuscate the snow. Current satellite snow cover algorithms assume that fractional snow-covered area (fSCA) under the canopy is the same as the fSCA in the visible portion of the pixel. In-situ observations and first principles considerations indicate otherwise, therefore there is a need for improvement of the under-canopy correction of snow cover. Here, we leverage multiple LIDAR overflights and in-situ observations with a distributed fiber-optic temperature sensor (DTS) to quantify snow cover under canopy as opposed to gap areas at the Sagehen Experimental Forest in the Northern Sierra Nevada, California, USA. Snow-off LIDAR overflights from 2014 are used to create a baseline high-resolution digital elevation model and classify pixels at 1 m resolution as canopy-covered or gap. Low canopy pixels are excluded from the analysis. Snow-on LIDAR overflights conducted by the Airborne Snow Observatory in 2016 are then used to classify all pixels as snow-covered or not and quantify fSCA under canopies vs. in gap areas over the Sagehen watershed. DTS observations are classified as snow-covered or not based on diel temperature fluctuations and used as validation for the LIDAR observations. LIDAR- and DTS-derived fSCA is also compared with retrievals from hyperspectral imaging spectroradiometer (AVIRIS) data. Initial evidence suggest fSCA was generally lower under canopy and that overall snow cover estimates were overestimated as a result. Implications for a canopy correction applicable to coarser-resolution sensors like MODIS are discussed, as are topography and view angle effects.

Disturbance, life history traits, and dynamics in an old-growth forest landscape of southeastern Europe.

PubMed

Nagel, Thomas A; Svoboda, Miroslav; Kobal, Milan

2014-06-01

Much of our understanding of natural forest dynamics in the temperate region of Europe is based on observational studies in old-growth remnants that have emphasized small-scale gap dynamics and equilibrium stand structure and composition. Relatively little attention has been given to the role of infrequent disturbance events in forest dynamics. In this study, we analyzed dendroecological data from four stands and three windthrow patches in an old-growth landscape in the Dinaric Mountains of Bosnia and Herzegovina to examine disturbance history, tree life history traits, and compositional dynamics. Over all stands, most decades during the past 340 years experienced less than 10% canopy loss, yet each stand showed evidence of periodic intermediate-severity disturbances that removed > 40% of the canopy, some of which were synchronized over the study area landscape. Analysis of radial growth patterns indicated several life history differences among the dominant canopy trees; beech was markedly older than fir, while growth patterns of dead and dying trees suggested that fir was able to tolerate longer periods of suppressed growth in shade. Maple had the fastest radial growth and accessed the canopy primarily through rapid early growth in canopy gaps, whereas most beech and fir experienced a period of suppressed growth prior to canopy accession. Peaks in disturbance were roughly linked to increased recruitment, but mainly of shade-tolerant beech and fir; less tolerant species (i.e., maple, ash, and elm) recruited successfully on some of the windthown sites where advance regeneration of beech and fir was less abundant. The results challenge the traditional notions of stability in temperate old-growth forests of Europe and highlight the nonequilibrial nature of canopy composition due to unique histories of disturbance and tree life history differences. These findings provide valuable information for developing natural disturbance-based silvicultural systems, as well as insight into maintaining less shade-tolerant, but valuable broadleaved trees in temperate forests of Europe.

Herbivorous insect response to group selection cutting in a southeastern bottomland hardwood forest

Treesearch

Michael D. Ulyshen; James L. Hanula; Scott Horn; John C. Kilgo; Christopher E. Moorman

2005-01-01

Malaise and pitfall traps were used to sample herbivorous insects in canopy gaps created by group-selection cutting in a bottomland hardwood forest in South Carolina. The traps were placed at the centers, edges, and in the forest adjacent to gaps of different sizes (0.13, 0.26, and 0.50 ha) and ages (1 and 7 yr old) during four sampling periods in 2001. Overall, the...

Prospects for quantifying structure, floristic composition and species richness of tropical forests

USGS Publications Warehouse

Gillespie, T.W.; Brock, J.; Wright, C.W.

2004-01-01

Airborne spectral and light detection and ranging (lidar) sensors have been used to quantify biophysical characteristics of tropical forests. Lidar sensors have provided high-resolution data on forest height, canopy topography, volume, and gap size; and provided estimates on number of strata in a forest, successional status of forests, and above-ground biomass. Spectral sensors have provided data on vegetation types, foliar biochemistry content of forest canopies, tree and canopy phenology, and spectral signatures for selected tree species. A number of advances are theoretically possible with individual and combined spectral and lidar sensors for the study of forest structure, floristic composition and species richness. Delineating individual canopies of over-storey trees with small footprint lidar and discrimination of tree architectural types with waveform distributions is possible and would provide scientists with a new method to study tropical forest structure. Combined spectral and lidar data can be used to identify selected tree species and identify the successional status of tropical forest fragments in order to rank forest patches by levels of species richness. It should be possible in the near future to quantify selected patterns of tropical forests at a higher resolution than can currently be undertaken in the field or from space. ?? 2004 Taylor and Francis Ltd.

Vegetation and Ecological Characteristics of Mixed-Conifer and Red Fir Forests at the Teakettle Experimental Forest

Treesearch

Malcolm North; Brian Oakley; Jiquan Chen; Heather Erickson; Andrew Gray; Antonio Izzo; Dale Johnson; Siyan Ma; Jim Marra; Marc Meyer; Kathryn Purcell; Tom Rambo; Dave Rizzo; Brent Roath; Tim Schowalter

2002-01-01

Detailed analysis of mixed-conifer and red fir forests were made from extensive, large vegetation sampling, systematically conducted throughout the Teakettle Experimental Forest. Mixed conifer is characterized by distinct patch conditions of closed-canopy tree clusters, persistent gaps and shrub thickets. This heterogeneous spatial structure provides contrasting...

Pervasive interactions between ungulate browsers and disturbance regimes promote temperate forest herbaceous diversity.

PubMed

Royo, Alejandro A; Collins, Rachel; Adams, Mary Beth; Kirschbaum, Chad; Carson, Walter P

2010-01-01

Disruptions to historic disturbance and herbivory regimes have altered plant assemblages in forests worldwide. An emerging consensus suggests that these disruptions often result in impoverished forest biotas. This is particularly true for eastern U.S. deciduous forests where large gaps and understory fires were once relatively common and browsers were far less abundant. Although much research has focused on how disturbance and browsers affect tree diversity, far less attention has been devoted to forest understories where the vast majority (>75%) of the vascular species reside. Here we test the hypothesis that the reintroduction of disturbances resembling historic disturbance regimes and moderate levels of ungulate browsing enhance plant diversity. We explore whether once-common disturbances and their interaction with the top-down influence of browsers can create conditions favorable for the maintenance of a rich herbaceous layer in a region recognized as a temperate biodiversity hotspot in West Virginia, U.S.A. We tested this hypothesis via a factorial experiment whereby we manipulated canopy gaps (presence/absence) of a size typically found in old-growth stands, low-intensity understory fire (burned/unburned), and deer browsing (fenced/unfenced). We tracked the abundance and diversity of more than 140 herb species for six years. Interactions among our treatments were pervasive. The combination of canopy gaps and understory fire increased herbaceous layer richness, cover, and diversity well beyond either disturbance alone. Furthermore, we documented evidence that deer at moderate levels of abundance promote herbaceous richness and abundance by preferentially browsing fast-growing pioneer species that thrive following co-occurring disturbances (i.e., fire and gaps). This finding sharply contrasts with the negative impact browsers have when their populations reach levels well beyond those that occurred for centuries. Although speculative, our results suggest that interactions among fire, canopy gaps, and browsing provided a variable set of habitats and conditions across the landscape that was potentially capable of maintaining much of the plant diversity found in temperate forests.

Soil respiration patterns in root gaps 27 years after small scale experimental disturbance in Pinus contorta forests

NASA Astrophysics Data System (ADS)

Baker, S.; Berryman, E.; Hawbaker, T. J.; Ewers, B. E.

2015-12-01

While much attention has been focused on large scale forest disturbances such as fire, harvesting, drought and insect attacks, small scale forest disturbances that create gaps in forest canopies and below ground root and mycorrhizal networks may accumulate to impact regional scale carbon budgets. In a lodgepole pine (Pinus contorta) forest near Fox Park, WY, clusters of 15 and 30 trees were removed in 1988 to assess the effect of tree gap disturbance on fine root density and nitrogen transformation. Twenty seven years later the gaps remain with limited regeneration present only in the center of the 30 tree plots, beyond the influence of roots from adjacent intact trees. Soil respiration was measured in the summer of 2015 to assess the influence of these disturbances on carbon cycling in Pinus contorta forests. Positions at the centers of experimental disturbances were found to have the lowest respiration rates (mean 2.45 μmol C/m2/s, standard error 0.17 C/m2/s), control plots in the undisturbed forest were highest (mean 4.15 μmol C/m2/s, standard error 0.63 C/m2/s), and positions near the margin of the disturbance were intermediate (mean 3.7 μmol C/m2/s, standard error 0.34 C/m2/s). Fine root densities, soil nitrogen, and microclimate changes were also measured and played an important role in respiration rates of disturbed plots. This demonstrates that a long-term effect on carbon cycling occurs when gaps are created in the canopy and root network of lodgepole forests.

Management guidelines for enhancing Cerulean Warbler breeding habitat in Appalachian hardwood forests

USGS Publications Warehouse

Wood, Petra; Sheehan, James; Keyser, Patrick D.; Buehler, David A.; Larkin, Jeff; Rodewald, Amanda D.; Stoleson, Scott H.; Wigley, T. Bently; Mizel, Jeremy; Boves, Than J.; George, Greg; Bakermans, Marja H.; Beachy, Tiffany A.; Evans, Andrea; McDermott, Molly E.; Newell, Felicity L.; Perkins, Kelly A.; White, Matt

2013-01-01

The Cerulean Warbler (Setophaga cerulea) is a migratory songbird that breeds in mature deciduous forests of eastern North America. Cerulean Warblers (hereafter, ceruleans) require heavily forested landscapes for nesting and, within Appalachian forests, primarily occur on ridge tops and steep, upper slopes. They are generally associated with oakdominated (Quercus spp.) stands that contain gaps in the forest canopy, that have large diameter trees (>16 inches diameter breast height (dbh)), and that have well-developed understory-and upper-canopy layers. Ceruleans primarily use the midand upper-canopy where they glean insects from the surface of leaves and conceal their open cup nests. Because they are severely declining across much of their range (Fig. 1), habitat management is a high priority. Management for this species can also improve conditions for a number of other wildlife species that depend on the same structure.

Rapid assessment of forest canopy and light regime using smartphone hemispherical photography.

PubMed

Bianchi, Simone; Cahalan, Christine; Hale, Sophie; Gibbons, James Michael

2017-12-01

Hemispherical photography (HP), implemented with cameras equipped with "fisheye" lenses, is a widely used method for describing forest canopies and light regimes. A promising technological advance is the availability of low-cost fisheye lenses for smartphone cameras. However, smartphone camera sensors cannot record a full hemisphere. We investigate whether smartphone HP is a cheaper and faster but still adequate operational alternative to traditional cameras for describing forest canopies and light regimes. We collected hemispherical pictures with both smartphone and traditional cameras in 223 forest sample points, across different overstory species and canopy densities. The smartphone image acquisition followed a faster and simpler protocol than that for the traditional camera. We automatically thresholded all images. We processed the traditional camera images for Canopy Openness (CO) and Site Factor estimation. For smartphone images, we took two pictures with different orientations per point and used two processing protocols: (i) we estimated and averaged total canopy gap from the two single pictures, and (ii) merging the two pictures together, we formed images closer to full hemispheres and estimated from them CO and Site Factors. We compared the same parameters obtained from different cameras and estimated generalized linear mixed models (GLMMs) between them. Total canopy gap estimated from the first processing protocol for smartphone pictures was on average significantly higher than CO estimated from traditional camera images, although with a consistent bias. Canopy Openness and Site Factors estimated from merged smartphone pictures of the second processing protocol were on average significantly higher than those from traditional cameras images, although with relatively little absolute differences and scatter. Smartphone HP is an acceptable alternative to HP using traditional cameras, providing similar results with a faster and cheaper methodology. Smartphone outputs can be directly used as they are for ecological studies, or converted with specific models for a better comparison to traditional cameras.

Potential effects of forest management on surface albedo

NASA Astrophysics Data System (ADS)

Otto, J.; Bréon, F.-M.; Schelhaas, M.-J.; Pinty, B.; Luyssaert, S.

2012-04-01

Currently 70% of the world's forests are managed and this figure is likely to rise due to population growth and increasing demand for wood based products. Forest management has been put forward by the Kyoto-Protocol as one of the key instruments in mitigating climate change. For temperate and boreal forests, the effects of forest management on the stand-level carbon balance are reasonably well understood, but the biophysical effects, for example through changes in the albedo, remain elusive. Following a modeling approach, we aim to quantify the variability in albedo that can be attributed to forest management through changes in canopy structure and density. The modelling approach chains three separate models: (1) a forest gap model to describe stand dynamics, (2) a Monte-Carlo model to estimate the probability density function of the optical path length of photons through the canopy and (3) a physically-based canopy transfer model to estimate the interaction between photons and leaves. The forest gap model provides, on a monthly time step the position, height, diameter, crown size and leaf area index of individual trees. The Monte-Carlo model computes from this the probability density function of the distance a photon travels through crown volumes to determine the direct light reaching the forest floor. This information is needed by the canopy transfer model to calculate the effective leaf area index - a quantity that allows it to correctly represent a 3D process with a 1D model. Outgoing radiation is calculated as the result of multiple processes involving the scattering due to the canopy layer and the forest floor. Finally, surface albedo is computed as the ratio between incident solar radiation and calculated outgoing radiation. The study used two time series representing thinning from below of a beech and a Scots pine forest. The results show a strong temporal evolution in albedo during stand establishment followed by a relatively stable albedo once the canopy is closed. During this period, albedo is affected for a short time by forest operations. The modelling approach allowed us to estimate the importance of ground vegetation in the stand albedo. Given that ground vegetation depends on the light reaching the forest floor, ground vegetation could act as a natural buffer to dampen changes in albedo, allowing the stand to maintain optimal leaf temperature. Consequently, accounting for only the carbon balance component of forest management ignores albedo impacts and is thus likely to yield biased estimates of the climate benefits of forest ecosystems.

New gap-filling and partitioning technique for H2O eddy fluxes measured over forests

NASA Astrophysics Data System (ADS)

Kang, Minseok; Kim, Joon; Malla Thakuri, Bindu; Chun, Junghwa; Cho, Chunho

2018-01-01

The continuous measurement of H2O fluxes using the eddy covariance (EC) technique is still challenging for forests because of large amounts of wet canopy evaporation (EWC), which occur during and following rain events when the EC systems rarely work correctly. We propose a new gap-filling and partitioning technique for the H2O fluxes: a model-statistics hybrid (MSH) method. It enables the recovery of the missing EWC in the traditional gap-filling method and the partitioning of the evapotranspiration (ET) into transpiration and (wet canopy) evaporation. We tested and validated the new method using the data sets from two flux towers, which are located at forests in hilly and complex terrains. The MSH reasonably recovered the missing EWC of 16-41 mm yr-1 and separated it from the ET (14-23 % of the annual ET). Additionally, we illustrated certain advantages of the proposed technique which enable us to understand better how ET responds to environmental changes and how the water cycle is connected to the carbon cycle in a forest ecosystem.

The response of ground beetles (Coleoptera: Carabidae) to selection cutting in a South Carolina bottomland hardwood forest

Treesearch

Michael D. Ulyshen; James L. Hanula; Scott Horn; John C. Kilgo; Christopher E. Moorman

2005-01-01

We compared the response of ground beetles (Coleoptera: Carabidae) to the creation of canopy gaps of different size (0.13, 0.26, and 0.50 ha) and age (1 and 7 years) in a bottomland hardwood forest (South Carolina, USA). Samples were collected four times in 2001 by malaise and pitfall traps placed at the center and edge of each gap, and 50 m into the surrounding forest...

Forest influences on snow accumulation and snowmelt at the Hubbard Brook Experimental Forest, New Hampshire, USA

Treesearch

Colin A. Penn; Beverley C. Wemple; John L. Campbell

2012-01-01

Many factors influence snow depth, water content and duration in forest ecosystems. The effects of forest cover and canopy gap geometry on snow accumulation has been well documented in coniferous forests of western North America and other regions; however, few studies have evaluated these effects on snowpack dynamics in mixed deciduous forests of the northeastern USA....

Impact of typhoon disturbance on the diversity of key ecosystem engineers in a monoculture mangrove forest plantation, Can Gio Biosphere Reserve, Vietnam

NASA Astrophysics Data System (ADS)

Diele, K.; Tran Ngoc, D. M.; Geist, S. J.; Meyer, F. W.; Pham, Q. H.; Saint-Paul, U.; Tran, T.; Berger, U.

2013-11-01

Mangrove crabs as key ecosystem engineers may play an important role in the recovery process of storm-damaged forests. Yet, their response to storm disturbance is largely unknown. Here we compare the ground-dwelling brachyuran crab community of intact mangrove stands with that of typhoon gaps having experienced 100% tree mortality. Field work was conducted in two adjacent areas in Can Gio Biosphere Reserve, southern Vietnam. In each area, an 18-20 yr old monoculture Rhizophora apiculata stand served as control and was compared with typhoon gaps where downed stems had been removed or left on-site. The gaps were 14 and 20 months old when studied in the dry and rainy season 2008, respectively. Time-based sampling of ground-dwelling crabs with hand or shovel was conducted by 4 persons inside 100 m2 plots for 30 min (7 replicate plots per area, treatment and month). Abiotic (sediment pH, salinity, temperature, grain size, water content, carbon and nitrogen content), and biotic measures (e.g. canopy coverage, woody debris, number of trees, leaf litter) were also taken. Despite complete canopy loss, total crab abundance has not changed significantly (in contrast to biomass) and all 12 species found in the forest were also found in the gaps, demonstrating their robustness. Another 9 gap-exclusive species were recorded and average species number and Shannon diversity were thus higher in the gaps. Perisesarma eumolpe was the most abundant species, both in the forest and in the gaps, and a shift from sesarmids (typical forest species) to ocypodids (generally more prominent in open areas) has not occurred. The persistence of litter-feeding sesarmid crabs prior to the re-establishment of a mangrove canopy is likely to depend on the availability of woody debris on the ground of the gaps, fuelling a mangrove detritus based food web, rather than one based on microphytobenthos and deposit-feeding ocypodids. The presence of burrowing crabs in the gaps suggests that important ecosystem engineering activities are still performed. However, bioturbation may be reduced as crab biomass and body size were smaller in the gaps. Follow-up assessments and field experiments are needed to understand the crabs' role in processing the woody debris, their long-term community dynamics and possible feed-backs between species shifts and gap regeneration.

A Review and Evaluation of Forest Canopy Epiphyte Roles in the Partitioning and Chemical Alteration of Precipitation

NASA Astrophysics Data System (ADS)

Van Stan, J. T., II; Pypker, T. G.

2015-12-01

Interactions between precipitation and forest canopy elements (bark, leaves, and epiphytes) control the quantity, spatiotemporal patterning, and the chemical concentration, character and constituency of precipitation to soils. Canopy epiphytes are an element that exerts a range of storm-related hydrological and biogeochemical effects due to their diversity of morphological traits and nutrient acquisition mechanisms. We reviewed and evaluated the state of knowledge regarding epiphyte interactions with precipitation partitioning (into interception loss, throughfall, and stemflow) and the chemical alteration of net precipitation fluxes (throughfall and stemflow). As epiphyte species are quite diverse, this review categorized findings by common paraphyletic groups: lichens, bryophytes, and vascular epiphytes. Of these groups, vascular epiphytes have received the least attention and lichens the most. In general, epiphytes decrease throughfall and stemflow and increase interception loss. Epiphytes alter the spatiotemporal pattern of throughfall and increase the overall latent heat fluxes from the canopy. Epiphytes alter biogeochemical processes by impacting the transfer of solutes through the canopy; however, the change in solute concentration varies with epiphyte type and chemical species. We discuss several important knowledge gaps across all epiphyte groups. We also explore innovative methods that currently exist to confront these knowledge gaps and past techniques applied to gain our current understanding. Future research addressing the listed deficiencies will improve our knowledge of epiphyte roles in water and biogeochemical processes coupled within forest canopies—processes crucial to supporting microbe, plant, vertebrate and invertebrate communities within individual epiphytes/epiphyte assemblages, host trees, and even the forest ecosystem as a whole.

Beyond edge effects: landscape controls on forest structure in the southeastern US

NASA Astrophysics Data System (ADS)

Fagan, M. E.; Morton, D. C.; Cook, B.; Masek, J. G.; Zhao, F. A.; Nelson, R.; Huang, C.

2016-12-01

The structure of forest canopies (i.e., their height and complexity) is known to be influenced by a variety of factors, including forest age, species composition, disturbance, edaphic and topographical conditions, and exposure to edge environments. The combined impact of each of these factors on canopy structure is not well characterized for most forest ecosystems, however, which limits our ability to predict the regional impacts of forest fragmentation. The objective of this study was to elucidate the main biophysical drivers of canopy structure across two dominant ecosystems in the southeastern U.S: natural mixed deciduous forests, and industrial conifer plantations. We analyzed spatial changes in canopy structure along aerial transects of LiDAR data ( 3,000 km in all). High-resolution (1 m) LiDAR data from Goddard's LiDAR, Hyperspectral, and Thermal Airborne Imager (G-LiHT) were combined with time series of Landsat imagery to quantify forest type, age, composition, and fragmentation. Forest structural metrics (height, gap fraction, and canopy roughness) were examined across forest types, ages, topography, and decreasing edge exposure. We hypothesized that 1) structural edge effects would be weak in both natural and plantation forest types, and 2) age, composition, and topography would be the dominant influences on natural forest structure. We analyzed all large (>4 ha) fragments from the 8562 distinct forests measured during G-LiHT data collections in 2011 across the southeastern U.S. In general, the relationship between forest structural metrics and edge exposure was highly variable in both natural forests and plantations. However, variability in all structural metrics decreased with distance from an edge. Forest age and topography were strong predictors of canopy structure in natural forests. However plantations tended to be located in sites with limited topographical variation, and thinning disturbances of conifer plantations decreased the strength of the age-structure relationship. We found that canopy structure in our region is influenced by edge effects, but other factors played a larger role in determining forest characteristics. Our results highlight the importance of endogenous, stand-specific processes for forest structure, biomass, and biodiversity in the southeastern U.S.

Forest structure of oak plantations after silvicultural treatment to enhance habitat for wildlife

USGS Publications Warehouse

Twedt, Daniel J.; Phillip, Cherrie-Lee P.; Guilfoyle, Michael P.; Wilson, R. Randy; Schweitzer, Callie Jo; Clatterbuck, Wayne K.; Oswalt, Christopher M.

2016-01-01

During the past 30 years, thousands of hectares of oak-dominated bottomland hardwood plantations have been planted on agricultural fields in the Mississippi Alluvial Valley. Many of these plantations now have closed canopies and sparse understories. Silvicultural treatments could create a more heterogeneous forest structure, with canopy gaps and increased understory vegetation for wildlife. Lack of volume sufficient for commercial harvest in hardwood plantations has impeded treatments, but demand for woody biomass for energy production may provide a viable means to introduce disturbance beneficial for wildlife. We assessed forest structure in response to prescribed pre-commercial perturbations in hardwood plantations resulting from silvicultural treatments: 1) row thinning by felling every fourth planted row; 2) multiple patch cuts with canopy gaps of <1 0.25 – 2 ha; and 3) tree removal on intersecting corridors diagonal to planted rows. These 3 treatments, and an untreated control, were applied to oak plantations (20 - 30 years post-planting) on three National Wildlife Refuges (Cache River, AR; Grand Cote, LA; and Yazoo, MS) during summer 2010. We sampled habitat using fixed-radius plots in 2009 (pre-treatment) and in 2012 (post-treatment) at random locations. Retained basal area was least in diagonal corridor treatments but had greater variance in patch-cut treatments. All treatments increased canopy openness and the volume of coarse woody debris. Occurrence of birds using early successional habitats was greater on sites treated with patch cuts and diagonal intersections. Canopy openings on row-thinned stands are being filled by lateral crown growth of retained trees whereas patch cut and diagonal intersection gaps appear likely to be filled by regenerating saplings.

[Edge effects of forest gap in Pinus massoniana plantations on the decomposition of leaf litter recalcitrant components of Cinnamomum camphora and Toona ciliata.

PubMed

Zhang, Yan; Zhang, Dan Ju; Li, Xun; Liu, Hua; Zhang, Ming Jin; Yang, Wan Qin; Zhang, Jian

2016-04-22

The objective of the study was to evaluate the dynamics of recalcitrant components during foliar litter decomposition under edge effects of forest gap in Pinus massoniana plantations in the low hilly land, Sichuan basin. A field litterbag experiment was conducted in seven forest gaps with different sizes (100, 225, 400, 625, 900, 1225, 1600 m 2 ) which were generated by thinning P. massoniana plantations. The degradation rate of four recalcitrant components, i.e., condensed tannins, total phenol, lignin and cellulose in foliar litter of two native species (Cinnamomum camphora and Toona ciliata) at the gap edge and under the closed canopy were measured. The results showed that the degradation rate of recalcitrant components in T. ciliata litter except for cellulose at the gap edge were significantly higher than that under the closed canopy. For C. camphora litter, only the degradation of lignin at the gap edge was higher than that under the closed canopy. After one-year decomposition, four recalcitrant components in two types of foliar litter exhibited an increment of degradation rate, and the degradation rate of condensed tannin was the fastest, followed by total phenol and cellulose, but the lignin degradation rate was the slowest. With the increase of gap size, except for cellulose, the degradation rate ofthe other three recalcitrant components of the T. ciliata at the edge of medium sized gaps (400 and 625 m 2 ) were significantly higher than at the edge of other gaps. However, lignin in the C. camphora litter at the 625 m 2 gap edge showed the greatest degradation rate. Both temperature and litter initial content were significantly correlated with litter recalcitrant component degradation. Our results suggested that medium sized gaps (400-625 m 2 ) had a more significant edge effect on the degradation of litter recalcitrant components in the two native species in P. massoniana plantations, however, the effect also depended on species.

Modeling bidirectional reflectance of forests and woodlands using Boolean models and geometric optics

NASA Technical Reports Server (NTRS)

Strahler, Alan H.; Jupp, David L. B.

1990-01-01

Geometric-optical discrete-element mathematical models for forest canopies have been developed using the Boolean logic and models of Serra. The geometric-optical approach is considered to be particularly well suited to describing the bidirectional reflectance of forest woodland canopies, where the concentration of leaf material within crowns and the resulting between-tree gaps make plane-parallel, radiative-transfer models inappropriate. The approach leads to invertible formulations, in which the spatial and directional variance provides the means for remote estimation of tree crown size, shape, and total cover from remotedly sensed imagery.

Herbivorous insect response to group selection cutting in a southeastern bottomland hardwood forest.

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

Michael D. Ulyshen; James L. Hanula; Scott Horn

2005-04-01

ABSTRACT Malaise and pitfall traps were used to sample herbivorous insects in canopy gaps created by group-selection cutting in a bottomland hardwood forest in South Carolina. The traps were placed at the centers, edges, and in the forest adjacent to gaps of different sizes (0.13, 0.26, and 0.50 ha) and ages (1 and 7 yr old) during four sampling periods in 2001. Overall, the abundance and species richness of insect herbivores were greater at the centers of young gaps than at the edge of young gaps or in the forest surrounding young gaps. There were no differences in abundance ormore » species richness among old gap locations (i.e., centers, edges, and forest), and we collected significantly more insects in young gaps than old gaps. The insect communities in old gaps were more similar to the forests surrounding them than young gap communities were to their respective forest locations, but the insect communities in the two forests locations (surrounding young and old gaps) had the highest percent similarity of all. Although both abundance and richness increased in the centers of young gaps with increasing gap size, these differences were not significant.Weattribute the increased numbers of herbivorous insects to the greater abundance of herbaceous plants available in young gaps.« less

Soil properties in old-growth Douglas-fir gaps in the western Cascade Mountains of Oregon

Treesearch

Robert P. Griffiths; Andrew N. Gray; Thomas A. Spies

2010-01-01

This study had three objectives: (1) to determine if there are correlations between aboveground vegetation and belowground soil properties within large 50-m-diameter gaps, (2) to determine how large gaps influence forest soils compared with nongap soils, and (3) to measure the effects of differently sized gaps on gap soils. Circular canopy gaps were created in old-...

[Effects of forest canopy gap on Abies faxoniana seedling's biomass and its allocation in sub-alpine coniferous forest of West Sichuan].

PubMed

Xian, Jun-Ren; Hu, Ting-Xing; Zhang, Yuan-Bin; Wang, Kai-Yun

2007-04-01

By the method of strip transect sampling, the density, height, basal diameter, and components biomass of Abies faxoniana seedlings (H < or = 100 cm) lived in the forest gap (FG) and under the forest canopy (FC) of subalpine natural coniferous forest in West Sichuan were investigated, and the relationships among different components biomass were analyzed. The results indicated that the density and average height (H) of A. faxoniana seedlings were significantly different in FG and under FC, with the values being 12 903 and 2 017 per hectare, and 26.6 cm and 24.3 cm, respectively, while no significant differences were found in average basal diameter (D) and biomass. The biomass allocation in seedling's components was markedly affected by forest gap. In FG, the biomass ratio of branch to trunk (BRBT) reached the maximum (1.54) at 12th year, and then, declined and fluctuated at 0. 69. Under FC, the BRBT was increased with seedlings growth, and exceeded 1.0 at about 15th year. The total biomass and the biomass of leaf, stem, shoot and root grown in FG and under FC were significantly linearly correlated with D2H. There were significant positive correlations among the biomass of different seedling's components.

Canopy gaps decrease microbial densities and disease risk for a shade-intolerant tree species

Treesearch

Kurt O. Reinhart; Alejandro A. Royo; Stacie A. Kageyama; Keith. Clay

2010-01-01

Canopy disturbances such as windthrowevents have obvious impacts on forest structure and composition aboveground, but changes in soil microbial communities and the consequences of these changes are less understood.We characterized the densities of a soil-borne pathogenic oomycete (Pythium) and a common saprotrophic zygomycete (Mortierella...

Case study: Rainfall partitioning across a natural-to-urban forest gradient during an extreme rain event

NASA Astrophysics Data System (ADS)

Akin, B. H.; Van Stan, J. T., II; Cote, J. F.; Jarvis, M. T.; Underwood, J.; Friesen, J.; Hildebrandt, A.; Maldonado, G.

2017-12-01

Trees' partitioning of rainfall is an important first process along the rainfall-to-runoff pathway that has economically significant influences on urban stormwater management. However, important knowledge gaps exist regarding (1) its role during extreme storms and (2) how this role changes as forest structure is altered by urbanization. Little research has been conducted on canopy rainfall partitioning during large, intense storms, likely because canopy water storage is rapidly overwhelmed (i.e., 1-3 mm) by short duration events exceeding, for example, 80 mm of rainfall. However, canopy structure controls more than just storage; it also affects the time for rain to drain to the surface (becoming throughfall) and the micrometeorological conditions that drive wet canopy evaporation. In fact, observations from an example extreme ( 100 mm with maximum 5-minute intensities exceeding 55 mm/h) storm across a urban-to-natural gradient in pine forests in southeast Georgia (USA), show that storm intensities were differentially dampened by 33% (tree row), 28% (forest fragment), and 17% (natural forests). In addition, maximum wet canopy evaporation rates were higher for the exposed tree row (0.18 mm/h) than for the partially-enclosed fragment canopy (0.14 mm/h) and the closed canopy natural forest site (0.11). This resulted in interception percentages decreasing from urban-to-natural stand structures (25% to 16%). A synoptic analysis of the extreme storm in this case study also shows that the mesoscale meteorological conditions that developed the heavy rainfall is expected to occur more often with projected climate changes.

Assessing the performance of aerial image point cloud and spectral metrics in predicting boreal forest canopy cover

NASA Astrophysics Data System (ADS)

Melin, M.; Korhonen, L.; Kukkonen, M.; Packalen, P.

2017-07-01

Canopy cover (CC) is a variable used to describe the status of forests and forested habitats, but also the variable used primarily to define what counts as a forest. The estimation of CC has relied heavily on remote sensing with past studies focusing on satellite imagery as well as Airborne Laser Scanning (ALS) using light detection and ranging (lidar). Of these, ALS has been proven highly accurate, because the fraction of pulses penetrating the canopy represents a direct measurement of canopy gap percentage. However, the methods of photogrammetry can be applied to produce point clouds fairly similar to airborne lidar data from aerial images. Currently there is little information about how well such point clouds measure canopy density and gaps. The aim of this study was to assess the suitability of aerial image point clouds for CC estimation and compare the results with those obtained using spectral data from aerial images and Landsat 5. First, we modeled CC for n = 1149 lidar plots using field-measured CCs and lidar data. Next, this data was split into five subsets in north-south direction (y-coordinate). Finally, four CC models (AerialSpectral, AerialPointcloud, AerialCombi (spectral + pointcloud) and Landsat) were created and they were used to predict new CC values to the lidar plots, subset by subset, using five-fold cross validation. The Landsat and AerialSpectral models performed with RMSEs of 13.8% and 12.4%, respectively. AerialPointcloud model reached an RMSE of 10.3%, which was further improved by the inclusion of spectral data; RMSE of the AerialCombi model was 9.3%. We noticed that the aerial image point clouds managed to describe only the outermost layer of the canopy and missed the details in lower canopy, which was resulted in weak characterization of the total CC variation, especially in the tails of the data.

Airborne laser-guided imaging spectroscopy to map forest trait diversity and guide conservation.

PubMed

Asner, G P; Martin, R E; Knapp, D E; Tupayachi, R; Anderson, C B; Sinca, F; Vaughn, N R; Llactayo, W

2017-01-27

Functional biogeography may bridge a gap between field-based biodiversity information and satellite-based Earth system studies, thereby supporting conservation plans to protect more species and their contributions to ecosystem functioning. We used airborne laser-guided imaging spectroscopy with environmental modeling to derive large-scale, multivariate forest canopy functional trait maps of the Peruvian Andes-to-Amazon biodiversity hotspot. Seven mapped canopy traits revealed functional variation in a geospatial pattern explained by geology, topography, hydrology, and climate. Clustering of canopy traits yielded a map of forest beta functional diversity for land-use analysis. Up to 53% of each mapped, functionally distinct forest presents an opportunity for new conservation action. Mapping functional diversity advances our understanding of the biosphere to conserve more biodiversity in the face of land use and climate change. Copyright © 2017, American Association for the Advancement of Science.

Demonstrating the Uneven Importance of Fine-Scale Forest Structure on Snow Distributions using High Resolution Modeling

NASA Astrophysics Data System (ADS)

Broxton, P. D.; Harpold, A. A.; van Leeuwen, W.; Biederman, J. A.

2016-12-01

Quantifying the amount of snow in forested mountainous environments, as well as how it may change due to warming and forest disturbance, is critical given its importance for water supply and ecosystem health. Forest canopies affect snow accumulation and ablation in ways that are difficult to observe and model. Furthermore, fine-scale forest structure can accentuate or diminish the effects of forest-snow interactions. Despite decades of research demonstrating the importance of fine-scale forest structure (e.g. canopy edges and gaps) on snow, we still lack a comprehensive understanding of where and when forest structure has the largest impact on snowpack mass and energy budgets. Here, we use a hyper-resolution (1 meter spatial resolution) mass and energy balance snow model called the Snow Physics and Laser Mapping (SnowPALM) model along with LIDAR-derived forest structure to determine where spatial variability of fine-scale forest structure has the largest influence on large scale mass and energy budgets. SnowPALM was set up and calibrated at sites representing diverse climates in New Mexico, Arizona, and California. Then, we compared simulations at different model resolutions (i.e. 1, 10, and 100 m) to elucidate the effects of including versus not including information about fine scale canopy structure. These experiments were repeated for different prescribed topographies (i.e. flat, 30% slope north, and south-facing) at each site. Higher resolution simulations had more snow at lower canopy cover, with the opposite being true at high canopy cover. Furthermore, there is considerable scatter, indicating that different canopy arrangements can lead to different amounts of snow, even when the overall canopy coverage is the same. This modeling is contributing to the development of a high resolution machine learning algorithm called the Snow Water Artificial Network (SWANN) model to generate predictions of snow distributions over much larger domains, which has implications for improving land surface models that do not currently resolve or parameterize fine-scale canopy structure. In addition, these findings have implications for understanding the potential of different forest management strategies (i.e. thinning) based on local topography and climate to maximize the amount and retention of snow.

Simulated transient thermal infrared emissions of forest canopies during rainfall events

NASA Astrophysics Data System (ADS)

Ballard, Jerrell R.; Hawkins, William R.; Howington, Stacy E.; Kala, Raju V.

2017-05-01

We describe the development of a centimeter-scale resolution simulation framework for a theoretical tree canopy that includes rainfall deposition, evaporation, and thermal infrared emittance. Rainfall is simulated as discrete raindrops with specified rate. The individual droplets will either fall through the canopy and intersect the ground; adhere to a leaf; bounce or shatter on impact with a leaf resulting in smaller droplets that are propagated through the canopy. Surface physical temperatures are individually determined by surface water evaporation, spatially varying within canopy wind velocities, solar radiation, and water vapor pressure. Results are validated by theoretical canopy gap and gross rainfall interception models.

Release of suppressed red spruce using canopy gap creation—Ecological restoration in the Central Appalachians

USGS Publications Warehouse

Rentch, J.S.; Ford, W. Mark; Schuler, T.S.; Palmer, J.; Diggins, Corinne A.

2016-01-01

Red spruce (Picea rubens) and red spruce-northern hardwood mixed stands once covered as much as 300,000 ha in the Central Appalachians, but now comprise no more than 21,000 ha. Recently, interest in restoration of this forest type has increased because red spruce forests provide habitat for a number of rare animal species. Our study reports the results of an understory red spruce release experiment in hardwood-dominated stands that have a small component of understory red spruce. In 2005, 188 target spruce were identified in sample plots at six locations in central West Virginia. We projected a vertical cylinder above the crown of all target spruces, and in 2007, we performed a release treatment whereby overtopping hardwoods were treated with herbicide using a stem injection technique. Release treatments removed 0–10% (Control), 11–50% (Low), 51–89% (Medium), and ≤90% (High) of the basal area of overtopping trees. We also took canopy photographs at the time of each remeasurement in 2007, 2010, and 2013, and compared basal removal treatments and resulting 2010 canopy openness and understory light values. The high treatment level provided significantly greater six-year dbh and height growth than the other treatment levels. Based on these results, we propose that a tree-centered release approach utilizing small canopy gaps that emulate the historical, gap-phase disturbance regime provides a good strategy for red spruce restoration in hardwood forests where overstory spruce are virtually absent, and where red spruce is largely relegated to the understory.

Vegetative composition in forested areas following application of desired forest condition treatments

Treesearch

Trent A. Danley; Andrew W. Ezell; Emily B. Schultz; John D. Hodges

2015-01-01

Desired forest conditions, or DFCs, are recently created parameters which strive to create diverse stands of hardwoods of various species and age classes, along with varying densities and canopy gaps, through the use of uneven-aged silvicultural methods and repeated stand entries. Little research has been conducted to examine residual stand composition and hardwood...

Quantifying forest mortality with the remote sensing of snow

NASA Astrophysics Data System (ADS)

Baker, Emily Hewitt

Greenhouse gas emissions have altered global climate significantly, increasing the frequency of drought, fire, and pest-related mortality in forests across the western United States, with increasing area affected each year. Associated changes in forests are of great concern for the public, land managers, and the broader scientific community. These increased stresses have resulted in a widespread, spatially heterogeneous decline of forest canopies, which in turn exerts strong controls on the accumulation and melt of the snowpack, and changes forest-atmosphere exchanges of carbon, water, and energy. Most satellite-based retrievals of summer-season forest data are insufficient to quantify canopy, as opposed to the combination of canopy and undergrowth, since the signals of the two types of vegetation greenness have proven persistently difficult to distinguish. To overcome this issue, this research develops a method to quantify forest canopy cover using winter-season fractional snow covered area (FSCA) data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) snow covered area and grain size (MODSCAG) algorithm. In areas where the ground surface and undergrowth are completely snow-covered, a pixel comprises only forest canopy and snow. Following a snowfall event, FSCA initially rises, as snow is intercepted in the canopy, and then falls, as snow unloads. A select set of local minima in a winter F SCA timeseries form a threshold where canopy is snow-free, but forest understory is snow-covered. This serves as a spatially-explicit measurement of forest canopy, and viewable gap fraction (VGF) on a yearly basis. Using this method, we determine that MODIS-observed VGF is significantly correlated with an independent product of yearly crown mortality derived from spectral analysis of Landsat imagery at 25 high-mortality sites in northern Colorado. (r =0.96 +/-0.03, p =0.03). Additionally, we determine the lag timing between green-stage tree mortality and needlefall, showing that needlefall occurred an average of 2.6 +/- 1.2 years after green-stage mortality. We relate observed increases in the VGF with crown mortality, showing that a 1% increase in mortality area produces a 0.33 +/- 0.1 % increase in the VGF.

Exploring canopy structure and function as a potential mechanism of sustain carbon sequestration in aging forests

NASA Astrophysics Data System (ADS)

Fotis, A. T.; Curtis, P.; Ricart, R.

2013-12-01

The notion that old-growth forests reach carbon neutrality has recently been challenged, but the mechanisms responsible for continued productivity have remained elusive. Increases in canopy structural complexity, defined by high horizontal and vertical variability in leaf distribution (rugosity), has been proposed as a mechanism for sustained high rates of above ground net primary production (ANPPw) in forests up to ~170 years by enhancing light use efficiency (LUE) and nitrogen use efficiency (NUE). However, a detailed understanding of how rugosity affects resource distribution within and among trees leading to greater LUE and NUE is not known. We propose that leaves in high rugosity plots receive greater photosynthetic photon flux density (PPFD) than leaves in low rugosity plots, causing shifts from shade- to sun- adapted leaves into deeper portions of the canopy, which is thought to increase the photosynthetic capacity of individuals and lead to higher carbon assimilation in forests. The goal of this research was to: 1) quantify different canopy structural characteristics using a portable canopy LiDAR (PCL) and; 2) assess how these structural characteristics affect resource distribution and subsequent changes in leaf morphological, physiological and biochemical traits in three broadleaf species (e.g., Acer rubrum, Quercus rubra and Fagus grandifolia) and one conifer species (e.g., Pinus strobus) at different levels in the canopy in plots with similar leaf are index (LAI) but highly contrasting rugosity levels. We found that gap fraction had a strong positive correlation with rugosity. High rugosity plots had a bimodal distribution of LAI that was concentrated at the top and bottom of the canopy with an open midstory (between 10-50% of total canopy height) whereas low rugosity plots had a more even distribution of leaves. Leaf mass per area (LMA) of all broadleaved species had a strong positive correlation with cumulative gap fraction (P. strobus had a relatively weaker, but strong positive correlation). On average, Q. rubra and F. grandifolia had greater LMA in high rugosity plots while LMA was greater for A. rubrum and P. strobus in low rugosity plots. These findings suggest that species are responding differently to canopy structural complexity and that leaf arrangement in space plays an important role in determining leaf level traits. Furthermore, this research demonstrates that PCL can be used for quick identification of canopy traits (e.g., average LMA) relevant to photosynthetic capacity, and thus, carbon sequestration potential, and therefore may become an important tool in forest management.

GAP SIZE AND SUCCESSIONAL PROCESSES IN SOUTHERN APPALACHIAN FORESTS

EPA Science Inventory

We used clearcut logging in establishing four replicated sizes of canopy openings (0.016, 0.08, 0.4, and 2.0 ha) in a southern Appalachian hardwood forest in 1981 to examine the long-term effects of disturbance size on plant community structure, biomass accumulation, aboveground ...

Canopy gap characteristics of an old-growth and an adjacent second-growth beech-maple stand in north-central Ohio

Treesearch

David M. Hix; P. Charles Goebel; Heather L. Whitman

2011-01-01

The increased importance of integrating concepts of natural disturbance regimes into forest management, as well as the need to manage for complex forest structures, requires an understanding of how forest stands develop following natural disturbances. One of the primary natural disturbance types occurring in beech-maple ecosystems of the Central Hardwood Forest is...

Estimation of canopy attributes in beech forests using true colour digital images from a small fixed-wing UAV

NASA Astrophysics Data System (ADS)

Chianucci, Francesco; Disperati, Leonardo; Guzzi, Donatella; Bianchini, Daniele; Nardino, Vanni; Lastri, Cinzia; Rindinella, Andrea; Corona, Piermaria

2016-05-01

Accurate estimates of forest canopy are essential for the characterization of forest ecosystems. Remotely-sensed techniques provide a unique way to obtain estimates over spatially extensive areas, but their application is limited by the spectral and temporal resolution available from these systems, which is often not suited to meet regional or local objectives. The use of unmanned aerial vehicles (UAV) as remote sensing platforms has recently gained increasing attention, but their applications in forestry are still at an experimental stage. In this study we described a methodology to obtain rapid and reliable estimates of forest canopy from a small UAV equipped with a commercial RGB camera. The red, green and blue digital numbers were converted to the green leaf algorithm (GLA) and to the CIE L*a*b* colour space to obtain estimates of canopy cover, foliage clumping and leaf area index (L) from aerial images. Canopy attributes were compared with in situ estimates obtained from two digital canopy photographic techniques (cover and fisheye photography). The method was tested in beech forests. UAV images accurately quantified canopy cover even in very dense stand conditions, despite a tendency to not detecting small within-crown gaps in aerial images, leading to a measurement of a quantity much closer to crown cover estimated from in situ cover photography. Estimates of L from UAV images significantly agreed with that obtained from fisheye images, but the accuracy of UAV estimates is influenced by the appropriate assumption of leaf angle distribution. We concluded that true colour UAV images can be effectively used to obtain rapid, cheap and meaningful estimates of forest canopy attributes at medium-large scales. UAV can combine the advantage of high resolution imagery with quick turnaround series, being therefore suitable for routine forest stand monitoring and real-time applications.

[Effects of forest gap size and light intensity on herbaceous plants in Pinus koraiensis-dominated broadleaved mixed forest].

PubMed

Duan, Wen-Biao; Wang, Li-Xia; Chen, Li-Xin; Du, Shan; Wei, Quan-Shuai; Zhao, Jian-Hui

2013-03-01

1 m x 1 m fixed quadrats were parallelly arranged with a space of 2 m in each of six forest gaps in Pinus koraiensis-dominated broadleaved mixed forest, taking the gap center as the starting point and along east-west and south-north directions. In each quadrat, the coverage and abundance of herbaceous plants at different height levels were investigated by estimation method in June and September 2011, and the matrix characteristics within the quadrats were recorded. Canopy analyzer was used to take fish-eye photos in the selected overcast days in each month from June to September, 2011, and the relative light intensity was calculated by using Gap Light Analyzer 2.0 software. The differences in the relative light intensity and herbaceous plants coverage and richness between different gaps as well as the correlations between the coverage of each species and the direct light, diffuse light, and matrix were analyzed. The results showed that in opening areas and under canopy, the relative light intensity in large gaps was higher than that in small gaps, and the variation ranges of diffuse light and direct light from gap center to gap edge were bigger in large gaps than in small gaps. The direct light reaching at the ground both in large gaps and in small gaps was higher in the north than in the south direction. In the Z1, Z2, Z3, and Z4 zones, both the coverage and the richness of herbaceous plants were larger in large gaps than in small gaps, and the differences of species richness between large and small gaps reached significant level. The coverage of the majority of the herbaceous plants had significant correlations with diffuse light and matrix, and only the coverage of a few herbaceous plants was correlated with direct light.

Canopy gap dynamics of second-growth red spruce-northern hardwood stands in West Virginia

USGS Publications Warehouse

Rentch, J.S.; Schuler, T.M.; Nowacki, G.J.; Beane, N.R.; Ford, W.M.

2010-01-01

Forest restoration requires an understanding of the natural disturbance regime of the target community and estimates of the historic range of variability of ecosystem components (composition, structure, and disturbance processes). Management prescriptions that support specific restoration activities should be consistent with these parameters. In this study, we describe gap-phase dynamics of even-aged, second-growth red spruce-northern hardwood stands in West Virginia that have been significantly degraded following early Twentieth Century harvesting and wildfire. In the current stage of stand development, gaps tended to be small, with mean canopy gap and extended canopy gap sizes of 53.4m2 and 199.3m2, respectively, and a canopy turnover rate of 1.4%year-1. The majority of gaps resulted from the death of one or two trees. American beech snags were the most frequent gap maker, partially due to the elevated presence of beech-bark disease in the study area. Gaps ranged in age from 1 to 28 years, had a mean of 13 years, and were unimodal in distribution. We projected red spruce to be the eventual gap filler in approximately 40% of the gaps. However, we estimated that most average-sized gaps will close within 15-20 years before red spruce canopy ascension is projected (30-60 years). Accordingly, many understory red spruce will require more than one overhead release - an observation verified by the tree-ring record and consistent with red spruce life history characteristics. Based on our observations, silvicultural prescriptions that include overhead release treatments such as thinning from above or small gap creation through selection harvesting could be an appropriate activity to foster red spruce restoration in the central Appalachians. ?? 2010 Elsevier B.V.

Multiresolution quantification of deciduousness in West-Central African forests

NASA Astrophysics Data System (ADS)

Viennois, G.; Barbier, N.; Fabre, I.; Couteron, P.

2013-11-01

The characterization of leaf phenology in tropical forests is of major importance for forest typology as well as to improve our understanding of earth-atmosphere-climate interactions or biogeochemical cycles. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West-Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data were averaged over the wet and dry seasons to provide a data set of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high (SPOT-5) spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry-season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in West-Central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and carbon-cycle applications.

Repeated prescribed fires alter gap-phase regeneration in mixed-oak forests

Treesearch

Todd F. Hutchinson; Robert P. Long; Joanne Rebbeck; Elaine Kennedy Sutherland; Daniel A. Yaussy

2012-01-01

Oak dominance is declining in the central hardwoods region, as canopy oaks are being replaced by shade-tolerant trees that are abundant in the understory of mature stands. Although prescribed fire can reduce understory density, oak seedlings often fail to show increased vigor after fire, as the canopy remains intact. In this study, we examine the response of tree...

Tree Death Leading To Ecosystem Renewal? Forecasting Carbon Storage As Eastern Forests Age

NASA Astrophysics Data System (ADS)

Curtis, P.; Gough, C. M.; Bohrer, G.; Nadelhoffer, K. J.; Ivanov, V. Y.

2013-12-01

The future trajectory of North American carbon (C) stocks remains uncertain as a subset of maturing trees die in mixed deciduous forests of the U.S. Midwest and East transitioning from early to middle and late succession. We are studying disturbance-structure-function relationships of aging forests in northern Michigan using long-term ecological and meteorological C cycling studies, a large-scale disturbance experiment, a 200-year forest chronosequence, and flux comparisons across three tower sites. We find that ecosystem responses to mortality are characterized by several processes that affect structure-function relationships and alter the way ecosystem functioning interacts with meteorological forcing. We subjected 39 ha of forest to moderate experimental disturbance, similar to that of age-related or climatically induced tree mortality. We found that the mortality of a third of all canopy trees minimally altered the balance between forest C uptake and release, as growth-limiting light and nitrogen resources were rapidly reallocated from dead and dying trees to undisturbed trees. Although disturbance-induced mortality increased soil N mineralization rates, nitrification, and denitrification, N exports from soils remained low. Upper canopy gap formation and a rise in structural complexity allowed increased photosynthetic contribution of sub-canopy vegetation to compensate for the death of canopy dominant trees. However, we found large differences between the transpirational response of maples and oaks to VPD and soil moisture, which led to relative declines in maple transpiration post-disturbance. These hydrologic differences may affect a species' ability to compete for resources following such a disturbance. Changes to canopy structure had a relatively small effect on roughness length and the turbulence forcing of fluxes from the canopy. We currently are studying how tree mortality driven changes in canopy structure affects within-canopy resource distribution and subsequent changes in leaf morphological, physiological and biochemical traits, how disturbance severity relates to the magnitude of C storage resilience, the impacts of clouds and aerosols on surface diffuse light and how they interact with canopy structure to modify C uptake, and how these processes change overall C assimilation given different forest age and disturbance histories. Along a conceptual continuum from structural to functional attributes, our results show that leaf area distribution and its heterogeneity, canopy light, water and nutrient use efficiency, canopy roughness length and turbulent mixing of canopy air, and the coupling between soil moisture and canopy density, all change with successional and disturbance processes and affect ecosystem C fluxes. Patchy mortality and related increases in structural complexity could, against expectations, enhance the C storage of some forests. Our finding that increases in canopy structural complexity improve resource-use efficiency provides a mechanism for maintaining high rates of C storage in aging forests.

Bat activity in harvested and intact forest stands in the allegheny mountains

USGS Publications Warehouse

Owen, S.F.; Menzel, M.A.; Edwards, J.W.; Ford, W.M.; Menzel, J.M.; Chapman, B.R.; Wood, P.B.; Miller, K.V.

2004-01-01

We used Anabat acoustical monitoring devices to examine bat activity in intact canopy forests, complex canopy forests with gaps, forests subjected to diameter-limit harvests, recent deferment harvests, clearcuts and unmanaged forested riparian areas in the Allegheny Mountains of West Virginia in the summer of 1999. We detected eight species of bats, including the endangered Indiana bat (Myotis sodalis). Most bat activity was concentrated in forested riparian areas. Among upland habitats, activity of silver-haired bats (Lasionycteris noctivagans) and hoary bats (Lasiurus cinereus) was higher in open, less cluttered vegetative types such as recent deferment harvests and clearcuts. Our results suggest that bat species in the central Appalachians partially segregate themselves among vegetative conditions based on differences in body morphology and echolocation call characteristics. From the standpoint of conserving bat foraging habitat for the maximum number of species in the central Appalachians, special emphasis should be placed on protecting forested riparian areas.

Canopy structural alterations to nitrogen functions of the soil microbial community in a Quercus virginiana forest

NASA Astrophysics Data System (ADS)

Moore, L. D.; Van Stan, J. T., II; Rosier, C. L.; Gay, T. E.; Wu, T.

2014-12-01

Forest canopy structure controls the timing, amount and chemical character of precipitation supply to soils through interception and drainage along crown surfaces. Yet, few studies have examined forest canopy structural connections to soil microbial communities (SMCs), and none have measured how this affects SMC N functions. The maritime Quercus virginiana Mill. (southern live oak) forests of St Catherine's Island, GA, USA provide an ideal opportunity to examine canopy structural alterations to SMCs and their functioning, as their throughfall varies substantially across space due to dense Tillandsia usneoides L. (spanish moss) mats bestrewn throughout. To examine the impact of throughfall variability on SMC N functions, we examined points along the canopy coverage continuum: large canopy gaps (0%), bare canopy (50-60%), and canopy of heavy T. usneoides coverage (>=85%). Five sites beneath each of the canopy cover types were monitored for throughfall water/ions and soil leachates chemistry for one storm each month over the growing period (7 months, Mar-2014 to Sep-2014) to compare with soil chemistry and SMC communities sampled every two months throughout that same period (Mar, May, Jul, Sep). DGGE and QPCR analysis of the N functioning genes (NFGs) to characterize the ammonia oxidizing bacterial (AOB-amoA), archaea (AOA-amoA), and ammonification (chiA) communities were used to determine the nitrification and decomposition potential of these microbial communities. PRS™-probes (Western Ag Innovations Inc., Saskatoon, Canada) were then used to determine the availability of NO3-N and NH4+N in the soils over a 6-week period to evaluate whether the differing NFG abundance and community structures resulted in altered N cycling.

Multiresolution quantification of deciduousness in West Central African forests

NASA Astrophysics Data System (ADS)

Viennois, G.; Barbier, N.; Fabre, I.; Couteron, P.

2013-04-01

The characterization of leaf phenology in tropical forests is of major importance and improves our understanding of earth-atmosphere-climate interactions. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data were averaged over the wet and dry seasons to provide a dataset of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye) and high (SPOT-5) spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in west central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and carbon-cycle applications.

Estimation of leaf area index and foliage clumping in deciduous forests using digital photography

NASA Astrophysics Data System (ADS)

Chianucci, Francesco; Cutini, Andrea

2013-04-01

Rapid, reliable and meaningful estimates of leaf area index (LAI) are essential to the characterization of forest ecosystems. In this contribution the accuracy of both fisheye and non-fisheye digital photography for the estimation of forest leaf area in deciduous stands was evaluated. We compared digital hemispherical photography (DHP), the most widely used technique that measures the gap fraction at multiple zenith angles, with methods that measure the gap fraction at a single zenith angle, namely 57.5 degree photography and cover photography (DCP). Comparison with other different gap fraction methods used to calculate LAI such as canopy transmittance measurements from AccuPAR ceptometer and LAI- 2000 Plant Canopy Analyzer (PCA) were also performed. LAI estimated from all these indirect methods were compared with direct measurements obtained by litter traps (LAILT). We applied these methods in 10 deciduous stands of Quercus cerris, Castanea sativa and Fagus sylvatica, the most common deciduous species in Italy, where LAILT ranged from 3.9 to 7.3. DHP and DCP provided good indirect estimates of LAILT, and outperformed the other indirect methods. The DCP method provided estimates of crown porosity, crown cover, foliage cover and the clumping index at the zenith, but required assumptions about the light extinction coefficient at the zenith (k), to accurately estimate LAI. Cover photography provided good indirect estimates of LAI assuming a spherical leaf angle distribution, even though k appeared to decrease as LAI increased, thus affecting the accuracy of LAI estimates in DCP. In contrast, the accuracy of LAI estimates in DHP appeared insensitive to LAILT values, but the method was sensitive to photographic exposure, gamma-correction and was more time-consuming than DCP. Foliage clumping was estimated from all the photographic methods by analyzing either gap size distribution (DCP) or gap fraction distribution (DHP). Foliage clumping was also calculated from PCA and compared with DHP. The studied stands were characterized by fairly homogeneous canopies with higher within-crown clumping than between-crowns clumping; only the segmented analysis of gap fraction for each ring of the fisheye images was found to provide useful clumping index in such homogeneous canopies. By contrast, the 1-azimuth segment method employed in PCA poorly detected clumping in dense canopies. We conclude both fisheye and non-fisheye photographic methods are suitable for dense deciduous forests. Cover photography holds great promise as a means to quickly obtain inexpensive estimates of LAI over large areas. However, in situations where no direct reference measurements of k are available, we recommend using both DHP and DCP, in order to cross-calibrate the two methods; DCP could then be used for more routinely indirect measurement and monitoring of LAI. Keywords: digital hemispherical photography, cover photography, litter trap, AccuPAR ceptometer, LAI-2000.

Experimental canopy removal enhances diversity of vernal pond amphibians.

PubMed

Skelly, David K; Bolden, Susan R; Freidenburg, L Kealoha

2014-03-01

Vernal ponds are often treated as protected environments receiving special regulation and management. Within the landscapes where they are found, forest vegetation frequently dominates surrounding uplands and can grow to overtop and shade pond basins. Two bodies of research offer differing views of the role of forest canopy for vernal pond systems. Studies of landscape conversion suggest that removing forest overstory within uplands can cause local extinctions of amphibians by altering terrestrial habitat or hindering movement. Studies of canopy above pond basins imply an opposite relationship; encroachment of overstory vegetation can be associated with local extinctions potentially via changes in light, thermal, and food resource environments. Unresolved uncertainties about the role of forest canopy reveal significant gaps in our understanding of wetland species distributions and dynamics. Any misunderstanding of canopy influences is simultaneously important to managers because current practices emphasize promoting or conserving vegetation growth particularly within buffers immediately adjacent to ponds. We evaluated this apparent contradiction by conducting a landscape-scale, long-term experiment using 14 natural vernal ponds. Tree felling at six manipulated ponds was limited in spatial scope but was nevertheless effective in increasing water temperature. Compared with eight control ponds, manipulated ponds maintained more amphibian species during five years post-manipulation. There was little evidence that any species was negatively influenced, and the reproductive effort of species for which we estimated egg inputs maintained pretreatment population densities in manipulated compared with control ponds. Overall, our experiment shows that a carefully circumscribed reduction of overhead forest canopy can enhance the capacity of vernal ponds to support wildlife diversity and suggests a scale dependence of canopy influences on amphibians. These findings have implications for the connection between current wetland management practices and the goals of wetland stewardship and conservation of wetland-dependent species.

Carbon stocks and accumulation rates in Pacific Northwest forests: role of stand age, plant community, and productivity

Treesearch

Andrew N. Gray; Thomas R. Whittier; Mark E. Harmon

2016-01-01

Forest ecosystems are removing significant amounts of carbon from the atmosphere. Both abiotic resource availability and biotic interactions during forest succession affect C accumulation rates and maximum C stocks. However, the timing and controls on the peak and decline in C accumulation rates as stands age, trees increase in size, and canopy gaps become prevalent...

Remote sensing of selective logging in Amazonia Assessing limitations based on detailed field observations, Landsat ETM+, and textural analysis.

Treesearch

Gregory P. Asner; Michael Keller; Rodrigo Pereira; Johan C. Zweede

2002-01-01

We combined a detailed field study of forest canopy damage with calibrated Landsat 7 Enhanced Thematic Mapper Plus (ETM+) reflectance data and texture analysis to assess the sensitivity of basic broadband optical remote sensing to selective logging in Amazonia. Our field study encompassed measurements of ground damage and canopy gap fractions along a chronosequence of...

Does the precipitation redistribution of the canopy sense in the moisture pattern of the forest litter?

NASA Astrophysics Data System (ADS)

Zagyvai-Kiss, Katalin Anita; Kalicz, Péter; Csáfordi, Péter; Kucsara, Mihály; Gribovszki, Zoltán

2013-04-01

Precipitation is trapped and temporarily stored by the surfaces of forest crown (canopy interception) and forest litter (litter interception). The stemflow and throughfall reach the litter, thus theoretically the litter moisture content depends on these parts of precipitation. Nowadays the moisture pattern of the forest floor, both spatial and temporal scale, have growing respect for the forestry. The transition to the continuous cover forestry induce much higher variability compared to the even aged, more-less homogeneous, monocultural stands. The gap cutting is one of the key methods in the Hungarian forestry. There is an active discussion among the forest professionals how to determine the optimal gap size to maintain the optimal conditions for the seedlings. Among the open questions is how to modify surrounding trees the moisture pattern of the forest floor in the gap? In the early steps of a multidisciplinary project we processed some available data, to estimate the spatial dependency between the water content of forest litter and the spatial pattern of the canopy represented by the tree trunk. The maximum water content depends on dry weight of litter, thus we also analysed that parameter. Data were measured in three different forest ecosystems: a middle age beech (Fagus sylvatica), a sessile oak (Quercus petraea) and a spruce (Picea abies) stand. The study site (Hidegvíz Valley Research Cathcment) is located in Sopron Hills at the eastern border of the Alps. Litter samples were collected under each stand (occasionally 10-10 pieces from 40?40 cm area) and locations of the samples and neighbouring trees were mapped. We determined dry weight and the water content of litter in laboratory. The relationship between water content and the distance of tree trunks in case of spruce and oak stands were not significant and in case of the beech stand was weakly significant. Climate change effects can influence significantly forest floor moisture content, therefore this factor has also taken into account. Acknowledgement: The research was financially supported by the TÁMOP-4.2.2.A-11/1/KONV-2012-0004 and TÁMOP-4.2.2.A-11/1/KONV-2012-0013 joint EU-national research projects.

Community Composition in Canopy Gaps as Influenced by Presence or Absence of Rhododendron maximum

Treesearch

Christopher T. Rivers; David H. van Lear; Barton D. Clinton; Thomas A. Waldrop

1999-01-01

The process of gap formation and recolonization plays an important role in the structure and composition in southern Appalachian forests. The understory composition existing before a disturbance will shape successional patterns of the future stand. Rhododendron maximum is native to the southern Appalachians and exists as a major understory...

Canopy gaps decrease microbial densities and disease risk for a shade-intolerant tree species

NASA Astrophysics Data System (ADS)

Reinhart, Kurt O.; Royo, Alejandro A.; Kageyama, Stacie A.; Clay, Keith

2010-11-01

Canopy disturbances such as windthrow events have obvious impacts on forest structure and composition aboveground, but changes in soil microbial communities and the consequences of these changes are less understood. We characterized the densities of a soil-borne pathogenic oomycete ( Pythium) and a common saprotrophic zygomycete ( Mortierella) in nine pairs of forest gaps created by windthrows and adjacent forest understories. We determined the levels of Pythium necessary to cause disease by performing pathogenicity experiments using two Pythium species, a range of Pythium densities, and two common tree species ( Acer rubrum and Prunus serotina) from the study sites. Three years post-disturbance, densities of Mortierella remained suppressed in soil from forest gaps compared to levels in intact forest understories while varying across sites and sampling dates. Pythium were infrequently detected likely because of soil handling effects. Expression of disease symptoms increased with increasing inoculum density for seedlings of P. serotina with each Pythium spp. having a similar effect on this species. Conversely, A. rubrum appeared resistant to the two species of Pythium. These results suggest that Pythium densities at sites where they were detected are sufficient to cause disease and possibly affect establishment of susceptible species like P. serotina. Because early seral environments have lower loads of the saprotrophic Mortierella, pathogen loads may follow a similar pattern, causing susceptible species to establish more frequently in those habitats than in late-seral forests. Forest disturbances that alter the disease landscape may provide an additional mechanism for explaining succession of temperate forests in addition to the shade-tolerance paradigm.

Using Remote Sensing Technologies to Quantify the Effects of Beech Bark Disease on the Structure, Composition, and Function of a Late-Successional Forest

NASA Astrophysics Data System (ADS)

Stuart-Haëntjens, E. J.; Ricart, R. D.; Fahey, R. T.; Fotis, A. T.; Gough, C. M.

2016-12-01

Ecological theory maintains that as forests age, the rate at which carbon (C) is stored declines because C released through organic matter decomposition offsets declining C sequestration in new vegetative growth. Recent observational studies are challenging this long-held hypothesis, with limited evidence suggesting higher-than-expected rates in late-successional forests could be, counterintuitively, tied to canopy structural changes associated with low intensity tree mortality. As forests age, canopy structural complexity may increase when old trees die and form upper canopy gaps that release subcanopy vegetation. This provides one explanation for observations of sustained high production in old forests. Recent studies have found that this increased structural complexity and resource-use efficiency maintain C storage in mid-successional deciduous forests; whether a similar mechanism extends to late-successional forests is unknown. We will present how a slow, moderate disturbance affects the structure and C sequestration of late-successional forests. Our study site is a forest recently infected by Beech Bark Disease (BBD), which will result in the eventual mortality of American beech trees in this late successional forest in Northern Michigan, at the University of Michigan Biological Station. American Beech, Hemlock, Sugar Maple, and White Pine dominate the landscape, with American Beech making up 30% of the canopy trees on average. At the plot scale American Beech is distributed heterogeneously, comprising 1% to 60% of total plot basal area, making it possible to examine the interplay between disturbance severity, canopy structural change, and primary production resilience in this forest. Within each of the 13 plots, species and stem diameter were collected in 1992, 1994, 2014, and 2016, with future remeasurements planned. We will discuss how ground-based lidar coupled with airborne spectral (IR and RGB) imagery are being used to track canopy BBD-related structural changes over time and space, and to link structural changes with late-successional primary production. Our hypothesis is that, up to a presently unknown disturbance threshold, moderate disturbance from BBD sustains primary production in this late successional forest by partially, but not fully, rewinding ecological succession.

Mapping Topoclimate and Microclimate in the Monarch Butterfly Biosphere Reserve, Mexico

NASA Astrophysics Data System (ADS)

Weiss, S. B.

2006-12-01

Overwintering monarch butterflies in Mexico select areas of the high elevation Oyamel fir -pine forest providing a canopy that protects them from extremes of cold, heat, sun, and wind. These exacting microclimatic conditions are found in relatively small areas of forest with appropriate topography and canopy cover. The major goal of this investigation is to map topoclimatic and microclimatic conditions within the Monarch Butterfly Biosphere Reserve by combining temperature monitoring (iButton Thermochrons), hemispherical canopy photography, multiple regression, and GIS modeling. Temperature measurements included base weather stations and arrays of Thermochrons (on the north-side of trees at 2m height) across local topographic and canopy cover gradients. Topoclimatic models of minimum temperatures included topographic position, slope, and elevation, and predicted that thermal belts on slopes and cold air drainage into canyons create local minimum temperature gradients of 2°C. Topoclimatic models of maximum temperatures models included elevation, topographic position, and relative solar exposure, with local gradients of 3°C. These models, which are independent of forest canopy structure, were then projected across the entire region. Forest canopy structure, including direct and diffuse solar radiation, was assessed with hemispherical photography at each Thermochron site. Canopy cover affected minimum temperatures primarily on the calmest, coldest nights. Maximum temperatures were predicted by direct radiation below the canopy. Fine- scale grids (25 m spacing) at three overwintering sites characterized effects of canopy gaps and edges on temperature and wind exposure. The effects of temperature variation were considered for lipid loss rates, ability to take flight, and freezing mortality. Lipid loss rates were estimated by measured hourly temperatures. Many of the closed canopy sites allowed for substantial lipid reserves at the end of the season (March 15), but increases in average temperature could effectively deplete lipids by that time. The large influence of canopy cover on daytime maximum temperatures demonstrates that forest thinning directly reduces habitat suitability. Monarchs' flight behavior under warmer conditions suggests that daytime temperatures drive the dynamics of monarch distribution within colonies. Thinning also decreases nighttime minimum temperatures, and increases wind exposure. These results create a basis for quantitative understanding of the combinations of topography and forest structure that provide high quality overwintering habitat.

[The research on bidirectional reflectance computer simulation of forest canopy at pixel scale].

PubMed

Song, Jin-Ling; Wang, Jin-Di; Shuai, Yan-Min; Xiao, Zhi-Qiang

2009-08-01

Computer simulation is based on computer graphics to generate the realistic 3D structure scene of vegetation, and to simulate the canopy regime using radiosity method. In the present paper, the authors expand the computer simulation model to simulate forest canopy bidirectional reflectance at pixel scale. But usually, the trees are complex structures, which are tall and have many branches. So there is almost a need for hundreds of thousands or even millions of facets to built up the realistic structure scene for the forest It is difficult for the radiosity method to compute so many facets. In order to make the radiosity method to simulate the forest scene at pixel scale, in the authors' research, the authors proposed one idea to simplify the structure of forest crowns, and abstract the crowns to ellipsoids. And based on the optical characteristics of the tree component and the characteristics of the internal energy transmission of photon in real crown, the authors valued the optical characteristics of ellipsoid surface facets. In the computer simulation of the forest, with the idea of geometrical optics model, the gap model is considered to get the forest canopy bidirectional reflectance at pixel scale. Comparing the computer simulation results with the GOMS model, and Multi-angle Imaging SpectroRadiometer (MISR) multi-angle remote sensing data, the simulation results are in agreement with the GOMS simulation result and MISR BRF. But there are also some problems to be solved. So the authors can conclude that the study has important value for the application of multi-angle remote sensing and the inversion of vegetation canopy structure parameters.

Seedling survival and growth of three forest tree species: The role of spatial heterogeneity

Treesearch

Brian Beckage; James S. Clark

2003-01-01

Spatial heterogeneity in microenvironments may provide unique regeneration niches for trees and may promote forest diversity. We examined how heterogeneity in understory cover, mineral nutrients, and moisture and their interactions with canopy gaps contribute to the coexistence of three common, co-occuring tree species. We measured survival and height growth of 1080...

Tree root dynamics in montane and sub-alpine mixed forest patches.

PubMed

Wang, Y; Kim, J H; Mao, Z; Ramel, M; Pailler, F; Perez, J; Rey, H; Tron, S; Jourdan, C; Stokes, A

2018-02-28

The structure of heterogeneous forests has consequences for their biophysical environment. Variations in the local climate significantly affect tree physiological processes. We hypothesize that forest structure also alters tree root elongation and longevity through temporal and spatial variations in soil temperature and water potential. We installed rhizotrons in paired vegetation communities of closed forest (tree islands) and open patches (canopy gaps), along a soil temperature gradient (elevations of 1400, 1700 and 2000 m) in a heterogeneous mixed forest. We measured the number of growing tree roots, elongation and mortality every month over 4 years. The results showed that the mean daily root elongation rate (RER) was not correlated with soil water potential but was significantly and positively correlated with soil temperature between 0 and 8 °C only. The RER peaked in spring, and a smaller peak was usually observed in the autumn. Root longevity was dependent on altitude and the season in which roots were initiated, and root diameter was a significant factor explaining much of the variability observed. The finest roots usually grew faster and had a higher risk of mortality in gaps than in closed forest. At 2000 m, the finest roots had a higher risk of mortality compared with the lower altitudes. The RER was largely driven by soil temperature and was lower in cold soils. At the treeline, ephemeral fine roots were more numerous, probably in order to compensate for the shorter growing season. Differences in soil climate and root dynamics between gaps and closed forest were marked at 1400 and 1700 m, but not at 2000 m, where canopy cover was more sparse. Therefore, heterogeneous forest structure and situation play a significant role in determining root demography in temperate, montane forests, mostly through impacts on soil temperature.

Modeling lidar waveforms with time-dependent stochastic radiative transfer theory for remote estimations of forest structure

NASA Astrophysics Data System (ADS)

Kotchenova, Svetlana Y.; Shabanov, Nikolay V.; Knyazikhin, Yuri; Davis, Anthony B.; Dubayah, Ralph; Myneni, Ranga B.

2003-08-01

Large footprint waveform-recording laser altimeters (lidars) have demonstrated a potential for accurate remote sensing of forest biomass and structure, important for regional and global climate studies. Currently, radiative transfer analyses of lidar data are based on the simplifying assumption that only single scattering contributes to the return signal, which may lead to errors in the modeling of the lower portions of recorded waveforms in the near-infrared spectrum. In this study we apply time-dependent stochastic radiative transfer (RT) theory to model the propagation of lidar pulses through forest canopies. A time-dependent stochastic RT equation is formulated and solved numerically. Such an approach describes multiple scattering events, allows for realistic representation of forest structure including foliage clumping and gaps, simulates off-nadir and multiangular observations, and has the potential to provide better approximations of return waveforms. The model was tested with field data from two conifer forest stands (southern old jack pine and southern old black spruce) in central Canada and two closed canopy deciduous forest stands (with overstory dominated by tulip poplar) in eastern Maryland. Model-simulated signals were compared with waveforms recorded by the Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) over these regions. Model simulations show good agreement with SLICER signals having a slow decay of the waveform. The analysis of the effects of multiple scattering shows that multiply scattered photons magnify the amplitude of the reflected signal, especially that originating from the lower portions of the canopy.

Historic disturbance regimes promote tree diversity only under low browsing regimes in eastern deciduous forest

Treesearch

Tim Nuttle; Alejandro A. Royo; Mary Beth Adams; Walter P. Carson

2013-01-01

Eastern deciduous forests are changing in species composition and diversity outside of classical successional trajectories. Three disturbance mechanisms appear central to this phenomenon: fire frequency is reduced, canopy gaps are smaller, and browsers are more abundant. Which factor is most responsible is a matter of great debate and remains unclear, at least partly...

Behavioral activities of male Cerulean Warblers in relation to habitat characteristics

USGS Publications Warehouse

Wood, Petra Bohall; Perkins, Kelly A.

2012-01-01

Activities of 29 male Cerulean Warblers (Setophaga cerulea) were quantified on two sites in West Virginia during May–June 2005. Singing and foraging were the most common of 11 observed behavioral activities (81.6%), while maintenance and mating behaviors were uncommonly observed. Male activity differed among vegetative strata (P  =  0.02) with lower- and mid-canopy strata used most often (70% of observations), especially for foraging, perching, and preening. The upper-canopy was used primarily for singing, particularly within core areas of territories and in association with canopy gaps. Foraging occurred more than expected outside of core areas. Males were associated with canopy gaps during 30% of observations, but the distribution of behavioral activities was not significantly related (P  =  0.06) to gap presence. Males used 23 different tree species for a variety of activities with oaks (Quercus spp.) used most often on the xeric site and black cherry (Prunus serotina) and black locust (Robinia pseudoacacia) on the mesic site. Tree species used for singing differed between core and non-core areas (P < 0.0001) but distribution of singing and foraging activity did not differ among tree species (P  =  0.13). Cerulean Warblers appear to be flexible in use of tree species. Their use of different canopy strata for different behavioral activities provides an explanation for the affinity this species exhibits for a vertically stratified forest canopy.

Comparison of modeled backscatter with SAR data at P-band

NASA Technical Reports Server (NTRS)

Wang, Yong; Davis, Frank W.; Melack, John M.

1992-01-01

In recent years several analytical models were developed to predict microwave scattering by trees and forest canopies. These models contribute to the understanding of radar backscatter over forested regions to the extent that they capture the basic interactions between microwave radiation and tree canopies, understories, and ground layers as functions of incidence angle, wavelength, and polarization. The Santa Barbara microwave model backscatter model for woodland (i.e. with discontinuous tree canopies) combines a single-tree backscatter model and a gap probability model. Comparison of model predictions with synthetic aperture radar (SAR) data and L-band (lambda = 0.235 m) is promising, but much work is still needed to test the validity of model predictions at other wavelengths. The validity of the model predictions at P-band (lambda = 0.68 m) for woodland stands at our Mt. Shasta test site was tested.

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.

Regeneration patterns of northern white cedar, an old-growth forest dominant

USGS Publications Warehouse

Scott, Michael L.; Murphy, Peter G.

1987-01-01

Regeneration of Thuja occidentalis L. was examined in an old-growth dune forest on South Manitou Island, Michigan. To estimate the current status of cedar regeneration, we determined size structure of seedlings and stems and analyzed present patterns of establishment and persistence relative to substrate type. There has been a shift in the pattern of cedar establishment from soil to log substrates. While 97% of all stems ≥15 cm dbh are associated with a soil substrate, 81% of stems ≥2.5cm-25 cm tall. There was no significant relationship between the state of log decay and the density of seedlings >25 cm in height, indicating that long-term survival is not dependent on the degree of log decomposition. However, survival on logs is associated with canopy openings. Seedlings >25 cm tall were associated with gaps, and 78% of cedar stems (≥2.5 cm dbh) on logs were associated with a single windthrow gap. Thus, current cedar regeneration in this old-growth forest depends on logs and the canopy openings associated with them.

Improving representation of canopy temperatures for modeling subcanopy incoming longwave radiation to the snow surface

NASA Astrophysics Data System (ADS)

Webster, Clare; Rutter, Nick; Jonas, Tobias

2017-09-01

A comprehensive analysis of canopy surface temperatures was conducted around a small and large gap at a forested alpine site in the Swiss Alps during the 2015 and 2016 snowmelt seasons (March-April). Canopy surface temperatures within the small gap were within 2-3°C of measured reference air temperature. Vertical and horizontal variations in canopy surface temperatures were greatest around the large gap, varying up to 18°C above measured reference air temperature during clear-sky days. Nighttime canopy surface temperatures around the study site were up to 3°C cooler than reference air temperature. These measurements were used to develop a simple parameterization for correcting reference air temperature for elevated canopy surface temperatures during (1) nighttime conditions (subcanopy shortwave radiation is 0 W m-2) and (2) periods of increased subcanopy shortwave radiation >400 W m-2 representing penetration of shortwave radiation through the canopy. Subcanopy shortwave and longwave radiation collected at a single point in the subcanopy over a 24 h clear-sky period was used to calculate a nighttime bulk offset of 3°C for scenario 1 and develop a multiple linear regression model for scenario 2 using reference air temperature and subcanopy shortwave radiation to predict canopy surface temperature with a root-mean-square error (RMSE) of 0.7°C. Outside of these two scenarios, reference air temperature was used to predict subcanopy incoming longwave radiation. Modeling at 20 radiometer locations throughout two snowmelt seasons using these parameterizations reduced the mean bias and RMSE to below 10 W m s-2 at all locations.

Long-term retention of (137)Cs in three forest soil types with different soil properties.

PubMed

Suchara, Ivan; Sucharová, Julie; Holá, Marie; Pilátová, Helena; Rulík, Petr

2016-07-01

Current (137)Cs activity concentrations were studied at three localities in individual soil horizons of Stagnosol, Arenic Podzol and Haplic Cambisol soil units in soil blocks with dimensions of 20 × 20 × 40 cm situated below pine canopies (n = 3) and spruce canopies (n = 3), and below small canopy gaps, at least 15 × 15 m in area (n = 3 + 3), which have probably endured since 1986. The main zone of (137)Cs accumulation in all the localities was found to be in the organic horizons (H and F). No significant transport and accumulation of (137)Cs into illuvial soil horizons (Bm, Bs or Bhs, Bv and Bv/IIC) was found. The estimated current total (137)Cs activity concentrations in the soil blocks 40 cm in depth were only slightly higher below the coniferous canopy than they were below nearby canopy gaps. The inventory of (137)Cs in the soils was found to be in accordance with the estimated (137)Cs inputs from the Chernobyl fallout and from global fallout. The low amounts of (137)Cs found accumulated in the aboveground biomass (mosses, grasses, needles) did not substantially bias the studied radiocaesium balance in the soils. The vertical migration rate of (137)Cs in soils (cm/year) had a tendency to be higher below canopies than below canopy gaps and below pine canopies than below spruce canopies. We expected the current (137)Cs activity concentrations in the individual soil horizons to be related to the studied soil parameters: pH (H2O), pH (CaCl2), content of organic matter and mineral portion and portion of humic and fulvic acid contents (Q4/6). However, this was not confirmed. Similarly, we observed a weak tendency toward higher (137)Cs activity in soils below the canopy than in soils below canopy gaps. The available gaps used in our study may have been too small, and they may have been affected by an accumulation of litter and humus containing (137)Cs from the surrounding plots situated below neighbouring canopies. Copyright © 2016 Elsevier Ltd. All rights reserved.

A neighborhood analysis of the consequences of Quercus suber decline for regeneration dynamics in Mediterranean forests.

PubMed

Ibáñez, Beatriz; Gómez-Aparicio, Lorena; Stoll, Peter; Ávila, José M; Pérez-Ramos, Ignacio M; Marañón, Teodoro

2015-01-01

In forests, the vulnerable seedling stage is largely influenced by the canopy, which modifies the surrounding environment. Consequently, any alteration in the characteristics of the canopy, such as those promoted by forest dieback, might impact regeneration dynamics. Our work analyzes the interaction between canopy neighbors and seedlings in Mediterranean forests affected by the decline of their dominant species (Quercus suber). Our objective was to understand how the impacts of neighbor trees and shrubs on recruitment could affect future dynamics of these declining forests. Seeds of the three dominant tree species (Quercus suber, Olea europaea and Quercus canariensis) were sown in six sites during two consecutive years. Using a spatially-explicit, neighborhood approach we developed models that explained the observed spatial variation in seedling emergence, survival, growth and photochemical efficiency as a function of the size, identity, health, abundance and distribution of adult trees and shrubs in the neighborhood. We found strong neighborhood effects for all the performance estimators, particularly seedling emergence and survival. Tree neighbors positively affected emergence, independently of species identity or health. Alternatively, seedling survival was much lower in neighborhoods dominated by defoliated and dead Q. suber trees than in neighborhoods dominated by healthy trees. For the two oak species, these negative effects were consistent over the three years of the experimental seedlings. These results indicate that ongoing changes in species' relative abundance and canopy trees' health might alter the successional trajectories of Mediterranean oak-forests through neighbor-specific impacts on seedlings. The recruitment failure of dominant late-successional oaks in the gaps opened after Q. suber death would indirectly favor the establishment of other coexisting woody species, such as drought-tolerant shrubs. This could lead current forests to shift into open systems with lower tree cover. Adult canopy decline would therefore represent an additional factor threatening the recruitment of Quercus forests worldwide.

Towards ground-truthing of spaceborne estimates of above-ground life biomass and leaf area index in tropical rain forests

NASA Astrophysics Data System (ADS)

Köhler, P.; Huth, A.

2010-08-01

The canopy height h of forests is a key variable which can be obtained using air- or spaceborne remote sensing techniques such as radar interferometry or LIDAR. If new allometric relationships between canopy height and the biomass stored in the vegetation can be established this would offer the possibility for a global monitoring of the above-ground carbon content on land. In the absence of adequate field data we use simulation results of a tropical rain forest growth model to propose what degree of information might be generated from canopy height and thus to enable ground-truthing of potential future satellite observations. We here analyse the correlation between canopy height in a tropical rain forest with other structural characteristics, such as above-ground life biomass (AGB) (and thus carbon content of vegetation) and leaf area index (LAI) and identify how correlation and uncertainty vary for two different spatial scales. The process-based forest growth model FORMIND2.0 was applied to simulate (a) undisturbed forest growth and (b) a wide range of possible disturbance regimes typically for local tree logging conditions for a tropical rain forest site on Borneo (Sabah, Malaysia) in South-East Asia. In both undisturbed and disturbed forests AGB can be expressed as a power-law function of canopy height h (AGB = a · hb) with an r2 ~ 60% if data are analysed in a spatial resolution of 20 m × 20 m (0.04 ha, also called plot size). The correlation coefficient of the regression is becoming significant better in the disturbed forest sites (r2 = 91%) if data are analysed hectare wide. There seems to exist no functional dependency between LAI and canopy height, but there is also a linear correlation (r2 ~ 60%) between AGB and the area fraction of gaps in which the canopy is highly disturbed. A reasonable agreement of our results with observations is obtained from a comparison of the simulations with permanent sampling plot (PSP) data from the same region and with the large-scale forest inventory in Lambir. We conclude that the spaceborne remote sensing techniques such as LIDAR and radar interferometry have the potential to quantify the carbon contained in the vegetation, although this calculation contains due to the heterogeneity of the forest landscape structural uncertainties which restrict future applications to spatial averages of about one hectare in size. The uncertainties in AGB for a given canopy height are here 20-40% (95% confidence level) corresponding to a standard deviation of less than ± 10%. This uncertainty on the 1 ha-scale is much smaller than in the analysis of 0.04 ha-scale data. At this small scale (0.04 ha) AGB can only be calculated out of canopy height with an uncertainty which is at least of the magnitude of the signal itself due to the natural spatial heterogeneity of these forests.

Assessing the impact of Amazonia logging with a new ecosystem model

NASA Astrophysics Data System (ADS)

Huang, M.; Asner, G. P.; Keller, M.; Berry, J. A.; Bustamante, M. M.

2006-12-01

Old-growth Amazonian forests play a fundamental role in the global climate and carbon cycle. Land use in old- growth tropical forests contributes to the accumulation of CO2 in the atmosphere and can alter the hydrological cycle, locally, regionally, and globally. Although deforestation, largely for the conversion of land to food crops or pastures, is the major destructive force in tropical forests worldwide (Houghton et al., 2000), other forest disturbances such as the selective logging have also increased in frequency and extent. Selective logging causes widespread collateral damage to remaining trees, sub-canopy vegetation, and soils, with impacts on hydrological processes, erosion, fire, carbon storage, and plant and animal species. In this study, the impact of selective logging on the carbon budget of the Brazil Amazon region is assessed with a new 3-D version of the Carnegie-Ames-Stanford Approach (CASA) ecosystem model, which features: (1) an alternative way of estimating absorbed photosynthetically-active radiation (APAR) by taking advantage of new high-resolution maps of forest canopy gap fraction; (2) a pulse disturbance module to realistically modify the carbon pools after timber harvest; (3) a regrowth module considering changes in community composition; and (4) a radiative transfer module for charactering the dynamic 3-D light environment above the canopy and within gaps after logging. The model was calibrated and validated with field observations from the Large-scale Biosphere Atmosphere Experiment (LBA) and its sensitivity was evaluated with Monte Carlo simulations. The impacts of selected logging on regional carbon budget of the Brazilian Amazon were then assessed under different future climate change scenarios. Results from this study quantify the gross and net carbon storage effects of widespread logging practices throughout the Brazilian Amazon.

Release of Suppressed Red Spruce Using Canopy Gap Creation--Ecological Restoration in the Central Appalachians

Treesearch

J.S. Rentch; W.M. Ford; Thomas Schuler; Jeff Palmer; C.A. Diggins

2016-01-01

Red spruce (Picea rubens) and red spruce-northern hardwood mixed stands once covered as much as 300,000 ha in the Central Appalachians, but now comprise no more than 21,000 ha. Recently, interest in restoration of this forest type has increased because red spruce forests provide habitat for a number of rare animal species. Our study reports the...

Use of Fouler Transforms to define landscape scales of analysis for disturbances: A case study of thinned and unthinned forest stands

Treesearch

J. E. Lundquist; R. A. Sommerfeld

2002-01-01

Various disturbances such as disease and management practices cause canopy gaps that change patterns of forest stand structure. This study examined the usefulness of digital image analysis using aerial photos, Fourier Tranforms, and cluster analysis to investigate how different spatial statistics are affected by spatial scale. The specific aims were to: 1) evaluate how...

Do deer and shrubs override canopy gap size effects on growth and survival of yellow birch, northern red oak, eastern white pine, and eastern hemlock seedlings?

Treesearch

Cristel C. Kern; Peter B. Reich; Rebecca A. Montgomery; Terry F. Strong

2012-01-01

Innovative forestry practices that use natural disturbance and stand developmental processes as models to increase forest complexity are now being considered as a way to conserve biodiversity while managing for a range of objectives.We evaluated the influence of harvest-created gap size (6, 10, 20, 30, and 46 m diameter gaps and uncut references) over 12 growing...

Spatial and temporal patterns of beetles associated with coarse woody debris in managed bottomland hardwood forests.

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

Ulyshen, M., D.; Hanula, J., L.; Horn, S.

2004-05-13

For. Ecol. and Mgt. 199:259-272. Malaise traps were used to sample beetles in artificial canopy gaps of different size (0.13 ha, 0.26 ha, and0.50 ha) and age in a South Carolina bottomland hardwood forest. Traps were placed at the center, edge, and in the surrounding forest of each gap. Young gaps (ý 1 year) had large amounts of coarse woody debris compared to the surrounding forest, while older gaps (ý 6 years) had virtually none. The total abundance and diversity of wood-dwelling beetles (Buprestidae, Cerambycidae, Brentidae, Bostrichidae, and Curculionidae (Scolytinae and Platypodinae)) was higher in the center of young gapsmore » than in the center of old gaps. The abundance was higher in the center of young gaps than in the surrounding forest, while the forest surrounding old gaps and the edge of old gaps had a higher abundance and diversity of wood-dwelling beetles than did the center of old gaps. There was no difference in wood-dwelling beetle abundance between gaps of different size, but diversity was lower in 0.13 ha old gaps than in 0.26 ha or 0.50 ha old gaps. We suspect that gap size has more of an effect on woodborer abundance than indicated here because malaise traps sample a limited area. The predaceous beetle family Cleridae showed a very similar trend to that of the woodborers. Coarse woody debris is an important resource for many organisms, and our results lend further support to forest management practices that preserve coarse woody debris created during timber removal.« less

Gap Shape Classification using Landscape Indices and Multivariate Statistics

PubMed Central

Wu, Chih-Da; Cheng, Chi-Chuan; Chang, Che-Chang; Lin, Chinsu; Chang, Kun-Cheng; Chuang, Yung-Chung

2016-01-01

This study proposed a novel methodology to classify the shape of gaps using landscape indices and multivariate statistics. Patch-level indices were used to collect the qualified shape and spatial configuration characteristics for canopy gaps in the Lienhuachih Experimental Forest in Taiwan in 1998 and 2002. Non-hierarchical cluster analysis was used to assess the optimal number of gap clusters and canonical discriminant analysis was used to generate the discriminant functions for canopy gap classification. The gaps for the two periods were optimally classified into three categories. In general, gap type 1 had a more complex shape, gap type 2 was more elongated and gap type 3 had the largest gaps that were more regular in shape. The results were evaluated using Wilks’ lambda as satisfactory (p < 0.001). The agreement rate of confusion matrices exceeded 96%. Differences in gap characteristics between the classified gap types that were determined using a one-way ANOVA showed a statistical significance in all patch indices (p = 0.00), except for the Euclidean nearest neighbor distance (ENN) in 2002. Taken together, these results demonstrated the feasibility and applicability of the proposed methodology to classify the shape of a gap. PMID:27901127

Gap Shape Classification using Landscape Indices and Multivariate Statistics.

PubMed

Wu, Chih-Da; Cheng, Chi-Chuan; Chang, Che-Chang; Lin, Chinsu; Chang, Kun-Cheng; Chuang, Yung-Chung

2016-11-30

This study proposed a novel methodology to classify the shape of gaps using landscape indices and multivariate statistics. Patch-level indices were used to collect the qualified shape and spatial configuration characteristics for canopy gaps in the Lienhuachih Experimental Forest in Taiwan in 1998 and 2002. Non-hierarchical cluster analysis was used to assess the optimal number of gap clusters and canonical discriminant analysis was used to generate the discriminant functions for canopy gap classification. The gaps for the two periods were optimally classified into three categories. In general, gap type 1 had a more complex shape, gap type 2 was more elongated and gap type 3 had the largest gaps that were more regular in shape. The results were evaluated using Wilks' lambda as satisfactory (p < 0.001). The agreement rate of confusion matrices exceeded 96%. Differences in gap characteristics between the classified gap types that were determined using a one-way ANOVA showed a statistical significance in all patch indices (p = 0.00), except for the Euclidean nearest neighbor distance (ENN) in 2002. Taken together, these results demonstrated the feasibility and applicability of the proposed methodology to classify the shape of a gap.

Tropical Forest Fragmentation Limits Movements, but Not Occurrence of a Generalist Pollinator Species

PubMed Central

Volpe, Noelia L.; Robinson, W. Douglas; Frey, Sarah J. K.; Hadley, Adam S.; Betts, Matthew G.

2016-01-01

Habitat loss and fragmentation influence species distributions and therefore ecological processes that depend upon them. Pollination may be particularly susceptible to fragmentation, as it depends on frequent pollinator movement. Unfortunately, most pollinators are too small to track efficiently which has precluded testing the hypothesis that habitat fragmentation reduces or eliminates pollen flow by disrupting pollinator movement. We used radio-telemetry to examine space use of the green hermit hummingbird (Phaethornis guy), an important ‘hub’ pollinator of understory flowering plants across substantial portions of the neotropics and the primary pollinator of a keystone plant which shows reduced pollination success in fragmented landscapes. We found that green hermits strongly avoided crossing large stretches of non-forested matrix and preferred to move along stream corridors. Forest gaps as small as 50 m diminished the odds of movement by 50%. Green hermits occurred almost exclusively inside the forest, with the odds of occurrence being 8 times higher at points with >95% canopy cover compared with points having <5% canopy cover. Nevertheless, surprisingly. the species occurred in fragmented landscapes with low amounts of forest (~30% within a 2 km radius). Our results indicate that although green hermits are present even in landscapes with low amounts of tropical forest, movement within these landscapes ends up strongly constrained by forest gaps. Restricted movement of pollinators may be an underappreciated mechanism for widespread declines in pollination and plant fitness in fragmented landscapes, even when in the presence of appropriate pollinators. PMID:27941984

Legacy of Pre-Disturbance Spatial Pattern Determines Early Structural Diversity following Severe Disturbance in Montane Spruce Forests

PubMed Central

Bače, Radek; Svoboda, Miroslav; Janda, Pavel; Morrissey, Robert C.; Wild, Jan; Clear, Jennifer L.; Čada, Vojtěch; Donato, Daniel C.

2015-01-01

Background Severe canopy-removing disturbances are native to many temperate forests and radically alter stand structure, but biotic legacies (surviving elements or patterns) can lend continuity to ecosystem function after such events. Poorly understood is the degree to which the structural complexity of an old-growth forest carries over to the next stand. We asked how pre-disturbance spatial pattern acts as a legacy to influence post-disturbance stand structure, and how this legacy influences the structural diversity within the early-seral stand. Methods Two stem-mapped one-hectare forest plots in the Czech Republic experienced a severe bark beetle outbreak, thus providing before-and-after data on spatial patterns in live and dead trees, crown projections, down logs, and herb cover. Results Post-disturbance stands were dominated by an advanced regeneration layer present before the disturbance. Both major species, Norway spruce (Picea abies) and rowan (Sorbus aucuparia), were strongly self-aggregated and also clustered to former canopy trees, pre-disturbance snags, stumps and logs, suggesting positive overstory to understory neighbourhood effects. Thus, although the disturbance dramatically reduced the stand’s height profile with ~100% mortality of the canopy layer, the spatial structure of post-disturbance stands still closely reflected the pre-disturbance structure. The former upper tree layer influenced advanced regeneration through microsite and light limitation. Under formerly dense canopies, regeneration density was high but relatively homogeneous in height; while in former small gaps with greater herb cover, regeneration density was lower but with greater heterogeneity in heights. Conclusion These findings suggest that pre-disturbance spatial patterns of forests can persist through severe canopy-removing disturbance, and determine the spatial structure of the succeeding stand. Such patterns constitute a subtle but key legacy effect, promoting structural complexity in early-seral forests as well as variable successional pathways and rates. This influence suggests a continuity in spatial ecosystem structure that may well persist through multiple forest generations. PMID:26421726

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.

Tree species effects on topsoil properties in an old tropical plantation

NASA Astrophysics Data System (ADS)

Bauters, Marijn; Boeckx, Pascal; Ampoorter, Evy; Verbeeck, Hans; Döetterl, Sebastian; Baert, Geert; Verheyen, Kris

2016-04-01

Forest biogeochemistry is strongly linked to the functional strategies of the tree community and the topsoil. Research has long documented that tree species affect soil properties in forests. Our current understanding on this interaction is mainly based on common garden experiments in temperate forest and needs to be extended to other ecosystems if we want to understand this interaction in natural forests worldwide. Using a 77-year-old tropical experimental plantation from central Africa, we examined the relationship between canopy and litter chemical traits and topsoil properties. By the current diversity in this site, the unique setup allowed us to extend the current knowledge from temperate and simplified systems to near-natural tropical forests, and thus bridge the gap between planted monocultures in common gardens, and correlative studies in natural systems. We linked the species-specific leaf and litter chemical traits to the topsoil cation composition, acidity, pH and soil organic matter. We found that average canopy trait values were a better predictor for the topsoil than the litter chemistry. Canopy base cation content positively affected topsoil pH and negatively affected acidity. These, in turn strongly determined the soil organic carbon contents of the topsoil, which ranged a tree-fold in the experiment.

Spatial Configuration of Drought Disturbance and Forest Gap Creation across Environmental Gradients

PubMed Central

Andrew, Margaret E.; Ruthrof, Katinka X.; Matusick, George; Hardy, Giles E. St. J.

2016-01-01

Climate change is increasing the risk of drought to forested ecosystems. Although drought impacts are often anecdotally noted to occur in discrete patches of high canopy mortality, the landscape effects of drought disturbances have received virtually no study. This study characterized the landscape configuration of drought impact patches and investigated the relationships between patch characteristics, as indicators of drought impact intensity, and environmental gradients related to water availability to determine factors influencing drought vulnerability. Drought impact patches were delineated from aerial surveys following an extreme drought in 2011 in southwestern Australia, which led to patchy canopy dieback of the Northern Jarrah Forest, a Mediterranean forest ecosystem. On average, forest gaps produced by drought-induced dieback were moderate in size (6.6 ± 9.7 ha, max = 85.7 ha), compact in shape, and relatively isolated from each other at the scale of several kilometers. However, there was considerable spatial variation in the size, shape, and clustering of forest gaps. Drought impact patches were larger and more densely clustered in xeric areas, with significant relationships observed with topographic wetness index, meteorological variables, and stand height. Drought impact patch clustering was more strongly associated with the environmental factors assessed (R2 = 0.32) than was patch size (R2 = 0.21); variation in patch shape remained largely unexplained (R2 = 0.02). There is evidence that the xeric areas with more intense drought impacts are ‘chronic disturbance patches’ susceptible to recurrent drought disturbance. The spatial configuration of drought disturbances is likely to influence ecological processes including forest recovery and interacting disturbances such as fire. Regime shifts to an alternate, non-forested ecosystem may occur preferentially in areas with large or clustered drought impact patches. Improved understanding of drought impacts and their patterning in space and time will expand our knowledge of forest ecosystems and landscape processes, informing management of these dynamic systems in an uncertain future. PMID:27275744

Indirect effects of emerald ash borer-induced ash mortality and canopy gap formation on epigaeic beetles.

PubMed

Gandhi, Kamal J K; Smith, Annemarie; Hartzler, Diane M; Herms, Daniel A

2014-06-01

Exotic herbivorous insects have drastically and irreversibly altered forest structure and composition of North American forests. For example, emerald ash borer (Agrilus planipennis Fairmaire) from Asia has caused wide-scale mortality of ash trees (Fraxinus spp.) in eastern United States and Canada. We studied the effects of forest changes resulting from emerald ash borer invasion on epigaeic or ground beetles (Coleoptera: Carabidae) along a gradient of ash dieback and gap sizes in southeastern Michigan. Ground beetles were sampled in hydric, mesic, and xeric habitats in which black (Fraxinus nigra Marshall), green (Fraxinus pennsylvanica Marshall), and white (Fraxinus americana L.) ash were the most common species, respectively. During 2006-2007, we trapped 2,545 adult ground beetles comprising 52 species. There was a negative correlation between percent ash tree mortality in 2006 and catches of all beetles. Catches of Agonum melanarium Dejean (in 2006) and Pterostichus mutus (Say) (in 2006-2007) were negatively correlated with tree mortality and gap size, respectively. However, catches of Pterostichus corvinus Dejean were positively correlated with gap size in 2006. As ash mortality and average gap size increased from 2006 to 2007, catches of all beetles as well as P. mutus and Pterostichus stygicus (Say) increased (1.3-3.9 times), while species diversity decreased, especially in mesic and xeric stands. Cluster analysis revealed that beetle assemblages in hydric and mesic stand diverged (25 and 40%, respectively) in their composition from 2006 to 2007, and that hydric stands had the most unique beetle assemblages. Overall, epigaeic beetle assemblages were altered in ash stands impacted by emerald ash borer; however, these impacts may dissipate as canopy gaps close.

Effects of gap size, duration of daylight, and presence of leaf litter on forest regeneration

Treesearch

G. Andrew Bartholomay; Todd W. Bowersox

2003-01-01

Selection systems are used to manage multi-cohort forest stands by removing individual and/or groups of trees to create 0.01- to 1.0-ha openings in the canopy. Inherent in the selection system are the dual roles of tending the residual trees and regenerating a new cohort of tree seedlings. Research of silvicultural selection systems has historically focused on the...

Watershed Land Use and Seasonal Variation Constrain the ...

EPA Pesticide Factsheets

While watershed and local scale controls on stream metabolism have been independently investigated, little is known about how controls exerted at these different scales interact to determine stream metabolic rates, or how these interactions vary across seasons. To address this knowledge gap, we measured ecosystem metabolism in four urban and four reference streams in northern Kentucky, USA, with paired closed and open riparian canopies, during each of the four seasons of the year. Gross primary production (GPP), ecosystem respiration (ER), and net ecosystem production (NEP) were all best predicted by models with season as a main effect, but interactions between season, canopy and watershed varied for each response. Urban streams exhibited higher GPP during most seasons, likely due to elevated nutrient loads. Open canopy reaches in both urban and forested streams supported higher rates of GPP than the closed canopy reaches during the summer and fall when the overhead vegetation shaded the closed reaches. Surprisingly, the effect of canopy cover on GPP was similar among urban and forested streams. The combination of watershed and local-scale controls resulted in urban streams that alternated between net heterotrophy (NEP 0) between seasons with and without dense canopy cover. This finding has management relevance because net production can lead to accumulation of algal biomass and associated issues like dissolved oxygen sags at night. Our study reinforces

Further Studies of Forest Structure Parameter Retrievals Using the Echidna® Ground-Based Lidar

NASA Astrophysics Data System (ADS)

Strahler, A. H.; Yao, T.; Zhao, F.; Yang, X.; Schaaf, C.; Wang, Z.; Li, Z.; Woodcock, C. E.; Culvenor, D.; Jupp, D.; Newnham, G.; Lovell, J.

2012-12-01

Ongoing work with the Echidna® Validation Instrument (EVI), a full-waveform, ground-based scanning lidar (1064 nm) developed by Australia's CSIRO and deployed by Boston University in California conifers (2008) and New England hardwood and softwood (conifer) stands (2007, 2009, 2010), confirms the importance of slope correction in forest structural parameter retrieval; detects growth and disturbance over periods of 2-3 years; provides a new way to measure the between-crown clumping factor in leaf area index retrieval using lidar range; and retrieves foliage profiles with more lower-canopy detail than a large-footprint aircraft scanner (LVIS), while simulating LVIS foliage profiles accurately from a nadir viewpoint using a 3-D point cloud. Slope correction is important for accurate retrieval of forest canopy structural parameters, such as mean diameter at breast height (DBH), stem count density, basal area, and above-ground biomass. Topographic slope can induce errors in parameter retrievals because the horizontal plane of the instrument scan, which is used to identify, measure, and count tree trunks, will intersect trunks below breast height in the uphill direction and above breast height in the downhill direction. A test of three methods at southern Sierra Nevada conifer sites improved the range of correlations of these EVI-retrieved parameters with field measurements from 0.53-0.68 to 0.85-0.93 for the best method. EVI scans can detect change, including both growth and disturbance, in periods of two to three years. We revisited three New England forest sites scanned in 2007-2009 or 2007-2010. A shelterwood stand at the Howland Experimental Forest, Howland, Maine, showed increased mean DBH, above-ground biomass and leaf area index between 2007 and 2009. Two stands at the Harvard Forest, Petersham, Massachusetts, suffered reduced leaf area index and reduced stem count density as the result of an ice storm that damaged the stands. At one stand, broken tops were visible in the 2010 point cloud canopy reconstruction. A new method for retrieval of the forest canopy between-crown clumping index from angular gaps in hemispherically-projected EVI data traces gaps as they narrow with range from the instrument, thus providing the approximate physical size, rather than angular size, of the gaps. In applying this method to a range of sites in the southern Sierra Nevada, element clumping index values are lower (more between-crown clumping effect) in more open stands, providing improved results as compared to conventional hemispherical photography. In dense stands with fewer gaps, the clumping index values were closer. Foliage profiles retrieved from EVI scans at five Sierra Nevada sites are closely correlated with those of the airborne Lidar Vegetation Imaging Sensor (LVIS) when averaged over a diameter of 100 m. At smaller diameters, the EVI scans have more detail in lower canopy layers and the LVIS and EVI foliage profiles are more distinct. Foliage profiles derived from processing 3-D site point clouds with a nadir view match the LVIS foliage profiles more closely than profiles derived from EVI in scan mode. Removal of terrain effects significantly enhances the match with LVIS profiles. This research was supported by the US National Science Foundation under grant MRI DBI-0923389.

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.

Estimating forest canopy fuel parameters using LIDAR data.

Treesearch

Hans-Erik Andersen; Robert J. McGaughey; Stephen E. Reutebuch

2005-01-01

Fire researchers and resource managers are dependent upon accurate, spatially-explicit forest structure information to support the application of forest fire behavior models. In particular, reliable estimates of several critical forest canopy structure metrics, including canopy bulk density, canopy height, canopy fuel weight, and canopy base height, are required to...

Three-dimensional feature extraction and geometric mappings for improved parameter estimation in forested terrain using airborne LiDAR data

NASA Astrophysics Data System (ADS)

Lee, Heezin

Scanning laser ranging technology is well suited for measuring point-to-point distances because of its ability to generate small beam divergences. As a result, many of the laser pulses emitted from airborne light detection and ranging (LiDAR) systems are able to reach the ground underneath tree canopies through small (10 cm scale) gaps in the foliage. Using high pulse rate lasers and fast optical scanners, airborne LiDAR systems can provide both high spatial resolution and canopy penetration, and these data have become more widely available in recent years for use in environmental and forestry applications. The small-footprint, discrete-return Airborne Laser Swath Mapping (ALSM) system at the University of Florida (UF) is used to directly measure ground surface elevations and the three-dimensional (3D) distribution of the vegetative material above the soil surface. Field of view geometric mappings are explored to find optical gaps inside forests. First, a method is developed to detect walking trails in natural forests that are obscured from above by the canopy. Several features are derived from the ALSM data and used to constrain the search space and infer the location of trails. Second, a robust and simple procedure for estimating intercepted photosynthetically active radiation (IPAR), which is an important measure of forest timber productivity and of daylight visibility in forested terrain, is presented. Simple scope functions that isolate the relevant LiDAR reflections between observer locations and the sun are defined and shown to give good agreement between the LiDAR-derived estimates and values of IPAR measured in situ. A conical scope function with an angular divergence from the centerline of +/-7° provided the best agreement with the in situ measurements. This scope function yielded remarkably consistent IPAR estimates for different pine species and growing conditions. The developed idea could be extended, through potential future work, to characterize the spatial distribution of attenuation of GPS (L-band) microwave signals and of detectability from the sky for military personnel operating in forested terrain. Measuring individual trees can provide valuable information about forests, and airborne LiDAR sensors have been recently used to identify individual trees and measure structural tree parameters. Past results, however, have been mixed because of reliance on interpolated (image) versions of the LiDAR measurements and search methods that do not adapt to variations in canopies. In this work, an adaptive clustering method is developed using 3D airborne LiDAR data acquired over two distinctly different managed pine forests in North-Central Florida, USA. A critical issue in isolating individual trees is determining the appropriate size of the moving window (search radius) when locating seed points. The proposed approach works directly on the 3D "cloud" of LiDAR points and adapts to irregular canopy sizes. The region growing step yields collectively exhaustive sets in an initial segmentation of tree canopies. An agglomerative clustering step is then used to merge clusters that represent parts of whole canopies using the locally varying height distribution. The overall tree detection accuracy achieved is 95.1% with no significant bias. The tree detection enables subsequent estimation of tree height and vertical crown length to an accuracy of better than 0.8 m and 1.5 m, respectively. Lastly, a compact representation of the different geometric characteristics of the segmented LiDAR points is introduced using spin images as a new tool that can potentially help tree detection in complex natural forests.

Multiyear Multiseasonal Changes in Leaf and Canopy Traits Measured by AVIRIS over Ecosystems with Different Functional Type Characteristics Through the Progressive California Drought 2013-2015

NASA Astrophysics Data System (ADS)

Ustin, S.; Roth, K. L.; Huesca, M.; Casas, A.; Adeline, K.; Drewry, D.; Koltunov, A.; Ramirez, C.

2015-12-01

Given the known heterogeneity in ecological processes within plant communities in California, we questioned whether the concept of conventional plant functional types (cPFTs) was adequate to characterize the functionality of the dominant species in these communities. We examined seasonal (spring, summer, fall) airborne AVIRIS and MASTER imagery collected during three years of progressive drought in California, and airborne LiDAR acquired once, for ecosystems that represent a wide range of plant functional types, from annual agriculture and herbaceous perennial wetlands, to forests and shrublands, including broadleaf deciduous and evergreen species and conifer species. These data were used to determine the extent to which changes in canopy chemistry could be detected, quantified, and related to leaf and canopy traits that are indicators of physiological functioning (water content, Leaf Mass Area, total C, N, and pigments (chlorophyll a, b, and carotenoids). At the canopy scale we measured leaf area index, and for forests — species, height, canopy area, DBH, deciduous or evergreen, broadleaf or needleleaf, and gap size. Strong correlations between leaf and canopy traits were predictable and quantifiable from spectroscopy data. Key structural properties of canopy height, biomass and complexity, a measure of spatial and vertical heterogeneity, were predicted by AVIRIS and validated against LiDAR data. Our data supports the hypothesis that optical sensors provide more detailed information about the distribution and variability in leaf and canopy traits related to plant functionality than cPFTs.

A cool-temperate young larch plantation as a net methane source - A 4-year continuous hyperbolic relaxed eddy accumulation and chamber measurements

NASA Astrophysics Data System (ADS)

Ueyama, Masahito; Yoshikawa, Kota; Takagi, Kentaro

2018-07-01

Upland forests are thought to be methane (CH4) sinks due to oxidation by methanotrophs in aerobic soils. However, CH4 budget for upland forests are not well quantified at the ecosystem scale, when possible CH4 sources, such as small wet areas, exists in the ecosystem. Here, we quantified CH4 fluxes in a cool-temperate larch plantation based on four-year continuous measurements using the hyperbolic relaxed eddy accumulation (HREA) method and dynamic closed chambers with a laser-based analyzer. After filling data gaps for half-hourly data using machine-learning-based regressions, we found that the forest acted as a net CH4 source at the canopy scale: 30 ± 11 mg CH4 m-2 yr-1 in 2014, 56 ± 8 mg CH4 m-2 yr-1 in 2015, 154 ± 5 mg CH4 m-2 yr-1 in 2016, and 132 ± 6 mg CH4 m-2 yr-1 in 2017. Hotspot emissions from the edge of the pond could strongly contribute to the canopy-scale emissions. The magnitude of the hotspot emissions was 10-100 times greater than the order of the canopy-scale and chamber-based CH4 fluxes at the dry soils. The high temperatures with wet conditions stimulated the hotspot emissions, and thus induced canopy-scale CH4 emissions in the summer. Understanding and modeling the dynamics of hotspot emissions are important for quantifying CH4 budgets of upland forests. Micrometeorological measurements at various forests are required for revisiting CH4 budget of upland forests.

Evaluating the Impacts of Extreme Events on Ecological Processes Through the Lens of an Ice Storm Manipulation Experiment

NASA Astrophysics Data System (ADS)

Campbell, J. L.; Rustad, L.; Driscoll, C. T.; Fahey, T.; Garlick, S.; Groffman, P.; Schaberg, P. G.

2016-12-01

It is increasingly evident that human-induced climate change is altering the prevalence and severity of extreme weather events. Ice storms are an example of a rare and typically localized extreme weather event that is difficult to predict and has impacts that are poorly understood. We used long-term data and a field manipulation experiment to evaluate how ice storms alter the structure, function, and composition of forest ecosystems. Plots established after a major ice storm in the Northeast in 1998 were re-sampled to evaluate longer-term (17 yr) responses of tree health, productivity, and species composition. Results indicate, that despite changes in herbaceous vegetation in the years immediately after the ice storm, the forest canopy recovered, albeit with some changes in composition, most notably a release of American Beech. An ice storm field manipulation experiment was used to evaluate mechanistic understanding of short term ecological responses. Water from a stream was sprayed above the forest canopy when air temperatures were below freezing, which was effective in simulating a natural ice storm. The experimental design consisted of three levels of ice thickness treatment with two replicates per treatment. The plots with the two more severe icing treatments experienced significant damage to the forest canopy, creating gaps. These plots also had large inputs of fine and coarse woody debris to the forest floor. The exposure to light and presence of brush piles in the more heavily damaged plots resulted in warming with increased spatial variability of soil temperature. Preliminary results from the early growing season have shown no significant changes in soil respiration or soil solution losses of nutrients despite significant forest canopy damage. Further monitoring will determine whether these trends continue in the future.

Harvest-related edge effects on prey availability and foraging of hooded warblers in a bottomland hardwood forest.

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

John Kilgo

2005-04-20

The effects of harvest-created canopy gaps in bottomland hardwood forests on arthropod abundance and, hence, the foraging ecology of birds are poorly understood. I predicted that arthropod abundance would be high near edges of group-selection harvest gaps and lower in the surrounding forest, and that male Hooded Warblers (Wilsonia citrina) foraging near gaps would find more prey per unit time than those foraging in the surrounding forest. In fact, arthropod abundance was greater >100 m from a gap edge than at 0-30 m or 30-100 m from an edge, due to their abundance on switchcane (Arundinaria gigantea); arthropods did notmore » differ in abundance among distances from gaps on oaks (Quercus spp.) or red maple (Acer rubrum). Similarly, Hooded Warbler foraging attack rates were not higher near gap edges: when foraging for fledglings, attack rate did not differ among distances from gaps, but when foraging for themselves, attack rates actually were lower 0-30 m from gap edges than 30-100 m or >100 m from a gap edge. Foraging attack rate was positively associated with arthropod abundance. Hooded Warblers apparently encountered fewer prey and presumably foraged less efficiently where arthropods were least abundant, i.e., near gaps. That attack rates among birds foraging for fledglings were not affected by distance from gap (and hence arthropod abundance) suggests that prey availability may not be limiting at any location across the forest, despite the depressing effects of gaps on arthropod abundance.« less

Rainfall interception, and its modeling, in Pine and Eucalypt stands in Portugal

NASA Astrophysics Data System (ADS)

de Coninck, H. L.; Keizer, J. J.; Coelho, C. O. A.; van Dijck, S. J. E.; Jetten, V. G.; Warmerdam, P. M. M.; Ferreira, A. J. D.; Boulet, A. K.

2003-04-01

Within the framework of the EU-funded CLIMED project (ICA3-2000-30005), concerning the water management implications of foreseeable climate and land-use changes in central Portugal and northern Africa, the event-based Limburg Soil Erosion Model (LISEM; www.geog.uu.nl/lisem) is intended to provide further insight into water yields, peak flow and timing under possible future rainfall regimes. In the Portuguese study area, LISEM is being applied to two small (< 1km2) catchments with contrasting land covers, dominated by Pinus pinaster Ait. and Eucalyptus globulus Labill. tree stands, respectively. In LISEM, cumulative interception is modelled using the empirical formula by Ashton (1979), i.e. as a function of vegetation cover and canopy storage capacity, which in turn is estimated from the Leaf Area Index using the Von Hoyningen-Huenes (1981) formula. Besides that the appropriateness of the LISEM interception module for forested areas may be questioned, its (optional) substitution in LISEM by a more process-based model like that of Rutter would be more in line with LISEM’s overall model structure. This study has as main aims to assess the suitability of (1) the Ashton formula and (2) the sparse variants of the Gash and Rutter interception models to model rainfall interception measurements carried out in a Pinus pinaster Ait. stand as well as a Eucalyptus globulus Labill. stand. Unlike in the bulk of published studies on forest interception, the experimental set-up structures the sampling space in below-canopy and gaps. The below-canopy sampling space is further divided into two classes on the basis of dendrometric data from a prior inventory of 20x20 m. The two stands are equipped with 15 below-canopy and 5 gap rainfall collectors, 3 of which are automated tipping-buckets gauges. Stemflow is measured for 10 trees per stand, which includes 2 trees with automated tipping-bucket (0.5 l/tip). Between November 2002 and the present time, 31 rainfall events totaling about 850 mm were recorded. Interestingly, these preliminary results reveal that below-canopy rainfall may exceed gap rainfall. This phenomenon can be explained by non-vertical rainfall, increasing the probability of droplets hitting the tree canopy instead of the forest floor. If further measurements confirm it to occur regularly, the suitability of not only the LISEM interception module but also the sparse Rutter and Gash models will, at least conceptually, be in doubt.

Systematic variations in multi-spectral lidar representations of canopy height profiles and gap probability

NASA Astrophysics Data System (ADS)

Chasmer, L.; Hopkinson, C.; Gynan, C.; Mahoney, C.; Sitar, M.

2015-12-01

Airborne and terrestrial lidar are increasingly used in forest attribute modeling for carbon, ecosystem and resource monitoring. The near infra-red wavelength at 1064nm has been utilised most in airborne applications due to, for example, diode manufacture costs, surface reflectance and eye safety. Foliage reflects well at 1064nm and most of the literature on airborne lidar forest structure is based on data from this wavelength. However, lidar systems also operate at wavelengths further from the visible spectrum (e.g. 1550nm) for eye safety reasons. This corresponds to a water absorption band and can be sensitive to attenuation if surfaces contain moisture. Alternatively, some systems operate in the visible range (e.g. 532nm) for specialised applications requiring simultaneous mapping of terrestrial and bathymetric surfaces. All these wavelengths provide analogous 3D canopy structure reconstructions and thus offer the potential to be combined for spatial comparisons or temporal monitoring. However, a systematic comparison of wavelength-dependent foliage profile and gap probability (index of transmittance) is needed. Here we report on two multispectral lidar missions carried out in 2013 and 2015 over conifer, deciduous and mixed stands in Ontario, Canada. The first used separate lidar sensors acquiring comparable data at three wavelengths, while the second used a single sensor with 3 integrated laser systems. In both cases, wavelenegths sampled were 532nm, 1064nm and 1550nm. The experiment revealed significant differences in proportions of returns at ground level, the vertical foliage distribution and gap probability across wavelengths. Canopy attenuation was greatest at 532nm due to photosynthetic plant tissue absorption. Relative to 1064nm, foliage was systematically undersampled at the 10% to 60% height percentiles at both 1550nm and 532nm (this was confirmed with coincident terrestrial lidar data). When using all returns to calculate gap probability, all wavelengths were within 6% but when using first returns only, gap probability was overestimated by 67% at 532nm and 11% by 1550nm. These results demonstrate that each wavelength contains distinct information about canopy attributes and models must account for variations in wavelength if applied to data for monitoring purposes.

Spatial and temporal trends of drought effects in a heterogeneous semi-arid forest ecosystem

USGS Publications Warehouse

Assal, Timothy J.; Anderson, Patrick J.; Sibold, Jason

2016-01-01

Drought has long been recognized as a driving mechanism in the forests of western North America and drought-induced mortality has been documented across genera in recent years. Given the frequency of these events are expected to increase in the future, understanding patterns of mortality and plant response to severe drought is important to resource managers. Drought can affect the functional, physiological, structural, and demographic properties of forest ecosystems. Remote sensing studies have documented changes in forest properties due to direct and indirect effects of drought; however, few studies have addressed this at local scales needed to characterize highly heterogeneous ecosystems in the forest-shrubland ecotone. We analyzed a 22-year Landsat time series (1985–2012) to determine changes in forest in an area that experienced a relatively dry decade punctuated by two years of extreme drought. We assessed the relationship between several vegetation indices and field measured characteristics (e.g. plant area index and canopy gap fraction) and applied these indices to trend analysis to uncover the location, direction and timing of change. Finally, we assessed the interaction of climate and topography by forest functional type. The Normalized Difference Moisture Index (NDMI), a measure of canopy water content, had the strongest correlation with short-term field measures of plant area index (R2 = 0.64) and canopy gap fraction (R2 = 0.65). Over the entire time period, 25% of the forested area experienced a significant (p-value < 0.05) negative trend in NDMI, compared to less than 10% in a positive trend. Coniferous forests were more likely to be associated with a negative NDMI trend than deciduous forest. Forests on southern aspects were least likely to exhibit a negative trend while north aspects were most prevalent. Field plots with a negative trend had a lower live density, and higher amounts of standing dead and down trees compared to plots with no trend. Our analysis identifies spatially explicit patterns of long-term trends anchored with ground based evidence to highlight areas of forest that are resistant, persistent or vulnerable to severe drought. The results provide a long-term perspective for the resource management of this area and can be applied to similar ecosystems throughout western North America.

Soil moisture in sessile oak forest gaps

NASA Astrophysics Data System (ADS)

Zagyvainé Kiss, Katalin Anita; Vastag, Viktor; Gribovszki, Zoltán; Kalicz, Péter

2015-04-01

By social demands are being promoted the aspects of the natural forest management. In forestry the concept of continuous forest has been an accepted principle also in Hungary since the last decades. The first step from even-aged stand to continuous forest can be the forest regeneration based on gap cutting, so small openings are formed in a forest due to forestry interventions. This new stand structure modifies the hydrological conditions for the regrowth. Without canopy and due to the decreasing amounts of forest litter the interception is less significant so higher amount of precipitation reaching the soil. This research focuses on soil moisture patterns caused by gaps. The spatio-temporal variability of soil water content is measured in gaps and in surrounding sessile oak (Quercus petraea) forest stand. Soil moisture was determined with manual soil moisture meter which use Time-Domain Reflectometry (TDR) technology. The three different sizes gaps (G1: 10m, G2: 20m, G3: 30m) was opened next to Sopron on the Dalos Hill in Hungary. First, it was determined that there is difference in soil moisture between forest stand and gaps. Second, it was defined that how the gap size influences the soil moisture content. To explore the short term variability of soil moisture, two 24-hour (in growing season) and a 48-hour (in dormant season) field campaign were also performed in case of the medium-sized G2 gap along two/four transects. Subdaily changes of soil moisture were performed. The measured soil moisture pattern was compared with the radiation pattern. It was found that the non-illuminated areas were wetter and in the dormant season the subdaily changes cease. According to our measurements, in the gap there is more available water than under the forest stand due to the less evaporation and interception loss. Acknowledgements: The research was supported by TÁMOP-4.2.2.A-11/1/KONV-2012-0004 and AGRARKLIMA.2 VKSZ_12-1-2013-0034.

Do canopy disturbances drive forest plantations into more natural conditions? — A case study from Can Gio Biosphere Reserve, Viet Nam

NASA Astrophysics Data System (ADS)

Vogt, Juliane; Kautz, Markus; Fontalvo Herazo, Martha Liliana; Triet, Tran; Walther, Denny; Saint-Paul, Ulrich; Diele, Karen; Berger, Uta

2013-11-01

Large areas of mangrove forests were devastated in South Viet Nam during the second Indochina war. After its end in 1975, extensive reforestation with monocultures took place. Can Gio, one of the biggest replanted sites with about 20,000 ha of mangroves mainly Rhizophora apiculata, was declared a biosphere reserve by the UNESCO in 2000. Although this status now enables progressive forest dynamics, there are still drawbacks resulting from the unnatural character of the plantations. For example, the homogeneous size and age structure as well as the regular arrangement of the planted trees make larger forest stands more vulnerable to synchronized collapsing which can be triggered by stronger winds and storms. A transformation into a more natural forest characterized by a heterogeneous age and size structure and a mixed species composition is of urgent need to avoid a synchronized dieback. In this study we test the capability of natural canopy disturbances (e.g. lightning strikes) to facilitate this transformation.Canopy gaps created by lightning strikes were detected and quantified by remote sensing techniques. SPOT satellite images from the years 2003, 2005 and 2007 provided information about the spatial distribution, size, shape, and formation frequency of the gaps. Lightning strike gaps were identified based on their shape and size. They form small openings (mean: 0.025 ha) and their yearly probability of occurrence was determined to be approximately 0.012 per hectare. Selected gaps were surveyed in the field in 2008 to complement the remote sensing data and to provide information upon forest structure and regeneration.Simulation experiments were carried out with the individual-based KiWi mangrove model for quantifying the influence of different lightning regimes on the vertical and horizontal structure of the R. apiculata plantation. In addition, we conducted simulations with a natural and thus randomly generated forest to compare the structure of the two different cultivation types (i.e. plantation and natural forest). The simulation shows that even small disturbances can already partly buffer the risk of cohort senescence of monospecific even-aged plantations. However, after the decline of the plantation, the disturbance regime does not play an important role for further stand development. After the break-up of the initial strongly regular structure of the simulated plantation, a vertical pattern, i.e. height distribution of the trees, similar to the one of the natural forest, emerged quickly. However, the convergence for the horizontal structure i.e. the distance of trees to their nearest neighbor, took twice as long as for the vertical structure. Our results highlight the importance of small disturbances such as lightning strikes to mitigate vulnerability against synchronous windfall in homogenous forest structures. Hence, creating small openings artificially may be an appropriate management measure in areas where the frequency of natural small-scale disturbances is low.

Spatial radiation environment in a heterogeneous oak woodland using a three-dimensional radiative transfer model and multiple constraints from observations

NASA Astrophysics Data System (ADS)

Kobayashi, H.; Ryu, Y.; Ustin, S.; Baldocchi, D. D.

2009-12-01

B15: Remote Characterization of Vegetation Structure: Including Research to Inform the Planned NASA DESDynI and ESA BIOMASS Missions Title: Spatial radiation environment in a heterogeneous oak woodland using a three-dimensional radiative transfer model and multiple constraints from observations Hideki Kobayashi, Youngryel Ryu, Susan Ustin, and Dennis Baldocchi Abstract Accurate evaluations of radiation environments of visible, near infrared, and thermal infrared wavebands in forest canopies are important to estimate energy, water, and carbon fluxes. Californian oak woodlands are sparse and highly clumped so that radiation environments are extremely heterogeneous spatially. The heterogeneity of radiation environments also varies with wavebands which depend on scattering and emission properties. So far, most of modeling studies have been performed in one dimensional radiative transfer models with (or without) clumping effect in the forest canopies. While some studies have been performed by using three dimensional radiative transfer models, several issues are still unresolved. For example, some 3D models calculate the radiation field with individual tree basis, and radiation interactions among trees are not considered. This interaction could be important in the highly scattering waveband such as near infrared. The objective of this study is to quantify the radiation field in the oak woodland. We developed a three dimensional radiative transfer model, which includes the thermal waveband. Soil/canopy energy balances and canopy physiology models, CANOAK, are incorporated in the radiative transfer model to simulate the diurnal patterns of thermal radiation fields and canopy physiology. Airborne LiDAR and canopy gap data measured by the several methods (digital photographs and plant canopy analyzer) were used to constrain the forest structures such as tree positions, crown sizes and leaf area density. Modeling results were tested by a traversing radiometer system that measured incoming photosynthetically active radiation and net radiation at forest floor and spatial variations in canopy reflectances taken by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). In this study, we show how the model with available measurements can reproduce the spatially heterogeneous radiation environments in the oak woodland.

Are temperate mature forests buffered from invasive lianas?

USGS Publications Warehouse

Pavlovic, Noel B.; Leicht-Young, Stacey A.

2011-01-01

Mature and old-growth forests are often thought to be buffered against invasive species due to low levels of light and infrequent disturbance. Lianas (woody vines) and other climbing plants are also known to exhibit lower densities in older forests. As part of a larger survey of the lianas of the southern Lake Michigan region in mature and old-growth forests, the level of infestation by invasive lianas was evaluated. The only invasive liana detected in these surveys was Celastrus orbiculatus Thunb. (Celastraceae). Although this species had only attached to trees and reached the canopy in a few instances, it was present in 30% of transects surveyed, mostly as a component of the ground layer. Transects with C. orbiculatus had higher levels of soil potassium and higher liana richness than transects without. In contrast, transects with the native C. scandens had higher pH, sand content, and soil magnesium and lower organic matter compared to transects where it was absent. Celastrus orbiculatus appears to be a generalist liana since it often occurs with native lianas. Celastrus orbiculatus poses a substantial threat to mature forests as it will persist in the understory until a canopy gap or other disturbance provides the light and supports necessary for it to ascend to the canopy and damage tree species. As a result, these forests should be monitored by land managers so that C. orbiculatus eradication can occur while invasions are at low densities and restricted to the ground layer.

Logging disturbance shifts net primary productivity and its allocation in Bornean tropical forests.

PubMed

Riutta, Terhi; Malhi, Yadvinder; Kho, Lip Khoon; Marthews, Toby R; Huaraca Huasco, Walter; Khoo, MinSheng; Tan, Sylvester; Turner, Edgar; Reynolds, Glen; Both, Sabine; Burslem, David F R P; Teh, Yit Arn; Vairappan, Charles S; Majalap, Noreen; Ewers, Robert M

2018-01-24

Tropical forests play a major role in the carbon cycle of the terrestrial biosphere. Recent field studies have provided detailed descriptions of the carbon cycle of mature tropical forests, but logged or secondary forests have received much less attention. Here, we report the first measures of total net primary productivity (NPP) and its allocation along a disturbance gradient from old-growth forests to moderately and heavily logged forests in Malaysian Borneo. We measured the main NPP components (woody, fine root and canopy NPP) in old-growth (n = 6) and logged (n = 5) 1 ha forest plots. Overall, the total NPP did not differ between old-growth and logged forest (13.5 ± 0.5 and 15.7 ± 1.5 Mg C ha -1  year -1 respectively). However, logged forests allocated significantly higher fraction into woody NPP at the expense of the canopy NPP (42% and 48% into woody and canopy NPP, respectively, in old-growth forest vs 66% and 23% in logged forest). When controlling for local stand structure, NPP in logged forest stands was 41% higher, and woody NPP was 150% higher than in old-growth stands with similar basal area, but this was offset by structure effects (higher gap frequency and absence of large trees in logged forest). This pattern was not driven by species turnover: the average woody NPP of all species groups within logged forest (pioneers, nonpioneers, species unique to logged plots and species shared with old-growth plots) was similar. Hence, below a threshold of very heavy disturbance, logged forests can exhibit higher NPP and higher allocation to wood; such shifts in carbon cycling persist for decades after the logging event. Given that the majority of tropical forest biome has experienced some degree of logging, our results demonstrate that logging can cause substantial shifts in carbon production and allocation in tropical forests. © 2018 John Wiley & Sons Ltd.

Large off-nadir scan angle of airborne LiDAR can severely affect the estimates of forest structure metrics

NASA Astrophysics Data System (ADS)

Liu, Jing; Skidmore, Andrew K.; Jones, Simon; Wang, Tiejun; Heurich, Marco; Zhu, Xi; Shi, Yifang

2018-02-01

Gap fraction (Pgap) and vertical gap fraction profile (vertical Pgap profile) are important forest structural metrics. Accurate estimation of Pgap and vertical Pgap profile is therefore critical for many ecological applications, including leaf area index (LAI) mapping, LAI profile estimation and wildlife habitat modelling. Although many studies estimated Pgap and vertical Pgap profile from airborne LiDAR data, the scan angle was often overlooked and a nadir view assumed. However, the scan angle can be off-nadir and highly variable in the same flight strip or across different flight strips. In this research, the impact of off-nadir scan angle on Pgap and vertical Pgap profile was evaluated, for several forest types. Airborne LiDAR data from nadir (0°∼7°), small off-nadir (7°∼23°), and large off-nadir (23°∼38°) directions were used to calculate both Pgap and vertical Pgap profile. Digital hemispherical photographs (DHP) acquired during fieldwork were used as references for validation. Our results show that angular Pgap from airborne LiDAR correlates well with angular Pgap from DHP (R2 = 0.74, 0.87, and 0.67 for nadir, small off-nadir and large off-nadir direction). But underestimation of Pgap from LiDAR amplifies at large off-nadir scan angle. By comparing Pgap and vertical Pgap profiles retrieved from different directions, it is shown that scan angle impact on Pgap and vertical Pgap profile differs amongst different forest types. The difference is likely to be caused by different leaf angle distribution and canopy architecture in these forest types. Statistical results demonstrate that the scan angle impact is more severe for plots with discontinuous or sparse canopies. These include coniferous plots, and deciduous or mixed plots with between-crown gaps. In these discontinuous plots, Pgap and vertical Pgap profiles are maximum when observed from nadir direction, and then rapidly decrease with increasing scan angle. The results of this research have many important practical implications. First, it is suggested that large off-nadir scan angle of airborne LiDAR should be avoided to ensure a more accurate Pgap and LAI estimation. Second, the angular dependence of vertical Pgap profiles observed from airborne LiDAR should be accounted for, in order to improve the retrieval of LAI profiles, and other quantitative canopy structural metrics. This is especially necessary when using multi-temporal datasets in discontinuous forest types. Third, the anisotropy of Pgap and vertical Pgap profile observed by airborne LiDAR, can potentially help to resolve the anisotropic behavior of canopy reflectance, and refine the inversion of biophysical and biochemical properties from passive multispectral or hyperspectral data.

Landscape-scale forest disturbance regimes in southern Peruvian Amazonia.

PubMed

Boyd, Doreen S; Hill, Ross A; Hopkinson, Chris; Baker, Timothy R

2013-10-01

Landscape-scale gap-size frequency distributions in tropical forests are a poorly studied but key ecological variable. Currently, a scale gap currently exists between local-scale field-based studies and those employing regional-scale medium-resolution satellite data. Data at landscape scales but of fine resolution would, however, facilitate investigation into a range of ecological questions relating to gap dynamics. These include whether canopy disturbances captured in permanent sample plots (PSPs) are representative of those in their surrounding landscape, and whether disturbance regimes vary with forest type. Here, therefore, we employ airborne LiDAR data captured over 142.5 km2 of mature, swamp, and regenerating forests in southeast Peru to assess the landscape-scale disturbance at a sampling resolution of up to 2 m. We find that this landscape is characterized by large numbers of small gaps; large disturbance events are insignificant and infrequent. Of the total number of gaps that are 2 m2 or larger in area, just 0.45% were larger than 100 m2, with a power-law exponent (alpha) value of the gap-size frequency distribution of 2.22. However, differences in disturbance regimes are seen among different forest types, with a significant difference in the alpha value of the gap-size frequency distribution observed for the swamp/regenerating forests compared with the mature forests at higher elevations. Although a relatively small area of the total forest of this region was investigated here, this study presents an unprecedented assessment of this landscape with respect to its gap dynamics. This is particularly pertinent given the range of forest types present in the landscape and the differences observed. The coupling of detailed insights into forest properties and growth provided by PSPs with the broader statistics of disturbance events using remote sensing is recommended as a strong basis for scaling-up estimates of landscape and regional-scale carbon balance.

Not so hot: Rapid recovery of soil temperature and respiration following tornado damage, regardless of disturbance severity

NASA Astrophysics Data System (ADS)

Nagendra, U.; Peterson, C.

2013-12-01

Forest disturbances such as tornadoes are expected to raise soil temperatures and increase soil respiration. Opening canopy gaps allows solar radiation to heat the forest floor, and damaged plant roots provide fuel for decomposition. Patches of disturbed forest can range from low severity (some defoliation, broken branches) to high severity (uprooted or snapped trees). Disturbance severity affects plant population and community processes, such as regeneration mode, species diversity, and community structure. We expect disturbance severity to also affect ecosystem processes such as soil respiration. Severe disturbances cause more distinct, and often larger, canopy gaps than mild disturbances, and damage more standing biomass, both above- and below-ground. We would expect these larger gaps and greater litter amounts to increase soil temperature and respiration in more severely disturbed forest patches. In April 2011, a moderate (EF-3) tornado damaged portions of the Chattahoochee National Forest in NE Georgia, USA. Our lab has been characterizing the damage and regeneration in sections of the forest since summer 2011. In Spring 2013, we installed 4 iButton temperature sensors in each of 14 plots across a range of disturbance severity (for a total of 56 sensors). Severity was determined by percent of initial tree basal area downed by the tornado, and ranged from 8% to 100% basal area down. The iButtons monitored soil temperature at a depth of 5 cm every hour for 85 days. In July 2013, integrated 24-hour soil respiration was measured at the same locations using soda lime absorption in sealed PVC collars. Soil temperature at 5 cm averaged 12.66 °C. Contrary to expectations, average daily temperatures did not increase with greater plot damage severity (R2 = 0.001). Daily variation was only slightly higher in plots of very high severity. Overall, soil temperatures appeared to have returned to pre-disturbance temperatures more quickly than expected. Results for upcoming months will be presented at the meeting. Soil respiration was relatively high in all plots (4.49 +/-1.19 g C m-2 hr-1). Contrary to expectations, respiration did not vary significantly with plot damage severity (R2 = 0.0676). The temperature and respiration data together suggest potentially rapid ecosystem recovery after these types of wind disturbances. The flush of understory growth in open patches may insulate the forest floor from solar radiation, even though the forest canopy is still open. These unexpected preliminary results may indicate that ecosystem processes in southern forests are more resilient to disturbances than previously thought. Although forests become carbon sinks immediately after disturbances, they may return to carbon neutral or sink status relatively quickly, given the right circumstances.

Food abundance does not determine bird use of early-successional habitat

Treesearch

Tracey B. Champlin; John C. Kilgo; Christopher E. Moorman

2009-01-01

Few attempts have been made to experimentally address the extent to which temporal or spatial variation in food availability influences avian habitat use. We used an experimental approach to investigate whether bird use differed between treated (arthropods reduced through insecticide application) and control (untreated) forest canopy gaps within a bottomland hardwood...

Canopy gap dynamics of second-growth red spruce-northern hardwood stands in West Virginia

Treesearch

James S. Rentch; Thomas M. Schuler; Gregory J. Nowacki; Nathan R. Beane; W. Mark Ford

2010-01-01

Forest restoration requires an understanding of the natural disturbance regime of the target community and estimates of the historic range of variability of ecosystem components (composition, structure, and disturbance processes). Management prescriptions that support specific restoration activities should be consistent with these parameters. In this study, we describe...

An examination of fire spread thresholds in discontinuous fuel beds

Treesearch

Mark A. Finney; Jack D. Cohen; Isaac C. Grenfell; Kara M. Yedinak

2010-01-01

Many fuel beds, especially live vegetation canopies (conifer forests, shrub fields, bunch-grasses) contain gaps between vegetation clumps. Fires burning in these fuel types often display thresholds for spread that are observed to depend on environmental factors like wind, slope, and fuel moisture content. To investigate threshold spread behaviours, we conducted a set...

Throughfall and stemflow dynamics in a riparian cedar swamp: possible ecohydrological feedbacks

NASA Astrophysics Data System (ADS)

Duval, T. P.

2012-12-01

Partitioning of rainfall through forest canopies as throughfall and stemflow have deservedly been the subject of much research in the past; however, very little is known about the fluxes of water and solutes through forested wetland communities. Temperate swamps are characterized by intermittent canopy coverage, with areas that are denser than upland forests of similar species, but also contain canopy gaps of meadow and marsh communities,. Understanding the role of vegetation on the distribution of precipitation in these ecosystems is necessary to effectively constrain water balance estimates and predict possible community responses to shifting climate regimes. This study examines throughfall, stemflow, and interception dynamics in a riparian cedar swamp in Alliston, Ontario, Canada over the 2012 growing season. Throughfall averaged 76 % of above-canopy rainfall; however, there were spatial-magnitude interaction variations within the swamp. For events less than 20 mm, between 17 and 75 % of the measured swamp floor received greater depth of rain than above the canopy, whereas for events greater than 20 mm only between 2 and 23 % of the sampled swamp floor received more water than the actual event. The observed spatial variability in throughfall was not related to leaf area index, suggesting remote sensing modelling efforts may not be an accurate method for quantification of wetland precipitation dynamics. Stemflow along the predominantly cedar trees averaged 5 %; therefore, net precipitation on a seasonal basis in this cedar swamp was 81 % of above canopy rainfall. Throughfall DOC and total nitrogen concentrations averaged 31 and 2.2 mg/L, respectively, with stemflow DOC and TN concentrations averaging 109 and 6.5 mg/L, respectively. These values are much higher than reported for upland forest species. In general, throughfall magnitudes increased and solute concentrations decreased with increasing distance from the existing forest boles. The delivery of high reactive-solute concentrations through stemflow and comparatively reduced throughfall water fluxes closer to the trees may represent an ecohydrological feedback to cedar maintenance in swamp ecosystems by enriching the root zone soil with nutrients and shedding water away from the roots in a system where the presence of water is viewed as a stress to optimal growth.

Canopy structural complexity influences forest canopy reflectance: linking terrestrial lidar with Landsat observations

NASA Astrophysics Data System (ADS)

Hardiman, B. S.; Atkins, J.; Dahlin, K.; Fahey, R. T.; Gough, C. M.

2016-12-01

Canopy physical structure - leaf quantity and arrangement - strongly affects light interception and distribution. As such, canopy physical structure is a key driver of forest carbon (C) dynamics. Terrestrial lidar systems (TLS) provide spatially explicit, quantitative characterizations of canopy physical structure at scales commensurate with plot-scale C cycling processes. As an example, previous TLS-based studies established that light use efficiency is positively correlated with canopy physical structure, influencing the trajectory of net primary production throughout forest development. Linking TLS measurements of canopy structure to multispectral satellite observations of forest canopies may enable scaling of ecosystem C cycling processes from leaves to continents. We will report on our study relating a suite of canopy structural metrics to well-established remotely sensed measurements (NDVI, EVI, albedo, tasseled cap indices, etc.) which are indicative of important forest characteristics (leaf area, canopy nitrogen, light interception, etc.). We used Landsat data, which provides observations at 30m resolution, a scale comparable to that of TLS. TLS data were acquired during 2009-2016 from forest sites throughout Eastern North America, comprised primarily of NEON and Ameriflux sites. Canopy physical structure data were compared with contemporaneous growing-season Landsat data. Metrics of canopy physical structure are expected to covary with forest composition and dominant PFT, likely influencing interaction strength between TLS and Landsat canopy metrics. More structurally complex canopies (those with more heterogeneous distributions of leaf area) are expected to have lower albedo, suggesting greater canopy light absorption (higher fAPAR) than simpler canopies. We expect that vegetation indices (NDVI, EVI) will increase with TLS metrics of spatial heterogeneity, and not simply quantity, of leaves, supporting our hypothesis that canopy light absorption is dependent on both leaf quantity and arrangement. Relating satellite observations of canopy properties to TLS metrics of canopy physical structure represents an important advance for modelling canopy energy balance and forest C cycling processes at large spatial scales.

Herpetofaunal Response to Gap and Skidder-Rut Wetland Creation in a Southern Bottomland Hardwood Forest.

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

Cromer R.B.; Lanham J.D.; Hanlin H.H.

2002-05-01

Herpetofaunal Response to Gap and Skidder-Rut Wetland Creation in a Southern Bottomland Hardwood Forest. Cromer R.B., J.D.Lanham, and H.H. Hanlin.Forest Science, 1 May 2002, vol. 48, iss. 2, pp. 407-413(7) We compared herpetofaunal communities in recently harvested gaps, skidder trails, and unharvested depressional wetlands to assess the effects of group-selection harvesting and skidder traffic on reptiles and amphibians in a southern bottomland hardwood forest. From January 1, 1997 to December 31, 1998 we captured 24,292 individuals representing 55 species of reptiles and amphibians at the Savannah River Site in Barnwell County, South Carolina. Forty-two species (n = 6,702 individuals) weremore » captured in gaps, 43 species (n = 8,863 individuals) were captured along skid trails between gaps and 43 species (n = 8,727 individuals) were captured in bottomland depressions over the 2 yr period. Three vegetation variables and six environmental variables were correlated with herpetofaunal abundance. Salamander abundance, especially for species in the genus Ambystoma, was negatively associated with areas with less canopy cover and pronounced rutting (i.e., gaps and skidder trails). Alternatively, treefrog (Hylidae) abundance was positively associated with gap creation. Results from this study suggest that group selection harvests and skidder rutting may alter the herpetofaunal species composition in southern bottomland hardwoods by increasing habitat suitability for some species while diminishing it for others.« less

SAR backscatter from coniferous forest gaps

NASA Technical Reports Server (NTRS)

Day, John L.; Davis, Frank W.

1992-01-01

A study is in progress comparing Airborne Synthetic Aperture Radar (AIRSAR) backscatter from coniferous forest plots containing gaps to backscatter from adjacent gap-free plots. Issues discussed are how do gaps in the range of 400 to 1600 sq m (approximately 4-14 pixels at intermediate incidence angles) affect forest backscatter statistics and what incidence angles, wavelengths, and polarizations are most sensitive to forest gaps. In order to visualize the slant-range imaging of forest and gaps, a simple conceptual model is used. This strictly qualitative model has led us to hypothesize that forest radar returns at short wavelengths (eg., C-band) and large incidence angles (e.g., 50 deg) should be most affected by the presence of gaps, whereas returns at long wavelengths and small angles should be least affected. Preliminary analysis of 1989 AIRSAR data from forest near Mt. Shasta supports the hypothesis. Current forest backscatter models such as MIMICS and Santa Barbara Discontinuous Canopy Backscatter Model have in several cases correctly predicted backscatter from forest stands based on inputs of measured or estimated forest parameters. These models do not, however, predict within-stand SAR scene texture, or 'intrinsic scene variability' as Ulaby et al. has referred to it. For instance, the Santa Barbara model, which may be the most spatially coupled of the existing models, is not truly spatial. Tree locations within a simulated pixel are distributed according to a Poisson process, as they are in many natural forests, but tree size is unrelated to location, which is not the case in nature. Furthermore, since pixels of a simulated stand are generated independently in the Santa Barbara model, spatial processes larger than one pixel are not modeled. Using a different approach, Oliver modeled scene texture based on an hypothetical forest geometry. His simulated scenes do not agree well with SAR data, perhaps due to the simple geometric model used. Insofar as texture is the expression of biological forest processes, such as succession and disease, and physical ones, such as fire and wind-throw, it contains useful information about the forest, and has value in image interpretation and classification. Forest gaps are undoubtedly important contributors to scene variance. By studying the localized effects of gaps on forest backscatter, guided by our qualitative model, we hope to understand more clearly the manner in which spatial heterogeneities in forests produce variations in backscatter, which collectively give rise to scene texture.

Plant canopy gap-size analysis theory for improving optical measurements of leaf-area index

NASA Astrophysics Data System (ADS)

Chen, Jing M.; Cihlar, Josef

1995-09-01

Optical instruments currently available for measuring the leaf-area index (LAI) of a plant canopy all utilize only the canopy gap-fraction information. These instruments include the Li-Cor LAI-2000 Plant Canopy Analyzer, Decagon, and Demon. The advantages of utilizing both the canopy gap-fraction and gap-size information are shown. For the purpose of measuring the canopy gap size, a prototype sunfleck-LAI instrument named Tracing Radiation and Architecture of Canopies (TRAC), has been developed and tested in two pure conifer plantations, red pine (Pinus resinosa Ait.) and jack pine (Pinus banksiana Lamb). A new gap-size-analysis theory is presented to quantify the effect of canopy architecture on optical measurements of LAI based on the gap-fraction principle. The theory is an improvement on that of Lang and Xiang [Agric. For. Meteorol. 37, 229 (1986)]. In principle, this theory can be used for any heterogeneous canopies.

[Estimation of forest canopy chlorophyll content based on PROSPECT and SAIL models].

PubMed

Yang, Xi-guang; Fan, Wen-yi; Yu, Ying

2010-11-01

The forest canopy chlorophyll content directly reflects the health and stress of forest. The accurate estimation of the forest canopy chlorophyll content is a significant foundation for researching forest ecosystem cycle models. In the present paper, the inversion of the forest canopy chlorophyll content was based on PROSPECT and SAIL models from the physical mechanism angle. First, leaf spectrum and canopy spectrum were simulated by PROSPECT and SAIL models respectively. And leaf chlorophyll content look-up-table was established for leaf chlorophyll content retrieval. Then leaf chlorophyll content was converted into canopy chlorophyll content by Leaf Area Index (LAD). Finally, canopy chlorophyll content was estimated from Hyperion image. The results indicated that the main effect bands of chlorophyll content were 400-900 nm, the simulation of leaf and canopy spectrum by PROSPECT and SAIL models fit better with the measured spectrum with 7.06% and 16.49% relative error respectively, the RMSE of LAI inversion was 0. 542 6 and the forest canopy chlorophyll content was estimated better by PROSPECT and SAIL models with precision = 77.02%.

Global patterns and determinants of forest canopy height.

PubMed

Tao, Shengli; Guo, Qinghua; Li, Chao; Wang, Zhiheng; Fang, Jingyun

2016-12-01

Forest canopy height is an important indicator of forest biomass, species diversity, and other ecosystem functions; however, the climatic determinants that underlie its global patterns have not been fully explored. Using satellite LiDAR-derived forest canopy heights and field measurements of the world's giant trees, combined with climate indices, we evaluated the global patterns and determinants of forest canopy height. The mean canopy height was highest in tropical regions, but tall forests (>50 m) occur at various latitudes. Water availability, quantified by the difference between annual precipitation and annual potential evapotranspiration (P-PET), was the best predictor of global forest canopy height, which supports the hydraulic limitation hypothesis. However, in striking contrast with previous studies, the canopy height exhibited a hump-shaped curve along a gradient of P-PET: it initially increased, then peaked at approximately 680 mm of P-PET, and finally declined, which suggests that excessive water supply negatively affects the canopy height. This trend held true across continents and forest types, and it was also validated using forest inventory data from China and the United States. Our findings provide new insights into the climatic controls of the world's giant trees and have important implications for forest management and improvement of forest growth models. © 2016 by the Ecological Society of America.

A Black Swan and Sub-continental Scale Dynamics in Humid, Late-Holocene Broadleaf Forests

NASA Astrophysics Data System (ADS)

Pederson, N.; Dyer, J.; McEwan, R.; Hessl, A. E.; Mock, C. J.; Orwig, D.; Rieder, H. E.; Cook, B. I.

2012-12-01

In humid regions with dense broadleaf-dominated forests where gap-dynamics is the prevailing disturbance regime, paleoecological evidence shows regional-scale changes in forest composition associated with climatic change. To investigate the potential for regional events in late-Holocene forests, we use tree-ring data from 76 populations covering 840,000 km2 and 5.3k tree recruitment dates spanning 1.4 million km2 in the eastern US to investigate the occurrence of simultaneous forest dynamics across a humid region. We compare regional forest dynamics with an independent set of annually-resolved tree ring record of hydroclimate to examine whether climate dynamics might drive forest dynamics in this humid region. In forests where light availability is an important limitation for tree recruitment, we document a pulse of tree recruitment during the mid- to late-1600s across the eastern US. This pulse, which can be inferred as large-scale canopy opening, occurred during an era that multiple proxies indicate as extended drought between two intense pluvial. Principal component analysis of the 76 populations indicates a step-change increase in average ring width during the late-1770s resembling a potential canopy accession event over 42,800 km2 of the southeastern US. Growth-release analysis of populations loading strongly on this eigenvector indicates severe canopy disturbance from 1775-1779 that peaked in 1776. The 1776 event follows a period with extended droughts and severe large-scale frost event. We hypothesize these climatic events lead to elevated tree mortality in the late-1770s and canopy accession for understory trees. Superposed epoch analysis reveals that spikes of elevated canopy disturbance from 1685-1850 CE are significantly associated with drought. Extreme value theory statistics indicates the 1776 event lies beyond the 99.9 quantile and nearly 7 sigmas above the 1685-1850 mean rate of disturbance. The time-series of canopy disturbance from 1685-1850 is so poorly described by a Gaussian distribution that it can be considered 'heavy tailed'. Preliminary results show that disturbance events that affect >3-5% of the trees in our dataset occur approximately every 200 years. The most extreme rates (>5%) occur approximately every 500-1000 years. These statistics indicate that the 1775-1779 heavy-tail event can also be considered a 'Black Swan', the rare event that has the potential to alter a system's trajectory further than common events. Our results challenge traditional views regarding characteristic disturbance regime in humid temperate forests, and speak to the importance of punctuated climatic events in shaping forest structure for centuries. Such an understanding is critical given the potential of more frequent extreme climatic events in the future.

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...

Upscaling of Solar Induced Chlorophyll Fluorescence from Leaf to Canopy Using the Dart Model and a Realistic 3d Forest Scene

NASA Astrophysics Data System (ADS)

Liu, W.; Atherton, J.; Mõttus, M.; MacArthur, A.; Teemu, H.; Maseyk, K.; Robinson, I.; Honkavaara, E.; Porcar-Castell, A.

2017-10-01

Solar induced chlorophyll a fluorescence (SIF) has been shown to be an excellent proxy of photosynthesis at multiple scales. However, the mechanical linkages between fluorescence and photosynthesis at the leaf level cannot be directly applied at canopy or field scales, as the larger scale SIF emission depends on canopy structure. This is especially true for the forest canopies characterized by high horizontal and vertical heterogeneity. While most of the current studies on SIF radiative transfer in plant canopies are based on the assumption of a homogeneous canopy, recently codes have been developed capable of simulation of fluorescence signal in explicit 3-D forest canopies. Here we present a canopy SIF upscaling method consisting of the integration of the 3-D radiative transfer model DART and a 3-D object model BLENDER. Our aim was to better understand the effect of boreal forest canopy structure on SIF for a spatially explicit forest canopy.

Coming down from the trees: Is terrestrial activity in Bornean orangutans natural or disturbance driven?

PubMed Central

Ancrenaz, Marc; Sollmann, Rahel; Meijaard, Erik; Hearn, Andrew J.; Ross, Joanna; Samejima, Hiromitsu; Loken, Brent; Cheyne, Susan M.; Stark, Danica J.; Gardner, Penny C.; Goossens, Benoit; Mohamed, Azlan; Bohm, Torsten; Matsuda, Ikki; Nakabayasi, Miyabi; Lee, Shan Khee; Bernard, Henry; Brodie, Jedediah; Wich, Serge; Fredriksson, Gabriella; Hanya, Goro; Harrison, Mark E.; Kanamori, Tomoko; Kretzschmar, Petra; Macdonald, David W.; Riger, Peter; Spehar, Stephanie; Ambu, Laurentius N.; Wilting, Andreas

2014-01-01

The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated. PMID:24526001

Forest biomass, canopy structure, and species composition relationships with multipolarization L-band synthetic aperture radar data

NASA Technical Reports Server (NTRS)

Sader, Steven A.

1987-01-01

The effect of forest biomass, canopy structure, and species composition on L-band synthetic aperature radar data at 44 southern Mississippi bottomland hardwood and pine-hardwood forest sites was investigated. Cross-polarization mean digital values for pine forests were significantly correlated with green weight biomass and stand structure. Multiple linear regression with five forest structure variables provided a better integrated measure of canopy roughness and produced highly significant correlation coefficients for hardwood forests using HV/VV ratio only. Differences in biomass levels and canopy structure, including branching patterns and vertical canopy stratification, were important sources of volume scatter affecting multipolarization radar data. Standardized correction techniques and calibration of aircraft data, in addition to development of canopy models, are recommended for future investigations of forest biomass and structure using synthetic aperture radar.

ForestCrowns: a software tool for analyzing ground-based digital photographs of forest canopies

Treesearch

Matthew F. Winn; Sang-Mook Lee; Phillip A. Araman

2013-01-01

Canopy coverage is a key variable used to characterize forest structure. In addition, the light transmitted through the canopy is an important ecological indicator of plant and animal habitat and understory climate conditions. A common ground-based method used to document canopy coverage is to take digital photographs from below the canopy. To assist with analyzing...

ForestCrowns: a transparency estimation tool for digital photographs of forest canopies

Treesearch

Matthew Winn; Jeff Palmer; S.-M. Lee; Philip Araman

2016-01-01

ForestCrowns is a Windows®-based computer program that calculates forest canopy transparency (light transmittance) using ground-based digital photographs taken with standard or hemispherical camera lenses. The software can be used by forest managers and researchers to monitor growth/decline of forest canopies; provide input for leaf area index estimation; measure light...

In search of radiation minima for balancing the needs of forest and water management in snow dominated watersheds (Invited)

NASA Astrophysics Data System (ADS)

Kumar, M.; Seyednasrollah, B.; Link, T. E.

2013-12-01

In upland snowfed forested watersheds, where the majority of melt recharge occurs, there is growing interest among water and forest managers to strike a balance between maximizing forest productivity and minimizing impacts on water resources. Implementation of forest management strategies that involve reduction of forest cover generally result in increased water yield and peak flows from forests, which has potentially detrimental consequences including increased erosion, stream destabilization, water shortages in late melt season, and degradation of water quality and ecosystem health. These ill effects can be partially negated by implementing optimal gap patterns and vegetation densities through forest management, that may minimize net radiation on snow-covered forest floor (NRSF). A small NRSF can moderate peak flows and increase water availability late in the melt season. Since forest canopies reduce direct solar (0.28 - 3.5 μm) radiation but increase longwave (3.5-100 μm) radiation at the snow surface, by performing detailed quantification of individual radiation components for a range of vegetation density and and gap configurations, we identify the optimal vegetation configurations. We also evaluate the role of site location, its topographic setting, local meteorological conditions and vegetation morphological characteristics, on the optimal configurations. The results can be used to assist forest managers to quantify the radiative regime alteration for various thinning and gap-creation scenarios, as a function of latitudinal, topographic, climatic and vegetation characteristics.

Fire-induced changes in boreal forest canopy volume and soil organic matter from multi-temporal airborne lidar

NASA Astrophysics Data System (ADS)

Alonzo, M.; Cook, B.; Andersen, H. E.; Babcock, C. R.; Morton, D. C.

2016-12-01

Fire in boreal forests initiates a cascade of biogeochemical and biophysical processes. Over typical fire return intervals, net radiative forcing from boreal forest fires depends on the offsetting impacts of greenhouse gas emissions and post-fire changes in land surface albedo. Whether boreal forest fires warm or cool the climate over these multi-decadal intervals depends on the magnitude of fire emissions and the time scales of decomposition, albedo changes, and forest regrowth. Our understanding of vegetation and surface organic matter (SOM) changes from boreal forest fires is shaped by field measurements and moderate resolution remote sensing data. Intensive field plot measurements offer detailed data on overstory, understory, and SOM changes from fire, but sparse plot data can be difficult to extend across the heterogeneous boreal forest landscape. Conversely, satellite measurements of burn severity are spatially extensive but only provide proxy measures of fire effects. In this research, we seek to bridge the scale gap between existing intensive and extensive methods using a combination of airborne lidar data and time series of Landsat data to evaluate pre- and post-fire conditions across Alaska's Kenai Peninsula. Lidar-based estimates of pre-fire stand structure and composition were essential to characterize the loss of canopy volume from fires between 2001 and 2014, quantify transitions from live to dead standing carbon pools, and isolate vegetation recovery following fire over 1 to 13 year time scales. Results from this study demonstrate the utility of lidar for estimating pre-fire structure and species composition at the scale of individual tree crowns. Multi-temporal airborne lidar data also provide essential insights regarding the heterogeneity of canopy and SOM losses at a sub-Landsat pixel scale. Fire effects are forest-structure and species dependent with variable temporal lags in carbon release due to delayed mortality (>5 years post fire) and standing dead trees. Establishing the spatial and temporal scales of canopy structural change will aid in constraining estimates of net radiative forcing from both carbon release and albedo in the years following fire.

Forest-climate interactions in fragmented tropical landscapes.

PubMed

Laurance, William F

2004-03-29

In the tropics, habitat fragmentation alters forest-climate interactions in diverse ways. On a local scale (less than 1 km), elevated desiccation and wind disturbance near fragment margins lead to sharply increased tree mortality, thus altering canopy-gap dynamics, plant community composition, biomass dynamics and carbon storage. Fragmented forests are also highly vulnerable to edge-related fires, especially in regions with periodic droughts or strong dry seasons. At landscape to regional scales (10-1000 km), habitat fragmentation may have complex effects on forest-climate interactions, with important consequences for atmospheric circulation, water cycling and precipitation. Positive feedbacks among deforestation, regional climate change and fire could pose a serious threat for some tropical forests, but the details of such interactions are poorly understood.

Spatial and Temporal Habitat Use of an Asian Elephant in Sumatra

PubMed Central

Sitompul, Arnold F.; Griffin, Curtice R.; Rayl, Nathaniel D.; Fuller, Todd K.

2013-01-01

Simple Summary A wild Sumatran elephant radio-monitored near a conservation center from August 2007–May 2008 used medium- and open-canopy land cover more than expected, but closed canopy forests were used more during the day than at night. When in closed canopy forests, elephants spent more time near the forest edge. Effective elephant conservation strategies in Sumatra need to focus on forest restoration of cleared areas and providing a forest matrix that includes various canopy types. Abstract Increasingly, habitat fragmentation caused by agricultural and human development has forced Sumatran elephants into relatively small areas, but there is little information on how elephants use these areas and thus, how habitats can be managed to sustain elephants in the future. Using a Global Positioning System (GPS) collar and a land cover map developed from TM imagery, we identified the habitats used by a wild adult female elephant (Elephas maximus sumatranus) in the Seblat Elephant Conservation Center, Bengkulu Province, Sumatra during 2007–2008. The marked elephant (and presumably her 40–60 herd mates) used a home range that contained more than expected medium canopy and open canopy land cover. Further, within the home range, closed canopy forests were used more during the day than at night. When elephants were in closed canopy forests they were most often near the forest edge vs. in the forest interior. Effective elephant conservation strategies in Sumatra need to focus on forest restoration of cleared areas and providing a forest matrix that includes various canopy types. PMID:26479527

Forest canopy temperatures: dynamics, controls, and relationships with ecosystem fluxes

NASA Astrophysics Data System (ADS)

Still, C. J.; Griffith, D.; Kim, Y.; Law, B. E.; Hanson, C. V.; Kwon, H.; Schulze, M.; Detto, M.; Pau, S.

2017-12-01

Temperature strongly affects enzymatic reactions, ecosystem biogeochemistry, and species distributions. Although most focus is on air temperature, the radiative or skin temperature of plants is more relevant. Canopy skin temperature dynamics reflect biophysical, physiological, and anatomical characteristics and interactions with the environment, and can be used to examine forest responses to stresses like droughts and heat waves. Thermal infrared (TIR) imaging allows for extensive temporal and spatial sampling of canopy temperatures, particularly compared to spot measurements using thermocouples. We present results of TIR imaging of forest canopies at eddy covariance flux tower sites in the US Pacific Northwest and in Panama. These forests range from an old-growth temperate rainforest to a second growth semi-arid pine forest to a semi-deciduous tropical forest. Canopy temperature regimes at these sites are highly variable. Canopy temperatures at all forest sites displayed frequent departures from air temperature, particularly during clear sky conditions, with elevated canopy temperatures during the day and depressed canopy temperatures at night compared to air temperature. Comparison of canopy temperatures to fluxes of carbon dioxide, water vapor, and energy reveals stronger relationships than those found with air temperature. Daytime growing season net ecosystem exchange at the pine forest site is better explained by canopy temperature (r2 = 0.61) than air temperature (r2 = 0.52). At the semi-deciduous tropical forest, canopy photosynthesis is highly correlated with canopy temperature (r2 = 0.51), with a distinct optimum temperature for photosynthesis ( 31 °C) that agrees with leaf-level measurements. During the peak of one heat wave at an old-growth temperate rainforest, hourly averaged air temperature exceeded 35 °C, 10 °C above average. Peak hourly canopy temperature approached 40 °C, and leaf-to-air vapor pressure deficit exceeded 6 kPa. These extreme conditions had a dramatic effect on forest carbon and energy exchanges: the canopy switched from daytime net carbon uptake prior to the heatwave to net carbon release during and immediately after the heat wave. The latent heat flux from evapotranspiration increased during the heat wave, while sensible heat fluxes were lower.

Quantifying widespread canopy cover decline through the course of a beetle kill epidemic in Colorado with remote sensing of snow

NASA Astrophysics Data System (ADS)

Baker, E. H.; Raleigh, M. S.; Molotch, N. P.

2014-12-01

Since the mid-1990s, outbreaks of aggressive bark beetle species have caused extensive forest morality across 600,000 km2 of North-American forests, killing over 17,800 km2 of forest in Colorado alone. This mortality has resulted in a widespread, spatially heterogeneous decline of forest canopies, which in turn exerts strong controls on the accumulation and melt of the snowpack. In the Western United States, where approximately 70-80% of total annual runoff originates as mountain snowmelt, it is important to monitor and quantify changes in forest canopy in snow-dominated catchments. To quantify annual values of forest canopy cover, this research develops a metric from time series of daily fractional snow covered area (FSCA) from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) snow covered area and grain size (MODSCAG) algorithm. In areas where soil and rock are completely snow-covered, a land pixel is composed only of forest canopy and snow. Following a snowfall event, FSCA initially rises rapidly, as snow is intercepted in the canopy, and then declines, as snow unloads from the canopy. The lower of these local minima form a threshold representative of snow-free canopy conditions, which serves as a spatially explicit metric of forest canopy. Investigation of a site in southern Colorado with over 40% spruce beetle mortality shows a statistically significant decrease of canopy cover, from 76 (±4)% pre-infestation to 55 (±8)% post-infestation (t=-5.1, p<0.01). Additionally, this yearly parameterization of forest canopy is well correlated (ρ=0.76, p<0.01) with an independent product of yearly crown mortality derived from U.S. Forest Service Aerial Detection Surveys. Future work will examine this relationship across varied ecologic settings and geographic locations, and incorporate field measurements of species-specific canopy change after beetle kill.

Spatial and Temporal Variabilities of Solar and Longwave Radiation Fluxes below a Coniferous Forest in the French Alps

NASA Astrophysics Data System (ADS)

Sicart, J. E.; Ramseyer, V.; Lejeune, Y.; Essery, R.; Webster, C.; Rutter, N.

2017-12-01

At high altitudes and latitudes, snow has a large influence on hydrological processes. Large fractions of these regions are covered by forests, which have a strong influence on snow accumulation and melting processes. Trees absorb a large part of the incoming shortwave radiation and this heat load is mostly dissipated as longwave radiation. Trees shelter the snow surface from wind, so sub-canopy snowmelt depends mainly on the radiative fluxes: vegetation attenuates the transmission of shortwave radiation but enhances longwave irradiance to the surface. An array of 13 pyranometers and 11 pyrgeometers was deployed on the snow surface below a coniferous forest at the CEN-MeteoFrance Col de Porte station in the French Alps (1325 m asl) during the 2017 winter in order to investigate spatial and temporal variabilities of solar and infrared irradiances in different meteorological conditions. Sky view factors measured with hemispherical photographs at each radiometer location were in a narrow range from 0.2 to 0.3. The temperature of the vegetation was measured with IR thermocouples and an IR camera. In clear sky conditions, the attenuation of solar radiation by the canopy reached 96% and its spatial variability exceeded 100 W m-2. Longwave irradiance varied by 30 W m-2 from dense canopy to gap areas. In overcast conditions, the spatial variabilities of solar and infrared irradiances were reduced and remained closely related to the sky view factor. A simple radiative model taking into account the penetration through the canopy of the direct and diffuse solar radiation, and isotropic infrared emission of the vegetation as a blackbody emitter, accurately reproduced the dynamics of the radiation fluxes at the snow surface. Model results show that solar transmissivity of the canopy in overcast conditions is an excellent proxy of the sky view factor and the emitting temperature of the vegetation remained close to the air temperature in this typically dense Alpine forest.

Characterizing stand-level forest canopy cover and height using Landsat time series, samples of airborne LiDAR, and the Random Forest algorithm

NASA Astrophysics Data System (ADS)

Ahmed, Oumer S.; Franklin, Steven E.; Wulder, Michael A.; White, Joanne C.

2015-03-01

Many forest management activities, including the development of forest inventories, require spatially detailed forest canopy cover and height data. Among the various remote sensing technologies, LiDAR (Light Detection and Ranging) offers the most accurate and consistent means for obtaining reliable canopy structure measurements. A potential solution to reduce the cost of LiDAR data, is to integrate transects (samples) of LiDAR data with frequently acquired and spatially comprehensive optical remotely sensed data. Although multiple regression is commonly used for such modeling, often it does not fully capture the complex relationships between forest structure variables. This study investigates the potential of Random Forest (RF), a machine learning technique, to estimate LiDAR measured canopy structure using a time series of Landsat imagery. The study is implemented over a 2600 ha area of industrially managed coastal temperate forests on Vancouver Island, British Columbia, Canada. We implemented a trajectory-based approach to time series analysis that generates time since disturbance (TSD) and disturbance intensity information for each pixel and we used this information to stratify the forest land base into two strata: mature forests and young forests. Canopy cover and height for three forest classes (i.e. mature, young and mature and young (combined)) were modeled separately using multiple regression and Random Forest (RF) techniques. For all forest classes, the RF models provided improved estimates relative to the multiple regression models. The lowest validation error was obtained for the mature forest strata in a RF model (R2 = 0.88, RMSE = 2.39 m and bias = -0.16 for canopy height; R2 = 0.72, RMSE = 0.068% and bias = -0.0049 for canopy cover). This study demonstrates the value of using disturbance and successional history to inform estimates of canopy structure and obtain improved estimates of forest canopy cover and height using the RF algorithm.

Seeing through the Canopy: Relationship between Coarse Woody Debris and Forest Structure measured by Airborne Lidar in the Brazilian Amazon

NASA Astrophysics Data System (ADS)

Scaranello, M. A., Sr.; Keller, M. M.; dos-Santos, M. N.; Longo, M.; Pinagé, E. R.; Leitold, V.

2016-12-01

Coarse woody debris is an important but infrequently quantified carbon pool in tropical forests. Based on studies at 12 sites spread across the Brazilian Amazon, we quantified coarse woody debris stocks in intact forests and forests affected by different intensities of degradation by logging and/or fire. Measurement were made in-situ and for the first time field measurements of coarse woody debris were related to structural metrics derived from airborne lidar. Using the line-intercept method we established 84 transects for sampling fallen coarse woody debris and associated inventory plots for sampling standing dead wood in intact, conventional logging, reduced impact logging, burned and burned after logging forests. Overall mean and standard deviation of total coarse woody debris were 50.0 Mg ha-1 and 26.4 Mg ha-1 respectively. Forest degradation increased coarse woody debris stocks compared to intact forests by a factor of 1.7 in reduced impact logging forests and up to 3-fold in burned forests, in a side-by-side comparison of nearby areas. The ratio between coarse woody debris and biomass increased linearly with number of degradation events (R²: 0.67, p<0.01). Individual lidar-derived structural variables strongly correlated with coarse woody debris in intact and reduced impact logging forests: the 5th percentile of last returns for in intact forests (R²: 0.78, p<0.01) and forest gap area, mapped using lidar-derived canopy height model, for reduced impact logging forests (R²: 0.63, p<0.01). Individual gap area also played a weak but significant role in determining coarse woody debris in burned forests (R2: 0.21, p<0.05), but with contrasting trend. Both degradation-specific and general multiple models using lidar-derived variables were good predictor of coarse woody debris stocks in different degradation levels in the Brazilian Amazon. The strong relation of coarse woody debris with lidar derived structural variables suggests an approach for quantifying infrequently measured coarse woody debris over large areas.

[Turbulent characteristics in forest canopy under atmospheric neutral condition].

PubMed

Diao, Yi-Wei; Guan, De-Xin; Jin, Chang-Jie; Wang, An-Zhi; Pei, Tie-Fan

2010-02-01

Based on the micrometeorological data of broad-leaved Korean pine forest in Changbai Mountain in 2003, a second-order closure model was employed to calculate and analyze the turbulent characteristics within and above the canopy of the forest. The calculated mean wind profile was coincident with the measured one. The Reynolds stress within the forest was significantly attenuated. The turbulent strength, velocity flux, and skew were the largest at forest-atmosphere interface, as well the wind shear. With the increase of velocity skew, the turbulent intermittence became more significant, and the downward turbulent eddy within the canopy was limited. Most of the turbulent deeply within the forest canopy was produced by the non-local contributions above the canopy.

Landscape distribution and characteristics of large hurricane-related canopy gaps in a southern Appalachian watershed

Treesearch

W. Henry McNab; Cathryn H. Greenberg; Erik C. Berg

2004-01-01

Hurricane-related winds are a major source of disturbance in coastal ecosystems of the southern United States, but their effects on forests in the southern Appalachian Mountains, >400 km inland, have seldom been documented. In October 1995, remnant winds of Hurricane Opal caused windthrow of individual and patches of trees throughout the mountainous region of...

Differential responses of Bolivian timber species to prescribed fire and other gap treatments

Treesearch

Debora K. Kennard; Francis E. Putz

2005-01-01

We followed the establishment and growth response of 13 commercial tree species to canopy opening, above-ground biomass removal, and experimental burns of low and high intensities in a lowland dry forest in Bolivia. Three patterns of response to treatments were observed among the most abundant commercial tree species. (1) Shade-intolerant species regenerated mostly...

Correction to the plant canopy gap-size analysis theory used by the Tracing Radiation and Architecture of Canopies instrument

NASA Astrophysics Data System (ADS)

Leblanc, Sylvain G.

2002-12-01

A plant canopy gap-size analyzer, the Tracing Radiation and Architecture of Canopies (TRAC), developed by Chen and Cihlar [Appl. Opt. 34, 6211 (1995)] and commercialized by 3rd Wave Engineering (Nepean, Canada), has been used around the world to quantify the fraction of photosynthetically active radiation absorbed by plant canopies, the leaf area index (LAI), and canopy architectural parameters. The TRAC is walked under a canopy along transects to measure sunflecks that are converted into a gap-size distribution. A numerical gap-removal technique is performed to remove gaps that are not theoretically possible in a random canopy. The resulting reduced gap-size distribution is used to quantify the heterogeneity of the canopy and to improve LAI measurements. It is explicitly shown here that the original derivation of the clumping index was missing a normalization factor. For a very clumped canopy with a large gap fraction, the resulting LAI can be more than 100% smaller than previously estimated. A test case is used to demonstrate that the new clumping index derivation allows a more accurate change of LAI to be measured.

Changes in canopy processes following whole-forest canopy nitrogen fertilization of a mature spruce-hemlock forest

Treesearch

E. Gaige; D.B. Dail; D.Y. Hollinger; E.A. Davidson; I.J. Fernandez; H. Sievering; A. White; W. Halteman

2007-01-01

Most experimental additions of nitrogen to forest ecosystems apply the N to the forest floor, bypassing important processes taking place in the canopy, including canopy retention of N and/or conversion of N from one form to another. To quantify these processes, we carried out a large-scale experiment and determined the fate of nitrogen applied directly to a mature...

Phenology, seed dispersal and difficulties in natural recruitment of the canopy tree Pachira quinata (Malvaceae).

PubMed

Castellanos, Maria Clara; Stevenson, Pablo R

2011-06-01

Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachira quinata (Malvaceae), at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations.

Seed dispersal increases local species richness and reduces spatial turnover of tropical tree seedlings

PubMed Central

Dunham, Amy E.; Duncan, Richard P.; Rogers, Haldre S.

2017-01-01

Dispersal is thought to be a key process underlying the high spatial diversity of tropical forests. Just how important dispersal is in structuring plant communities is nevertheless an open question because it is very difficult to isolate dispersal from other processes, and thereby measure its effect. Using a unique situation, the loss of vertebrate seed dispersers on the island of Guam and their presence on the neighboring islands of Saipan and Rota, we quantify the contribution of vertebrate seed dispersal to spatial patterns of diversity of tree seedlings in treefall gaps. The presence of vertebrate seed dispersers approximately doubled seedling species richness within canopy gaps and halved species turnover among gaps. Our study demonstrates that dispersal plays a key role in maintaining local and regional patterns of diversity, and highlights the potential for ongoing declines in vertebrate seed dispersers to profoundly alter tropical forest composition. PMID:28847937

Seed dispersal increases local species richness and reduces spatial turnover of tropical tree seedlings.

PubMed

Wandrag, Elizabeth M; Dunham, Amy E; Duncan, Richard P; Rogers, Haldre S

2017-10-03

Dispersal is thought to be a key process underlying the high spatial diversity of tropical forests. Just how important dispersal is in structuring plant communities is nevertheless an open question because it is very difficult to isolate dispersal from other processes, and thereby measure its effect. Using a unique situation, the loss of vertebrate seed dispersers on the island of Guam and their presence on the neighboring islands of Saipan and Rota, we quantify the contribution of vertebrate seed dispersal to spatial patterns of diversity of tree seedlings in treefall gaps. The presence of vertebrate seed dispersers approximately doubled seedling species richness within canopy gaps and halved species turnover among gaps. Our study demonstrates that dispersal plays a key role in maintaining local and regional patterns of diversity, and highlights the potential for ongoing declines in vertebrate seed dispersers to profoundly alter tropical forest composition.

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.

Influence of Forest-Canopy Morphology and Relief on Spectral Characteristics of Taiga Forests

NASA Astrophysics Data System (ADS)

Zhirin, V. M.; Knyazeva, S. V.; Eydlina, S. P.

2017-12-01

The article deals with the results of a statistical analysis reflecting tendencies (trends) of the relationship between spectral characteristics of taiga forests, indicators of the morphological structure of forest canopy and illumination of the territory. The study was carried out on the example of the model forest territory of the Priangarskiy taiga region of Eastern Siberia (Krasnoyarsk krai) using historical data (forest inventory 1992, Landsat 5 TM 16.06.1989) and the digital elevation model. This article describes a method for determining the quantitative indicator of morphological structure of forest canopy based on taxation data, and the authors propose to subdivide the morphological structure into high complexity, medium complexity, and relatively simple. As a result of the research, dependences of average values of spectral brightness in near and short-wave infrared channels of a Landsat 5 TM image for dark-coniferous, light-coniferous and deciduous forests from the degree of complexity of the forest-canopy structure are received. A high level of variance and maximum brightness average values are marked in green moss (hilocominosa) dark-coniferous and various-grass (larioherbosa) dark-coniferous forests and light-coniferous forests with a complex structure of canopy. The parvifoliate forests are characterized by high values of brightness in stands with a relatively simple structure of the canopy and by a small variance in brightness of any degree of the structure of the canopy complexity. The increase in brightness for the lit slopes in comparison with shaded ones in all stands with a difficult morphological canopy structure is revealed. However, the brightness values of the lit and shaded slopes do not differ for stands with a medium complexity of the structure. It is noted that, in addition to the indicator of the forest-canopy structure, the possible impact on increasing the variance of spectral brightness for the taxation plot has a variability of the slope ratio of "microslopes" inside the forest plot if it exceeds 60%.

Nitrogen cycling in canopy soils of tropical montane forests responds rapidly to indirect N and P fertilization.

PubMed

Matson, Amanda L; Corre, Marife D; Veldkamp, Edzo

2014-12-01

Although the canopy can play an important role in forest nutrient cycles, canopy-based processes are often overlooked in studies on nutrient deposition. In areas of nitrogen (N) and phosphorus (P) deposition, canopy soils may retain a significant proportion of atmospheric inputs, and also receive indirect enrichment through root uptake followed by throughfall or recycling of plant litter in the canopy. We measured net and gross rates of N cycling in canopy soils of tropical montane forests along an elevation gradient and assessed indirect effects of elevated nutrient inputs to the forest floor. Net N cycling rates were measured using the buried bag method. Gross N cycling rates were measured using (15) N pool dilution techniques. Measurements took place in the field, in the wet and dry season, using intact cores of canopy soil from three elevations (1000, 2000 and 3000 m). The forest floor had been fertilized biannually with moderate amounts of N and P for 4 years; treatments included control, N, P, and N + P. In control plots, gross rates of NH4 (+) transformations decreased with increasing elevation; gross rates of NO3 (-) transformations did not exhibit a clear elevation trend, but were significantly affected by season. Nutrient-addition effects were different at each elevation, but combined N + P generally increased N cycling rates at all elevations. Results showed that canopy soils could be a significant N source for epiphytes as well as contributing up to 23% of total (canopy + forest floor) mineral N production in our forests. In contrast to theories that canopy soils are decoupled from nutrient cycling in forest floor soil, N cycling in our canopy soils was sensitive to slight changes in forest floor nutrient availability. Long-term atmospheric N and P deposition may lead to increased N cycling, but also increased mineral N losses from the canopy soil system. © 2014 John Wiley & Sons Ltd.

Thermal Imaging of Forest Canopy Temperatures: Relationships with Biological and Biophysical Drivers and Ecosystem Fluxes

NASA Astrophysics Data System (ADS)

Still, C. J.; Kim, Y.; Hanson, C. V.; Law, B. E.; Kwon, H.; Schulze, M.; Pau, S.; Detto, M.

2015-12-01

Temperature is a primary environmental control on plant processes at a range of spatial and temporal scales, affecting enzymatic reactions, ecosystem biogeochemistry, and species distributions. Although most focus is on air temperature, the radiative or skin temperature of plants is more relevant. Canopy skin temperature dynamics reflect biophysical, physiological, and anatomical characteristics and interactions with environmental drivers, and can be used to examine forest responses to stresses like droughts and heat waves. Direct measurements of plant canopy temperatures using thermocouple sensors have been challenging and offer limited information. Such measurements are usually conducted over short periods of time and a limited spatial extent of the canopy. By contrast, thermal infrared (TIR) imaging allows for extensive temporal and spatial measurement of canopy temperature regimes. We present results of TIR imaging of forest canopies at a range of well-studied forest sites in the United States and Panama. These forest types include temperate rainforests, a semi­arid pine forest, and a semi­deciduous tropical forest. Canopy temperature regimes at these sites are highly variable spatially and temporally and display frequent departures from air temperature, particularly during clear sky conditions. Canopy tissue temperatures are often warmer (daytime) and colder (nighttime) than air temperature, and canopy structure seems to have a large influence on the thermal regime. Additionally, comparison of canopy temperatures to eddy covariance fluxes of carbon dioxide, water vapor, and energy reveals relationships not apparent using air temperature. Initial comparisons between our forest canopy temperatures and remotely sensed skin temperature using Landsat and MODIS data show reasonably good agreement. We conclude that temporal and spatial changes in canopy temperature and its relationship to biological and environmental factors can improve our understanding of how climate change is affecting forest function, and argue for wider deployment of thermal cameras in other ecosystems.

Canopy structure of tropical and sub-tropical rain forests in relation to conifer dominance analysed with a portable LIDAR system

PubMed Central

Aiba, Shin-ichiro; Akutsu, Kosuke; Onoda, Yusuke

2013-01-01

Background and Aims Globally, conifer dominance is restricted to nutient-poor habitats in colder, drier or waterlogged environments, probably due to competition with angiosperms. Analysis of canopy structure is important for understanding the mechanism of plant coexistence in relation to competition for light. Most conifers are shade intolerant, and often have narrow, deep, conical crowns. In this study it is predicted that conifer-admixed forests have less distinct upper canopies and more undulating canopy surfaces than angiosperm-dominated forests. Methods By using a ground-based, portable light detection and ranging (LIDAR) system, canopy structure was quantified for old-growth evergreen rainforests with varying dominance of conifers along altitudinal gradients (200–3100 m a.s.l.) on tropical and sub-tropical mountains (Mount Kinabalu, Malaysian Borneo and Yakushima Island, Japan) that have different conifer floras. Key Results Conifers dominated at higher elevations on both mountains (Podocarpaceae and Araucariaceae on Kinabalu and Cupressaceae and Pinaceae on Yakushima), but conifer dominance also varied with soil/substrate conditions on Kinabalu. Conifer dominance was associated with the existence of large-diameter conifers. Forests with higher conifer dominance showed a canopy height profile (CHP) more skewed towards the understorey on both Kinabalu and Yakushima. In contrast, angiosperm-dominated forests had a CHP skewed towards upper canopy, except for lowland dipterocarp forests and a sub-alpine scrub dominated by small-leaved Leptospermum recurvum (Myrtaceae) on Kinabalu. Forests with a less dense upper canopy had more undulating outer canopy surfaces. Mixed conifer–angiosperm forests on Yakushima and dipterocarp forests on Kinabalu showed similar canopy structures. Conclusions The results generally supported the prediction, suggesting that lower growth of angiosperm trees (except L. recurvum on Kinabalu) in cold and nutrient-poor environments results in a sparser upper canopy, which allows shade-intolerant conifers to co-occur with angiosperm trees either as emergents or as codominants in the open canopy. PMID:24197751

Canopy structure of tropical and sub-tropical rain forests in relation to conifer dominance analysed with a portable LIDAR system.

PubMed

Aiba, Shin-ichiro; Akutsu, Kosuke; Onoda, Yusuke

2013-12-01

Globally, conifer dominance is restricted to nutient-poor habitats in colder, drier or waterlogged environments, probably due to competition with angiosperms. Analysis of canopy structure is important for understanding the mechanism of plant coexistence in relation to competition for light. Most conifers are shade intolerant, and often have narrow, deep, conical crowns. In this study it is predicted that conifer-admixed forests have less distinct upper canopies and more undulating canopy surfaces than angiosperm-dominated forests. By using a ground-based, portable light detection and ranging (LIDAR) system, canopy structure was quantified for old-growth evergreen rainforests with varying dominance of conifers along altitudinal gradients (200-3100 m a.s.l.) on tropical and sub-tropical mountains (Mount Kinabalu, Malaysian Borneo and Yakushima Island, Japan) that have different conifer floras. Conifers dominated at higher elevations on both mountains (Podocarpaceae and Araucariaceae on Kinabalu and Cupressaceae and Pinaceae on Yakushima), but conifer dominance also varied with soil/substrate conditions on Kinabalu. Conifer dominance was associated with the existence of large-diameter conifers. Forests with higher conifer dominance showed a canopy height profile (CHP) more skewed towards the understorey on both Kinabalu and Yakushima. In contrast, angiosperm-dominated forests had a CHP skewed towards upper canopy, except for lowland dipterocarp forests and a sub-alpine scrub dominated by small-leaved Leptospermum recurvum (Myrtaceae) on Kinabalu. Forests with a less dense upper canopy had more undulating outer canopy surfaces. Mixed conifer-angiosperm forests on Yakushima and dipterocarp forests on Kinabalu showed similar canopy structures. The results generally supported the prediction, suggesting that lower growth of angiosperm trees (except L. recurvum on Kinabalu) in cold and nutrient-poor environments results in a sparser upper canopy, which allows shade-intolerant conifers to co-occur with angiosperm trees either as emergents or as codominants in the open canopy.

Using ALS and MODIS data to evaluate degradation in different forests types over the Xingu basin - Brazilian Amazon

NASA Astrophysics Data System (ADS)

Moura, Y.; Aragão, L. E.; Galvão, L. S.; Dalagnol, R.; Lyapustin, A.; Santos, E. G.; Espirito-Santo, F.

2017-12-01

Degradation of Amazon rainforests represents a vital threat to carbon storage, climate regulation and biodiversity; however its effect on tropical ecosystems is largely unknown. In this study we evaluate the effects of forest degradation on forest structure and functioning over the Xingu Basin in the Brazilian Amazon. The vegetation types in the area is dominated by Open Ombrophilous Forest (Asc), Semi-decidiuous Forest (Fse) and Dense Ombrophilous Forest (Dse). We used Airborne Laser Scanning (ALS) data together with time series of optical remote sensing images from the Moderate Resolution Imaging Spectroradiometer (MODIS) bi-directional corrected using the Multi-Angle Implementation for Atmospheric Correction (MAIAC). We derive time-series (2008 to 2016) of the Enhanced Vegetation Index (EVI) and Green-Red Normalized Difference (GRND) to analyze the dynamics of degraded areas with related changes in canopy structure and greenness values, respectively. Airborne ALS measurements showed the largest tree heights in the Dse class with values up to 40m tall. Asc and Fse vegetation types reached up to 30m and 25m in height, respectively. Differences in canopy structure were also evident from the analysis of canopy volume models (CVMs). Asc showed higher proportion of sunlit, as expected for open forest types. Fse showed gaps predominantly in lower height levels, and a higher overall proportion of shaded crown. Full canopy closure was reached at about15 m height for both Asc and Dse, and at about 20 m height for Fse. We also used a base map of degraded areas (available from Imazon - Instituto do Homen e Meio Ambiente da Amazônia) to follow these regions throughout time using EVI and GRND from MODIS. All three forest types displayed seasonal cycles. Notable differences in amplitude were detected during the periods when degradation occurred and both indexes showed a decrease in their response. However, there were marked differences in timing and amplitude depending on forest type. These responses were influenced by the spatial resolution of 1km of the MODIS images, limited the ability to observe small degraded regions. In conclusion, ASL together with optical remote sensing used in a straight multi-scale approach may contribute to understand the impacts of degradation in the structure and functioning of tropical forest.

Finescale turbulence and seabed scouring around pneumatophores in a wave-exposed mangrove forest

NASA Astrophysics Data System (ADS)

Mullarney, J. C.; Norris, B. K.; Henderson, S. M.; Bryan, K. R.

2015-12-01

Coastal mangroves provide a barrier between the coast and lower energy intertidal environments. The presence of mangrove roots (pneumatophores) alters local hydrodynamics by slowing currents, dissipating waves, enhancing within-canopy turbulence, and introducing significant spatial variability to the flow, particularly on the stem scale. To date, limited measurements exist within pneumatophore regions owing to the difficulties of measuring on sufficiently small scales. Hence, little is known about the turbulence controlling sediment transport within these regions. We report unique field observations near the seaward edge of a mangrove forest in the Mekong Delta, Vietnam. This forest is exposed to moderate wave energy (maximum heights of around 1 m), with waves observed to propagate and break up to 100 m inside the forest. Our measurements focus on a rapidly prograding area with a relatively sandy substrate and a gentle topographic slope. We resolved millimeter-scale turbulent flows within and above the pneumatophore canopy. Precise measurements of vegetation densities as a function of height were obtained using photogrammetry techniques. The dissipation rate of turbulent kinetic energy was enhanced at the canopy edge (ɛ ~ 10-4 W/kg), and decreased with distance into the forest (ɛ ~ 10-5 W/kg), although rates remained elevated above values measured on the tidal flat immediately offshore of the mangroves (ɛ ~ 10-6 W/kg). The dependence of turbulence on vegetation characteristics and on the stage of the tidal cycle is explored. The hydrodynamic measurements are then linked with changes in bathymetric features noted after a large wave event. Finer mud sediments were deposited outside the forest on the intertidal mudflat, whereas sandy sediments in the fringe region were significant scoured around regions of dense pneumatophores, and sediment mounds developed in the gaps between pneumatophores.

Estimating Leaf Area Index in Southeast Alaska: A Comparison of Two Techniques

PubMed Central

Eckrich, Carolyn A.; Flaherty, Elizabeth A.; Ben-David, Merav

2013-01-01

The relationship between canopy structure and light transmission to the forest floor is of particular interest for studying the effects of succession, timber harvest, and silviculture prescriptions on understory plants and trees. Indirect measurements of leaf area index (LAI) estimated using gap fraction analysis with linear and hemispheric sensors have been commonly used to assess radiation interception by the canopy, although the two methods often yield inconsistent results. We compared simultaneously obtained measurements of LAI from a linear ceptometer and digital hemispheric photography in 21 forest stands on Prince of Wales Island, Alaska. We assessed the relationship between these estimates and allometric LAI based on tree diameter at breast height (LAIDBH). LAI values measured at 79 stations in thinned, un-thinned controls, old-growth and clearcut stands were highly correlated between the linear sensor (AccuPAR) and hemispheric photography, but the latter was more negatively biased compared to LAIDBH. In contrast, AccuPAR values were more similar to LAIDBH in all stands with basal area less than 30 m2ha−1. Values produced by integrating hemispheric photographs over the zenith angles 0–75° (Ring 5) were highly correlated with those integrated over the zenith angles 0–60° (Ring 4), although the discrepancies between the two measures were significant. On average, the AccuPAR estimates were 53% higher than those derived from Ring 5, with most of the differences in closed canopy stands (unthinned controls and old-growth) and less so in clearcuts. Following typical patterns of canopy closure, AccuPAR LAI values were higher in dense control stands than in old-growth, whereas the opposite was derived from Ring 5 analyses. Based on our results we advocate the preferential use of linear sensors where canopy openness is low, canopies are tall, and leaf distributions are clumped and angles are variable, as is common in the conifer forests of coastal Alaska. PMID:24223718

Mapping canopy defoliation by herbivorous insects at the individual tree level using bi-temporal airborne imaging spectroscopy and LiDAR measurements

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

Meng, Ran; Dennison, Philip E.; Zhao, Feng

Defoliation by herbivorous insects is a widespread forest disturbance driver, affecting global forest health and ecosystem dynamics. Additionally, compared with time- and labor-intensive field surveys, remote sensing provides the only realistic approach to mapping canopy defoliation by herbivorous insects over large spatial and temporal scales. However, the spectral and structural signatures of defoliation by insects at the individual tree level have not been well studied. Additionally, the predictive power of spectral and structural metrics for mapping canopy defoliation has seldom been compared. These critical knowledge gaps prevent us from consistently detecting and mapping canopy defoliation by herbivorous insects across multiplemore » scales. During the peak of a gypsy moth outbreak in Long Island, New York in summer 2016, we leveraged bi-temporal airborne imaging spectroscopy (IS, i.e., hyperspectral imaging) and LiDAR measurements at 1m spatial resolution to explore the spectral and structural signatures of canopy defoliation in a mixed oak-pine forest. We determined that red edge and near-infrared spectral regions within the IS data were most sensitive to crown-scale defoliation severity. LiDAR measurements including B70 (i.e., 70th bincentile height), intensity skewness, and kurtosis were effectively able to detect structural changes caused by herbivorous insects. In addition to canopy leaf loss, increased exposure of understory and non-photosynthetic materials contributed to the detected spectral and structural signatures. Comparing the ability of individual sensors to map canopy defoliation, the LiDAR-only Ordinary Least-Square (OLS) model performed better than the IS-only model (Adj. R-squared = 0.77, RMSE = 15.37% vs. Adj. R- squared = 0.63, RMSE = 19.11%). The IS+LiDAR model improved on performance of the individual sensors (Adj. R-squared = 0.81, RMSE = 14.46%). Our study improves our understanding of spectral and structural signatures of defoliation by herbivorous insects and presents a novel approach for mapping insect defoliation at the individual tree level. Furthermore, with the current and next generation of spaceborne sensors (e.g., WorldView-3, Landsat, Sentinel-2, HyspIRI, and GEDI), higher accuracy and frequent monitoring of insect defoliation may become more feasible across a range of spatial scales, which are critical for ecological research and management of forest resources including the economic consequences of forest insect infestations (e.g., reduced growth and increased mortality), as well as for informing and testing of carbon cycle models.« less

Mapping canopy defoliation by herbivorous insects at the individual tree level using bi-temporal airborne imaging spectroscopy and LiDAR measurements

DOE PAGES

Meng, Ran; Dennison, Philip E.; Zhao, Feng; ...

2018-06-19

Defoliation by herbivorous insects is a widespread forest disturbance driver, affecting global forest health and ecosystem dynamics. Additionally, compared with time- and labor-intensive field surveys, remote sensing provides the only realistic approach to mapping canopy defoliation by herbivorous insects over large spatial and temporal scales. However, the spectral and structural signatures of defoliation by insects at the individual tree level have not been well studied. Additionally, the predictive power of spectral and structural metrics for mapping canopy defoliation has seldom been compared. These critical knowledge gaps prevent us from consistently detecting and mapping canopy defoliation by herbivorous insects across multiplemore » scales. During the peak of a gypsy moth outbreak in Long Island, New York in summer 2016, we leveraged bi-temporal airborne imaging spectroscopy (IS, i.e., hyperspectral imaging) and LiDAR measurements at 1m spatial resolution to explore the spectral and structural signatures of canopy defoliation in a mixed oak-pine forest. We determined that red edge and near-infrared spectral regions within the IS data were most sensitive to crown-scale defoliation severity. LiDAR measurements including B70 (i.e., 70th bincentile height), intensity skewness, and kurtosis were effectively able to detect structural changes caused by herbivorous insects. In addition to canopy leaf loss, increased exposure of understory and non-photosynthetic materials contributed to the detected spectral and structural signatures. Comparing the ability of individual sensors to map canopy defoliation, the LiDAR-only Ordinary Least-Square (OLS) model performed better than the IS-only model (Adj. R-squared = 0.77, RMSE = 15.37% vs. Adj. R- squared = 0.63, RMSE = 19.11%). The IS+LiDAR model improved on performance of the individual sensors (Adj. R-squared = 0.81, RMSE = 14.46%). Our study improves our understanding of spectral and structural signatures of defoliation by herbivorous insects and presents a novel approach for mapping insect defoliation at the individual tree level. Furthermore, with the current and next generation of spaceborne sensors (e.g., WorldView-3, Landsat, Sentinel-2, HyspIRI, and GEDI), higher accuracy and frequent monitoring of insect defoliation may become more feasible across a range of spatial scales, which are critical for ecological research and management of forest resources including the economic consequences of forest insect infestations (e.g., reduced growth and increased mortality), as well as for informing and testing of carbon cycle models.« less

Spatially explicit modelling of forest structure and function using airborne lidar and hyperspectral remote sensing data combined with micrometeorological measurements

NASA Astrophysics Data System (ADS)

Thomas, Valerie Anne

This research models canopy-scale photosynthesis at the Groundhog River Flux Site through the integration of high-resolution airborne remote sensing data and micrometeorological measurements collected from a flux tower. Light detection and ranging (lidar) data are analysed to derive models of tree structure, including: canopy height, basal area, crown closure, and average aboveground biomass. Lidar and hyperspectral remote sensing data are used to model canopy chlorophyll (Chl) and carotenoid concentrations (known to be good indicators of photosynthesis). The integration of lidar and hyperspectral data is applied to derive spatially explicit models of the fraction of photosynthetically active radiation (fPAR) absorbed by the canopy as well as a species classification for the site. These products are integrated with flux tower meteorological measurements (i.e., air temperature and global solar radiation) collected on a continuous basis over 2004 to apply the C-Fix model of carbon exchange to the site. Results demonstrate that high resolution lidar and lidar-hyperspectral integration techniques perform well in the boreal mixedwood environment. Lidar models are well correlated with forest structure, despite the complexities introduced in the mixedwood case (e.g., r2=0.84, 0.89, 0.60, and 0.91, for mean dominant height, basal area, crown closure, and average aboveground biomass). Strong relationships are also shown for canopy scale chlorophyll/carotenoid concentration analysis using integrated lidar-hyperspectral techniques (e.g., r2=0.84, 0.84, and 0.82 for Chl(a), Chl(a+b), and Chl(b)). Examination of the spatially explicit models of fPAR reveal distinct spatial patterns which become increasingly apparent throughout the season due to the variation in species groupings (and canopy chlorophyll concentration) within the 1 km radius surrounding the flux tower. Comparison of results from the modified local-scale version of the C-Fix model to tower gross ecosystem productivity (GEP) demonstrate a good correlation to flux tower measured GEP (r2=0.70 for 10 day averages), with the largest deviations occurring in June-July. This research has direct benefits for forest inventory mapping and management practices; mapping of canopy physiology and biochemical constituents related to forest health; and scaling and direct comparison to large resolution satellite models to help bridge the gap between the local-scale measurements at flux towers and predictions derived from continental-scale carbon models.

Vertical stratification of beetles (Coleoptera) and flies (Diptera) in temperate forest canopies.

PubMed

Maguire, Dorothy Y; Robert, Katleen; Brochu, Kristen; Larrivée, Maxim; Buddle, Christopher M; Wheeler, Terry A

2014-02-01

Forest canopies support high arthropod biodiversity, but in temperate canopies, little is known about the spatial distribution of these arthropods. This is an important first step toward understanding ecological roles of insects in temperate canopies. The objective of this study was to assess differences in the species composition of two dominant and diverse taxa (Diptera and Coleoptera) along a vertical gradient in temperate deciduous forest canopies. Five sugar maple trees from each of three deciduous forest sites in southern Quebec were sampled using a combination of window and trunk traps placed in three vertical strata (understory, mid-canopy, and upper-canopy) for three sampling periods throughout the summer. Coleoptera species richness and abundance did not differ between canopy heights, but more specimens and species of Diptera were collected in the upper-canopy. Community composition of Coleoptera and Diptera varied significantly by trap height. Window traps collected more specimens and species of Coleoptera than trunk traps, although both trap types should be used to maximize representation of the entire Coleoptera community. There were no differences in abundance, diversity, or composition of Diptera collected between trap types. Our data confirm the relevance of sampling all strata in a forest when studying canopy arthropod biodiversity.

Groundlayer vegetation gradients across oak woodland canopy gaps

USGS Publications Warehouse

Pavlovic, N.B.; Grundel, R.; Sluis, W.

2006-01-01

Frequency of groundlayer plants was measured across oak woodland canopy gaps at three sites in northwest Indiana to examine how vegetation varied with gap size, direction along the gap edge, and microhabitat. Microhabitats were defined as under the canopy adjacent to the gap, along the gap edge, and within the gap. Gap-sites consisted of gaps plus adjacent tree canopy. Gaps were classified as small (16 ± 1 m2), medium (97 ± 8), and large (310 ± 32). Neither richness nor diversity differed among microhabitats, gap sizes, or edges. Similarity between microhabitats wthin a gap-site increased as the distance between plots decreased and as the difference in PAR decreased, the latter explaining twice the variation in percent dissimilarity compared to Mg concentration, A horizon depth, and litter cover. Diervilla lonicera, Frageria virginiana, Helianthus divaricatus, Polygonatum pubescens, Quercus velutina, Smilacena stellata, and Tradescantia ohiensis decreased, whileTephrosia virginiana and legumes increased in frequency, from canopy to gap, and C4 grasses peaked at the gap edge, independent of gap size. Additional species frequency varied across the microhabitat gradient within specific sites. Sorghastrum nutans was three times more frequent in gaps at large sites than elsewhere. The vegetation in medium-sized gap-sites was more variable than within small and large gap-sites, suggesting greater environmental heterogeneity at that scale. Within gap-sites, vegetation was more heterogeneous within edges and canopies than in gaps. Edges were more similar in composition to gaps than to canopy groundlayer within gap-sites. Few species varied significantly in frequency around the gap edge. The oak woodland groundlayer on sandy substrates can be characterized as a mosaic of forb dominated vegetation that varies across light gradients associated with canopy gaps, transitioning to islands of grassland vegetation when gaps exceed 160 m2.

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.

Examining conifer canopy structural complexity across forest ages and elevations with LiDAR data

Treesearch

Van R. Kane; Jonathan D. Bakker; Robert J. McGaughey; James A. Lutz; Rolf F. Gersonde; Jerry F. Franklin

2010-01-01

LiDAR measurements of canopy structure can be used to classify forest stands into structural stages to study spatial patterns of canopy structure, identify habitat, or plan management actions. A key assumption in this process is that differences in canopy structure based on forest age and elevation are consistent with predictions from models of stand development. Three...

Calibration and Validation of Landsat Tree Cover in the Taiga-Tundra Ecotone

NASA Technical Reports Server (NTRS)

Montesano, Paul Mannix; Neigh, Christopher S. R.; Sexton, Joseph; Feng, Min; Channan, Saurabh; Ranson, Kenneth J.; Townshend, John R.

2016-01-01

Monitoring current forest characteristics in the taiga-tundra ecotone (TTE) at multiple scales is critical for understanding its vulnerability to structural changes. A 30 m spatial resolution Landsat-based tree canopy cover map has been calibrated and validated in the TTE with reference tree cover data from airborne LiDAR and high resolution spaceborne images across the full range of boreal forest tree cover. This domain-specific calibration model used estimates of forest height to determine reference forest cover that best matched Landsat estimates. The model removed the systematic under-estimation of tree canopy cover greater than 80% and indicated that Landsat estimates of tree canopy cover more closely matched canopies at least 2 m in height rather than 5 m. The validation improved estimates of uncertainty in tree canopy cover in discontinuous TTE forests for three temporal epochs (2000, 2005, and 2010) by reducing systematic errors, leading to increases in tree canopy cover uncertainty. Average pixel-level uncertainties in tree canopy cover were 29.0%, 27.1% and 31.1% for the 2000, 2005 and 2010 epochs, respectively. Maps from these calibrated data improve the uncertainty associated with Landsat tree canopy cover estimates in the discontinuous forests of the circumpolar TTE.

Forest Management in Earth System Modelling: a Vertically Discretised Canopy Description for ORCHIDEE and Effects on European Climate Since 1750

NASA Astrophysics Data System (ADS)

McGrath, M.; Luyssaert, S.; Naudts, K.; Chen, Y.; Ryder, J.; Otto, J.; Valade, A.

2015-12-01

Forest management has the potential to impact surface physical characteristics to the same degree that changes in land cover do. The impacts of land cover changes on the global climate are well-known. Despite an increasingly detailed understanding of the potential for forest management to affect climate, none of the current generation of Earth system models account for forest management through their land surface modules. We addressed this gap by developing and reparameterizing the ORCHIDEE land surface model to simulate the biogeochemical and biophysical effects of forest management. Through vertical discretization of the forest canopy and corresponding modifications to the energy budget, radiation transfer, and carbon allocation, forest management can now be simulated much more realistically on the global scale. This model was used to explore the effect of forest management on European climate since 1750. Reparameterization was carried out to replace generic forest plant functional types with real tree species, covering the most dominant species across the continent. Historical forest management and land cover maps were created to run the simulations from 1600 until the present day. The model was coupled to the atmospheric model LMDz to explore differences in climate between 1750 and 2010 and attribute those differences to changes in atmospheric carbon dioxide concentrations and concurrent warming, land cover, species composition, and wood extraction. Although Europe's forest are considered a carbon sink in this century, our simulations show the modern forests are still experiencing carbon debt compared to their historical values.

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.

Altered structural development and accelerated succession from intermediate-scale wind disturbance in Quercus stands on the Cumberland Plateau, USA

Treesearch

Stephen D White; Justin L. Hart; Callie J. Schweitzer; Daniel C. Dey

2015-01-01

Natural disturbances play important roles in shaping the structure and composition of all forest ecosystems and can be used to inform silvicultural practices. Canopy disturbances are often classified along a gradient ranging from highly localized, gap-scale events to stand-replacing events. Wind storms such as downbursts, derechos, and low intensity tornadoes typically...

Seedling growth responses to light and mineral N form are predicted by species ecologies and can help explain tree diversity

Treesearch

Michael B. Walters; John L. Willis; Kurt W. Gottschalk

2014-01-01

Tree species distributions and diversity could be explained by rank changes in performance over multiple spatiotemporal resource gradients, i.e., resource partitioning. For 14 species planted in 45 harvest gap and closed canopy locations in a mesic northern hardwood forest community, Michigan, USA, we asked the following questions: (i) are species growth responses to...

[Canopy interception characteristics of main vegetation types in Liupan Mountains of China].

PubMed

Xu, Li-hong; Shi, Zhong-jie; Wang, Yan-hui; Xiong, Wei; Yu, Peng-tao

2010-10-01

Based on field observation and modeling analysis, this paper studied the canopy interception, interception capacity, and some parameters for interception modeling of main forest types in Liupan Mountains of China. For the test main forest types, the ratio of their canopy interception to precipitation ranged from 8.59% to 17.94%, throughfall was more than 80%, and stemflow ranged from 0.23% to 3.10%. The canopy interception capacity was 0.78-1.88 mm, among which, leaf interception capacity was 0.62-1.63 mm, and stem interception capacity was 0.13-0.29 mm. Conifer forest had a higher canopy interception capacity than broad-leaved forest. The modified model considering the change of leaf area index, which was used in this paper, had a higher simulating precision than the interception model used before. The simulation results for Betula albo-sinensis forest, Pinus armandii forest, Prunus shrub, and Quercus liaotungensis-Tilia paucicostata forest were good, but those for Quercus liaotungensis forest, Pinus tabulaeformis forest, and Acer tetramerum and Euonymus sanguineus shrub were bad, which might be related to the differences in canopy structure, leaf area index, and precipitation characteristics.

Persistent effects of a severe drought on Amazonian forest canopy.

PubMed

Saatchi, Sassan; Asefi-Najafabady, Salvi; Malhi, Yadvinder; Aragão, Luiz E O C; Anderson, Liana O; Myneni, Ranga B; Nemani, Ramakrishna

2013-01-08

Recent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate perturbations. Satellite and in situ observations have shown an increase in fire occurrence during drought years and tree mortality following severe droughts, but to date there has been no assessment of long-term impacts of these droughts across landscapes in Amazonia. Here, we use satellite microwave observations of rainfall and canopy backscatter to show that more than 70 million hectares of forest in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy structure and moisture. Remarkably, and despite the gradual recovery in total rainfall in subsequent years, the decrease in canopy backscatter persisted until the next major drought, in 2010. The decline in backscatter is attributed to changes in structure and water content associated with the forest upper canopy. The persistence of low backscatter supports the slow recovery (>4 y) of forest canopy structure after the severe drought in 2005. The result suggests that the occurrence of droughts in Amazonia at 5-10 y frequency may lead to persistent alteration of the forest canopy.

Application of Lidar remote sensing to the estimation of forest canopy and stand structure

NASA Astrophysics Data System (ADS)

Lefsky, Michael Andrew

A new remote sensing instrument, SLICER (Scanning Lidar Imager of Canopies by Echo Recovery), has been applied to the problem of remote sensing the canopy and stand structure of two groups of deciduous forests, Tulip Poplar-Oak stands in the vicinity of Annapolis, MD. and bottomland hardwood stands near Williamston, NC. The ability of the SLICER instrument to remotely sense the vertical distribution of canopy structure (Canopy Height Profile), bulk canopy transmittance, and several indices of canopy height has been successfully validated using twelve stands with coincident field and SLICER estimates of canopy structure. Principal components analysis has been applied to canopy height profiles from both field sites, and three significant factors were identified, each closely related to the amount of foliage in a recognizable layer of the forest, either understory, midstory, or overstory. The distribution of canopy structure to these layers is significantly correlated with the size and number of stems supporting them. The same layered structure was shown to apply to both field and SLICER remotely sensed canopy height profiles, and to apply to SLICER remotely sensed canopy profiles from both the bottomland hardwood stands in the coastal plain of North Carolina, and to mesic Tulip-Poplars stands in the upland coastal plain of Maryland. Linear regressions have demonstrated that canopy and stand structure are correlated to both a statistically significant and useful degree. Stand age and stem density is more highly correlated to stand height, while stand basal area and aboveground biomass are more closely related to a new measure of canopy structure, the quadratic mean canopy height. A geometric model of canopy structure has been shown to explain the differing relationships between canopy structure and stand basal area for stands of Eastern Deciduous Forest and Douglas Fir Forest.

Remote sensing of canopy chemistry and nitrogen cycling in temperate forest ecosystems

NASA Technical Reports Server (NTRS)

Wessman, Carol A.; Aber, John D.; Peterson, David L.; Melillo, Jerry M.

1988-01-01

The use of images acquired by the Airborne Imaging Spectrometer, an experimental high-spectral resolution imaging sensor developed by NASA, to estimate the lignin concentration of whole forest canopies in Wisconsin is reported. The observed strong relationship between canopy lignin concentration and nitrogen availability in seven undisturbed forest ecosystems on Blackhawk Island, Wisconsin, suggests that canopy lignin may serve as an index for site nitrogen status. This predictive relationship presents the opportunity to estimate nitrogen-cycling rates across forested landscapes through remote sensing.

Integration of lidar and Landsat ETM+ data for estimating and mapping forest canopy height.

Treesearch

Andrew T. Hudak; Michael A. Lefsky; Warren B. Cohen; Mercedes Berterretche

2002-01-01

Light detection and ranging (LIDAR) data provide accurate measurements of forest canopy structure in the vertical plane; however, current LIDAR sensors have limited coverage in the horizontal plane. Landsat data provide extensive coverage of generalized forest structural classes in the horizontal plane but are relatively insensitive to variation in forest canopy height...

The effects of cleared larch canopy and nitrogen supply on gas exchange and leaf traits in deciduous broad-leaved tree seedlings.

PubMed

Kitaoka, Satoshi; Watanabe, Yoko; Koike, Takayoshi

2009-12-01

To understand the leaf-level responses of successional tree species to forest gap formation and nitrogen deposition, we performed canopy clearing and nitrogen-amendment treatments in larch plantations and investigated the changes in the light-use characteristics and the leaf structure of the invading deciduous broad-leaved tree seedlings. We hypothesized that the responses of the tree seedlings to clearing and nitrogen input would reflect specific traits in the shoot development that would be related to the species-specific successional characteristics. The gap phase species Magnolia hyporeuca Siebold et Zucc. and the mid-late successional tree species Quercus mongolica Fischer ex Ledeb. var. crispula (Blume) Ohashi., which grow in or near the forest gaps, had higher light-saturated photosynthetic rates (Psat), enhanced mesophyll surface area (Smes) and increased leaf mass per area (LMA) under both the clearing treatment and the clearing with nitrogen-amendment treatment. These two species therefore increased their Psat via an increase in Smes and LMA. The LMA values of the late successional tree species Prunus ssiori F. Schmidt and Carpinus cordata Blume, which grow in the forest understory, were enhanced by the clearing treatment. However, they displayed lesser responses to the clearing treatment under which there were no marked increases in Psat or Smes values in the second year. These results indicate distinct and varied responses to disturbance regimes among the four seral tree seedlings. The Psat value largely increased in line with the increase in Smes value during the second year in M. hyporeuca and Q. mongolica. The nitrogen supply accelerated the change in LMA and increased the Smes value in the leaves of Q. mongolica.

A preliminary report on the measurements of forest canopies with C-band radar scatterometer at NASA/NSTL

NASA Technical Reports Server (NTRS)

Wu, S. T.

1985-01-01

This paper presents preliminary results of C-band radar scatterometer measurements of forest canopies of southeastern forests in the vicinity of NASA/NSTL. The results are as follows: (1) the radar backscattering coefficients (BSC) of deciduous forests such as oak, maple, blackgum, and cypress are higher than those of coniferous forests such as slash pine plantation and natural pine; (2) at a large incidence angle, where polarization effect is significant, and by ranging measurement, the VV polarization BSC obtain peak value at the first few meters from the canopy top and decrease rather quickly, while the HH polarization BSC obtain peak value at longer distances from the canopy top and decrease rather slowly through the canopy; and (3) using the active radar calibrator for tree canopy attenuation measurement of a dense and a sparse live oak, it is found that the tree canopies with higher attenuations have higher BSC for all three polarizations, with VV polarization containing the largest differential (2.2 dB).

Assessing the influence of flight parameters, interferometric processing, slope and canopy density on the accuracy of X-band IFSAR-derived forest canopy height models.

Treesearch

H.-E. Andersen; R.J. McGaughey; S.E. Reutebuch

2008-01-01

High resolution, active remote sensing technologies, such as interferometric synthetic aperture radar (IFSAR) and airborne laser scanning (LIDAR) have the capability to provide forest managers with direct measurements of 3-dimensional forest canopy surface structure. Although LIDAR systems can provide highly accurate measurements of canopy and terrain surfaces, high-...

Classification of Snowfall Events and Their Effect on Canopy Interception Efficiency in a Temperate Montane Forest.

NASA Astrophysics Data System (ADS)

Roth, T. R.; Nolin, A. W.

2015-12-01

Forest canopies intercept as much as 60% of snowfall in maritime environments, while processes of sublimation and melt can reduce the amount of snow transferred from the canopy to the ground. This research examines canopy interception efficiency (CIE) as a function of forest and event-scale snowfall characteristics. We use a 4-year dataset of continuous meteorological measurements and monthly snow surveys from the Forest Elevation Snow Transect (ForEST) network that has forested and open sites at three elevations spanning the rain-snow transition zone to the upper seasonal snow zone. Over 150 individual storms were classified by forest and storm type characteristics (e.g. forest density, vegetation type, air temperature, snowfall amount, storm duration, wind speed, and storm direction). The between-site comparisons showed that, as expected, CIE was highest for the lower elevation (warmer) sites with higher forest density compared with the higher elevation sites where storm temperatures were colder, trees were smaller and forests were less dense. Within-site comparisons based on storm type show that this classification system can be used to predict CIE.Our results suggest that the coupling of forest type and storm type information can improve estimates of canopy interception. Understanding the effects of temperature and storm type in temperate montane forests is also valuable for future estimates of canopy interception under a warming climate.

Incorporating Canopy Cover for Airborne-Derived Assessments of Forest Biomass in the Tropical Forests of Cambodia

PubMed Central

Singh, Minerva; Evans, Damian; Coomes, David A.; Friess, Daniel A.; Suy Tan, Boun; Samean Nin, Chan

2016-01-01

This research examines the role of canopy cover in influencing above ground biomass (AGB) dynamics of an open canopied forest and evaluates the efficacy of individual-based and plot-scale height metrics in predicting AGB variation in the tropical forests of Angkor Thom, Cambodia. The AGB was modeled by including canopy cover from aerial imagery alongside with the two different canopy vertical height metrics derived from LiDAR; the plot average of maximum tree height (Max_CH) of individual trees, and the top of the canopy height (TCH). Two different statistical approaches, log-log ordinary least squares (OLS) and support vector regression (SVR), were used to model AGB variation in the study area. Ten different AGB models were developed using different combinations of airborne predictor variables. It was discovered that the inclusion of canopy cover estimates considerably improved the performance of AGB models for our study area. The most robust model was log-log OLS model comprising of canopy cover only (r = 0.87; RMSE = 42.8 Mg/ha). Other models that approximated field AGB closely included both Max_CH and canopy cover (r = 0.86, RMSE = 44.2 Mg/ha for SVR; and, r = 0.84, RMSE = 47.7 Mg/ha for log-log OLS). Hence, canopy cover should be included when modeling the AGB of open-canopied tropical forests. PMID:27176218

Incorporating Canopy Cover for Airborne-Derived Assessments of Forest Biomass in the Tropical Forests of Cambodia.

PubMed

Singh, Minerva; Evans, Damian; Coomes, David A; Friess, Daniel A; Suy Tan, Boun; Samean Nin, Chan

2016-01-01

This research examines the role of canopy cover in influencing above ground biomass (AGB) dynamics of an open canopied forest and evaluates the efficacy of individual-based and plot-scale height metrics in predicting AGB variation in the tropical forests of Angkor Thom, Cambodia. The AGB was modeled by including canopy cover from aerial imagery alongside with the two different canopy vertical height metrics derived from LiDAR; the plot average of maximum tree height (Max_CH) of individual trees, and the top of the canopy height (TCH). Two different statistical approaches, log-log ordinary least squares (OLS) and support vector regression (SVR), were used to model AGB variation in the study area. Ten different AGB models were developed using different combinations of airborne predictor variables. It was discovered that the inclusion of canopy cover estimates considerably improved the performance of AGB models for our study area. The most robust model was log-log OLS model comprising of canopy cover only (r = 0.87; RMSE = 42.8 Mg/ha). Other models that approximated field AGB closely included both Max_CH and canopy cover (r = 0.86, RMSE = 44.2 Mg/ha for SVR; and, r = 0.84, RMSE = 47.7 Mg/ha for log-log OLS). Hence, canopy cover should be included when modeling the AGB of open-canopied tropical forests.

Forest canopy height estimation using double-frequency repeat pass interferometry

NASA Astrophysics Data System (ADS)

Karamvasis, Kleanthis; Karathanassi, Vassilia

2015-06-01

In recent years, many efforts have been made in order to assess forest stand parameters from remote sensing data, as a mean to estimate the above-ground carbon stock of forests in the context of the Kyoto protocol. Synthetic aperture radar interferometry (InSAR) techniques have gained traction in last decade as a viable technology for vegetation parameter estimation. Many works have shown that forest canopy height, which is a critical parameter for quantifying the terrestrial carbon cycle, can be estimated with InSAR. However, research is still needed to understand further the interaction of SAR signals with forest canopy and to develop an operational method for forestry applications. This work discusses the use of repeat pass interferometry with ALOS PALSAR (L band) HH polarized and COSMO Skymed (X band) HH polarized acquisitions over the Taxiarchis forest (Chalkidiki, Greece), in order to produce accurate digital elevation models (DEMs) and estimate canopy height with interferometric processing. The effect of wavelength-dependent penetration depth into the canopy is known to be strong, and could potentially lead to forest canopy height mapping using dual-wavelength SAR interferometry at X- and L-band. The method is based on scattering phase center separation at different wavelengths. It involves the generation of a terrain elevation model underneath the forest canopy from repeat-pass L-band InSAR data as well as the generation of a canopy surface elevation model from repeat pass X-band InSAR data. The terrain model is then used to remove the terrain component from the repeat pass interferometric X-band elevation model, so as to enable the forest canopy height estimation. The canopy height results were compared to a field survey with 6.9 m root mean square error (RMSE). The effects of vegetation characteristics, SAR incidence angle and view geometry, and terrain slope on the accuracy of the results have also been studied in this work.

Recovery of forest structure and spectral properties after selective logging in lowland Bolivia.

PubMed

Broadbent, Eben N; Zarin, Daniel J; Asner, Gregory P; Peña-Claros, Marielos; Cooper, Amanda; Littell, Ramon

2006-06-01

Effective monitoring of selective logging from remotely sensed data requires an understanding of the spatial and temporal thresholds that constrain the utility of those data, as well as the structural and ecological characteristics of forest disturbances that are responsible for those constraints. Here we assess those thresholds and characteristics within the context of selective logging in the Bolivian Amazon. Our study combined field measurements of the spatial and temporal dynamics of felling gaps and skid trails ranging from <1 to 19 months following reduced-impact logging in a forest in lowland Bolivia with remote-sensing measurements from simultaneous monthly ASTER satellite overpasses. A probabilistic spectral mixture model (AutoMCU) was used to derive per-pixel fractional cover estimates of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil. Results were compared with the normalized difference in vegetation index (NDVI). The forest studied had considerably lower basal area and harvest volumes than logged sites in the Brazilian Amazon where similar remote-sensing analyses have been performed. Nonetheless, individual felling-gap area was positively correlated with canopy openness, percentage liana coverage, rates of vegetation regrowth, and height of remnant NPV. Both liana growth and NPV occurred primarily in the crown zone of the felling gap, whereas exposed soil was limited to the trunk zone of the gap. In felling gaps >400 m2, NDVI, and the PV and NPV fractions, were distinguishable from unlogged forest values for up to six months after logging; felling gaps <400 m2 were distinguishable for up to three months after harvest, but we were entirely unable to distinguish skid trails from our analysis of the spectral data.

Cascading Effects of Canopy Opening and Debris Deposition from a Large-Scale Hurricane Experiment in a Tropical Rain Forest

Treesearch

Aaron B. Shiels; Grizelle Gonzalez; D. Jean Lodge; Michael R Willig; Jess K. Zimmerman

2015-01-01

Intense hurricanes disturb many tropical forests, but the key mechanisms driving post-hurricane forest changes are not fully understood. In Puerto Rico, we used a replicated factorial experiment to determine the mechanisms of forest change associated with canopy openness and organic matter (debris) addition. Cascading effects from canopy openness accounted for...

A stem-map model for predicting tree canopy cover of Forest Inventory and Analysis (FIA) plots

Treesearch

Chris Toney; John D. Shaw; Mark D. Nelson

2009-01-01

Tree canopy cover is an important stand characteristic that affects understory light, fuel moisture, decomposition rates, wind speed, and wildlife habitat. Canopy cover also is a component of most definitions of forest land used by US and international agencies. The USDA Forest Service Forest Inventory and Analysis (FIA) Program currently does not provide a national...

A comparison of forest canopy models derived from LIDAR and INSAR data in a Pacific Northwest conifer forest.

Treesearch

Hans-Erik Andersen; Robert J. McGaughey; Ward W. Carson; Stephen E. Reutebuch; Bryan Mercer; Jeremy Allan

2004-01-01

Active remote sensing technologies, including interferometric radar (InSAR) and airborne laser scanning (LIDAR) have the potential to provide accurate information relating to three-dimensional forest canopy structure over extensive areas of the landscape. In order to assess the capabilities of these alternative systems for characterizing the forest canopy dimensions,...

Mapping canopy gap fraction and leaf area index at continent-scale from satellite lidar

NASA Astrophysics Data System (ADS)

Mahoney, C.; Hopkinson, C.; Held, A. A.

2015-12-01

Information on canopy cover is essential for understanding spatial and temporal variability in vegetation biomass, local meteorological processes and hydrological transfers within vegetated environments. Gap fraction (GF), an index of canopy cover, is often derived over large areas (100's km2) via airborne laser scanning (ALS), estimates of which are reasonably well understood. However, obtaining country-wide estimates is challenging due to the lack of spatially distributed point cloud data. The Geoscience Laser Altimeter System (GLAS) removes spatial limitations, however, its large footprint nature and continuous waveform data measurements make derivations of GF challenging. ALS data from 3 Australian sites are used as a basis to scale-up GF estimates to GLAS footprint data by the use of a physically-based Weibull function. Spaceborne estimates of GF are employed in conjunction with supplementary predictor variables in the predictive Random Forest algorithm to yield country-wide estimates at a 250 m spatial resolution; country-wide estimates are accompanied with uncertainties at the pixel level. Preliminary estimates of effective Leaf Area Index (eLAI) are also presented by converting GF via the Beer-Lambert law, where an extinction coefficient of 0.5 is employed; deemed acceptable at such spatial scales. The need for such wide-scale quantification of GF and eLAI are key in the assessment and modification of current forest management strategies across Australia. Such work also assists Australia's Terrestrial Ecosystem Research Network (TERN), a key asset to policy makers with regards to the management of the national ecosystem, in fulfilling their government issued mandates.

Attaining the canopy in dry and moist tropical forests: strong differences in tree growth trajectories reflect variation in growing conditions.

PubMed

Brienen, Roel J W; Zuidema, Pieter A; Martínez-Ramos, Miguel

2010-06-01

Availability of light and water differs between tropical moist and dry forests, with typically higher understorey light levels and lower water availability in the latter. Therefore, growth trajectories of juvenile trees--those that have not attained the canopy--are likely governed by temporal fluctuations in light availability in moist forests (suppressions and releases), and by spatial heterogeneity in water availability in dry forests. In this study, we compared juvenile growth trajectories of Cedrela odorata in a dry (Mexico) and a moist forest (Bolivia) using tree rings. We tested the following specific hypotheses: (1) moist forest juveniles show more and longer suppressions, and more and stronger releases; (2) moist forest juveniles exhibit wider variation in canopy accession pattern, i.e. the typical growth trajectory to the canopy; (3) growth variation among dry forest juveniles persists over longer time due to spatial heterogeneity in water availability. As expected, the proportion of suppressed juveniles was higher in moist than in dry forest (72 vs. 17%). Moist forest suppressions also lasted longer (9 vs. 5 years). The proportion of juveniles that experienced releases in moist forest (76%) was higher than in dry forest (41%), and releases in moist forests were much stronger. Trees in the moist forest also had a wider variation in canopy accession patterns compared to the dry forest. Our results also showed that growth variation among juvenile trees persisted over substantially longer periods of time in dry forest (>64 years) compared to moist forest (12 years), most probably because of larger persistent spatial variation in water availability. Our results suggest that periodic increases in light availability are more important for attaining the canopy in moist forests, and that spatial heterogeneity in water availability governs long-term tree growth in dry forests.

Estimating canopy cover from standard forest inventory measurements in western Oregon

Treesearch

Anne McIntosh; Andrew Gray; Steven. Garman

2012-01-01

Reliable measures of canopy cover are important in the management of public and private forests. However, direct sampling of canopy cover is both labor- and time-intensive. More efficient methods for estimating percent canopy cover could be empirically derived relationships between more readily measured stand attributes and canopy cover or, alternatively, the use of...

Airborne remote sensing of forest biomes

NASA Technical Reports Server (NTRS)

Sader, Steven A.

1987-01-01

Airborne sensor data of forest biomes obtained using an SAR, a laser profiler, an IR MSS, and a TM simulator are presented and examined. The SAR was utilized to investigate forest canopy structures in Mississippi and Costa Rica; the IR MSS measured forest canopy temperatures in Oregon and Puerto Rico; the TM simulator was employed in a tropical forest in Puerto Rico; and the laser profiler studied forest canopy characteristics in Costa Rica. The advantages and disadvantages of airborne systems are discussed. It is noted that the airborne sensors provide measurements applicable to forest monitoring programs.

Persistent effects of a severe drought on Amazonian forest canopy

PubMed Central

Saatchi, Sassan; Asefi-Najafabady, Salvi; Malhi, Yadvinder; Aragão, Luiz E. O. C.; Anderson, Liana O.; Myneni, Ranga B.; Nemani, Ramakrishna

2013-01-01

Recent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate perturbations. Satellite and in situ observations have shown an increase in fire occurrence during drought years and tree mortality following severe droughts, but to date there has been no assessment of long-term impacts of these droughts across landscapes in Amazonia. Here, we use satellite microwave observations of rainfall and canopy backscatter to show that more than 70 million hectares of forest in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy structure and moisture. Remarkably, and despite the gradual recovery in total rainfall in subsequent years, the decrease in canopy backscatter persisted until the next major drought, in 2010. The decline in backscatter is attributed to changes in structure and water content associated with the forest upper canopy. The persistence of low backscatter supports the slow recovery (>4 y) of forest canopy structure after the severe drought in 2005. The result suggests that the occurrence of droughts in Amazonia at 5–10 y frequency may lead to persistent alteration of the forest canopy. PMID:23267086

Towards Linking 3D SAR and Lidar Models with a Spatially Explicit Individual Based Forest Model

NASA Astrophysics Data System (ADS)

Osmanoglu, B.; Ranson, J.; Sun, G.; Armstrong, A. H.; Fischer, R.; Huth, A.

2017-12-01

In this study, we present a parameterization of the FORMIND individual-based gap model (IBGM)for old growth Atlantic lowland rainforest in La Selva, Costa Rica for the purpose of informing multisensor remote sensing techniques for above ground biomass techniques. The model was successfully parameterized and calibrated for the study site; results show that the simulated forest reproduces the structural complexity of Costa Rican rainforest based on comparisons with CARBONO inventory plot data. Though the simulated stem numbers (378) slightly underestimated the plot data (418), particularly for canopy dominant intermediate shade tolerant trees and shade tolerant understory trees, overall there was a 9.7% difference. Aboveground biomass (kg/ha) showed a 0.1% difference between the simulated forest and inventory plot dataset. The Costa Rica FORMIND simulation was then used to parameterize a spatially explicit (3D) SAR and lidar backscatter models. The simulated forest stands were used to generate a Look Up Table as a tractable means to estimate aboveground forest biomass for these complex forests. Various combinations of lidar and radar variables were evaluated in the LUT inversion. To test the capability of future data for estimation of forest height and biomass, we considered data of 1) L- (or P-) band polarimetric data (backscattering coefficients of HH, HV and VV); 2) L-band dual-pol repeat-pass InSAR data (HH/HV backscattering coefficients and coherences, height of scattering phase center at HH and HV using DEM or surface height from lidar data as reference); 3) P-band polarimetric InSAR data (canopy height from inversion of PolInSAR data or use the coherences and height of scattering phase center at HH, HV and VV); 4) various height indices from waveform lidar data); and 5) surface and canopy top height from photon-counting lidar data. The methods for parameterizing the remote sensing models with the IBGM and developing Look Up Tables will be discussed. Results from various remote sensing scenarios will also be presented.

Forest management in Earth system modelling: a vertically discretised canopy description for ORCHIDEE and the modifications to the energy, water and carbon fluxes

NASA Astrophysics Data System (ADS)

Naudts, Kim; Ryder, James; McGrath, Matthew J.; Otto, Juliane; Chen, Yiying; Valade, Aude; Bellasen, Valentin; Ghattas, Josefine; Haverd, Vanessa; MacBean, Natasha; Maignan, Fabienne; Peylin, Philippe; Pinty, Bernard; Solyga, Didier; Vuichard, Nicolas; Luyssaert, Sebastiaan

2015-04-01

Since 70% of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land surface models used in Earth system models, and therefore none of today's predictions of future climate, account for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrizing a version of the land surface model ORCHIDEE to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new model called ORCHIDEE-CAN and the standard version of ORCHIDEE are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes towards a better process representation occurred for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrization was revisited after introducing twelve new parameter sets that represent specific tree species or genera rather than a group of unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, GPP, albedo and evapotranspiration over Europe. For all tested variables ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92% chance to reproduce the spatial and temporal variability of the validation data.

Isotopic characteristics of canopies in simulated leaf assemblages

NASA Astrophysics Data System (ADS)

Graham, Heather V.; Patzkowsky, Mark E.; Wing, Scott L.; Parker, Geoffrey G.; Fogel, Marilyn L.; Freeman, Katherine H.

2014-11-01

The geologic history of closed-canopy forests is of great interest to paleoecologists and paleoclimatologists alike. Closed canopies have pronounced effects on local, continental and global rainfall and temperature patterns. Although evidence for canopy closure is difficult to reconstruct from the fossil record, the characteristic isotope gradients of the ;canopy effect; could be preserved in leaves and proxy biomarkers. To assess this, we employed new carbon isotopic data for leaves collected in diverse light environments within a deciduous, temperate forest (Maryland, USA) and for leaves from a perennially closed canopy, moist tropical forest (Bosque Protector San Lorenzo, Panamá). In the tropical forest, leaf carbon isotope values range 10‰, with higher δ13Cleaf values occurring both in upper reaches of the canopy, and with higher light exposure and lower humidity. Leaf fractionation (Δleaf) varied negatively with height and light and positively with humidity. Vertical 13C enrichment in leaves largely reflects changes in Δleaf, and does not trend with δ13C of CO2 within the canopy. At the site in Maryland, leaves express a more modest δ13C range (∼6‰), with a clear trend that follows both light and leaf height. Using a model we simulate leaf assemblage isotope patterns from canopy data binned by elevation. The re-sampling (bootstrap) model determined both the mean and range of carbon isotope values for simulated leaf assemblages ranging in size from 10 to over 1000 leaves. For the tropical forest data, the canopy's isotope range is captured with 50 or more randomly sampled leaves. Thus, with a sufficient number of fossil leaves it is possible to distinguish isotopic gradients in an ancient closed canopy forest from those in an open forest. For very large leaf assemblages, mean isotopic values approximate the δ13C of carbon contributed by leaves to soil and are similar to observed δ13Clitter values at forested sites within Panamá, including the site where leaves were sampled. The model predicts a persistent ∼1‰ difference in δ13Clitter for the two sites which is consistent with higher water availability in the tropical forests. This work provides a new framework for linking contemporary ecological observations to the geochemical record using flux-weighted isotope data and lends insights to the effect of forest architecture on organic and isotopic records of ancient terrestrial ecosystems. How many leaves from a litter assemblage are necessary to distinguish the isotopic gradient characteristics of canopy closure? Are mean δ13Cleaf values for a litter assemblage diagnostic of a forest biome? Can we predict the δ13C values of cumulative litter, soil organic matter, and organic carbon in sedimentary archives using litter flux and isotope patterns in canopies? We determined the δ13C range and mean for different sized assemblages of leaves sampled from data for each forest. We re-sampled very high numbers of leaves in order to estimate the isotopic composition of cumulative carbon delivered to soils as litter, and compared these results to available data from forest soils. Modeled leaf and soil organic carbon isotope patterns in this study offer insights to how forest structure can be derived from carbon isotope measurements of fossil leaves, as well as secondary material - such as teeth, hair, paleosol carbonates, or organic soil carbon (van der Merwe and Medina, 1989; Koch, 1998; Secord et al., 2008; Levin et al., 2011).Distinct climate and seasonal difference in the Panamá and Maryland, USA forests are reflected in their canopy isotope gradients. In the tropical forest of Panamá, leaves are produced throughout the year within a canopy that is both extensively and persistently closed (Leigh, 1975; Lowman and Wittman, 1996). In the temperate forest of Maryland leaves are produced during the spring when canopy conditions are relatively open (Korner and Basler, 2010).

A canopy trimming experiment in Puerto Rico: the response of litter invertebrate communities to canopy loss and debris deposition in a tropical forest subject to hurricanes

Treesearch

Barbara A. Richardson; Michael J. Richardson; Grizelle Gonzalez; Aaron B. Shiels; Diane S. Srivastava

2010-01-01

Hurricanes cause canopy removal and deposition of pulses of litter to the forest floor. A Canopy Trimming Experiment (CTE) was designed to decouple these two factors, and to investigate the separate abiotic and biotic consequences of hurricane-type damage and monitor recovery processes. As part of this experiment, effects on forest floor invertebrate communities were...

Estimation of tropical forest canopy temperatures, thermal response numbers, and evapotranspiration using an aircraft-based thermal sensor

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Lieberman, Diana; Lieberman, Milton; Hartshorn, Gary S.; Peralta, Rodolfo

1990-01-01

Thermal infrared Multispectral Scanner (TIMS) data were collected at a resolution of 5 to 10 m from a tropical rain forest over an elevation gradient from 35 to 2700 m in the Braulio Carrillo National Park in Costa Rica. Flight lines were repeated with a 15 to 30 minute time difference for measurement of forest canopy thermal response over time. Concurrent radiosonde measurements of atmospheric profiles of air temperature and moisture provided inputs to LOWTRAN6 for atmospheric radiance corrections of the TIMS data. Techniques for using calibrated aircraft-based thermal scanner data to examine tropical forest canopy thermal properties are described. Forest canopy temperature changes over time assessed between repeated, duplicated flight lines were combined with estimates of surface radiative energy measurements from towers above the forest canopy to determine temperature spatial variability, calculate Thermal Response Numbers (TRN), and estimate evapotranspiration along the elevation gradient from selected one hectare forest inventory plots.

Canopy soil bacterial communities altered by severing host tree limbs

PubMed Central

Dangerfield, Cody R.; Nadkarni, Nalini M.

2017-01-01

Trees of temperate rainforests host a large biomass of epiphytic plants, which are associated with soils formed in the forest canopy. Falling of epiphytic material results in the transfer of carbon and nutrients from the canopy to the forest floor. This study provides the first characterization of bacterial communities in canopy soils enabled by high-depth environmental sequencing of 16S rRNA genes. Canopy soil included many of the same major taxonomic groups of Bacteria that are also found in ground soil, but canopy bacterial communities were lower in diversity and contained different operational taxonomic units. A field experiment was conducted with epiphytic material from six Acer macrophyllum trees in Olympic National Park, Washington, USA to document changes in the bacterial communities of soils associated with epiphytic material that falls to the forest floor. Bacterial diversity and composition of canopy soil was highly similar, but not identical, to adjacent ground soil two years after transfer to the forest floor, indicating that canopy bacteria are almost, but not completely, replaced by ground soil bacteria. Furthermore, soil associated with epiphytic material on branches that were severed from the host tree and suspended in the canopy contained altered bacterial communities that were distinct from those in canopy material moved to the forest floor. Therefore, the unique nature of canopy soil bacteria is determined in part by the host tree and not only by the physical environmental conditions associated with the canopy. Connection to the living tree appears to be a key feature of the canopy habitat. These results represent an initial survey of bacterial diversity of the canopy and provide a foundation upon which future studies can more fully investigate the ecological and evolutionary dynamics of these communities. PMID:28894646

Canopy soil bacterial communities altered by severing host tree limbs.

PubMed

Dangerfield, Cody R; Nadkarni, Nalini M; Brazelton, William J

2017-01-01

Trees of temperate rainforests host a large biomass of epiphytic plants, which are associated with soils formed in the forest canopy. Falling of epiphytic material results in the transfer of carbon and nutrients from the canopy to the forest floor. This study provides the first characterization of bacterial communities in canopy soils enabled by high-depth environmental sequencing of 16S rRNA genes. Canopy soil included many of the same major taxonomic groups of Bacteria that are also found in ground soil, but canopy bacterial communities were lower in diversity and contained different operational taxonomic units. A field experiment was conducted with epiphytic material from six Acer macrophyllum trees in Olympic National Park, Washington, USA to document changes in the bacterial communities of soils associated with epiphytic material that falls to the forest floor. Bacterial diversity and composition of canopy soil was highly similar, but not identical, to adjacent ground soil two years after transfer to the forest floor, indicating that canopy bacteria are almost, but not completely, replaced by ground soil bacteria. Furthermore, soil associated with epiphytic material on branches that were severed from the host tree and suspended in the canopy contained altered bacterial communities that were distinct from those in canopy material moved to the forest floor. Therefore, the unique nature of canopy soil bacteria is determined in part by the host tree and not only by the physical environmental conditions associated with the canopy. Connection to the living tree appears to be a key feature of the canopy habitat. These results represent an initial survey of bacterial diversity of the canopy and provide a foundation upon which future studies can more fully investigate the ecological and evolutionary dynamics of these communities.

Overstory and Understory CO2 and Energy Fluxes of a Black Spruce Forest in Interior Alaska

NASA Astrophysics Data System (ADS)

Ikawa, H.; Nakai, T.; Busey, R.; Kim, Y.; Kobayashi, H.; Nagai, S.; Ueyama, M.; Saito, K.; Suzuki, R.; Hinzman, L. D.

2014-12-01

Eddy covariance techniques were used to quantify understory contributions to carbon and energy balances, and to evaluate the environmental responses of the overstory and understory at a black spruce forest in interior Alaska. Net ecosystem productivity (NEP), gross primary productivity (GPP), ecosystem respiration (RE), sensible heat flux (H), and latent heat flux (LE) were estimated for the ecosystem (subscripted by 'eco'), canopy (subscripted by 'cano') and forest floor (subscripted by 'floor') based on canopy gap fraction and footprint analyses for 3 years, 2011 - 2013. Fluxes per unit land surface area of black spruce overstory (subscripted by 'b') and that of understory (subscripted by 'u') were also evaluated their ecophysiological responses to micrometeorological environments. Overall, NEPfloor, GPPfloor, REfloor and LEfloor represented 60 (37, growing season in parenthesis) %, 47 (51) %, 47 (54) %, and 75 (76) % of NEPeco, GPPeco, REeco, and LEeco, respectively with the average canopy gap fraction of 0.52 (± 0.073 SD). The year, 2013 was characterized by high air temperature and vapor pressure deficit (VPD) during the growing season. The high temperature and VPD particularly reduced understory NEP and their growth inferred by low green excessive index (GEI), which was correlated to GPPu more strongly than GPPb. LEu linearly increased with vapor pressure deficit (VPD) whereas LEb was insensitive to VPD. Future warming and drying expected in the boreal forest will increase understory evapotranspiration disproportionately to that of black spruce and likely decrease the production of the current understory community. Acknowledgments This study was supported by the Japan Aerospace Exploration Agency (JAXA) and the JAMSTEC-IARC Collaboration Study, with funding provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) to the International Arctic Research Center (IARC). The Polar Geospatial Center, University of Minnesota provided the Quick Bird Image as a support for the NSF grand number 1107524. HI acknowledges J. H. Matthes for helping the footprint algorism, R. Hirata, D. McGuire, and E. Euskirchen for fruitful discussion, and Y. Harazono and H. Nagano for providing parts of meteorological data. We thank N. Bauer for editing.

Assessing urban forest canopy cover using airborne or satellite imagery

Treesearch

Jeffrey T. Walton; David J. Nowak; Eric J. Greenfield

2008-01-01

With the availability of many sources of imagery and various digital classification techniques, assessing urban forest canopy cover is readily accessible to most urban forest managers. Understanding the capability and limitations of various types of imagery and classification methods is essential to interpreting canopy cover values. An overview of several remote...

Gainesville's urban forest canopy cover

Treesearch

Francisco Escobedo; Jennifer A. Seitz; Wayne Zipperer

2009-01-01

Ecosystem benefits from trees are linked directly to the amount of healthy urban forest canopy cover. Urban forest cover is dynamic and changes over time due to factors such as urban development, windstorms, tree removals, and growth. The amount of a city's canopy cover depends on its land use, climate, and people's preferences. This fact sheet examines how...

Tree canopy types constrain plant distributions in ponderosa pine-Gambel oak forests, northern Arizona

Treesearch

Scott R. Abella

2009-01-01

Trees in many forests affect the soils and plants below their canopies. In current high-density southwestern ponderosa pine (Pinus ponderosa) forests, managers have opportunities to enhance multiple ecosystem values by manipulating tree density, distribution, and canopy cover through tree thinning. I performed a study in northern Arizona ponderosa...

Forest canopy structural properties. Chapter 14

Treesearch

Marie-Louise Smith; Jeanne Anderson; Matthew Fladeland

2008-01-01

The forest canopy is the interface between the land and the atmosphere, fixing atmospheric carbon into biomass and releasing oxygen and water. The arrangement of individual trees, differences in species morphology, the availability of light and soil nutrients, and many other factors determine canopy structure. Overviews of approaches for basic measurements of canopy...

Evaporation and the sub-canopy energy environment in a flooded forest

USDA-ARS?s Scientific Manuscript database

The combination of canopy cover and a free water surface makes the sub-canopy environment of flooded forested wetlands unlike other aquatic or terrestrial systems. The sub-canopy vapor flux and energy budget are not well understood in wetlands, but they importantly control water level and understory...

Post-Hurricane Successional Dynamics in Abundance and Diversity of Canopy Arthropods in a Tropical Rainforest.

PubMed

Schowalter, T D; Willig, M R; Presley, S J

2017-02-01

We quantified long-term successional trajectories of canopy arthropods on six tree species in a tropical rainforest ecosystem in the Luquillo Mountains of Puerto Rico that experienced repeated hurricane-induced disturbances during the 19-yr study (1991-2009). We expected: 1) differential performances of arthropod species to result in taxon- or guild-specific responses; 2) differences in initial conditions to result in distinct successional responses to each hurricane; and 3) the legacy of hurricane-created gaps to persist despite subsequent disturbances. At least one significant effect of gap, time after hurricane, or their interaction occurred for 53 of 116 analyses of taxon abundance, 31 of 84 analyses of guild abundance, and 21 of 60 analyses of biodiversity (e.g., richness, evenness, dominance, and rarity). Significant responses were ∼60% more common for time after hurricane than for gap creation, indicating that temporal changes in habitat during recovery were of primary importance. Both increases and decreases in abundance or diversity occurred in response to each factor. Guild-level responses were probably driven by changes in the abundance of resources on which they rely. For example, detritivores were most abundant soon after hurricanes when litter resources were elevated, whereas sap-suckers were most abundant in gaps where new foliage growth was the greatest. The legacy of canopy gaps created by Hurricane Hugo persisted for at least 19 yr, despite droughts and other hurricanes of various intensities that caused forest damage. This reinforces the need to consider historical legacies when seeking to understand responses to disturbance. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The effects of phenoseason and storm characteristics on throughfall solute washoff and leaching dynamics from a temperate deciduous forest canopy.

PubMed

Van Stan, John T; Levia, Delphis F; Inamdar, Shreeram P; Lepori-Bui, Michelle; Mitchell, Myron J

2012-07-15

Seasonal variations in the washoff and leaching dynamics of throughfall ionic fluxes represent a significant process affecting the biogeochemical cycling of forested ecosystems-particularly for temperate deciduous forests with distinct phenological seasons (or "phenoseasons"). Most studies on temperate deciduous forests aggregate seasonal throughfall fluxes to the leafed (growing) and leafless (dormant) periods, yet the phenological conditions controlling seasonality demand finer-scale demarcations that include the transitional phenoseasons (leaf senescence and emergence). To fill these gaps our study examines the washoff and leaching dynamics of Na(+), Mg(2+), K(+), Ca(2+), Cl(-), SO(4)(2-), and NO(3)(-) throughfall derived from bulk and sequentially sampled rain events across leafed, leafless and both transitional phenoseasons over a 3-year period (2008-2010). As throughfall washoff and leached solute fluxes are also closely-coupled to rainfall conditions, we further examine the effects of storm characteristics on phenoseasonal washoff-dominated (Na(+) and Cl(-)) and leaching-dominated (K(+), Ca(2+), Mg(2+)) fluxes through intrastorm event comparison plots and factorial MANOVA. Highly significant differences in leached and washoff solute fluxes were found across meteorological conditions (p<0.001) nested within phenoseasonal divisions (p<0.00001). Phenoseasonal washoff Na(+) and Cl(-) fluxes seemed to be more closely related to leaf area; whereas, leaching flux and canopy exchange of all solutes to correspond more with major phenological changes (when the canopies tend to be most metabolically active). The greatest differences in leached Mg(2+), K(+), Ca(2+), and SO(4)(2-) fluxes were not between the full leafed and leafless phenoseasons (33-80% difference), but between the transitional periods (80 to 200 fold greater during leaf senescence than leaf emergence). Intrastorm average canopy NO(3)(-) leaching, however, ranged from low losses (1 μmol(c)m(-2)h(-1)) to canopy uptake (-2 μmol(c)m(-2)h(-1)) during both transitional phenoseasons. K(+), Ca(2+), Mg(2+) were all markedly more exchangeable during senescence, with Ca(2+) and Mg(2+) being more tightly held by the canopy. Leaching rates and fluxes for all measured solutes were negligible to negative during emergence, except for K(+) and SO(4)(2-). Our results indicate that much of the variance in timing and magnitude of throughfall solute fluxes to forest soils within temperate deciduous ecosystems may be ascribed to phenologically-delineated seasons and storm conditions. Copyright © 2012 Elsevier B.V. All rights reserved.

Investigation into the role of canopy structure traits and plant functional types in modulating the correlation between canopy nitrogen and reflectance in a temperate forest in northeast China

NASA Astrophysics Data System (ADS)

Yu, Quanzhou; Wang, Shaoqiang; Zhou, Lei

2017-10-01

A precise estimate of canopy leaf nitrogen concentration (CNC, based on dry mass) is important for researching the carbon assimilation capability of forest ecosystems. Hyperspectral remote sensing technology has been applied to estimate regional CNC, which can adjust forest photosynthetic capacity and carbon uptake. However, the relationship between forest CNC and canopy spectral reflectance as well as its mechanism is still poorly understood. Using measured CNC, canopy structure and species composition data, four vegetation indices (VIs), and near-infrared reflectance (NIR) derived from EO-1 Hyperion imagery, we investigated the role of canopy structure traits and plant functional types (PFTs) in modulating the correlation between CNC and canopy reflectance in a temperate forest in northeast China. A plot-scale forest structure indicator, named broad foliar dominance index (BFDI), was introduced to provide forest canopy structure and coniferous and broadleaf species composition. Then, we revealed the response of forest canopy reflectance spectrum to BFDI and CNC. Our results showed that leaf area index had no significant effect on NIR (P>0.05) but indicated that there was a significant correlation (R2=0.76, P<0.0001) between CNC and BFDI. NIR had a more significant correlation with BFDI than with CNC for all PFTs, but it had no obvious correlation with CNC for single PFT. Partial correlation analysis showed that four VIs had better correlations with BFDI than with CNC. When the effect of BFDI was removed, the partial correlation between CNC and NIR was insignificant (R=0.273, P>0.05). On the contrary, removing the CNC effect, the partial correlation between BFDI and NIR was positively significant (R=0.69, P<0.0001). These findings proved that canopy structure and coniferous and broadleaf species composition had a greater influence on the remote sensing signal than canopy nitrogen concentration. The functional convergence of plant traits resulted in the relation of CNC and canopy structure and determined the positive correlation between CNC and NIR. We maintain that the repeatable relationship between CNC and NIR can be used in the remote sensing retrieval of CNC during various forest types. Nevertheless, the relationship cannot be considered as a feasible approach of CNC estimation for a single PFT.

Impacts of Water Stress on Forest Recovery and Its Interaction with Canopy Height.

PubMed

Xu, Peipei; Zhou, Tao; Yi, Chuixiang; Luo, Hui; Zhao, Xiang; Fang, Wei; Gao, Shan; Liu, Xia

2018-06-13

Global climate change is leading to an increase in the frequency, intensity, and duration of drought events, which can affect the functioning of forest ecosystems. Because human activities such as afforestation and forest attributes such as canopy height may exhibit considerable spatial differences, such differences may alter the recovery paths of drought-impacted forests. To accurately assess how climate affects forest recovery, a quantitative evaluation on the effects of forest attributes and their possible interaction with the intensity of water stress is required. Here, forest recovery following extreme drought events was analyzed for Yunnan Province, southwest China. The variation in the recovery of forests with different water availability and canopy heights was quantitatively assessed at the regional scale by using canopy height data based on light detection and ranging (LiDAR) measurements, enhanced vegetation index data, and standardized precipitation evapotranspiration index (SPEI) data. Our results indicated that forest recovery was affected by water availability and canopy height. Based on the enhanced vegetation index measures, shorter trees were more likely to recover than taller ones after drought. Further analyses demonstrated that the effect of canopy height on recovery rates after drought also depends on water availability—the effect of canopy height on recovery diminished as water availability increased after drought. Additional analyses revealed that when the water availability exceeded a threshold (SPEI > 0.85), no significant difference in the recovery was found between short and tall trees ( p > 0.05). In the context of global climate change, future climate scenarios of RCP2.6 and RCP8.5 showed more frequent water stress in Yunnan by the end of the 21st century. In summary, our results indicated that canopy height casts an important influence on forest recovery and tall trees have greater vulnerability and risk to dieback and mortality from drought. These results may have broad implications for policies and practices of forest management.

Diversity of Bats in Contrasting Habitats of Hulu Terengganu Dipterocarp Forest and Setiu Wetland BRIS Forest with a Note on Preliminary Study of Vertical Stratification of Pteropodid Bats.

PubMed

Pounsin, Grace; Wahab, Nur Syahirah; Roslan, Azuan; Zahidin, Muhamad Aidil; Pesiu, Elizabeth; Tamrin, Nur Aida Md; Abdullah, M T

2018-03-01

A study of the bat diversity was conducted in Hulu Terengganu dipterocarp forest and Setiu Wetland Beach Ridges Interspersed with Swales (BRIS) forest in Terengganu, to study the species diversity, composition and stratification of fruit bats from the understorey to the forest canopy. Mist nets were set up at the understorey, sub-canopy and canopy layer while harp traps were set up at the understorey layer. We recorded 170 individuals from six families' compromised 21 species from Hulu Terengganu dipterocarp forests and four species from Setiu Wetland BRIS forests throughout the sampling period. Megaerops ecaudatus and Cynopterus brachyotis were the most dominant species in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forests. Our study also recorded two species with new distributional records for the east coast of Peninsular Malaysia, namely, Rhinolophus chiewkweeae and Chaerephon johorensis in Hulu Terengganu dipterocarp forests. Potential factors that might influence the results were in terms of the canopy covers, the structural complexity of canopy, food availability and spatial characteristics. This study was able to increase the knowledge on the species diversity and composition of bats in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forest, thus, further aid in the effort of bat conservation in both areas.

Modeling a historical mountain pine beetle outbreak using Landsat MSS and multiple lines of evidence

USGS Publications Warehouse

Assal, Timothy J.; Sibold, Jason; Reich, Robin M.

2014-01-01

Mountain pine beetles are significant forest disturbance agents, capable of inducing widespread mortality in coniferous forests in western North America. Various remote sensing approaches have assessed the impacts of beetle outbreaks over the last two decades. However, few studies have addressed the impacts of historical mountain pine beetle outbreaks, including the 1970s event that impacted Glacier National Park. The lack of spatially explicit data on this disturbance represents both a major data gap and a critical research challenge in that wildfire has removed some of the evidence from the landscape. We utilized multiple lines of evidence to model forest canopy mortality as a proxy for outbreak severity. We incorporate historical aerial and landscape photos, aerial detection survey data, a nine-year collection of satellite imagery and abiotic data. This study presents a remote sensing based framework to (1) relate measurements of canopy mortality from fine-scale aerial photography to coarse-scale multispectral imagery and (2) classify the severity of mountain pine beetle affected areas using a temporal sequence of Landsat data and other landscape variables. We sampled canopy mortality in 261 plots from aerial photos and found that insect effects on mortality were evident in changes to the Normalized Difference Vegetation Index (NDVI) over time. We tested multiple spectral indices and found that a combination of NDVI and the green band resulted in the strongest model. We report a two-step process where we utilize a generalized least squares model to account for the large-scale variability in the data and a binary regression tree to describe the small-scale variability. The final model had a root mean square error estimate of 9.8% canopy mortality, a mean absolute error of 7.6% and an R2 of 0.82. The results demonstrate that a model of percent canopy mortality as a continuous variable can be developed to identify a gradient of mountain pine beetle severity on the landscape.

The effect of interspecific variation in photosynthetic plasticity on 4-year growth rate and 8-year survival of understorey tree seedlings in response to gap formations in a cool-temperate deciduous forest.

PubMed

Oguchi, Riichi; Hiura, Tsutom; Hikosaka, Kouki

2017-08-01

Gap formation increases the light intensity in the forest understorey. The growth responses of seedlings to the increase in light availability show interspecific variation, which is considered to promote biodiversity in forests. At the leaf level, some species increase their photosynthetic capacity in response to gap formation, whereas others do not. Here we address the question of whether the interspecific difference in the photosynthetic response results in the interspecific variation in the growth response. If so, the interspecific difference in photosynthetic response would also contribute to species coexistence in forests. We also address the further relevant question of why some species do not increase their photosynthetic capacity. We assumed that some cost of photosynthetic plasticity may constrain acquisition of the plasticity in some species, and hypothesized that species with larger photosynthetic plasticity exhibit better growth after gap formation and lower survivorship in the shade understorey of a cool-temperate deciduous forest. We created gaps by felling canopy trees and studied the relationship between the photosynthetic response and the subsequent growth rate of seedlings. Naturally growing seedlings of six deciduous woody species were used and their mortality was examined for 8 years. The light-saturated rate of photosynthesis (Pmax) and the relative growth rate (RGR) of the seedlings of all study species increased at gap plots. The extent of these increases varied among the species. The stimulation of RGR over 4 years after gap formation was strongly correlated with change in photosynthetic capacity of newly expanded leaves. The increase in RGR and Pmax correlated with the 8-year mortality at control plots. These results suggest a trade-off between photosynthetic plasticity and the understorey shade tolerance. Gap-demanding species may acquire photosynthetic plasticity, sacrificing shade tolerances, whereas gap-independent species may acquire shade tolerances, sacrificing photosynthetic plasticity. This strategic difference among species would contribute to species coexistence in cool-temperate deciduous forests. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Monitoring tree health with a dual-wavelength terrestrial laser scanner

NASA Astrophysics Data System (ADS)

Hancock, S.

2013-12-01

Steven Hancock1, Rachel Gaulton1, Mark Danson2 1School of Civil Engineering and Geosciences, Newcastle University, UK, steven.hancock@ncl.ac.uk, rachel.gaulton@ncl.ac.uk 2 School of Environment and Life Sciences, University of Salford, UK, F.M.Danson@salford.ac.uk Forests are a vital part of the Earth's carbon cycle and drive interactions between the land and atmosphere. Accurate and repeatable measurement of forests is essential for understanding the Earth system. Terrestrial laser scanning can be a powerful tool for characterising forests. However, there are a number of issues that have yet to be resolved. Commercial laser scanners are optimised for measuring buildings and other hard targets. Vegetation canopies are complex and porous, confounding standard interpretation techniques. Commercial systems struggle with partial hits and cannot distinguish leaf from wood (Danson et al 2007). A new generation of terrestrial laser scanners, optimised for vegetation measurement, are in development. The Salford Advanced Laser Canopy Analyser (SALCA, Gaulton et al 2013) aims to overcome these issues using full-waveform analysis and two wavelengths (1064 nm and 1545 nm), allowing the characterisation of a porous canopy, the identification of leaf and wood and derivation of information on leaf biochemistry. Gaulton et al (2013) showed that SALCA is capable of measuring the Equivalent Water Thickness (EWT) of individual leaves in laboratory conditions. In this study, the method was applied to complete tree canopies. A controlled experiment simulating a small 'forest' of potted broadleaved (Tilia cordata) and coniferous trees (Pinus nigra) was established and groups subjected to different moisture stresses over a one month period. Trees were repeatedly scanned by SALCA and regular measurements were made of leaf EWT, stomatal conductance, chlorophyll content, spectral properties (using an ASD field spectroradiometer) and, for a limited number of trees, leaf area (by destructive harvesting). Trees were arranged so that some were clearly visible to the scanner and could be analysed individually (a best case scenario) whilst others were grouped to form a denser, more realistic canopy (a worse case scenario). A method was developed to simultaneously extract canopy structure (leaf area, tree height and clumping) and leaf biochemistry (EWT) from the laser scanner data. These results were compared to ground to assess their accuracy. References Danson, F. M., Hetherington D., Morsdorf F., Koetz B., Allgower B., 2007. Forest canopy gap fraction from terrestrial laser scanning. IEEE Geoscience and Remote Sensing Letters, 4, 157-160. Gaulton R., Danson F. M., Ramirez F. A., Gunawan O., 2013. The potential of dual-wavelength laser scanning for estimating vegetation moisture content. Remote Sensing of Environment, 132, 32-39.

Forest impacts on snow accumulation and ablation across an elevation gradient in a temperate montane environment

NASA Astrophysics Data System (ADS)

Roth, Travis R.; Nolin, Anne W.

2017-11-01

Forest cover modifies snow accumulation and ablation rates via canopy interception and changes in sub-canopy energy balance processes. However, the ways in which snowpacks are affected by forest canopy processes vary depending on climatic, topographic and forest characteristics. Here we present results from a 4-year study of snow-forest interactions in the Oregon Cascades. We continuously monitored snow and meteorological variables at paired forested and open sites at three elevations representing the Low, Mid, and High seasonal snow zones in the study region. On a monthly to bi-weekly basis, we surveyed snow depth and snow water equivalent across 900 m transects connecting the forested and open pairs of sites. Our results show that relative to nearby open areas, the dense, relatively warm forests at Low and Mid sites impede snow accumulation via canopy snow interception and increase sub-canopy snowpack energy inputs via longwave radiation. Compared with the Forest sites, snowpacks are deeper and last longer in the Open site at the Low and Mid sites (4-26 and 11-33 days, respectively). However, we see the opposite relationship at the relatively colder High sites, with the Forest site maintaining snow longer into the spring by 15-29 days relative to the nearby Open site. Canopy interception efficiency (CIE) values at the Low and Mid Forest sites averaged 79 and 76 % of the total event snowfall, whereas CIE was 31 % at the lower density High Forest site. At all elevations, longwave radiation in forested environments appears to be the primary energy component due to the maritime climate and forest presence, accounting for 93, 92, and 47 % of total energy inputs to the snowpack at the Low, Mid, and High Forest sites, respectively. Higher wind speeds in the High Open site significantly increase turbulent energy exchanges and snow sublimation. Lower wind speeds in the High Forest site create preferential snowfall deposition. These results show the importance of understanding the effects of forest cover on sub-canopy snowpack evolution and highlight the need for improved forest cover model representation to accurately predict water resources in maritime forests.

The impact of forest structure and light utilization on carbon cycling in tropical forests

NASA Astrophysics Data System (ADS)

Morton, D. C.; Longo, M.; Leitold, V.; Keller, M. M.

2015-12-01

Light competition is a fundamental organizing principle of forest ecosystems, and interactions between forest structure and light availability provide an important constraint on forest productivity. Tropical forests maintain a dense, multi-layered canopy, based in part on abundant diffuse light reaching the forest understory. Climate-driven changes in light availability, such as more direct illumination during drought conditions, therefore alter the potential productivity of forest ecosystems during such events. Here, we used multi-temporal airborne lidar data over a range of Amazon forest conditions to explore the influence of forest structure on gross primary productivity (GPP). Our analysis combined lidar-based observations of canopy illumination and turnover in the Ecosystem Demography model (ED, version 2.2). The ED model was updated to specifically account for regional differences in canopy and understory illumination using lidar-derived measures of canopy light environments. Model simulations considered the influence of forest structure on GPP over seasonal to decadal time scales, including feedbacks from differential productivity between illuminated and shaded canopy trees on mortality rates and forest composition. Finally, we constructed simple scenarios with varying diffuse and direct illumination to evaluate the potential for novel plant-climate interactions under scenarios of climate change. Collectively, the lidar observations and model simulations underscore the need to account for spatial heterogeneity in the vertical structure of tropical forests to constrain estimates of tropical forest productivity under current and future climate conditions.

Global Forest Canopy Height Maps Validation and Calibration for The Potential of Forest Biomass Estimation in The Southern United States

NASA Astrophysics Data System (ADS)

Ku, N. W.; Popescu, S. C.

2015-12-01

In the past few years, three global forest canopy height maps have been released. Lefsky (2010) first utilized the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat) and Moderate Resolution Imaging Spectroradiometer (MODIS) data to generate a global forest canopy height map in 2010. Simard et al. (2011) integrated GLAS data and other ancillary variables, such as MODIS, Shuttle Radar Topography Mission (STRM), and climatic data, to generate another global forest canopy height map in 2011. Los et al. (2012) also used GLAS data to create a vegetation height map in 2012.Several studies attempted to compare these global height maps to other sources of data., Bolton et al. (2013) concluded that Simard's forest canopy height map has strong agreement with airborne lidar derived heights. Los map is a coarse spatial resolution vegetation height map with a 0.5 decimal degrees horizontal resolution, around 50 km in the US, which is not feasible for the purpose of our research. Thus, Simard's global forest canopy height map is the primary map for this research study. The main objectives of this research were to validate and calibrate Simard's map with airborne lidar data and other ancillary variables in the southern United States. The airborne lidar data was collected between 2010 and 2012 from: (1) NASA LiDAR, Hyperspectral & Thermal Image (G-LiHT) program; (2) National Ecological Observatory Network's (NEON) prototype data sharing program; (3) NSF Open Topography Facility; and (4) the Department of Ecosystem Science and Management at Texas A&M University. The airborne lidar study areas also cover a wide variety of vegetation types across the southern US. The airborne lidar data is post-processed to generate lidar-derived metrics and assigned to four different classes of point cloud data. The four classes of point cloud data are the data with ground points, above 1 m, above 3 m, and above 5 m. The root mean square error (RMSE) and coefficient of determination (R2) are used for examining the discrepancies of the canopy heights between the airborne lidar-derived metrics and global forest canopy height map, and the regression and random forest approaches are used to calibrate the global forest canopy height map. In summary, the research shows a calibrated forest canopy height map of the southern US.

Under-canopy snow accumulation and ablation measured with airborne scanning LiDAR altimetry and in-situ instrumental measurements, southern Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Kirchner, P. B.; Bales, R. C.; Musselman, K. N.; Molotch, N. P.

2012-12-01

We investigated the influence of canopy on snow accumulation and melt in a mountain forest using paired snow on and snow off scanning LiDAR altimetry, synoptic measurement campaigns and in-situ time series data of snow depth, SWE, and radiation collected from the Kaweah River watershed, Sierra Nevada, California. Our analysis of forest cover classified by dominant species and 1 m2 grided mean under canopy snow accumulation calculated from airborne scanning LiDAR, demonstrate distinct relationships between forest class and under-canopy snow depth. The five forest types were selected from carefully prepared 1 m vegetation classifications and named for their dominant tree species, Giant Sequoia, Jeffrey Pine, White Fir, Red Fir, Sierra Lodgepole, Western White Pine, and Foxtail Pine. Sufficient LiDAR returns for calculating mean snow depth per m2 were available for 31 - 44% of the canopy covered area and demonstrate a reduction in snow depth of 12 - 24% from adjacent open areas. The coefficient of variation in snow depth under canopies ranged from 0.2 - 0.42 and generally decreased as elevation increased. Our analysis of snow density snows no statistical significance between snow under canopies and in the open at higher elevations with a weak significance for snow under canopies at lower elevations. Incident radiation measurements made at 15 minute intervals under forest canopies show an input of up to 150 w/m2 of thermal radiation from vegetation to the snow surface on forest plots. Snow accumulated on the mid to high elevation forested slopes of the Sierra Nevada represents the majority of winter snow storage. However snow estimates in forested environments demonstrate a high level of uncertainty due to the limited number of in-situ observations and the inability of most remote sensing platforms to retrieve reflectance under dense vegetation. Snow under forest canopies is strongly mediated by forest cover and decoupled from the processes that dictate accumulation and ablation of snow in open locations, where almost all precipitation and meteorlogic measurements concerning snow are made. Snow accumulation is intercepted by vegetation until it accumulates to a depth equal to or greater than the height of the vegetation, is reduced by the amount of sublimation or evaporation occurring while on the canopy and is redistributed beneath the canopy at a different density or as liquid water. Ablation processes are dictated by the energy environment surrounding vegetation where sensible heat is mediated by shading of short wave radiation.

Integration of airborne LiDAR data and voxel-based ray tracing to determine high-resolution solar radiation dynamics at the forest floor: implications for improving stand-scale distributed snowmelt models

NASA Astrophysics Data System (ADS)

Musselman, K. N.; Molotch, N. P.; Margulis, S. A.

2012-12-01

Forest architecture dictates sub-canopy solar irradiance and the resulting patterns can vary seasonally and over short spatial distances. These radiation dynamics are thought to have significant implications on snowmelt processes, regional hydrology, and remote sensing signatures. The variability calls into question many assumptions inherent in traditional canopy models (e.g. Beer's Law) when applied at high resolution (i.e. 1 m). We present a method of estimating solar canopy transmissivity using airborne LiDAR data. The canopy structure is represented in 3-D voxel space (i.e. a cubic discretization of a 3-D domain analogous to a pixel representation of a 2-D space). The solar direct beam canopy transmissivity (DBT) is estimated with a ray-tracing algorithm and the diffuse component is estimated from LiDAR-derived effective LAI. Results from one year at five-minute temporal and 1 m spatial resolutions are presented from Sequoia National Park. Compared to estimates from 28 hemispherical photos, the ray-tracing model estimated daily mean DBT with a 10% average error, while the errors from a Beer's-type DBT estimate exceeded 20%. Compared to the ray-tracing estimates, the Beer's-type transmissivity method was unable to resolve complex spatial patterns resulting from canopy gaps, individual tree canopies and boles, and steep variable terrain. The snowmelt model SNOWPACK was applied at locations of ultrasonic snow depth sensors. Two scenarios were tested; 1) a nominal case where canopy model parameters were obtained from hemispherical photographs, and 2) an explicit scenario where the model was modified to accept LiDAR-derived time-variant DBT. The bulk canopy treatment was generally unable to simulate the sub-canopy snowmelt dynamics observed at the depth sensor locations. The explicit treatment reduced error in the snow disappearance date by one week and both positive and negative melt-season SWE biases were reduced. The results highlight the utility of LiDAR canopy measurements and physically based snowmelt models to simulate spatially distributed stand- and slope-scale snowmelt dynamics at resolutions necessary to capture the inherent underlying variability.iDAR-derived solar direct beam canopy transmissivity computed as the daily average for March 1st and May 1st.

The influence of canopy shading of snow on effective albedo in forested environments

NASA Astrophysics Data System (ADS)

Webster, C.; Jonas, T.

2017-12-01

The overlap of highly reflective snow and absorbent forested areas creates strong heterogeneity in the effective surface albedo compared to forest-free areas. Current errors in calculations of effective forest snow albedo arise due to uncertainties in how models should treat masking of snow by vegetation but improvement of local and large scale models is currently limited by a lack of measurements that demonstrate both spatial and temporal variability over forests. We present above-canopy measurements of winter-time effective forest snow albedo using up- and down-looking radiometers mounted on an octocopter UAV for a total of fifteen flights on eight different days. Ground-view fractions across the flight path were between 0.12 and 0.81. Correlations between effective albedo and both ground-view fraction and canopy height were statistically significant during 14 out of 15 flights, but varied between flights due to solar angle and snow cover. Measured effective albedo across the flight path differed by up to 0.33 during snow-on canopy conditions. A comparison between maximum interception and no interception showed effective albedo varied by up 0.17, which was the same variation between effective albedo during high (46°) and low (23°) solar elevation angles. Temporal and spatial variations in effective albedo caused by canopy shading of the snow surface are therefore as important as temporal variations caused by interception of snow by the canopy. Calculation of effective albedo over forested areas therefore requires careful consideration of canopy height, canopy coverage, solar angle and interception load. The results of this study should be used to inform snow albedo and canopy structure parametrisations in local and larger scale land surface models.

Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations

Treesearch

Gregory P. Asner; Michael Palace; Michael Keller; Rodrigo Pereira Jr.; Jose N. M. Silva; Johan C. Zweede

2002-01-01

Canopy structural data can be used for biomass estimation and studies of carbon cycling, disturbance, energy balance, and hydrological processes in tropical forest ecosystems. Scarce information on canopy dimensions reflects the difficulties associated with measuring crown height, width, depth, and area in tall, humid tropical forests. New field and spaceborne...

A cross-comparison of field, spectral, and lidar estimates of forest canopy cover

Treesearch

Alistair M. S. Smith; Michael J. Falkowski; Andrew T. Hudak; Jeffrey S. Evans; Andrew P. Robinson; Caiti M. Steele

2010-01-01

A common challenge when comparing forest canopy cover and similar metrics across different ecosystems is that there are many field- and landscape-level measurement methods. This research conducts a cross-comparison and evaluation of forest canopy cover metrics produced using unmixing of reflective spectral satellite data, light detection and ranging (lidar) data, and...

Development and applications of the LANDFIRE forest structure layers

Treesearch

Chris Toney; Birgit Peterson; Don Long; Russ Parsons; Greg Cohn

2012-01-01

The LANDFIRE program is developing 2010 maps of vegetation and wildland fuel attributes for the United States at 30-meter resolution. Currently available vegetation layers include ca. 2001 and 2008 forest canopy cover and canopy height derived from Landsat and Forest Inventory and Analysis (FIA) plot measurements. The LANDFIRE canopy cover layer for the conterminous...

Interactions of Northwest forest canopies and arboreal mammals.

Treesearch

A.B. Carey

1996-01-01

The interactions among Northwest forest canopies and the mammals that inhabit them have been poorly studied. My purpose was to identify interactions among arboreal mammals and canopies that have implications for managers seeking to conserve biodiversity in the Pacific Northwest. I constructed a comprehensive, but parsimonious list of canopy attributes that could be...

Arbuscular mycorrhizal fungi in the tree seedlings of two Australian rain forests: occurrence, colonization, and relationships with plant performance.

PubMed

Gehring, Catherine A; Connell, Joseph H

2006-03-01

The roots of rain forest plants are frequently colonized by arbuscular mycorrhizal fungi (AMF) that can promote plant growth in the nutrient poor soils characteristic of these forests. However, recent studies suggest that both the occurrence of AMF on rain forest plants and the dependence of rain forest plants on AMF can be highly variable. We examined the occurrence and levels of AMF colonization of some common seedling species in a tropical and a subtropical rain forest site in Queensland, Australia. We also used a long-term database to compare the growth and mortality rates of seedling species that rarely formed AMF with those that regularly formed AMF. In both forests, more than one-third of the seedling species rarely formed AMF associations, while 40% of species consistently formed AMF in the tropical site compared to 27% in the subtropical site. Consistent patterns of AMF occurrence were observed among plant families at the two sites. Variation among seedling species in AMF occurrence or colonization was not associated with differences in seed mass among species, variation in seedling size and putative age within a species, or lack of AMF inoculum in the soil. Comparisons of four seedling species growing both in the shaded understory and in small canopy gaps revealed an increase in AMF colonization in two of the four species in gaps, suggesting that light limitation partially explains the low occurrence of AMF. Seedling survival was significantly positively associated with seed biomass but not with AMF colonization. Furthermore, seedling species that regularly formed AMF and those that did not had similar rates of growth and survival, suggesting that mycorrhizal and nonmycorrhizal strategies were equivalent in these forests. Furthermore, the high numbers of seedlings that lacked AMF and the overall low rate of seedling growth (the average seedling required 6 years to double its height) suggest that most seedlings did not receive significant indirect benefits from AMF through connection to canopy trees via a common mycorrhizal network.

High-Resolution Forest Canopy Height Estimation in an African Blue Carbon Ecosystem

NASA Technical Reports Server (NTRS)

Lagomasino, David; Fatoyinbo, Temilola; Lee, Seung-Kuk; Simard, Marc

2015-01-01

Mangrove forests are one of the most productive and carbon dense ecosystems that are only found at tidally inundated coastal areas. Forest canopy height is an important measure for modeling carbon and biomass dynamics, as well as land cover change. By taking advantage of the flat terrain and dense canopy cover, the present study derived digital surface models (DSMs) using stereophotogrammetric techniques on high-resolution spaceborne imagery (HRSI) for southern Mozambique. A mean-weighted ground surface elevation factor was subtracted from the HRSI DSM to accurately estimate the canopy height in mangrove forests in southern Mozambique. The mean and H100 tree height measured in both the field and with the digital canopy model provided the most accurate results with a vertical error of 1.18-1.84 m, respectively. Distinct patterns were identified in the HRSI canopy height map that could not be discerned from coarse shuttle radar topography mission canopy maps even though the mode and distribution of canopy heights were similar over the same area. Through further investigation, HRSI DSMs have the potential of providing a new type of three-dimensional dataset that could serve as calibration/validation data for other DSMs generated from spaceborne datasets with much larger global coverage. HSRI DSMs could be used in lieu of Lidar acquisitions for canopy height and forest biomass estimation, and be combined with passive optical data to improve land cover classifications.

Influence of vegetation structure on lidar-derived canopy height and fractional cover in forested riparian buffers during leaf-off and leaf-on conditions.

PubMed

Wasser, Leah; Day, Rick; Chasmer, Laura; Taylor, Alan

2013-01-01

Estimates of canopy height (H) and fractional canopy cover (FC) derived from lidar data collected during leaf-on and leaf-off conditions are compared with field measurements from 80 forested riparian buffer plots. The purpose is to determine if existing lidar data flown in leaf-off conditions for applications such as terrain mapping can effectively estimate forested riparian buffer H and FC within a range of riparian vegetation types. Results illustrate that: 1) leaf-off and leaf-on lidar percentile estimates are similar to measured heights in all plots except those dominated by deciduous compound-leaved trees where lidar underestimates H during leaf off periods; 2) canopy height models (CHMs) underestimate H by a larger margin compared to percentile methods and are influenced by vegetation type (conifer needle, deciduous simple leaf or deciduous compound leaf) and canopy height variability, 3) lidar estimates of FC are within 10% of plot measurements during leaf-on periods, but are underestimated during leaf-off periods except in mixed and conifer plots; and 4) depth of laser pulse penetration lower in the canopy is more variable compared to top of the canopy penetration which may influence within canopy vegetation structure estimates. This study demonstrates that leaf-off lidar data can be used to estimate forested riparian buffer canopy height within diverse vegetation conditions and fractional canopy cover within mixed and conifer forests when leaf-on lidar data are not available.

Influence of Vegetation Structure on Lidar-derived Canopy Height and Fractional Cover in Forested Riparian Buffers During Leaf-Off and Leaf-On Conditions

PubMed Central

Wasser, Leah; Day, Rick; Chasmer, Laura; Taylor, Alan

2013-01-01

Estimates of canopy height (H) and fractional canopy cover (FC) derived from lidar data collected during leaf-on and leaf-off conditions are compared with field measurements from 80 forested riparian buffer plots. The purpose is to determine if existing lidar data flown in leaf-off conditions for applications such as terrain mapping can effectively estimate forested riparian buffer H and FC within a range of riparian vegetation types. Results illustrate that: 1) leaf-off and leaf-on lidar percentile estimates are similar to measured heights in all plots except those dominated by deciduous compound-leaved trees where lidar underestimates H during leaf off periods; 2) canopy height models (CHMs) underestimate H by a larger margin compared to percentile methods and are influenced by vegetation type (conifer needle, deciduous simple leaf or deciduous compound leaf) and canopy height variability, 3) lidar estimates of FC are within 10% of plot measurements during leaf-on periods, but are underestimated during leaf-off periods except in mixed and conifer plots; and 4) depth of laser pulse penetration lower in the canopy is more variable compared to top of the canopy penetration which may influence within canopy vegetation structure estimates. This study demonstrates that leaf-off lidar data can be used to estimate forested riparian buffer canopy height within diverse vegetation conditions and fractional canopy cover within mixed and conifer forests when leaf-on lidar data are not available. PMID:23382966

[Simulation of CO2 exchange between forest canopy and atmosphere].

PubMed

Diao, Yiwei; Wang, Anzhi; Jin, Changjie; Guan, Dexin; Pei, Tiefan

2006-12-01

Estimating the scalar source/sink distribution of CO2 and its vertical fluxes within and above forest canopy continues to be a critical research problem in biosphere-atmosphere exchange processes and plant ecology. With broad-leaved Korean pine forest in Changbai Mountains as test object, and based on Raupach's localized near field theory, the source/sink and vertical flux distribution of CO2 within and above forest canopy were modeled through an inverse Lagrangian dispersion analysis. This model correctly predicted a strong positive CO2 source strength in the deeper layers of the canopy due to soil-plant respiration, and a strong CO2 sink in the upper layers of the canopy due to the assimilation by sunlit foliage. The foliage in the top layer of canopy changed from a CO2 source in the morning to a CO2 sink in the afternoon, while the soil constituted a strong CO2 source all the day. The simulation results accorded well with the eddy covariance CO2 flux measurements within and above the canopy, and the average precision was 89%. The CO2 exchange predicted by the analysis was averagely 15% higher than that of the eddy correlation, but exhibited identical temporal trend. Atmospheric stability remarkably affected the CO2 exchange between forest canopy and atmosphere.

The effect of canopy closure on chimpanzee nest abundance in Lagoas de Cufada National Park, Guinea-Bissau.

PubMed

Sousa, Joana; Casanova, Catarina; Barata, André V; Sousa, Cláudia

2014-04-01

The present study aimed to gather baseline information about chimpanzee nesting and density in Lagoas de Cufada Natural Park (LCNP), in Guinea-Bissau. Old and narrow trails were followed to estimate chimpanzee density through marked-nest counts and to test the effect of canopy closure (woodland savannah, forest with a sparse canopy, and forest with a dense canopy) on nest distribution. Chimpanzee abundance was estimated at 0.79 nest builders/km(2), the lowest among the areas of Guinea-Bissau with currently studied chimpanzee populations. Our data suggest that sub-humid forest with a dense canopy accounts for significantly higher chimpanzee nest abundance (1.50 nests/km of trail) than sub-humid forest with a sparse canopy (0.49 nests/km of trail) or woodland savannah (0.30 nests/km of trail). Dense-canopy forests play an important role in chimpanzee nesting in the patchy and highly humanized landscape of LCNP. The tree species most frequently used for nesting are Dialium guineense (46%) and Elaeis guineensis (28%). E. guineensis contain nests built higher in the canopy, while D. guineense contain nests built at lower heights. Nests observed during baseline sampling and replications suggest seasonal variations in the tree species used for nest building.

Determining coniferous forest cover and forest fragmentation with NOAA-9 advanced very high resolution radiometer data

NASA Technical Reports Server (NTRS)

Ripple, William J.

1995-01-01

NOAA-9 satellite data from the Advanced Very High Resolution Radiometer (AVHRR) were used in conjunction with Landsat Multispectral Scanner (MSS) data to determine the proportion of closed canopy conifer forest cover in the Cascade Range of Oregon. A closed canopy conifer map, as determined from the MSS, was registered with AVHRR pixels. Regression was used to relate closed canopy conifer forest cover to AVHRR spectral data. A two-variable (band) regression model accounted for more variance in conifer cover than the Normalized Difference Vegetation Index (NDVI). The spectral signatures of various conifer successional stages were also examined. A map of Oregon was produced showing the proportion of closed canopy conifer cover for each AVHRR pixel. The AVHRR was responsive to both the percentage of closed canopy conifer cover and the successional stage in these temperate coniferous forests in this experiment.

Investigating the relationship between tree heights derived from SIBBORK forest model and remote sensing measurements

NASA Astrophysics Data System (ADS)

Osmanoglu, B.; Feliciano, E. A.; Armstrong, A. H.; Sun, G.; Montesano, P.; Ranson, K.

2017-12-01

Tree heights are one of the most commonly used remote sensing parameters to measure biomass of a forest. In this project, we investigate the relationship between remotely sensed tree heights (e.g. G-LiHT lidar and commercially available high resolution satellite imagery, HRSI) and the SIBBORK modeled tree heights. G-LiHT is a portable, airborne imaging system that simultaneously maps the composition, structure, and function of terrestrial ecosystems using lidar, imaging spectroscopy and thermal mapping. Ground elevation and canopy height models were generated using the lidar data acquired in 2012. A digital surface model was also generated using the HRSI technique from the commercially available WorldView data in 2016. The HRSI derived height and biomass products are available at the plot (10x10m) level. For this study, we parameterized the SIBBORK individual-based gap model for Howland forest, Maine. The parameterization was calibrated using field data for the study site and results show that the simulated forest reproduces the structural complexity of Howland old growth forest, based on comparisons of key variables including, aboveground biomass, forest height and basal area. Furthermore carbon cycle and ecosystem observational capabilities will be enhanced over the next 6 years via the launch of two LiDAR (NASA's GEDI and ICESAT 2) and two SAR (NASA's ISRO NiSAR and ESA's Biomass) systems. Our aim is to present the comparison of canopy height models obtained with SIBBORK forest model and remote sensing techniques, highlighting the synergy between individual-based forest modeling and high-resolution remote sensing.

Mesohabitat use of threatened hemlock forests by breeding birds of the Delaware River basin in northeastern United States

USGS Publications Warehouse

Ross, R.M.; Redell, L.A.; Bennett, R.M.; Young, J.A.

2004-01-01

Avian biodiversity may be at risk in eastern parks and forests due to continued expansion of the hemlock woolly adelgid (Adelges tsugae), an exotic homopteran insect native to East Asia. To assess avian biodiversity, mesohabitat relations, and the risk of species loss with declining hemlock forests in Appalachian park lands, 80 randomly distributed fixed-radius plots were established in which territories of breeding birds were estimated on four forest-terrain types (hemlock and hardwood benches and ravines) in the Delaware Water Gap National Recreation Area. Both species richness and number of territories were higher in hardwood than hemlock forest types and in bench than ravine terrain types. Four insectivorous species, Acadian flycatcher (Empidonax virescens), blue-headed vireo (Vireo solitarius), black-throated green warbler (Dendroica virens), and Blackburnian warbler (Dendroica fusca), showed high affinity for hemlock forest type and exhibited significantly greater numbers of territories in hemlock than hardwood sites. These species are hemlock-associated species at risk from continued hemlock decline in the Delaware River valley and similar forests of the mid-Atlantic east slope. Two of these species, the blue-headed vireo and Blackburnian warbler, appeared to specialize on ravine mesohabitats of hemlock stands, the vireo a low-to-mid canopy species, the warbler a mid-to-upper canopy forager. Unchecked expansion of the exotic adelgid and subsequent hemlock decline could negatively impact 3,600 pairs from the park and several million pairs from northeastern United States hemlock forests due to elimination of preferred habitat.

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.

The stochastic Beer-Lambert-Bouguer law for discontinuous vegetation canopies

NASA Astrophysics Data System (ADS)

Shabanov, N.; Gastellu-Etchegorry, J.-P.

2018-07-01

The 3D distribution of canopy foliage affects the radiation regime and retrievals of canopy biophysical parameters. The gap fraction is one primary indicator of a canopy structure. Historically the Beer-Lambert-Bouguer law and the linear mixture model have served as a basis for multiple technologies for retrievals of the gap (or vegetation) fraction and Leaf Area Index (LAI). The Beer-Lambert-Bouguer law is a form of the Radiative Transfer (RT) equation for homogeneous canopies, which was later adjusted for a correlation between fitoelements using concept of the clumping index. The Stochastic Radiative Transfer (SRT) approach has been developed specifically for heterogeneous canopies, however the approach lacks a proper model of the vegetation fraction. This study is focused on the implementation of the stochastic version of the Beer-Lambert-Bouguer law for heterogeneous canopies, featuring the following principles: 1) two mechanisms perform photon transport- transmission through the turbid medium of foliage crowns and direct streaming through canopy gaps, 2) the radiation field is influenced by a canopy structure (quantified by the statistical moments of a canopy structure) and a foliage density (quantified by the gap fraction as a function of LAI), 3) the notions of canopy transmittance and gap fraction are distinct. The derived stochastic Beer-Lambert-Bouguer law is consistent with the Geometrical Optical and Radiative Transfer (GORT) derivations. Analytical and numerical analysis of the stochastic Beer-Lambert-Bouguer law presented in this study provides the basis to reformulate widely used technologies for retrievals of the gap fraction and LAI from ground and satellite radiation measurements.

Do trees fall downhill? Relationship between treefall direction and slope-aspect and wind in eight old-growth oak stands in the central hardwood forest

Treesearch

James S. Rentch

2011-01-01

This study examined the relationship between direction of treefall and slope-aspect, and prevailing wind in eight old-growth stands where single-tree canopy gaps characterize the dominant disturbance regime. All live and downed trees were inventoried in 0.45-ha sample plots. To determine crown asymmetry, crown sizes of live trees were measured along two perpendicular...

Testing a ground-based canopy model using the wind river canopy crane

Treesearch

Robert Van Pelt; Malcolm P. North

1999-01-01

A ground-based canopy model that estimates the volume of occupied space in forest canopies was tested using the Wind River Canopy Crane. A total of 126 trees in a 0.25 ha area were measured from the ground and directly from a gondola suspended from the crane. The trees were located in a low elevation, old-growth forest in the southern Washington Cascades. The ground-...

Forest canopy growth dynamic modeling based on remote sensing prodcuts and meteorological data in Daxing'anling of Northeast China

NASA Astrophysics Data System (ADS)

Wu, Qiaoli; Song, Jinling; Wang, Jindi; Xiao, Zhiqiang

2014-11-01

Leaf Area Index (LAI) is an important biophysical variable for vegetation. Compared with vegetation indexes like NDVI and EVI, LAI is more capable of monitoring forest canopy growth quantitatively. GLASS LAI is a spatially complete and temporally continuous product derived from AVHRR and MODIS reflectance data. In this paper, we present the approach to build dynamic LAI growth models for young and mature Larix gmelinii forest in north Daxing'anling in Inner Mongolia of China using the Dynamic Harmonic Regression (DHR) model and Double Logistic (D-L) model respectively, based on the time series extracted from multi-temporal GLASS LAI data. Meanwhile we used the dynamic threshold method to attract the key phenological phases of Larix gmelinii forest from the simulated time series. Then, through the relationship analysis between phenological phases and the meteorological factors, we found that the annual peak LAI and the annual maximum temperature have a good correlation coefficient. The results indicate this forest canopy growth dynamic model to be very effective in predicting forest canopy LAI growth and extracting forest canopy LAI growth dynamic.

Origin of the Hawaiian rainforest ecosystem and its evolution in long-term primary succession

NASA Astrophysics Data System (ADS)

Mueller-Dombois, D.; Boehmer, H. J.

2013-02-01

Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering plants that over the millenia evolved into ca. 1000 endemic species. Outstanding among the forest builders were the tree ferns (Cibotium spp.) and the 'Ōhi'a lehua trees (Metrosideros spp.), which still dominate the Hawaiian rainforest ecosystem today. The structure of this forest is simple. The canopy in closed mature rainforests is dominated by cohorts of Metrosideros polymorpha and the undergrowth by tree fern species of Cibotium. When a new lava flow cuts through this forest, kipuka are formed, i.e. islands of remnant vegetation. On the new volcanic substrate, the assemblage of plant life-forms is similar as during the evolution of this system. In open juvenile forests, a mat-forming fern, the uluhe fern (Dicranopteris lineraris) becomes established. It inhibits further regeneration of the dominant 'Ōhi'a tree, thereby reinforcing the cohort structure of the canopy guild. In the later part of its life cycle, the canopy guild breaks down often in synchrony. The trigger is hypothesized to be a climatic perturbation. After that disturbance the forest becomes reestablished in about 30-40 yr. As the volcanic surfaces age, they go from a mesotrophic to a eutrophic phase, reaching a biophilic nutrient climax by about 1-25 K yr. Thereafter, a regressive oligotrophic phase follows; the soils become exhausted of nutrients. The shield volcanoes break down. Marginally, forest habitats change into bogs and stream ecosystems. The broader 'Ōhi'a rainforest redeveloping in the more dissected landscapes of the older islands looses stature, often forming large gaps that are invaded by the aluminum tolerant uluhe fern. The 'Ōhi'a trees still thrive on soils rejuvenated from landslides and from Asian dust on the oldest (5 million year old) island Kaua'i but their stature and living biomass is greatly diminished.

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

NASA Astrophysics Data System (ADS)

Naudts, K.; Ryder, J.; McGrath, M. J.; Otto, J.; Chen, Y.; Valade, A.; Bellasen, V.; Berhongaray, G.; Bönisch, G.; Campioli, M.; Ghattas, J.; De Groote, T.; Haverd, V.; Kattge, J.; MacBean, N.; Maignan, F.; Merilä, P.; Penuelas, J.; Peylin, P.; Pinty, B.; Pretzsch, H.; Schulze, E. D.; Solyga, D.; Vuichard, N.; Yan, Y.; Luyssaert, S.

2015-07-01

Since 70 % of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land-surface models used in Earth system models, and therefore none of today's predictions of future climate, accounts for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrising a version of the ORCHIDEE land-surface model to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes were introduced towards a better process representation for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrisation was revisited after introducing 12 new parameter sets that represent specific tree species or genera rather than a group of often distantly related or even unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, gross primary production (GPP), albedo and evapotranspiration over Europe. For all tested variables, ORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92 % chance to reproduce the spatial and temporal variability of the validation data.

Forest-atmosphere BVOC exchange in diverse and structurally complex canopies: 1-D modeling of a mid-successional forest in northern Michigan

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

Bryan, Alexander M.; Cheng, Susan J.; Ashworth, Kirsti

Foliar emissions of biogenic volatile organic compounds (BVOC)dimportant precursors of tropospheric ozone and secondary organic aerosolsdvary widely by vegetation type. Modeling studies to date typi-cally represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height vari-ation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homo-geneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting fo-liagemore » (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.« less

Temperate forest impacts on maritime snowpacks across an elevation gradient: An assessment of the snow surface energy balance and airborne lidar derived forest structure

NASA Astrophysics Data System (ADS)

Roth, T. R.; Nolin, A. W.

2016-12-01

Temperate forests modify snow evolution patterns both spatially and temporally relative to open areas. Dense, warm forests both impede snow accumulation through increased canopy snow interception and increase sub-canopy longwave energy inputs onto the snow surface. These process modifications vary in magnitude and duration depending on climatic, topographic and forest characteristics. Here we present results from a four year study of paired forested and open sites at three elevations, Low - 1150 m, Mid - 1325 m and High - 1465 m. Snowpacks are deeper and last up to 3-4 weeks longer at the Low and Mid elevation Open sites relative to the adjacent Forest sites. Conversely, at the High Forest site, snow is retained 2-4 weeks longer than the Open site. This change in snowpack depth and persistence is attributed to deposition patterns at higher elevations and forest structure differences that alter the canopy interception efficiency and the sub-canopy energy balance. Canopy interception efficiency (CIE) in the Low and Mid Forest sites, over the duration of the study were 79% and 76% of the total event snowfall, whereas CIE was 31% at the High Forest site. Longwave radiation in forested environments is the primary energy component across each elevation band due to the warm winter environment and forest presence, accounting for 82%, 88%, and 59% of the energy balance at the Low, Mid, and High Forest sites, respectively. High wind speeds in the High elevation Open site significantly increases the turbulent energy and creates preferential snowfall deposition in the nearby Forest site. These results show the importance of understanding the effects of forest cover on sub-canopy snowpack evolution and highlight the need for improved forest cover model representation to accurately predict water resources in maritime forests.

Field- and Remote Sensing-based Structural Attributes Measured at Multiple Scales Influence the Relationship Between Nitrogen and Reflectance of Forest Canopies

NASA Astrophysics Data System (ADS)

Sullivan, F.; Ollinger, S. V.; Palace, M. W.; Ouimette, A.; Sanders-DeMott, R.; Lepine, L. C.

2017-12-01

The correlation between near-infrared reflectance and forest canopy nitrogen concentration has been demonstrated at varying scales using a range of optical sensors on airborne and satellite platforms. Although the mechanism underpinning the relationship is unclear, at its basis are biologically-driven functional relationships of multiple plant traits that affect canopy chemistry and structure. The link between near-infrared reflectance and canopy nitrogen has been hypothesized to be partially driven by covariation of canopy nitrogen with canopy structure. In this study, we used a combination of airborne LiDAR data and field measured leaf and canopy chemical and structural traits to explore interrelationships between canopy nitrogen, near-infrared reflectance, and canopy structure on plots at Bartlett Experimental Forest in the White Mountain National Forest, New Hampshire. Over each plot, we developed a 1-meter resolution canopy height profile and a 1-meter resolution canopy height model. From canopy height profiles and canopy height models, we calculated a set of metrics describing the plot-level variability, breadth, depth, and arrangement of LiDAR returns. This combination of metrics was used to describe both vertical and horizontal variation in structure. In addition, we developed and measured several field-based metrics of leaf and canopy structure at the plot scale by directly measuring the canopy or by weighting leaf-level metrics by species leaf area contribution. We assessed relationships between leaf and structural metrics, near-infrared reflectance and canopy nitrogen concentration using multiple linear regression and mixed effects modeling. Consistent with our hypothesis, we found moderately strong links between both near-infrared reflectance and canopy nitrogen concentration with LiDAR-derived structural metrics, and we additionally found that leaf-level metrics scaled to the plot level share an important role in canopy reflectance. We suggest that canopy structure has a governing role in canopy reflectance, reducing maximum potential reflectance as structural complexity increases, and therefore also influences the relationship between canopy nitrogen and NIR reflectance.

[Microbial community and its activities in canopy- and understory humus of two montane forest types in Ailao Mountains, Northwest China].

PubMed

Liu, Yong-jie; Liu, Wen-yao; Chen, Lin; Zhang, Han-bo; Wang, Gao-sheng

2010-09-01

Mid-montane moist evergreen broadleaved forest (MMF) and top-montane dwarf mossy forest (DMF) are the two major natural forest types in subtropical mountainous area of Ailao Mountains, Northwest China. In this paper, a comparative study was made on the microbial composition, quantity, biochemical activity, metabolic activity, and their seasonal dynamics in the canopy- and understory humus of the two forest types. The composition, quantity, and metabolic activity of the microbes in the canopy humus of dominant tree species in MMF and DMF were also analyzed. In the canopy humus of the two forest types, the amounts of fungi and actinomycetes, microbial biomass C and N, and intensities of nitrogen fixation and cellulose decomposition were significantly higher than those in understory humus. Meanwhile, the amount of cellulose-decomposing microbes (ACDM), cellulose decomposition intensity, microbial biomass C and N, and metabolic activity in the canopy humus of MMF were significantly higher than those of DMF. The amounts of bacteria, fungi, and aerobic nitrogen-fixing bacteria (ANFB) and the metabolic activity in the canopy humus of MMF and DMF were significantly higher in wet season than in dry season, while a contradictory trend was observed on the amount of actinomycetes. No significant difference was observed on the amount of ACDM between wet season and dry season. For the two forest types, the amounts of microbes and their biochemical activities in canopy humus had a larger seasonal variation range than those in understory humus. There was a significant difference in the amounts of the microbes in canopy humus among the dominant tree species in MMF and DMF, especially in wet season. The microbes in canopy humus played important roles in maintaining the biodiversity of epiphytes in the canopy, and in supplying the needed nutrients for the vigorous growth of the epiphytes.

Diversity of Bats in Contrasting Habitats of Hulu Terengganu Dipterocarp Forest and Setiu Wetland BRIS Forest with a Note on Preliminary Study of Vertical Stratification of Pteropodid Bats

PubMed Central

Pounsin, Grace; Wahab, Nur Syahirah; Roslan, Azuan; Zahidin, Muhamad Aidil; Pesiu, Elizabeth; Tamrin, Nur Aida Md; Abdullah, M T

2018-01-01

A study of the bat diversity was conducted in Hulu Terengganu dipterocarp forest and Setiu Wetland Beach Ridges Interspersed with Swales (BRIS) forest in Terengganu, to study the species diversity, composition and stratification of fruit bats from the understorey to the forest canopy. Mist nets were set up at the understorey, sub-canopy and canopy layer while harp traps were set up at the understorey layer. We recorded 170 individuals from six families’ compromised 21 species from Hulu Terengganu dipterocarp forests and four species from Setiu Wetland BRIS forests throughout the sampling period. Megaerops ecaudatus and Cynopterus brachyotis were the most dominant species in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forests. Our study also recorded two species with new distributional records for the east coast of Peninsular Malaysia, namely, Rhinolophus chiewkweeae and Chaerephon johorensis in Hulu Terengganu dipterocarp forests. Potential factors that might influence the results were in terms of the canopy covers, the structural complexity of canopy, food availability and spatial characteristics. This study was able to increase the knowledge on the species diversity and composition of bats in Hulu Terengganu dipterocarp forest and Setiu Wetland BRIS forest, thus, further aid in the effort of bat conservation in both areas. PMID:29644015

Quantifying the effects of mountain pine beetle infestation on water and biogeochemical cycles at multiple spatial and temporal scales

NASA Astrophysics Data System (ADS)

Brooks, P. D.; Harpold, A. A.; Somor, A. J.; Troch, P. A.; Gochis, D. J.; Ewers, B. E.; Pendall, E.; Biederman, J. A.; Reed, D.; Barnard, H. R.; Whitehouse, F.; Aston, T.; Borkhuu, B.

2010-12-01

Unprecedented levels of bark beetle infestation over the last decade have radically altered forest structure across millions of hectares of Western U.S. montane environments. The widespread extent of this disturbance presents a major challenge for governments and resource managers who lack a predictive understanding of how water and biogeochemical cycles will respond to this disturbance over various temporal and spatial scales. There is a widespread perception, largely based on hydrological responses to fire or logging, that a reduction in both transpiration and interception following tree death will increase soil water availability and catchment water yield. However, few studies have directly addressed the effects of insect-induced forest decline on water and biogeochemical cycling. We address this knowledge gap using observations and modeling at scales from 100 to 109 m2 across study sites in CO and WY that vary in the intensity and timing of beetle infestation and tree death. Our focus on multiple sites with different levels of impact allows us to address two broad, organizing questions: How do changes in vegetation structure associated with MPB alter the partitioning of energy and water? And How do these changes in energy and water availability affect local to regional scale water and biogeochemical cycles? This presentation will focus primarily on energy balance and water partitioning, providing context for ongoing biogeochemical work. During the growing season, stand-scale transpiration declines rapidly and soil moisture increases following infestation, consistent with streamflow data from regional catchments that shows an increase in baseflow following widespread attack. During the winter and spring, stand scale snow surveys and continuous snow depth sensors suggested that the variability in snow cover decreased as the severity of beetle impact increases, but there were no significant stand-scale differences in snow depth among levels of impact. This is due both to an increase in snow under the canopies of dead trees and a decrease in snow cover in canopy gaps. For example, mean snow depth under the canopy was 86cm (CV 0.02) in unimpacted sites and 95cm (CV 0.05) in heavily impacted sites. In canopy gaps however, mean snow depth was 117cm (CV 0.11) in unimpacted sites but only 93cm (CV 0.07) in heavily impacted sites. At the watershed scale, bark beetle infestation was more likely to decrease the amount of both snowmelt and annual runoff, suggesting that the opening of the canopy increases sublimation and evaporation of the snow cover. These data suggest that the disturbance due to bark beetle infestation is both quantitatively and qualitatively different than either fire or logging. Using these observations, we develop a conceptual model for evaluating how biotic and abiotic processes couple water and biogeochemical cycles in forest ecosystems.

Measurements of canopy chemistry with 1992 AVIRIS data at Blackhawk Island and Harvard Forest

NASA Technical Reports Server (NTRS)

Martin, Mary E.; Aber, John D.

1993-01-01

The research described in this paper was designed to determine if high spectral resolution imaging spectrometer data can be used to measure the chemical composition of forest foliage, specifically nitrogen and lignin concentration. Information about the chemical composition of forest canopies can be used to determine nutrient cycling rates and carbon balances in forest ecosystems. This paper will describe the results relating data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) to field measured canopy chemistry at Blackhawk Island, WI and Harvard Forest, MA.

Fine-scale habitat use by orang-utans in a disturbed peat swamp forest, central Kalimantan, and implications for conservation management.

PubMed

Morrogh-Bernard, Helen C; Husson, Simon J; Harsanto, Fransiskus A; Chivers, David J

2014-01-01

This study was conducted to see how orang-utans (Pongo pygmaeus wurmbii) were coping with fine-scale habitat disturbance in a selectively logged peat swamp forest in Central Kalimantan, Borneo. Seven habitat classes were defined, and orang-utans were found to use all of these, but were selective in their preference for certain classes over others. Overall, the tall forest classes (≥20 m) were preferred. They were preferred for feeding, irrespective of canopy connectivity, whereas classes with a connected canopy (canopy cover ≥75%), irrespective of canopy height, were preferred for resting and nesting, suggesting that tall trees are preferred for feeding and connected canopy for security and protection. The smaller forest classes (≤10 m high) were least preferred and were used mainly for travelling from patch to patch. Thus, selective logging is demonstrated here to be compatible with orang-utan survival as long as large food trees and patches of primary forest remain. Logged forest, therefore, should not automatically be designated as 'degraded'. These findings have important implications for forest management, forest classification and the designation of protected areas for orang-utan conservation.

Morton et al. Reply

NASA Technical Reports Server (NTRS)

Morton, Douglas C.; Nagol, Jyoteshwar; Carabajal, Claudia C.; Rosette, Jacqueline; Palace, Michael; Cook, Bruce D.; Vermote, Eric F.; Harding, David J.; North, Peter R. J.

2016-01-01

Multiple mechanisms could lead to up-regulation of dry-season photosynthesis in Amazon forests, including canopy phenology and illumination geometry. We specifically tested two mechanisms for phenology-driven changes in Amazon forests during dry-season months, and the combined evidence from passive optical and lidar satellite data was incompatible with large net changes in canopy leaf area or leaf reflectance suggested by previous studies. We therefore hypothesized that seasonal changes in the fraction of sunlit and shaded canopies, one aspect of bidirectional reflectance effects in Moderate Resolution Imaging Spectroradiometer (MODIS) data, could alter light availability for dry-season photosynthesis and the photosynthetic capacity of Amazon forests without large net changes in canopy composition. Subsequent work supports the hypothesis that seasonal changes in illumination geometry and diffuse light regulate light saturation in Amazon forests. These studies clarify the physical mechanisms that govern light availability in Amazon forests from seasonal variability in direct and diffuse illumination. Previously, in the debate over light limitation of Amazon forest productivity, seasonal changes in the distribution of light within complex Amazon forest canopies were confounded with dry-season increases in total incoming photosynthetically active radiation. In the accompanying Comment, Saleska et al. do not fully account for this confounding effect of forest structure on photosynthetic capacity.

[Effects of atmospheric thermally stratified condition on sensible heat within forest canopy].

PubMed

Diao, Yi-Wei; Wang, An-Zhi; Guan, De-Xin; Jin, Chang-Jie; Pei, Tie-Fan

2010-01-01

By using Eulerian second-order closure model, this paper studied the source-sink distribution and flux characteristics of sensible heat within forest canopy under atmospheric thermally stratified condition. In the daytime, a notable feature for the atmospheric stratification of forest canopy was the unstable stratification above the canopy and the stable stratification under the canopy. The changes of temperature profile indicated there was a 'hot spot' at about 2/3 of canopy height. The counter-gradient fluxes within the canopy were discovered by modeling the heat flux under weak stable atmospheric condition. Simulations of the diurnal variation of sensible heat flux were consistent with the measurements (R2 = 0.9035, P < 0.01). Adding buoyancy in the sensible heat balance equation could increase the simulation accuracy of inversion model, and improve the simulation capability for heat flux balance.

El Niño drought increased canopy turnover in Amazon forests.

PubMed

Leitold, Veronika; Morton, Douglas C; Longo, Marcos; Dos-Santos, Maiza Nara; Keller, Michael; Scaranello, Marcos

2018-03-25

Amazon droughts, including the 2015-2016 El Niño, may reduce forest net primary productivity and increase canopy tree mortality, thereby altering both the short- and the long-term net forest carbon balance. Given the broad extent of drought impacts, inventory plots or eddy flux towers may not capture regional variability in forest response to drought. We used multi-temporal airborne Lidar data and field measurements of coarse woody debris to estimate patterns of canopy turnover and associated carbon losses in intact and fragmented forests in the central Brazilian Amazon between 2013-2014 and 2014-2016. Average annualized canopy turnover rates increased by 65% during the drought period in both intact and fragmented forests. The average size and height of turnover events was similar for both time intervals, in contrast to expectations that the 2015-2016 El Niño drought would disproportionally affect large trees. Lidar-biomass relationships between canopy turnover and field measurements of coarse woody debris were modest (R 2  ≈ 0.3), given similar coarse woody debris production and Lidar-derived changes in canopy volume from single tree and multiple branch fall events. Our findings suggest that El Niño conditions accelerated canopy turnover in central Amazon forests, increasing coarse woody debris production by 62% to 1.22 Mg C ha -1  yr -1 in drought years . No claim to original US Government works New Phytologist © 2018 New Phytologist Trust.

Progressive forest canopy water loss during the 2012-2015 California drought.

PubMed

Asner, Gregory P; Brodrick, Philip G; Anderson, Christopher B; Vaughn, Nicholas; Knapp, David E; Martin, Roberta E

2016-01-12

The 2012-2015 drought has left California with severely reduced snowpack, soil moisture, ground water, and reservoir stocks, but the impact of this estimated millennial-scale event on forest health is unknown. We used airborne laser-guided spectroscopy and satellite-based models to assess losses in canopy water content of California's forests between 2011 and 2015. Approximately 10.6 million ha of forest containing up to 888 million large trees experienced measurable loss in canopy water content during this drought period. Severe canopy water losses of greater than 30% occurred over 1 million ha, affecting up to 58 million large trees. Our measurements exclude forests affected by fire between 2011 and 2015. If drought conditions continue or reoccur, even with temporary reprieves such as El Niño, we predict substantial future forest change.

A correlation analysis of percent canopy closure versus TMS spectral response for selected forest sites in the San Juan National Forest, Colorado

NASA Technical Reports Server (NTRS)

Butera, M. K.

1983-01-01

The correlation of canopy closure with the signal response of individual thematic mapper simulator (TMS) bands for selected forest sites in the San Juan National Forest, Colorado was investigated. Ground truth consisted of a photointerpreted determination of percent canopy closure of 0 to 100 percent for 32 sites. The sites selected were situated on plateaus at an elevation of approximately 3 km with slope or = 10 percent. The predominant tree species were ponderosa pine and aspen. The mean TMS response per band per site was calculated from data acquired by aircraft during mid-September, 1981. A correlation analysis of TMS response vs. canopy closure resulted in the following correlation coefficients for bands 1 through 7, respectively: -0.757, -0.663, -0.666, -0.088, -0.797, -0.763. Two model regressions were applied to the TMS data set to create a map of predicted percent forest canopy closure for the study area. Results indicated percent predictive accuracies of 71, 74, and 57 for percent canopy closure classes of 0-25, 25-75, and 75-100, respectively.

Analysis of hyperspectral data for estimation of temperate forest canopy nitrogen concentration: comparison between an airborne (AVIRIS) and a spaceborne (Hyperion) sensor

Treesearch

Marie-Louise Smith; Mary E. Martin; Lucie Plourde; Scott V. Ollinger

2003-01-01

Field studies among diverse biomes demonstrate that mass-based nitrogen concentration at leaf and canopy scales is strongly related to carbon uptake and cycling. Combined field and airborne imaging spectrometry studies demonstrate the capacity for accurate empirical estimation of forest canopy N concentration and other biochemical constituents at scales from forest...

A GIS-based tool for estimating tree canopy cover on fixed-radius plots using high-resolution aerial imagery

Treesearch

Sara A. Goeking; Greg C. Liknes; Erik Lindblom; John Chase; Dennis M. Jacobs; Robert. Benton

2012-01-01

Recent changes to the Forest Inventory and Analysis (FIA) Program's definition of forest land precipitated the development of a geographic information system (GIS)-based tool for efficiently estimating tree canopy cover for all FIA plots. The FIA definition of forest land has shifted from a density-related criterion based on stocking to a 10 percent tree canopy...

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.

[Functional diversity characteristics of canopy tree species of Jianfengling tropical montane rainforest on Hainan Island, China.

PubMed

Xu, Ge Xi; Shi, Zuo Min; Tang, Jing Chao; Liu, Shun; Ma, Fan Qiang; Xu, Han; Liu, Shi Rong; Li, Yi de

2016-11-18

Based on three 1-hm 2 plots of Jianfengling tropical montane rainforest on Hainan Island, 11 commom used functional traits of canopy trees were measured. After combining with topographical factors and trees census data of these three plots, we compared the impacts of weighted species abundance on two functional dispersion indices, mean pairwise distance (MPD) and mean nearest taxon distance (MNTD), by using single- and multi-dimensional traits, respectively. The relationship between functional richness of the forest canopies and species abundance was analyzed. We used a null model approach to explore the variations in standardized size effects of MPD and MNTD, which were weighted by species abundance and eliminated the influences of species richness diffe-rences among communities, and assessed functional diversity patterns of the forest canopies and their responses to local habitat heterogeneity at community's level. The results showed that variation in MPD was greatly dependent on the dimensionalities of functional traits as well as species abundance. The correlations between weighted and non-weighted MPD based on different dimensional traits were relatively weak (R=0.359-0.628). On the contrary, functional traits and species abundance had relatively weak effects on MNTD, which brought stronger correlations between weighted and non-weighted MNTD based on different dimensional traits (R=0.746-0.820). Functional dispersion of the forest canopies were generally overestimated when using non-weighted MPD and MNTD. Functional richness of the forest canopies showed an exponential relationship with species abundance (F=128.20; R 2 =0.632; AIC=97.72; P＜0.001), which might exist a species abundance threshold value. Patterns of functional diversity of the forest canopies based on different dimensional functional traits and their habitat responses showed variations in some degree. Forest canopies in the valley usually had relatively stronger biological competition, and functional diversity was higher than expected functional diversity randomized by null model, which indicated dispersed distribution of functional traits among canopy tree species in this habitat. However, the functional diversity of the forest canopies tended to be close or lower than randomization in the other habitat types, which demonstrated random or clustered distribution of the functional traits among canopy tree species.

Water Vapor Exchange in a Costa Rican Lower Montane Tropical Forest

NASA Astrophysics Data System (ADS)

Andrews, R.; Miller, G. R.; Cahill, A. T.; Moore, G. W.; Aparecido, L. M. T.

2015-12-01

Because of high canopy interception in tropical forests, evaporation from wet canopy surfaces makes up a sizeable portion of the total water vapor flux. The modeling complexities presented by changing canopy wetness, along with a scarcity of land-atmosphere flux exchange data from tropical forests, means evapotranspiration (ET) processes have been poorly represented in the tropics in land-surface modeling schemes. To better understand tropical forest ET, we will evaluate the influence of canopy wetness and various micrometeorological data on ET partitioning and total ET flux. We have collected flux data from a lower montane forest in Costa Rica at a newly established AmeriFlux site, which notably has the highest mean annual precipitation of any site in the network. The site features a 39-m canopy tower, equipped with two eddy covariance systems (LI-7200, LI-COR), a CO2/H2O atmospheric profile system (AP200, Campbell Scientific), leaf wetness sensors (LWS, Decagon Devices), sap flow sensors, and a soil respiration chamber (LI-8100A, LI-COR) as well as an array of other micrometeorological sensors. At the site, total ET is driven primarily by available energy, and to a lesser extent, by vapor pressure deficit. Average daily latent energy fluxes peak at values of 160, 75, and 35 W m-2 for dry, partially wet, and wet canopy conditions respectively. Correlations between latent energy flux and all other variables are strongest for drier canopy conditions. Complex relationships between canopy wetness and tropical forest ET cause the environmental controls on these fluxes to be significantly different from those in other biomes. As a result, a new modeling paradigm is needed to more accurately model ET differences between tropical forests and other vegetation types.

The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii)

PubMed Central

Chappell, Jackie; Phillips, Abigail C.; van Noordwijk, Maria A.; Mitra Setia, Tatang; Thorpe, Susannah K. S.

2015-01-01

For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence. Orangutans have developed a diverse range of locomotor behaviour to cross gaps between trees, which vary in their physical and cognitive demands. The aims of this study were to examine the ontogeny of orangutan gap crossing behaviours and to determine which factors influence the distance orangutans crossed. A non-invasive photographic technique was used to quantify forearm length as a measure of body size. We also recorded locomotor behaviour, support use and the distance crossed between trees. Our results suggest that gap crossing varies with both physical and cognitive development. More complex locomotor behaviours, which utilized compliant trunks and lianas, were used to cross the largest gaps, but these peaked in frequency much earlier than expected, between the ages of 4 and 5 years old, which probably reflects play behaviour to perfect locomotor techniques. Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation. Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size. PMID:26154061

The Ontogeny of Gap Crossing Behaviour in Bornean Orangutans (Pongo pygmaeus wurmbii).

PubMed

Chappell, Jackie; Phillips, Abigail C; van Noordwijk, Maria A; Mitra Setia, Tatang; Thorpe, Susannah K S

2015-01-01

For orangutans, the largest predominantly arboreal primates, discontinuous canopy presents a particular challenge. The shortest gaps between trees lie between thin peripheral branches, which offer the least stability to large animals. The affordances of the forest canopy experienced by orangutans of different ages however, must vary substantially as adult males are an order of magnitude larger in size than infants during the early stages of locomotor independence. Orangutans have developed a diverse range of locomotor behaviour to cross gaps between trees, which vary in their physical and cognitive demands. The aims of this study were to examine the ontogeny of orangutan gap crossing behaviours and to determine which factors influence the distance orangutans crossed. A non-invasive photographic technique was used to quantify forearm length as a measure of body size. We also recorded locomotor behaviour, support use and the distance crossed between trees. Our results suggest that gap crossing varies with both physical and cognitive development. More complex locomotor behaviours, which utilized compliant trunks and lianas, were used to cross the largest gaps, but these peaked in frequency much earlier than expected, between the ages of 4 and 5 years old, which probably reflects play behaviour to perfect locomotor techniques. Smaller individuals also crossed disproportionately large gaps relative to their size, by using support deformation. Our results suggest that orangutans acquire the full repertoire of gap crossing techniques, including the more cognitively demanding ones, before weaning, but adjust the frequency of the use of these techniques to their increasing body size.

Airborne Laser Scanning of Forest Stem Volume in a Mountainous Environment

PubMed Central

Hollaus, Markus; Wagner, Wolfgang; Maier, Bernhard; Schadauer, Klemens

2007-01-01

Airborne laser scanning (ALS) is an active remote sensing technique that uses the time-of-flight measurement principle to capture the three-dimensional structure of the earth's surface with pulsed lasers that transmit nanosecond-long laser pulses with a high pulse repetition frequency. Over forested areas most of the laser pulses are reflected by the leaves and branches of the trees, but a certain fraction of the laser pulses reaches the forest floor through small gaps in the canopy. Thus it is possible to reconstruct both the three-dimensional structure of the forest canopy and the terrain surface. For the retrieval of quantitative forest parameters such as stem volume or biomass it is necessary to use models that combine ALS with inventory data. One approach is to use multiplicative regression models that are trained with local inventory data. This method has been widely applied over boreal forest regions, but so far little experience exists with applying this method for mapping alpine forest. In this study the transferability of this approach to a 128 km2 large mountainous region in Vorarlberg, Austria, was evaluated. For the calibration of the model, inventory data as operationally collected by Austrian foresters were used. Despite these inventory data are based on variable sample plot sizes, they could be used for mapping stem volume for the entire alpine study area. The coefficient of determination R2 was 0.85 and the root mean square error (RMSE) 90.9 m3ha−1 (relative error of 21.4%) which is comparable to results of ALS studies conducted over topographically less complex environments. Due to the increasing availability, ALS data could become an operational part of Austrian's forest inventories.

Investigating the Relationships between Canopy Characteristics and Snow Depth Distribution at Fine Scales: Preliminary Results from the SnowEX TLS Campaign

NASA Astrophysics Data System (ADS)

Glenn, N. F.; Uhlmann, Z.; Spaete, L.; Tennant, C.; Hiemstra, C. A.; McNamara, J.

2017-12-01

Predicting changes in forested seasonal snowpacks under altered climate scenarios is one of the most pressing hydrologic challenges facing today's society. Airborne- and satellite-based remote sensing methods hold the potential to transform measurements of terrestrial water stores in snowpack, improve process representations of snowpack accumulation and ablation, and to generate high quality predictions that inform potential strategies to better manage water resources. While the effects of forest on snowpack are well documented, many of the fine-scale processes influenced by the forest-canopy are not directly accounted for because most snow models don't explicitly represent canopy structure and canopy heterogeneity. This study investigates the influence of forest canopy on snowpack distribution at fine scales and quantifies the influence of canopy heterogeneity on snowpack accumulation and ablation processes. We use terrestrial laser scanning (TLS) data collected during the SnowEX campaign to discover how the relationships between canopy and snow distributions change across scales. Our sample scales range from individual trees to patches of trees across the Grand Mesa, CO, SnowEx site.

Non-timber forest products: alternative multiple-uses for sustainable forest management

Treesearch

James L. Chamberlain; Mary Predny

2003-01-01

Forests of the southern United States are the source of a great diversity of flora, much of which is gathered for non-timber forest products (NTFPs). These products are made from resources that grow under the forest canopy as trees, herbs, shrubs, vines, moss and even lichen. They occur naturally in forests or may be cultivated under the forest canopy or in...

On the Relationship Between Hyperspectral Data and Foliar Nitrogen Content in Closed Canopy Forests

NASA Astrophysics Data System (ADS)

Knyazikhin, Y.; Schull, M.; Lepine, L. C.; Stenberg, P.; Mõttus, M.; Rautiainen, M.; Latorre, P.; Myneni, R.; Kaufmann, R.

2011-12-01

The importance of nitrogen for terrestrial ecosystem carbon dynamics and its climate feedback has been well recognized by the ecological community. Interaction between carbon and nitrogen at leaf level is among the fundamental mechanisms that directly control the dynamics of terrestrial vegetation carbon. This process influences absorption and scattering of solar radiation by foliage, which in turn impacts radiation reflected by the vegetation and measured by satellite sensors. NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) and ground based data on canopy structure and foliage nitrogen concentration acquired over six sites in Maine, New England, Florida, North Carolina and Washington were analyzed to assess the role of canopy structure, leaf optics and its biochemical constituents in the spectral variation of radiation reflected by the forest. The study sites represent closed canopy forests (LAI~5). Our results suggest: 1. Impact of canopy structure is so strong that it can significantly suppress the sensitivity of hyperspectral data to leaf optics. 2. Forest reflectance spectra in the interval [710, 790 nm] are required to obtain the fraction of the total leaf area that a "sensor sees" in a given direction. For closed canopy forests its retrieval does not require canopy reflectance models, suggesting that canopy reflectance spectra in this interval provide a direct estimate of the leaf area fraction. 3. The leaf area fraction fully explains variation in measured reflectance spectra due to variation in canopy structure. This variable is used to estimate the mean leaf scattering over foliage that the "sensor sees." For example the nadir-viewing AVIRIS sensor accumulates foliage optical properties over 25% of the total foliage area in needle leaf forest and about 50% in broadleaf forest. 4. Leaf surface properties have an impact on forest reflectivity, lowering its sensitivity to leaf absorbing pigments. 5. Variation in foliar nitrogen concentration can explain up to 55% of variation in AVIRIS spectra in the interval between 400 and 900 nm. The remaining factors could be due to (a) impact of leaf surface properties and/or (b) under-sampling of leaf optical properties due to the single view of the AVIRIS sensor. The theory of canopy spectral invariants underlies the separation of leaf scattering from the total canopy reflectance spectrum.

From open to closed canopy: A century of change in Douglas-fir forest, Orcas Island, Washington

USGS Publications Warehouse

Peterson, D.L.; Hammer, R.D.

2001-01-01

During the past century, forest structure on south-facing slopes of Mount Constitution, Orcas Island, Washington, has changed from open-grown Douglas-fir (Pseudotsuga menziesii) mixed with prairie to primarily closed canopy forest. Density of open-grown Douglas-fir was approximately 7 stems/ha in the 19th century, while current density of trees in closed-canopy mature forest is 426 stems/ha. Trees occur at intermediate densities in areas of transition from savanna-like stands to closed canopy. Analysis of fire scars indicates that at least seven fires have occurred on Mount Constitution since 1736, but only one fire has occurred since 1893, which suggests that the recent increase in stem density has been caused primarily by fire exclusion. The high stem densities currently found in this landscape put the relict (120-350+ years old) Douglas-fir at risk from contemporary fires, which would likely be high-intensity crown fires. Given the transition of forests on Orcas Island during the 20th century to closed canopy structure, undisturbed open-grown coniferous forest is now extremely rare in the San Juan Islands.

Effects of structural complexity on within-canopy light environments and leaf traits in a northern mixed deciduous forest

NASA Astrophysics Data System (ADS)

Fotis, A. T.; Curtis, P.

2016-12-01

Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in four co-dominant species (Acer rubrum, Fagus grandifolia, Pinus strobus and Quercus rubra) at different heights in plots with similar leaf area index (LAI) but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaves of F. grandifolia, Q. rubra, and P. strobus shifted towards sun-acclimation phenotypes with increasing canopy complexity while leaves of A. rubrum became more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further acclimation by increasing Narea and reducing Chlmass as LMA increased, while P. strobus showed no change in Narea and Chlmass with increasing LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic disturbances cause structural changes in the canopy.

Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests

PubMed Central

Košulič, Ondřej; Michalko, Radek; Hula, Vladimír

2016-01-01

Traditional woodland management created a mosaic of differently aged patches providing favorable conditions for a variety of arthropods. After abandonment of historical ownership patterns and traditional management and the deliberate transformation to high forest after World War II, large forest areas became darker and more homogeneous. This had significant negative consequences for biodiversity. An important question is whether even small-scale habitat structures maintained by different levels of canopy openness in abandoned coppiced forest may constitute conditions suitable for forest as well as open habitat specialists. We investigated the effect of canopy openness in former traditionally coppiced woodlands on the species richness, functional diversity, activity density, conservation value, and degree of rareness of epigeic spiders. In each of the eight studied locations, 60-m-long transect was established consisting of five pitfall traps placed at regular 15 m intervals along the gradient. Spiders were collected from May to July 2012. We recorded 90 spider species, including high proportions of xeric specialists (40%) and red-listed threatened species (26%). The peaks of conservation indicators, as well as spider community abundance, were shifted toward more open canopies. On the other hand, functional diversity peaked at more closed canopies followed by a rapid decrease with increasing canopy openness. Species richness was highest in the middle of the canopy openness gradient, suggesting an ecotone effect. Ordinations revealed that species of conservation concern tended to be associated with sparse and partly opened canopy. The results show that the various components of biodiversity peaked at different levels of canopy openness. Therefore, the restoration and suitable forest management of such conditions will retain important diversification of habitats in formerly coppiced oak forest stands. We indicate that permanent presence of small-scale improvements could be suitable conservation tools to prevent the general decline of woodland biodiversity in the intensified landscape of Central Europe. PMID:26845431

Comprehensive monitoring of Bangladesh tree cover inside and outside of forests, 2000-2014

NASA Astrophysics Data System (ADS)

Potapov, P.; Siddiqui, B. N.; Iqbal, Z.; Aziz, T.; Zzaman, B.; Islam, A.; Pickens, A.; Talero, Y.; Tyukavina, A.; Turubanova, S.; Hansen, M. C.

2017-10-01

A novel approach for satellite-based comprehensive national tree cover change assessment was developed and applied in Bangladesh, a country where trees outside of forests play an important role in the national economy and carbon sequestration. Tree cover change area was quantified using the integration of wall-to-wall Landsat-based mapping with a higher spatial resolution sample-based assessment. The total national tree canopy cover area was estimated as 3165 500 ± 186 600 ha in the year 2000, with trees outside forests making up 54% of total canopy cover. Total tree canopy cover increased by 135 700 (± 116 600) ha (4.3%) during the 2000-2014 time interval. Bangladesh exhibits a national tree cover dynamic where net change is rather small, but gross dynamics significant and variable by forest type. Despite the overall gain in tree cover, results revealed the ongoing clearing of natural forests, especially within the Chittagong hill tracts. While forests decreased their tree cover area by 83 600 ha, the trees outside forests (including tree plantations, village woodlots, and agroforestry) increased their canopy area by 219 300 ha. Our results demonstrated method capability to quantify tree canopy cover dynamics within a fine-scale agricultural landscape. Our approach for comprehensive monitoring of tree canopy cover may be recommended for operational implementation in Bangladesh and other countries with significant tree cover outside of forests.

Modeling Diurnal and Seasonal 3D Light Profiles in Amazon Forests

NASA Astrophysics Data System (ADS)

Morton, D. C.; Rubio, J.; Gastellu-Etchegorry, J.; Cook, B. D.; Hunter, M. O.; Yin, T.; Nagol, J. R.; Keller, M. M.

2013-12-01

The complex horizontal and vertical structure in tropical forests generates a diversity of light environments for canopy and understory trees. These 3D light profiles are dynamic on diurnal and seasonal time scales based on changes in solar illumination and the fraction of diffuse light. Understanding this variability is critical for improving ecosystem models and interpreting optical and LiDAR remote sensing data from tropical forests. Here, we initialized the Discrete Anisotropic Radiative Transfer (DART) model using dense airborne LiDAR data (>20 returns m2) from three forest sites in the central and eastern Amazon. Forest scenes derived from airborne LiDAR data were tested using modeled and observed large-footprint LiDAR data from the ICESat-GLAS sensor. Next, diurnal and seasonal profiles of photosynthetically active radiation (PAR) for each forest site were simulated under clear sky and cloudy conditions using DART. Incident PAR was summarized for canopy, understory, and ground levels. Our study illustrates the importance of realistic canopy models for accurate representation of LiDAR and optical radiative transfer. In particular, canopy rugosity and ground topography information from airborne LiDAR data provided critical 3D information that cannot be recreated using stem maps and allometric relationships for crown dimensions. The spatial arrangement of canopy trees altered PAR availability, even for dominant individuals, compared to downwelling measurements from nearby eddy flux towers. Pseudo-realistic branch and leaf architecture was also essential for recreating multiple scattering within canopies at near-infrared wavelengths commonly used for LiDAR remote sensing and quantifying PAR attenuation from shading within and between canopies. These findings point to the need for more spatial information on forest structure to improve the representation of light availability in models of tropical forest productivity.

Responses of Two Litter-Based Invertebrate Communities to Changes in Canopy Cover in a Forest Subject to Hurricanes

Treesearch

Barbara Richardson; Michael Richardson; Grizelle González

2018-01-01

Tropical forests are subject to seasonal hurricanes resulting in cycles of canopy opening and deposition of litter, followed by periods of recovery and canopy closure. Herein, we review two studies of litter-based communities in Puerto Rico; (i) a survey of bromeliad invertebrates in three montane forest types along an elevational gradient in 1993–1997, during a period...

Architecture of the Black Moshannon forest canopy measured by hemispherical photographs and a LI-COR LAI-2000 sensor

Treesearch

Y. S. Wang; J. Welles; D. R. Miller; D. E. Anderson; G. Heisler; M. McManus

1991-01-01

Non-destructive measurements of light penetration were made at 10 heights in the canopy on twelve different sites in the PA oak forest where the Blackmo 88 spray-micrometeorological experiment was conducted. Vertical profiles of Leaf Area Index, LAI, were calculated from these measurements, and the data were used to define the spatial variability of the forest canopy...

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.

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.

Functional traits enhance invasiveness of bamboos over co-occurring tree saplings in the semideciduous Atlantic Forest

NASA Astrophysics Data System (ADS)

Montti, Lía; Villagra, Mariana; Campanello, Paula I.; Gatti, M. Genoveva; Goldstein, Guillermo

2014-01-01

Many woody bamboo species are forest understory plants that become invasive after disturbance. They can grow rapidly forming a dense, nearly monospecific understory that inhibits tree regeneration. The principal aim of this study was to understand what functional traits of bamboos allow them to outcompete tree seedlings and saplings and become successful species in the semideciduous Atlantic Forests of northeastern Argentina. We studied leaf and whole-plant functional traits of two bamboo species of the genus Chusquea and five co-occurring saplings of common tree species growing under similar solar radiation and soil nutrient availabilities. Nutrient addition had no effect on bamboo or tree sapling survival and growth after two years. Tree species with high-light requirements had higher growth rates and developed relatively thin leaves with high photosynthetic capacity per unit leaf area and short leaf life-span when growing in gaps, but had lower survival rates in the understory. The opposite pattern was observed in shade-tolerant species that were able to survive in the understory but had lower photosynthetic capacity and growth than light-requiring species in gaps. Bamboos exhibited a high plasticity in functional traits and leaf characteristics that enabled them to grow rapidly in gaps (e.g., higher photosynthetic capacity per unit dry mass and clonal reproduction in gaps than in the understory) but at the same time to tolerate closed-canopy conditions (they had thinner leaves and a relatively longer leaf life-span in the understory compared to gaps). Photosynthetic capacity per unit dry mass was higher in bamboos than in trees. Bamboo plasticity in key functional traits, such as clonal reproduction at the plant level and leaves with a relatively low C cost and high photosynthesis rates, allows them to colonize disturbed forests with consequences at the community and ecosystem levels. Increasing disturbance in some forests worldwide will likely enhance bamboo invasion resulting in profound negative impacts on forest diversity, structure and function in the long term.

Induced spatial heterogeneity in forest canopies: responses of small mammals.

Treesearch

A.B. Carey

2001-01-01

We hypothesized that creating a mosaic of interspersed patches of different densities of canopy trees in a second-growth Douglas-fir (Pseudotsuga menziesiz) forest would accelerate development of biocomplexity (diversity in ecosystem structure, composition, and processes) by promoting spatial heterogeneity in understory, midstory, and canopy,...

Effects of Canopy Wetness on Evapotranspiration in Native and Invaded Tropical Montane Cloud Forest in Hawai‘i

NASA Astrophysics Data System (ADS)

Giambelluca, T. W.; Delay, J. K.; Takahashi, M.; Mudd, R. G.; Huang, M.; Asner, G. P.; Martin, R. E.; Nullet, M. A.

2009-12-01

Canopy wetness has profound effects on ecosystem processes. Canopy-atmosphere gas and energy exchanges are strongly altered when leaves are wetted by rainfall, fog, or dew. In some tropical forests, wet-canopy evaporation contributes a large portion of total evapotranspiration. On the other hand, transpiration is minimized when leaves are wet. The overall hydrological effects of canopy wetting depend on the canopy structure and on the frequency and duration of wetting events. At two field sites in Hawai‘i, one within native Metrosideros polymorpha forest and the other at a site heavily invaded by Psidium cattleianum, we are conducting measurements of canopy water balance, stand-level evapotranspiration (ET), transpiration (using sapflow techniques), energy balance, and related processes. Preliminary canopy water balance results show that wet canopy evaporation is 588 mm/yr (33% of potential ET) at the native site and 376 mm/yr (22% of potential ET) at the invaded site. Based on sapflow measurements in canopy branches, mean transpiration for partially and fully wetted canopy periods (categorized using leaf wetness sensor observations) was 47% and 17% of dry canopy transpiration at the native forest site. For the invaded site, transpiration for partially and fully wetted canopy periods was 67% and 33% of dry canopy transpiration. It appears that the invaded site is able to maintain higher transpiration rates, along with lower wet-canopy evaporation rates, during wet-canopy periods. Previously reported stand level measurements have shown that total ET represents a larger portion of available energy at the invaded site than the native site. These findings suggest that alien plant invasion is shifting evaporative water loss from wet-canopy evaporation to transpiration, while increasing overall water loss. Higher transpiration is likely to be associated with higher rates of carbon exchange, which may contribute to the success of this invasive tree.

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.

Estimating canopy bulk density and canopy base height for conifer stands in the interior Western United States using the Forest Vegetation Simulator Fire and Fuels Extension.

Treesearch

Seth Ex; Frederick Smith; Tara Keyser; Stephanie Rebain

2017-01-01

The Forest Vegetation Simulator Fire and Fuels Extension (FFE-FVS) is often used to estimate canopy bulk density (CBD) and canopy base height (CBH), which are key indicators of crown fire hazard for conifer stands in the Western United States. Estimated CBD from FFE-FVS is calculated as the maximum 4 m running mean bulk density of predefined 0.3 m thick canopy layers (...

Establishment and spread of Microstegium vimineum (Japanese stiltgrass) in closed-canopy forests

Treesearch

Cynthia D. Huebner

2011-01-01

Establishment and spread of Microstegium vimineum, an invasive exotic grass, in closed-canopy U.S. eastern forests were evaluated across a local (roadside to forest interior) and regional (across two geographic provinces) environmental gradient.

Non-timber forest products enterprises in the south: perceived distribution and implications for sustainable forest management

Treesearch

J.L. Chamberlain; M. Predny

2003-01-01

Forests of the southern United States are the source of a great diversity of flora, much of which is gathered to produce non-timber forest products (NTFPs). These products are made from resources that grow under the forest canopy as trees, herbs, shrubs, vines, moss and even lichen. They occur naturally in forests or may be cultivated under the forest canopy or in...

Influence of canopy traits on spatio-temporal variability of throughfall in Mediterranean Downy oak and Scots pine stands

NASA Astrophysics Data System (ADS)

Llorens, Pilar; Garcia-Estringana, Pablo; Latron, Jérôme; Molina, Antonio J.; Gallart, Francesc

2014-05-01

The spatio-temporal variability of throughfall is the result of the interaction of biotic factors, related to the canopy traits, and abiotic factors, linked to the meteorological conditions. This variability may lead to significant differences in the volume of water and solutes that reach the ground in each location, and beyond in the hydrological and biogeochemical dynamics of forest soils. Two forest stands in Mediterranean climatic conditions were studied to analyse the role of biotic and abiotic factors in the temporal and spatial redistribution of throughfall. The monitored stands are a Downy oak forest (Quercus pubescens) and a Scots pine forest (Pinus sylvestris), both located in the Vallcebre research catchments (NE Spain, 42º 12'N, 1º 49'E). The study plots are representative of Mediterranean mountain areas with spontaneous afforestation by Scots pine as a consequence of the abandonment of agricultural terraces, formerly covered by Downy oaks. The monitoring design of each plot consisted of a set of 20 automatic rain recorders and 40 automatic soil moisture probes located below the canopy. 100 hemispheric photographs of the canopy were used to place the instruments at representative locations (in terms of canopy cover) within the plot. Bulk rainfall, stemflow and meteorological conditions above the forest cover were also automatically recorded. Canopy cover as well as biometric characteristics of the plots were also regularly measured. The results indicate a temporal persistence of throughfall in both stands, as observed elsewhere. However, for the oak plot the seasonal evolution of canopy traits added additional variability, with higher variability in summer and different locations of wet and dry spots depending on the season. Furthermore, this work investigates the influence of canopy structure on the spatial variability of throughfall by analysing a large set of forest parameters, from main canopy traits to detailed leaves and wood characteristics. The analysis includes the consideration of the interaction of main abiotic factors with canopy traits.

High manoeuvring costs force narrow-winged molossid bats to forage in open space.

PubMed

Voigt, Christian C; Holderied, Marc W

2012-04-01

Molossid bats are specialised aerial-hawkers that, like their diurnal ecological counterparts, swallows and swifts, hunt for insects in open spaces. The long and narrow wings of molossids are considered energetically adapted to fast flight between resource patches, but less suited for manoeuvring in more confined spaces, such as between tree-tops or in forest gaps. To understand whether a potential increase in metabolic costs of manoeuvring excludes molossids from foraging in more confined spaces, we measured energy costs and speed of manoeuvring flight in two tropical molossids, 18 g Molossus currentium and 23 g Molossus sinaloae, when flying in a ~500 m(3) hexagonal enclosure (~120 m(2) area), which is of similar dimensions as typical forest gaps. Flight metabolism averaged 10.21 ± 3.00 and 11.32 ± 3.54 ml CO(2) min(-1), and flight speeds 5.65 ± 0.47 and 6.27 ± 0.68 m s(-1) for M. currentium and M. sinaloae respectively. Metabolic rate during flight was higher for the M. currentium than for the similar-sized, but broader-winged frugivore Carollia sowelli, corroborating that broad-winged bats are better adapted to flying in confined spaces. These higher metabolic costs of manoeuvring flight may be caused by having to fly slower than the optimal foraging speed, and by the additional metabolic costs for centripetal acceleration in curves. This may preclude molossids from foraging efficiently between canopy trees or in forest gaps. The surprisingly brief burst of foraging activity at dusk of many molossids might be related to the cooling of the air column after sunset, which drives airborne insects to lower strata. Accordingly, foraging activity of molossids may quickly turn unprofitable when the abundance of insects decreases above the canopy.

Estimating Chemical Exchange between Atmospheric Deposition and Forest Canopy in Guizhou, China.

PubMed

Li, Wei; Gao, Fang; Liao, Xueqin

2013-01-01

To evaluate the effects of atmospheric deposition on forest ecosystems, wet-only precipitation and throughfall samples were collected in two forest types (Masson pine [ Lamb.] forests and mixed conifer and broadleaf forests) in the Longli forest in the Guizhou province of southwestern China for a period of 21 successive months from April 2007 to December 2008. The pH and chemical components of precipitation and throughfall were analyzed. In addition, the canopy budget model was applied to distinguish between in-canopy and atmospheric sources of chemical compounds. Canopy leaching and total potentially acidifying deposition fluxes were calculated. The results showed that the average pH and the concentration of ions in throughfall were higher than those in precipitation, with the exception of the NH concentration. Dry deposition of S and N accumulated more in Masson pine forests than in mixed conifer and broadleaf forests. Canopy leaching was the most significant source of base cations in forest throughfall, which was higher in the mixed forests than in the coniferous forests. Anions in throughfall deposition in Masson pine forests exceeded those in the mixed forests. Higher total potentially acidifying deposition fluxes reflected the more effective amounts of acid delivered to Masson pine forests compared with mixed conifer and broadleaf forests. In addition, acid deposition induced the leaching and loss of nutrient ions such as Mg, K, and Ca. Although the trees of the studied areas have not shown any symptoms of cation loss, a potentially harmful influence was engendered by atmospheric deposition in the two forest types in the Longli area. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Current remote sensing approaches to monitoring forest degradation in support of countries measurement, reporting and verification (MRV) systems for REDD.

PubMed

Mitchell, Anthea L; Rosenqvist, Ake; Mora, Brice

2017-12-01

Forest degradation is a global phenomenon and while being an important indicator and precursor to further forest loss, carbon emissions due to degradation should also be accounted for in national reporting within the frame of UN REDD+. At regional to country scales, methods have been progressively developed to detect and map forest degradation, with these based on multi-resolution optical, synthetic aperture radar (SAR) and/or LiDAR data. However, there is no one single method that can be applied to monitor forest degradation, largely due to the specific nature of the degradation type or process and the timeframe over which it is observed. The review assesses two main approaches to monitoring forest degradation: first, where detection is indicated by a change in canopy cover or proxies, and second, the quantification of loss (or gain) in above ground biomass (AGB). The discussion only considers degradation that has a visible impact on the forest canopy and is thus detectable by remote sensing. The first approach encompasses methods that characterise the type of degradation and track disturbance, detect gaps in, and fragmentation of, the forest canopy, and proxies that provide evidence of forestry activity. Progress in these topics has seen the extension of methods to higher resolution (both spatial and temporal) data to better capture the disturbance signal, distinguish degraded and intact forest, and monitor regrowth. Improvements in the reliability of mapping methods are anticipated by SAR-optical data fusion and use of very high resolution data. The second approach exploits EO sensors with known sensitivity to forest structure and biomass and discusses monitoring efforts using repeat LiDAR and SAR data. There has been progress in the capacity to discriminate forest age and growth stage using data fusion methods and LiDAR height metrics. Interferometric SAR and LiDAR have found new application in linking forest structure change to degradation in tropical forests. Estimates of AGB change have been demonstrated at national level using SAR and LiDAR-assisted approaches. Future improvements are anticipated with the availability of next generation LiDAR sensors. Improved access to relevant satellite data and best available methods are key to operational forest degradation monitoring. Countries will need to prioritise their monitoring efforts depending on the significance of the degradation, balanced against available resources. A better understanding of the drivers and impacts of degradation will help guide monitoring and restoration efforts. Ultimately we want to restore ecosystem service and function in degraded forests before the change is irreversible.

Evidence for substantial forestry canopy processing of nitrogen deposition using isotopic tracer experiments in low deposition conditions

NASA Astrophysics Data System (ADS)

Ferraretto, Daniele; Heal, Kate

2017-04-01

Temperate forest ecosystems are significant sinks for nitrogen deposition (Ndep) yielding benefits such as protection of waterbodies from eutrophication and enhanced sequestration of atmospheric CO2. Previous studies have shown evidence of biological nitrification and Ndep processing and retention in forest canopies. However, this was reported only at sites with high environmental or experimentally enhanced rates of Ndep (˜18 kg N ha-1 y-1) and has not yet been demonstrated in low Ndep environments. We have used bulk field hydrochemical measurements and labelled isotopic experiments to assess canopy processing in a lower Ndep environment (˜7 kg N ha-1 year-1) at a Sitka spruce plantation in Perthshire, Scotland, representing the dominant tree species (24%) in woodlands in Great Britain. Analysis of 4.5 years of measured N fluxes in rainfall (RF) and fogwater onto the canopy and throughfall (TF) and stemflow (SF) below the canopy suggests strong transformation and uptake of Ndep in the forest canopy. Annual canopy Ndep uptake was ˜4.7 kg N ha-1 year-1, representing 60-76% of annual Ndep. To validate these plot-scale results and track N uptake within the forest canopy in different seasons, double 15N-labelled NH4NO3 (98%) solution was sprayed in summer and winter onto the canopy of three trees at the measurement site. RF, TF and SF samples have been collected and analysed for 15NH4 and 15NO3. Comparing the amount of labelled N recovered under the sample trees with the measured δ15N signal is expected to provide further evidence of the role of forest canopies in actively processing and retaining atmospheric N deposition.

Measurement of snow interception and canopy effects on snow accumulation and melt in a mountainous maritime climate, Oregon, United States

NASA Astrophysics Data System (ADS)

Storck, Pascal; Lettenmaier, Dennis P.; Bolton, Susan M.

2002-11-01

The results of a 3 year field study to observe the processes controlling snow interception by forest canopies and under canopy snow accumulation and ablation in mountain maritime climates are reported. The field study was further intended to provide data to develop and test models of forest canopy effects on beneath-canopy snowpack accumulation and melt and the plot and stand scales. Weighing lysimeters, cut-tree experiments, and manual snow surveys were deployed at a site in the Umpqua National Forest, Oregon (elevation 1200 m). A unique design for a weighing lysimeter was employed that allowed continuous measurements of snowpack evolution beneath a forest canopy to be taken at a scale unaffected by variability in canopy throughfall. Continuous observations of snowpack evolution in large clearings were made coincidentally with the canopy measurements. Large differences in snow accumulation and ablation were observed at sites beneath the forest canopy and in large clearings. These differences were not well described by simple relationships between the sites. Over the study period, approximately 60% of snowfall was intercepted by the canopy (up to a maximum of about 40 mm water equivalent). Instantaneous sublimation rates exceeded 0.5 mm per hour for short periods. However, apparent average sublimation from the intercepted snow was less than 1 mm per day and totaled approximately 100 mm per winter season. Approximately 72 and 28% of the remaining intercepted snow was removed as meltwater drip and large snow masses, respectively. Observed differences in snow interception rate and maximum snow interception capacity between Douglas fir (Pseudotsuga menziesii), white fir (Abies concolor), ponderosa pine (Pinus ponderosa), and lodgepole pine (Pinus contorta) were minimal.

Vertical heterogeneity in predation pressure in a temperate forest canopy

PubMed Central

Aikens, Kathleen R.; Buddle, Christopher M.

2013-01-01

The forest canopy offers a vertical gradient across which variation in predation pressure implies variation in refuge quality for arthropods. Direct and indirect experimental approaches were combined to assess whether canopy strata differ in ability to offer refuge to various arthropod groups. Vertical heterogeneity in impact of avian predators was quantified using exclosure cages in the understory, lower, mid, and upper canopy of a north-temperate deciduous forest near Montreal, Quebec. Bait trials were completed in the same strata to investigate the effects of invertebrate predators. Exclusion of birds yielded higher arthropod densities across all strata, although treatment effects were small for some taxa. Observed gradients in predation pressure were similar for both birds and invertebrate predators; the highest predation pressure was observed in the understory and decreased with height. Our findings support a view of the forest canopy that is heterogeneous with respect to arthropod refuge from natural enemies. PMID:24010017

Estimation of regional surface resistance to evapotranspiration from NDVI and thermal-IR AVHRR data. [Normalized Difference Vegetation Index

NASA Technical Reports Server (NTRS)

Nemani, Ramakrishna R.; Running, Steven W.

1989-01-01

Infrared surface temperatures from satellite sensors have been used to infer evaporation and soil moisture distribution over large areas. However, surface energy partitioning to latent versus sensible heat changes with surface vegetation cover and water availability. The hypothesis that the relationship between surface temperature and canopy density is sensitivite to seasonal changes in canopy resistance of conifer forests is presently tested. Surface temperature and canopy density were computed for a 20 x 25 km forested region in Montana, from the NOAA/AVHRR for 8 days during the summer of 1985. A forest ecosystem model, FOREST-BGC, simulated canopy resistance for the same period. For all eight days, surface temperatures had high association with canopy density, measured as Normalized Difference Vegetation Index, implying that latent heat exchange is the major cause of spatial variations in surface radiant tmeperatures.

Ecophysiological Remote Sensing of Leaf-Canopy Photosynthetic Characteristics in a Cool-Temperate Deciduous Forest in Japan

NASA Astrophysics Data System (ADS)

Noda, H. M.; Muraoka, H.

2014-12-01

Satellite remote sensing of structure and function of canopy is crucial to detect temporal and spatial distributions of forest ecosystems dynamics in changing environments. The spectral reflectance of the canopy is determined by optical properties (spectral reflectance and transmittance) of single leaves and their spatial arrangements in the canopy. The optical properties of leaves reflect their pigments contents and anatomical structures. Thus detailed information and understandings of the consequence between ecophysiological traits and optical properties from single leaf to canopy level are essential for remote sensing of canopy ecophysiology. To develop the ecophysiological remote sensing of forest canopy, we have been promoting multiple and cross-scale measurements in "Takayama site" belonging to AsiaFlux and JaLTER networks, located in a cool-temperate deciduous broadleaf forest on a mountainous landscape in Japan. In this forest, in situ measurement of canopy spectral reflectance has been conducted continuously by a spectroradiometer as part of the "Phenological Eyes Network (PEN)" since 2004. To analyze the canopy spectral reflectance from leaf ecophysiological viewpoints, leaf mass per area, nitrogen content, chlorophyll contents, photosynthetic capacities and the optical properties have been measured for dominant canopy tree species Quercus crispla and Betula ermanii throughout the seasons for multiple years.Photosynthetic capacity was largely correlated with chlorophyll contents throughout the growing season in both Q. crispla and B. ermanii. In these leaves, the reflectance at "red edge" (710 nm) changed by corresponding to the changes of chlorophyll contents throughout the seasons. Our canopy-level examination showed that vegetation indices obtained by red edge reflectance have linear relationship with leaf chlorophyll contents and photosynthetic capacity. Finally we apply this knowledge to the Rapid Eye satellite imagery around Takayama site to scale-up the leaf-level findings to canopy and landscape levels on a mountainous landscape.

Experimental evaluation of the significance of the pressure transport term for the Turbulence Kinetic Energy Budget across contrasting forest architectures

NASA Astrophysics Data System (ADS)

Ehrnsperger, Laura; Wunder, Tobias; Thomas, Christoph

2017-04-01

Forests are one of the dominant vegetation types on Earth and are an important sink for carbon on our planet. Forests are special ecosystems due to their great canopy height und complex architecture consisting of a subcanopy and a canopy layer, which changes the mechanisms of turbulent exchange within the plant canopy. To date, the sinks and sources of turbulence in forest canopies are not completely understood, especially the role of the pressure transport remains unclear. The INTRAMIX experiment was conducted in a mountainous Norway spruce (Picea abies) forest at the Fluxnet Waldstein site (DE-Bay) in Bavaria, Germany, for a period of 10 weeks in order to experimentally evaluate the significance of the pressure transport to the TKE budget for the first time. The INTRAMIX data of the dense mountain forest was compared to observations from a sparse Ponderosa pine (Pinus ponderosa) stand in Oregon, USA, to study the influence of forest architecture. We hypothesized that the pressure transport is more important in dense forest canopies as the crown decouples the subcanopy from the buoyancy- and shear-driven flow above the canopy. It is also investigated how atmospheric stability influences the TKE budget. Based upon model results from literature we expect the pressure transport to act as a source for TKE especially under free convective and unstable dynamic stability. Results to date indicate that pressure transport is most important in the subcanopy with decreasing magnitude with increasing height. Nevertheless, pressure transport is a continuous source of TKE above the canopy, while in the canopy and subcanopy layer pressure transport acts both as a sink and source term for TKE. In the tree crown layer pressure transport is a source in the morning and afternoon hours and acts as a sink during the evening, while in the subcanopy pressure transport is a source around noon and during the night and acts as a sink in the early morning and afternoon hours. This complementary pattern suggests that the pressure transport is an important means for exchanging TKE across canopy layers.

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.

Amblyomma tapirellum  (Acari: Ixodidae) collected from tropical forest canopy

PubMed Central

Loaiza, Jose R; Miller, Matthew J; Bermingham, Eldredge; Sanjur, Oris I; Jansen, Patrick A; Rovira, Jose R; Alvarez, Eric; Rodriguez, Eric; Davis, Philip; Dutari, Larissa C; Pecor, James; Foley, Desmond; Radtke, Meghan; Pongsiri, Montira J

2014-01-01

Free-ranging ticks are widely known to be restricted to the ground level of vegetation. Here, we document the capture of the tick species Amblyomma tapirellum in light traps placed in the forest canopy of Barro Colorado Island, central Panama. A total of forty eight adults and three nymphs were removed from carbon dioxide–octenol baited CDC light traps suspended 20 meters above the ground during surveys for forest canopy mosquitoes. To our knowledge, this represents the first report of questing ticks from the canopy of tropical forests. Our finding suggests a novel ecological relationship between A. tapirellum and arboreal mammals, perhaps monkeys that come to the ground to drink or to feed on fallen fruits. PMID:25075277

Estimating average tree crown size using spatial information from Ikonos and QuickBird images: Across-sensor and across-site comparisons

Treesearch

Conghe Song; Matthew B. Dickinson; Lihong Su; Su Zhang; Daniel Yaussey

2010-01-01

The forest canopy is the medium for energy, mass, and momentum exchanges between the forest ecosystem and the atmosphere. Tree crown size is a critical aspect of canopy structure that significantly influences these biophysical processes in the canopy. Tree crown size is also strongly related to other canopy structural parameters, such as tree height, diameter at breast...

Difficulties with estimating city-wide urban forest cover change from national, remotely-sensed tree canopy maps

Treesearch

Jeffrey T. Walton

2008-01-01

Two datasets of percent urban tree canopy cover were compared. The first dataset was based on a 1991 AVHRR forest density map. The second was the US Geological Survey's National Land Cover Database (NLCD) 2001 sub-pixel tree canopy. A comparison of these two tree canopy layers was conducted in 36 census designated places of western New York State. Reference data...

A Regional Simulation to Explore Impacts of Resource Use and Constraints

DTIC Science & Technology

2007-03-01

mountaintops. (10) Deciduous Forest - This class is composed of forests, which contain at least 75% deciduous trees in the canopy, deciduous ... trees , pine plantations, and evergreen woodlands. (12) Mixed Forest - This class includes forests with mixed deciduous /coniferous canopies, natural...reflective surfaces. Classification of forested wetlands dominated by deciduous trees is probably more accurate than that in areas with 104

Use of LIDAR for forest inventory and forest management application

Treesearch

Birgit Peterson; Ralph Dubayah; Peter Hyde; Michelle Hofton; J. Bryan Blair; JoAnn Fites-Kaufman

2007-01-01

A significant impediment to forest managers has been the difficulty in obtaining large-area forest structure and fuel characteristics at useful resolutions and accuracies. This paper demonstrates how LIDAR data were used to predict canopy bulk density (CBD) and canopy base height (CBH) for an area in the Sierra National Forest. The LIDAR data were used to generate maps...

Soil types and forest canopy structures in southern Missouri: A first look with AIS data

NASA Technical Reports Server (NTRS)

Green, G. M.; Arvidson, R. E.

1986-01-01

Spectral reflectance properties of deciduous oak-hickory forests covering the eastern half of the Rolla Quadrangle were examined using Thematic Mapper (TM) data acquired in August and December, 1982 and Airborne Imaging Spectrometer (AIS) data acquired in August, 1985. For the TM data distinctly high relative reflectance values (greater than 0.3) in the near infrared (Band 4, 0.73 to 0.94 micrometers) correspond to regions characterized by xeric (dry) forests that overlie soils with low water retention capacities. These soils are derived primarily from rhyolites. More mesic forests characterized by lower TM band 4 relative reflectances are associated with soils of higher retention capacities derived predominately from non-cherty carbonates. The major factors affecting canopy reflectance appear to be the leaf area index (LAI) and leaf optical properties. The Suits canopy reflectance model predicts the relative reflectance values for the xeric canopies. The mesic canopy reflectance is less well matched and incorporation of canopy shadowing caused by the irregular nature of the mesic canopy may be necessary. Preliminary examination of high spectral resolution AIS data acquired in August of 1985 reveals no more information than found in the broad band TM data.

Discriminating Canopy Structural Types from Optical Properties using AVIRIS Data in the Sierra National Forest in Central California

NASA Astrophysics Data System (ADS)

Huesca Martinez, M.; Garcia, M.; Roth, K. L.; Casas, A.; Ustin, S.

2015-12-01

There is a well-established need within the remote sensing community for improved estimation of canopy structure and understanding of its influence on the retrieval of leaf biochemical properties. The aim of this project was to evaluate the estimation of structural properties directly from hyperspectral data, with the broader goal that these might be used to constrain retrievals of canopy chemistry. We used NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) to discriminate different canopy structural types, defined in terms of biomass, canopy height and vegetation complexity, and compared them to estimates of these properties measured by LiDAR data. We tested a large number of optical metrics, including single narrow band reflectance and 1st derivative, sub-pixel cover fractions, narrow-band indices, spectral absorption features, and Principal Component Analysis components. Canopy structural types were identified and classified from different forest types by integrating structural traits measured by optical metrics using the Random Forest (RF) classifier. The classification accuracy was above 70% in most of the vegetation scenarios. The best overall accuracy was achieved for hardwood forest (>80% accuracy) and the lowest accuracy was found in mixed forest (~70% accuracy). Furthermore, similarly high accuracy was found when the RF classifier was applied to a spatially independent dataset, showing significant portability for the method used. Results show that all spectral regions played a role in canopy structure assessment, thus the whole spectrum is required. Furthermore, optical metrics derived from AVIRIS proved to be a powerful technique for structural attribute mapping. This research illustrates the potential for using optical properties to distinguish several canopy structural types in different forest types, and these may be used to constrain quantitative measurements of absorbing properties in future research.

Towards ground-truthing of spaceborne estimates of above-ground biomass and leaf area index in tropical rain forests

NASA Astrophysics Data System (ADS)

Köhler, P.; Huth, A.

2010-05-01

The canopy height of forests is a key variable which can be obtained using air- or spaceborne remote sensing techniques such as radar interferometry or lidar. If new allometric relationships between canopy height and the biomass stored in the vegetation can be established this would offer the possibility for a global monitoring of the above-ground carbon content on land. In the absence of adequate field data we use simulation results of a tropical rain forest growth model to propose what degree of information might be generated from canopy height and thus to enable ground-truthing of potential future satellite observations. We here analyse the correlation between canopy height in a tropical rain forest with other structural characteristics, such as above-ground biomass (AGB) (and thus carbon content of vegetation) and leaf area index (LAI). The process-based forest growth model FORMIND2.0 was applied to simulate (a) undisturbed forest growth and (b) a wide range of possible disturbance regimes typically for local tree logging conditions for a tropical rain forest site on Borneo (Sabah, Malaysia) in South-East Asia. It is found that for undisturbed forest and a variety of disturbed forests situations AGB can be expressed as a power-law function of canopy height h (AGB=a·hb) with an r2~60% for a spatial resolution of 20 m×20 m (0.04 ha, also called plot size). The regression is becoming significant better for the hectare wide analysis of the disturbed forest sites (r2=91%). There seems to exist no functional dependency between LAI and canopy height, but there is also a linear correlation (r2~60%) between AGB and the area fraction in which the canopy is highly disturbed. A reasonable agreement of our results with observations is obtained from a comparison of the simulations with permanent sampling plot data from the same region and with the large-scale forest inventory in Lambir. We conclude that the spaceborne remote sensing techniques have the potential to quantify the carbon contained in the vegetation, although this calculation contains due to the heterogeneity of the forest landscape structural uncertainties which restrict future applications to spatial averages of about one hectare in size. The uncertainties in AGB for a given canopy height are here 20-40% (95% confidence level) corresponding to a standard deviation of less than ±10%. This uncertainty on the 1 ha-scale is much smaller than in the analysis of 0.04 ha-scale data. At this small scale (0.04 ha) AGB can only be calculated out of canopy height with an uncertainty which is at least of the magnitude of the signal itself due to the natural spatial heterogeneity of these forests.

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.

Lidar observed seasonal variation of vertical canopy structure in the Amazon evergreen forests

NASA Astrophysics Data System (ADS)

Tang, H.; Dubayah, R.

2017-12-01

Both light and water are important environmental factors governing tree growth. Responses of tropical forests to their changes are complicated and can vary substantially across different spatial and temporal scales. Of particular interest is the dry-season greening-up of Amazon forests, a phenomenon undergoing considerable debates whether it is real or a "light illusion" caused by artifacts of passive optical remote sensing techniques. Here we analyze seasonal dynamic patterns of vertical canopy structure in the Amazon forests using lidar observations from NASA's Ice, Cloud, and and land Elevation Satellite (ICESat). We found that the net greening of canopy layer coincides with the wet-to-dry transition period, and its net browning occurs mostly at the late dry season. The understory also shows a seasonal cycle, but with an opposite variation to canopy and minimal correlation to seasonal variations in rainfall or radiation. Our results further suggest a potential interaction between canopy layers in the light regime that can optimize the growth of Amazon forests during the dry season. This light regime variability that exists in both spatial and temporal domains can better reveal the dry-season greening-up phenomenon, which appears less obvious when treating the Amazon forests as a whole.

Height is more important than light in determining leaf morphology in a tropical forest.

PubMed

Cavaleri, Molly A; Oberbauer, Steven F; Clark, David B; Clark, Deborah A; Ryan, Michael G

2010-06-01

Both within and between species, leaf physiological parameters are strongly related to leaf dry mass per area (LMA, g/m2), which has been found to increase from forest floor to canopy top in every forest where it has been measured. Although vertical LMA gradients in forests have historically been attributed to a direct phenotypic response to light, an increasing number of recent studies have provided evidence that water limitation in the upper canopy can constrain foliar morphological adaptations to higher light levels. We measured height, light, and LMA of all species encountered along 45 vertical canopy transects across a Costa Rican tropical rain forest. LMA was correlated with light levels in the lower canopy until approximately 18 m sample height and 22% diffuse transmittance. Height showed a remarkably linear relationship with LMA throughout the entire vertical canopy profile for all species pooled and for each functional group individually (except epiphytes), possibly through the influence of gravity on leaf water potential and turgor pressure. Models of forest function may be greatly simplified by estimating LMA-correlated leaf physiological parameters solely from foliage height profiles, which in turn can be assessed with satellite- and aircraft-based remote sensing.

Mechanisms of nitrogen deposition effects on temperate forest lichens and trees

USGS Publications Warehouse

Carter, Therese S.; Clark, Christopher M.; Fenn, Mark E.; Jovan, Sarah E.; Perakis, Steven; Riddell, Jennifer; Schaberg, Paul G.; Greaver, Tara; Hastings, Meredith

2017-01-01

We review the mechanisms of deleterious nitrogen (N) deposition impacts on temperate forests, with a particular focus on trees and lichens. Elevated anthropogenic N deposition to forests has varied effects on individual organisms depending on characteristics both of the N inputs (form, timing, amount) and of the organisms (ecology, physiology) involved. Improved mechanistic knowledge of these effects can aid in developing robust predictions of how organisms respond to either increases or decreases in N deposition. Rising N levels affect forests in micro- and macroscopic ways from physiological responses at the cellular, tissue, and organism levels to influencing individual species and entire communities and ecosystems. A synthesis of these processes forms the basis for the overarching themes of this paper, which focuses on N effects at different levels of biological organization in temperate forests. For lichens, the mechanisms of direct effects of N are relatively well known at cellular, organismal, and community levels, though interactions of N with other stressors merit further research. For trees, effects of N deposition are better understood for N as an acidifying agent than as a nutrient; in both cases, the impacts can reflect direct effects on short time scales and indirect effects mediated through long-term soil and belowground changes. There are many gaps on fundamental N use and cycling in ecosystems, and we highlight the most critical gaps for understanding potential deleterious effects of N deposition. For lichens, these gaps include both how N affects specific metabolic pathways and how N is metabolized. For trees, these gaps include understanding the direct effects of N deposition onto forest canopies, the sensitivity of different tree species and mycorrhizal symbionts to N, the influence of soil properties, and the reversibility of N and acidification effects on plants and soils. Continued study of how these N response mechanisms interact with one another, and with other dimensions of global change, remains essential for predicting ongoing changes in lichen and tree populations across North American temperate forests.

The 2008 South China Freeze and its Impact on the Forests

NASA Astrophysics Data System (ADS)

Zhou, B.; Ai, C.; Wang, Y.; Li, Z.; Cao, Y.; Wang, X.

2008-12-01

An unprecedented calamity caused by snow and freezing rain occurred in South China in 2008. This freeze was closely related to the La Nina phenomenon according to a report from the World Meteorological Organization. The freeze stroke 19 provinces in China, and damaged forests of 19.33 million ha with a standing volume loss of 371 million m3. It is estimated that the direct economic loss in the form of destroyed forests is over $8 billion. The indirect loss in the form of impaired ecological functions, such as water and soil conservation, water resources conservancy, biodiversity and forest carbon pool etc is enormous. The calamity of snow and freezing rain affected the structure and function of forest ecosystems. The snow load and freezing rain caused mechanical damage to the trees, with the species of Pinus massoniana, Cunninghamia lanceolata, Pinus elliottii and Phyllostachys pubescens etc. being the most seriously affected. The cold weather could also cause the physiological hurt to the trees. The change of the biotic components leads to the change of abiotic components in the ecosystems. The sunlight under the canopy was intensified due to the opening up of the canopy. The air temperature in the forest, the nutrient and microorganism in soil, the litterfall dynamic were also affected. The alteration of the forest ecosystem structure brought in the alteration of its functions. The damage of the ecosystem structure weakened the capacity of the water and soil conservation, water resources conservancy and reduced the biodiversity in forest ecosystems. Forest gaps allow more sunlight into the freeze-damaged ecosystem, inducing the invasion of more masculine species. The direction and progress of the community succession was therefore altered. At the same time, the freeze made a great impact on the stability and health of the forest ecosystem, increasing the potential risk of outbreak of forest fire and plant diseases/insect pests. Some suggestions on the rebuilding and recovery of damaged forest were given in this paper.

Forest Stand Canopy Structure Attribute Estimation from High Resolution Digital Airborne Imagery

Treesearch

Demetrios Gatziolis

2006-01-01

A study of forest stand canopy variable assessment using digital, airborne, multispectral imagery is presented. Variable estimation involves stem density, canopy closure, and mean crown diameter, and it is based on quantification of spatial autocorrelation among pixel digital numbers (DN) using variogram analysis and an alternative, non-parametric approach known as...

Comparison of five canopy cover estimation techniques in the western Oregon Cascades.

Treesearch

Anne C.S. Fiala; Steven L. Garman; Andrew N. Gray

2006-01-01

Estimates of forest canopy cover are widely used in forest research and management, yet methods used to quantify canopy cover and the estimates they provide vary greatly. Four commonly used ground-based techniques for estimating overstory cover - line-intercept, spherical densiometer, moosehorn, and hemispherical photography - and cover estimates generated from crown...

Contrasting spatial patterns in active-fire and fire-suppressed Mediterranean climate old-growth mixed conifer forests.

PubMed

Fry, Danny L; Stephens, Scott L; Collins, Brandon M; North, Malcolm P; Franco-Vizcaíno, Ernesto; Gill, Samantha J

2014-01-01

In Mediterranean environments in western North America, historic fire regimes in frequent-fire conifer forests are highly variable both temporally and spatially. This complexity influenced forest structure and spatial patterns, but some of this diversity has been lost due to anthropogenic disruption of ecosystem processes, including fire. Information from reference forest sites can help management efforts to restore forests conditions that may be more resilient to future changes in disturbance regimes and climate. In this study, we characterize tree spatial patterns using four-ha stem maps from four old-growth, Jeffrey pine-mixed conifer forests, two with active-fire regimes in northwestern Mexico and two that experienced fire exclusion in the southern Sierra Nevada. Most of the trees were in patches, averaging six to 11 trees per patch at 0.007 to 0.014 ha(-1), and occupied 27-46% of the study areas. Average canopy gap sizes (0.04 ha) covering 11-20% of the area were not significantly different among sites. The putative main effects of fire exclusion were higher densities of single trees in smaller size classes, larger proportion of trees (≥ 56%) in large patches (≥ 10 trees), and decreases in spatial complexity. While a homogenization of forest structure has been a typical result from fire exclusion, some similarities in patch, single tree, and gap attributes were maintained at these sites. These within-stand descriptions provide spatially relevant benchmarks from which to manage for structural heterogeneity in frequent-fire forest types.

Below-Canopy Isoprene Nitrate Chemistry and Dynamics in a Mixed Coniferous/Deciduous Forest Canopy during the 2016 PROPHET-AMOS Summer Field Campaign.

NASA Astrophysics Data System (ADS)

Desrochers, S. J.; Slade, J. H., Jr.; Shepson, P. B.; Alwe, H. D.; Millet, D. B.; Kavassalis, S.; Shi, Q.; Murphy, J. G.; Bloss, W.; Wood, E.; Stevens, P. S.; Mauldin, L.; Cantrell, C. A.; Kim, T.; Zhou, X.; Helmig, D.; Shutter, J. D.; Rivera, J. C.; Keutsch, F. N.; Flynn, J. H., III; Alvarez, S. L.; Erickson, M.; Wang, W.; Griffin, R. J.; Bui, A. T.; Kim, K.; Wallace, H. W., IV

2017-12-01

Isoprene is the most abundant biogenic volatile organic compound (BVOC) emitted in forest ecosystems. Isoprene hydroxynitrates (IN) can be produced via OH oxidation of isoprene in the presence of NOx, thereby sequestering NOx, and limiting ozone production. Furthermore, IN can lead to the formation of secondary organic aerosols (SOA), which affect air quality and radiative forcing. Forest environments are often complex in terms of isoprene emission as a function of height through the canopy, and to date, there has been little study of chemistry below the canopy. However, the above- and below-canopy environments can be quite different, e.g. in terms of irradiance, NOx, and temperature. Thus, for example, there can be significantly more nitrate radical chemistry below canopy during daytime. Here we present and discuss IN measurements from the 2016 PROPHET-AMOS summer field campaign at the University of Michigan Biological Station (UMBS). IN was sampled from inlets at two heights, below the canopy and within the canopy, using a single quadrupole chemical ionization mass spectrometer, using I- ion chemistry. Differences in [IN] measured from the two inlets varied throughout the campaign, indicating a difference in the importance of light and dark dominated IN production pathways. Measurements of isoprene, terpenes, OH, HONO, HCHO, NOx, O3, HO2, H2O, jO3, jNO2, and jNO3 values conducted during the campaign were used to constrain a 0-D box model to simulate IN concentrations in order to better understand the influence of local-scale chemistry on IN production and destruction, and mixing below and through the forest canopy. Here we will compare measurements with model results, and discuss the implications for IN processing and mixing under the canopy and for nitrogen exchange above and below the forest canopy environment.

Attaining the canopy in dry and moist tropical forests: strong differences in tree growth trajectories reflect variation in growing conditions

PubMed Central

Zuidema, Pieter A.; Martínez-Ramos, Miguel

2009-01-01

Availability of light and water differs between tropical moist and dry forests, with typically higher understorey light levels and lower water availability in the latter. Therefore, growth trajectories of juvenile trees—those that have not attained the canopy—are likely governed by temporal fluctuations in light availability in moist forests (suppressions and releases), and by spatial heterogeneity in water availability in dry forests. In this study, we compared juvenile growth trajectories of Cedrela odorata in a dry (Mexico) and a moist forest (Bolivia) using tree rings. We tested the following specific hypotheses: (1) moist forest juveniles show more and longer suppressions, and more and stronger releases; (2) moist forest juveniles exhibit wider variation in canopy accession pattern, i.e. the typical growth trajectory to the canopy; (3) growth variation among dry forest juveniles persists over longer time due to spatial heterogeneity in water availability. As expected, the proportion of suppressed juveniles was higher in moist than in dry forest (72 vs. 17%). Moist forest suppressions also lasted longer (9 vs. 5 years). The proportion of juveniles that experienced releases in moist forest (76%) was higher than in dry forest (41%), and releases in moist forests were much stronger. Trees in the moist forest also had a wider variation in canopy accession patterns compared to the dry forest. Our results also showed that growth variation among juvenile trees persisted over substantially longer periods of time in dry forest (>64 years) compared to moist forest (12 years), most probably because of larger persistent spatial variation in water availability. Our results suggest that periodic increases in light availability are more important for attaining the canopy in moist forests, and that spatial heterogeneity in water availability governs long-term tree growth in dry forests. Electronic supplementary material The online version of this article (doi:10.1007/s00442-009-1540-5) contains supplementary material, which is available to authorized users. PMID:20033820

Drought stress and carbon uptake in an Amazon forest measured with spaceborne imaging spectroscopy

PubMed Central

Asner, Gregory P.; Nepstad, Daniel; Cardinot, Gina; Ray, David

2004-01-01

Amazônia contains vast stores of carbon in high-diversity ecosystems, yet this region undergoes major changes in precipitation affecting land use, carbon dynamics, and climate. The extent and structural complexity of Amazon forests impedes ground studies of ecosystem functions such as net primary production (NPP), water cycling, and carbon sequestration. Traditional modeling and remote-sensing approaches are not well suited to tropical forest studies, because (i) biophysical mechanisms determining drought effects on canopy water and carbon dynamics are poorly known, and (ii) remote-sensing metrics of canopy greenness may be insensitive to small changes in leaf area accompanying drought. New spaceborne imaging spectroscopy may detect drought stress in tropical forests, helping to monitor forest physiology and constrain carbon models. We combined a forest drought experiment in Amazônia with spaceborne imaging spectrometer measurements of this area. With field data on rainfall, soil water, and leaf and canopy responses, we tested whether spaceborne hyperspectral observations quantify differences in canopy water and NPP resulting from drought stress. We found that hyperspectral metrics of canopy water content and light-use efficiency are highly sensitive to drought. Using these observations, forest NPP was estimated with greater sensitivity to drought conditions than with traditional combinations of modeling, remote-sensing, and field measurements. Spaceborne imaging spectroscopy will increase the accuracy of ecological studies in humid tropical forests. PMID:15071182

A forester's look at the application of image manipulation techniques to multitemporal Landsat data

NASA Technical Reports Server (NTRS)

Williams, D. L.; Stauffer, M. L.; Leung, K. C.

1979-01-01

Registered, multitemporal Landsat data of a study area in central Pennsylvania were analyzed to detect and assess changes in the forest canopy resulting from insect defoliation. Images taken July 19, 1976, and June 27, 1977, were chosen specifically to represent forest canopy conditions before and after defoliation, respectively. Several image manipulation and data transformation techniques, developed primarily for estimating agricultural and rangeland standing green biomass, were applied to these data. The applicability of each technique for estimating the severity of forest canopy defoliation was then evaluated. All techniques tested had highly correlated results. In all cases, heavy defoliation was discriminated from healthy forest. Areas of moderate defoliation were confused with healthy forest on northwest (NW) aspects, but were distinct from healthy forest conditions on southeast (SE)-facing slopes.

Amazon Forest Structure from IKONOS Satellite Data and the Automated Characterization of Forest Canopy Properties

Treesearch

Michael Palace; Michael Keller; Gregory P. Asner; Stephen Hagen; Bobby Braswell

2008-01-01

We developed an automated tree crown analysis algorithm using 1-m panchromatic IKONOS satellite images to examine forest canopy structure in the Brazilian Amazon. The algorithm was calibrated on the landscape level with tree geometry and forest stand data at the Fazenda Cauaxi (3.75◦ S, 48.37◦ W) in the eastern Amazon, and then compared with forest...

California Spotted Owl (Strix occidentalis occidentalis) habitat use patterns in a burned landscape

USGS Publications Warehouse

Eyes, Stephanie; Roberts, Susan L.; Johnson, Matthew D.

2017-01-01

Fire is a dynamic ecosystem process of mixed-conifer forests of the Sierra Nevada, but there is limited scientific information addressing wildlife habitat use in burned landscapes. Recent studies have presented contradictory information regarding the effects of stand-replacing wildfires on Spotted Owls (Strix occidentalis) and their habitat. While fire promotes heterogeneous forest landscapes shown to be favored by owls, high severity fire may create large canopy gaps that can fragment the closed-canopy habitat preferred by Spotted Owls. We used radio-telemetry to determine whether foraging California Spotted Owls (S. o. occidentalis) in Yosemite National Park, California, USA, showed selection for particular fire severity patch types within their home ranges. Our results suggested that Spotted Owls exhibited strong habitat selection within their home ranges for locations near the roost and edge habitats, and weak selection for lower fire severity patch types. Although owls selected high contrast edges with greater relative probabilities than low contrast edges, we did not detect a statistical difference between these probabilities. Protecting forests from stand-replacing fires via mechanical thinning or prescribed fire is a priority for management agencies, and our results suggest that fires of low to moderate severity can create habitat conditions within California Spotted Owls' home ranges that are favored for foraging.

Value of eddy-covariance data for individual-based, forest gap models

NASA Astrophysics Data System (ADS)

Roedig, Edna; Cuntz, Matthias; Huth, Andreas

2014-05-01

Individual-based forest gap models simulate tree growth and carbon fluxes on large time scales. They are a well established tool to predict forest dynamics and successions. However, the effect of climatic variables on processes of such individual-based models is uncertain (e.g. the effect of temperature or soil moisture on the gross primary production (GPP)). Commonly, functional relationships and parameter values that describe the effect of climate variables on the model processes are gathered from various vegetation models of different spatial scales. Though, their accuracies and parameter values have not been validated for the specific model scales of individual-based forest gap models. In this study, we address this uncertainty by linking Eddy-covariance (EC) data and a forest gap model. The forest gap model FORMIND is applied on the Norwegian spruce monoculture forest at Wetzstein in Thuringia, Germany for the years 2003-2008. The original parameterizations of climatic functions are adapted according to the EC-data. The time step of the model is reduced to one day in order to adapt to the high resolution EC-data. The FORMIND model uses functional relationships on an individual level, whereas the EC-method measures eco-physiological responses at the ecosystem level. However, we assume that in homogeneous stands as in our study, functional relationships for both methods are comparable. The model is then validated at the spruce forest Waldstein, Germany. Results show that the functional relationships used in the model, are similar to those observed with the EC-method. The temperature reduction curve is well reflected in the EC-data, though parameter values differ from the originally expected values. For example at the freezing point, the observed GPP is 30% higher than predicted by the forest gap model. The response of observed GPP to soil moisture shows that the permanent wilting point is 7 vol-% lower than the value derived from the literature. The light response curve, integrated over the canopy and the forest stand, is underestimated compared to the measured data. The EC-method measures a yearly carbon balance of 13 mol(CO2)m-2 for the Wetzstein site. The model with the original parameterization overestimates the yearly carbon balance by nearly 5 mol(CO2)m-2 while the model with an EC-based parameterization fits the measured data very well. The parameter values derived from EC-data are applied on the spruce forest Waldstein and clearly improve estimates of the carbon balance.

Deposition of aerially applied BT in an oak forest and its prediction with the FSCBG model

USGS Publications Warehouse

Anderson, Dean E.; Miller, David R.; Wang, Yansen; Yendol, William G.; Mierzejewski, Karl; McManus, Michael L.

1992-01-01

Data are provided from 17 single-swath aerial spray trials that were conducted over a fully leafed, 16-m tall, mixed oak forest. The distribution of cross-swath spray deposits was sampled at the top of the canopy and below the canopy. Micrometeorological conditions were measured above and within the canopy during the spray trials. The USDA Forest Service FSCBG (Forest Service-Cramer-Barry-Grim) model was run to predict the target sampler catch for each trial using forest stand, airplane-application-equipment configuration, and micrometeorological conditions as inputs. Observations showed an average cross-swath deposition of 100 IU cm−2 with large run-to-run variability in deposition patterns, magnitudes, and drift. Eleven percent of the spray material that reached the top of the canopy penetrated through the tree canopy to the forest floor.The FSCBG predictions of the ensemble-averaged deposition were within 17% of the measured deposition at the canopy top and within 8% on the ground beneath the canopy. Run-to-run deposit predictions by FSCBG were considerably less variable than the measured deposits. Individual run predictions were much less accurate than the ensemble-averaged predictions as demonstrated by an average root-mean-square-error (rmse) of 27.9 IU CM−2 at the top of the canopy. Comparisons of the differences between predicted and observed deposits indicated that the model accuracy was sensitive to atmospheric stability conditions. In neutral and stable conditions, a regular pattern of error was indicated by overprediction of the canopy-top deposit at distances from 0 to 20 m downwind from the flight line and underprediction of the deposit both farther downwind than 20 m and upwind of the flight line. In unstable conditions the model generally underpredicted the deposit downwind from the flight line, but showed no regular pattern of error.

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.

Diurnal Patterns of Direct Light Extinction in Two Tropical Forest Canopies

NASA Astrophysics Data System (ADS)

Cushman, K.; Silva, C. E.; Kellner, J. R.

2016-12-01

The extent to which net ecosystem production is light-limited in Neotropical forests is poorly understood. This is due in part to our limited knowledge of how light moves through complex canopies to different layers of leaves, and the extent to which structural changes in canopies modify the amount of light absorbed by the landscape to drive photosynthesis. Systematic diurnal changes in solar angle, leaf angle, and wind speed suggest that patterns of light attenuation change over the course of the day in tropical forests. In this study, we characterize the extinction of direct light through the canopies of two forests in Panama using high-resolution, three-dimensional measurements from a small footprint, discrete return airborne laser scanner mounted on the gondola of a canopy crane. We hypothesized that light penetrates deeper into canopies during the middle of the day because changes in leaf angle by light-saturated leaves temporarily reduce effective canopy leaf area, and because greater wind speeds increase sunflecks. Also, we hypothesized that rates of light extinction are greater in the wetter forest that receives less direct sunlight because light saturation in upper leaves is less prevalent. We collected laser measurements with resolution of approximately 5,000 points per square meter of ground every 90 minutes over the course of one day each at Parque Natural Metropolitano (1740 mm annual rainfall) and Parque Nacional San Lorenzo (3300 mm annual rainfall) during the dry season in April, 2016. Using a voxel-based approach, we compared the actual versus potential distance traveled by laser beams through each volume of the canopy. We fit an exponential model to quantify the rate of light extinction. We found that rates of light extinction vary spatially, temporally, and by site. These results indicate that variation in forest structure changes patterns of light attenuation through the canopy over multiple scales.

Disturbance, succession, and structural development of an upland hardwood forest on the Interior Low Plateau, Tennessee

Treesearch

Justin L. Hart; Merrit M. Cowden; Scott J. Torreano; J. Patrick R. Vestal

2017-01-01

We quantified species composition, stand structure, canopy disturbance history, and Quercus establishment and canopy accession patterns in an upland hardwood forest in Tennessee. The forest established in the mid-1800s and exhibited structural characteristics that were within the range of what has been reported from other late-successional forests...

Species composition and forest structure explain the temperature sensitivity patterns of productivity in temperate forests

NASA Astrophysics Data System (ADS)

Bohn, Friedrich J.; May, Felix; Huth, Andreas

2018-03-01

Rising temperatures due to climate change influence the wood production of forests. Observations show that some temperate forests increase their productivity, whereas others reduce their productivity. This study focuses on how species composition and forest structure properties influence the temperature sensitivity of aboveground wood production (AWP). It further investigates which forests will increase their productivity the most with rising temperatures. We described forest structure by leaf area index, forest height and tree height heterogeneity. Species composition was described by a functional diversity index (Rao's Q) and a species distribution index (ΩAWP). ΩAWP quantified how well species are distributed over the different forest layers with regard to AWP. We analysed 370 170 forest stands generated with a forest gap model. These forest stands covered a wide range of possible forest types. For each stand, we estimated annual aboveground wood production and performed a climate sensitivity analysis based on 320 different climate time series (of 1-year length). The scenarios differed in mean annual temperature and annual temperature amplitude. Temperature sensitivity of wood production was quantified as the relative change in productivity resulting from a 1 °C rise in mean annual temperature or annual temperature amplitude. Increasing ΩAWP positively influenced both temperature sensitivity indices of forest, whereas forest height showed a bell-shaped relationship with both indices. Further, we found forests in each successional stage that are positively affected by temperature rise. For such forests, large ΩAWP values were important. In the case of young forests, low functional diversity and small tree height heterogeneity were associated with a positive effect of temperature on wood production. During later successional stages, higher species diversity and larger tree height heterogeneity were an advantage. To achieve such a development, one could plant below the closed canopy of even-aged, pioneer trees a climax-species-rich understorey that will build the canopy of the mature forest. This study highlights that forest structure and species composition are both relevant for understanding the temperature sensitivity of wood production.

Alterations to throughfall water and solute flux by Tillandsias usneoides L. (Spanish moss) cover in a maritime live oak forest

NASA Astrophysics Data System (ADS)

Gay, T. E.; Van Stan, J. T., II; Reichard, J. S.; Moore, L. D.; Lewis, E. S.

2014-12-01

Alterations to forest canopy structures can have a direct effect on hydrological and biogeochemical cycles in forest ecosystems. Epiphytes act as additional canopy biomass intercepting water, effecting pathways under different micrometeorological conditions and alternating nutrient uptake/releases. Most studies on epiphyte cover have focused on non-vascular epiphytes (e.g., lichen and bryophyte mosses), leaving vascular epiphytes like Tillandsia usneoides L. (Spanish moss) relatively understudied. To fill this gap, we characterized alterations to throughfall water and dissolved ion enrichment/flux to soils by T. usneoides in a Quercus Virginiana Mill. (southern live oak) stand on St. Catherine's Island. Specifically, we compare throughfall generated from heavy T. usneoides coverage, bare canopy, and a continuum of T. usneoides cover percentages (~400 water & 210 chemistry observations over ~40 storms for each canopy cover category). Findings show T.usneoides acts as a significant water storage agent, significantly reducing throughfall. However, under certain meteorological conditions T. usneoides can become saturated and act as a funneling "hotspot." Tillandsia usneoides coverage enriched throughfall with primarily dry deposited ions (Na+,Cl-, SO42-, Li+), leached greater Mg2+, Ca2+, reduced NO3- and increased NH4+ concentrations. Dry deposited ion enrichment is likely a result of the moss' greater surface roughness. It has been shown that epiphytes prefer to leach Mg2+ and Ca2+. Increased NH4+ suggests that the saturated T. usneoides mat likely hosts microbial decomposition of leaf, branch, and bark biomass ensnared in the plant itself. K-means cluster analysis on the storms revealed 4 storm types of the differing meteorological conditions (windy/calm, dry/wet [high/low VPD], high/low intensity, intermittent/consistent), and these throughfall dynamics varied between these storm types. Discussion of future research questions regarding how these throughfall variations may impact ecological communities in the litter, soil, or understory vegetation is also provided.

Drying of Floodplain Forests Associated with Water-Level Decline in the Apalachicola River, Florida - Interim Results, 2006

USGS Publications Warehouse

Darst, Melanie R.; Light, Helen M.

2007-01-01

Floodplain forests of the Apalachicola River, Florida, are drier in composition today (2006) than they were before 1954, and drying is expected to continue for at least the next 50 years. Drier forest composition is probably caused by water-level declines that occurred as a result of physical changes in the main channel after 1954 and decreased flows in spring and summer months since the 1970s. Forest plots sampled from 2004 to 2006 were compared to forests sampled in the late 1970s (1976-79) using a Floodplain Index (FI) based on species dominance weighted by the Floodplain Species Category, a value that represents the tolerance of tree species to inundation and saturation in the floodplain and consequently, the typical historic floodplain habitat for that species. Two types of analyses were used to determine forest changes over time: replicate plot analysis comparing present (2004-06) canopy composition to late 1970s canopy composition at the same locations, and analyses comparing the composition of size classes of trees on plots in late 1970s and in present forests. An example of a size class analysis would be a comparison of the composition of the entire canopy (all trees greater than 7.5 cm (centimeter) diameter at breast height (dbh)) to the composition of the large canopy tree size class (greater than or equal to 25 cm dbh) at one location. The entire canopy, which has a mixture of both young and old trees, is probably indicative of more recent hydrologic conditions than the large canopy, which is assumed to have fewer young trees. Change in forest composition from the pre-1954 period to approximately 2050 was estimated by combining results from three analyses. The composition of pre-1954 forests was represented by the large canopy size class sampled in the late 1970s. The average FI for canopy trees was 3.0 percent drier than the average FI for the large canopy tree size class, indicating that the late 1970s forests were 3.0 percent drier than pre-1954 forests. The change from the late 1970s to the present was based on replicate plot analysis. The composition of 71 replicate plots sampled from 2004 to 2006 averaged 4.4 percent drier than forests sampled in the late 1970s. The potential composition of future forests (2050 or later) was estimated from the composition of the present subcanopy tree size class (less than 7.5 cm and greater than or equal to 2.5 cm dbh), which contains the greatest percentage of young trees and is indicative of recent hydrologic conditions. Subcanopy trees are the driest size class in present forests, with FIs averaging 31.0 percent drier than FIs for all canopy trees. Based on results from all three sets of data, present floodplain forests average 7.4 percent drier in composition than pre-1954 forests and have the potential to become at least 31.0 percent drier in the future. An overall total change in floodplain forests to an average composition 38.4 percent drier than pre-1954 forests is expected within approximately 50 years. The greatest effects of water-level decline have occurred in tupelo-cypress swamps where forest composition has become at least 8.8 percent drier in 2004-06 than in pre-1954 years. This change indicates that a net loss of swamps has already occurred in the Apalachicola River floodplain, and further losses are expected to continue over the next 50 years. Drying of floodplain forests will result in some low bottomland hardwood forests changing in composition to high bottomland hardwood forests. The composition of high bottomland hardwoods will also change, although periodic flooding is still occurring and will continue to limit most of the floodplain to bottomland hardwood species that are adapted to at least short periods of inundation and saturation.

Effects of structural complexity on within-canopy light environments and leaf traits in a northern mixed deciduous forest.

PubMed

Fotis, Alexander T; Curtis, Peter S

2017-10-01

Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in red maple (Acer rubrum), american beech (Fagus grandifolia), white pine (Pinus strobus), and northern red oak (Quercus rubra) at different heights in plots with similar leaf area index but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaf phenotypes of F. grandifolia, Q. rubra and P. strobus were more sun-acclimated in the midstory of structurally complex canopies while leaf phenotypes of A. rubrum were more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further differences in acclimation with increased Narea and reduced Chlmass in leaves with higher LMA, while P. strobus showed no change in Narea and Chlmass with higher LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic disturbances cause structural changes in the canopy. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Eo-1 Hyperion Measures Canopy Drought Stress In Amazonia

NASA Technical Reports Server (NTRS)

Asner, Gregory P.; Nepstad, Daniel; Cardinot, Gina; Moutinho, Paulo; Harris, Thomas; Ray, David

2004-01-01

The central, south and southeast portions of the Amazon Basin experience a period of decreased cloud cover and precipitation from June through November. There are likely important effects of seasonal and interannual rainfall variation on forest leaf area index, canopy water stress, productivity and regional carbon cycling in the Amazon. While both ground and spaceborne studies of precipitation continue to improve, there has been almost no progress made in observing forest canopy responses to rainfall variability in the humid tropics. This shortfall stems from the large stature of the vegetation and great spatial extent of tropical forests, both of which strongly impede field studies of forest responses to water availability. Those few studies employing satellite measures of canopy responses to seasonal and interannual drought (e.g., Bohlman et al. 1998, Asner et al. 2000) have been limited by the spectral resolution and sampling available from Landsat and AVHRR sensors. We report on a study combining the first landscape-level, managed drought experiment in Amazon tropical forest with the first spaceborne imaging spectrometer observations of this experimental area. Using extensive field data on rainfall inputs, soil water content, and both leaf and canopy responses, we test the hypothesis that spectroscopic signatures unique to hyperspectral observations can be used to quantify relative differences in canopy stress resulting from water availability.

Linking canopy phenology to the seasonality of biosphere-atmosphere interactions in a temperate deciduous forest (Invited)

NASA Astrophysics Data System (ADS)

Richardson, A. D.; Toomey, M. P.; Aubrecht, D.; Sonnentag, O.; Ryu, Y.; Hilker, T.

2013-12-01

Phenology - the annual rhythm of canopy development and senescence - is a key control on the seasonality of surface-atmosphere fluxes of CO2, water, and energy. Phenology is also a highly sensitive indicator of the biological impacts of climate change. In many biomes, there is strong evidence of trends towards earlier spring onset, and later autumn senescence, over the last four decades. These shifts in phenology may play an imprortant role in mitigating - or amplifying - feedbacks between terrestrial ecosystems and the climate system. To better understand relationships between canopy structure and function in a temperate deciduous forest, we installed a wide array of radiometric instruments and imaging sensors near the top of a 40-m high tower at Harvard Forest beginning in 2011. Our data set includes: - incoming and outgoing visible (including incoming direct and diffuse components), shortwave, and longwave radiation; - narrowband (five visible and three near-infrared channels) canopy reflectance; - leaf area index (LAI, from continuous below-canopy digital cover photography), fraction of absorbed photosynthetically active radiation (fAPAR, from above- and below-canopy quantum sensors), normalized difference vegetation index (NDVI, from broad- and narrow-band radiometric sensors), and photochemical reflectance index (PRI, from narrow-band radiometric sensors); - visible and near-infrared PhenoCam (http://phenocam.sr.unh.edu) canopy imagery; - multi-angular narrowband hyperspectral canopy reflectance (AMSPEC, in 2012); and - beginning in 2013, hyperspectral and thermal canopy imagery. Together with eddy covariance measurements of CO2 and water fluxes from the Harvard Forest AmeriFlux site, located in similar forest about 1 km to the east, on-the-ground visual observations of phenology, and continuous stem diameter measurements with automated band dendrometers, these data provide an unusually detailed view of phenological processes at scales from leaves to trees to the forest canopy. In this presentation I will discuss our efforts to use these data for model-based analyses that link phenology to biosphere-atmosphere interactions through the cycling of CO2, water and energy. As an example, I will describe how we are using a two-layer canopy model, in conjunction with both LAI data and narrowband reflectance indices, to improve model representation of the seasonal cycle of canopy photosynthesis and hence understanding of surface-atmosphere fluxes of CO2.

Norway maple displays greater seasonal growth and phenotypic plasticity to light than native sugar maple.

PubMed

Paquette, Alain; Fontaine, Bastien; Berninger, Frank; Dubois, Karine; Lechowicz, Martin J; Messier, Christian; Posada, Juan M; Valladares, Fernando; Brisson, Jacques

2012-11-01

Norway maple (Acer platanoides L), which is among the most invasive tree species in forests of eastern North America, is associated with reduced regeneration of the related native species, sugar maple (Acer saccharum Marsh) and other native flora. To identify traits conferring an advantage to Norway maple, we grew both species through an entire growing season under simulated light regimes mimicking a closed forest understorey vs. a canopy disturbance (gap). Dynamic shade-houses providing a succession of high-intensity direct-light events between longer periods of low, diffuse light were used to simulate the light regimes. We assessed seedling height growth three times in the season, as well as stem diameter, maximum photosynthetic capacity, biomass allocation above- and below-ground, seasonal phenology and phenotypic plasticity. Given the north European provenance of Norway maple, we also investigated the possibility that its growth in North America might be increased by delayed fall senescence. We found that Norway maple had significantly greater photosynthetic capacity in both light regimes and grew larger in stem diameter than sugar maple. The differences in below- and above-ground biomass, stem diameter, height and maximum photosynthesis were especially important in the simulated gap where Norway maple continued extension growth during the late fall. In the gap regime sugar maple had a significantly higher root : shoot ratio that could confer an advantage in the deepest shade of closed understorey and under water stress or browsing pressure. Norway maple is especially invasive following canopy disturbance where the opposite (low root : shoot ratio) could confer a competitive advantage. Considering the effects of global change in extending the potential growing season, we anticipate that the invasiveness of Norway maple will increase in the future.

Simple Forest Canopy Thermal Exitance Model

NASA Technical Reports Server (NTRS)

Smith J. A.; Goltz, S. M.

1999-01-01

We describe a model to calculate brightness temperature and surface energy balance for a forest canopy system. The model is an extension of an earlier vegetation only model by inclusion of a simple soil layer. The root mean square error in brightness temperature for a dense forest canopy was 2.5 C. Surface energy balance predictions were also in good agreement. The corresponding root mean square errors for net radiation, latent, and sensible heat were 38.9, 30.7, and 41.4 W/sq m respectively.

Temporal Variability of Stemflow Dissolved Organic Carbon (DOC) Concentrations and Quality from Morphologically Contrasting Deciduous Canopies

NASA Astrophysics Data System (ADS)

van Stan, J. T.; Levia, D. F.; Inamdar, S. P.; Mitchell, M. J.; Mage, S. M.

2010-12-01

Dissolved organic carbon (DOC) inputs from canopy-derived hydrologic fluxes play a significant role in the terrestrial carbon budgets of forested ecosystems. However, no studies known to the authors have examined the variability of both DOC concentrations and quality for stemflow across time scales, nor has any study to date evaluated the effects of canopy structure on stemflow DOC characteristics. This investigation seeks to rectify this knowledge gap by examining the variability of stemflow DOC concentrations and quality across contrasting canopy morphologies and time scales (seasonal, storm and intrastorm). Bulk and intrastorm stemflow samples from a less dense, rough-barked, more plagiophile (Liriodendron tulipifera L. (tulip poplar)) and a denser, thin-barked, more erectophile (Fagus grandifolia Ehrh. (American beech)) canopy were collected and analyzed for DOC quality using metrics derived from UV-vis spectroscopy (E2:E3 ratio, SUVA254, select spectral slope (S), and spectral slope ratios (SR)). Our results suggest that stemflow DOC concentrations and quality change as crown architectural traits enhance or diminish hydrologic retention time within the canopy. The architecture of L. tulipifera canopies likely retards the flow of intercepted water, increasing chemical exchange with bark and foliar surfaces. UV-vis metrics indicated that this increased chemical exchange, particularly with bark surfaces, generally enhanced aromatic hydrocarbon content and increased molecular weight. Because leaf presence influenced DOC quality, stemflow DOC characteristics also varied seasonally in response to canopy condition. At the inter- and intrastorm scale, stemflow DOC concentration and quality varied with meteorological and antecedent canopy conditions. Since recent studies have linked stemflow production to preferential subsurface transport of dissolved chemistries, trends in DOC speciation and fluxes described in this study may impact soil environments within wooded ecosystems.

Canopy structural complexity predicts forest canopy light absorption at continental scales

NASA Astrophysics Data System (ADS)

Atkins, J. W.; Fahey, R. T.; Hardiman, B. S.; Gough, C. M.

2017-12-01

Understanding how the physical structure of forest canopies influence light acquisition is a long-standing area of inquiry fundamental to advancing understanding of many areas of the physical sciences, including the modeling and interpretation of biogeochemical cycles. Conventional measures of forest canopy structure employed in earth system models are often limited to leaf area index (LAI)—a measure of the quantity of leaves in the canopy. However, more novel multi-dimensional measures of canopy structural complexity (CSC) that describe the arrangement of vegetation are now possible because of technological advances, and may improve modeled estimates of canopy light absorption. During 2016 and 2017, we surveyed forests at sites from across the eastern, southern, and midwestern United States using portable canopy LiDAR (PCL). This survey included 14 National Ecological Observation Network (NEON), Long-Term Ecological Research Network (LTER,) Ameriflux, and University affiliated sites. Our findings show that a composite model including CSC parameters and LAI explains 96.8% of the variance in light acquisition, measured as the fraction of photosynthetically absorbed radiation (fPAR) at the continental scale, and improvement of 12% over an LAI only model. Under high light sky conditions, measures of CSC are more strongly coupled with light acquisition than under low light, possibly because light scattering partially decouples CSC from canopy light absorption under low, predominately diffuse light conditions. We conclude that scalable estimates of CSC metrics may improve continent-wide estimates of canopy light absorption and, therefore, carbon uptake, with implications for remote sensing and earth system modeling.

UWScat observations of snow on Grand Mesa, Colorado - Backscatter and polarimetric response of snow in a canopy and snow on the ground

NASA Astrophysics Data System (ADS)

Thompson, A. D.; Kelly, R. E. J.

2017-12-01

The ability to measure the amount of water stored in Earth's terrestrial snowpack is important for human development, resource management, and environmental modelling. Active microwave remote sensing offers the promise to do so however we must better understand how forest, which accounts for a large fraction of snow-covered land, affects the microwave retrieval of snow water equivalent (SWE). This is a fundamental goal of the NASA SnowEx mission and one we address using data collected during the February 2017 campaign in Grand Mesa, Colorado. We deployed UWScat, a ground-based, polarimetric scatterometer operating at 9.6 and 17.2 GHz frequencies, at 8 sites on Grand Mesa, including 2 sites observed from a platform approximately 9 m above the ground overlooking a coniferous canopy. Ancillary snowpit and snow microstructure measurements were also made and include traditional snowpit measurements along with measurements of snow specific surface area (SSA) using IRIS and IceCube systems. A snow micropenetrometer (SMP) was used to provide stratigraphic information. First, we show the influence of forest canopy on the microwave backscatter response, and how backscatter alone is insufficient to distinguish between forested and non-forested landscapes. Secondly, we show how polarimetric data can be used to identify the presence of forest canopy within the scene by revealing the depolarization that occurs in the interaction between the microwaves and the canopy structure. This result illustrates the benefits of a dual frequency polarimetric approach. While depolarization from a canopy is evident at X-band, there is less evidence of depolarization from a snowpack. At Ku-band frequencies, however, depolarization is evident both from interaction with the snowpack and the canopy. Finally we explore the relationship between SWE and backscatter in forested and un-forested environments. Together these results provide useful insights that increase our understanding of the radar polarimetric response from SWE in a forested landscape using a dual frequency Ku and X-band active microwave system.

Biodiversity Meets the Atmosphere: A Global View of Forest Canopies

Treesearch

C. M. P. Ozanne; D. Anhuf; S. L. Boulter; M. Keller; R. L. Kitching; C. Korner; F. C. Meinzer; A. W. Mitchell; T. Nakashizuka; P. L. Silva Dias; N. E. Stork; S. J. Wright; M Yoshimura

2003-01-01

The forest canopy is the functional interface between 90% of Earth’s terrestrial biomass and the atmosphere. Multidisciplinary research in the canopy has expanded concepts of global species richness, physiological processes, and the provision of ecosystem services. Trees respond in a species-specific manner to elevated carbon dioxide levels, while climate change...

Use of the forest canopy by bats.

Treesearch

L. Wunder; A.B. Carey

1994-01-01

Of the 15 species of bats in the Pacific Northwest, 11 are known to make regular use of the forest canopy for roosting, foraging, and reproduction. This paper reviews roosting requirements, foraging, and the importance of landscape-scale factors to canopy using species in the Northwest. Many northwest bats use several different types of tree roosts. Common roosting...

Plant responses to simulated hurricane impacts in a subtropical wet forest, Puerto Rico

Treesearch

Aaron B. Shiels; Jess K. Zimmerman; Diana C. García-Montiel; Inge Jonckheere; Jennifer Holm; David Horton; Nicholas Brokaw

2010-01-01

1. We simulated two key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on woody plant recruitment and forest structure. 2. We increased canopy openness by trimming branches and added or subtracted canopy detritus in a factorial design. Plant responses were...

A comparison of mangrove canopy height using multiple independent measurements from land, air, and space

Treesearch

David Lagomasino; Temilola Fatoyinbo; SeungKuk Lee; Emanuelle Feliciano; Carl Trettin; Marc Simard

2016-01-01

Canopy height is one of the strongest predictors of biomass and carbon in forested ecosystems. Additionally, mangrove ecosystems represent one of the most concentrated carbon reservoirs that are rapidly degrading as a result of deforestation, development, and hydrologic manipulation. Therefore, the accuracy of Canopy Height Models (CHM) over mangrove forest...

Drought-induced changes in Amazon forest structure from repeat airborne lidar

NASA Astrophysics Data System (ADS)

Morton, D. C.; Leitold, V.; Longo, M.; Keller, M.; dos-Santos, M. N.; Scaranello, M. A., Sr.

2017-12-01

Drought events in tropical forests, including the 2015-2016 El Niño, may reduce net primary productivity and increase canopy tree mortality, thereby altering the short and long-term net carbon balance of tropical forests. Given the broad extent of drought impacts, forest inventory plots or eddy flux towers may not capture regional variability in forest response to drought. Here, we analyzed repeat airborne lidar data to evaluate canopy turnover from branch and tree fall before (2013-2014) and during (2014-2016) the recent El Niño drought in the eastern and central Brazilian Amazon. Coincident field surveys for a 16-ha subset of the lidar coverage provided complementary information to classify turnover areas by mechanism (branch, multiple branch, tree fall, multiple tree fall) and estimate the total coarse woody debris volume from canopy and understory tree mortality. Annualized rates of canopy turnover increased by 50%, on average, during the drought period in both intact and fragmented forests near Santarém, Pará. Turnover increased uniformly across all size classes, and there was limited evidence that taller trees contributed a greater proportion of turnover events in any size class in 2014-2016 compared to 2013-2014. This short-term increase in canopy turnover differs from findings in multi-year rainfall exclusion experiments that large trees were more sensitive to drought impacts. Field measurements confirmed the separability of the smallest (single branch) and largest damage classes (multiple tree falls), but single tree and multiple branch fall events generated similar coarse woody debris production and lidar-derived changes in canopy volume. Large-scale sampling possible with repeat airborne lidar data also captured strong local and regional gradients in canopy turnover. Differences in slope partially explained the north-south gradient in canopy turnover dynamics near Santarém, with larger increases in turnover on flatter terrain. Regional variability in canopy turnover in response to drought conditions highlights the need for a mechanistic representation of branch and tree fall dynamics in ecosystem models to resolve changes in net carbon balance from the increase in coarse woody debris production and reorganization of canopy light environments during drought years.

Large-scale wind disturbances promote tree diversity in a Central Amazon forest.

PubMed

Marra, Daniel Magnabosco; Chambers, Jeffrey Q; Higuchi, Niro; Trumbore, Susan E; Ribeiro, Gabriel H P M; Dos Santos, Joaquim; Negrón-Juárez, Robinson I; Reu, Björn; Wirth, Christian

2014-01-01

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m(2)) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583 ± 46 trees ha(-1)) (mean ± 99% Confidence Interval) and basal area (26.7 ± 2.4 m(2) ha(-1)). Highly impacted areas had tree density and basal area as low as 120 trees ha(-1) and 14.9 m(2) ha(-1), respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m(2)) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

PubMed Central

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro; Trumbore, Susan E.; Ribeiro, Gabriel H. P. M.; dos Santos, Joaquim; Negrón-Juárez, Robinson I.; Reu, Björn; Wirth, Christian

2014-01-01

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 to 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha−1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m2 ha−1). Highly impacted areas had tree density and basal area as low as 120 trees ha−1 and 14.9 m2 ha−1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level. PMID:25099118

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

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

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m 2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 tomore » 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha -1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m 2 ha -1). Highly impacted areas had tree density and basal area as low as 120 trees ha -1 and 14.9 m 2 ha -1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m 2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.« less

Large-Scale Wind Disturbances Promote Tree Diversity in a Central Amazon Forest

DOE PAGES

Marra, Daniel Magnabosco; Chambers, Jeffrey Q.; Higuchi, Niro; ...

2014-08-06

Canopy gaps created by wind-throw events, or blowdowns, create a complex mosaic of forest patches varying in disturbance intensity and recovery in the Central Amazon. Using field and remote sensing data, we investigated the short-term (four-year) effects of large (>2000 m 2) blowdown gaps created during a single storm event in January 2005 near Manaus, Brazil, to study (i) how forest structure and composition vary with disturbance gradients and (ii) whether tree diversity is promoted by niche differentiation related to wind-throw events at the landscape scale. In the forest area affected by the blowdown, tree mortality ranged from 0 tomore » 70%, and was highest on plateaus and slopes. Less impacted areas in the region affected by the blowdown had overlapping characteristics with a nearby unaffected forest in tree density (583±46 trees ha -1) (mean±99% Confidence Interval) and basal area (26.7±2.4 m 2 ha -1). Highly impacted areas had tree density and basal area as low as 120 trees ha -1 and 14.9 m 2 ha -1, respectively. In general, these structural measures correlated negatively with an index of tree mortality intensity derived from satellite imagery. Four years after the blowdown event, differences in size-distribution, fraction of resprouters, floristic composition and species diversity still correlated with disturbance measures such as tree mortality and gap size. Our results suggest that the gradients of wind disturbance intensity encompassed in large blowdown gaps (>2000 m 2) promote tree diversity. Specialists for particular disturbance intensities existed along the entire gradient. The existence of species or genera taking an intermediate position between undisturbed and gap specialists led to a peak of rarefied richness and diversity at intermediate disturbance levels. A diverse set of species differing widely in requirements and recruitment strategies forms the initial post-disturbance cohort, thus lending a high resilience towards wind disturbances at the community level.« less

Restoration of temperate savannas and woodlands

Treesearch

Brice B. Hanberry; John M. Kabrick; Peter W. Dunwiddie; Tibor Hartel; Theresa B. Jain; Benjamin O. Knapp

2017-01-01

Savannas and woodlands are open forest phases that occur along a gradient between grasslands and closed canopy forests. These ecosystems are characterized by open to nearly closed canopies of overstorey trees, relatively sparse midstorey and understorey woody vegetation, and dense, species-rich ground flora. In contrast to closed forests, the dominant and codominant...

EVALUATION OF FOREST CANOPY MODELS FOR ESTIMATING ISOPRENE EMISSIONS

EPA Science Inventory

During the summer of 1992, isoprene emissions were measured in a mixed deciduous forest near Oak Ridge, Tennessee. Measurements were aimed at the experimental scale-up of emissions from the leaf level to the forest canopy to the mixed layer. Results from the scale-up study are co...

LINKING IN SITU TIME SERIES FOREST CANOPY LAI AND PHENOLOGY METRICS WITH MODIS AND LANDSAT NDVI AND LAI PRODUCTS

EPA Science Inventory

The subject of this presentation is forest vegetation dynamics as observed by the TERRA spacecraft's Moderate-Resolution Imaging Spectroradiometer (MODIS) and Landsat Thematic Mapper, and complimentary in situ time series measurements of forest canopy metrics related to Leaf Area...

Canopy microclimate response to pattern and density of thinning in a Sierra Nevada forest

Treesearch

T. Rambo; M. North

2009-01-01

Restoring Sierra Nevada mixed-conifer forests after a century of fire suppression has become an important management priority as fuel reduction thinning has been mandated by the Healthy Forests Restoration Act. However, in mechanically thinned stands there is little information on the effects of different patterns and densities of live-tree retention on forest canopy...

Breeding season concerns and response to forest management: Can forest management produce more breeding birds? Ornitologia Neotropical

Treesearch

J.L. Larkin; P.B. Wood; T.J. Boves; J. Sheehan; D.A. Buehler

2012-01-01

Cerulean Warblers (Setophaga cerulea), one of the fastest declining avian species in North America, are associated with heterogeneous canopies in mature hardwood forests. However, the age of most second and third-growth forests in eastern North American is not sufficient for natural tree mortality to maintain structurally diverse canopies. Previous research suggests...

Spread of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients

Treesearch

Cynthia D. Huebner

2010-01-01

Spread of Microstegium vimineum, an invasive exotic grass, in closed-canopy forests of West Virginia, U.S. was evaluated across a local (roadside to forest interior) and regional (across two geographic provinces) environmental gradient. Seed dispersal distances from roadside populations into forest interiors based on seed rain and soil seed bank data...

Origin of the Hawaiian rainforest and its transition states in long-term primary succession

NASA Astrophysics Data System (ADS)

Mueller-Dombois, D.; Boehmer, H. J.

2013-07-01

This paper addresses the question of transition states in the Hawaiian rainforest ecosystem with emphasis on their initial developments. Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering plants that over the millennia evolved into ca. 1000 endemic species. Outstanding among the forest builders were the tree ferns (Cibotium spp.) and the 'ōhi'a lehua trees (Metrosideros spp.), which still dominate the Hawaiian rainforest ecosystem today. The structure of this forest is simple. The canopy in closed mature rainforests is dominated by cohorts of Metrosideros polymorpha and the undergrowth by tree fern species of Cibotium. When a new lava flow cuts through this forest, kipuka are formed, i.e., islands of remnant vegetation. On the new volcanic substrate, the assemblage of plant life forms is similar to the assemblage during the evolution of this system. In open juvenile forests, a mat-forming fern, the uluhe fern (Dicranopteris linearis), becomes established. It inhibits further regeneration of the dominant 'ōhi'a tree, thereby reinforcing the cohort structure of the canopy guild. In the later part of its life cycle, the canopy guild breaks down often in synchrony. The trigger is hypothesized to be a climatic perturbation. After the disturbance, the forest becomes reestablished in about 30-40 yr. As the volcanic surfaces age, they go from a mesotrophic to a eutrophic phase, reaching a biophilic nutrient climax by about 1-25 K yr. Thereafter, a regressive oligotrophic phase follows; the soils become exhausted of nutrients. The shield volcanoes break down. Marginally, forest habitats change into bogs and stream ecosystems. The broader 'ōhi'a rainforest redeveloping in the more dissected landscapes of the older islands loses stature, often forming large gaps that are invaded by the aluminum tolerant uluhe fern. The 'ōhi'a trees still thrive on soils rejuvenated from landslides and from Asian dust on the oldest (5 million years old) island Kaua'i but their stature and living biomass is greatly diminished.

The Influence of Anthropogenic Sources on Fluxes of Secondary Organic Aerosol Precursors From a Deciduous Forest in the Southeastern United States

NASA Astrophysics Data System (ADS)

Saylor, R. D.; Stein, A. F.

2012-12-01

The dynamic, bi-directional exchange of trace chemical species between forests and the atmosphere has important impacts on both the forest ecosystem and atmospheric composition, with potentially profound consequences on air quality, climate and global ecosystem functioning. Forests are a dominant source of biogenic volatile organic compound (BVOC) emissions into the earth's atmosphere and thus play an important role in the formation of secondary organic aerosol (SOA). To arrive at a better scientific understanding of the complex chemical and physical processes of forest-atmosphere exchange and provide a platform for robust analysis of field measurements of these processes, a process-level, multiphase model of the atmospheric chemistry and physics of forest canopies is being developed. This model, the Atmospheric Chemistry and Canopy Exchange Simulation System (ACCESS) is being used to investigate various aspects of forest-atmosphere exchange and chemistry including gas, aqueous and aerosol phases. ACCESS currently includes processes accounting for the emission of BVOCs from the canopy, turbulent vertical transport within and above the canopy and throughout the height of the planetary boundary layer, detailed chemical reactions, mixing with the background atmosphere and bi-directional exchange between the atmosphere and the canopy and the forest floor. The Walker Branch Watershed (WBW) is a dedicated ecosystem research area on the U. S. Department of Energy's Oak Ridge Reservation in eastern Tennessee. The 97.5 ha watershed has been the site of long-term ecosystem and atmospheric research activities since the mid-1960's. A flux tower located within the watershed (35°57'30"N, 84°17'15"W; 365 m above mean sea level) and 10 km southwest of Oak Ridge, Tennessee, has served as a focal point for previous atmospheric turbulence and chemical flux measurements and the canopy morphology of the forest surrounding the flux tower has been extensively documented. The forest is broadleaf deciduous consisting of chestnut oak (Quercus prinus), tulip poplar (Liriodendron tulipifera), white oak (Quercus alba), red oak (Quercus rubra), red maple (Acer rubrum), and various hickory species (Carya sp.) in order of decreasing biomass density. At the time of isoprene flux measurements made at the tower in 1999, the stand was approximately 50 years old, the overstory canopy height was 24 m, and the whole canopy leaf area index was 4.9 m2 leaf/m2 ground area. In this presentation, the model formulation is described and results from the application of ACCESS to the WBW forest are presented and compared to measurements made at the site to investigate the influence of background anthropogenic sources on above canopy fluxes of SOA precursors in an isoprene emission dominated landscape in the unique atmospheric chemical environment of the southeastern United States. In particular, levels of background NOx concentrations are found to significantly influence both the magnitude and chemical composition of fluxes of SOA precursors from the canopy.

The phenology of leaf quality and its within-canopy variation is essential for accurate modeling of photosynthesis in tropical evergreen forests

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

Wu, Jin; Serbin, Shawn P.; Xu, Xiangtao

Leaf quantity (i.e., canopy leaf area index, LAI), quality (i.e., per-area photosynthetic capacity), and longevity all influence the photosynthetic seasonality of tropical evergreen forests. However, these components of tropical leaf phenology are poorly represented in most terrestrial biosphere models (TBMs). Here in this paper, we explored alternative options for the representation of leaf phenology effects in TBMs that employ the Farquahar, von Caemmerer & Berry (FvCB) representation of CO 2 assimilation. We developed a two-fraction leaf (sun and shade), two-layer canopy (upper and lower) photosynthesis model to evaluate different modeling approaches and assessed three components of phenological variations (i.e., leafmore » quantity, quality, and within-canopy variation in leaf longevity). Our model was driven by the prescribed seasonality of leaf quantity and quality derived from ground-based measurements within an Amazonian evergreen forest. Modeled photosynthetic seasonality was not sensitive to leaf quantity, but was highly sensitive to leaf quality and its vertical distribution within the canopy, with markedly more sensitivity to upper canopy leaf quality. This is because light absorption in tropical canopies is near maximal for the entire year, implying that seasonal changes in LAI have little impact on total canopy light absorption; and because leaf quality has a greater effect on photosynthesis of sunlit leaves than light limited, shade leaves and sunlit foliage are more abundant in the upper canopy. Our two-fraction leaf, two-layer canopy model, which accounted for all three phenological components, was able to simulate photosynthetic seasonality, explaining ~90% of the average seasonal variation in eddy covariance-derived CO 2 assimilation. This work identifies a parsimonious approach for representing tropical evergreen forest photosynthetic seasonality in TBMs that utilize the FvCB model of CO 2 assimilation and highlights the importance of incorporating more realistic phenological mechanisms in models that seek to improve the projection of future carbon dynamics in tropical evergreen forests.« less

The phenology of leaf quality and its within-canopy variation is essential for accurate modeling of photosynthesis in tropical evergreen forests

DOE PAGES

Wu, Jin; Serbin, Shawn P.; Xu, Xiangtao; ...

2017-04-18

Leaf quantity (i.e., canopy leaf area index, LAI), quality (i.e., per-area photosynthetic capacity), and longevity all influence the photosynthetic seasonality of tropical evergreen forests. However, these components of tropical leaf phenology are poorly represented in most terrestrial biosphere models (TBMs). Here in this paper, we explored alternative options for the representation of leaf phenology effects in TBMs that employ the Farquahar, von Caemmerer & Berry (FvCB) representation of CO 2 assimilation. We developed a two-fraction leaf (sun and shade), two-layer canopy (upper and lower) photosynthesis model to evaluate different modeling approaches and assessed three components of phenological variations (i.e., leafmore » quantity, quality, and within-canopy variation in leaf longevity). Our model was driven by the prescribed seasonality of leaf quantity and quality derived from ground-based measurements within an Amazonian evergreen forest. Modeled photosynthetic seasonality was not sensitive to leaf quantity, but was highly sensitive to leaf quality and its vertical distribution within the canopy, with markedly more sensitivity to upper canopy leaf quality. This is because light absorption in tropical canopies is near maximal for the entire year, implying that seasonal changes in LAI have little impact on total canopy light absorption; and because leaf quality has a greater effect on photosynthesis of sunlit leaves than light limited, shade leaves and sunlit foliage are more abundant in the upper canopy. Our two-fraction leaf, two-layer canopy model, which accounted for all three phenological components, was able to simulate photosynthetic seasonality, explaining ~90% of the average seasonal variation in eddy covariance-derived CO 2 assimilation. This work identifies a parsimonious approach for representing tropical evergreen forest photosynthetic seasonality in TBMs that utilize the FvCB model of CO 2 assimilation and highlights the importance of incorporating more realistic phenological mechanisms in models that seek to improve the projection of future carbon dynamics in tropical evergreen forests.« less

An energy balance model for forest canopies: a case study

Treesearch

S. M. Goltz; James A. Smith

1996-01-01

The use of thermal scanning devices to map underlying terrain surface temperatures has been recognized as a potential tool for estimating evapotranspiration and latent heat flux densities in forest canopies.

Monitoring Forest Degradation for a Case Study in Cambodia: Comparison of Landsat 8 and Sentinel-2 Imagery

NASA Astrophysics Data System (ADS)

Langner, Andreas; Miettinen, Jukka; Stibig, Hans-Jurgen

2016-08-01

We use a Normalized Burned Ratio (NBR) differential approach for detecting forest canopy disturbance caused by selective logging in evergreen tropical moist forests of central Cambodia. The general disturbance pattern obtained from Landsat 8 (30 m) imagery is largely compatible to Sentinel-2 (10 m), showing good conformity to high resolution RapidEye reference data. However, the 10 m spatial resolution of Sentinel-2 provides notably higher spatial detail and purer pixel values, increasing the potential for detecting fine and subtle forest canopy changes as indicators for potential forest degradation. We can expect further improvement for detecting short-lived disturbance signals in tropical forest canopies due to an increased revisit frequency (5 days) after the Sentinel-2B launch.

Observation of organized structure in turbulent flow within and above a forest canopy

NASA Technical Reports Server (NTRS)

Gao, W.; Shaw, R. H.; Paw u, K. T.

1989-01-01

Data obtained with seven triaxial sonic anemometer/thermometers and three Lyman-alpha hygrometers at an experimental site in Ontario, Canada reveal the coherent occurrence of ramp patterns of temperature and humidity at several levels within and above the deciduous forest considered. The ramps appear most clearly in the middle and upper portion of the forest, and near the top of the forest they are composed of a weak ejecting motion transporting warm and/or moist air out of the forest, followed by strong sweeps of cool and/or dry air penetrating into the canopy. In the middle and upper parts of the canopy, the sweeps are found to conduct a large proportion of the overall transfer between the forest and the lower atmosphere, with a lesser contribution from ejections.

Landscape biogeochemistry reflected in shifting distributions of chemical traits in the Amazon forest canopy

NASA Astrophysics Data System (ADS)

Asner, Gregory P.; Anderson, Christopher B.; Martin, Roberta E.; Tupayachi, Raul; Knapp, David E.; Sinca, Felipe

2015-07-01

Tropical forest functional diversity, which is a measure of the diversity of organismal interactions with the environment, is poorly understood despite its importance for linking evolutionary biology to ecosystem biogeochemistry. Functional diversity is reflected in functional traits such as the concentrations of different compounds in leaves or the density of leaf mass, which are related to plant activities such as plant defence, nutrient cycling, or growth. In the Amazonian lowlands, river movement and microtopography control nutrient mobility, which may influence functional trait distributions. Here we use airborne laser-guided imaging spectroscopy to develop maps of 16 forest canopy traits, throughout four large landscapes that harbour three common forest community types on the Madre de Dios and Tambopata rivers in southwestern Amazonia. Our maps, which are based on quantitative chemometric analysis of forest canopies with visible-to-near infrared (400-2,500 nm) spectroscopy, reveal substantial variation in canopy traits and their distributions within and among forested landscapes. Forest canopy trait distributions are arranged in a nested pattern, with location along rivers controlling trait variation between different landscapes, and microtopography controlling trait variation within landscapes. We suggest that processes of nutrient deposition and depletion drive increasing phosphorus limitation, and a corresponding increase in plant defence, in an eastward direction from the base of the Andes into the Amazon Basin.

On the accurate estimation of gap fraction during daytime with digital cover photography

NASA Astrophysics Data System (ADS)

Hwang, Y. R.; Ryu, Y.; Kimm, H.; Macfarlane, C.; Lang, M.; Sonnentag, O.

2015-12-01

Digital cover photography (DCP) has emerged as an indirect method to obtain gap fraction accurately. Thus far, however, the intervention of subjectivity, such as determining the camera relative exposure value (REV) and threshold in the histogram, hindered computing accurate gap fraction. Here we propose a novel method that enables us to measure gap fraction accurately during daytime under various sky conditions by DCP. The novel method computes gap fraction using a single DCP unsaturated raw image which is corrected for scattering effects by canopies and a reconstructed sky image from the raw format image. To test the sensitivity of the novel method derived gap fraction to diverse REVs, solar zenith angles and canopy structures, we took photos in one hour interval between sunrise to midday under dense and sparse canopies with REV 0 to -5. The novel method showed little variation of gap fraction across different REVs in both dense and spares canopies across diverse range of solar zenith angles. The perforated panel experiment, which was used to test the accuracy of the estimated gap fraction, confirmed that the novel method resulted in the accurate and consistent gap fractions across different hole sizes, gap fractions and solar zenith angles. These findings highlight that the novel method opens new opportunities to estimate gap fraction accurately during daytime from sparse to dense canopies, which will be useful in monitoring LAI precisely and validating satellite remote sensing LAI products efficiently.

Removal of nutrient limitations in forest gaps enhances growth rate and resistance to cavitation in subtropical canopy tree species differing in shade tolerance.

PubMed

Villagra, Mariana; Campanello, Paula I; Montti, Lia; Goldstein, Guillermo

2013-03-01

A 4-year fertilization experiment with nitrogen (N) and phosphorus (P) was carried out in natural gaps of a subtropical forest in northeastern Argentina. Saplings of six dominant canopy species differing in shade tolerance were grown in five control and five N + P fertilized gaps. Hydraulic architectural traits such as wood density, the leaf area to sapwood area ratio (LA : SA), vulnerability to cavitation (P50) and specific and leaf-specific hydraulic conductivity were measured, as well as the relative growth rate, specific leaf area (SLA) and percentage of leaf damage by insect herbivores. Plant growth rates and resistance to drought-induced embolisms increased when nutrient limitations were removed. On average, the P50 of control plants was -1.1 MPa, while the P50 of fertilized plants was -1.6 MPa. Wood density and LA : SA decreased with N + P additions. A trade-off between vulnerability to cavitation and efficiency of water transport was not observed. The relative growth rate was positively related to the total leaf surface area per plant and negatively related to LA : SA, while P50 was positively related to SLA across species and treatments. Plants with higher growth rates and higher total leaf area in fertilized plots were able to avoid hydraulic dysfunction by becoming less vulnerable to cavitation (more negative P50). Two high-light-requiring species exhibited relatively low growth rates due to heavy herbivore damage. Contrary to expectations, shade-tolerant plants with relatively high resistance to hydraulic dysfunction and reduced herbivory damage were able to grow faster. These results suggest that during the initial phase of sapling establishment in gaps, species that were less vulnerable to cavitation and exhibited reduced herbivory damage had faster realized growth rates than less shade-tolerant species with higher potential growth rates. Finally, functional relationships between hydraulic traits and growth rate across species and treatments were maintained regardless of soil nutrient status.

A polar grid estimator of forest canopy structure metrics using airborne laser scanning data

Treesearch

Nicholas R. Vaughn; Greg P. Asner; Christian P. Giardina

2013-01-01

The structure of a forest canopy is the key determinant of light transmission, use and understory availability. Airborne light detection and ranging (LiDAR) has been used successfully to measure multiple canopy structural properties, thereby greatly reducing the fieldwork required to map spatial variation in structure. However, lidar metrics to date do not reflect the...

Seedling response to initial oak woodland restoration treatments on the Ozark National Forest

Treesearch

Jamie L. Schuler; Don C. Bragg; Eric Heitzman; Jason Milks

2013-01-01

Over the last century, the range of oak woodland ecosystems has diminished as woodlands have become more closed-canopy forests. A century of fire suppression efforts has all but eliminated the frequent ground fires necessary to maintain the open canopy characteristics of oak woodland ecosystems. Restoration efforts are underway to return some of the closed-canopy...

Analyzing canopy structure in Pacific Northwest old-growth forests with a stand-scale crown model

Treesearch

Robert Van Pelt; Malcolm P. North

1996-01-01

I n forests, the canopy is the locale of critical ecosystem processes such as photosynthesis and evapotranspiration. and it provides essential habitat for a highly diverse array of animals, plants, and other organisms. Despite its importance, the structure of the canopy as a whole has had little quantitative study because limited access makes quantification difficult...

Natural canopy bridges effectively mitigate tropical forest fragmentation for arboreal mammals.

PubMed

Gregory, Tremaine; Carrasco-Rueda, Farah; Alonso, Alfonso; Kolowski, Joseph; Deichmann, Jessica L

2017-06-20

Linear infrastructure development and resulting habitat fragmentation are expanding in Neotropical forests, and arboreal mammals may be disproportionately impacted by these linear habitat clearings. Maintaining canopy connectivity through preservation of connecting branches (i.e. natural canopy bridges) may help mitigate that impact. Using camera traps, we evaluated crossing rates of a pipeline right-of-way in a control area with no bridges and in a test area where 13 bridges were left by the pipeline construction company. Monitoring all canopy crossing points for a year (7,102 canopy camera nights), we confirmed bridge use by 25 mammal species from 12 families. With bridge use beginning immediately after exposure and increasing over time, use rates were over two orders of magnitude higher than on the ground. We also found a positive relationship between a bridge's use rate and the number of species that used it, suggesting well-used bridges benefit multiple species. Data suggest bridge use may be related to a combination of bridge branch connectivity, multiple connections, connectivity to adjacent forest, and foliage cover. Given the high use rate and minimal cost, we recommend all linear infrastructure projects in forests with arboreal mammal populations include canopy bridges.

Web-FACE: a new canopy free-air CO2 enrichment system for tall trees in mature forests.

PubMed

Pepin, Steeve; Körner, Christian

2002-09-01

The long-term responses of forests to atmospheric CO2 enrichment have been difficult to determine experimentally given the large scale and complex structure of their canopy. We have developed a CO2 exposure system that uses the free-air CO2 enrichment (FACE) approach but was designed for tall canopy trees. The system consists of a CO2-release system installed within the crown of adult trees using a 45-m tower crane, a CO2 monitoring system and an automated regulation system. Pure CO2 gas is released from a network of small tubes woven into the forest canopy (web-FACE), and CO2 is emitted from small laser-punched holes. The set point CO2 concentration ([CO2]) of 500 µmol mol(-1) is controlled by a pulse-width modulation routine that adjusts the rate of CO2 injection as a function of measured [CO2] in the canopy. CO2 consumption for the enrichment of 14 tall canopy trees was about 2 tons per day over the whole growing season. The seasonal daytime mean CO2 concentration was 520 µmol mol(-1). One-minute averages of CO2 measurements conducted at canopy height in the center of the CO2-enriched zone were within ±20% and ±10% of the target concentration for 76% and 47% of the exposure time, respectively. Despite the size of the canopy and the windy site conditions, performance values correspond to about 75% of that reported for conventional forest FACE with the added advantage of a much simpler and less intrusive infrastructure. Stable carbon isotope signals captured by 80 Bermuda grass (Cynodon dactylon) seedlings distributed within the canopy of treated and control tree districts showed a clearly delineated area, with some nearby individuals having been exposed to a gradient of [CO2], which is seen as added value. Time-integrated values of [CO2] derived from the C isotope composition of C. dactylon leaves indicated a mean (±SD) concentration of 513±63 µmol mol(-1) in the web-FACE canopy area. In view of the size of the forest and the rough natural canopy, web-FACE is a most promising avenue towards natural forest experiments, which are greatly needed.

Comparison of infrared canopy temperature in a rubber plantation and tropical rain forest

NASA Astrophysics Data System (ADS)

Song, Qing-Hai; Deng, Yun; Zhang, Yi-Ping; Deng, Xiao-Bao; Lin, You-Xing; Zhou, Li-Guo; Fei, Xue-Hai; Sha, Li-Qing; Liu, Yun-Tong; Zhou, Wen-Jun; Gao, Jin-Bo

2017-10-01

Canopy temperature is a result of the canopy energy balance and is driven by climate conditions, plant architecture, and plant-controlled transpiration. Here, we evaluated canopy temperature in a rubber plantation (RP) and tropical rainforest (TR) in Xishuangbanna, southwestern China. An infrared temperature sensor was installed at each site to measure canopy temperature. In the dry season, the maximum differences (Tc - Ta) between canopy temperature (Tc) and air temperature (Ta) in the RP and TR were 2.6 and 0.1 K, respectively. In the rainy season, the maximum (Tc - Ta) values in the RP and TR were 1.0 and -1.1 K, respectively. There were consistent differences between the two forests, with the RP having higher (Tc - Ta) than the TR throughout the entire year. Infrared measurements of Tc can be used to calculate canopy stomatal conductance in both forests. The difference in (Tc - Ta) at three gc levels with increasing direct radiation in the RP was larger than in the TR, indicating that change in (Tc - Ta) in the RP was relatively sensitive to the degree of stomatal closure.

Analysis of laser altimeter waveforms for forested ecosystems of Central Florida

NASA Astrophysics Data System (ADS)

Weishampel, John F.; Harding, David J.; Boutet, Jeffry C., Jr.; Drake, Jason B.

1997-07-01

An experimental profiling airborne laser altimeter system developed at NASA's Goddard Space Flight Center was used to acquire vertical canopy data from several ecosystem types from The Nature Conservancy's Disney Wilderness Preserve, near Kissimmee, Florida. This laser altimeter, besides providing submeter accuracy of tree height, captures a profile of data which relates to the magnitude of reflectivity of the laser pulse as it penetrates different elevations of the forest canopy. This complete time varying amplitude of the return signal of the laser pulse, between the first (i.e., the canopy top) and last (i.e., the ground) returns, yields a waveform which is related to canopy architecture, specifically the nadir-projected vertical distribution of the surface of canopy components (i.e., foliage, twigs, and branches). Selected profile returns from representative covertypes (e.g., pine flatwoods, bayhead, and cypress wetland) were compared with ground truthed forest composition (i.e., species and size class distribution) and structural (i.e., canopy height, canopy closure, crown depth) measures to help understand how these properties contribute to variation in the altimeter waveform.

Aspects of Boreal Forest Hydrology: From Stand to Watershed

NASA Technical Reports Server (NTRS)

Nijssen, B.

2000-01-01

This report evaluates land surface hydrologic processes in the boreal forest using observations collected during the Boreal Ecosystem Atmospheric Study (BOREAS), carried out in the boreal forest of central Canada from 1994 to 1996. Three separate studies, each of which constitutes a journal publication, are included. The first study describes the application of a spatially-distributed hydrologic model, originally developed for mid-latitude forested environments, to selected BOREAS flux measurement sites. Compared to point observations at the flux towers, the model represented energy and moisture fluxes reasonably well, but shortcomings were identified in the soil thermal submodel and the partitioning of evapotranspiration into canopy and subcanopy components. As a first step towards improving this partitioning, the second study develops a new parameterization for transmission of shortwave radiation through boreal forest canopies. The new model accounts for the transmission of diffuse and direct shortwave radiation and accounts for multiple scattering in the canopy and multiple reflections between the canopy layers.

Manipulation of density of Pseudotsuga menziesii canopies: preliminary effects on understory vegetation.

Treesearch

D.R. Thysell; A.B. Carey

2001-01-01

Managing second-growth forests to conserve biodiversity has been proposed by both foresters and conservation biologists. Management, however, can have unintended consequences, including reduction in native species diversity and increased invasion by exotic species. Our goal was to determine if inducing heterogeneity in managed forest canopies could promote a diversity...

Restoration of temperate savannas and woodlands [Chapter 11

Treesearch

Brice B. Hanberry; John M. Kabrick; Peter W. Dunwiddie; Tibor Hartel; Theresa B. Jain; Benjamin O. Knapp

2017-01-01

Savannas and woodlands are open forest phases that occur along a gradient between grasslands and closed canopy forests. These ecosystems are characterized by open to nearly closed canopies of overstorey trees, relatively sparse midstorey and understorey woody vegetation, and dense, species-rich ground flora. In contrast to closed forests, the dominant and codominant...

Models for estimation and simulation of crown and canopy cover

Treesearch

John D. Shaw

2005-01-01

Crown width measurements collected during Forest Inventory and Analysis and Forest Health Monitoring surveys are being used to develop individual tree crown width models and plot-level canopy cover models for species and forest types in the Intermountain West. Several model applications are considered in the development process, including remote sensing of plot...

Accuracy of an IFSAR-derived digital terrain model under a conifer forest canopy.

Treesearch

Hans-Erik Andersen; Stephen E. Reutebuch; Robert J. McGaughey

2005-01-01

Accurate digital terrain models (DTMs) are necessary for a variety of forest resource management applications, including watershed management, timber harvest planning, and fire management. Traditional methods for acquiring topographic data typically rely on aerial photogrammetry, where measurement of the terrain surface below forest canopy is difficult and error prone...

Radon 222 tracing of soil and forest canopy trace gas exchange in an open canopy boreal forest

NASA Technical Reports Server (NTRS)

Ussler, William, III; Chanton, Jeffrey P.; Kelley, Cheryl A.; Martens, Christopher S.

1994-01-01

A set of continuous, high-resolution atmospheric radon (Rn-222) concentration time series and radon soil flux measurements were acquired during the summer of 1990 at a micrometeorological tower site 13 km northwest of Schefferville, Quebec, Canada. The tower was located in a dry upland, open-canopy lichen-spruce woodland. For the period July 23 to August 1, 1990, the mean radon soil flux was 41.1 +/- 4.8 Bq m(exp -2)/h. Radon surface flux from the two end-member forest floor cover types (lichen mat and bare soil) were 38.8 +/- 5.1 and 61.8 +/- 15.6 Bq m(exp -2)/h, respectively. Average total forest canopy resistances computed using a simple 'flux box' model for radon exchange between the forest canopy and the overlying atmosphere range from 0.47 +/- 0.24 s cm(exp -1) to 2.65 +/- 1.61 cm(exp -1) for daytime hours (0900-1700 LT) and from 3.44 +/- 0.91 s cm(exp -1) to 10.55 +/- 7.16 s cm(exp -1) for nighttime hours (2000-0600) for the period July 23 to August 6, 1990. Continuous radon profiling of canopy atmospheres is a suitable approach for determining rates of biosphere/atmosphere trace gas exchange for remote field sites where daily equipment maintenance is not possible. where daily equipment maintenance is not possible.

Remote sensing of forest canopy and leaf biochemical contents

NASA Technical Reports Server (NTRS)

Peterson, David L.; Matson, Pamela A.; Card, Don H.; Aber, John D.; Wessman, Carol; Swanberg, Nancy; Spanner, Michael

1988-01-01

Recent research on the remote sensing of forest leaf and canopy biochemical contents suggests that the shortwave IR region contains this information; laboratory analyses of dry ground leaves have yielded reliable predictive relationships between both leaf nitrogen and lignin with near-IR spectra. Attention is given to the application of these laboratory techniques to a limited set of spectra from fresh, whole leaves of conifer species. The analysis of Airborne Imaging Spectrometer data reveals that total water content variations in deciduous forest canopies appear as overall shifts in the brightness of raw spectra.

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

Danilo Dragoni; Hans Peter Schmid; C.S.B. Grimmond

During the project period we continued to conduct long-term (multi-year) measurements, analysis, and modeling of energy and mass exchange in and over a deciduous forest in the Midwestern United States, to enhance the understanding of soil-vegetation-atmosphere exchange of carbon. At the time when this report was prepared, results from nine years of measurements (1998 - 2006) of above canopy CO2 and energy fluxes at the AmeriFlux site in the Morgan-Monroe State Forest, Indiana, USA (see Table 1), were available on the Fluxnet database, and the hourly CO2 fluxes for 2007 are presented here (see Figure 1). The annual sequestration ofmore » atmospheric carbon by the forest is determined to be between 240 and 420 g C m-2 a-1 for the first ten years. These estimates are based on eddy covariance measurements above the forest, with a gap-filling scheme based on soil temperature and photosynthetically active radiation. Data gaps result from missing data or measurements that were rejected in qua)lity control (e.g., during calm nights). Complementary measurements of ecological variables (i.e. inventory method), provided an alternative method to quantify net carbon uptake by the forest, partition carbon allocation in each ecosystem components, and reduce uncertainty on annual net ecosystem productivity (NEP). Biometric datasets are available on the Fluxnext database since 1998 (with the exclusion of 2006). Analysis for year 2007 is under completion.« less

Patterns of Canopy and Surface Layer Consumption in a Boreal Forest Fire from Repeat Airborne Lidar

NASA Technical Reports Server (NTRS)

Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

2017-01-01

Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaskas Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broad leaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from above ground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity from Landsat.

Patterns of canopy and surface layer consumption in a boreal forest fire from repeat airborne lidar

NASA Astrophysics Data System (ADS)

Alonzo, Michael; Morton, Douglas C.; Cook, Bruce D.; Andersen, Hans-Erik; Babcock, Chad; Pattison, Robert

2017-05-01

Fire in the boreal region is the dominant agent of forest disturbance with direct impacts on ecosystem structure, carbon cycling, and global climate. Global and biome-scale impacts are mediated by burn severity, measured as loss of forest canopy and consumption of the soil organic layer. To date, knowledge of the spatial variability in burn severity has been limited by sparse field sampling and moderate resolution satellite data. Here, we used pre- and post-fire airborne lidar data to directly estimate changes in canopy vertical structure and surface elevation for a 2005 boreal forest fire on Alaska’s Kenai Peninsula. We found that both canopy and surface losses were strongly linked to pre-fire species composition and exhibited important fine-scale spatial variability at sub-30 m resolution. The fractional reduction in canopy volume ranged from 0.61 in lowland black spruce stands to 0.27 in mixed white spruce and broadleaf forest. Residual structure largely reflects standing dead trees, highlighting the influence of pre-fire forest structure on delayed carbon losses from aboveground biomass, post-fire albedo, and variability in understory light environments. Median loss of surface elevation was highest in lowland black spruce stands (0.18 m) but much lower in mixed stands (0.02 m), consistent with differences in pre-fire organic layer accumulation. Spatially continuous depth-of-burn estimates from repeat lidar measurements provide novel information to constrain carbon emissions from the surface organic layer and may inform related research on post-fire successional trajectories. Spectral measures of burn severity from Landsat were correlated with canopy (r = 0.76) and surface (r = -0.71) removal in black spruce stands but captured less of the spatial variability in fire effects for mixed stands (canopy r = 0.56, surface r = -0.26), underscoring the difficulty in capturing fire effects in heterogeneous boreal forest landscapes using proxy measures of burn severity from Landsat.

Oil road effects on the anuran community of a high canopy tank bromeliad (Aechmea zebrina) in the upper Amazon basin, Ecuador.

PubMed

McCracken, Shawn F; Forstner, Michael R J

2014-01-01

Tropical forest canopies are among the most species-rich terrestrial habitats on earth and one of the remaining relatively unexplored biotic frontiers. Epiphytic bromeliads provide microhabitat for a high diversity of organisms in tropical forest canopies and are considered a keystone resource. A number of amphibians inhabit these phytotelmata, yet their ecological role and status in forest canopies remains unknown. For this study, anurans were collected from an upper canopy tank bromeliad (Aechmea zebrina) at ∼20-45 m (x¯ = 33 m) above the forest floor. Bromeliads were sampled from trees located near trails in undisturbed primary rainforest and oil access roads in the Yasuní Biosphere Reserve of Amazonian Ecuador. We collected 95 anurans representing 10 species from 160 bromeliads in 32 trees. We used generalized linear mixed models to assess the effects of disturbance and habitat factors on the occupancy and abundance of anurans collected. Bromeliads in forest along oil roads had a lower occupancy and abundance of anurans than those in undisturbed forest, a somewhat unexpected result due to the intactness and quality of forest adjacent to the roads. Recorded habitat variables had no relationship with occupancy or abundance of anurans, and did not differ significantly between treatments. Our findings reveal that even the minimal footprint of natural resource extraction operations, primarily roads, in rainforest environments can have significant negative impacts on the unique upper canopy anuran community. Based on these results, we recommend that natural resource development treat rainforest habitat as an offshore system where roads are not used, employ industry best practice guidelines, and current access roads be protected from colonization and further deforestation.

Canopy volume removal from oil and gas development activity in the upper Susquehanna River basin in Pennsylvania and New York (USA): An assessment using lidar data

USGS Publications Warehouse

Young, John A.; Maloney, Kelly O.; Slonecker, Terry; Milheim, Lesley E.; Siripoonsup, David

2018-01-01

Oil and gas development is changing the landscape in many regions of the United States and globally. However, the nature, extent, and magnitude of landscape change and development, and precisely how this development compares to other ongoing land conversion (e.g. urban/sub-urban development, timber harvest) is not well understood. In this study, we examine land conversion from oil and gas infrastructure development in the upper Susquehanna River basin in Pennsylvania and New York, an area that has experienced much oil and gas development over the past 10 years. We quantified land conversion in terms of forest canopy geometric volume loss in contrast to previous studies that considered only areal impacts. For the first time in a study of this type, we use fine-scale lidar forest canopy geometric models to assess the volumetric change due to forest clearing from oil and gas development and contrast this land change to clear cut forest harvesting, and urban and suburban development. Results show that oil and gas infrastructure development removed a large volume of forest canopy from 2006 to 2013, and this removal spread over a large portion of the study area. Timber operations (clear cutting) on Pennsylvania State Forest lands removed a larger total volume of forest canopy during the same time period, but this canopy removal was concentrated in a smaller area. Results of our study point to the need to consider volumetric impacts of oil and gas development on ecosystems, and to place potential impacts in context with other ongoing land conversions.

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.

Oil Road Effects on the Anuran Community of a High Canopy Tank Bromeliad (Aechmea zebrina) in the Upper Amazon Basin, Ecuador

PubMed Central

McCracken, Shawn F.; Forstner, Michael R. J.

2014-01-01

Tropical forest canopies are among the most species-rich terrestrial habitats on earth and one of the remaining relatively unexplored biotic frontiers. Epiphytic bromeliads provide microhabitat for a high diversity of organisms in tropical forest canopies and are considered a keystone resource. A number of amphibians inhabit these phytotelmata, yet their ecological role and status in forest canopies remains unknown. For this study, anurans were collected from an upper canopy tank bromeliad (Aechmea zebrina) at ∼20–45 m (x¯ = 33 m) above the forest floor. Bromeliads were sampled from trees located near trails in undisturbed primary rainforest and oil access roads in the Yasuní Biosphere Reserve of Amazonian Ecuador. We collected 95 anurans representing 10 species from 160 bromeliads in 32 trees. We used generalized linear mixed models to assess the effects of disturbance and habitat factors on the occupancy and abundance of anurans collected. Bromeliads in forest along oil roads had a lower occupancy and abundance of anurans than those in undisturbed forest, a somewhat unexpected result due to the intactness and quality of forest adjacent to the roads. Recorded habitat variables had no relationship with occupancy or abundance of anurans, and did not differ significantly between treatments. Our findings reveal that even the minimal footprint of natural resource extraction operations, primarily roads, in rainforest environments can have significant negative impacts on the unique upper canopy anuran community. Based on these results, we recommend that natural resource development treat rainforest habitat as an offshore system where roads are not used, employ industry best practice guidelines, and current access roads be protected from colonization and further deforestation. PMID:24416414

Polarimetric signatures of a coniferous forest canopy based on vector radiative transfer theory

NASA Technical Reports Server (NTRS)

Karam, M. A.; Fung, A. K.; Amar, F.; Mougin, E.; Lopes, A.; Beaudoin, A.

1992-01-01

Complete polarization signatures of a coniferous forest canopy are studied by the iterative solution of the vector radiative transfer equations up to the second order. The forest canopy constituents (leaves, branches, stems, and trunk) are embedded in a multi-layered medium over a rough interface. The branches, stems and trunk scatterers are modeled as finite randomly oriented cylinders. The leaves are modeled as randomly oriented needles. For a plane wave exciting the canopy, the average Mueller matrix is formulated in terms of the iterative solution of the radiative transfer solution and used to determine the linearly polarized backscattering coefficients, the co-polarized and cross-polarized power returns, and the phase difference statistics. Numerical results are presented to investigate the effect of transmitting and receiving antenna configurations on the polarimetric signature of a pine forest. Comparison is made with measurements.

Effects of foliage clumping on the estimation of global terrestrial gross primary productivity

NASA Astrophysics Data System (ADS)

Chen, Jing M.; Mo, Gang; Pisek, Jan; Liu, Jane; Deng, Feng; Ishizawa, Misa; Chan, Douglas

2012-03-01

Sunlit and shaded leaf separation proposed by Norman (1982) is an effective way to upscale from leaf to canopy in modeling vegetation photosynthesis. The Boreal Ecosystem Productivity Simulator (BEPS) makes use of this methodology, and has been shown to be reliable in modeling the gross primary productivity (GPP) derived from CO2flux and tree ring measurements. In this study, we use BEPS to investigate the effect of canopy architecture on the global distribution of GPP. For this purpose, we use not only leaf area index (LAI) but also the first ever global map of the foliage clumping index derived from the multiangle satellite sensor POLDER at 6 km resolution. The clumping index, which characterizes the degree of the deviation of 3-dimensional leaf spatial distributions from the random case, is used to separate sunlit and shaded LAI values for a given LAI. Our model results show that global GPP in 2003 was 132 ± 22 Pg C. Relative to this baseline case, our results also show: (1) global GPP is overestimated by 12% when accurate LAI is available but clumping is ignored, and (2) global GPP is underestimated by 9% when the effective LAI is available and clumping is ignored. The clumping effects in both cases are statistically significant (p < 0.001). The effective LAI is often derived from remote sensing by inverting the measured canopy gap fraction to LAI without considering the clumping. Global GPP would therefore be generally underestimated when remotely sensed LAI (actually effective LAI by our definition) is used. This is due to the underestimation of the shaded LAI and therefore the contribution of shaded leaves to GPP. We found that shaded leaves contribute 50%, 38%, 37%, 39%, 26%, 29% and 21% to the total GPP for broadleaf evergreen forest, broadleaf deciduous forest, evergreen conifer forest, deciduous conifer forest, shrub, C4 vegetation, and other vegetation, respectively. The global average of this ratio is 35%.

Canopy structure and tree condition of young, mature, and old-growth Douglas-fir/hardwood forests

Treesearch

B.B. Bingham; J.O. Sawyer

1992-01-01

Sixty-two Douglas-fir/hardwood stands ranging from 40 to 560 years old were used to characterize the density; diameter, and height class distributions of canopy hardwoods and conifers in young (40 -100 yr), mature (101 - 200 yr) and old-growth (>200 yr) forests. The crown, bole, disease, disturbance, and cavity conditions of canopy conifers and hardwoods were...

Large area mapping of southwestern forest crown cover, canopy height, and biomass using the NASA Multiangle Imaging Spectro-Radiometer

Treesearch

Mark Chopping; Gretchen G. Moisen; Lihong Su; Andrea Laliberte; Albert Rango; John V. Martonchik; Debra P. C. Peters

2008-01-01

A rapid canopy reflectance model inversion experiment was performed using multi-angle reflectance data from the NASA Multi-angle Imaging Spectro-Radiometer (MISR) on the Earth Observing System Terra satellite, with the goal of obtaining measures of forest fractional crown cover, mean canopy height, and aboveground woody biomass for large parts of south-eastern Arizona...

Random forests and stochastic gradient boosting for predicting tree canopy cover: Comparing tuning processes and model performance

Treesearch

Elizabeth A. Freeman; Gretchen G. Moisen; John W. Coulston; Barry T. (Ty) Wilson

2015-01-01

As part of the development of the 2011 National Land Cover Database (NLCD) tree canopy cover layer, a pilot project was launched to test the use of high-resolution photography coupled with extensive ancillary data to map the distribution of tree canopy cover over four study regions in the conterminous US. Two stochastic modeling techniques, random forests (RF...

Wind shear, sensible heat flux and atmospheric stability within a forest canopy

NASA Astrophysics Data System (ADS)

Piringer, M.; Polreich, E.

2009-09-01

The scientific project "ROSALIA”, carried out in co-operation between ZAMG and the Austrian Federal Research and Training Centre for Forests, Natural Hazards, and Landscape, investigated the meteorological impacts on pollen emission and spread in a typical Central European forest of mixed deciduous and coniferous trees. The study area is the "Lehrforst Rosalia” of BOKU University approx. 60 km south of the city of Vienna in undulating terrain (300 - 750 m altitude). In this area, two meteorological towers of similar construction, one at crest height, the other in the small valley of the river "Ofenbach” near a meteorological ground station, have been equipped with 3D ultrasonic anemometers: one has been placed on top of the upper tower to representatively measure the gradient flow; the tower in the valley has been equipped with 3 instruments, one at the lowermost platform near ground, the second in the middle of the forest canopy, the third on top of the tower situated within the transition zone between the canopy and the "free” boundary layer where the gradient winds dominate. The sonic anemometers measure the three-dimensional wind vector; in addition, the sound velocity is derived, from which the so-called "sonic temperature” is calculated to derive the sensible heat flux. Other quantities are the means, standard deviations, and covariances of the wind components and the momentum flux, the Monin-Obukhov stability parameter, and the friction velocity. In the sloping dense forest canopy surrounding the tower, complex meteorological conditions and frequent decoupling of above-canopy and within-canopy flow has to be expected. The presence of a thick leaf canopy results in a stronger decoupling between the flow above and inside the canopy. As the investigation period covers April and May 2009, this gives the opportunity to discern between leaf-off (at the beginning) and leaf-on periods, with a proposed increase in decoupling with time. The aim of the study is to derive characteristic patterns of wind and atmospheric stability within the forest canopy for leaf-off and leaf-on periods as well as for days of intense versus negligible pollen production.

Contrasting Spatial Patterns in Active-Fire and Fire-Suppressed Mediterranean Climate Old-Growth Mixed Conifer Forests

PubMed Central

Fry, Danny L.; Stephens, Scott L.; Collins, Brandon M.; North, Malcolm P.; Franco-Vizcaíno, Ernesto; Gill, Samantha J.

2014-01-01

In Mediterranean environments in western North America, historic fire regimes in frequent-fire conifer forests are highly variable both temporally and spatially. This complexity influenced forest structure and spatial patterns, but some of this diversity has been lost due to anthropogenic disruption of ecosystem processes, including fire. Information from reference forest sites can help management efforts to restore forests conditions that may be more resilient to future changes in disturbance regimes and climate. In this study, we characterize tree spatial patterns using four-ha stem maps from four old-growth, Jeffrey pine-mixed conifer forests, two with active-fire regimes in northwestern Mexico and two that experienced fire exclusion in the southern Sierra Nevada. Most of the trees were in patches, averaging six to 11 trees per patch at 0.007 to 0.014 ha−1, and occupied 27–46% of the study areas. Average canopy gap sizes (0.04 ha) covering 11–20% of the area were not significantly different among sites. The putative main effects of fire exclusion were higher densities of single trees in smaller size classes, larger proportion of trees (≥56%) in large patches (≥10 trees), and decreases in spatial complexity. While a homogenization of forest structure has been a typical result from fire exclusion, some similarities in patch, single tree, and gap attributes were maintained at these sites. These within-stand descriptions provide spatially relevant benchmarks from which to manage for structural heterogeneity in frequent-fire forest types. PMID:24586472

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

Maurer, K. D.; Bohrer, G.; Kenny, W. T.

Surface roughness parameters, namely the roughness length and displacement height, are an integral input used to model surface fluxes. However, most models assume these parameters to be a fixed property of plant functional type and disregard the governing structural heterogeneity and dynamics. In this study, we use large-eddy simulations to explore, in silico, the effects of canopy-structure characteristics on surface roughness parameters. We performed a virtual experiment to test the sensitivity of resolved surface roughness to four axes of canopy structure: (1) leaf area index, (2) the vertical profile of leaf density, (3) canopy height, and (4) canopy gap fraction.more » We found roughness parameters to be highly variable, but uncovered positive relationships between displacement height and maximum canopy height, aerodynamic canopy height and maximum canopy height and leaf area index, and eddy-penetration depth and gap fraction. We also found negative relationships between aerodynamic canopy height and gap fraction, as well as between eddy-penetration depth and maximum canopy height and leaf area index. We generalized our model results into a virtual "biometric" parameterization that relates roughness length and displacement height to canopy height, leaf area index, and gap fraction. Using a decade of wind and canopy-structure observations in a site in Michigan, we tested the effectiveness of our model-driven biometric parameterization approach in predicting the friction velocity over heterogeneous and disturbed canopies. We compared the accuracy of these predictions with the friction-velocity predictions obtained from the common simple approximation related to canopy height, the values calculated with large-eddy simulations of the explicit canopy structure as measured by airborne and ground-based lidar, two other parameterization approaches that utilize varying canopy-structure inputs, and the annual and decadal means of the surface roughness parameters at the site from meteorological observations. We found that the classical representation of constant roughness parameters (in space and time) as a fraction of canopy height performed relatively well. Nonetheless, of the approaches we tested, most of the empirical approaches that incorporate seasonal and interannual variation of roughness length and displacement height as a function of the dynamics of canopy structure produced more precise and less biased estimates for friction velocity than models with temporally invariable parameters.« less

Tropical forest carbon balance: effects of field- and satellite-based mortality regimes on the dynamics and the spatial structure of Central Amazon forest biomass

NASA Astrophysics Data System (ADS)

Di Vittorio, Alan V.; Negrón-Juárez, Robinson I.; Higuchi, Niro; Chambers, Jeffrey Q.

2014-03-01

Debate continues over the adequacy of existing field plots to sufficiently capture Amazon forest dynamics to estimate regional forest carbon balance. Tree mortality dynamics are particularly uncertain due to the difficulty of observing large, infrequent disturbances. A recent paper (Chambers et al 2013 Proc. Natl Acad. Sci. 110 3949-54) reported that Central Amazon plots missed 9-17% of tree mortality, and here we address ‘why’ by elucidating two distinct mortality components: (1) variation in annual landscape-scale average mortality and (2) the frequency distribution of the size of clustered mortality events. Using a stochastic-empirical tree growth model we show that a power law distribution of event size (based on merged plot and satellite data) is required to generate spatial clustering of mortality that is consistent with forest gap observations. We conclude that existing plots do not sufficiently capture losses because their placement, size, and longevity assume spatially random mortality, while mortality is actually distributed among differently sized events (clusters of dead trees) that determine the spatial structure of forest canopies.

Air-Parcel Residence Times Within Forest Canopies

NASA Astrophysics Data System (ADS)

Gerken, Tobias; Chamecki, Marcelo; Fuentes, Jose D.

2017-10-01

We present a theoretical model, based on a simple model of turbulent diffusion and first-order chemical kinetics, to determine air-parcel residence times and the out-of-canopy export of reactive gases emitted within forest canopies under neutral conditions. Theoretical predictions of the air-parcel residence time are compared to values derived from large-eddy simulation for a range of canopy architectures and turbulence levels under neutral stratification. Median air-parcel residence times range from a few sec in the upper canopy to approximately 30 min near the ground and the distribution of residence times is skewed towards longer times in the lower canopy. While the predicted probability density functions from the theoretical model and large-eddy simulation are in good agreement with each other, the theoretical model requires only information on canopy height and eddy diffusivities inside the canopy. The eddy-diffusivity model developed additionally requires the friction velocity at canopy top and a parametrized profile of the standard deviation of vertical velocity. The theoretical model of air-parcel residence times is extended to include first-order chemical reactions over a range of of Damköhler numbers ( Da) characteristic of plant-emitted hydrocarbons. The resulting out-of-canopy export fractions range from near 1 for Da =10^{-3} to less than 0.3 at Da = 10. These results highlight the necessity for dense and tall forests to include the impacts of air-parcel residence times when calculating the out-of-canopy export fraction for reactive trace gases.

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.

Effects of forest management on California Spotted Owls: implications for reducing wildfire risk in fire‐prone forests.

PubMed

Tempel, Douglas J; Gutiérrez, R J; Whitmore, Sheila A; Reetz, Matthew J; Stoelting, Ricka E; Berigan, William J; Seamans, Mark E; Zachariah Peery, M

Management of many North American forests is challenged by the need to balance the potentially competing objectives of reducing risks posed by high-severity wildfires and protecting threatened species. In the Sierra Nevada, California, concern about high-severity fires has increased in recent decades but uncertainty exists over the effects of fuel-reduction treatments on species associated with older forests, such as the California Spotted Owl (Strix occidentalis occidentalis). Here, we assessed the effects of forest conditions, fuel reductions, and wildfire on a declining population of Spotted Owls in the central Sierra Nevada using 20 years of demographic data collected at 74 Spotted Owl territories. Adult survival and territory colonization probabilities were relatively high, while territory extinction probability was relatively low, especially in territories that had relatively large amounts of high canopy cover (≥70%) forest. Reproduction was negatively associated with the area of medium-intensity timber harvests characteristic of proposed fuel treatments. Our results also suggested that the amount of edge between older forests and shrub/sapling vegetation and increased habitat heterogeneity may positively influence demographic rates of Spotted Owls. Finally, high-severity fire negatively influenced the probability of territory colonization. Despite correlations between owl demographic rates and several habitat variables, life stage simulation (sensitivity) analyses indicated that the amount of forest with high canopy cover was the primary driver of population growth and equilibrium occupancy at the scale of individual territories. Greater than 90% of medium-intensity harvests converted high-canopy-cover forests into lower-canopy-cover vegetation classes, suggesting that landscape-scale fuel treatments in such stands could have short-term negative impacts on populations of California Spotted Owls. Moreover, high-canopy-cover forests declined by an average of 7.4% across territories during our study, suggesting that habitat loss could have contributed to declines in abundance and territory occupancy. We recommend that managers consider the existing amount and spatial distribution of high-canopy forest before implementing fuel treatments within an owl territory, and that treatments be accompanied by a rigorous monitoring program.

Changes in canopy cover alter surface air and forest floor temperature in a high-elevation red spruce (Picea rubens Sarg.) forest

Treesearch

Johnny L. Boggs; Steven G. McNulty

2010-01-01

The objective of this study is to describe winter and summer surface air and forest floor temperature patterns and diurnal fluctuations in high-elevation red spruce (Picea rubens Sarg.) forests with different levels of canopy cover. In 1988, a series of 10- x 10-meter plots (control, low nitrogen [N] addition, and high nitrogen addition) were...

On the vertical distribution of bees in a temperate deciduous forest

Treesearch

Michael Ulyshen; Villa Soon; James Hanula

2010-01-01

1. Despite a growing interest in forest canopy biology, very few studies have examined the vertical distribution of forest bees. In this study, bees were sampled using 12 pairs of flight-intercept traps suspended in the canopy (‡15 m) and near the ground (0.5 m) in a bottomland hardwood forest in the southeastern United States. 2. In total, 6653 bees from 5 families...

Variations in canopy and litter interception across a forest chronosequence in the southern Appalachian Mountains

Treesearch

Steven T. Brantley; Paul V. Bolstad; Stephanie H. Laseter; A. Christopher Oishi; Kimberly A. Novick; Chelcy F. Miniat

2016-01-01

Variations in evapotranspiration (ET) have been well documented across a variety of forest types and climates in recent decades; however, most of these data have focused on mature, secondgrowth stands. Here we present data on two important fluxes of water, canopy interception (Ic) and forest floor litter interception (Iff), across a chronosequence of forest age in the...

Mapping forest height in Alaska using GLAS, Landsat composites, and airborne LiDAR

USGS Publications Warehouse

Peterson, Birgit; Nelson, Kurtis

2014-01-01

Vegetation structure, including forest canopy height, is an important input variable to fire behavior modeling systems for simulating wildfire behavior. As such, forest canopy height is one of a nationwide suite of products generated by the LANDFIRE program. In the past, LANDFIRE has relied on a combination of field observations and Landsat imagery to develop existing vegetation structure products. The paucity of field data in the remote Alaskan forests has led to a very simple forest canopy height classification for the original LANDFIRE forest height map. To better meet the needs of data users and refine the map legend, LANDFIRE incorporated ICESat Geoscience Laser Altimeter System (GLAS) data into the updating process when developing the LANDFIRE 2010 product. The high latitude of this region enabled dense coverage of discrete GLAS samples, from which forest height was calculated. Different methods for deriving height from the GLAS waveform data were applied, including an attempt to correct for slope. These methods were then evaluated and integrated into the final map according to predefined criteria. The resulting map of forest canopy height includes more height classes than the original map, thereby better depicting the heterogeneity of the landscape, and provides seamless data for fire behavior analysts and other users of LANDFIRE data.

Effect of canopy removal on snowpack quantity and quality, fraser experimental forest, Colorado

USGS Publications Warehouse

Stottlemyer, R.; Troendle, C.A.

2001-01-01

Snowpack peak water equivalent (PWE), ion concentration, content, and spatial distribution of ion load data from spring 1987-1996 in a 1 ha clearcut and adjacent forested plots vegetated by mature Picea engelmannii and Abies lasiocarpa in the Fraser experimental forest (FEF), Colorado are presented. Our objectives were: (1) to see if a forest opening might redistribute snowfall, snowpack moisture, and snowpack chemical content, and (2) to examine the importance of canopy interception on snowpack quantity and chemistry. On an average, the canopy intercepted 36% of snowfall. Interception was correlated with snowfall amount, snowpack PWE beneath the canopy, and air temperature. Canopy removal increased snowpack PWE to >90% cumulative snowfall inputs. Snowpack K-, H-, and NH4+ concentrations on the clearcut were lower and NO3- higher than in the snowpack beneath the forested plots. Cu mulative snowfall K+ input was less than in the clearcut snowpack; H+ inputs were greater in snowfall than in the snowpack of any plot; and inorganic N (NO3- and NH4+) inputs from snowfall to the clearcut were greater than to the forested plots. Processes accounting for the differences between snowfall inputs and snowpack ion content were leaching of organic debris in the snowpack, differential elution of the snowpack, and canopy retention. There were significant trends by year in snowpack ion content at PWE without similar trends in snowfall inputs. This finding coupled with snowpack ion elution bring into question the use of snowpack chemistry as an indicator of winter atmospheric inputs in short-term studies. ?? 2001 Elsevier Science B.V.

Influence of the forest canopy on total and methyl mercury deposition in the boreal forest

Treesearch

E.L. Witt; R.K. Kolka; E.A. Nater; T.R. Wickman

2009-01-01

Atmospheric mercury deposition by wet and dry processes contributes mercury to terrestrial and aquatic systems. Factors influencing the amount of mercury deposited to boreal forests were identified in this study. Throughfall and open canopy precipitation samples were collected in 2005 and 2006 using passive precipitation collectors from pristine sites located across...

Forest fire effects on mercury deposition in the boreal forest

Treesearch

Emma L. Witt; Randall K. Kolka; Edward A. Nater; Trent R. Wickman

2009-01-01

The objective of this study was to determine how forest fire effects Hg deposition to nearby landscapes impacted by smoke plumes. Hg concentrations and deposition were hypothesized to increase in throughfall and open precipitation after fire, and canopy type was hypothesized to influence the magnitude of the increase. Conifer canopies, which are better able to scavenge...

Mapping forest canopy disturbance in the Upper Great Lakes, USA

Treesearch

James D. Garner; Mark D. Nelson; Brian G. Tavernia; Charles H. (Hobie) Perry; Ian W. Housman

2015-01-01

A map of forest canopy disturbance was generated for Michigan, Wisconsin, and most of Minnesota using 42 Landsat time series stacks (LTSS) and a vegetation change tracker (VCTw) algorithm. Corresponding winter imagery was used to reduce commission errors of forest disturbance by identifying areas of persistent snow cover. The resulting disturbance age map was classed...

Patterns of covariance between forest stand and canopy structure in the Pacific Northwest.

Treesearch

Michael A. Lefsky; Andrew T. Hudak; Warren B. Cohen; S.A. Acker

2005-01-01

In the past decade, LIDAR (light detection and ranging) has emerged as a powerful tool for remotely sensing forest canopy and stand structure, including the estimation of aboveground biomass and carbon storage. Numerous papers have documented the use of LIDAR measurements to predict important aspects of forest stand structure, including aboveground biomass. Other...

Snow accumulation under various forest stand densities at Tenderfoot Creek Experimental Forest, Montana, USA

Treesearch

Chadwick A. Moore; Ward W. McCaughey

1997-01-01

Snow accumulation in forested watersheds is controlled by climate, elevation, topographic factors and vegetation structure. Conifers affect snow accumulation principally by intercepting snow with the canopy which may later be sublimated. Various tree, stand, species and canopy densities of a subalpine fir habitat (ALBANASC) in central Montana were studied to determine...

Seven-year responses of trees to experimental hurricane effects in a tropical rainforest, Puerto Rico

Treesearch

Jess K. Zimmerman; James Aaron Hogan; Aaron B. Shiels; John E. Bithorn; Samuel Matta Carmona; Nicholas Brokaw

2014-01-01

We experimentally manipulated key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on tree recruitment, forest structure, and diversity in a wet tropical forest in the Luquillo Experimental Forest, Puerto Rico. Canopy openness was increased by trimming branches...

Estimates of forest canopy height and aboveground biomass using ICESat.

Treesearch

Michael A. Lefsky; David J. Harding; Michael Keller; Warren B. Cohen; Claudia C. Carabajal; Fernando Del Bom Espirito-Santo; Maria O. Hunter; Raimundo de Oliveira Jr.

2005-01-01

Exchange of carbon between forests and the atmosphere is a vital component of the global carbon cycle. Satellite laser altimetry has a unique capability for estimating forest canopy height, which has a direct and increasingly well understood relationship to aboveground carbon storage. While the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud and land...

Establishment of an invasive grass in closed-canopy deciduous forests across local and regional environmental gradients

Treesearch

Cynthia D. Huebner

2010-01-01

Establishment of Microstegium vimineum, an invasive exotic grass, in closed-canopy U.S. eastern forests was evaluated across a local (roadside to forest interior) and regional (across two geographic provinces) environmental gradient in West Virginia. The two geographic provinces were the Allegheny Plateau (more mesic) and the Ridge and Valley...

Rainfall Interception by Hardwood Forest Litter in the Southern Appalachians

Treesearch

J.D. Helvey

1964-01-01

The portion of rainfall over forest cover which does not reach mineral soil can be separated into the parts evaporated from the canopy and from the litter. Canopy interception loss is usually estimated by subtracting the sum of throughfall (water falling through tree crowns) and stemflow (water running down stems) from rainfall measured in forest openings (Hamilton...

Modelling the vertical distribution of canopy fuel load using national forest inventory and low-density airbone laser scanning data.

PubMed

González-Ferreiro, Eduardo; Arellano-Pérez, Stéfano; Castedo-Dorado, Fernando; Hevia, Andrea; Vega, José Antonio; Vega-Nieva, Daniel; Álvarez-González, Juan Gabriel; Ruiz-González, Ana Daría

2017-01-01

The fuel complex variables canopy bulk density and canopy base height are often used to predict crown fire initiation and spread. Direct measurement of these variables is impractical, and they are usually estimated indirectly by modelling. Recent advances in predicting crown fire behaviour require accurate estimates of the complete vertical distribution of canopy fuels. The objectives of the present study were to model the vertical profile of available canopy fuel in pine stands by using data from the Spanish national forest inventory plus low-density airborne laser scanning (ALS) metrics. In a first step, the vertical distribution of the canopy fuel load was modelled using the Weibull probability density function. In a second step, two different systems of models were fitted to estimate the canopy variables defining the vertical distributions; the first system related these variables to stand variables obtained in a field inventory, and the second system related the canopy variables to airborne laser scanning metrics. The models of each system were fitted simultaneously to compensate the effects of the inherent cross-model correlation between the canopy variables. Heteroscedasticity was also analyzed, but no correction in the fitting process was necessary. The estimated canopy fuel load profiles from field variables explained 84% and 86% of the variation in canopy fuel load for maritime pine and radiata pine respectively; whereas the estimated canopy fuel load profiles from ALS metrics explained 52% and 49% of the variation for the same species. The proposed models can be used to assess the effectiveness of different forest management alternatives for reducing crown fire hazard.

Kinetic energy of throughfall in a highly diverse forest ecosystem in the humid subtropics

NASA Astrophysics Data System (ADS)

Geißler, Christian; Kühn, Peter; Scholten, Thomas

2010-05-01

After decades of research it is generally accepted that vegetation is a key factor in controlling soil erosion. Therefore, in ecosystems where erosion is a serious problem, afforestation is a common measure against erosion. Most of the studies in the last decades focused on agricultural systems and less attention was paid to natural systems. To understand the mechanisms preventing soil erosion in natural systems the processes have to be studied in detail and gradually. The first step and central research question is on how the canopies of the tree layer alter the properties of rainfall and generate throughfall. Kinetic energy is a widely used parameter to estimate the erosion potential of open field rainfall and throughfall. In the past, numerous studies have shown that vegetation of a certain height enhances the kinetic energy under the canopy (Chapman 1948, Mosley 1982, Vis 1986, Hall & Calder 1993, Nanko et al. 2006, Nanko et al. 2008) in relation to open field rainfall. This is mainly due to a shift in the drop size distribution to less but larger drops possessing a higher amount of kinetic energy. In vital forest ecosystems lower vegetation (shrubs, herbs) as well as a continuous litter layer protects the forest soil from the impact of large drops. The influence of biodiversity, specific forest stands or single species in this process system is still in discussion. In the present study calibrated splash cups (after Ellison 1947, Geißler et al. under review) have been used to detect differences in kinetic energy on the scale of specific species and on the scale of forest stands of contrasting age and biodiversity in a natural forest ecosystem. The splash cups have been calibrated experimentally using a laser disdrometer. The results show that the kinetic energy of throughfall produced by the tree layer increases with the age of the specific forest stand. The average throughfall kinetic energy (J m-2) is about 2.6 times higher in forests than under open field conditions. Most of the energy is supposed to be absorbed by shrubs, herbs and the litter layer. For some species in the shrub and herb layer throughfall drops are crucial for seed dispersal (Nakanishi 2002). A higher kinetic energy of throughfall should be advantageous for seed dispersal and probably support biodiversity. Further, it is shown that the variability of kinetic energy in forests varies among the age of the forest stand which can be related to the forest structure. In our case there is a high variability in young forests (< 30 years) due to selective logging (some older trees were left out) and gaps in the tree layer. Old forests (> 80 years) also have a high variability in kinetic energy. There, external influences like snow and wind break result in a fragmentary tree layer which allows less erosive rainfall to reach the forest floor. Medium aged forests are more homogenous regarding canopy closure or tree heights. Generally, the variability of kinetic energy in forests is increasing with the amount of rainfall. Moreover, it is shown that the kinetic energy of throughfall is species specific. For the investigated tree species the values range between 24.41 J m-2 mm-1 (Daphniphyllum oldhamii) and 33.24 J m-2 mm-1 (Schima superba) while the concurrent rainfall in the open field has an average kinetic energy of 6.75 J m-2 mm-1. Leaf size and canopy architecture are supposed to be two of the controlling variables for specific species. These results give implications for afforestation measures and are important input variables for modeling of erosion processes. Chapman, G., 1948. Size of raindrops and their striking force at the soil surface in a Red Pine plantation. Transactions - American Geophysical Union, 29: 664-670. Ellison, W.D., 1947. Soil Erosion Studies - Part II. Agricultural Engineering, 28: 197-201. Geißler, C., Kühn, P., Böhnke, M., Bruelheide, H., Shi, X., Scholten, T., under review: Measuring splash erosion potential under vegetation using sand-filled splash cups. Hall, R.L., Calder, I.R., 1993. Drop size modification by forest canopies: measurements using a disdrometer. Journal of Geophysical Research (D10), 98: 18465-18470. Mosley, M.P., 1982. The effect of a New Zealand beech forest canopy on the kinetic energy of water drops and on surface erosion. Earth Surface Processes and Landforms, 7: 103-107. Nakanishi, H., 2002. Splash dispersal by raindrops. Ecological research, 17: 663-671. Nanko, K., Hotta, N., Suzuki, M., 2006. Evaluating the influence of canopy species and meteorological factors on throughfall drop size distribution. Journal of Hydrology, 329: 422-431. Nanko, K., Mizugaki, S., Onda, Y., 2008. Estimation of soil splash detachment rates on the forest floor of an unmanaged Japanese cypress plantation based on field measurements of throughfall drop sizes and velocities. Catena, 72: 348-361. Vis, M., 1986. Interception, drop size distribution and rainfall kinetic energy in four Columbian forest ecosystems. Earth Surface Processes and Landforms, 11: 591-603.

Evaluating UAV and LiDAR Retrieval of Snow Depth in a Coniferous Forest in Arizona

NASA Astrophysics Data System (ADS)

Van Leeuwen, W. J. D.; Broxton, P.; Biederman, J. A.

2017-12-01

Remote sensing of snow depth and cover in forested environments is challenging. Trees interfere with the remote sensing of snowpack below the canopy and cause large variations in the spatial distribution of the snowpack itself (e.g. between below canopy environments to shaded gaps to open clearings). The distribution of trees and topographic variation make it challenging to monitor the snowpack with in-situ observations. Airborne LiDAR has improved our ability to monitor snowpack over large areas in montane and forested environments because of its high sampling rate and ability to penetrate the canopy. However, these LiDAR flights can be too expensive and time-consuming to process, making it hard to use them for real-time snow monitoring. In this research, we evaluate Structure from Motion (SfM) as an alternative to Airborne LiDAR to generate high-resolution snow depth data in forested environments. This past winter, we conducted a snow field campaign over Arizona's Mogollon Rim where we acquired aerial LiDAR, multi-angle aerial photography from a UAV, and extensive field observations of snow depth at two sites. LiDAR and SFM derived snow depth maps were generated by comparing "snow-on" and "snow-off" LiDAR and SfM data. The SfM- and LiDAR-generated snow depth maps were similar at a site with fewer trees, though there were more discrepancies at a site with more trees. Both compared reasonably well with the field observations at the sparser forested site, with poorer agreement at the denser forested site. Finally, although the SfM produced point clouds with much higher point densities than the aerial LiDAR, the SfM was not able to produce meaningful snow depth estimates directly underneath trees and had trouble in areas with deep shadows. Based on these findings, we are optimizing our UAV data acquisition strategies for this upcoming field season. We are using these data, along with high-resolution hydrological modeling, to gain a better understanding of how different forest structural, climatic and topographic conditions affect the snowpack and consequently the water resources available to the Salt River Project, a water utility providing power and water to millions of customers in the Phoenix area

Canopy tree species drive local heterogeneity in soil nitrogen availability in a lowland tropical forest

NASA Astrophysics Data System (ADS)

Osborne, B. B.; Nasto, M.; Asner, G. P.; Balzotti, C.; Cleveland, C. C.; Taylor, P.; Townsend, A. R.; Porder, S.

2016-12-01

The high phylogenetic and functional diversity of tree species in lowland tropical forests make field-based investigations of organismal influences on soil nutrient cycling challenging. Here, we used remotely-detected canopy nitrogen (N) data from the Carnegie Airborne Observatory to identify and characterize ¼ ha plots of a mature forest with either high or low canopy N on the Osa Peninsula in Costa Rica. Specifically we were interested in mechanisms by which foliar N might influence soil N, or the reverse. A non-dimensional scaling analysis suggested that high and low canopy N plots differ in their emergent (≥40 cm DBH) tree communities, though there were few putative N fixers in any of the plots. We found litterfall mass was similar beneath all canopies. However, mean DOC solubility of litter was 0.40% of dry biomass in low canopy N plots compared to 0.26% in high N plots. Additionally, litter leachate C:N was twice as high in litter from the low canopy N plots (61±1.4) compared with litter from the high N plots (30±1.4). We found strong positive correlations between canopy N and concentrations of soil KCl-extractable soil NO3- and net nitrification and net N mineralization rates (N=5; P<0.0001 in all cases). Under high canopy N, mean NO3-N concentrations were roughly an order of magnitude higher than beneath low N canopies (2.7±0.39 and 0.19±0.05, respectively). We hypothesize that differences in litter chemistry lead to differences in leachate quality that promote high soil N under canopies with high foliar N. Our findings suggest that remote sensing of foliar characteristics may offer an effective way to study spatial patterns in soil biogeochemistry in diverse tropical forests.