Science.gov

Sample records for canopy scale valutazione

  1. Scaling leaf measurements to estimate cotton canopy gas exchange

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diurnal leaf and canopy gas exchange of well watered field grown cotton were measured. Leaf measurements were made with a portable photosynthesis system and canopy measurements with open Canopy Evapo-Transpiration and Assimilation (CETA) systems. Leaf level measurements were arithmetically scaled to...

  2. [Valutazione delle guardie di sicurezza privata attraverso la Suicide Probability Scale e la Brief Symptom Inventory].

    PubMed

    Dogan, Bulent; Canturk, Gurol; Canturk, Nergis; Guney, Sevgi; Özcan, Ebru

    2016-01-01

    RIASSUNTO. Scopo. Lo scopo di questo studio è stato quello di investigare l'influenza della probabilità di suicidio, con le sue caratteristiche sociodemografiche, e di procurare i dati per la prevenzione del suicidio tra le guardie di sicurezza privata che lavorano in condizioni di stress, essendo a contatto ininterrottamente con eventi negativi e traumatici di vita durante il loro lavoro. Metodi. Hanno partecipato allo studio 200 guardie di sicurezza privata e 200 persone dell'Università di Ankara. Per raccogliere i dati sono stati utilizzati un questionario riguardante le condizioni sociodemografiche dei partecipanti, la Suicide Probability Scale (SPS) e la Brief Symptom Inventory (BSI). Risultati. Genere, stato civile, stipendio, credenze religiose, vivere una situazione di pericolo di vita, passato di tentativi di suicidio, fumare e non avere una malattia cronica hanno causato statisticamente una differenza significativa sui punteggi di SPS tra il gruppo di guardie di sicurezza privata e quello di controllo. In aggiunta, c'è stata una correlazione positiva statisticamente significativa tra i punteggi totali delle sottoscale di SPS e quelli di BSI. Conclusioni. Allo stesso modo degli agenti di polizia e dei gendarmi, le guardie di sicurezza privata sono ad alto rischio di commettere e tentare il suicidio trovandosi in condizioni stressanti di lavoro e anche soffrendo del trauma secondario. È necessario che essi siano consapevoli della propria tendenza al suicidio e avere controlli psichiatrici regolari.

  3. Temporal Scales of the Nocturnal Flow Within and Above a Forest Canopy in Amazonia

    NASA Astrophysics Data System (ADS)

    Santos, Daniel M.; Acevedo, Otávio C.; Chamecki, Marcelo; Fuentes, José D.; Gerken, Tobias; Stoy, Paul C.

    2016-10-01

    Multiresolution decomposition is applied to 10 months of nocturnal turbulence observations taken at eight levels within and above a forest canopy in Central Amazonia. The aim is to identify the contributions of different temporal scales of the flow above and within the canopy. Results show that turbulence intensity in the lower canopy is mostly affected by the static stability in the upper canopy. Horizontal velocity fluctuations peak at time scales longer than 100 s within the canopy, which correspond to the scale of non-turbulent submeso motions above the canopy. In the vertical velocity spectrum near the surface, the peak occurs at time scales around 100 s, which are larger than the time scales of the turbulent flow above the canopy. Heat-flux cospectra within the canopy peak at the same temporal scales as the vertical velocity fluctuations at that level, suggesting the existence of buoyancy driven turbulence. Case studies are presented as evidence that low-frequency fluctuations propagate towards the canopy interior more easily than does turbulence.

  4. The impact of beetle-induced conifer death on stand-scale canopy snow interception

    NASA Astrophysics Data System (ADS)

    Pugh, E. T.; Small, E. E.

    2011-12-01

    Snow that falls on a forest either passes through the canopy to the ground or is intercepted by the canopy on needles, branches or bark. The interception of snowfall in forest canopies impacts the water budget because intercepted snow is more likely to sublimate than subcanopy snow. Because forest canopy characteristics are a primary control of canopy snow interception, which in turn controls subcanopy snow accumulation, reductions in canopy density have important implications for snow accumulation on the forest floor. Forest structure can be drastically and rapidly altered by forest disturbance, such as insect attack, wildfire and blowdown. Here, we look at the impact that changing forest characteristics associated with beetle infestation have on canopy snow interception. The mountain pine beetle is currently impacting more than 100,000 km2 of pine forest in western North America. Trees killed by bark beetles eventually lose the majority of their canopy material. We hypothesize that tree death significantly reduces available interception platforms, leading to greater subcanopy snow accumulation than pre-infestation conditions. These potential impacts on snow accumulation are especially important for water resources in the western U.S., where the hydrologic cycle is dominated by snowmelt. We test this hypothesis using extensive data collected from adjacent living and grey phase dead stands. We employ multiple methods to measure canopy snow interception, at both the storm- and season-scales. During the winter of 2011, we made more than 10,000 spatially distributed measurements of subcanopy snow accumulation in three living and two dead lodgepole pine stands as well as three clearings. Measurements were made daily as well as immediately prior to and following storm events, allowing us to calculate storm-scale canopy interception. Interception is estimated by comparing subcanopy snow accumulation in clearings and forests. Additionally, by taking repeated daily

  5. Spectral measurements at different spatial scales in potato: relating leaf, plant and canopy nitrogen status

    NASA Astrophysics Data System (ADS)

    Jongschaap, Raymond E. E.; Booij, Remmie

    2004-09-01

    Chlorophyll contents in vegetation depend on soil nitrogen availability and on crop nitrogen uptake, which are important management factors in arable farming. Crop nitrogen uptake is important, as nitrogen is needed for chlorophyll formation, which is important for photosynthesis, i.e. the conversion of absorbed radiance into plant biomass. The objective of this study was to estimate leaf and canopy nitrogen contents by near and remote sensing observations and to link observations at leaf, plant and canopy level. A theoretical base is presented for scaling-up leaf optical properties to whole plants and crops, by linking different optical recording techniques at leaf, plant and canopy levels through the integration of vertical nitrogen distribution. Field data come from potato experiments in The Netherlands in 1997 and 1998, comprising two potato varieties: Eersteling and Bintje, receiving similar nitrogen treatments (0, 100, 200 and 300 kg N ha -1) in varying application schemes to create differences in canopy nitrogen status during the growing season. Ten standard destructive field samplings were performed to follow leaf area index and crop dry weight evolution. Samples were analysed for inorganic nitrogen and total nitrogen contents. At sampling dates, spectral measurements were taken both at leaf level and at canopy level. At leaf level, an exponential relation between SPAD-502 readings and leaf organic nitrogen contents with a high correlation factor of 0.91 was found. At canopy level, an exponential relation between canopy organic nitrogen contents and red edge position ( λrep, nm) derived from reflectance measurements was found with a good correlation of 0.82. Spectral measurements (SPAD-502) at leaf level of a few square mm were related to canopy reflectance measurements (CropScan™) of approximately 0.44 m 2. Statistical regression techniques were used to optimise theoretical vertical nitrogen profiles that allowed scaling-up leaf chlorophyll measurements

  6. Scaling uncertainties in estimating canopy foliar maintenance respiration for black spruce ecosystems in Alaska

    USGS Publications Warehouse

    Zhang, X.; McGuire, A.D.; Ruess, Roger W.

    2006-01-01

    A major challenge confronting the scientific community is to understand both patterns of and controls over spatial and temporal variability of carbon exchange between boreal forest ecosystems and the atmosphere. An understanding of the sources of variability of carbon processes at fine scales and how these contribute to uncertainties in estimating carbon fluxes is relevant to representing these processes at coarse scales. To explore some of the challenges and uncertainties in estimating carbon fluxes at fine to coarse scales, we conducted a modeling analysis of canopy foliar maintenance respiration for black spruce ecosystems of Alaska by scaling empirical hourly models of foliar maintenance respiration (Rm) to estimate canopy foliar Rm for individual stands. We used variation in foliar N concentration among stands to develop hourly stand-specific models and then developed an hourly pooled model. An uncertainty analysis identified that the most important parameter affecting estimates of canopy foliar Rm was one that describes R m at 0??C per g N, which explained more than 55% of variance in annual estimates of canopy foliar Rm. The comparison of simulated annual canopy foliar Rm identified significant differences between stand-specific and pooled models for each stand. This result indicates that control over foliar N concentration should be considered in models that estimate canopy foliar Rm of black spruce stands across the landscape. In this study, we also temporally scaled the hourly stand-level models to estimate canopy foliar Rm of black spruce stands using mean monthly temperature data. Comparisons of monthly Rm between the hourly and monthly versions of the models indicated that there was very little difference between the estimates of hourly and monthly models, suggesting that hourly models can be aggregated to use monthly input data with little loss of precision. We conclude that uncertainties in the use of a coarse-scale model for estimating canopy foliar

  7. Contrasting effects of sampling scale on insect herbivores distribution in response to canopy structure.

    PubMed

    Neves, Frederico S; Sperber, Carlos F; Campos, Ricardo I; Soares, Janaína P; Ribeiro, Sérvio P

    2013-03-01

    Species diversity of insect herbivores associated to canopy may vary local and geographically responding to distinct factors at different spatial scales. The aim of this study was to investigate how forest canopy structure affects insect herbivore species richness and abundance depending on feeding guilds' specificities. We tested the hypothesis that habitat structure affects insect herbivore species richness and abundance differently to sap-sucking and chewing herbivore guilds. Two spatial scales were evaluated: inside tree crowns (fine spatial cale) and canopy regions (coarse spatial scale). In three sampling sites we measured 120 tree crowns, grouped n five points with four contiguous tree crowns. Insects were sampled by beating method from each crown and data were summed up for analyzing each canopy region. In crowns (fine spatial scale) we measured habitat tructure: trunk circumference, tree height, canopy depth, number of ramifications and maximum ramification level. In each point, defined as a canopy region (coarse spatial scale), we measured habitat structure using a vertical cylindrical transect: tree species richness, leaf area, sum of strata heights and maximum canopy height. A principal component analysis based on the measured variables for each spatial scale was run to estimate habitat structure parameters. To test the effects of habitat structure upon herbivores, different general linear models were adjusted using the first two principal components as explanatory variables. Sap-sucking insect species richness and all herbivore abundances increased with size of crown at fine spatial scale. On the other hand, chewer species richness and abundance increased with resource quantity at coarse scale. Feeding specialization, resources availability, and agility are discussed as ecological causes of the found pattern.

  8. Modelling canopy scale solar induced chlorophyll fluorescence simulated by the three dimensional radiative transfer model

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Nagai, S.; Inoue, T.; Yang, W.; Ichii, K.

    2014-12-01

    Recent studies show that the vegetation canopy scale sun-induced chlorophyll fluorescence (SIF) can be observed from satellite. To understand how the canopy scale bidirectional fluorescence observations are related to three-dimensional fluorescence distribution within a plant canopy, it is necessary to evaluate canopy scale fluorescence emission using a detailed plant canopy radiative transfer model. In this study, we developed a three-dimensional plant canopy radiative transfer model that can simulate the bidirectional chlorophyll fluorescence radiance and show several preliminary results of fluorescence distribution at the tree level. To simulate the three dimensional variations in chlorophyll fluorescence from trees, we measured tree structures using a terrestrial LiDAR instrument. The measurements were conducted in Yokohama, Japan (35°22'49" N 139°37'29" E). Three Japanese cherry trees (Cerasus Speciosa) were chosen for our study (Figure 1). Leaf-level sun-induced chlorophyll fluorescence (SIF) is also necessary as an input of radiative transfer model. To measure the leaf-level SIF, we used high spectral resolution spectroradiometer (HR 4000, Ocean Optics Inc. USA). The spectral resolution of this instrument is 0.05 nm (full width half maximum). The spectral range measured was 720 to 780 nm. From the spectral radiance measurements, we estimated SIF using the three band Fraunhofer Line Depth (3FLD) method. The effect of solar and view zenith angles, multiple scattering depends on many factors such as back ground reflectance, leaf reflectance transmittance and landscape structures. To understand how the SIF from both sparse and dense forest stands vary with sun and view angles and optical variables, it is necessary to conduct further sensitivity analysis. Radiative transfer simulation will help understand SIF emission at variety of forest canopy cases.

  9. Evaluating Uncertainties in Sap Flux Scaled Estimates of Forest Transpiration, Canopy Conductance and Photosynthesis

    NASA Astrophysics Data System (ADS)

    Ward, E. J.; Bell, D. M.; Clark, J. S.; Kim, H.; Oren, R.

    2009-12-01

    Thermal dissipation probes (TDPs) are a common method for estimating forest transpiration and canopy conductance from sap flux rates in trees, but their implementation is plagued by uncertainties arising from missing data and variability in the diameter and canopy position of trees, as well as sapwood conductivity within individual trees. Uncertainties in estimates of canopy conductance also translate into uncertainties in carbon assimilation in models such as the Canopy Conductance Constrained Carbon Assimilation (4CA) model that combine physiological and environmental data to estimate photosynthetic rates. We developed a method to propagate these uncertainties in the scaling and imputation of TDP data to estimates of canopy transpiration and conductance using a state-space Jarvis-type conductance model in a hierarchical Bayesian framework. This presentation will focus on the impact of these uncertainties on estimates of water and carbon fluxes using 4CA and data from the Duke Free Air Carbon Enrichment (FACE) project, which incorporates both elevated carbon dioxide and soil nitrogen treatments. We will also address the response of canopy conductance to vapor pressure deficit, incident radiation and soil moisture, as well as the effect of treatment-related stand structure differences in scaling TDP measurements. Preliminary results indicate that in 2006, a year of normal precipitation (1127 mm), canopy transpiration increased in elevated carbon dioxide ~8% on a ground area basis. In 2007, a year with a pronounced drought (800 mm precipitation), this increase was only present in the combined carbon dioxide and fertilization treatment. The seasonal dynamics of water and carbon fluxes will be discussed in detail.

  10. IMPLEMENTATION OF AN URBAN CANOPY PARAMETERIZATION FOR FINE-SCALE SIMULATIONS

    EPA Science Inventory

    The Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) (Grell et al. 1994) has been modified to include an urban canopy parameterization (UCP) for fine-scale urban simulations ( 1 - km horizontal grid spacing ). The UCP accounts for dr...

  11. Photosynthesis and stomatal conductance related to reflectance on the canopy scale

    NASA Technical Reports Server (NTRS)

    Verma, S. B.; Sellers, P. J.; Walthall, C. L.; Hall, F. G.; Kim, J.; Goetz, S. J.

    1993-01-01

    Field measurements of carbon dioxide and water vapor fluxes were analyzed in conjunction with reflectances obtained from a helicopter-mounted Modular Multiband Radiometer at a grassland study site during the First International Satellite Land Surface Climatology Project Field Experiment. These measurements are representative of the canopy scale and were made over a range of meteorological and soil moisture conditions during different stages in the annual life cycle of the prairie vegetation, and thus provide a good basis for investigating hpotheses/relationships potentially useful in remote sensing applications. We tested the hypothesis (Sellers, 1987) that the simple ratio vegetation index should be near-linearly related to the derivatives of the unstressed canopy stomatal conductance and the unstressed canopy photosynthesis with respect to photosynthetically active radiation. Even though there is some scatter in our data, the results seem to support this hypothesis.

  12. Using Sensitivity Analysis and Fine-Scale Field Measurements to Understand How Canopy Interception Models Function

    NASA Astrophysics Data System (ADS)

    Siegert, C. M.; Levia, D. F., Jr.; Dowtin, A. L.; Hudson, S.; Linhoss, A.

    2015-12-01

    The capacity of the forest canopy to intercept precipitation and partition the remaining water into throughfall and stemflow largely influences the surface water budget in forested ecosystems. These processes are controlled by species-specific traits, canopy seasonality, and meteorological conditions. The complexity of these interacting factors at varying temporal and spatial scales can lead to errors in estimating canopy interception and reduce accuracy of derivative watershed hydrologic modeling efforts. To improve interception estimates, model calibration and validation must be assessed using long-term, fine-scale field measurements that capture the variability of all interacting factors. As such, field measurements of subcanopy hydrologic fluxes and meteorological conditions during discrete storm events were taken from 2007 to 2012 in a deciduous forest dominated by Fagus grandifolia and Liriodendron tulipifera in Fair Hill, Maryland, USA. Preliminary results suggest that many of the current interception models (e.g., Gash and Rutter-types) are driven primarily by evaporation terms. However, field measurements indicate that a large degree of variability in both throughfall and stemflow partitioning is derived from biophysical characteristics. For example, even within the small 12-hectare research catchment, differences in species composition induced by slight changes in elevation, coupled with slope orientation, resulted in sufficient canopy variability whereby throughfall fluxes were definitively different across small distances. Additionally, smaller trees were more efficient in generating stemflow, while species with smoother bark generated large quantities of stemflow under a variety of storm conditions—a mechanism that may further confound modeling efforts. To improve canopy interception estimates, model sensitivity analysis was used to determine the influence of current model parameters and how biophysical canopy characteristics may be further

  13. Plant Transpiration and its Sensitivity to Increasing Carbon Dioxide Concentration at Leaf, Canopy and Regional Scales

    NASA Astrophysics Data System (ADS)

    Zhan, Xiwu

    1995-01-01

    This thesis assembles simulation models for plant transpiration and uses these models to investigate the sensitivity of transpiration rates to the elevation of atmospheric CO_2 concentration at leaf, canopy and regional scales. The leaf transpiration model assembly (LTMA) simulates stomatal conductance, leaf net photosynthesis, leaf boundary layer conductance, mass and energy transfer, leaf energy balance. The stomatal conductance model and the leaf photosynthesis model are selected from two candidate stomatal models and four candidate biochemical photosynthesis models, based on the comparison of the model results with literature-surveyed observations. Integration of the LTMA for all the leaves within a plant canopy, with the modeled canopy structure, wind speed profile, radiation distribution, and soil surface fluxes, produces a canopy evapotranspiration model assembly (CEMA). Coupling the CEMA with an atmospheric boundary layer model, a larger model assembly (REMA) for simulating the evapotranspiration from a region covered with a homogeneous canopy is obtained. From the outputs of the LTMA, it is found that in response to a doubling of atmospheric CO_2 concentration the modeled leaf transpiration rate will be reduced by around -23.0% for C _3 plants and -26.6% for C4 plants. The simulated reduction in stomatal conductance resulting from the CO_2 doubling is 37.0% for C_3 plants and 37.7% for C_4 plants. The difference of the responses of stomatal conductance and leaf transpiration to CO_2 changes is found to be the results of the leaf boundary layer damping effect and the leaf temperature feedback effect. The CO_2 sensitivity of canopy evapotranspiration is found to be smaller still than that of leaf transpiration: the corresponding percentage changes with a CO_2 doubling are -15.7% and -16.1% respectively for C_3 and C_4 canopies. The cause is found to be the extension of the air within the canopy to the leaf boundary layers. The temperature feedback and the

  14. Energy budget closure and field scale estimation of canopy energy storage with increased and sustained turbulence

    NASA Astrophysics Data System (ADS)

    Anderson, R. G.; Wang, D.

    2012-12-01

    Eddy Covariance (EC) is widely used for direct, non-invasive observations of land-atmosphere energy and mass fluxes. However, EC observations of available energy fluxes are usually less than fluxes inferred from radiometer and soil heat flux observations; thus introducing additional uncertainty in using and interpreting EC flux measurements. We compare EC observations from two towers established over sugarcane (Saccharum officinarum L.) in Hawai'i, USA under similar cultivation, temperature, sunlight, and precipitation, but drastically different wind conditions due to orographic effects. At a daily scale, we find that energy closure for both towers occurs on days when the entire 24 hours has sufficient turbulence. At our windier site, this turbulence condition occurs over 60% of the time, which contributes to substantially better daily energy closure (~98%) than at the calmer site (~75%). At our windy site, we then invert the daily energy closure for continuously windy days to calculate canopy energy storage. At full canopy, peak daily canopy energy storage fluxes (200-400 Wm-2) are approximately an order of magnitude larger than soil heat flux (20-40 Wm-2). As a fraction of net radiation, canopy energy storage appears to vary seasonally and shows substantially greater variability than soil heat flux. The results illustrate the importance of sustained turbulence for accurate, direct measurement of land-atmosphere fluxes. As increasing number of EC towers are established in complex terrain, these results indicate the need for preliminary wind studies to optimize tower placement where orography enhances, rather than suppresses, turbulence.

  15. Sensitivity of the normalized difference vegetation index to subpixel canopy cover, soil albedo, and pixel scale

    NASA Technical Reports Server (NTRS)

    Jasinski, Michael F.

    1990-01-01

    An analytical framework is provided for examining the physically based behavior of the normalized difference vegetation index (NDVI) in terms of the variability in bulk subpixel landscape components and with respect to variations in pixel scales, within the context of the stochastic-geometric canopy reflectance model. Analysis focuses on regional scale variability in horizontal plant density and soil background reflectance distribution. Modeling is generalized to different plant geometries and solar angles through the use of the nondimensional solar-geometric similarity parameter. Results demonstrate that, for Poisson-distributed plants and for one deterministic distribution, NDVI increases with increasing subpixel fractional canopy amount, decreasing soil background reflectance, and increasing shadows, at least within the limitations of the geometric reflectance model. The NDVI of a pecan orchard and a juniper landscape is presented and discussed.

  16. The transpiration and the spectral response of non-irrigated Haloxylon ammodendron at canopy scale

    NASA Astrophysics Data System (ADS)

    Cao, Xiao-ming; Wang, Juan-le; Gao, Zhiqiang; Chen, Mao-si

    2012-10-01

    Transpiration, an essential component of surface evapotranspiration, is particularly important in the research of surface evapotranspiration in arid areas. The paper explores the spectral information of the arid vegetal evapotranspiration from a semi-empirical perspective by the measured data and the up-scaling method. The paper inverted the transpiration of Haloxylon ammodendronat at the canopy, pixel and regional scales in the southern edge of the Gurbantunggut desert in Xinjiang, China. The results are as follows: At the canopy scale, the optimal exponential model of the sap flow based on the hyperspectrum is Y = 3.65× SR(1580,1600) + 0.76, R2 = 0.72. At the pixel scale, there was a good linear relationship between the sap flow and the SR index, with a linear relationship of Y = 0.0787 X - 0.0724, R2 = 0.604. At the regional scale, based on the optimal exponential model and the EO-1 Hyperion remote sensing data, the transpiration of the study area was inverted. Comparing the results of the SEBAL and SEBS models, the errors of the simulation results were 12.66% and 11.68%. The paper made full use of the knowledge flow at different scales, bridging the scale difference in canopy and remote sensing images to avoid the information bottleneck in the up-scaling. However, there is much limit in the data acquirement, the endmembers determine, the temporal-spatial up-scaling, and the accuracy assessment to be improved in the future studies.

  17. Observations of leaf stomatal conductance at the canopy scale: An atmospheric modeling perspective

    NASA Astrophysics Data System (ADS)

    Avissar, Roni

    1993-03-01

    Plant stomata play a key role in the redistribution of energy received on vegetated land into sensible and latent heat. As a result, they have a considerable impact on the atmospheric planetary boundary layer, the hydrologic cycle, the climate, and the weather. Current parameterizations of the stomatal mechanism in state-of-the-art atmospheric models are based on empirical relations that are established at the leaf scale between stomatal conductance and environmental conditions. In order to evaluate these parameterizations, an experiment was carried out on a potato field in New Jersey during the summer of 1989. Stomatal conductances were measured within a small homogeneous area in the middle of the potato field and under a relatively broad range of atmospheric conditions. A large variability of stomatal conductances was observed. This variability, which was associated with the variability of micro-environmental and physiological conditions that is found even in a homogeneous canopy, cannot be simulated explicitly on the scale of a single agricultural field and, a fortiori, on the scale of atmospheric models. Furthermore, this variability could not be related to the environmental conditions measured at a height of 2 m above the plant canopy simultaneously with the conductances, reinforcing the concept of scale decoupling suggested by Jarvis and McNaughton (1986) and McNaughton and Jarvis (1991). Thus, for atmospheric modeling purposes, a parameterization of stomatal conductance at the canopy scale using external environmental forcing conditions seems more appropriate than a parameterization based on leaf-scale stomatal conductance, as currently adopted in state-of-the-art atmospheric models. The measured variability was characterized by a lognormal probability density function (pdf) that remained relatively stable during the entire measuring period. These observations support conclusions by McNaughton and Jarvis (1991) that, unlike current parameterizations, a

  18. Scaling up Semi-Arid Grassland Biochemical Content from the Leaf to the Canopy Level: Challenges and Opportunities

    PubMed Central

    He, Yuhong; Mui, Amy

    2010-01-01

    Remote sensing imagery is being used intensively to estimate the biochemical content of vegetation (e.g., chlorophyll, nitrogen, and lignin) at the leaf level. As a result of our need for vegetation biochemical information and our increasing ability to obtain canopy spectral data, a few techniques have been explored to scale leaf-level biochemical content to the canopy level for forests and crops. However, due to the contribution of non-green materials (i.e., standing dead litter, rock, and bare soil) from canopy spectra in semi-arid grasslands, it is difficult to obtain information about grassland biochemical content from remote sensing data at the canopy level. This paper summarizes available methods used to scale biochemical information from the leaf level to the canopy level and groups these methods into three categories: direct extrapolation, canopy-integrated approach, and inversion of physical models. As for semi-arid heterogeneous grasslands, we conclude that all methods are useful, but none are ideal. It is recommended that future research should explore a systematic upscaling framework which combines spatial pattern analysis, canopy-integrated approach, and modeling methods to retrieve vegetation biochemical content at the canopy level. PMID:22163513

  19. Plant chlorophyll fluorescence: active and passive measurements at canopy and leaf scales with different nitrogen treatments

    PubMed Central

    Cendrero-Mateo, M. Pilar; Moran, M. Susan; Papuga, Shirley A.; Thorp, K.R.; Alonso, L.; Moreno, J.; Ponce-Campos, G.; Rascher, U.; Wang, G.

    2016-01-01

    Most studies assessing chlorophyll fluorescence (ChlF) have examined leaf responses to environmental stress conditions using active techniques. Alternatively, passive techniques are able to measure ChlF at both leaf and canopy scales. However, the measurement principles of both techniques are different, and only a few datasets concerning the relationships between them are reported in the literature. In this study, we investigated the potential for interchanging ChlF measurements using active techniques with passive measurements at different temporal and spatial scales. The ultimate objective was to determine the limits within which active and passive techniques are comparable. The results presented in this study showed that active and passive measurements were highly correlated over the growing season across nitrogen treatments at both canopy and leaf-average scale. At the single-leaf scale, the seasonal relation between techniques was weaker, but still significant. The variability within single-leaf measurements was largely related to leaf heterogeneity associated with variations in CO2 assimilation and stomatal conductance, and less so to variations in leaf chlorophyll content, leaf size or measurement inputs (e.g. light reflected and emitted by the leaf and illumination conditions and leaf spectrum). This uncertainty was exacerbated when single-leaf analysis was limited to a particular day rather than the entire season. We concluded that daily measurements of active and passive ChlF at the single-leaf scale are not comparable. However, canopy and leaf-average active measurements can be used to better understand the daily and seasonal behaviour of passive ChlF measurements. In turn, this can be used to better estimate plant photosynthetic capacity and therefore to provide improved information for crop management. PMID:26482242

  20. Photosynthesis and stomatal conductance related to reflectance on the canopy scale

    SciTech Connect

    Verma, S.B.; Kim, J. ); Sellers, P.J.; Hall, F.G.; Goetz, S.J. ); Walthall, C.L. )

    1993-04-01

    Field measurements of carbon dioxide and water vapor fluxes were analyzed in conjunction with reflectances obtained from a helicopter-mounted Modular Multiband Radiometer (MMR) at a grassland study site during the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE). These measurements are representative of the canopy scale and were made over a range of meteorological and soil moisture conditions during different stages in the annual life cycle of the prairie vegetation, and thus provide a good basis for investigating hypotheses/relationships potentially useful in remote sensing applications. The authors tested the hypothesis (Sellers, 1987) that the simple ratio vegetation index (SR) should be near-linearly related to the derivatives of the unstressed canopy stomatal conductance (g[sub c]*) and the unstressed canopy photosynthesis (P[sub c]*) with respect to photosynthetically active radiation (PAR). Even though there is some scatter in the data, the results seem to support this hypothesis. Further investigation, however, is needed before such relationships can be employed in satellite remote sensing applications.

  1. Scaling up carbonyl sulfide (COS) fluxes from leaf and soil to the canopy

    NASA Astrophysics Data System (ADS)

    Yang, Fulin; Yakir, Dan

    2016-04-01

    Carbonyl sulfide (COS) with atmospheric concentrations around 500 ppt is an analog of CO2 which can potentially serve as powerful and much needed tracer of photosynthetic CO2 uptake, and global gross primary production (GPP). However, questions remain regarding the application of this approach due to uncertainties in the contributions of different ecosystem components to the canopy scale fluxes of COS. We used laser quantum cascade spectroscopy in combination with soil and branch chambers, and eddy covariance measurements of net ecosystem exchange fluxes of COS and CO2 (NEE) in citrus orchard during the driest summer month to test our ability to integrate the chamber measurements into the ecosystem fluxes. The results indicated that: 1) Soil fluxes showed clear gradient from continuous uptake under the trees in wet soil of up to -4 pmol m-2s-1 (CO2 emission of ~0.5 umol m-2s-1) to emission in dry hot and exposed soil between rows of trees of up to +3 pmol m-2s-1 (CO2 emission of ~11 umol m-2s-1). In all cases a clear correlation between fluxes and soil temperature was observed. 2) At the leaf scale, midday uptake was ~5.5 pmol m-2s-1 (CO2 uptake of ~1.8 umol m-2s-1). Some nighttime COS uptake was observed in the citrus leaves consistent with nocturnal leaf stomatal conductance. Leaf relative uptake (LRU) of COS vs. CO2 was not constant over the diurnal cycle, but showed exponential correlation with photosynthetically active radiation (PAR) during the daytime. 3) At the canopy scale mid-day summer flux reached -12.0 pmol m-2s-1 (NEE ~6 umol m-2s-1) with the diurnal patterns of COS fluxes following those of CO2 fluxes during the daytime, but with small COS uptake fluxes maintained also during the night when significant CO2 emission fluxes were observed. The canopy-scale fluxes always indicated COS uptake, irrespective of the soil emission effects. GPP estimates were consistent with conventional indirect estimates based on NEE and nocturnal measurements. Scaling up

  2. Scaling-law equilibria for calcium in canopy-type models of the solar chromosphere

    NASA Technical Reports Server (NTRS)

    Jones, H. P.

    1982-01-01

    Scaling laws for resonance line formation are used to obtain approximate excitation and ionization equilibria for a three-level model of singly ionized calcium. The method has been developed for and is applied to the study of magnetograph response in the 8542 A infrared triplet line to magnetostatic canopies which schematically model diffuse, nearly horizontal fields in the low solar chromosphere. For this application, the method is shown to be efficient and semi-quantitative, and the results indicate the type and range of effects on calcium-line radiation which result from reduced gas pressure inside the magnetic regions.

  3. Improving and validating 3D models for the leaf energy balance in canopy-scale problems with complex geometry

    NASA Astrophysics Data System (ADS)

    Bailey, B.; Stoll, R., II; Miller, N. E.; Pardyjak, E.; Mahaffee, W.

    2014-12-01

    Plants cover the majority of Earth's land surface, and thus play a critical role in the surface energy balance. Within individual plant communities, the leaf energy balance is a fundamental component of most biophysical processes. Absorbed radiation drives the energy balance and provides the means by which plants produce food. Available energy is partitioned into sensible and latent heat fluxes to determine surface temperature, which strongly influences rates of metabolic activity and growth. The energy balance of an individual leaf is coupled with other leaves in the community through longwave radiation emission and advection through the air. This complex coupling can make scaling models from leaves to whole-canopies difficult, specifically in canopies with complex, heterogeneous geometries. We present a new three-dimensional canopy model that simultaneously resolves sub-tree to whole-canopy scales. The model provides spatially explicit predictions of net radiation exchange, boundary-layer and stomatal conductances, evapotranspiration rates, and ultimately leaf surface temperature. The radiation model includes complex physics such as anisotropic emission and scattering. Radiation calculations are accelerated by leveraging graphics processing unit (GPU) technology, which allows canopy-scale problems to be performed on a standard desktop workstation. Since validating the three-dimensional distribution of leaf temperature can be extremely challenging, we used several independent measurement techniques to quantify errors in measured and modeled values. When compared with measured leaf temperatures, the model gave a mean error of about 2°C, which was close to the estimated measurement uncertainty.

  4. 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.

  5. Canopy-scale biophysical controls of transpiration and evaporation in the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Mallick, Kaniska; Trebs, Ivonne; Boegh, Eva; Giustarini, Laura; Schlerf, Martin; Drewry, Darren T.; Hoffmann, Lucien; von Randow, Celso; Kruijt, Bart; Araùjo, Alessandro; Saleska, Scott; Ehleringer, James R.; Domingues, Tomas F.; Ometto, Jean Pierre H. B.; Nobre, Antonio D.; Leal de Moraes, Osvaldo Luiz; Hayek, Matthew; Munger, J. William; Wofsy, Steven C.

    2016-10-01

    Canopy and aerodynamic conductances (gC and gA) are two of the key land surface biophysical variables that control the land surface response of land surface schemes in climate models. Their representation is crucial for predicting transpiration (λET) and evaporation (λEE) flux components of the terrestrial latent heat flux (λE), which has important implications for global climate change and water resource management. By physical integration of radiometric surface temperature (TR) into an integrated framework of the Penman-Monteith and Shuttleworth-Wallace models, we present a novel approach to directly quantify the canopy-scale biophysical controls on λET and λEE over multiple plant functional types (PFTs) in the Amazon Basin. Combining data from six LBA (Large-scale Biosphere-Atmosphere Experiment in Amazonia) eddy covariance tower sites and a TR-driven physically based modeling approach, we identified the canopy-scale feedback-response mechanism between gC, λET, and atmospheric vapor pressure deficit (DA), without using any leaf-scale empirical parameterizations for the modeling. The TR-based model shows minor biophysical control on λET during the wet (rainy) seasons where λET becomes predominantly radiation driven and net radiation (RN) determines 75 to 80 % of the variances of λET. However, biophysical control on λET is dramatically increased during the dry seasons, and particularly the 2005 drought year, explaining 50 to 65 % of the variances of λET, and indicates λET to be substantially soil moisture driven during the rainfall deficit phase. Despite substantial differences in gA between forests and pastures, very similar canopy-atmosphere "coupling" was found in these two biomes due to soil moisture-induced decrease in gC in the pasture. This revealed the pragmatic aspect of the TR-driven model behavior that exhibits a high sensitivity of gC to per unit change in wetness as opposed to gA that is marginally sensitive to surface wetness variability

  6. Greenness indices from digital cameras predict the timing and seasonal dynamics of canopy-scale photosynthesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The proliferation of tower-mounted cameras co-located with eddy covariance instrumentation provides a novel opportunity to better understand the relationship between canopy phenology and the seasonality of canopy photosynthesis. In this paper, we describe the abilities and limitations of webcams to ...

  7. Fine-scale, multidimensional spatial patterns of forest canopy structure derived from remotely sensed and simulated datasets

    NASA Astrophysics Data System (ADS)

    Frazer, Gordon Wilson

    Forests are not simply storehouses of timber or wood fibre for human consumption and economic development. They represent structurally and ecologically rich habitat for an estimated 40 percent of the earth's extant species, and form the functional interface between the biosphere and atmosphere for some 27 percent of the earth's terrestrial surface. Forests, therefore, play a vital role in the maintenance of biodiversity and the regulation of local to global scale ecosystem processes and functions. Present strategies for conserving biodiversity in managed forests are based on the notion that maintaining the full range of structural conditions historically present in natural forests is the best approach for assuring the long-term persistence of a broad range of native species. The overarching goal of this dissertation is to contribute to the development of novel forest measurements that are relevant to organisms and ecosystems, and much needed by forest scientists and managers to recognize and retain the key elements and patterns of forest structure that are crucial for the conservation of forest biodiversity. This study focuses explicitly on fine-spatial-scale, multidimensional patterns of forest canopy structure based on the assumption that the 'canopy' is the primary focal site of complex interactions between vegetation and the physical environment. Two disparate remote sensing technologies---ground-based hemispherical (fisheye) canopy photography and airborne discrete-return LiDAR---are employed to characterize angular, vertical, and horizontal patterns of forest canopy structure. A quantitative technique is developed for precise measurements of gap fraction (P), element clumping (O), mean projection coefficient (G), and leaf area index (L) from sequences (sets) of black and white pixels extracted at specific view angles in digital fisheye photos. Results are compared with three other leading techniques and validated using well-documented simulated and real

  8. Integrating canopy and large-scale effects in the convective boundary-layer dynamics during the CHATS experiment

    NASA Astrophysics Data System (ADS)

    Shapkalijevski, Metodija M.; Ouwersloot, Huug G.; Moene, Arnold F.; Vilà-Guerau de Arrellano, Jordi

    2017-02-01

    By characterizing the dynamics of a convective boundary layer above a relatively sparse and uniform orchard canopy, we investigated the impact of the roughness-sublayer (RSL) representation on the predicted diurnal variability of surface fluxes and state variables. Our approach combined numerical experiments, using an atmospheric mixed-layer model including a land-surface-vegetation representation, and measurements from the Canopy Horizontal Array Turbulence Study (CHATS) field experiment near Dixon, California. The RSL is parameterized using an additional factor in the standard Monin-Obukhov similarity theory flux-profile relationships that takes into account the canopy influence on the atmospheric flow. We selected a representative case characterized by southerly wind conditions to ensure well-developed RSL over the orchard canopy. We then investigated the sensitivity of the diurnal variability of the boundary-layer dynamics to the changes in the RSL key scales, the canopy adjustment length scale, Lc, and the β = u*/|U| ratio at the top of the canopy due to their stability and dependence on canopy structure. We found that the inclusion of the RSL parameterization resulted in improved prediction of the diurnal evolution of the near-surface mean quantities (e.g. up to 50 % for the wind velocity) and transfer (drag) coefficients. We found relatively insignificant effects on the modelled surface fluxes (e.g. up to 5 % for the friction velocity, while 3 % for the sensible and latent heat), which is due to the compensating effect between the mean gradients and the drag coefficients, both of which are largely affected by the RSL parameterization. When varying Lc (from 10 to 20 m) and β (from 0.25 to 0.4 m), based on observational evidence, the predicted friction velocity is found to vary by up to 25 % and the modelled surface-energy fluxes (sensible heat, SH, and latent heat of evaporation, LE) vary up to 2 and 9 %. Consequently, the boundary-layer height varies up to

  9. Three-dimensional estimates of tree canopies: Scaling from high-resolution UAV data to satellite observations

    NASA Astrophysics Data System (ADS)

    Sankey, T.; Donald, J.; McVay, J.

    2015-12-01

    High resolution remote sensing images and datasets are typically acquired at a large cost, which poses big a challenge for many scientists. Northern Arizona University recently acquired a custom-engineered, cutting-edge UAV and we can now generate our own images with the instrument. The UAV has a unique capability to carry a large payload including a hyperspectral sensor, which images the Earth surface in over 350 spectral bands at 5 cm resolution, and a lidar scanner, which images the land surface and vegetation in 3-dimensions. Both sensors represent the newest available technology with very high resolution, precision, and accuracy. Using the UAV sensors, we are monitoring the effects of regional forest restoration treatment efforts. Individual tree canopy width and height are measured in the field and via the UAV sensors. The high-resolution UAV images are then used to segment individual tree canopies and to derive 3-dimensional estimates. The UAV image-derived variables are then correlated to the field-based measurements and scaled to satellite-derived tree canopy measurements. The relationships between the field-based and UAV-derived estimates are then extrapolated to a larger area to scale the tree canopy dimensions and to estimate tree density within restored and control forest sites.

  10. Global simulation of canopy scale sun-induced chlorophyll fluorescence with a 3 dimensional radiative transfer model

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Yang, W.; Ichii, K.

    2015-12-01

    Global simulation of canopy scale sun-induced chlorophyll fluorescence with a 3 dimensional radiative transfer modelHideki Kobayashi, Wei Yang, and Kazuhito IchiiDepartment of Environmental Geochemical Cycle Research, Japan Agency for Marine-Earth Science and Technology3173-25, Showa-machi, Kanazawa-ku, Yokohama, Japan.Plant canopy scale sun-induced chlorophyll fluorescence (SIF) can be observed from satellites, such as Greenhouse gases Observation Satellite (GOSAT), Orbiting Carbon Observatory-2 (OCO-2), and Global Ozone Monitoring Experiment-2 (GOME-2), using Fraunhofer lines in the near infrared spectral domain [1]. SIF is used to infer photosynthetic capacity of plant canopy [2]. However, it is not well understoond how the leaf-level SIF emission contributes to the top of canopy directional SIF because SIFs observed by the satellites use the near infrared spectral domain where the multiple scatterings among leaves are not negligible. It is necessary to quantify the fraction of emission for each satellite observation angle. Absorbed photosynthetically active radiation of sunlit leaves are 100 times higher than that of shaded leaves. Thus, contribution of sunlit and shaded leaves to canopy scale directional SIF emission should also be quantified. Here, we show the results of global simulation of SIF using a 3 dimensional radiative transfer simulation with MODIS atmospheric (aerosol optical thickness) and land (land cover and leaf area index) products and a forest landscape data sets prepared for each land cover category. The results are compared with satellite-based SIF (e.g. GOME-2) and the gross primary production empirically estimated by FLUXNET and remote sensing data.

  11. Continental-scale ICESat canopy height modelling sensitivity and random forest simulations in Australia and Canada

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The Geoscience Laser Altimeter System (GLAS), previously onboard the Ice, Cloud, and land Elevation Satellite (ICESat) uniquely offers near global waveform LiDAR coverage, however, data quality are subject to system, temporal, and spatial issues. These subtleties are investigated here with respect to canopy height comparisons with 3 airborne LiDAR sites in Australia. Optimal GLAS results were obtained from high energy laser transmissions from laser 3 during leaf-on conditions; GLAS data best corresponded with 95th percentile heights from an all return airborne LiDAR point cloud. In addition, best GLAS results were obtained over relatively open canopies, where prominent ground returns can be retrieved. Optimized GLAS data within Australian forests were employed as canopy height observations, and related to 6 predictor variables (landcover, cover fraction, elevation, slope, soils, and species) by random forest (RF) models. Fifty seven RF models were trained, varying by binomial combinations of predictor data, from 2 to 6 inputs. Trained models were separately utilized to predict Australia wide canopy heights; RF canopy height outputs were validated against spatially concurrent airborne LiDAR 95th percentile canopy heights from an all return point cloud for 10 sites, encompassing multiple ecosystems. The best RF output was obtained from predictor data inputs: landcover, cover fraction, elevation soils, and species, yielding a RMSE=7.98 m, and R2=0.97. Results indicate inherent issues (noted in existing literature) in GLAS observations that propagate through RF algorithms, manifested as canopy height underestimations for taller vegetation (>45 m). To extend this research to the Canadian boreal forest context, research is also targeting canopy height model development in the Northwest Territories, allowing investigations of time-variant phenology and landcover sensitivity due to wetland extent and growth, snow cover and other land cover changes common within boreal

  12. Rice evapotranspiration at the field and canopy scales under water-saving irrigation

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyin; Xu, Junzeng; Yang, Shihong; Zhang, Jiangang

    2017-02-01

    Evapotranspiration (ET) is an important process of land surface water and thermal cycling, with large temporal and spatial variability. To reveal the effect of water-saving irrigation (WSI) on rice ET at different spatial scales and understand the cross spatial scale difference, rice ET under WSI condition at canopy (ETCML) and field scale (ETEC) were measured simultaneously by mini-lysimeter and eddy covariance (EC) in the rice season of 2014. To overcome the shortage of energy balance deficit by EC system, and evaluate the influence of energy balance closure degree on ETEC, ETEC was corrected as ET_{EC}^{*} by energy balance closure correction according to the evaporative fraction. Seasonal average daily ETEC, ET_{EC}^{*} and ETCML of rice under WSI practice were estimated as 3.12, 4.03 and 4.35 mm day-1, smaller than the values reported in flooded paddy fields. Daily ETEC, ET_{EC}^{*} and ETCML varied in a similar trends and reached the maximum in late tillering, then decreased along with the crop growth in late season. The value of ETEC was much lower than ETCML, and was frequently 1-2 h lagged behind ETCML. It indicated that the energy balance deficit resulted in underestimation of crop ET by EC system. The corrected value of ET_{EC}^{*} matched ETCML much better than ETEC, with a smaller RMSE (0.086 mm h-1) and higher R 2 (0.843) and IOA (0.961). The time lapse between ET_{EC}^{*} and ETCML was mostly shortened to less than 0.5 h. The multiple stepwise regression analysis indicated that net radiation (R n) is the dominant factor for rice ET, and soil moisture (θ) is another significant factor (p < 0.01) in WSI rice fields. The difference between ETCML and ET_{EC}^{*} (ET_{CML} - ET_{EC^{*} ) were significantly (p < 0.05) correlated with R n, air temperature (T a), and air vapor pressure deficit (D), and its partial correlation coefficients to R n and T a were slightly greater than D. Thus, R n, T a and D are important variables for understanding the spatial

  13. Fine-Scale Genetic Structure of Monilinia fructicola During Brown Rot Epidemics Within Individual Peach Tree Canopies.

    PubMed

    Everhart, S E; Scherm, H

    2015-04-01

    The purpose of this study was to determine the fine-scale genetic structure of populations of the brown rot pathogen Monilinia fructicola within individual peach tree canopies to better understand within-tree plant pathogen diversity and to complement previous work on spatiotemporal development of brown rot disease at the canopy level. Across 3 years in a total of six trees, we monitored disease development, collected isolates from every M. fructicola symptom during the course of the season, and created high-resolution three-dimensional maps of all symptom and isolate locations within individual canopies using an electromagnetic digitizer. Each canopy population (65 to 173 isolates per tree) was characterized using a set of 13 microsatellite markers and analyzed for evidence of spatial genetic autocorrelation among isolates during the epidemic phase of the disease. Results showed high genetic diversity (average uh=0.529) and high genotypic diversity (average D=0.928) within canopies. The percentage of unique multilocus genotypes within trees was greater for blossom blight isolates (78.2%) than for fruit rot isolates (51.3%), indicating a greater contribution of clonal reproduction during the preharvest epidemic. For fruit rot isolates, between 54.2 and 81.7% of isolates were contained in one to four dominant clonal genotypes per tree having at least 10 members. All six fruit rot populations showed positive and significant spatial genetic autocorrelation for distance classes between 0.37 and 1.48 m. Despite high levels of within-tree pathogen diversity, the contribution of locally available inoculum combined with short-distance dispersal is likely the main factor generating clonal population foci and associated spatial genetic clustering within trees.

  14. Developing a regional canopy fuels assessment strategy using multi-scale lidar

    USGS Publications Warehouse

    Peterson, Birgit E.; Nelson, Kurtis

    2011-01-01

    Accurate assessments of canopy fuels are needed by fire scientists to understand fire behavior and to predict future fire occurrence. A key descriptor for canopy fuels is canopy bulk density (CBD). CBD is closely linked to the structure of the canopy; therefore, lidar measurements are particularly well suited to assessments of CBD. LANDFIRE scientists are exploring methods to integrate airborne and spaceborne lidar datasets into a national mapping effort. In this study, airborne lidar, spaceborne lidar, and field data are used to map CBD in the Yukon Flats Ecoregion, with the airborne lidar serving as a bridge between the field data and the spaceborne observations. The field-based CBD was positively correlated with airborne lidar observations (R2=0.78). Mapped values of CBD using the airborne lidar dataset were significantly correlated with spaceborne lidar observations when analyzed by forest type (R2=0.62, evergreen and R2=0.71, mixed). Though continued research is necessary to validate these results, they do support the feasibility of airborne and, most importantly, spaceborne lidar data for canopy fuels assessment.

  15. Landscape-Scale Canopy Complexity in and Near Braulio Carillo National Park, Costa Rica

    NASA Technical Reports Server (NTRS)

    Knox, Robert G.; Blair, J. B.; Weishampel, J. F.; Clark, D. B.; Hofton, M. A.; Dubayah, R.

    1999-01-01

    Using medium-large footprint lidar sampling of approximately 500 square km of Costa Rica, we assessed the vertical and horizontal complexity of a forest-dominated tropical landscape. As expected, vertical extents of structure and canopy heights estimated from lidar waveforms were smaller in high elevation forests than in forests at lower elevations. In areas of the park and long-protected areas of La Selva Biological Station, forests typically had more consistent ratios of median height to total height than areas with other types of recent land use. Areas outside the park exhibited both stronger and weaker spatial correlations in canopy properties than most areas within the park. We also simulated the effects of these differences on data products gridded from lidar transects, like those produced by the Vegetation Canopy Lidar (VCL) Mission.

  16. Deconvolution of pigment and physiologically related photochemical reflectance index variability at the canopy scale over an entire growing season.

    PubMed

    Hmimina, G; Merlier, E; Dufrêne, E; Soudani, K

    2015-08-01

    The sensitivity of the photochemical reflectance index (PRI) to leaf pigmentation and its impacts on its potential as a proxy for light-use efficiency (LUE) have recently been shown to be problematic at the leaf scale. Most leaf-to-leaf and seasonal variability can be explained by such a confounding effect. This study relies on the analysis of PRI light curves that were generated at the canopy scale under natural conditions to derive a precise deconvolution of pigment-related and physiologically related variability in the PRI. These sources of variability were explained by measured or estimated physiologically relevant variables, such as soil water content, that can be used as indicators of water availability and canopy chlorophyll content. The PRI mainly reflected the variability in the pigment content of the canopy. However, the corrected PRI, which was obtained by subtracting the pigment-related seasonal variability from the PRI measurement, was highly correlated with the upscaled LUE measurements. Moreover, the sensitivity of the PRI to the leaf pigment content may mask the PRI versus LUE relationship or result in an artificial relationship that reflects the relationship of chlorophyll versus LUE, depending on the species phenology.

  17. Monitoring regional patterns of canopy-scale phenology with a network of digitial webcams

    NASA Astrophysics Data System (ADS)

    Richardson, A. D.; Braswell, B. H.; Hollinger, D. Y.; Jenkins, J. P.

    2007-12-01

    Understanding relationships between canopy structure and the seasonal dynamics of photosynthetic uptake of CO2 by forest canopies requires improved knowledge of canopy phenology at eddy covariance flux tower sites. We investigated whether digital webcam images could be used to monitor the trajectories of spring green-up and autumn senescence in a deciduous northern hardwood forest. A standard, commercially available webcam was mounted at the top of the eddy covariance tower at the Bartlett AmeriFlux site. Images were collected each day around mid-day. Red, green and blue color channel brightness data for a 640 x 100 pixel region-of-interest were extracted from each image. We evaluated the green-up signal extracted from webcam images against changes in fAPAR (the fraction of incident photosynthetically active radiation that is absorbed by the canopy), broadband NDVI, and Amax (the light-saturated rate of canopy photosynthesis, inferred from eddy flux measurements). The relative brightness of the green channel (green %) was relatively stable through the winter months. A steady rising trend in green % began around day 120 and continued through day 160, at which point a stable plateau was reached. The relative brightness of the blue channel (blue %) also responded to spring green-up, although there was more day-to-day variation in the signal because blue % was more sensitive to changes in the quality (spectral distribution) of incident radiation. Seasonal changes in blue % were most similar to those in fAPAR and broadband NDVI, whereas changes in green % proceeded more slowly, and were drawn out over a longer period of time. Changes in Amax lagged green-up by at least a week. The onset of autumn senescence was marked by a decrease in green %, which preceded a spike in red % when autumn coloration peaked at day 270. A decrease in red % was observed over the next 30 days (through day 300) as senescence progressed and the deciduous canopy was shed. We conclude that

  18. Tropical forest phenology and carbon dioxide fluxes: a tower-mounted camera system for integrating canopy-scale phenology with seasonality of ecosystem-scale photosynthesis

    NASA Astrophysics Data System (ADS)

    Wu, J.; Restrepo-Coupe, N.; Hayek, M.; Marostica, S.; Stark, S.; Wiedemam, K.; Woodcock, T.; da Silva, R.; Nelson, B. W.; Huete, A. R.; Saleska, S. R.

    2012-12-01

    Seasonal and interanual pattern of leaf development and metabolism is a central topic of global change ecology and evolutionary biology. However, the seasonality of leaf development in tropical forests remains poorly understood due to relatively low variation in climate, the extremely high biodiversity of tropical biomes, and limited ability to bridge the gap between observations of individual plants and of large-scale patterns via remote sensing techniques. Indeed, most vegetation models assume that evergreen tropical forest canopies are aseasonal. In this study, we aim first, to demonstrate the feasibility of using a near-surface (tower mounted) remote sensing camera to understand the phenology of an evergreen tropical forest canopy (Tapajos National Forest or TNF site, Santarem, Para, Brazil), and second, to link camera-observed phonological patterns to the underlying metabolic processes of tropical vegetation. Two continuous years (2010-2011) of images from a tower mounted 3-channel (red, green, and near-infrared) TetraCAM ADC camera were analyzed for this study. A new approach based on classical image classification, which divided images into three components (leaves, bare wood, and open space), was developed to extract the seasonality of leaf development. This camera based phenology information was combined with tower based eddy covariance measurements at the same site to quantify the effect of canopy-scale phenology on ecosystem metabolism. Preliminary error analysis showed high agreement (R2=96.7%, n=24 images in 2010) between automatic classification and manual user classification of canopy components (leaf, bare wood, gap) in images, suggesting good accuracy from the image processing algorithm.. The seasonal pattern of the observed leaf fraction derived from camera images also compared well (R2=0.63, p=0.03, N=12 observations in 2010) with monthly ground-based LiDAR surveys of the integrated total canopy LAI. In addition, the seasonal pattern of camera

  19. Greenness indices from digital cameras predict the timing and seasonal dynamics of canopy-scale photosynthesis.

    PubMed

    Toomey, Michael; Friedl, Mark A; Frolking, Steve; Hufkens, Koen; Klosterman, Stephen; Sonnentag, Oliver; Baldocchi, Dennis D; Bernacchi, Carl J; Biraud, Sebastien C; Bohrer, Gil; Brzostek, Edward; Burns, Sean P; Coursolle, Carole; Hollinger, David Y; Margolis, Hank A; Mccaughey, Harry; Monson, Russell K; Munger, J William; Pallardy, Stephen; Phillips, Richard P; Torn, Margaret S; Wharton, Sonia; Zeri, Marcelo; And, Andrew D; Richardson, Andrew D

    2015-01-01

    The proliferation of digital cameras co-located with eddy covariance instrumentation provides new opportunities to better understand the relationship between canopy phenology and the seasonality of canopy photosynthesis. In this paper we analyze the abilities and limitations of canopy color metrics measured by digital repeat photography to track seasonal canopy development and photosynthesis, determine phenological transition dates, and estimate intra-annual and interannual variability in canopy photosynthesis. We used 59 site-years of camera imagery and net ecosystem exchange measurements from 17 towers spanning three plant functional types (deciduous broadleaf forest, evergreen needleleaf forest, and grassland/crops) to derive color indices and estimate gross primary productivity (GPP). GPP was strongly correlated with greenness derived from camera imagery in all three plant functional types. Specifically, the beginning of the photosynthetic period in deciduous broadleaf forest and grassland/crops and the end of the photosynthetic period in grassland/crops were both correlated with changes in greenness; changes in redness were correlated with the end of the photosynthetic period in deciduous broadleaf forest. However, it was not possible to accurately identify the beginning or ending of the photosynthetic period using camera greenness in evergreen needleleaf forest. At deciduous broadleaf sites, anomalies in integrated greenness and total GPP were significantly correlated up to 60 days after the mean onset date for the start of spring. More generally, results from this work demonstrate that digital repeat photography can be used to quantify both the duration of the photosynthetically active period as well as total GPP in deciduous broadleaf forest and grassland/crops, but that new and different approaches are required before comparable results can be achieved in evergreen needleleaf forest.

  20. Incorporating remotely sensed tree canopy cover data into broad scale assessments of wildlife habitat distribution and conservation

    NASA Astrophysics Data System (ADS)

    Martinuzzi, Sebastián; Vierling, Lee A.; Gould, William A.; Vierling, Kerri T.; Hudak, Andrew T.

    2009-12-01

    Remote sensing provides critical information for broad scale assessments of wildlife habitat distribution and conservation. However, such efforts have been typically unable to incorporate information about vegetation structure, a variable important for explaining the distribution of many wildlife species. We evaluated the consequences of incorporating remotely sensed information about horizontal vegetation structure into current assessments of wildlife habitat distribution and conservation. For this, we integrated the new NLCD tree canopy cover product into the US GAP Analysis database, using avian species and the finished Idaho GAP Analysis as a case study. We found: (1) a 15-68% decrease in the extent of the predicted habitat for avian species associated with specific tree canopy conditions, (2) a marked decrease in the species richness values predicted at the Landsat pixel scale, but not at coarser scales, (3) a modified distribution of biodiversity hotspots, and (4) surprising results in conservation assessment: despite the strong changes in the species predicted habitats, their distribution in relation to the reserves network remained the same. This study highlights the value of area wide vegetation structure data for refined biodiversity and conservation analyses. We discuss further opportunities and limitations for the use of the NLCD data in wildlife habitat studies.

  1. A visible band index for remote sensing leaf chlorophyll content at the canopy scale

    NASA Astrophysics Data System (ADS)

    Hunt, E. Raymond; Doraiswamy, Paul C.; McMurtrey, James E.; Daughtry, Craig S. T.; Perry, Eileen M.; Akhmedov, Bakhyt

    2013-04-01

    Leaf chlorophyll content is an important variable for agricultural remote sensing because of its close relationship to leaf nitrogen content. The triangular greenness index (TGI) was developed based on the area of a triangle surrounding the spectral features of chlorophyll with points at (670 nm, R670), (550 nm, R550), and (480 nm, R480), where Rλ is the spectral reflectance at wavelengths of 670, 550 and 480, respectively. The equation is TGI = -0.5[(670 - 480)(R670 - R550) - (670 - 550)(R670 - R480)]. In 1999, investigators funded by NASA's Earth Observations Commercialization and Applications Program collaborated on a nitrogen fertilization experiment with irrigated maize in Nebraska. Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data and Landsat 5 Thematic Mapper (TM) data were acquired along with leaf chlorophyll meter and other data on three dates in July during late vegetative growth and early reproductive growth. TGI was consistently correlated with plot-averaged chlorophyll-meter values at the spectral resolutions of AVIRIS, Landsat TM, and digital cameras. Simulations using the Scattering by Arbitrarily Inclined Leaves (SAIL) canopy model indicate an interaction among TGI, leaf area index (LAI) and soil type at low crop LAI, whereas at high LAI and canopy closure, TGI was only affected by leaf chlorophyll content. Therefore, TGI may be the best spectral index to detect crop nitrogen requirements with low-cost digital cameras mounted on low-altitude airborne platforms.

  2. Improved Retrieval of Chlorophyll and Carotenoids Contents at the Canopy Scale Using Hyperspectral CAO Data and PROSAIL Model

    NASA Astrophysics Data System (ADS)

    Feret, J.; Asner, G. P.; Jacquemoud, S.; François, C.

    2008-12-01

    The sustainability of biodiversity requires frequent and spatially detailed assessment of species number and distribution, among other information. Remote sensing is one of the most promising way to achieve this environmental management due to reasonable cost and accuracy. However, the use of airborne and spaceborne data remains challenging: sensors must combine the appropriate spatial and spectral resolutions to retrieve pertinent environmental parameters that will permit identification of specific properties of organisms present in an ecosystem. Leaf area index (LAI), canopy structure and pigment composition of vegetation are valuable information to study ecosystem dynamics and distinguish between many species. Chlorophyll and carotenoid pigments are of particular interest because they are involved in photosynthesis, but until now, remote sensing was unable to assess these pigments separately and accurately. Some advances have been made recently with the separation of these pigments in PROSPECT-5, a radiative transfer model that simulates leaf spectral reflectance and transmittance at 1 nm resolution. PROSAIL, the joint vegetation canopy reflectance model associating PROSPECT-5 with 4SAIL, the latest version of the SAIL model, was first run in direct mode to design vegetation indices sensitive to leaf pigments. Subsequently, we retrieved chlorophyll and carotenoid contents using PROSAIL with CAO (Carnegie Airborne Observatory) data acquired in Hawaii. The CAO, an imaging spectrometer coupled with a 3-D laser scanner, has already demonstrated its ability to manage biodiversity in various ecosystems like tropical rainforests or savannah. Its performance make it particularly adapted to assess vegetation structure, biochemistry, and then fluxes. The first results obtained when processing CAO images with PROSAIL are promising in terms of chlorophyll and carotenoid retrieval at the canopy scale. They show that our approach can provide original information on vegetation

  3. DISTRIBUTION OF ALGAL EPIPHYTES ACROSS ENVIRONMENTAL GRADIENTS AT DIFFERENT SCALES: INTERTIDAL ELEVATION, HOST CANOPIES, AND HOST FRONDS(1).

    PubMed

    Longtin, Caroline M; Scrosati, Ricardo A; Whalen, Gillian B; Garbary, David J

    2009-08-01

    Understanding epiphyte distribution in coastal communities is important because these organisms affect many others directly or indirectly. Yet, their distribution has been considerably less studied than that of their hosts and other primary-space holders. Identifying major sources of variation in epiphyte abundance is thus still a need. Environmental gradients help predict species distribution and are pervasive on marine shores. In this study, we test the notion that environmental gradients across intertidal elevation, throughout host canopies, and along host fronds explain a large variation in the abundance of sympatric epiphytes. Our model system was the assemblage of Ascophyllum nodosum (L.) Le Jol. and its epiphytes Vertebrata lanosa (L.) T. A. Chr. [= Polysiphonia lanosa (L.) Tandy], Elachista fucicola (Velley) Aresch., and Pylaiella littoralis (L.) Kjellm. On the coast of Nova Scotia (Canada), we found evidence of a spatial segregation among these species at almost all scales. While the red epiphyte V. lanosa was more common at high- and midintertidal elevations (peaking at midelevations) and on middle segments of host fronds, the brown epiphytes E. fucicola and P. littoralis were more common at low elevations and restricted to distal segments of host fronds. Canopy habitat affected abundance only for V. lanosa, which was more common within the host canopy than on its periphery at midelevations. Since the studied gradients are related to predictable changes in abiotic factors, the identification of likely causes behind the observed patterns was facilitated. Our study ends by proposing abiotic and biotic factors that deserve priority in the experimental testing of the forces structuring this assemblage.

  4. Explaining the variability of the photochemical reflectance index (PRI) at the canopy-scale: Disentangling the effects of phenological and physiological changes.

    PubMed

    Merlier, Elodie; Hmimina, Gabriel; Dufrêne, Eric; Soudani, Kamel

    2015-10-01

    Assessing photosynthesis rates at the ecosystem scale and over large regions is important for tracking the global carbon cycle and remote sensing has provided new and useful approaches for performing this assessment. The photochemical reflectance index (PRI) is a good estimator of short-term light-use efficiency (LUE) at the leaf scale; however, confounding factors appear at larger temporal and spatial scales. In this study, canopy-scale PRI variability was investigated for three species (Fagus sylvatica L., Quercus robur L. and Pinus sylvestris L.) growing under contrasting soil moisture conditions. Throughout the growing season, no significant differences in chlorophyll content and in violaxanthin, antheraxanthin and zeaxanthin were found between species or treatments. The daily PRI vs PAR (photosynthetically active radiation) relationships were determined using continuous measurements obtained at high frequency throughout the entire growing season, from early spring budburst to later autumn senescence, and were used to deconvolute the physiological PRI variability related to LUE variations due to phenological variability and related to temporal changes in the biochemical and structural canopy attributes. The PRI vs PAR relationship is used to show that the canopy-scale PRI measured at low radiation depends on the chlorophyll content of the canopy. The range of PRI variations at an intra-daily scale and the dynamics of the xanthophyll pool do not vary between days, which suggests that the PRI responds to a xanthophyll ratio. The PAR values at PRI saturation are mainly related to the canopy chlorophyll content during budburst and senescence and to the soil moisture content when the chlorophyll content is no longer a limiting factor. This parameter is significantly lower in the oak species that experience less stress from variations in soil moisture and is species dependant. These results provide new insights regarding the analysis and the meaning of PRI

  5. Fine-spatial scale predictions of understory species using climate- and LiDAR-derived terrain and canopy metrics

    NASA Astrophysics Data System (ADS)

    Nijland, Wiebe; Nielsen, Scott E.; Coops, Nicholas C.; Wulder, Michael A.; Stenhouse, Gordon B.

    2014-01-01

    Food and habitat resources are critical components of wildlife management and conservation efforts. The grizzly bear (Ursus arctos) has diverse diets and habitat requirements particularly for understory plant species, which are impacted by human developments and forest management activities. We use light detection and ranging (LiDAR) data to predict the occurrence of 14 understory plant species relevant to bear forage and compare our predictions with more conventional climate- and land cover-based models. We use boosted regression trees to model each of the 14 understory species across 4435 km2 using occurrence (presence-absence) data from 1941 field plots. Three sets of models were fitted: climate only, climate and basic land and forest covers from Landsat 30-m imagery, and a climate- and LiDAR-derived model describing both the terrain and forest canopy. Resulting model accuracies varied widely among species. Overall, 8 of 14 species models were improved by including the LiDAR-derived variables. For climate-only models, mean annual precipitation and frost-free periods were the most important variables. With inclusion of LiDAR-derived attributes, depth-to-water table, terrain-intercepted annual radiation, and elevation were most often selected. This suggests that fine-scale terrain conditions affect the distribution of the studied species more than canopy conditions.

  6. Chlorophyll content in eucalypt vegetation at the leaf and canopy scales as derived from high resolution spectral data.

    PubMed

    Coops, Nicholas C; Stone, Christine; Culvenor, Darius S; Chisholm, Laurie A; Merton, Ray N

    2003-01-01

    The physiological status of forest canopy foliage is influenced by a range of factors that affect leaf pigment content and function. Recently, several indices have been developed from remotely sensed data that attempt to provide robust estimates of leaf chlorophyll content. These indices have been developed from either hand-held spectroradiometer spectra or high spectral resolution (or hyperspectral) imagery. We determined if two previously published indices (Datt 1999), which were specifically developed to predict chlorophyll content in eucalypt vegetation by remote sensing at the leaf scale, can be extrapolated accurately to the canopy. We derived the two indices from hand-held spectroradiometer data of eucalypt leaves exhibiting a range of insect damage symptoms. We also derived the indices from spectra obtained from high spectral and spatial resolution Compact Airborne Spectrographic Imager 2 (CASI-2) imagery to determine if reasonable estimates at a scale of < 1 m can be achieved. One of the indices (R 850/R 710 index, where R is reflectance) derived from hand-held spectroradiometer data showed a moderate correlation with relative leaf chlorophyll content (r = 0.59, P < 0.05) for all dominant eucalypt species in the study area. The R (850)/R (710) index derived from CASI-2 imagery yielded slightly lower correlations over the entire data set (r = 0.42, P < 0.05), but correlations for individual species were high (r = 0.77, P < 0.05). A scaling analysis indicated that the R (850)/R (710) index was strongly affected by soil and water cover types when pixels were mixed, but appeared to be invariant to changes in proportions of understory, which may limit its application.

  7. NEON: the first continental-scale ecological observatory with airborne remote sensing of vegetation canopy biochemistry and structure

    NASA Astrophysics Data System (ADS)

    Johnson, Brian R.; Kampe, Thomas U.; Kuester, Michele A.; Keller, Michael

    2009-08-01

    The National Ecological Observatory Network (NEON), being funded by the National Science Foundation, is a continental-scale research platform for discovering, understanding and forecasting the impacts of climate change, land-use change, and invasive species on ecology. Local site-based flux tower and field measurements will be coordinated with high resolution, regional airborne remote sensing observations. The NEON Airborne Observation Platform (AOP) consists of an aircraft platform carrying remote sensing instrumentation designed to achieve sub-meter to meter scale ground resolution to bridge scales from organism and stand scales to the scale of satellite based remote sensing. Data from the AOP will be openly available to the science community and will provide quantitative information on land use change, and changes in ecological structure and chemistry including the presence and effects of invasive species. Remote sensing instrumentation consists of an imaging spectrometer measuring surface reflectance over the continuous wavelength range from 400 to 2500 nm with 10 nm resolution, a scanning, small footprint waveform LiDAR for 3-D canopy structure measurements and a high resolution airborne digital camera. The AOP science objectives, key mission requirements, the conceptual design and development status are presented.

  8. Scaling the effects of moose browsing on forage distribution, from the geometry of plant canopies to landscapes

    USGS Publications Warehouse

    De Jager, N. R.; Pastor, J.; Hodgson, A.L.

    2009-01-01

    jointly regulated intake rate during winter. Browsing-induced changes in the small-scale geometry of plant canopies can determine intake rate at larger spatial scales by changing d* relative to d and, hence, which mechanisms determine intake rate, essentially altering how herbivores sense the distribution of their food resources. ?? 2009 by the Ecological Society of America.

  9. Utility of an image-based canopy reflectance modeling tool for remote estimation and LAI and leaf chlorophyll content at regional scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Radiance data recorded by remote sensors function as a unique source for monitoring the terrestrial biosphere and vegetation dynamics at a range of spatial and temporal scales. A key challenge is to relate the remote sensing signal to critical variables describing land surface vegetation canopies su...

  10. Canopy stomatal conductance

    SciTech Connect

    Baldocchi, D.D.; Luxmoore, R.J.; Hatfield, J.L.

    1989-07-14

    Stomata are major conduits for the diffusion of many trace gas species between leaves and the atmosphere. The role of the stomata on controlling gas exchange between the terrestrial biosphere and the atmosphere at the landscape, meso- and global-scales has only recently been recognized. Further advances in modelling large-scale trace gas exchange will depend on our ability to understand and model stomatal mechanics at the scale of the pertinent sub-unit, which is typically that of the canopy. This paper describes two approaches for estimating canopy stomatal conductance. One approach is based on 'bottom-up' scaling. This approach computes canopy stomatal conductance by integrating detailed leaf-level and environmentally-driven, physiological processes with the use of a detailed canopy micrometeorology model. The other approach is based on 'top-down' scaling. It interprets the integrated canopy stomatal conductance from measured fluxes of trace gas exchange. Frameworks for extending these scaling approaches to non-idea conditions are given. 96 refs., 5 figs.

  11. Leaf photosynthetic traits scale with hydraulic conductivity and wood density in Panamanian forest canopy trees.

    PubMed

    Santiago, L S; Goldstein, G; Meinzer, F C; Fisher, J B; Machado, K; Woodruff, D; Jones, T

    2004-08-01

    We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity ( k(L)) of upper branches was positively correlated with maximum rates of net CO(2) assimilation per unit leaf area ( A(area)) and stomatal conductance ( g(s)) across 20 species of canopy trees. Maximum k(L) showed stronger correlation with A(area) than initial k(L) suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch k(L) was negatively correlated with A(area)/ g(s) and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics ( k(theoretical)) was positively related to A(area) and k(L), consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, k(L), A(area), net CO(2) assimilation per unit leaf mass ( A(mass)), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes.

  12. Toward regional- to continental-scale estimates of vegetation canopy height: An empirical approach based on data from the Shuttle Radar Topography Mission

    NASA Astrophysics Data System (ADS)

    Walker, Wayne S.

    This dissertation investigates the feasibility of exploiting interferometric synthetic aperture radar (InSAR) data acquired during the 2000 Shuttle Radar Topography Mission (SRTM) for the purpose of obtaining regional- to continental-scale estimates of vegetation canopy height. The specific objectives were to (1) assess the quality of SRTM C- and X-band data in the context of canopy height retrieval with an emphasis on vertical accuracy and horizontal resolution, (2) determine the extent to which SRTM C-band data could be used to develop empirical models for canopy height prediction, and (3) develop a robust SRTM-based approach for generating a year-2000 baseline map of canopy height for the conterminous U.S. The assessment of SRTM data quality revealed the presence of a vegetation signal sufficient to support canopy height retrieval. In the vertical dimension, signal quality was found to be most affected by error attributed to residual phase noise, and a novel strategy for error mitigation was developed. In the horizontal dimension, the resolution of the SRTM C- and X-band data was estimated at approximately 45 meters. Pilot studies conducted in Georgia and California demonstrated that empirical estimates of canopy height could be obtained from the SRTM C-band vegetation signal in conjunction with the National Elevation Dataset assuming the availability of sufficient field reference data and an appropriate level of error mitigation. The studies also revealed the importance of stand-level characteristics, including stand size and shape in the context of phase noise reduction and stand structure where regression model development is concerned. Supported by an unprecedented confluence of national geospatial data layers as well as an extensive national reference data network, a proof-of-concept study was designed to evaluate a novel, empirical approach for broad-scale SRTM-based canopy height mapping. The study produced the first-ever InSAR-based map of canopy height

  13. NEON: the first continental-scale ecological observatory with airborne remote sensing of vegetation canopy biochemistry and structure

    NASA Astrophysics Data System (ADS)

    Kampe, Thomas U.; Johnson, Brian R.; Kuester, Michele; Keller, Michael

    2010-03-01

    The National Ecological Observatory Network (NEON) is an ecological observation platform for discovering, understanding and forecasting the impacts of climate change, land use change, and invasive species on continental-scale ecology. NEON will operate for 30 years and gather long-term data on ecological response changes and on feedbacks with the geosphere, hydrosphere, and atmosphere. Local ecological measurements at sites distributed within 20 ecoclimatic domains across the contiguous United States, Alaska, Hawaii, and Puerto Rico will be coordinated with high resolution, regional airborne remote sensing observations. The Airborne Observation Platform (AOP) is an aircraft platform carrying remote sensing instrumentation designed to achieve sub-meter to meter scale ground resolution, bridging scales from organisms and individual stands to satellite-based remote sensing. AOP instrumentation consists of a VIS/SWIR imaging spectrometer, a scanning small-footprint waveform LiDAR for 3-D canopy structure measurements and a high resolution airborne digital camera. AOP data will be openly available to scientists and will provide quantitative information on land use change and changes in ecological structure and chemistry including the presence and effects of invasive species. AOP science objectives, key mission requirements, and development status are presented including an overview of near-term risk-reduction and prototyping activities.

  14. Assessment of rice leaf chlorophyll content using visible bands at different growth stages at both the leaf and canopy scale

    NASA Astrophysics Data System (ADS)

    Saberioon, M. M.; Amin, M. S. M.; Anuar, A. R.; Gholizadeh, A.; Wayayok, A.; Khairunniza-Bejo, S.

    2014-10-01

    Nitrogen is an important variable for paddy farming management. The objectives of this study were to develop and test a new method to determine the status of nitrogen and chlorophyll content in rice leaf by analysing and considering all visible bands derived from images captured using a conventional digital camera. The images from the 6-pannel leaf colour chart were acquired using Basler Scout scA640-70fc under light-emitting diode lighting, in which principal component analysis was used to retain the lower order principal component to develop a new index. Digital photographs of the upper most collared leaf of rice (Oriza sativa L.), grown over a range of soils with different nitrogen treatments, were processed into 11 indices and IPCA through six growth stages. Also a conventional digital camera mounted to an unmanned aerial vehicle was used to acquire images over the rice canopy for the purpose of verification. The result indicated that the conventional digital camera at the both leaf (r = -0.81) and the canopy (r = 0.78) scale could be used as a sensor to determine the status of chlorophyll content in rice plants through different growth stages. This indicates that conventional low-cost digital cameras can be used for determining chlorophyll content and consequently for monitoring nitrogen content of the growing rice plant, thus offering a potentially inexpensive, fast, accurate and suitable tool for rice growers. Additionally, results confirmed that a low cost LARS system would be well suited for high spatial and temporal resolution images and data analysis for proper assessment of key nutrients in rice farming in a fast, inexpensive and non-destructive way.

  15. Observations of the scale-dependent turbulence and evaluation of the flux–gradient relationship for sensible heat for a closed Douglas-fir canopy in very weak wind conditions

    DOE PAGES

    Vickers, D.; Thomas, C. K.

    2014-09-16

    Observations of the scale-dependent turbulent fluxes, variances, and the bulk transfer parameterization for sensible heat above, within, and beneath a tall closed Douglas-fir canopy in very weak winds are examined. The daytime sub-canopy vertical velocity spectra exhibit a double-peak structure with peaks at timescales of 0.8 s and 51.2 s. A double-peak structure is also observed in the daytime sub-canopy heat flux co-spectra. The daytime momentum flux co-spectra in the upper bole space and in the sub-canopy are characterized by a relatively large cross-wind component, likely due to the extremely light and variable winds, such that the definition of amore » mean wind direction, and subsequent partitioning of the momentum flux into along- and cross-wind components, has little physical meaning. Positive values of both momentum flux components in the sub-canopy contribute to upward transfer of momentum, consistent with the observed sub-canopy secondary wind speed maximum. For the smallest resolved scales in the canopy at nighttime, we find increasing vertical velocity variance with decreasing timescale, consistent with very small eddies possibly generated by wake shedding from the canopy elements that transport momentum, but not heat. Unusually large values of the velocity aspect ratio within the canopy were observed, consistent with enhanced suppression of the horizontal wind components compared to the vertical by the very dense canopy. The flux–gradient approach for sensible heat flux is found to be valid for the sub-canopy and above-canopy layers when considered separately in spite of the very small fluxes on the order of a few W m−2 in the sub-canopy. However, single-source approaches that ignore the canopy fail because they make the heat flux appear to be counter-gradient when in fact it is aligned with the local temperature gradient in both the sub-canopy and above-canopy layers. While sub-canopy Stanton numbers agreed well with values typically reported

  16. Effects of Fine-Scale Landscape Variability on Satellite-Derived Land Surface Temperature Products Over Sparse Vegetation Canopies

    NASA Astrophysics Data System (ADS)

    Powell, R. L.; Goulden, M.; Peterson, S.; Roberts, D. A.; Still, C. J.

    2015-12-01

    Temperature is a primary environmental control on biological systems and processes at a range of spatial and temporal scales, from controlling biochemical processes such as photosynthesis to influencing continental-scale species distribution. The Landsat satellite series provides a long record (since the mid-1980s) of relatively high spatial resolution thermal infrared (TIR) imagery, from which we derive land surface temperature (LST) grids. Here, we investigate fine spatial resolution factors that influence Landsat-derived LST over a spectrally and spatially heterogeneous landscape. We focus on paired sites (inside/outside a 1994 fire scar) within a pinyon-juniper scrubland in Southern California. The sites have nearly identical micro-meteorology and vegetation species composition, but distinctly different vegetation abundance and structure. The tower at the unburned site includes a number of in-situ imaging tools to quantify vegetation properties, including a thermal camera on a pan-tilt mount, allowing hourly characterization of landscape component temperatures (e.g., sunlit canopy, bare soil, leaf litter). We use these in-situ measurements to assess the impact of fine-scale landscape heterogeneity on estimates of LST, including sensitivity to (i) the relative abundance of component materials, (ii) directional effects due to solar and viewing geometry, (iii) duration of sunlit exposure for each compositional type, and (iv) air temperature. To scale these properties to Landsat spatial resolution (~100-m), we characterize the sub-pixel composition of landscape components (in addition to shade) by applying spectral mixture analysis (SMA) to the Landsat Operational Land Imager (OLI) spectral bands and test the sensitivity of the relationships established with the in-situ data at this coarser scale. The effects of vegetation abundance and cover height versus other controls on satellite-derived estimates of LST will be assessed by comparing estimates at the burned vs

  17. Solar-induced chlorophyll fluorescence that correlates with canopy photosynthesis on diurnal and seasonal scales in a temperate deciduous forest

    NASA Astrophysics Data System (ADS)

    Yang, Xi; Tang, Jianwu; Mustard, John F.; Lee, Jung-Eun; Rossini, Micol; Joiner, Joanna; Munger, J. William; Kornfeld, Ari; Richardson, Andrew D.

    2015-04-01

    Previous studies have suggested that solar-induced chlorophyll fluorescence (SIF) is correlated with Gross Primary Production (GPP). However, it remains unclear to what extent this relationship is due to absorbed photosynthetically active radiation (APAR) and/or light use efficiency (LUE). Here we present the first time series of near-surface measurement of canopy-scale SIF at 760 nm in temperate deciduous forests. SIF correlated with GPP estimated with eddy covariance at diurnal and seasonal scales (r2 = 0.82 and 0.73, respectively), as well as with APAR diurnally and seasonally (r2 = 0.90 and 0.80, respectively). SIF/APAR is significantly positively correlated with LUE and is higher during cloudy days than sunny days. Weekly tower-based SIF agreed with SIF from the Global Ozone Monitoring Experiment-2 (r2 = 0.82). Our results provide ground-based evidence that SIF is directly related to both APAR and LUE and thus GPP, and confirm that satellite SIF can be used as a proxy for GPP.

  18. Predicting landscape-scale CO2 flux at a pasture and rice paddy with long-term hyperspectral canopy reflectance measurements

    NASA Astrophysics Data System (ADS)

    Matthes, J. H.; Knox, S. H.; Sturtevant, C.; Sonnentag, O.; Verfaillie, J.; Baldocchi, D.

    2015-08-01

    Measurements of hyperspectral canopy reflectance provide a detailed snapshot of information regarding canopy biochemistry, structure and physiology. In this study, we collected 5 years of repeated canopy hyperspectral reflectance measurements for a total of over 100 site visits within the flux footprints of two eddy covariance towers at a pasture and rice paddy in northern California. The vegetation at both sites exhibited dynamic phenology, with significant interannual variability in the timing of seasonal patterns that propagated into interannual variability in measured hyperspectral reflectance. We used partial least-squares regression (PLSR) modeling to leverage the information contained within the entire canopy reflectance spectra (400-900 nm) in order to investigate questions regarding the connection between measured hyperspectral reflectance and landscape-scale fluxes of net ecosystem exchange (NEE) and gross primary productivity (GPP) across multiple timescales, from instantaneous flux to monthly integrated flux. With the PLSR models developed from this large data set we achieved a high level of predictability for both NEE and GPP flux in these two ecosystems, where the R2 of prediction with an independent validation data set ranged from 0.24 to 0.69. The PLSR models achieved the highest skill at predicting the integrated GPP flux for the week prior to the hyperspectral canopy reflectance collection, whereas the NEE flux often achieved the same high predictive power at daily to monthly integrated flux timescales. The high level of predictability achieved by PLSR in this study demonstrated the potential for using repeated hyperspectral canopy reflectance measurements to help partition NEE into its component fluxes, GPP and ecosystem respiration, and for using quasi-continuous hyperspectral reflectance measurements to model regional carbon flux in future analyses.

  19. Predicting landscape-scale CO2 flux at a pasture and rice paddy with long-term hyperspectral canopy reflectance measurements

    NASA Astrophysics Data System (ADS)

    Matthes, J. H.; Knox, S. H.; Sturtevant, C.; Sonnentag, O.; Verfaillie, J.; Baldocchi, D.

    2015-03-01

    Measurements of hyperspectral canopy reflectance provide a detailed snapshot of information regarding canopy biochemistry, structure and physiology. In this study, we collected five years of repeated canopy hyperspectral reflectance measurements for a total of over 100 site visits within the flux footprints of two eddy covariance towers at a pasture and rice paddy in Northern California. The vegetation at both sites exhibited dynamic phenology, with significant inter-annual variability in the timing of seasonal patterns that propagated into inter-annual variability in measured hyperspectral reflectance. We used partial least-squares regression (PLSR) modeling to leverage the information contained within the entire continuous canopy reflectance spectra (400-900 nm) in order to investigate questions regarding the connection between measured hyperspectral reflectance and landscape-scale fluxes of net ecosystem exchange (NEE) and gross primary productivity (GPP) across multiple timescales, from instantaneous flux to monthly-integrated flux. With the PLSR models developed from this large dataset we achieved a high level of predictability for both NEE and GPP flux in these two ecosystems, where the R2 of prediction with an independent validation dataset ranged from 0.24 to 0.69. The PLSR models achieved the highest skill at predicting the integrated GPP flux for the week prior to the hyperspectral canopy reflectance collection, whereas the NEE flux often achieved the same high predictive power at the daily- through monthly-integrated flux timescales. The high level of predictability achieved by PLSR regression in this study demonstrated the potential for using repeated hyperspectral canopy reflectance measurements to help partition NEE measurements into its component fluxes, GPP and ecosystem respiration, and for using continuous hyperspectral reflectance measurements to model regional carbon flux in future analyses.

  20. The relationship between canopy structure, light dynamics and deciduousness in a seasonal tropical forest in Panama: A multiple scale study using remote sensing and allometry

    NASA Astrophysics Data System (ADS)

    Bohlman, Stephanie Ann

    This dissertation uses two tools, remote sensing and allometry, to quantify canopy structure, phenology and light interception on stand to landscape levels in a semi-deciduous tropical forest in Panama. The remote sensing studies used a multiple scale approach. First relationships between spectral and physiological data were developed on a fine spatial scale. Then the interpretations were verified at a series of plots across the landscape. Finally, interpretation was applied to satellite images of the whole Panama Canal Zone. Using this approach, the applicability of the relationship between the Normalized Difference Vegetation Index (NDVI) and fraction of intercepted photosynthetically active radiation (FPAR) was tested for the first time in a tropical forest. NDVI was more strongly related to changes in the FPAR of the upper canopy than FPAR of the whole canopy profile. Both NDVI and FPAR were driven by the contrast of deciduous and non-deciduous tree crowns in the dry season. On a landscape scale, spectral mixture analysis (SMA) of remotely-sensed images quantified the percent of deciduous tree crowns in the overstory very accurately. Using the map of deciduousness developed from a Landsat image, I found high fine scale variability in deciduousness, highly deciduous patches throughout the canal zone of 4--250 ha in size, and landscape trends related to rainfall and geologic formation. Allometric relationships between stem diameter, tree height and crown size were developed for 65 species on Barro Colorado Island. Tree height was asymptotic with stem diameter, but crown radius was not, continuing to grow at large diameters. Allometric relationships through ontongeny varied among different functional groups. Gap species are taller than shade species when both functional groups were below 10 cm dbh, but have smaller crowns than shade species above 10 cm dbh. Subcanopy species are shorter with larger canopies than tall species. A simple canopy model based on these

  1. Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance

    NASA Astrophysics Data System (ADS)

    Whitley, Rhys; Medlyn, Belinda; Zeppel, Melanie; Macinnis-Ng, Catriona; Eamus, Derek

    2009-06-01

    SUMMARYThe responses of canopy conductance to variation in solar radiation, vapour pressure deficit and soil moisture have been extensively modelled using a Jarvis-Stewart (JS) model. Modelled canopy conductance has then often been used to predict transpiration using the Penman-Monteith (PM) model. We previously suggested an alternative approach in which the JS model is modified to directly estimate transpiration rather than canopy conductance. In the present study we used this alternative approach to model tree water fluxes from an Australian native forest over an annual cycle. For comparative purposes we also modelled canopy conductance and estimated transpiration via the PM model. Finally we applied an artificial neural network as a statistical benchmark to compare the performance of both models. Both the PM and modified JS models were parameterised using solar radiation, vapour pressure deficit and soil moisture as inputs with results that compare well with previous studies. Both models performed comparably well during the summer period. However, during winter the PM model was found to fail during periods of high rates of transpiration. In contrast, the modified JS model was able to replicate observed sapflow measurements throughout the year although it too tended to underestimate rates of transpiration in winter under conditions of high rates of transpiration. Both approaches to modelling transpiration gave good agreement with hourly, daily and total sums of sapflow measurements with the modified JS and PM models explaining 87% and 86% of the variance, respectively. We conclude that these three approaches have merit at different time-scales.

  2. Evapotranspiration in water limited environments: Up-scaling from the crown canopy to the eddy flux footprint

    NASA Astrophysics Data System (ADS)

    Rwasoka, D. T.; Reyes, L.; van der Tol, C.; Su, Z.; Lubczynski, M.

    2010-05-01

    Evapotranspiration in Water Limited Environments (WLE) plays a central role in explaining ecohydrological dynamics and the mass-energy interactions between the land surface and the atmosphere. To gain more in-depth knowledge on these interactions and dynamics demands that evapotranspiration components be quantified and the role of each of each evaporative flux be known at finer temporal and spatial scales ( ). In this research we integrate eddy covariance, energy flux, biometric and sapflow measurements together with remote sensing. The aims of the research are to assess (1) the role of transpiration fluxes in dry areas, (2) the energy balance and (3) the applicability of eddy footprints in tree transpiration up-scaling and mapping using remote sensing. Field measurements were done in the Sardon catchment close to Salamanca, Spain (DOY 249 -269, 2009).Where the tree species Quercus Ilex and Quercus Pyrenaica are the dominant vegetation and thus were the focus of this study. Sap-flow was measured and up-scaled using Quick-Bird imagery combined with species-specific biometric up-scaling functions. Post-processing eddy data was done to determine evapotranspiration from sensible and latent heat fluxes. Furthermore, 2-D flux footprints were determined using 30-min energy flux data, and discretized over the land surface. Finally, the transpiration contribution to evapotranspiration was determined by up-scaling sap-flow from the tree canopies inside the eddy footprint. It was found that Quercus ilex and Quercus pyrenaica transpire an average of 0.17 mm/day, while average dry season evapotranspiration was ~0.4 mm/day. The sources of the measured evapotranspiration varied with wind direction and thermal stratification. The cross wind integrated footprint varies 20m to 600m during daytime and reaches up to 1800m at night. The cumulative crosswind footprint shows that about 80% of the flux is from a distance of 300-500m. We were able to achieve an energy balance closure of 86

  3. Observations of the scale-dependent turbulence and evaluation of the flux-gradient relationship for sensible heat for a closed Douglas-Fir canopy in very weak wind conditions

    DOE PAGES

    Vickers, D.; Thomas, C.

    2014-05-13

    Observations of the scale-dependent turbulent fluxes and variances above, within and beneath a tall closed Douglas-Fir canopy in very weak winds are examined. The daytime subcanopy vertical velocity spectra exhibit a double-peak structure with peaks at time scales of 0.8 s and 51.2 s. A double-peak structure is also observed in the daytime subcanopy heat flux cospectra. The daytime momentum flux cospectra inside the canopy and in the subcanopy are characterized by a relatively large cross-wind component, likely due to the extremely light and variable winds, such that the definition of a mean wind direction, and subsequent partitioning of themore » momentum flux into along- and cross-wind components, has little physical meaning. Positive values of both momentum flux components in the subcanopy contribute to upward transfer of momentum, consistent with the observed mean wind speed profile. In the canopy at night at the smallest resolved scales, we find relatively large momentum fluxes (compared to at larger scales), and increasing vertical velocity variance with decreasing time scale, consistent with very small eddies likely generated by wake shedding from the canopy elements that transport momentum but not heat. We find unusually large values of the velocity aspect ratio within the canopy, consistent with enhanced suppression of the horizontal wind components compared to the vertical by the canopy. The flux-gradient approach for sensible heat flux is found to be valid for the subcanopy and above-canopy layers when considered separately; however, single source approaches that ignore the canopy fail because they make the heat flux appear to be counter-gradient when in fact it is aligned with the local temperature gradient in both the subcanopy and above-canopy layers. Modeled sensible heat fluxes above dark warm closed canopies are likely underestimated using typical values of the Stanton number.« less

  4. Large-scale variation in combined impacts of canopy loss and disturbance on community structure and ecosystem functioning.

    PubMed

    Crowe, Tasman P; Cusson, Mathieu; Bulleri, Fabio; Davoult, Dominique; Arenas, Francisco; Aspden, Rebecca; Benedetti-Cecchi, Lisandro; Bevilacqua, Stanislao; Davidson, Irvine; Defew, Emma; Fraschetti, Simonetta; Golléty, Claire; Griffin, John N; Herkül, Kristjan; Kotta, Jonne; Migné, Aline; Molis, Markus; Nicol, Sophie K; Noël, Laure M-L J; Pinto, Isabel Sousa; Valdivia, Nelson; Vaselli, Stefano; Jenkins, Stuart R

    2013-01-01

    Ecosystems are under pressure from multiple human disturbances whose impact may vary depending on environmental context. We experimentally evaluated variation in the separate and combined effects of the loss of a key functional group (canopy algae) and physical disturbance on rocky shore ecosystems at nine locations across Europe. Multivariate community structure was initially affected (during the first three to six months) at six locations but after 18 months, effects were apparent at only three. Loss of canopy caused increases in cover of non-canopy algae in the three locations in southern Europe and decreases in some northern locations. Measures of ecosystem functioning (community respiration, gross primary productivity, net primary productivity) were affected by loss of canopy at five of the six locations for which data were available. Short-term effects on community respiration were widespread, but effects were rare after 18 months. Functional changes corresponded with changes in community structure and/or species richness at most locations and times sampled, but no single aspect of biodiversity was an effective predictor of longer-term functional changes. Most ecosystems studied were able to compensate in functional terms for impacts caused by indiscriminate physical disturbance. The only consistent effect of disturbance was to increase cover of non-canopy species. Loss of canopy algae temporarily reduced community resistance to disturbance at only two locations and at two locations actually increased resistance. Resistance to disturbance-induced changes in gross primary productivity was reduced by loss of canopy algae at four locations. Location-specific variation in the effects of the same stressors argues for flexible frameworks for the management of marine environments. These results also highlight the need to analyse how species loss and other stressors combine and interact in different environmental contexts.

  5. The potential of detecting intermediate-scale biomass and canopy interception in a coniferous forest using cosmic-ray neutron intensity measurements and neutron transport modeling

    NASA Astrophysics Data System (ADS)

    Andreasen, M.; Looms, M. C.; Bogena, H. R.; Desilets, D.; Zreda, M. G.; Sonnenborg, T. O.; Jensen, K. H.

    2014-12-01

    The water stored in the various compartments of the terrestrial ecosystem (in snow, canopy interception, soil and litter) controls the exchange of the water and energy between the land surface and the atmosphere. Therefore, measurements of the water stored within these pools are critical for the prediction of e.g. evapotranspiration and groundwater recharge. The detection of cosmic-ray neutron intensity is a novel non-invasive method for the quantification of continuous intermediate-scale soil moisture. The footprint of the cosmic-ray neutron probe is a hemisphere of a few hectometers and subsurface depths of 10-70 cm depending on wetness. The cosmic-ray neutron method offers measurements at a scale between the point-scale measurements and large-scale satellite retrievals. The cosmic-ray neutron intensity is inversely correlated to the hydrogen stored within the footprint. Overall soil moisture represents the largest pool of hydrogen and changes in the soil moisture clearly affect the cosmic-ray neutron signal. However, the neutron intensity is also sensitive to variations of hydrogen in snow, canopy interception and biomass offering the potential to determine water content in such pools from the signal. In this study we tested the potential of determining canopy interception and biomass using cosmic-ray neutron intensity measurements within the framework of the Danish Hydrologic Observatory (HOBE) and the Terrestrial Environmental Observatories (TERENO). Continuous measurements at the ground and the canopy level, along with profile measurements were conducted at towers at forest field sites. Field experiments, including shielding the cosmic-ray neutron probes with cadmium foil (to remove lower-energy neutrons) and measuring reference intensity rates at complete water saturated conditions (on the sea close to the HOBE site), were further conducted to obtain an increased understanding of the physics controlling the cosmic-ray neutron transport and the equipment used

  6. Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy

    NASA Astrophysics Data System (ADS)

    Acton, W. J. F.; Schallhart, S.; Langford, B.; Valach, A.; Rantala, P.; Fares, S.; Carriero, G.; Tillmann, R.; Tomlinson, S. J.; Dragosits, U.; Gianelle, D.; Hewitt, C. N.; Nemitz, E.

    2015-10-01

    This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton transfer reaction-mass spectrometer (PTR-MS) and a proton transfer reaction-time of flight-mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (PTR-MS) and eddy covariance (PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean day-time flux of 1.9 mg m-2 h-1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28 day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m-2 h-1 was calculated using the MEGAN isoprene emissions algorithms (Guenther et al., 2006). A detailed tree species distribution map for the site enabled the leaf-level emissions of isoprene and monoterpenes recorded using GC-MS to be scaled up to produce a "bottom-up" canopy-scale flux. This was compared with the "top-down" canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.

  7. Controls on seasonal patterns of maximum ecosystem carbon uptake and canopy-scale photosynthetic light response: contributions from both temperature and photoperiod.

    PubMed

    Stoy, Paul C; Trowbridge, Amy M; Bauerle, William L

    2014-02-01

    Most models of photosynthetic activity assume that temperature is the dominant control over physiological processes. Recent studies have found, however, that photoperiod is a better descriptor than temperature of the seasonal variability of photosynthetic physiology at the leaf scale. Incorporating photoperiodic control into global models consequently improves their representation of the seasonality and magnitude of atmospheric CO2 concentration. The role of photoperiod versus that of temperature in controlling the seasonal variability of photosynthetic function at the canopy scale remains unexplored. We quantified the seasonal variability of ecosystem-level light response curves using nearly 400 site years of eddy covariance data from over eighty Free Fair-Use sites in the FLUXNET database. Model parameters describing maximum canopy CO2 uptake and the initial slope of the light response curve peaked after peak temperature in about 2/3 of site years examined, emphasizing the important role of temperature in controlling seasonal photosynthetic function. Akaike's Information Criterion analyses indicated that photoperiod should be included in models of seasonal parameter variability in over 90% of the site years investigated here, demonstrating that photoperiod also plays an important role in controlling seasonal photosynthetic function. We also performed a Granger causality analysis on both gross ecosystem productivity (GEP) and GEP normalized by photosynthetic photon flux density (GEP n ). While photoperiod Granger-caused GEP and GEP n in 99 and 92% of all site years, respectively, air temperature Granger-caused GEP in a mere 32% of site years but Granger-caused GEP n in 81% of all site years. Results demonstrate that incorporating photoperiod may be a logical step toward improving models of ecosystem carbon uptake, but not at the expense of including enzyme kinetic-based temperature constraints on canopy-scale photosynthesis.

  8. Plant photomorphogenesis and canopy growth

    NASA Technical Reports Server (NTRS)

    Ballare, Carlos L.; Scopel, Ana L.

    1994-01-01

    An important motivation for studying photomorphogenesis is to understand the relationships among plant photophysiology in canopies, canopy productivity, and agronomic yield. This understanding is essential to optimize lighting systems used for plant farming in controlled environments (CE) and for the design of genetically engineered crop strains with altered photoresponses. This article provides an overview of some basic principles of plant photomorphogenesis in canopies and discusses their implications for (1) scaling up information on plant photophysiology from individual plants in CE to whole canopies in the field, and (2) designing lighting conditions to increase plant productivity in CE used for agronomic purposes (e.g. space farming in CE Life Support Systems). We concentrate on the visible (lambda between 400 and 700 nm) and far-infrared (FR; lambda greater than 700 nm) spectral regions, since the ultraviolet (UV; 280 to 400 nm) is covered by other authors in this volume.

  9. Farm-scale evaluation of the impact of Cry1Ab Bt maize on canopy nontarget arthropods: a 3-year study.

    PubMed

    Arias-Martín, María; García, Matías; Castañera, Pedro; Ortego, Félix; Farinós, Gema P

    2016-08-11

    The cultivation of Cry1Ab-expressing genetically modified MON810 (Bt maize) has led to public concern in Europe, regarding its impact on nontarget arthropods (NTAs). We have assessed the potential effects of DKC 6451 YG (MON810) maize on canopy NTAs in a farm-scale study performed in Central Spain during 3 years. The study focused on hemipteran herbivores (leafhoppers and planthoppers) and hymenopteran parasitic wasps (mymarids) collected by yellow sticky traps, which accounted for 72% of the total number of insects studied. The dynamics and abundance of these groups varied among years, but no significant differences were found between Bt and non-Bt maize, indicating that Bt maize had no negative effect on these taxa. Nonetheless, the Cry1Ab toxin was detected in 2 different arthropods collected from Bt maize foliage, the cicadellids Zyginidia scutellaris and Empoasca spp. A retrospective power analysis on the arthropod abundance data for our field trials has determined that Z. scutellaris and the family Mymaridae have high capacity to detect differences between the Bt maize and its isogenic counterpart. The use of these canopy NTAs as surrogates for assessing environmental impacts of Bt maize is discussed.

  10. Modeling Coniferous Canopy Structure over Extensive Areas for Ray Tracing Simulations: Scaling from the Leaf to the Stand Level

    NASA Astrophysics Data System (ADS)

    van Aardt, J. A.; van Leeuwen, M.; Kelbe, D.; Kampe, T.; Krause, K.

    2015-12-01

    Remote sensing is widely accepted as a useful technology for characterizing the Earth surface in an objective, reproducible, and economically feasible manner. To date, the calibration and validation of remote sensing data sets and biophysical parameter estimates remain challenging due to the requirements to sample large areas for ground-truth data collection, and restrictions to sample these data within narrow temporal windows centered around flight campaigns or satellite overpasses. The computer graphics community have taken significant steps to ameliorate some of these challenges by providing an ability to generate synthetic images based on geometrically and optically realistic representations of complex targets and imaging instruments. These synthetic data can be used for conceptual and diagnostic tests of instrumentation prior to sensor deployment or to examine linkages between biophysical characteristics of the Earth surface and at-sensor radiance. In the last two decades, the use of image generation techniques for remote sensing of the vegetated environment has evolved from the simulation of simple homogeneous, hypothetical vegetation canopies, to advanced scenes and renderings with a high degree of photo-realism. Reported virtual scenes comprise up to 100M surface facets; however, due to the tighter coupling between hardware and software development, the full potential of image generation techniques for forestry applications yet remains to be fully explored. In this presentation, we examine the potential computer graphics techniques have for the analysis of forest structure-function relationships and demonstrate techniques that provide for the modeling of extremely high-faceted virtual forest canopies, comprising billions of scene elements. We demonstrate the use of ray tracing simulations for the analysis of gap size distributions and characterization of foliage clumping within spatial footprints that allow for a tight matching between characteristics

  11. Canopy-scale flux measurements and bottom-up emission estimates of volatile organic compounds from a mixed oak and hornbeam forest in northern Italy

    NASA Astrophysics Data System (ADS)

    Acton, W. Joe F.; Schallhart, Simon; Langford, Ben; Valach, Amy; Rantala, Pekka; Fares, Silvano; Carriero, Giulia; Tillmann, Ralf; Tomlinson, Sam J.; Dragosits, Ulrike; Gianelle, Damiano; Hewitt, C. Nicholas; Nemitz, Eiko

    2016-06-01

    This paper reports the fluxes and mixing ratios of biogenically emitted volatile organic compounds (BVOCs) 4 m above a mixed oak and hornbeam forest in northern Italy. Fluxes of methanol, acetaldehyde, isoprene, methyl vinyl ketone + methacrolein, methyl ethyl ketone and monoterpenes were obtained using both a proton-transfer-reaction mass spectrometer (PTR-MS) and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) together with the methods of virtual disjunct eddy covariance (using PTR-MS) and eddy covariance (using PTR-ToF-MS). Isoprene was the dominant emitted compound with a mean daytime flux of 1.9 mg m-2 h-1. Mixing ratios, recorded 4 m above the canopy, were dominated by methanol with a mean value of 6.2 ppbv over the 28-day measurement period. Comparison of isoprene fluxes calculated using the PTR-MS and PTR-ToF-MS showed very good agreement while comparison of the monoterpene fluxes suggested a slight over estimation of the flux by the PTR-MS. A basal isoprene emission rate for the forest of 1.7 mg m-2 h-1 was calculated using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) isoprene emission algorithms (Guenther et al., 2006). A detailed tree-species distribution map for the site enabled the leaf-level emission of isoprene and monoterpenes recorded using gas-chromatography mass spectrometry (GC-MS) to be scaled up to produce a bottom-up canopy-scale flux. This was compared with the top-down canopy-scale flux obtained by measurements. For monoterpenes, the two estimates were closely correlated and this correlation improved when the plant-species composition in the individual flux footprint was taken into account. However, the bottom-up approach significantly underestimated the isoprene flux, compared with the top-down measurements, suggesting that the leaf-level measurements were not representative of actual emission rates.

  12. Change Analysis of the Spectral Characteristics of Rubber Trees at Canopy and Leaf Scales during the Brazilian Autumn

    NASA Astrophysics Data System (ADS)

    Amaral, C. H.; Almeida, T. I. R.; Quitério, G. C. M.; Alves, M. N.; Souza Filho, C. R.

    2012-07-01

    The objective of this work is to investigate the hyperspectral remote sensing potential to detect spectral changes undergone by clones of two rubber trees within Brazilian Autumn, with decrease of rain, temperature and photoperiod between May and June. Indirectly, we also analyze the ability of the data to help discriminating the clones at two dates in autumn. The average canopy spectra of the stands were obtained with two overpasses of the ProSpecTIR-VS airborne hyperspectral sensor (357 bands between 400-2,500 nm; spatial resolution of 1m) by 14th May and 17th June, in 2010 year. Additionally measurements of leaf spectra were taken in the same dates, but in the 2011 year. Considering the analysis of the spectra measured from the three stands, this indicates that spectral differences in the VIS (400-700 nm) region are of genetic origin and occur regardless of environmental conditions and period of data collection. In the NIR (700-1,300 nm) range, the environmental factors predominate in the two periods of data collection. The SWIR (1,300-2,500 nm) displayed the largest differences between the months of data collection. In May, the relationship between stands indicated the prevalence of environmental aspects. However, in June, the stands and clones spectral behaviour indicates that as the temperature, the rainfall and the photoperiod are lower closer to winter, the SWIR can be effectively used to discriminate and map these clones separately.

  13. 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

    Figures Figures 1 Top of canopy digital terrain model ( DTM ) from statewide, large footprint, lower sampling density LIDAR data provided by the North...4 2 Top of canopy DTM from small footprint, higher sampling density LIDAR data ..................... 4 3 Top of canopy DTM ... DTM from small footprint, higher sampling density LIDAR data provided by ERDC-CERL and used in the case study (3-D perspective

  14. Ray Trace Modeling to Determine Optimal Forest Canopy Gap Size for Reduced Solar Irradiance During Snowmelt: Field Verification and Continental Scale Application

    NASA Astrophysics Data System (ADS)

    Musselman, K. N.; Pomeroy, J. W.; Link, T. E.

    2014-12-01

    Forest hydrology has long debated the influence of forest gap size on the shortwave radiation regime and subsequent snowmelt rates. To address this question, a new ray trace solar transmittance model is presented to evaluate the sensitivity of gap influence on shortwave irradiance patterns to latitude, gap size, and time of year in fragmented forest environments. The ray trace model takes into account solar position, gap and forest geometry, and position within or near the gap, and was tested against measurements of shortwave radiation from 20 pyranometers in and around a gap in a mixed conifer forest and compared to simpler canopy transmittance models that ignored shading or that scaled transmittance according to leaf area index. The ray trace model reduced the large errors obtained by simple canopy transmittance models; at the 20 pyranometer locations, average biases in excess of ~ ±90 W m-2 were reduced to better than 4 W m-2. These results suggest that an accurate description of the spatial variability of solar irradiance in and around a forest gap requires explicit calculation of how gaps modify the canopy transmittance. To examine model sensitivity to key parameters, gap size, latitude, and day of year were varied under clear-sky conditions. The calculated spatial distribution patterns of cumulative daily solar irradiance inform how forest gap sizes might be optimized to minimize (shortwave) snowmelt energy. As gap size was changed for a given latitude and date, the (spatial) coefficient of variation (CV) of cumulative daily irradiance exhibited a distinct maximum that is a function of gap geometry and solar angle; smaller (larger) gaps with more diffuse (direct beam) radiation exhibited reduced spatial variability of irradiance. The results indicate that optimum forest gap sizes to reduce solar radiation while maximizing gap area depend on date and latitude; using mean snowmelt onset dates for a range of latitudes (31°N - 71°N) spanning North American

  15. Species differences in stomatal control of water loss at the canopy scale in a mature bottomland deciduous forest

    NASA Astrophysics Data System (ADS)

    Pataki, D. E.; Oren, R.

    2003-12-01

    In order to evaluate factors controlling transpiration of six common eastern deciduous species in North America, a model describing responses of canopy stomatal conductance ( GS) to net radiation ( RN), vapor pressure deficit ( D) and relative extractable soil water (REW) was parameterized from sap flux data. Sap flux was measured in 24 mature trees consisting of the species Carya tomentosa, Quercus alba, Q. rubra, Fraxinus americana, Liriodendron tulipifera, and Liquidambar styraciflua in a bottomland oak-hickory forest in the Duke Forest, NC. Species differences in model coefficients were found during the 1997 growing season. All species showed a reduction in GS with increasing D. RN influenced GS in the overstory shade intolerant L. styraciflua to a larger extent than the other species measured. In addition, despite a severe drought during the study period, only L. tulipifera showed a decline in GS with decreasing REW. The primary effect of the drought for the other species appeared to be early autumn leaf senescence and abscission. As a result, despite the drought in this bottomland forest accustomed to ample water supply, maximum daily transpiration (1.6 mm) and growing season transpiration (264 mm) were similar to a nearby upland forest measured during a year of above average precipitation. These results may aid in assessing differences in water use and the ability of bottomland deciduous species to tolerate alterations in the frequency or amount of precipitation. Results also suggest little variation in water use among forests of similar composition and structure growing in different positions in the landscape and subjected to large interannual variation in water supply.

  16. Effect of canopy thickness and canopy saturation on the amount and kinetic energy of throughfall: An experimental approach

    NASA Astrophysics Data System (ADS)

    Nanko, Kazuki; Onda, Yuichi; Ito, Akane; Moriwaki, Hiromu

    2008-03-01

    To investigate how canopy thickness and canopy saturation affect the amount and kinetic energy of throughfall, we conducted indoor experiments using a 9.8-m-tall transplanted Japanese cypress (Chamaecyparis obtusa) and a large-scale rainfall simulator with spray nozzles at a height of 16 m. The amount of throughfall and raindrop sizes and velocities were measured at twenty-four points under four canopy structures generated by staged branch pruning. Decreasing the canopy thickness resulted in increases of the initial throughfall amount, volume proportion of large throughfall drops, the number of drops with high velocities, and throughfall kinetic energy. Compared to a saturated canopy, a canopy undergoing wetting had lower throughfall amounts and volume proportion of large drops, but higher mean drop velocity. Canopy thickness affected throughfall generation by affecting the processes of canopy saturation and drop generation within the canopy.

  17. 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

    2017-03-27

    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 CO2, 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.

  18. Utility of an image-based canopy reflectance modeling tool for remote estimation of LAI and leaf chlorophyll content at the field scale

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A REGularized canopy reFLECtance (REGFLEC) modeling tool that couples leaf optics (PROSPECT), canopy reflectance (ACRM), and atmospheric radiative transfer (6SV1) models is described and the model output of leaf chlorophyll (Cab) and total leaf area index (LAI) is validated against ground measuremen...

  19. ROLE OF CANOPY-SCALE PHOTOCHEMISTRY IN MODIFYING BIOGENIC-ATMOSPHERE EXCHANGE OF REACTIVE TERPENE SPECIES: RESULTS FROM THE CELTIC FIELD STUDY

    EPA Science Inventory

    A one-dimensional canopy model was used to quantify the impact of photochemistry in modifying biosphere-atmosphere exchange of trace gases. Canopy escape efficiencies, defined as the fraction of emission that escapes into the well-mixed boundary layer, were calculated for reactiv...

  20. Key canopy traits drive forest productivity

    PubMed Central

    Reich, Peter B.

    2012-01-01

    Quantifying the mechanistic links between carbon fluxes and forest canopy attributes will advance understanding of leaf-to-ecosystem scaling and its potential application to assessing terrestrial ecosystem metabolism. Important advances have been made, but prior studies that related carbon fluxes to multiple canopy traits are scarce. Herein, presenting data for 128 cold temperate and boreal forests across a regional gradient of 600 km and 5.4°C (from 2.4°C to 7.8°C) in mean annual temperature, I show that stand-scale productivity is a function of the capacity to harvest light (represented by leaf area index, LAI), and to biochemically fix carbon (represented by canopy nitrogen concentration, %N). In combination, LAI and canopy %N explain greater than 75 per cent of variation in above-ground net primary productivity among forests, expressed per year or per day of growing season. After accounting for growing season length and climate effects, less than 10 per cent of the variance remained unexplained. These results mirror similar relations of leaf-scale and canopy-scale (eddy covariance) maximum photosynthetic rates to LAI and %N. Collectively, these findings indicate that canopy structure and chemistry translate from instantaneous physiology to annual carbon fluxes. Given the increasing capacity to remotely sense canopy LAI, %N and phenology, these results support the idea that physiologically based scaling relations can be useful tools for global modelling. PMID:22279168

  1. An economical canopy model for use in urban climatology

    NASA Astrophysics Data System (ADS)

    Terjung, W. H.; O'Rourke, P. A.

    1980-12-01

    A multi-layered canopy leaf energy budget model (CANOPY) has been developed for the purpose of systematically examining the building-vegetation cause and effect structure in urban landscapes. At great computer savings, this simple, parametric model compared favorably with a much more complex canopy model (SPAM). The economic operation of this model makes it possible to investigate the spatial diversity of canopy budget characteristics on a microclimatic, geographical scale.

  2. 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

  3. IMPLEMENTATION OF AN URBAN CANOPY PARAMETERIZATION IN MM5 FOR MESO-GAMMA-SCALE AIR QUALITY MODELING APPLICATIONS

    EPA Science Inventory

    The U.S. Environmental Protection Agency (U.S. EPA) is extending its Models-3/Community Multiscale Air Quality (CMAQ) Modeling System to provide detailed gridded air quality concentration fields and sub-grid variability characterization at neighborhood scales and in urban areas...

  4. Photosynthesis, transpiration, and primary productivity: Scaling up from leaves to canopies and regions using process models and remotely sensed data

    NASA Astrophysics Data System (ADS)

    Chen, D.-X.; Coughenour, M. B.

    2004-12-01

    Biophysical and physiological processes in plants and ecosystems occur over a wide range of spatial and temporal scales. Our knowledge (or models) of these processes is largely at small scales. It is, however, difficult to directly apply mechanistic process-oriented models over large scales due to heterogeneities in the distributions of processes, and nonlinearities in the functional responses of processes to environmental variables. On the other hand, simple parametric/empirical models in which system complexity is lumped into a small number of parameters have been widely employed to describe processes at larger scales. The variation of these parameters in these simple parametric/empirical models depends on the underlying biophysical processes. In this work, we showed that detailed process models and simple parametric models for primary production and transpiration could be effectively combined to scale leaf photosynthesis and transpiration up to large spatial scales. The integrated process model, General Energy Mass Transfer Model (GEMTM), was used to identify major factors contributing to the variability of the parameters in the parametric models for regional transpiration and primary production and quantify their responses to these factors. Simulations with the GEMTM showed that net carbon assimilation was proportional to intercepted photosynthetically active radiation (IPAR), but the radiation use efficiency (RUE) changed with leaf N concentration, temperature, and atmospheric CO2 concentration; transpiration was linearly correlated with the product of net primary production (NPP) and atmospheric water vapor pressure deficit (VPD), and the slope varied with leaf N concentration. RUE increased with leaf N content asymptotically, and responded to temperature in an asymmetric bell shape pattern with a 22°C and 26°C optimal temperature under current ambient and doubled CO2 concentration, respectively. A simple parametric NPP model and a regional transpiration

  5. Explosive Fracturing of an F-16 Canopy for Through-Canopy Crew Egress

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.

    2000-01-01

    Through-canopy crew egress, such as in the Harrier (AV-8B) aircraft, expands escape envelopes by reducing seat ejection delays in waiting for canopy jettison. Adverse aircraft attitude and reduced forward flight speed can further increase the times for canopy jettison. However, the advent of heavy, high-strength polycarbonate canopies for bird-strike resistance has not only increased jettison times, but has made seat penetration impossible. The goal of the effort described in this paper was to demonstrate a method of explosively fracturing the F-16 polycarbonate canopy to allow through-canopy crew ejection. The objectives of this effort were to: 1. Mount the explosive materials on the exterior of the canopy within the mold line, 2. Minimize visual obstructions, 3. Minimize internal debris on explosive activation, 4. Operate within less than 10 ms, 5. Maintain the shape of the canopy after functioning to prevent major pieces from entering the cockpit, and 6. Minimize the resistance of the canopy to seat penetration. All goals and objectives were met in a full-scale test demonstration. In addition to expanding crew escape envelopes, this canopy fracture approach offers the potential for reducing system complexity, weight and cost, while increasing overall reliability, compared to current canopy jettison approaches. To comply with International Traffic in Arms Regulations (ITAR) and permit public disclosure, this document addresses only the principles of explosive fracturing of the F-16 canopy materials and the end result. ITAR regulations restrict information on improving the performance of weapon systems. Therefore, details on the explosive loads and final assembly of this canopy fracture approach, necessary to assure functional performance, are not included.

  6. Canopy Water Content retrieval at different scales from empirical and physically-based remote sensing methods in the SMOS VAS cal/val site

    NASA Astrophysics Data System (ADS)

    Camacho de Coca, Fernando

    The SMOS (Soil Moisture and Ocean Salinity) space mission from the European Space Agency (ESA) is aimed to observe soil moisture over the continents and sea surface salinity over the oceans with enough resolution to be used in global climatic studies. Calibration and validation of SMOS products is an essential activity due to the exploratory nature of the mission. After launch, intense field activities will collect in situ information simultaneous to SMOS obser-vations in order to improve the empirical aspects of retrieval algorithms and to validate the products generated from these observations. One of the cal/val site selected over land is the Valencia Anchor station site (with an extended area for SMOS of 125 x 125 km2), where soil moisture will be measure intensively in 2010. In order to validate the SMOS soil moisture algorithms is necessary to characterize the water content in the vegetation canopy layer. This paper describes the retrieval of the canopy water content (CWC) in the Valencia Anchor station site at different scales using high-resolution satellite sensors and low resolution MODIS data. Two different approaches has been used: (??) an empirical approach has been used for mapping CWC over the VAS site during field campaigns, (??) artificial neural network has been trained with radiative transfer model simulations to analyze the performance of this approach for mapping CWC. 1. Two field campaigns were carried out to collect CWC at ground level in the study area over vineyards and irrigated crops. Measured CWC values for vineyard crops ranged between 0.05 and 0.2 kg/m2, and over irrigated crops CWC ranged between 0.1 and 1,5 kg/m2, which correspond with the full range of expected variations in the study area. An empirical relationship based on a multivariate ordinary least squares algorithm between the collected ground dataset and concomitant reflectance values coming from high resolution (HR) satellite sensors has been selected to produce CWC HR maps

  7. A spatial length scale analysis of turbulent temperature and velocity fluctuations within and above an orchard canopy

    USGS Publications Warehouse

    Wang, Y.S.; Miller, D.R.; Anderson, D.E.; Cionco, R.M.; Lin, J.D.

    1992-01-01

    Turbulent flow within and above an almond orchard was measured with three-dimensional wind sensors and fine-wire thermocouple sensors arranged in a horizontal array. The data showed organized turbulent structures as indicated by coherent asymmetric ramp patterns in the time series traces across the sensor array. Space-time correlation analysis indicated that velocity and temperature fluctuations were significantly correlated over a transverse distance more than 4m. Integral length scales of velocity and temperature fluctuations were substantially greater in unstable conditions than those in stable conditions. The coherence spectral analysis indicated that Davenport's geometric similarity hypothesis was satisfied in the lower frequency region. From the geometric similarity hypothesis, the spatial extents of large ramp structures were also estimated with the coherence functions.

  8. [Distribution patterns of canopy and understory tree species at local scale in a Tierra Firme forest, the Colombian Amazonia].

    PubMed

    Barreto-Silva, Juan Sebastian; López, Dairon Cárdenas; Montoya, Alvaro Javier Duque

    2014-03-01

    The effect of environmental variation on the structure of tree communities in tropical forests is still under debate. There is evidence that in landscapes like Tierra Firme forest, where the environmental gradient decreases at a local level, the effect of soil on the distribution patterns of plant species is minimal, happens to be random or is due to biological processes. In contrast, in studies with different kinds of plants from tropical forests, a greater effect on floristic composition of varying soil and topography has been reported. To assess this, the current study was carried out in a permanent plot of ten hectares in the Amacayacu National Park, Colombian Amazonia. To run the analysis, floristic and environmental variations were obtained according to tree species abundance categories and growth forms. In order to quantify the role played by both environmental filtering and dispersal limitation, the variation of the spatial configuration was included. We used Detrended Correspondence Analysis and Canonical Correspondence Analysis, followed by a variation partitioning, to analyze the species distribution patterns. The spatial template was evaluated using the Principal Coordinates of Neighbor Matrix method. We recorded 14 074 individuals from 1 053 species and 80 families. The most abundant families were Myristicaceae, Moraceae, Meliaceae, Arecaceae and Lecythidaceae, coinciding with other studies from Northwest Amazonia. Beta diversity was relatively low within the plot. Soils were very poor, had high aluminum concentration and were predominantly clayey. The floristic differences explained along the ten hectares plot were mainly associated to biological processes, such as dispersal limitation. The largest proportion of community variation in our dataset was unexplained by either environmental or spatial data. In conclusion, these results support random processes as the major drivers of the spatial variation of tree species at a local scale on Tierra Firme

  9. Turbulence characteristics in grassland canopies and implications for tracer transport

    NASA Astrophysics Data System (ADS)

    Nemitz, E.; Loubet, B.; Lehmann, B. E.; Cellier, P.; Neftel, A.; Jones, S. K.; Hensen, A.; Ihly, B.; Tarakanov, S. V.; Sutton, M. A.

    2009-08-01

    In-canopy turbulence is a required input to study pollutant cycling and chemistry within plant canopies and to link concentrations and sources. Despite the importance of grasslands worldwide, most previous work has focused on forests and crops. Here, turbulence parameters in a mature agricultural grassland canopy were measured with a combination of a small ultrasonic anemometer, hotwire anemometry and a radon (Rn) tracer technique, as part of a measurement to study ammonia (NH3) exchange with grassland. The measurements are used to derive vertical profiles of basic turbulent parameters, for quadrant-hole analysis of the two-parametric frequency distributions of u'-w' and to derive in-canopy eddy diffusivities as input for models of in-canopy tracer transport. The results are in line with previous measurements on taller canopies, but shows increased decoupling between in-canopy flow and above-canopy turbulence. The comparison of sonic anemometry and Rn measurements implies that Lagrangian time-scales must decrease sharply at the ground, with important implications for estimating the magnitude of ground-level and soil emissions from concentration measurements. Atmospheric stability above and within the canopy has little influence on the standard deviation of vertical wind component inside the canopy. Use of the turbulence parameters in an analytical Lagrangian framework, which is here validated for heat transfer, suggests that measured in-canopy profiles of NH3 are consistent with a ground-level source, presumably from senescent plant parts, which is recaptured by the overlying canopy.

  10. Turbulence characteristics in grassland canopies and implications for tracer transport

    NASA Astrophysics Data System (ADS)

    Nemitz, E.; Loubet, B.; Lehmann, B. E.; Cellier, P.; Neftel, A.; Jones, S. K.; Hensen, A.; Ihly, B.; Tarakanov, S. V.; Sutton, M. A.

    2009-01-01

    In-canopy turbulence is a required input to study pollutant cycling and chemistry within plant canopies and to link concentrations and sources. Despite the importance of grasslands worldwide, most previous work has focused on forests and crops. Here, turbulence parameters in a mature agricultural grassland canopy were measured with a combination of a small ultrasonic anemometer, hotwire anemometry and a radon (Rn) tracer technique, as part of a measurement to study ammonia (NH3) exchange with grassland. The measurements are used to derive vertical profiles of basic turbulent parameters, for quadrant-hole analysis of the two-parametric frequency distributions of u'-w' and to derive in-canopy eddy diffusivities as input for models of in-canopy tracer transport. The results are in line with previous measurements on taller canopies, but shows increased decoupling between in-canopy flow and above-canopy turbulence. The comparison of sonic anemometry and Rn measurements implies that Lagrangian time-scales must decrease sharply at the ground, with important implications for estimating the magnitude of ground-level and soil emissions from concentration measurements. Atmospheric stability above and within the canopy has little influence on the standard deviation of vertical wind component inside the canopy. Use of the turbulence parameters in an analytical Lagrangian framework, which is here validated for heat transfer, suggests that measured in-canopy profiles of NH3 are consistent with a ground-level source, presumably from senescent plant parts, which is recaptured by the overlying canopy.

  11. [Valutazione del carico gestionale in un centro diurno psichiatrico: gravosità e recovery style].

    PubMed

    Callegari, Camilla; Caselli, Ivano; Bertù, Lorenza; Berto, Emanuela; Vender, Simone

    2016-01-01

    RIASSUNTO. Scopo. Nella riabilitazione psichiatrica il piano di trattamento individuale può essere formulato a partire da strumenti che offrano una valutazione multidimensionale del paziente. Il lavoro si propone di analizzare il rapporto tra gravosità (distress degli operatori) e stile di recupero (integration e sealing over) dalla patologia psicotica. Ipotizzando che esso influenzi il carico gestionale, lo studio si pone l'ulteriore obiettivo di acquisire maggiori elementi che indirizzino la formulazione di piani terapeutico-riabilitativi più efficaci. Metodi. Lo studio è stato condotto presso un centro diurno psichiatrico, struttura semi-residenziale dei servizi psichiatrici del Sistema Sanitario Nazionale in Italia. 45 pazienti reclutati sono stati valutati mediante la Neuropsychiatric Inventory (NPI - versione italiana) e la Integration/Sealing Over Scale (ISOS - versione italiana), nell'arco di tre mesi (marzo-giugno 2014). Risultati. Nel campione esaminato è emerso che la disinibizione, l'irritabilità e l'apatia sono i sintomi che provocano maggiore distress negli operatori, in senso assoluto. Inoltre, i risultati indicano che depressione e ansia recano un grado maggiore di distress nei pazienti sealer. Discussione e conclusione. Gli aspetti della disinibizione, dell'irritabilità e dell'apatia sono risultati più gravosi per gli operatori in quanto richiedono maggiore coinvolgimento nella relazione terapeutica. Sintomi ansiosi e depressivi risultano più gravosi nel gruppo dei sealer, segnalando minore tenuta della negazione della psicosi. I dati osservati sembrano provare che conoscere, differenziare e approfondire i diversi aspetti dello stile di recupero di ciascun paziente consente di stimare l'impegno gestionale fin dalla presa in carico e di ridurre il distress e il rischio di burnout degli operatori.

  12. Seagrass canopy photosynthetic response is a function of canopy density and light environment: a model for Amphibolis griffithii.

    PubMed

    Hedley, John D; McMahon, Kathryn; Fearns, Peter

    2014-01-01

    A three-dimensional computer model of canopies of the seagrass Amphibolis griffithii was used to investigate the consequences of variations in canopy structure and benthic light environment on leaf-level photosynthetic saturation state. The model was constructed using empirical data of plant morphometrics from a previously conducted shading experiment and validated well to in-situ data on light attenuation in canopies of different densities. Using published values of the leaf-level saturating irradiance for photosynthesis, results show that the interaction of canopy density and canopy-scale photosynthetic response is complex and non-linear, due to the combination of self-shading and the non-linearity of photosynthesis versus irradiance (P-I) curves near saturating irradiance. Therefore studies of light limitation in seagrasses should consider variation in canopy structure and density. Based on empirical work, we propose a number of possible measures for canopy scale photosynthetic response that can be plotted to yield isoclines in the space of canopy density and light environment. These plots can be used to interpret the significance of canopy changes induced as a response to decreases in the benthic light environment: in some cases canopy thinning can lead to an equivalent leaf level light environment, in others physiological changes may also be required but these alone may be inadequate for canopy survival. By providing insight to these processes the methods developed here could be a valuable management tool for seagrass conservation during dredging or other coastal developments.

  13. Seagrass Canopy Photosynthetic Response Is a Function of Canopy Density and Light Environment: A Model for Amphibolis griffithii

    PubMed Central

    Hedley, John D.; McMahon, Kathryn; Fearns, Peter

    2014-01-01

    A three-dimensional computer model of canopies of the seagrass Amphibolis griffithii was used to investigate the consequences of variations in canopy structure and benthic light environment on leaf-level photosynthetic saturation state. The model was constructed using empirical data of plant morphometrics from a previously conducted shading experiment and validated well to in-situ data on light attenuation in canopies of different densities. Using published values of the leaf-level saturating irradiance for photosynthesis, results show that the interaction of canopy density and canopy-scale photosynthetic response is complex and non-linear, due to the combination of self-shading and the non-linearity of photosynthesis versus irradiance (P-I) curves near saturating irradiance. Therefore studies of light limitation in seagrasses should consider variation in canopy structure and density. Based on empirical work, we propose a number of possible measures for canopy scale photosynthetic response that can be plotted to yield isoclines in the space of canopy density and light environment. These plots can be used to interpret the significance of canopy changes induced as a response to decreases in the benthic light environment: in some cases canopy thinning can lead to an equivalent leaf level light environment, in others physiological changes may also be required but these alone may be inadequate for canopy survival. By providing insight to these processes the methods developed here could be a valuable management tool for seagrass conservation during dredging or other coastal developments. PMID:25347849

  14. Canopy Vertical Spatial Scales which Constrain Biomass in a Tropical Forest at the Plot Level: Unifying Lidar and InSAR for Biomass Estimation

    NASA Astrophysics Data System (ADS)

    Treuhaft, R. N.; Goncalves, F. G.; Drake, J. B.; Chapman, B. D.; Dos Santos, J. R.; Dutra, L. V.; Graca, P. M.; Purcell, G. H.

    2009-12-01

    Structural remote sensing of forest biomass, using lidar and/or interferometric synthetic aperture radar (InSAR), often involves regressing field measured biomass against remotely sensed characteristics of the vertical density profile. Because spaceborne lidar or InSAR sensors will estimate structural characteristics averaged at the plot level (0.04-1 hectare), and because tropical forests contain 40% of the Earth’s forested biomass, this study focuses on the scales of vertical characteristics which best correlate with tropical forest biomass. This work suggests that the structural characteristics used in both lidar and InSAR biomass estimation, such as mean height or total height or height of median energy, are based on the behavior of Fourier vertical frequency components of vegetation density near zero frequency; that is, they are very low-spatial frequency characteristics of the vertical vegetation distribution. In this work, we ask which other vertical Fourier frequencies in lidar- or InSAR-produced structure metrics can best correlate with field biomass. Using lidar (LVIS) data from La Selva Biological Station, Costa Rica, taken in 2005, lidar canopy observations are Fourier transformed in the vertical direction to decompose into vertical frequency components. Each baseline of an InSAR observation, the complex coherence, is this Fourier transform of the canopy, if the ground contribution can be neglected. Using the qualitative similarity in vertical profiles seen by lidar, InSAR (at C-band, from AirSAR in 2004), and field measurements in the La Selva data, we produce the equivalent many (1000’s of) InSAR baselines from the lidar data and, using the lidar-simulated InSAR, determine the optimal spatial frequencies—baselines at DESDynI orbital altitudes for InSAR—which would estimate biomass in this wet tropical forest most accurately for either technique. For biomass ranging from 39-490 Mg/ha, regressing field biomass against some function of height

  15. Estimation of carotenoid content at the canopy scale using the carotenoid triangle ratio index from in situ and simulated hyperspectral data

    NASA Astrophysics Data System (ADS)

    Kong, Weiping; Huang, Wenjiang; Zhou, Xianfeng; Song, Xiaoyu; Casa, Raffaele

    2016-04-01

    Precise estimation of carotenoids (Car) content in plants, from remotely sensed data, is challenging due to their small proportion in the overall total pigment content and to the overlapping of spectral absorption features with chlorophyll (Chl) in the blue region of the spectrum. The use of narrow band vegetation indices (VIs) obtained from hyperspectral data has been considered an effective way to estimate Car content. However, VIs have proved to lack sensitivity to low or high Car content in a number of studies. In this study, the carotenoid triangle ratio index (CTRI), derived from the existing modified triangular vegetation index and a single band reflectance at 531 nm, was proposed and employed to estimate Car canopy content. We tested the potential of three categories of hyperspectral indices earlier proposed for Car, Chl, Car/Chl ratio estimation, and the new CTRI index, for Car canopy content assessment in winter wheat and corn. Spectral reflectance representing plant canopies were simulated using the PROSPECT and SAIL radiative transfer model, with the aim of analyzing saturation effects of these indices, as well as Chl effects on the relationship between spectral indices and Car content. The result showed that the majority of the spectral indices tested, saturated with the increase of Car canopy content above 28 to 64 μg/cm2. Conversely, the CTRI index was more robust and was linearly and highly sensitive to Car content in winter wheat and corn datasets, with coefficients of determination of 0.92 and 0.75, respectively. The corresponding root mean square error of prediction were 6.01 and 9.70 μg/cm2, respectively. Furthermore, the CTRI index did not show a saturation effect and was not greatly influenced by changes of Chl values, outperforming all the other indices tested. Estimation of Car canopy content using the CTRI index provides an insight into diagnosing plant physiological status and environmental stress.

  16. Geometric-optical Modeling of a Conifer Forest Canopy

    NASA Technical Reports Server (NTRS)

    Strahler, A. H. (Principal Investigator)

    1985-01-01

    The objective of this research is to explore how the geometry of trees in forest stands influences the reflectance of the forest as imaged from space. Most plant canopy modeling has viewed the canopy as an assemblage of plane-parallel layers on top of a soil surface. For these models, leaf angle distribution, leaf area index, and the angular transmittance and reflectance of leaves are the primary optical and geometric parameters. Such models are now sufficiently well developed to explain most of the variance in angular reflectance measurements observed from homogeneous plant canopies. However, forest canopies as imaged by airborne and spaceborne scanners exhibit considerable variance at quite a different scale. Brightness values vary strongly from one pixel to the next primarily as a function of the number of trees they contain. At this scale, the forest canopy is nonuniform and discontinuous. This research focuses on a discrete-element, geometric-optical view of the forest canopy.

  17. 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

  18. Using the Normalized Differential Wetness Index to Scale Leaf Area Index, Create Three-Dimensional Classification Maps, and Scale Seasonal Evapotranspiration Depletions in Canopies Along the Middle Rio Grande Riparian CorridorCorridor

    NASA Astrophysics Data System (ADS)

    McDonnell, D. E.; Cleverly, J. R.; Dahm, C. N.; Coonrod, J. A.

    2005-12-01

    This research creates temporally and spatially explicit data layers of vegetation, leaf area index (LAI), three dimensional (3D) vegetation classification maps, and seasonal evapotranspiration (ET) depletions along the middle Rio Grande riparian corridor. The first part of this work produces two dimensional (2D) classification maps of native and non-native canopy vegetation using temporal patterns and the decision tree classifier in ENVI 4.0 (Research Systems Inc. Boulder, Colorado). The second part of this work correlates the normalized differential wetness index (NDWI) with field measurements of plant area index (PAI), stem area index (SAI), and leaf area index (LAI) using the LAI-2000 Plant Canopy Analyzer (PCA) (LICOR Inc., Lincoln, Nebraska). SAI is measured in winter to capture only branches and stems. PAI is measured during the growing season. Field measurements taken within 10 days of image capture dates provide adequate correlations though the closer the dates the better the correlation. LAI represents the surface area of active green leafy vegetation. NDWI correlates with both PAI and estimated LAI in both Tamarisk chinensis and Populus deltoides ssp. Wislizeni sites better than the more traditional normalized differential vegetation index (NDVI). This study also suggests that winter PCA measurements approximate SAI which should be subtracted from PAI in woody vegetation like T. chinensis and Salix exigua stands. The results show that correcting for leaf geometry by multiplying T. chinensis areas with cylindrical cladophylls by pi and the remaining flat leaf vegetation by two yields the best relationship between NDWI and total LAI. The 2Dclassification maps can be placed on top of relief maps of LAI to produce 3D classification maps. The final part of this research scales ET from four 3D eddy covariance towers located in two T. chinensis and two P. deltoides study sites. ET is regressed with LAI, percent daylight (PD), and average hourly incoming net

  19. Improved snowmelt simulations with a canopy model forced with photo-derived direct beam canopy transmissivity

    NASA Astrophysics Data System (ADS)

    Musselman, Keith N.; Molotch, Noah P.; Margulis, Steven A.; Lehning, Michael; Gustafsson, David

    2012-10-01

    The predictive capacity of a physically based snow model to simulate point-scale, subcanopy snowmelt dynamics is evaluated in a mixed conifer forest, southern Sierra Nevada, California. Three model scenarios each providing varying levels of canopy structure detail were tested. Simulations of three water years initialized at locations of 24 ultrasonic snow depth sensors were evaluated against observations of snow water equivalent (SWE), snow disappearance date, and volumetric soil water content. When canopy model parameters canopy openness and effective leaf area index were obtained from satellite and literature-based sources, respectively, the model was unable to resolve the variable subcanopy snowmelt dynamics. When canopy parameters were obtained from hemispherical photos, the improvements were not statistically significant. However, when the model was modified to accept photo-derived time-varying direct beam canopy transmissivity, the error in the snow disappearance date was reduced by as much as one week and positive and negative biases in melt-season SWE and snow cover duration were significantly reduced. Errors in the timing of soil meltwater fluxes were reduced by 11 days on average. The optimum aggregated temporal model resolution of direct beam canopy transmissivity was determined to be 30 min; hourly averages performed no better than the bulk canopy scenarios and finer time steps did not increase overall model accuracy. The improvements illustrate the important contribution of direct shortwave radiation to subcanopy snowmelt and confirm the known nonlinear melt behavior of snow cover.

  20. A hotspot model for leaf canopies

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The hotspot effect, which provides important information about canopy structure, is modeled using general principles of environmental physics as driven by parameters of interest in remote sensing, such as leaf size, leaf shape, leaf area index, and leaf angle distribution. Specific examples are derived for canopies of horizontal leaves. The hotspot effect is implemented within the framework of the model developed by Suits (1972) for a canopy of leaves to illustrate what might occur in an agricultural crop. Because the hotspot effect arises from very basic geometrical principles and is scale-free, it occurs similarly in woodlands, forests, crops, rough soil surfaces, and clouds. The scaling principles advanced are also significant factors in the production of image spatial and angular variance and covariance which can be used to assess land cover structure through remote sensing.

  1. 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.

  2. Canopy Spectral Invariants. Part 1: A New Concept in Remote Sensing of Vegetation

    NASA Technical Reports Server (NTRS)

    Knyazikhin, Yuri; Schull, Mitchell A.; Xu, Liang; Myneni, Ranga B.; Samanta, Arindam

    2011-01-01

    The concept of canopy spectral invariants expresses the observation that simple algebraic combinations of leaf and canopy spectral reflectance become wavelength independent and determine two canopy structure specific variables the recollision and escape probabilities. These variables specify an accurate relationship between the spectral response of a vegetation canopy to incident solar radiation at the leaf and the canopy scale. They are sensitive to important structural features of the canopy such as forest cover, tree density, leaf area index, crown geometry, forest type and stand age. This paper presents the mathematical basis of the concept which is linked to eigenvalues and eigenvectors of the three-dimensional radiative transfer equation.

  3. Remote sensing of sagebrush canopy nitrogen

    USGS Publications Warehouse

    Mitchell, Jessica J.; Glenn, Nancy F.; Sankey, Temuulen T.; Derryberry, DeWayne R.; Germino, Matthew J.

    2012-01-01

    This paper presents a combination of techniques suitable for remotely sensing foliar Nitrogen (N) in semiarid shrublands – a capability that would significantly improve our limited understanding of vegetation functionality in dryland ecosystems. The ability to estimate foliar N distributions across arid and semi-arid environments could help answer process-driven questions related to topics such as controls on canopy photosynthesis, the influence of N on carbon cycling behavior, nutrient pulse dynamics, and post-fire recovery. Our study determined that further exploration into estimating sagebrush canopy N concentrations from an airborne platform is warranted, despite remote sensing challenges inherent to open canopy systems. Hyperspectral data transformed using standard derivative analysis were capable of quantifying sagebrush canopy N concentrations using partial least squares (PLS) regression with an R2 value of 0.72 and an R2 predicted value of 0.42 (n = 35). Subsetting the dataset to minimize the influence of bare ground (n = 19) increased R2 to 0.95 (R2 predicted = 0.56). Ground-based estimates of canopy N using leaf mass per unit area measurements (LMA) yielded consistently better model fits than ground-based estimates of canopy N using cover and height measurements. The LMA approach is likely a method that could be extended to other semiarid shrublands. Overall, the results of this study are encouraging for future landscape scale N estimates and represent an important step in addressing the confounding influence of bare ground, which we found to be a major influence on predictions of sagebrush canopy N from an airborne platform.

  4. Flow over a Ram-Air Parachute Canopy

    NASA Astrophysics Data System (ADS)

    Eslambolchi, Ali; Johari, Hamid

    2012-11-01

    The flow field over a full-scale, ram-air personnel parachute canopy was investigated numerically using a finite-volume flow solver coupled with the Spalart-Allmaras turbulence model. Ram-air parachute canopies resemble wings with arc-anhedral, surface protuberances, and an open leading edge for inflation. The rectangular planform canopy had an aspect ratio of 2.2 and was assumed to be rigid and impermeable. The chord-based Reynolds number was 3.2 million. Results indicate that the oncoming flow barely penetrates the canopy opening, and creates a large separation bubble below the lower lip of canopy. A thick boundary layer exists over the entire lower surface of the canopy. The flow over the upper surface of the canopy remains attached for an extended fraction of the chord. Lift increases linearly with angle of attack up to about 12 degrees. To assess the capability of lifting-line theory in predicting the forces on the canopy, the lift and drag data from a two-dimensional simulation of the canopy profile were extended using finite-wing expressions and compared with the forces from the present simulations. The finite-wing predicted lift and drag trends compare poorly against the full-span simulation, and the maximum lift-to-drag ratio is over-predicted by 36%. Sponsored by the US Army NRDEC.

  5. Arctic canopy photosynthetic efficiency enhanced under diffuse light, linked to a reduction in the fraction of the canopy in deep shade.

    PubMed

    Williams, Mathew; Rastetter, Edward B; Van der Pol, Laura; Shaver, Gaius R

    2014-06-01

    We investigated how radiation conditions within a tundra canopy were linked to canopy photosynthesis, and how this linkage explained photosynthetic sensitivity to sky conditions, that is total radiation and its diffuse fraction. We measured within canopy radiation at leaf scales and net CO2 exchanges at canopy scales, under varied total irradiance and diffuse fraction, in Alaskan shrub tundra. Normalised mean radiation profiles within canopies showed no significant differences with varied diffuse fractions. However, radiation density distribution was non-normal, being more unimodal under diffuse conditions and distinctly bimodal under direct sunlight. There was a nearly three-fold increase in the proportion of the canopy in deep shade under direct illumination, compared to diffuse conditions. Under diffuse conditions the canopy had higher light-use efficiency (LUE), resulting in up to 17% greater photosynthesis. The enhancement in LUE under diffuse illumination was not related to differences in the mean light profiles, but instead was due to significant shifts in the density distribution of light at leaf scales, in particular a reduced fraction of the canopy in deep shade under diffuse illumination. These results provide unique information for testing radiative transfer schemes in canopy models, and for better understanding canopy structure and trait variation within plant canopies.

  6. Spatial variability of throughfall and raindrops under a single canopy with different canopy structure

    NASA Astrophysics Data System (ADS)

    Nanko, Kazuki; Onda, Yuichi; Ito, Akane; Moriwaki, Hiromu

    2013-04-01

    To evaluate the spatial variability of throughfall amount, raindrops, and erosivity under a single canopy during calm meteorological conditions, indoor experiments were conducted using a 9.8-m-tall transplanted Japanese cypress (Chamaecyparis obtusa) and a large-scale rainfall simulator. Drop size distribution, drop velocity, and kinetic energy of throughfall varied spatially under a single canopy as did throughfall amount and rain rate. Compared with throughfall rain rate, the variability was similar in drop size distribution, lower in drop velocity, and higher in kinetic energy. The results suggest that the spatial distribution of throughfall amount was dominated by the canopy shape and position of branches inside the canopy, and thus the spatial distribution was correlated with the radial distance from the trunk. Throughfall amount and rate were lower at the midway point between the trunk and the canopy edge. Throughfall drop size indices (drop size distribution, drop velocity, and unit kinetic energy) varied spatially while did not differ significantly. On the other hand, time-specific throughfall kinetic energy was correlated with the radial distance from the trunk. The dependence the throughfall kinetic energy on the radial distance from the trunk was dominated by the spatial distribution of throughfall amount. The trend in the spatial distribution of throughfall revealed in this study will aid in modelling canopy water processes and in predicting soil erosion on the bare forest floor. The part of this study is published in Nanko et al. (2011, Agric. Forest. Meteorol. 151, 1173-1182).

  7. Comparison of three methods to derive canopy-scale flux measurements above a mixed oak and hornbeam forest in Northern Italy

    NASA Astrophysics Data System (ADS)

    Acton, William; Schallhart, Simon; Langford, Ben; Valach, Amy; Rantala, Pekka; Fares, Silvano; Carriero, Giulia; Mentel, Thomas; Tomlinson, Sam; Dragosits, Ulrike; Hewitt, Nicholas; Nemitz, Eiko

    2015-04-01

    Plants emit a wide range of Biogenic Volatile Organic Compounds (BVOCs) into the atmosphere. These BVOCs are a major source of reactive carbon into the troposphere and play an important role in atmospheric chemistry by, for example, acting as an OH sink and contributing to the formation of secondary organic aerosol. While the emission rates of some of these compounds are relatively well understood, large uncertainties are still associated with the emission estimates of many compounds. Here the fluxes and mixing ratios of BVOCs recorded during June/July 2012 over the Bosco Fontana forest reserve in northern Italy are reported and discussed, together with a comparison of three methods of flux calculation. This work was carried out as a part of the EC FP7 project ECLAIRE (Effects of Climate Change on Air Pollution and Response Strategies for European Ecosystems). The Bosco Fontana reserve is a semi natural deciduous forest dominated by Carpinus betulus (hornbeam), Quercus robur (pedunculate oak) and Quercus rubra (northern red oak). Virtual disjunct eddy covariance measurements made using Proton Transfer Reaction-Mass Spectrometry (PTR-MS) and Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS) were used to calculate fluxes and mixing ratios of BVOCs above the forest canopy at Bosco Fontana. BVOC mixing ratios were dominated by methanol with acetaldehyde, acetone, acetic acid, isoprene, the sum of methyl vinyl ketone and methacrolein, methyl ethyl ketone and monoterpenes also recorded. A large flux of isoprene was observed as well as significant fluxes of monoterpenes, methanol, acetaldehyde and methyl vinyl ketone / methacrolein. The fluxes recorded using the PTR-MS and PTR-ToF-MS showed good agreement. Comparison of the isoprene fluxes calculated using these instruments also agreed well with fluxes modelled using the MEGAN algorithms (Guenther et al. 2006). The detailed tree distribution maps for the forest at Bosco Fontana compiled by Dalponte et

  8. Within-canopy sampling of global irradiance to describe downwelling light distribution and infer canopy stratification in a broadleaf forest.

    PubMed

    Giuliani, Rita; Brown, Kim J

    2008-09-01

    A broadleaf mixed forest diversified through partial tree thinning was studied to identify expedient sampling and data analysis procedures to capture the heterogeneous within-canopy downward distribution of instantaneous global photosynthetic photon flux (PPF); to extract foliage structural properties from the acquired light values; and to compute statistics descriptive of the within-canopy light and leaf layer distributions. We sampled PPF at 1-m intervals along vertical gradients using a helium-filled balloon as a platform for a light sensor. A random method was used to identify the forest floor locations for the within-canopy balloon ascents. About 400 PPF measurements were recorded per vertical transect. For each PPF value, we computed, by inversion of the Monsi-Saeki model, the number of leaf strata cumulated along the sunbeam direction from the position where the light was measured. Variability in PPF and leaf layer at different vegetation scales was computed by non-parametric statistics. The methods were evaluated as appropriate for intra-canopy PPF sampling, particularly in an undisturbed canopy. The minimum number of vertical PPF profiles required to capture the within-canopy PPF variability was 9-10 (equivalent to about 4000 measurements). The reliability and sensitivity of the inversion of the Monsi-Saeki method were sufficient to capture the canopy structural differences between undisturbed and partially thinned forests. The proposed PPF canopy sampling and data analysis procedures provide a fast, reliable and inexpensive way to characterize tree crown structure, and to predict plant growth and forest dynamics and could be applied whenever vegetation absorbed radiation is a main driving force for forest canopy processes. The experimental light attenuation data and the extracted canopy leaf layer numbers could serve to corroborate canopy mechanistic models of radiative transfer and net primary production.

  9. Small-Footprint Lidar Estimations of Sagebrush Canopy Characteristics

    SciTech Connect

    Matthew Anderson; Ryan Hruska; Jessica Mitchell; Nancy Glenn

    2011-05-01

    Separating lidar returns for use in determining canopy height and shape in low-height vegetation is difficult because the vegetation canopy return is often close to the ground return in time and space. In addition, height underestimation is likely exacerbated in sparsely vegetated shrub ecosystems. This study compares lidar point-cloud data to sagebrush canopy characteristics measured in the field. It was determined that cumulative prediction error could account for as much as 35.6% of the average height and 37.4% of the average canopy area of shrubs sampled. When scaling from the individual shrub scale to coarser scales, prediction error averaged over a number of shrubs decreases as observation numbers increase. High density (in this case an average of 9.46 returns per m2), small footprint lidar (in this case a footprint diameter of 18 cm at nadir) may provide sufficient accuracy for characterizing sagebrush structure and cover and estimating biomass across landscapes.

  10. Canopy foliar nitrogen retrieved from airborne hyperspectral imagery by correcting for canopy structure effects

    NASA Astrophysics Data System (ADS)

    Wang, Zhihui; Skidmore, Andrew K.; Wang, Tiejun; Darvishzadeh, Roshanak; Heiden, Uta; Heurich, Marco; Latifi, Hooman; Hearne, John

    2017-02-01

    A statistical relationship between canopy mass-based foliar nitrogen concentration (%N) and canopy bidirectional reflectance factor (BRF) has been repeatedly demonstrated. However, the interaction between leaf properties and canopy structure confounds the estimation of foliar nitrogen. The canopy scattering coefficient (the ratio of BRF and the directional area scattering factor, DASF) has recently been suggested for estimating %N as it suppresses the canopy structural effects on BRF. However, estimation of %N using the scattering coefficient has not yet been investigated for longer spectral wavelengths (>855 nm). We retrieved the canopy scattering coefficient for wavelengths between 400 and 2500 nm from airborne hyperspectral imagery, and then applied a continuous wavelet analysis (CWA) to the scattering coefficient in order to estimate %N. Predictions of %N were also made using partial least squares regression (PLSR). We found that %N can be accurately retrieved using CWA (R2 = 0.65, RMSE = 0.33) when four wavelet features are combined, with CWA yielding a more accurate estimation than PLSR (R2 = 0.47, RMSE = 0.41). We also found that the wavelet features most sensitive to %N variation in the visible region relate to chlorophyll absorption, while wavelet features in the shortwave infrared regions relate to protein and dry matter absorption. Our results confirm that %N can be retrieved using the scattering coefficient after correcting for canopy structural effect. With the aid of high-fidelity airborne or upcoming space-borne hyperspectral imagery, large-scale foliar nitrogen maps can be generated to improve the modeling of ecosystem processes as well as ecosystem-climate feedbacks.

  11. [Effects of canopy shapes of grape on canopy microenvironment, leaf and fruit quality in greenhouse].

    PubMed

    Shi, Xiang-bin; Liu, Feng-zhi; Cheng, Cun-gang; Wang, Xiao-di; Wang, Bao-liang; Zheng, Xiao-cui; Wang, Hai-bo

    2015-12-01

    The effects of three canopy shapes, i.e., vertical canopy, V-shaped canopy and horizontal canopy, on canopy microenvironment, quality of leaves and fruits were studied in the 3-year-old grape 'Jingmi' grafted on ' Beta' in greenhouse. The results showed that gap fraction and openness of vertical canopy were significantly higher than that of V-shaped canopy and horizontal canopy, and leaf area index, light interception rate and canopy temperature difference between day and night were significantly lower than those of V-shaped canopy and horizontal canopy. There was no significant difference between the latter two treatments. The palisade thickness of V-shaped canopy was significantly greater than that of vertical canopy, and horizontal canopy was in the middle. The chlorophyll and carotenoid contents of V-shaped canopy were significantly higher than those of vertical canopy and horizontal canopy, and those in the latter two treatments had no significant difference. The fruit quality of V-shaped canopy was the best, and that of horizontal canopy was the worst. The results of GC-MS analysis showed that 29 types of volatile aroma compounds were detected in V-shaped canopy, but just 17 and 16 in vertical canopy and horizontal canopy, respectively. In V-shaped canopy, the characteristic aroma in grape 'Jingmi' was higher, except ethanol, trans-2- hexene-1-alcohol, 2-octyl ketone and formic acid ester. The linalool content in vertical canopy and V-shaped canopy was higher than that in horizontal canopy. The nerol content in V-shaped canopy was higher than that in vertical canopy and horizontal canopy, and the leaf alcohol content in V-shaped canopy and horizontal canopy was higher than that in vertical canopy. The citronellol was de-tected only in V-shaped canopy. In greenhouse, the fruit aroma of V-shaped canopy grape was stronger, and well reflected the variety characteristics.

  12. Canopy Research Network seeks input

    NASA Astrophysics Data System (ADS)

    In July 1993, the Canopy Research Network was established with a 2-year planning grant from the National Science Foundation to bring together forest canopy researchers, quantitative scientists, and computer specialists to establish methods for collecting, storing, analyzing, interpreting, and displaying three-dimensional data that relate to tree crowns and forest canopies. The CRN is now soliciting input from scientists in other fields who may have developed techniques and software to help obtain answers to questions that concern the complex three-dimensional structure of tree crowns and forest canopies. Over the next 3 years, the CRN plans to compile an array of research questions and issues requiring information on canopy structure, examine useful information models and software tools already in use in allied fields, and develop conceptual models and recommendations for the types and format of information and analyses necessary to answer research questions posed by canopy researchers.

  13. Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest.

    PubMed

    Ellsworth, D S; Reich, P B

    1993-11-01

    Canopy structure and light interception were measured in an 18-m tall, closed canopy deciduous forest of sugar maple (Acer saccharum) in southwestern Wisconsin, USA, and related to leaf structural characteristics, N content, and leaf photosynthetic capacity. Light attenuation in the forest occurred primarily in the upper and middle portions of the canopy. Forest stand leaf area index (LAI) and its distribution with respect to canopy height were estimated from canopy transmittance values independently verified with a combined leaf litterfall and point-intersect method. Leaf mass, N and A max per unit area (LMA, N/area and A max/area, respectively) all decreased continuously by over two-fold from the upper to lower canopy, and these traits were strongly correlated with cumulative leaf area above the leaf position in the canopy. In contrast, neither N concentration nor A max per unit mass varied significantly in relation to the vertical canopy gradient. Since leaf N concentration showed no consistent pattern with respect to canopy position, the observed vertical pattern in N/area is a direct consequence of vertical variation of LMA. N/area and LMA were strongly correlated with A max/area among different canopy positions (r(2)=0.81 and r(2)=0.66, respectively), indicating that vertical variation in area-based photosynthetic capacity can also be attributed to variation in LMA. A model of whole-canopy photosynthesis was used to show that observed or hypothetical canopy mass distributions toward higher LMA (and hence higher N/area) in the upper portions of the canopy tended to increase integrated daily canopy photosynthesis over other LMA distribution patterns. Empirical relationships between leaf and canopy-level characteristics may help resolve problems associated with scaling gas exchange measurements made at the leaf level to the individual tree crown and forest canopy-level.

  14. Plant canopy specular reflectance model

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Grant, L.

    1985-01-01

    A model is derived for the amount of light specularly reflected and polarized by a plant canopy. The model is based on the morphological and phenological characteristics of the canopy and upon the Fresnel equations of optics. The theory demonstrates that the specular reflectance of the plant canopy is a function of the angle of incidence and potentially contains information to help discriminate between species. The theory relates the specular reflectance to botanical condition of the canopy - to factors such as development stage, plant vigor, and leaf area index (LAI).

  15. Predicting Ecosystem-scale CO2 Fluxes and Vegetation Biophysical Parameters of a Subalpine Grassland with Continuous Canopy Hyperspectral Reflectance Measurements.

    NASA Astrophysics Data System (ADS)

    Sakowska, K.; Vescovo, L.; Marcolla, B.; Cavagna, M.; Zampedri, R.; Gianelle, D.

    2015-12-01

    This study investigates the potential of the ASD-WhiteRef system for monitoring CO2 fluxes and vegetation biophysical parameters (such as e.g. fraction of absorbed photosynthetically active radiation - fapar, canopy total chlorophyll content - TotChl). The ASD-WhiteRef is an automated system designed for continuous and unattended acquisition of radiometric data using an ASD FieldSpec Pro spectroradiometer. The ASD-WhiteRef system was installed in May 2013 at the EC tower (at a height of 6 m, with a field of view of 25°) of the FLUXNET Monte Bondone site (IT-MBo), which is a representative of a typical extensively-managed, low-productive meadow of the Italian Alps. Vegetation hyperspectral reflectance and EC observations were collected on a continuous basis for three growing seasons covering periods of extreme weather conditions (both hot/dry and rainy periods), while fapar and TotChl were determined periodically (at around weekly intervals) during two growing seasons at different vegetation development stages by means of line quantum sensors and UV-VIS spectroscopy method, respectively. In order to characterize the interannual dynamics in grassland CO2 fluxes three approaches were used: i) linear regression between CO2 fluxes and spectral vegetation indices - VI (model 1); ii) linear regression between CO2 fluxes and a product of VI and PAR (model 2), iii) partial least squares regression (PLSR) using simultaneously the full set of ASD-WhiteRef reflectance spectra (2151 bands, 350-2500 nm) to predict CO2 fluxes. In addition, model i) and model iii) were tested also for predicting fapar and TotChl variability. The range of presented VIs contained both VIs derived from the Sentinel-2 bands simulation and VIs calculated using all two-band combinations of wavelengths available from the ASD-WhiteRef hyperspectral dataset. The findings of the study highlight the potential of vegetation spectroscopy to monitor temporal variations in key drivers of photosynthesis process

  16. Medium term ecohydrological response of peatland bryophytes to canopy disturbance

    NASA Astrophysics Data System (ADS)

    Leonard, Rhoswen; Kettridge, Nick; Krause, Stefan; Devito, Kevin; Granath, Gustaf; Petrone, Richard; Mandoza, Carl; Waddington, James Micheal

    2016-04-01

    Canopy disturbance in northern forested peatlands is widespread. Canopy changes impact the ecohydrological function of moss and peat, which provide the principal carbon store within these carbon rich ecosystems. Different mosses have contrasting contributions to carbon and water fluxes (e.g. Sphagnum fuscum and Pleurozium schreberi) and are strongly influenced by canopy cover. As a result, changes in canopy cover lead to long-term shifts in species composition and associated ecohydrological function. Despite this, the medium-term response to such disturbance, the associated lag in this transition to a new ecohydrological and biogeochemical regime, is not understood. Here we investigate this medium term ecohydrological response to canopy removal using a randomised plot design within a north Albertan peatland. We show no significant ecohydrological change in treatment plots four years after canopy removal. Notably, Pleurozium schreberi and Sphagnum fuscum remained within respective plots post treatment and there was no significant difference in plot resistance to evapotranspiration or carbon exchange. Our results show that canopy removal alone has little impact on bryophyte ecohydrology in the short/medium term. This resistance to disturbance contrasts strongly with dramatic short-term changes observed within mineral soils suggesting that concurrent shifts in the large scale hydrology induced within such disturbances are necessary to cause rapid ecohydrological transitions. Understanding this lagged response is critical to determine the decadal response of carbon and water fluxes in response to disturbance and the rate at which important medium term ecohydrological feedbacks are invoked.

  17. Canopy temperature and cotton performance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abstract The temperature of a cotton canopy is a useful indicator of both the metabolic state and water status of the crop. Recent advances in equipment have resulted in reductions in the cost and complexity of near continuous canopy temperature monitoring. Measurements on a seasonal timeframe at a ...

  18. Canopy for VERAView Installation Guide

    SciTech Connect

    Lee, Ronald W.

    2016-09-12

    With the addition of the 3D volume slicer widget, VERAView now relies on Mayavi and its dependents. Enthought's Canopy Python environment provides everything VERAView needs, and pre-built Canopy versions for Windows, Mac OSX, and Linux can be downloaded.

  19. NEIGHBORHOOD SCALE AIR QUALITY MODELING IN HOUSTON USING URBAN CANOPY PARAMETERS IN MM5 AND CMAQ WITH IMPROVED CHARACTERIZATION OF MESOSCALE LAKE-LAND BREEZE CIRCULATION

    EPA Science Inventory

    Advanced capability of air quality simulation models towards accurate performance at finer scales will be needed for such models to serve as tools for performing exposure and risk assessments in urban areas. It is recognized that the impact of urban features such as street and t...

  20. 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...

  1. Three-dimensional modeling of canopy flow in complex terrain

    NASA Astrophysics Data System (ADS)

    Xu, X.; Yi, C.; Montagnani, L.

    2013-12-01

    Flows within and just above forest canopy over mountainous terrain are most complicated, which substantially influence the biosphere-atmosphere interaction of mass and energy. Due to the significant spatial variation, canopy flow in complex terrain is poorly understood based on the point-based tower measurement. We employ numerical model integrated with biogenic CO2 process to examine the impacts of topography, canopy structure, and synoptic atmospheric motion on canopy flow and associated CO2 transport in an alpine forest, with special focus on stable nocturnal condition when biogenic CO2 emission is active. Our model prediction is in better agreement with tower measurements when background synoptic wind is present, which leads to better larger-scale mixing, while local slope flow is just thermal-driven in the modeled domain by ignorance of surround mountain-valley. Our results show that large-scale synoptic wind is modified by local slope-canopy flow within and just above canopy. As the synoptic wind is down-slope (Figure 1a), recirculation is formed on the downwind slope with cool air and high accumulation of CO2 in front of tall and dense vegetation. As the synoptic wind is up-slope(Figure 1b), canopy flow at the higher elevation of the slope is in the same direction of synoptic wind, while canopy flow at the lower part of the slope blows down-slope. The upslope wind causes better mixing in the canopy and leads to smaller CO2 accumulation just close to the slope surface. The local down-slope wind (Figure 1c) causes rich and deep CO2 build-up in the downwind direction on the lower slope. Our numerical performance has demonstrated that three-dimensional CFD approach is a useful tool to understanding relationships between tower-point measurements and surrounding's field distributions. Acknowledgement: This research was supported by NSF Grants ATM-0930015, CNS-0958379 & CNS-0855217, PSC-CUNY ENHC-42-64 & CUNY HPCC. Figure 1 CO2 distribution within and just above

  2. Estimating Canopy Dark Respiration for Crop Models

    NASA Technical Reports Server (NTRS)

    Monje Mejia, Oscar Alberto

    2014-01-01

    Crop production is obtained from accurate estimates of daily carbon gain.Canopy gross photosynthesis (Pgross) can be estimated from biochemical models of photosynthesis using sun and shaded leaf portions and the amount of intercepted photosyntheticallyactive radiation (PAR).In turn, canopy daily net carbon gain can be estimated from canopy daily gross photosynthesis when canopy dark respiration (Rd) is known.

  3. Forest Canopy Gap Distributions in the Southern Peruvian Amazon

    PubMed Central

    Asner, Gregory P.; Kellner, James R.; Kennedy-Bowdoin, Ty; Knapp, David E.; Anderson, Christopher; Martin, Roberta E.

    2013-01-01

    Canopy gaps express the time-integrated effects of tree failure and mortality as well as regrowth and succession in tropical forests. Quantifying the size and spatial distribution of canopy gaps is requisite to modeling forest functional processes ranging from carbon fluxes to species interactions and biological diversity. Using high-resolution airborne Light Detection and Ranging (LiDAR), we mapped and analyzed 5,877,937 static canopy gaps throughout 125,581 ha of lowland Amazonian forest in Peru. Our LiDAR sampling covered a wide range of forest physiognomies across contrasting geologic and topographic conditions, and on depositional floodplain and erosional terra firme substrates. We used the scaling exponent of the Zeta distribution (λ) as a metric to quantify and compare the negative relationship between canopy gap frequency and size across sites. Despite variable canopy height and forest type, values of λ were highly conservative (λ mean  = 1.83, s  = 0.09), and little variation was observed regionally among geologic substrates and forest types, or at the landscape level comparing depositional-floodplain and erosional terra firme landscapes. λ-values less than 2.0 indicate that these forests are subjected to large gaps that reset carbon stocks when they occur. Consistency of λ-values strongly suggests similarity in the mechanisms of canopy failure across a diverse array of lowland forests in southwestern Amazonia. PMID:23613748

  4. Forest canopy gap distributions in the southern Peruvian Amazon.

    PubMed

    Asner, Gregory P; Kellner, James R; Kennedy-Bowdoin, Ty; Knapp, David E; Anderson, Christopher; Martin, Roberta E

    2013-01-01

    Canopy gaps express the time-integrated effects of tree failure and mortality as well as regrowth and succession in tropical forests. Quantifying the size and spatial distribution of canopy gaps is requisite to modeling forest functional processes ranging from carbon fluxes to species interactions and biological diversity. Using high-resolution airborne Light Detection and Ranging (LiDAR), we mapped and analyzed 5,877,937 static canopy gaps throughout 125,581 ha of lowland Amazonian forest in Peru. Our LiDAR sampling covered a wide range of forest physiognomies across contrasting geologic and topographic conditions, and on depositional floodplain and erosional terra firme substrates. We used the scaling exponent of the Zeta distribution (λ) as a metric to quantify and compare the negative relationship between canopy gap frequency and size across sites. Despite variable canopy height and forest type, values of λ were highly conservative (λ mean  = 1.83, s  = 0.09), and little variation was observed regionally among geologic substrates and forest types, or at the landscape level comparing depositional-floodplain and erosional terra firme landscapes. λ-values less than 2.0 indicate that these forests are subjected to large gaps that reset carbon stocks when they occur. Consistency of λ-values strongly suggests similarity in the mechanisms of canopy failure across a diverse array of lowland forests in southwestern Amazonia.

  5. Simulations of tropical rainforest albedo: is canopy wetness important?

    PubMed

    Yanagi, Silvia N M; Costa, Marcos H

    2011-12-01

    Accurate information on surface albedo is essential for climate modelling, especially for regions such as Amazonia, where the response of the regional atmospheric circulation to the changes on surface albedo is strong. Previous studies have indicated that models are still unable to correctly reproduce details of the seasonal variation of surface albedo. Therefore, it was investigated the role of canopy wetness on the simulated albedo of a tropical rainforest by modifying the IBIS canopy radiation transfer code to incorporate the effects of canopy wetness on the vegetation reflectance. In this study, simulations were run using three versions of the land surface/ecosystem model IBIS: the standard version, the same version recalibrated to fit the data of albedo on tropical rainforests and a modified version that incorporates the effects of canopy wetness on surface albedo, for three sites in the Amazon forest at hourly and monthly scales. The results demonstrated that, at the hourly time scale, the incorporation of canopy wetness on the calculations of radiative transfer substantially improves the simulations results, whereas at the monthly scale these changes do not substantially modify the simulated albedo.

  6. A comparative quadrant analysis of turbulence in a plant canopy

    NASA Astrophysics Data System (ADS)

    Yue, Wusi; Meneveau, Charles; Parlange, Marc B.; Zhu, Weihong; van Hout, René; Katz, Joseph

    2007-05-01

    Large-eddy simulation (LES) of turbulence in plant canopies has traditionally been validated using bulk statistical quantities such as mean velocity and variance profiles. However, turbulent exchanges between a plant canopy and the atmosphere are dominated by large-scale coherent structures, and therefore LES must also be validated using statistical tools that are sensitive to details of coherent structures. In this study, LES and measurements using particle image velocimetry (PIV) are compared near the top of the canopy by means of a quadrant-hole analysis of turbulent kinetic energy, vorticity, and dissipation rate. The LES resolves coarse features of individual corn plants and uses the Lagrangian scale-dependent dynamic subgrid model. At the measurement location, there is good agreement between the LES predictions and the field data in terms of most conditionally sampled quantities, confirming the applicability of LES for fundamental studies of vegetation-air interactions and coherent structures. The simulation results confirm that sweeps (the fourth-quadrant events) contribute the largest fraction of turbulent kinetic energy, vorticity, and dissipation rate inside the plant canopy. The magnitudes of the vorticity and dissipation rate at the top of the canopy are highest in the first quadrant (rare events of outward interactions).

  7. Impacts of Canopy Structure on Water, Energy and Carbon Exchange in a Loblolly Pine Forest in Southeast USA

    NASA Astrophysics Data System (ADS)

    Song, C.; Band, L. E.; Randolph, A.; Oren, R.; Katul, G.

    2004-12-01

    Forest ecosystems play a key role in water, energy and carbon exchange between the terrestrial ecosystems and the atmosphere. One of the major factors that govern the rate of exchange of these fluxes is canopy structure. However, most ecosystem models simulating water, energy and carbon exchange of forest ecosystems with the atmosphere are based on a simplified canopy structure, where the forest canopy is assumed to be a turbid medium with leaves uniformly distributed within the canopy as particles of infinitesimal size, and light propagates through the canopy following an exponential decay. In reality, there are gaps of various sizes within the forest canopy. Lights passing through the gaps are not attenuated creating sunflecks on the forest floor. In this study, we represent the canopy of a loblolly pine stand as an assembly of individual crowns with gaps between and within the crowns. Gaps in the canopy are estimated based on statistics of canopy structure. Such a representation of canopy structure relinquishes the need for the sizes and locations of each tree as are needed in three-dimensional radiation transfer models, making it possible to account for the landscape canopy structure in ecosystem models. The loblolly pine stand is located in the Blackwood Division of Duke Forest, and is an AmeriFlux site where water, energy and carbon exchanges with the atmosphere have been monitored with eddy-covariance instruments since 1997. We simulated the exchanges of these scalars using the RHESSys model with gaps in the canopy estimated from the statistics of canopy structure. Comparision with data from the eddy-covariance instruments shows that replacing a turbid medium canopy with a gapy canopy in RHESSys significantly improved simulation of these fluxes through the forest ecosystem on a daily and weekly time scale. The results identify improper canopy representation in models as a source of uncertainty in estimates of regional water, energy and carbon cycles of the

  8. Estimation of canopy parameters for inhomogeneous vegetation canopies from reflectance data. III - TRIM: A model for radiative transfer in heterogeneous three-dimensional canopies

    NASA Technical Reports Server (NTRS)

    Goel, Narendra S.; Grier, Toby

    1988-01-01

    A model for radiative transfer in heterogeneous three-dimensional canopies such as those found in forests is proposed. Its use in estimating important biophysical variables such as leaf area index and canopy architecture from bidirectional canopy reflectance data is discussed. The model and its use in estimating canopy parameters through its inversion are validated with measured canopy reflectance data for corn canopies.

  9. Soybean canopy reflectance modeling data sets

    NASA Technical Reports Server (NTRS)

    Ranson, K. J.; Biehl, L. L.; Daughtry, C. S. T.

    1984-01-01

    Numerous mathematical models of the interaction of radiation with vegetation canopies have been developed over the last two decades. However, data with which to exercise and validate these models are scarce. During three days in the summer of 1980, experiments are conducted with the objective of gaining insight about the effects of solar illumination and view angles on soybean canopy reflectance. In concert with these experiment, extensive measurements of the soybean canopies are obtained. This document is a compilation of the bidirectional reflectance factors, agronomic, characteristics, canopy geometry, and leaf, stem, and pod optical properties of the soybean canopies. These data sets should be suitable for use with most vegetation canopy reflectance models.

  10. EFFECTS OF EELGRASS ZOSTRA MARINA CANOPIES ON FLOW AND TRANSPORT

    EPA Science Inventory

    Ecological effects of the interaction between submerged aquatic vegetation and currents depend on the plants and their associated organisms as well as the large-scale transport of dissolved and suspended constituents near the canopy. Mathematical models for airflow within plant c...

  11. IMPLEMENTATION OF AN URBAN CANOPY PARAMETERIZATION IN MM5

    EPA Science Inventory

    The Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) (Grell et al. 1994) has been modified to include an urban canopy parameterization (UCP) for fine-scale urban simulations (~1-km horizontal grid spacing). The UCP accounts for drag ...

  12. Canopy light transmittance in Douglas-fir--western hemlock stands.

    PubMed

    Parker, Geoffrey G; Davis, Melinda M; Chapotin, Saharah Moon

    2002-02-01

    We measured vertical and horizontal variation in canopy transmittance of photosynthetically active radiation in five Pseudotsuga menziesii (Mirb.) Franco-Tsuga heterophylla (Raf.) Sarg. (Douglas-fir-western hemlock) stands in the central Cascades of southern Washington to determine how stand structure and age affect the forest light environment. The shape of the mean transmittance profile was related to stand height, but height of mean maximum transmittance was progressively lower than maximum tree height in older stands. The vertical rate of attenuation declined with stand age in both the overstory and understory. A classification of vertical light zones based on the mean and variance of transmittance showed a progressive widening of the bright (low variance and high mean) and transition (high variance and rapid vertical change) zones in older stands, whereas the dim zone (low variance and mean) narrowed. The zone of maximum canopy surface area in height profiles, estimated by inversion of transmittance profiles, changed from relatively high in the canopy in most young stands ("top-heavy") to lower in the canopy in older stands ("bottom-heavy"). In the understory, all stands had similar mean transmittances, but the spatial scale of variation increased with stand age and increasing crown size. The angular distribution of openness was similar in all stands, though the older stands were less open at all angles than the younger stands. Understory openness was generally unrelated to transmittance in the canopy above. Whole-canopy leaf area indices, estimated using three methods of inverting light measurements, showed little correspondence across methods. The observed patterns in light environment are consistent with structural changes occurring during stand development, particularly the diversification of crowns, the creation of openings of various sizes and the elaboration of the outer canopy surface. The ensemble of measurements has potential use in distinguishing

  13. 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.

  14. Canopy Interception for a Tallgrass Prairie under Juniper Encroachment.

    PubMed

    Zou, Chris B; Caterina, Giulia L; Will, Rodney E; Stebler, Elaine; Turton, Donald

    2015-01-01

    Rainfall partitioning and redistribution by canopies are important ecohydrological processes underlying ecosystem dynamics. We quantified and contrasted spatial and temporal variations of rainfall redistribution for a juniper (Juniperus virginiana, redcedar) woodland and a tallgrass prairie in the south-central Great Plains, USA. Our results showed that redcedar trees had high canopy storage capacity (S) ranging from 2.14 mm for open stands to 3.44 mm for closed stands. The canopy funneling ratios (F) of redcedar trees varied substantially among stand type and tree size. The open stands and smaller trees usually had higher F values and were more efficient in partitioning rainfall into stemflow. Larger trees were more effective in partitioning rainfall into throughfall and no significant changes in the total interception ratios among canopy types and tree size were found. The S values were highly variable for tallgrass prairie, ranging from 0.27 mm at early growing season to 3.86 mm at senescence. As a result, the rainfall interception by tallgrass prairie was characterized by high temporal instability. On an annual basis, our results showed no significant difference in total rainfall loss to canopy interception between redcedar trees and tallgrass prairie. Increasing structural complexity associated with redcedar encroachment into tallgrass prairie changes the rainfall redistribution and partitioning pattern at both the temporal and spatial scales, but does not change the overall canopy interception ratios compared with unburned and ungrazed tallgrass prairie. Our findings support the idea of convergence in interception ratio for different canopy structures under the same precipitation regime. The temporal change in rainfall interception loss from redcedar encroachment is important to understand how juniper encroachment will interact with changing rainfall regime and potentially alter regional streamflow under climate change.

  15. Canopy Interception for a Tallgrass Prairie under Juniper Encroachment

    PubMed Central

    Zou, Chris B.; Caterina, Giulia L.; Will, Rodney E.; Stebler, Elaine; Turton, Donald

    2015-01-01

    Rainfall partitioning and redistribution by canopies are important ecohydrological processes underlying ecosystem dynamics. We quantified and contrasted spatial and temporal variations of rainfall redistribution for a juniper (Juniperus virginiana, redcedar) woodland and a tallgrass prairie in the south-central Great Plains, USA. Our results showed that redcedar trees had high canopy storage capacity (S) ranging from 2.14 mm for open stands to 3.44 mm for closed stands. The canopy funneling ratios (F) of redcedar trees varied substantially among stand type and tree size. The open stands and smaller trees usually had higher F values and were more efficient in partitioning rainfall into stemflow. Larger trees were more effective in partitioning rainfall into throughfall and no significant changes in the total interception ratios among canopy types and tree size were found. The S values were highly variable for tallgrass prairie, ranging from 0.27 mm at early growing season to 3.86 mm at senescence. As a result, the rainfall interception by tallgrass prairie was characterized by high temporal instability. On an annual basis, our results showed no significant difference in total rainfall loss to canopy interception between redcedar trees and tallgrass prairie. Increasing structural complexity associated with redcedar encroachment into tallgrass prairie changes the rainfall redistribution and partitioning pattern at both the temporal and spatial scales, but does not change the overall canopy interception ratios compared with unburned and ungrazed tallgrass prairie. Our findings support the idea of convergence in interception ratio for different canopy structures under the same precipitation regime. The temporal change in rainfall interception loss from redcedar encroachment is important to understand how juniper encroachment will interact with changing rainfall regime and potentially alter regional streamflow under climate change. PMID:26544182

  16. Influence of Zostera marina canopies on unidirectional flow, hydraulic roughness and sediment movement

    NASA Astrophysics Data System (ADS)

    Lefebvre, A.; Thompson, C. E. L.; Amos, C. L.

    2010-09-01

    Seagrasses develop extensive or patchy underwater meadows in coastal areas around the world, forming complex, highly productive ecosystems. Seagrass canopies exert strong effects on water flow inside and around them, thereby affecting flow structure, sediment transport and benthic ecology. The influence of Zostera marina canopies on flow velocity, turbulence, hydraulic roughness and sediment movement was evaluated through laboratory experiments in 2 flumes and using live Z. marina and a mobile sand bed. Profiles of instantaneous velocities were measured and sediment movement was identified upstream, within and downstream of patches of different sizes and shoot density and at different free-stream velocities. Flow structure was characterised by time-averaged velocity, turbulence intensity and Turbulent Kinetic Energy (TKE). When velocity data were available above the canopy, they were fitted to the Law of the Wall and shear velocities and roughness lengths were calculated. When a seagrass canopy was present, three layers were distinguishable in the water column: (1) within canopy represented by low velocities and high turbulence; (2) transition zone around the height of the canopy, where velocities increased, turbulence decreased and TKE was high; and (3) above canopy where velocities were equal or higher than free-stream velocities and turbulence and TKE were lower than below. Shoot density and patch-width influenced this partitioning of the flow when the canopy was long enough (based on flume experiments, at least more than 1 m-long). The enhanced TKE observed at the canopy/water interface suggests that large-scale turbulence is generated at the canopy surface. These oscillations, likely to be related to the canopy undulations, are then broken down within the canopy and high-frequency turbulence takes place near the bed. This turbulence 'cascade' through the canopy may have an important impact on biogeochemical processes. The velocity above the canopy generally

  17. The Properties of Sunflecks in a Flexible Plant Canopy, and Their Relationship to Turbulence

    NASA Astrophysics Data System (ADS)

    Tong, Hongliang

    1992-01-01

    The properties of sunflecks within alfalfa canopies and their relationship to atmospheric turbulence above the canopies were quantified. Transient light environment in an alfalfa canopy was observed being highly dynamic, lasting from fractions of seconds to minutes in duration. Both probabilistic analysis and autocorrelation analysis indicate that the mean duration of sunflecks ranges from 0.1 to 1.6 seconds with most frequent sunflecks having durations of 0.2 to 0.8 seconds. Power spectral analysis suggests that winds have significant influences on the properties of sunflecks in the alfalfa canopies. Calculated power spectra of photosynthetically active radiation (PAR) time series within the canopies show clear linear relationships with the mean wind speeds and the spectra of vertical-velocity measured 1.5 m above the canopies. This implies that the properties of sunflecks may be evaluated from the measured properties of turbulence. Results also show that the total variances of the PAR time series increase with increased wind, and the enhancement in variance is more apparent in lower canopy as wind increases. This suggests that the wind-induced movement of plants can reduce the vertical light gradient with canopy depth. Also, frequency distributions of sunfleck irradiance were found to disobey the normal distribution laws, but to be skewed. The skewness is affected by both canopy depth and wind. Smaller canopy depth and stronger winds can cause larger skewness. An attempt was made to use the beta distributions to simulate the PAR irradiance distributions, and the simulated results seem acceptable. The PAR spatial series were also characterized. Spatial power spectral analysis suggests that small-scale spatial heterogeneity is a predominant feature of light environment in alfalfa canopies, and lower solar elevation seems to decrease the spatial variability. In addition, similar analyses were conducted for an aspen canopy. The power spectra of the PAR time series

  18. Emergence time in forest bats: the influence of canopy closure

    NASA Astrophysics Data System (ADS)

    Russo, Danilo; Cistrone, Luca; Jones, Gareth

    2007-01-01

    The role of the forest canopy in protecting bats roosting in forest from predators is poorly known. We analysed the effect of canopy closure on emergence time in Barbastella barbastellus in a mountainous area of central Italy. We used radio-tracking to locate roosts and filmed evening emergence. Comparisons were made between roosts in open areas and those in dense forest. Median emergence time and illuminance were correlated. Moreover, from pregnancy to late lactation bats emerged progressively earlier, probably because of the exceptionally high wing loading affecting pregnant bats and the high energy demand of lactation. A significant influence of canopy closure on median emergence time was revealed after adjusting for the effects of light and reproductive state. Bats in open habitat emerged later than those roosting beneath closed canopy. In cluttered habitats, predators relying on vision may find it more difficult to detect and catch bats at light levels which would offer more chances of success when attacking prey in open habitats. Bats in dense forest are less vulnerable to predators and may take advantage of an earlier emergence by prolonging foraging. Although more vulnerable, lactating females roosting at open sites may benefit from warmer roosting conditions. Roosts in dense forest may be preferred under intense predation pressure. Forest management should favour canopy heterogeneity to provide bats with a range of roosting conditions. Our work emphasises the role of a fine-grained spatial scale in the roosting ecology of forest bats.

  19. Canopy Cover Predictions using Ground Observations and Remotely Sensed Data

    NASA Technical Reports Server (NTRS)

    Dungan, Jennifer L.

    1999-01-01

    Maps of vegetation status are needed at many scales, from the field level to monitor ecosystem condition to the global level to understand the carbon cycle. Status is quantified by such variables as leaf area index, biomass, and fraction of canopy cover. Current methods of predicting vegetation variables use remote sensing data to provide a spatially exhaustive data source. In a study in western Montana, several hundred ground observations made by the US Forest Service on tenth-acre conifer plots were used to develop aspatial regression and geostatistical prediction models. Normalized Difference Vegetation Index (NDVI) values from Landsat Thematic Mapper images were used as ancillary data. These models were then used to predict canopy cover at unsampled locations in a 97 square kilometer region on the boundary of the Flathead National Forest and the Bob Marshall Wilderness. Independent data from two dates six years apart were used for validation. Given the assumption that actual canopy cover remained relatively unchanged within this time period, partial validation can be achieved by measuring the correspondence of the two maps. This criterion results in ranking the aspatial regression maps as less accurate than the geostatistically generated maps. The geostatistical approach emphasizes ground measurements more heavily than does aspatid regression. Geostatistical simulations of canopy cover also provide a means of describing uncertainty about the patterns of canopy cover.

  20. Canopy effects on snow sublimation from a central Arizona Basin

    NASA Astrophysics Data System (ADS)

    Svoma, Bohumil M.

    2017-01-01

    Guided by 30 m terrain and forest cover data, snow sublimation from the Salt River basin in the Southwest U.S. is simulated for years 2008 (wet year) and 2007 (dry year). Downscaled meteorological input correlates well (r 0.80) with independent observations at AmeriFlux sites. Additionally, model correlation and bias with eddy-covariance vapor flux observations is comparable to previous localized modeling efforts. Upon a 30% reduction in effective leaf area index, canopy sublimation decreases by 1.29 mm (27.0%) and 1.05 mm (23.0%) at the basin scale for the 2008 and 2007 simulations, respectively. Ground sublimation decreases 0.72 mm (4.75%) in 2008 and only 0.17 mm (1.5%) in 2007. Canopy snow-holding capacity and frequent unloading events at lower elevations limit the variability in canopy sublimation from wet year to dry year at the basin scale. The greater decrease in snowpack sublimation in the wet year is partly due to decreased longwave radiation from the canopy reduction over a more extensive snowpack than the dry year. This decrease overcomes the increased solar radiation and wind speed during winter. A second factor is that a greater extent of the snowpack persisted into spring in 2008 than 2007, and the large increase in shortwave flux upon canopy reduction increases melt rates, reducing duration. Only in heavily forested high elevations (>2900 m above sea level) in 2008 does the snowpack persist long enough into spring to result in increased ground sublimation upon canopy reduction. As forest cover change can occur rapidly, these results are critical from water resource and ecosystem function perspectives.

  1. 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

  2. Amazonian functional diversity from forest canopy chemical assembly.

    PubMed

    Asner, Gregory P; Martin, Roberta E; Tupayachi, Raul; Anderson, Christopher B; Sinca, Felipe; Carranza-Jiménez, Loreli; Martinez, Paola

    2014-04-15

    Patterns of tropical forest functional diversity express processes of ecological assembly at multiple geographic scales and aid in predicting ecological responses to environmental change. Tree canopy chemistry underpins forest functional diversity, but the interactive role of phylogeny and environment in determining the chemical traits of tropical trees is poorly known. Collecting and analyzing foliage in 2,420 canopy tree species across 19 forests in the western Amazon, we discovered (i) systematic, community-scale shifts in average canopy chemical traits along gradients of elevation and soil fertility; (ii) strong phylogenetic partitioning of structural and defense chemicals within communities independent of variation in environmental conditions; and (iii) strong environmental control on foliar phosphorus and calcium, the two rock-derived elements limiting CO2 uptake in tropical forests. These findings indicate that the chemical diversity of western Amazonian forests occurs in a regionally nested mosaic driven by long-term chemical trait adjustment of communities to large-scale environmental filters, particularly soils and climate, and is supported by phylogenetic divergence of traits essential to foliar survival under varying environmental conditions. Geographically nested patterns of forest canopy chemical traits will play a role in determining the response and functional rearrangement of western Amazonian ecosystems to changing land use and climate.

  3. A review of crop canopy reflectance models

    NASA Technical Reports Server (NTRS)

    Goel, N. S. (Principal Investigator)

    1982-01-01

    Various models for calculating crop canopy reflectance, in the visible and infrared wavelengths, from the optical and geometrical properties of a canopy and its constituents are reviewed. The radiative transfer equation is discussed as well as both analytical and numerical crop reflectance models which are manifestations of the solution of this equation. Recommendations are made for further work in modeling of canopy reflectance.

  4. Spatial and temporal variability of canopy GPP within a flux tower footprint

    NASA Astrophysics Data System (ADS)

    Garrity, S. R.; Vierling, L. A.

    2009-12-01

    Gross Primary Productivity (GPP) of plant canopies is strongly related to absorbed photosynthetically active radiation (APAR) and thus canopy structure. Short term canopy GPP responds to variable environmental conditions through alterations in the efficiency with which APAR is used to assimilate carbon and is thus also dependent on accessory pigment ratios and pool sizes. We used spatially distributed measurements of whole canopy transmitted radiation to better understand diurnal and seasonal dynamics of GPP within a flux tower footprint. Our instruments measured transmitted radiation in the Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) wavelengths. These measurements served as proxies for canopy structure, short term changes in radiation use efficiency (RUE) and longer term changes in pools of photosynthetically important pigments. We found that aggregated measurements of PRI were related to total canopy RUE at both diurnal and seasonal time scales with the highest correlations occurring during periods when light-related stress was greatest. Diurnal and seasonal variability among spatially distributed measurements was in part explained by species composition and canopy structure. At the seasonal time scale we found evidence that suggested the ratios of photosynthetic pigments were related to canopy development and were important for explaining variability in the relationship between APAR and GPP across the growing season.

  5. Influence of canopy foliage on turbulence above tall deciduous vegetation

    NASA Astrophysics Data System (ADS)

    Shapkalijevski, Metodija; Moene, Arnold; Ouwersloot, Huug; Patton, Edward; Vilà-Guerau de Arellano, Jordi

    2015-04-01

    In this study, the role of tree phenology on the atmospheric turbulence over tall vegetation is investigated. Our aim is to study dimensionless mean gradients, variances, and the turbulent kinetic energy (TKE) within the roughness sublayer (RSL), and their dependence on the leaf state of the canopy and the stability regimes. To do this, we analyse observations, that are continuously collected over a whole season above and in a walnut tree orchard during the Canopy Horizontal Array Turbulence Study (CHATS) field experiment near Dixon, California. To support this data analysis, we compare profiles of vertical fluxes and co-variances, as well as vertical gradients of mean wind, temperature and humidity, with empirically derived dimensionless gradients from previous studies and results from a second-order closure turbulence diagnostic model. In doing so, we study the differences in the calculation of the dimensionless gradients between recently developed model approaches that account for the RSL effects on these gradients against representations that omit those effects. The observations and model results are non-dimensionalized using atmospheric surface layer scaling, paying special attention to the displacement height. The latter is calculated from the observations and depends on the variable under consideration and the leaf state. Our results for the dimensionless gradients of momentum, heat and moisture show a reduction of these variables closer to the canopy top compared to the standard Monin-Obukhov similarity theory (MOST) for both unstable and near neutral conditions. We find that the reduction is larger for canopy with leaves than for leafless canopy. This confirms the applicability of the aforementioned RSL models. Their results are in better agreement with the observations for the fully vegetated canopy then for the leafless canopy. With regard to the TKE-budget, our analysis shows that turbulent transport is increasingly important term of the budget when

  6. Remote canopy hemispherical image collection system

    NASA Astrophysics Data System (ADS)

    Wan, Xuefen; Liu, Bingyu; Yang, Yi; Han, Fang; Cui, Jian

    2016-11-01

    Canopies are major part of plant photosynthesis and have distinct architectural elements such as tree crowns, whorls, branches, shoots, etc. By measuring canopy structural parameters, the solar radiation interception, photosynthesis effects and the spatio-temporal distribution of solar radiation under the canopy can be evaluated. Among canopy structure parameters, Leaf Area Index (LAI) is the key one. Leaf area index is a crucial variable in agronomic and environmental studies, because of its importance for estimating the amount of radiation intercepted by the canopy and the crop water requirements. The LAI can be achieved by hemispheric images which are obtained below the canopy with high accuracy and effectiveness. But existing hemispheric images canopy-LAI measurement technique is based on digital SLR camera with a fisheye lens. Users need to collect hemispheric image manually. The SLR camera with fisheye lens is not suit for long-term canopy-LAI outdoor measurement too. And the high cost of SLR limits its capacity. In recent years, with the development of embedded system and image processing technology, low cost remote canopy hemispheric image acquisition technology is becoming possible. In this paper, we present a remote hemispheric canopy image acquisition system with in-field/host configuration. In-field node based on imbed platform, low cost image sensor and fisheye lens is designed to achieve hemispherical image of plant canopy at distance with low cost. Solar radiation and temperature/humidity data, which are important for evaluating image data validation, are obtained for invalid hemispherical image elimination and node maintenance too. Host computer interacts with in-field node by 3G network. The hemispherical image calibration and super resolution are used to improve image quality in host computer. Results show that the remote canopy image collection system can make low cost remote canopy image acquisition for LAI effectively. It will be a potential

  7. 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

  8. Changes of ndvi across vertical canopy layers in temperate deciduous forest during a litterfall period

    NASA Astrophysics Data System (ADS)

    Kim, J. M.; Ryu, Y.

    2015-12-01

    Normalized Difference Vegetation Index (NDVI) is a key variable indicating changes in vegetation dynamics and carbon flux. Previous studies have paid little attention to the changes in NDVI during litterfall period. In this study, we report the changes of NDVI across vertical canopy layers in a temperate deciduous forest during a litterfall period. To monitor changes in canopy structure, functions, and spectral properties during the litterfall period, we combined automatic observations of NDVI derived from LED-spectral sensors and LAI derived from digital cover photography installed at multiple canopy layer depths. Furthermore, we collected hyperspectral optical properties of leaves across multiple canopy layers and hyperspectral reflectance of forest background using ASD-FieldSpec. We found that NDVI in forest floor became greater than the NDVI measured from the top of canopy during the litterfall period. We discuss what satellite-derived NDVI exactly sees during the litterfall period, which will be useful to better understand forest autumn phenology at large scales.

  9. Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

    USGS Publications Warehouse

    Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

    2013-01-01

    The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

  10. Winners and losers in the competition for space in tropical forest canopies.

    PubMed

    Kellner, James R; Asner, Gregory P

    2014-05-01

    Trees compete for space in the canopy, but where and how individuals or their component parts win or lose is poorly understood. We developed a stochastic model of three-dimensional dynamics in canopies using a hierarchical Bayesian framework, and analysed 267,533 positive height changes from 1.25 m pixels using data from airborne LiDAR within 43 ha on the windward flank of Mauna Kea. Model selection indicates a strong resident's advantage, with 97.9% of positions in the canopy retained by their occupants over 2 years. The remaining 2.1% were lost to a neighbouring contender. Absolute height was a poor predictor of success, but short stature greatly raised the risk of being overtopped. Growth in the canopy was exponentially distributed with a scaling parameter of 0.518. These findings show how size and spatial proximity influence the outcome of competition for space, and provide a general framework for the analysis of canopy dynamics.

  11. Does canopy nitrogen uptake enhance carbon sequestration by trees?

    PubMed

    Nair, Richard K F; Perks, Micheal P; Weatherall, Andrew; Baggs, Elizabeth M; Mencuccini, Maurizio

    2016-02-01

    Temperate forest (15) N isotope trace experiments find nitrogen (N) addition-driven carbon (C) uptake is modest as little additional N is acquired by trees; however, several correlations of ambient N deposition against forest productivity imply a greater effect of atmospheric nitrogen deposition than these studies. We asked whether N deposition experiments adequately represent all processes found in ambient conditions. In particular, experiments typically apply (15) N to directly to forest floors, assuming uptake of nitrogen intercepted by canopies (CNU) is minimal. Additionally, conventional (15) N additions typically trace mineral (15) N additions rather than litter N recycling and may increase total N inputs above ambient levels. To test the importance of CNU and recycled N to tree nutrition, we conducted a mesocosm experiment, applying 54 g N/(15) N ha(-1)  yr(-1) to Sitka spruce saplings. We compared tree and soil (15) N recovery among treatments where enrichment was due to either (1) a (15) N-enriched litter layer, or mineral (15) N additions to (2) the soil or (3) the canopy. We found that 60% of (15) N applied to the canopy was recovered above ground (in needles, stem and branches) while only 21% of (15) N applied to the soil was found in these pools. (15) N recovery from litter was low and highly variable. (15) N partitioning among biomass pools and age classes also differed among treatments, with twice as much (15) N found in woody biomass when deposited on the canopy than soil. Stoichiometrically calculated N effect on C uptake from (15) N applied to the soil, scaled to real-world conditions, was 43 kg C kg N(-1) , similar to manipulation studies. The effect from the canopy treatment was 114 kg C kg N(-1) . Canopy treatments may be critical to accurately represent N deposition in the field and may address the discrepancy between manipulative and correlative studies.

  12. Measurement of tree canopy architecture

    NASA Technical Reports Server (NTRS)

    Martens, S. N.; Ustin, S. L.; Norman, J. M.

    1991-01-01

    The lack of accurate extensive geometric data on tree canopies has retarded development and validation of radiative transfer models. A stratified sampling method was devised to measure the three-dimensional geometry of 16 walnut trees which had received irrigation treatments of either 100 or 33 per cent of evapotranspirational (ET) demand for the previous two years. Graphic reconstructions of the three-dimensional geometry were verified by 58 independent measurements. The distributions of stem- and leaf-size classes, lengths, and angle classes were determined and used to calculate leaf area index (LAI), stem area, and biomass. Reduced irrigation trees have lower biomass of stems, leaves and fruit, lower LAI, steeper leaf angles and altered biomass allocation to large stems. These data can be used in ecological models that link canopy processes with remotely sensed measurements.

  13. Modeling photosynthesis of discontinuous plant canopies by linking Geometric Optical Radiative Transfer model with biochemical processes

    NASA Astrophysics Data System (ADS)

    Xin, Q.; Gong, P.; Li, W.

    2015-02-01

    Modeling vegetation photosynthesis is essential for understanding carbon exchanges between terrestrial ecosystems and the atmosphere. The radiative transfer process within plant canopies is one of the key drivers that regulate canopy photosynthesis. Most vegetation cover consists of discrete plant crowns, of which the physical observation departs from the underlying assumption of a homogenous and uniform medium in classic radiative transfer theory. Here we advance the Geometric Optical Radiative Transfer (GORT) model to simulate photosynthesis activities for discontinuous plant canopies. We separate radiation absorption into two components that are absorbed by sunlit and shaded leaves, and derive analytical solutions by integrating over the canopy layer. To model leaf-level and canopy-level photosynthesis, leaf light absorption is then linked to the biochemical process of gas diffusion through leaf stomata. The canopy gap probability derived from GORT differs from classic radiative transfer theory, especially when the leaf area index is high, due to leaf clumping effects. Tree characteristics such as tree density, crown shape, and canopy length affect leaf clumping and regulate radiation interception. Modeled gross primary production (GPP) for two deciduous forest stands could explain more than 80% of the variance of flux tower measurements at both near hourly and daily time scales. We also demonstrate that the ambient CO2 concentration influences daytime vegetation photosynthesis, which needs to be considered in state-of-the-art biogeochemical models. The proposed model is complementary to classic radiative transfer theory and shows promise in modeling the radiative transfer process and photosynthetic activities over discontinuous forest canopies.

  14. Ground-Based Robotic Sensing of an Agricultural Sub-Canopy Environment

    NASA Astrophysics Data System (ADS)

    Burns, A.; Peschel, J.

    2015-12-01

    Airborne remote sensing is a useful method for measuring agricultural crop parameters over large areas; however, the approach becomes limited to above-canopy characterization as a crop matures due to reduced visual access of the sub-canopy environment. During the growth cycle of an agricultural crop, such as soybeans, the micrometeorology of the sub-canopy environment can significantly impact pod development and reduced yields may result. Larger-scale environmental conditions aside, the physical structure and configuration of the sub-canopy matrix will logically influence local climate conditions for a single plant; understanding the state and development of the sub-canopy could inform crop models and improve best practices but there are currently no low-cost methods to quantify the sub-canopy environment at a high spatial and temporal resolution over an entire growth cycle. This work describes the modification of a small tactical and semi-autonomous, ground-based robotic platform with sensors capable of mapping the physical structure of an agricultural row crop sub-canopy; a soybean crop is used as a case study. Point cloud data representing the sub-canopy structure are stored in LAS format and can be used for modeling and visualization in standard GIS software packages.

  15. Multispectral vegetative canopy parameter retrieval

    NASA Astrophysics Data System (ADS)

    Borel, Christoph C.; Bunker, David J.

    2011-11-01

    Precision agriculture, forestry and environmental remote sensing are applications uniquely suited to the 8 bands that DigitalGlobe's WorldView-2 provides. At the fine spatial resolution of 0.5 m (panchromatic) and 2 m (multispectral) individual trees can be readily resolved. Recent research [1] has shown that it is possible for hyper-spectral data to invert plant reflectance spectra and estimate nitrogen content, leaf water content, leaf structure, canopy leaf area index and, for sparse canopies, also soil reflectance. The retrieval is based on inverting the SAIL (Scattering by Arbitrary Inclined Leaves) vegetation radiative transfer model for the canopy structure and the reflectance model PROSPECT4/5 for the leaf reflectance. Working on the paper [1] confirmed that a limited number of adjacent bands covering just the visible and near infrared can retrieve the parameters as well, opening up the possibility that this method can be used to analyze multi-spectral WV-2 data. Thus it seems possible to create WV-2 specific inversions using 8 bands and apply them to imagery of various vegetation covered surfaces of agricultural and environmental interest. The capability of retrieving leaf water content and nitrogen content has important applications in determining the health of vegetation, e.g. plant growth status, disease mapping, quantitative drought assessment, nitrogen deficiency, plant vigor, yield, etc.

  16. 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.

  17. 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

  18. 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

    2017-01-18

    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

  19. The 4-Dimensional Plant: Effects of Wind-Induced Canopy Movement on Light Fluctuations and Photosynthesis

    PubMed Central

    Burgess, Alexandra J.; Retkute, Renata; Preston, Simon P.; Jensen, Oliver E.; Pound, Michael P.; Pridmore, Tony P.; Murchie, Erik H.

    2016-01-01

    Physical perturbation of a plant canopy brought about by wind is a ubiquitous phenomenon and yet its biological importance has often been overlooked. This is partly due to the complexity of the issue at hand: wind-induced movement (or mechanical excitation) is a stochastic process which is difficult to measure and quantify; plant motion is dependent upon canopy architectural features which, until recently, were difficult to accurately represent and model in 3-dimensions; light patterning throughout a canopy is difficult to compute at high-resolutions, especially when confounded by other environmental variables. Recent studies have reinforced the expectation that canopy architecture is a strong determinant of productivity and yield; however, links between the architectural properties of the plant and its mechanical properties, particularly its response to wind, are relatively unknown. As a result, biologically relevant data relating canopy architecture, light- dynamics, and short-scale photosynthetic responses in the canopy setting are scarce. Here, we hypothesize that wind-induced movement will have large consequences for the photosynthetic productivity of our crops due to its influence on light patterning. To address this issue, in this study we combined high resolution 3D reconstructions of a plant canopy with a simple representation of canopy perturbation as a result of wind using solid body rotation in order to explore the potential effects on light patterning, interception, and photosynthetic productivity. We looked at two different scenarios: firstly a constant distortion where a rice canopy was subject to a permanent distortion throughout the whole day; and secondly, a dynamic distortion, where the canopy was distorted in incremental steps between two extremes at set time points in the day. We find that mechanical canopy excitation substantially alters light dynamics; light distribution and modeled canopy carbon gain. We then discuss methods required for

  20. The 4-Dimensional Plant: Effects of Wind-Induced Canopy Movement on Light Fluctuations and Photosynthesis.

    PubMed

    Burgess, Alexandra J; Retkute, Renata; Preston, Simon P; Jensen, Oliver E; Pound, Michael P; Pridmore, Tony P; Murchie, Erik H

    2016-01-01

    Physical perturbation of a plant canopy brought about by wind is a ubiquitous phenomenon and yet its biological importance has often been overlooked. This is partly due to the complexity of the issue at hand: wind-induced movement (or mechanical excitation) is a stochastic process which is difficult to measure and quantify; plant motion is dependent upon canopy architectural features which, until recently, were difficult to accurately represent and model in 3-dimensions; light patterning throughout a canopy is difficult to compute at high-resolutions, especially when confounded by other environmental variables. Recent studies have reinforced the expectation that canopy architecture is a strong determinant of productivity and yield; however, links between the architectural properties of the plant and its mechanical properties, particularly its response to wind, are relatively unknown. As a result, biologically relevant data relating canopy architecture, light- dynamics, and short-scale photosynthetic responses in the canopy setting are scarce. Here, we hypothesize that wind-induced movement will have large consequences for the photosynthetic productivity of our crops due to its influence on light patterning. To address this issue, in this study we combined high resolution 3D reconstructions of a plant canopy with a simple representation of canopy perturbation as a result of wind using solid body rotation in order to explore the potential effects on light patterning, interception, and photosynthetic productivity. We looked at two different scenarios: firstly a constant distortion where a rice canopy was subject to a permanent distortion throughout the whole day; and secondly, a dynamic distortion, where the canopy was distorted in incremental steps between two extremes at set time points in the day. We find that mechanical canopy excitation substantially alters light dynamics; light distribution and modeled canopy carbon gain. We then discuss methods required for

  1. Influence of seasonal canopy development on turbulent flow characteristics in a hedgerow vineyard

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Turbulence is the main driver of vegetation-atmosphere exchanges. Flow characteristics determine the transport of energy and matter between different layers of the canopy and the atmosphere, defining local microclimatic conditions and influencing physiological processes of the vegetation. Therefore, studying turbulent flow dynamics inside and above the canopy is crucial to correctly predict overall fluxes of matter and energy and to understand their nature. Numerous studies have already investigated the characteristics of canopy turbulence over a wide range of vegetation types, leading to a thorough description of canopy turbulence. However, only a few studies have investigated the influence of gradual canopy structural changes such as foliage density (on multi-day time scales) on turbulence field properties. We hypothesize that seasonal variations of foliage density play a crucial role modifying foliage drag and canopy roughness, determining the degree of coupling between vegetation and the atmosphere, and changing the profiles of turbulent moments. The aim of this study was to follow the continuous evolution of turbulent flow characteristics from leaf budbreak to fully developed foliage in a hedgerow vineyard in the North East of Italy. Synchronous measurements from a vertical profile of five sonic anemometers on a 5 m tower have been collected at 20 Hz from beginning of April to end of July 2015.Detailed measurements of Leaf Area Density (LAD) profile and canopy architecture were performed at regular intervals (ca. weekly) around the tower. The canopy bulk drag coefficient increased during the growing season, suggesting that the coupling between the vegetation and the atmosphere increased with LAD. Vertical profiles of turbulent statistics showed to be highly correlated to local values of LAD. The penetration of momentum flux in the canopy decreased with the gradual increase of foliage. Most of the drag was exerted by the part of the canopy with denser foliage

  2. Evaluation of the Advanced-Canopy-Atmosphere-Surface Algorithm (ACASA Model) Using Eddy Covariance Technique Over Sparse Canopy

    NASA Astrophysics Data System (ADS)

    Marras, S.; Spano, D.; Sirca, C.; Duce, P.; Snyder, R.; Pyles, R. D.; Paw U, K. T.

    2008-12-01

    Land surface models are usually used to quantify energy and mass fluxes between terrestrial ecosystems and atmosphere on micro- and regional scales. One of the most elaborate land surface models for flux modelling is the Advanced Canopy-Atmosphere-Soil Algorithm (ACASA) model, which provides micro-scale as well as regional-scale fluxes when imbedded in a meso-scale meteorological model (e.g., MM5 or WRF). The model predicts vegetation conditions and changes with time due to plant responses to environment variables. In particular, fluxes and profiles of heat, water vapor, carbon and momentum within and above canopy are estimated using third-order equations. It also estimates turbulent profiles of velocity, temperature, humidity within and above canopy, and CO2 fluxes are estimated using a combination of Ball-Berry and Farquhar equations. The ACASA model is also able to include the effects of water stress on stomata, transpiration and CO2 assimilation. ACASA model is unique because it separates canopy domain into twenty atmospheric layers (ten layers within the canopy and ten layers above the canopy), and the soil is partitioned into fifteen layers of variable thickness. The model was mainly used over dense canopies in the past, so the aim of this work was to test the ACASA model over a sparse canopy as Mediterranean maquis. Vegetation is composed by sclerophyllous species of shrubs that are always green, with leathery leaves, small height, with a moderately sparse canopy, and that are tolerant at water stress condition. Eddy Covariance (EC) technique was used to collect continuous data for more than 3 years period. Field measurements were taken in a natural maquis site located near Alghero, Sardinia, Italy and they were used to parameterize and validate the model. The input values were selected by running the model several times varying the one parameter per time. A second step in the parameterization process was the simultaneously variation of some parameters

  3. Waveform- and Terrestrial Lidar Assessment of the Usual (Structural) Suspects in a Forest Canopy

    NASA Astrophysics Data System (ADS)

    van Aardt, J. A.; Romanczyk, P.; Kelbe, D.; van Leeuwen, M.; Cawse-Nicholson, K.; Gough, C. M.; Kampe, T. U.

    2015-12-01

    Forest inventory has evolved from standard stem diameter-height relationships, to coarse canopy metrics, to more involved ecologically-meaningful variables, such as leaf area index (LAI) and even canopy radiative transfer as a function of canopy gaps, leaf clumping, and leaf angle distributions. Accurate and precise measurement of the latter set of variables presents a challenge to the ecological and modeling communities; however, relatively novel remote sensing modalities, e.g., waveform lidar (wlidar) and terrestrial lidar systems (TLS), have the potential to adress this challenge. Research teams at Rochester Institute of Technology (RIT) and the Virginia Commonwealth University (VCU) have been collaborating with the National Ecological Observation Network (NEON) to assess vegetation canopy structure and variation at the University of Michigan Biological Research Station and the NEON Northeast domain (Harvard Forest, MA). Airborne small-footprint wlidar data, in-situ TLS data, and first-principles, physics-based simulation tools are being used to study (i) the impact of vegetation canopy geometric elements on wlidar signals (twigs and petioles have been deemed negligible), (ii) the analysis of airborne wlidar data for top-down assessment of canopy metrics such as LAI, and (iii) our ability to extract "bottom-up" canopy structure from TLS using scans registered to each other using a novel marker-free registration approach (e.g., basal area: R2=0.82, RMSE=7.43 m2/ha). Such studies indicate that we can potentially assess radiative transfer through vegetation canopies remotely using a vertically-stratified approach with wlidar, and augment such an approach via rapid-scan TLS technology to gain a better understanding of fine-scale variation in canopy structure. This in turn is key to quantifying and modeling radiative transfer based on understanding of forest canopy structural change as a function of ecosystem development, climate, and anthropogenic drivers.

  4. Post senescent grass canopy remote sensing

    NASA Technical Reports Server (NTRS)

    Tucker, C. J.

    1978-01-01

    Analysis of in situ collected spectral reflectance data from a dormant or senescent grass canopy showed a direct relationship existed between spectral reflectance and biomass for the 0.50-0.80 micron spectral region. The data, collected four weeks after the end of the growing season, indicated that post senescent remote sensing of grass canopy biomass is possible and helps to elucidate the spectral contribution of recently dead vegetation in mixed live/dead canopy situations.

  5. An empirical model that uses light attenuation and plant nitrogen status to predict within-canopy nitrogen distribution and upscale photosynthesis from leaf to whole canopy

    PubMed Central

    Louarn, Gaëtan; Frak, Ela; Zaka, Serge; Prieto, Jorge; Lebon, Eric

    2015-01-01

    Modelling the spatial and temporal distribution of leaf nitrogen (N) is central to specify photosynthetic parameters and simulate canopy photosynthesis. Leaf photosynthetic parameters depend on both local light availability and whole-plant N status. The interaction between these two levels of integration has generally been modelled by assuming optimal canopy functioning, which is not supported by experiments. During this study, we examined how a set of empirical relationships with measurable parameters could be used instead to predict photosynthesis at the leaf and whole-canopy levels. The distribution of leaf N per unit area (Na) within the canopy was related to leaf light irradiance and to the nitrogen nutrition index (NNI), a whole-plant variable accounting for plant N status. Na was then used to determine the photosynthetic parameters of a leaf gas exchange model. The model was assessed on alfalfa canopies under contrasting N nutrition and with N2-fixing and non-fixing plants. Three experiments were carried out to parameterize the relationships between Na, leaf irradiance, NNI and photosynthetic parameters. An additional independent data set was used for model evaluation. The N distribution model showed that it was able to predict leaf N on the set of leaves tested. The Na at the top of the canopy appeared to be related linearly to the NNI, whereas the coefficient accounting for N allocation remained constant. Photosynthetic parameters were related linearly to Na irrespective of N nutrition and the N acquisition mode. Daily patterns of gas exchange were simulated accurately at the leaf scale. When integrated at the whole-canopy scale, the model predicted that raising N availability above an NNI of 1 did not result in increased net photosynthesis. Overall, the model proposed offered a solution for a dynamic coupling of leaf photosynthesis and canopy N distribution without requiring any optimal functioning hypothesis. PMID:26433705

  6. An empirical model that uses light attenuation and plant nitrogen status to predict within-canopy nitrogen distribution and upscale photosynthesis from leaf to whole canopy.

    PubMed

    Louarn, Gaëtan; Frak, Ela; Zaka, Serge; Prieto, Jorge; Lebon, Eric

    2015-10-03

    Modelling the spatial and temporal distribution of leaf nitrogen (N) is central to specify photosynthetic parameters and simulate canopy photosynthesis. Leaf photosynthetic parameters depend on both local light availability and whole-plant N status. The interaction between these two levels of integration has generally been modelled by assuming optimal canopy functioning, which is not supported by experiments. During this study, we examined how a set of empirical relationships with measurable parameters could be used instead to predict photosynthesis at the leaf and whole-canopy levels. The distribution of leaf N per unit area (Na) within the canopy was related to leaf light irradiance and to the nitrogen nutrition index (NNI), a whole-plant variable accounting for plant N status. Na was then used to determine the photosynthetic parameters of a leaf gas exchange model. The model was assessed on alfalfa canopies under contrasting N nutrition and with N2-fixing and non-fixing plants. Three experiments were carried out to parameterize the relationships between Na, leaf irradiance, NNI and photosynthetic parameters. An additional independent data set was used for model evaluation. The N distribution model showed that it was able to predict leaf N on the set of leaves tested. The Na at the top of the canopy appeared to be related linearly to the NNI, whereas the coefficient accounting for N allocation remained constant. Photosynthetic parameters were related linearly to Na irrespective of N nutrition and the N acquisition mode. Daily patterns of gas exchange were simulated accurately at the leaf scale. When integrated at the whole-canopy scale, the model predicted that raising N availability above an NNI of 1 did not result in increased net photosynthesis. Overall, the model proposed offered a solution for a dynamic coupling of leaf photosynthesis and canopy N distribution without requiring any optimal functioning hypothesis.

  7. Tree canopy radiance measurement system

    NASA Technical Reports Server (NTRS)

    Caldwell, William; Vanderbilt, V. C.

    1989-01-01

    A system is described for obtaining both an estimate of the spatial mean bidirectional reflectance factor (BRF) for a tree canopy (displaying a horizontally heterogeneous foliage distribution) and the statistical significance of that estimate. The system includes a manlift supporting a horizontal beam 7 m long on which are mounted four radiometers. These radiometers may be pointed, and radiance data acquired, in any of 11 view directions in the principal plane of the sun. A total of 80 data points, acquired in 3 min, were used to estimate the BRF of a walnut orchard 5 m tall and detect true differences of 12 percent of the mean approximately 90 percent of the time.

  8. Tree canopy radiance measurement system

    NASA Astrophysics Data System (ADS)

    Caldwell, William; Vanderbilt, V. C.

    1989-11-01

    A system is described for obtaining both an estimate of the spatial mean bidirectional reflectance factor (BRF) for a tree canopy (displaying a horizontally heterogeneous foliage distribution) and the statistical significance of that estimate. The system includes a manlift supporting a horizontal beam 7 m long on which are mounted four radiometers. These radiometers may be pointed, and radiance data acquired, in any of 11 view directions in the principal plane of the sun. A total of 80 data points, acquired in 3 min, were used to estimate the BRF of a walnut orchard 5 m tall and detect true differences of 12 percent of the mean approximately 90 percent of the time.

  9. Turbulence in vertical axis wind turbine canopies

    NASA Astrophysics Data System (ADS)

    Kinzel, Matthias; Araya, Daniel B.; Dabiri, John O.

    2015-11-01

    Experimental results from three different full scale arrays of vertical-axis wind turbines (VAWTs) under natural wind conditions are presented. The wind velocities throughout the turbine arrays are measured using a portable meteorological tower with seven, vertically staggered, three-component ultrasonic anemometers. The power output of each turbine is recorded simultaneously. The comparison between the horizontal and vertical energy transport for the different turbine array sizes shows the importance of vertical transport for large array configurations. Quadrant-hole analysis is employed to gain a better understanding of the vertical energy transport at the top of the VAWT arrays. The results show a striking similarity between the flows in the VAWT arrays and the adjustment region of canopies. Namely, an increase in ejections and sweeps and decrease in inward and outward interactions occur inside the turbine array. Ejections are the strongest contributor, which is in agreement with the literature on evolving and sparse canopy flows. The influence of the turbine array size on the power output of the downstream turbines is examined by comparing a streamwise row of four single turbines with square arrays of nine turbine pairs. The results suggest that a new boundary layer forms on top of the larger turbine arrays as the flow adjusts to the new roughness length. This increases the turbulent energy transport over the whole planform area of the turbine array. By contrast, for the four single turbines, the vertical energy transport due to turbulent fluctuations is only increased in the near wake of the turbines. These findings add to the knowledge of energy transport in turbine arrays and therefore the optimization of the turbine spacing in wind farms.

  10. Canopy Effects on Macroscale Snow Sublimation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2015-12-01

    Sublimation of snow cover directly affects snow accumulation, impacting ecosystem processes, soil moisture, soil porosity, biogeochemical processes, wildfire, and water resources. Available energy, the exposed surface area of a snow cover, and exposure time with the atmosphere vary greatly in complex terrain (e.g., aspect, elevation, forest cover), with latitude, and with continentality. It is therefore difficult to scale up results from site specific short term studies. Using the 32-km NARR, the 4-km PRISM, with 30-m terrain and forest cover data, meteorological variables are downscaled to simulate sublimation from canopy intercepted snow and from the snowpack over the Salt River Basin in Arizona for a wet and dry year. Simulations indicate that: (1) total sublimation is highly variable in response to variability in both sublimation rate and snow cover duration; (2) total canopy sublimation is similar for both years while ground sublimation is considerably greater during the wet year; (3) sublimation is a relatively greater contribution to the snow water budget during the dry year (28% vs. 20% of total snowfall); (4) at high elevations, ground sublimation is less in open areas than forested areas during the dry year, while the reverse is evident during the wet year as snowpack lasted longer into spring. While a reduction in leaf area index leads to a reduction of total sublimation due to less interception in both years, ground sublimation increases during the dry year, possibly due to less sheltering from solar radiation and wind. This reduction in sheltering results in a large decrease in snowpack duration (i.e., ten days in spring) at mid-elevations for the wet year, leading to a decrease in ground sublimation. This results in a 500 meter difference in the elevation of maximum sublimation reduction upon reduced leaf area index between the two years. Forest cover properties can vary considerably on short and long time scales through natural (wildfire, bark beetle

  11. VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine.

    PubMed

    De Bei, Roberta; Fuentes, Sigfredo; Gilliham, Matthew; Tyerman, Steve; Edwards, Everard; Bianchini, Nicolò; Smith, Jason; Collins, Cassandra

    2016-04-23

    Leaf area index (LAI) and plant area index (PAI) are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI), canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants.

  12. Spatiotemporal variation of crown-scale stomatal conductance in an arid Vitis vinifera L. cv. Merlot vineyard: direct effects of hydraulic properties and indirect effects of canopy leaf area.

    PubMed

    Zhang, Yanqun; Oren, Ram; Kang, Shaozhong

    2012-03-01

    Vineyards were planted in the arid region of northwest China to meet the local economic strategy while reducing agricultural water use. Sap flow, environmental variables, a plant characteristic (sapwood-to-leaf area ratio, A(s)/A(l)) and a canopy characteristic (leaf area index, L) were measured in a vineyard in the region during the growing season of 2009, and hourly canopy stomatal conductance (G(si)) was estimated for individual vines to quantify the relationships between G(si) and these variables. After accounting for the effects of vapor pressure deficit (D) and solar radiation (R(s)) on G(si), much of the remaining variation of reference G(si) (G(siR)) was driven by that of leaf-specific hydraulic conductivity, which in turn was driven by that of A(s)/A(l). After accounting for that effect on G(siR), appreciable temporal variation remained in the decline rate of G(siR) with decreasing vineyard-averaged relative extractable soil water (θ(E)). This variation was related to the differential decline ofθ(E) near each monitored vine, decreasing faster between irrigation events near vines where L was greater, thus adding to the spatiotemporal variation of G(siR) observed in the vineyard. We also found that the vines showed isohydric-like behavior whenθ(E) was low, but switched to anisohydric-like behavior with increasingθ(E). Modeledθ(E) and associated G(s) of a canopy with even L (1.9 m(2) m(-2)) were greater than that of the same average L but split between the lowest and highest L observed along sections of rows in the vineyard (1.2 and 2.6 m(2) m(-2)) by 6 and 12%, respectively. Our results suggest that managing sectional L near the average, rather than allowing a wide variation, can reduce soil water depletion, maintaining G(s) higher, thus potentially enhancing yield.

  13. Processes of Ammonia Air-Surface Exchange in a Fertilized Corn Canopy

    NASA Astrophysics Data System (ADS)

    Walker, J. T.; Bash, J. O.; Jones, M.; Nemitz, E.; Robarge, W. P.

    2009-12-01

    Processes of ammonia (NH3) air-surface exchange in fertilized crops include bi-directional flux (emission or deposition) from the soil, surface litter, leaf stomatal cavity, and leaf cuticle. These component fluxes establish the net exchange between the canopy and atmosphere. We conducted an experiment in the summer of 2007 in eastern North Carolina to quantify the net flux of NH3 from a fertilized corn canopy over the course of the growing season. A primary objective was to examine the relative importance of soil vs. foliage exchange pathways with respect to net canopy-scale fluxes. Continuous wet rotating denuder and photoacoustic spectroscopic NH3 measurement methods were configured in a gradient mode to measure canopy-scale fluxes using the modified Bowen-ratio technique. In-canopy source-sink relationships were examined by inverse modeling of NH3 concentration, temperature, and turbulence profiles. Additionally, measurements of NH4+ and H+ in the soil solution, leaf apoplast, and leaf surface water were used in combination with resistance modeling to examine the relationships between net canopy-scale fluxes and soil, stomatal, and cuticular exchange pathways. Measurement and modeling results are presented and the relevance of this work to national NH3 emission inventories and regional air quality modeling is discussed.

  14. Chlorophyll fluorescence tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest.

    PubMed

    Yang, Hualei; Yang, Xi; Zhang, Yongguang; Heskel, Mary A; Lu, Xiaoliang; Munger, J William; Sun, Shucun; Tang, Jianwu

    2016-12-14

    Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf-level ChlF was linked with canopy-scale solar-induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts, USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R(2 ) = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively; P < 0.0001). We developed a model to estimate GPP from the tower-based measurement of SIF and leaf-level ChlF parameters. The estimation of GPP from this model agreed well with flux tower observations of GPP (R(2 ) = 0.68; P < 0.0001), demonstrating the potential of SIF for modeling GPP. At the leaf scale, we found that leaf Fq '/Fm ', the fraction of absorbed photons that are used for photochemistry for a light-adapted measurement from a pulse amplitude modulation fluorometer, was the best leaf fluorescence parameter to correlate with canopy SIF yield (SIF/APAR, R(2 ) = 0.79; P < 0.0001). We also found that canopy SIF and SIF-derived GPP (GPPSIF ) were strongly correlated to leaf-level biochemistry and canopy structure, including chlorophyll content (R(2 ) = 0.65 for canopy GPPSIF and chlorophyll content; P < 0.0001), leaf area index (LAI) (R(2 ) = 0.35 for canopy GPPSIF and LAI; P < 0.0001), and normalized difference vegetation index (NDVI) (R(2 ) = 0.36 for

  15. Plant canopy characteristics effect on spray deposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    While it is common for applicators to standardize their application parameters to minimize changes in settings during a season, this practice does not necessarily provide the best delivery when targeting different types of plant canopies and different zones within the canopy. The objective of this w...

  16. Canopy Structure in Relation to Rainfall Interception

    NASA Astrophysics Data System (ADS)

    Fathizadeh, Omid; Mohsen Hosseini, Seyed; Keim, Richard

    2016-04-01

    Spatial variation of throughfall (TF) is linked to canopy structure. The effects of canopy structure on the spatial redistribution of rainfall in deciduous stands remains poorly documented. Therefore, the objective of this study is to evaluate the influence of canopy structure such as stand density on the partitioning of incident rainfall when passing through the canopy of Brant's oak (Quercus branti) forest stands. The study site is the Zagros forests in the western Iranian state of Ilam, protected forests of Dalab region. Twelve TF plots (50 m × 50 m) with 30 gauges randomly placed within each plot were established. Interception loss was computed as the difference between rain and TF. Canopy cover (%) and leaf area index (LAI, m2 m-2) were estimated from the analysis of hemispherical photographs obtained during the fully leafed period. Relative interception varied from ˜4% at 0.1 LAI and canopy cover of 10% to ˜25% at 1.5 LAI and canopy cover of 65%. Interception represents a significant component of the seasonal water balance of oak forests, particularly in the case of intensive plantings. Keywords: Canopy Structure, Rainfall redistribution, Zagros forests, Quercus branti

  17. Canopy spectral and chemical diversity from lowland to tree line in the Western Amazon using CAO-VSWIR

    NASA Astrophysics Data System (ADS)

    Martin, R. E.; Asner, G. P.

    2012-12-01

    Canopy chemistry and spectroscopy offer insight into community assembly and ecosystem processes in high-diversity tropical forests. Results from one lowland site in the Peruvian Amazon suggests both an environmental and an evolutionary component of canopy trait development however, the degree to which larger environmental differences influence diversity in canopy traits and their respective spectroscopic signatures across remains poorly understood. The spectranomics approach explicitly connects phylogenetic, chemical and spectral patterns in tropical canopies providing the basis for analysis, while high-fidelity, airborne remote sensing measurements extend plot-level data to landscape-scale, achieving a comprehensive view of the region. In 2011, the Carnegie Airborne Observatory (CAO) was used to sample a large region of the Western Amazon Basin in southeastern Peru, extending from lowlands to tree line in the Andean mountains. The CAO Visible-Shortwave Imaging Spectrometer (VSWIR) collected 480-band high-fidelity imaging spectroscopy data of the forest canopy, while its high-resolution LiDAR captured information on canopy structure and the underlying terrain. The data were used to quantify relationships between environmental gradients and canopy chemical and spectral diversity. Results suggest strong environmental control with additional phylogenetic influence over canopy spectral and chemical properties, particularly those related to structure, defense and metabolic function. Data from CAO-VSWIR extends the large range in canopy chemical and spectral diversity related to environmental factors across the Western Amazon Basin.

  18. Changes in leaf area, nitrogen content and canopy photosynthesis in soybean exposed to an ozone concentration gradient.

    PubMed

    Oikawa, Shimpei; Ainsworth, Elizabeth A

    2016-08-01

    Influences of ozone (O3) on light-saturated rates of photosynthesis in crop leaves have been well documented. To increase our understanding of O3 effects on individual- or stand level productivity, a mechanistic understanding of factors determining canopy photosynthesis is necessary. We used a canopy model to scale photosynthesis from leaf to canopy, and analyzed the importance of canopy structural and leaf ecophysiological characteristics in determining canopy photosynthesis in soybean stands exposed to 9 concentrations of [O3] (37-116 ppb; 9-h mean). Light intensity and N content peaked in upper canopy layers, and sharply decreased through the lower canopy. Plant leaf area decreased with increasing [O3] allowing for greater light intensity to reach lower canopy levels. At the leaf level, light-saturated photosynthesis decreased and dark respiration increased with increasing [O3]. These data were used to calculate daily net canopy photosynthesis (Pc). Pc decreased with increasing [O3] with an average decrease of 10% for an increase in [O3] of 10 ppb, and which was similar to changes in above-ground dry mass production of the stands. Absolute daily net photosynthesis of lower layers was very low and thus the decrease in photosynthesis in the lower canopy caused by elevated [O3] had only minor significance for total canopy photosynthesis. Sensitivity analyses revealed that the decrease in Pc was associated with changes in leaf ecophysiology but not with decrease in leaf area. The soybean stands were very crowded, the leaves were highly mutually shaded, and sufficient light for positive carbon balance did not penetrate to lower canopy leaves, even under elevated [O3].

  19. Canopy reflectance related to marsh dieback onset and progression in Coastal Louisiana

    USGS Publications Warehouse

    Ramsey, Elijah W.; Rangoonwala, A.

    2006-01-01

    In this study, we extended previous work linking leaf spectral changes, dieback onset, and progression of Spartina alterniflora marshes to changes in site-specific canopy reflectance spectra. First, we obtained canopy reflectance spectra (approximately 20 m ground resolution) from the marsh sites occupied during the leaf spectral analyses and from additional sites exhibiting visual signs of dieback. Subsequently, the canopy spectra were analyzed at two spectral scales: the first scale corresponded to whole-spectra sensors, such as the NASA Earth Observing-1 (EO-1) Hyperion, and the second scale corresponded to broadband spectral sensors, such as the EO-1 Advanced Land Imager and the Landsat Enhanced Thematic Mapper. In the whole-spectra analysis, spectral indicators were generated from the whole canopy spectra (about 400 nm to 1,000 nm) by extracting typical dead and healthy marsh spectra, and subsequently using them to determine the percent composition of all canopy reflectance spectra. Percent compositions were then used to classify canopy spectra at each field site into groups exhibiting similar levels of dieback progression ranging from relatively healthy to completely dead. In the broadband reflectance analysis, blue, green, red, red-edge, and near infrared (NIR) spectral bands and NIR/green and NIR/red transforms were extracted from the canopy spectra. Spectral band and band transform indicators of marsh dieback and progression were generated by relating them to marsh status indicators derived from classifications of the 35 mm slides collected at the same time as the canopy reflectance recordings. The whole spectra and broadband spectral indicators were both able to distinguish (a) healthy marsh, (b) live marsh impacted by dieback, and (c) dead marsh, and they both provided some discrimination of dieback progression. Whole-spectra resolution sensors like the EO-1 Hyperion, however, offered an enhanced ability to categorize dieback progression. ?? 2006

  20. 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

  1. Canopy Spectral Invariants. Part 2; Application to Classification of Forest Types from Hyperspectral Data

    NASA Technical Reports Server (NTRS)

    Schull, M. A.; Knyazikhin, Y.; Xu, L.; Samanta, A.; Carmona, P. L.; Lepine, L.; Jenkins, J. P.; Ganguly, S.; Myneni, R. B.

    2011-01-01

    Many studies have been conducted to demonstrate the ability of hyperspectral data to discriminate plant dominant species. Most of them have employed the use of empirically based techniques, which are site specific, requires some initial training based on characteristics of known leaf and/or canopy spectra and therefore may not be extendable to operational use or adapted to changing or unknown land cover. In this paper we propose a physically based approach for separation of dominant forest type using hyperspectral data. The radiative transfer theory of canopy spectral invariants underlies the approach, which facilitates parameterization of the canopy reflectance in terms of the leaf spectral scattering and two spectrally invariant and structurally varying variables - recollision and directional escape probabilities. The methodology is based on the idea of retrieving spectrally invariant parameters from hyperspectral data first, and then relating their values to structural characteristics of three-dimensional canopy structure. Theoretical and empirical analyses of ground and airborne data acquired by Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) over two sites in New England, USA, suggest that the canopy spectral invariants convey information about canopy structure at both the macro- and micro-scales. The total escape probability (one minus recollision probability) varies as a power function with the exponent related to the number of nested hierarchical levels present in the pixel. Its base is a geometrical mean of the local total escape probabilities and accounts for the cumulative effect of canopy structure over a wide range of scales. The ratio of the directional to the total escape probability becomes independent of the number of hierarchical levels and is a function of the canopy structure at the macro-scale such as tree spatial distribution, crown shape and size, within-crown foliage density and ground cover. These properties allow for the natural

  2. Canopy bidirectional reflectance dependence on leaf orientation

    NASA Technical Reports Server (NTRS)

    Brakke, Thomas W.; Otterman, Joseph

    1990-01-01

    The dependence of the bidirectional reflectance (BR) on the inclination and azimuthal orientation of a leaf is analyzed, with the primary assumption that, in terms of both obscuration and shadowing, the entire canopy consists of the same leaves. The BR patterns of a dense canopy are examined as a function of canopy architecture. It is assumed that the leaves are opaque Lambertian reflectors, having identical orientation and relfecting properties throughout the canopy, and distributed randomly with respect to the the irradiation field and the viewing direction. Analytical expressions are presented and analyzed for the BR factor. It is noted that maximal BR occurs at large viewing zenith angles. A complex and often steep dependence of the BR on azimuthal location is reported, noting that the BR thus depends on the leaf azimuth as well as the zenith angle. It is concluded that the question of azimuthal distribution has to be addressed when conducting model inversions to infer canopy characteristics and architecture.

  3. Effects of vegetation canopy structure on remotely sensed canopy temperatures. [inferring plant water stress and yield

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.

    1979-01-01

    The effects of vegetation canopy structure on thermal infrared sensor response must be understood before vegetation surface temperatures of canopies with low percent ground cover can be accurately inferred. The response of a sensor is a function of vegetation geometric structure, the vertical surface temperature distribution of the canopy components, and sensor view angle. Large deviations between the nadir sensor effective radiant temperature (ERT) and vegetation ERT for a soybean canopy were observed throughout the growing season. The nadir sensor ERT of a soybean canopy with 35 percent ground cover deviated from the vegetation ERT by as much as 11 C during the mid-day. These deviations were quantitatively explained as a function of canopy structure and soil temperature. Remote sensing techniques which determine the vegetation canopy temperature(s) from the sensor response need to be studied.

  4. Another definition of forest canopy height

    NASA Astrophysics Data System (ADS)

    Nakai, T.; Sumida, A.; Kodama, Y.; Hara, T.

    2008-12-01

    Forest canopy height, the height of the highest vegetation components above ground level, is essential in normalizing micrometeorological parameters and in estimating forest biomass and carbon pools, but previous definitions of forest canopy height from inventory data bear uncertainties owing to arbitrary criteria of tall trees accounting for top height (i.e. mean height of tall trees selected by a certain definition) or to the effect of many shorter understory trees on Lorey's mean height (i.e. mean height weighted by basal area). We proposed a new concept of forest canopy height: the representative height of taller trees composing the crown surface or the upper canopy layer estimated on the basis of cumulative basal area from the shortest tree plotted against corresponding individual tree height. Because tall trees have large basal area, the cumulative basal area showing a sigmoidal curve would have an inflection point at a height class where many tall trees occur. Hence the forest canopy height is defined as the inflection point of the sigmoid function fitted to the cumulative basal area curve. This new forest canopy height is independent of the presence or absence of many shorter understory trees unlike Lorey's mean height, and is free from the definition of selecting the trees composing the upper canopy to determine their mean height. Applying this concept to actual forests, we found the new canopy height was larger than the arithmetic mean height and Lorey's mean height, and it was close to the aerodynamic canopy height determined by micrometeorological method, not only in the birch forest (even-aged pure stand) but also in the complex mixed forest of evergreen conifer and deciduous broadleaf species. Therefore the new canopy height would be suitable for intersite comparison studies and ground truth for remote sensing such as airborne laser scanning (ALS).

  5. Multidisciplinary Research on Canopy Photosynthetic Productivity in a Cool-Temperate Deciduous Broadleaf Forest in Japan

    NASA Astrophysics Data System (ADS)

    Muraoka, H.; Noda, H. M.; Saitoh, T. M.; Nagai, S.

    2014-12-01

    Forest canopy has crucial roles in regulating energy and material exchange between the atmosphere and terrestrial ecosystems and in ecological processes with respect to carbon cycle and growth in the ecosystems. Challenges to the canopy of tall forests for such research involve the access to the leaves for ecophysiological observations, responses of leaves to the changing environments from seconds to years, and up-scaling the leaf-level phenomena to canopy and landscape-levels. A long-term, multidisciplinary approach has been conducted in a cool-temperate deciduous broadleaf forest in Takayama site (ca. 1400m a.s.l.) in central Japan. This forest canopy is dominated by Quercus crispula and Betula ermanii. We have been focusing on the phenology of photosynthetic productivity from a single leaf to canopy, and to landscape level, by combining leaf ecophysiological research, optical observations by spectroradiometers and time-laps cameras with the aid of "Phenological Eyes Network (PEN)", and process-based modellings. The canopy-level photosynthesis is then compared with the micrometeorolgical observation of CO2 flux at the site. So far we have been clarifying that (1) inter-annual variations in seasonal growth rate and senescence rate of leaf photosynthetic capacity and canopy leaf area are largely responsible for the inter-annual change in forest photosynthesis, and (2) spectral vegetation indices such as enhanced vegetation index (EVI) and chlorophyll index (CCI) can be the indicator to observe the phenology of forest canopy photosynthesis. In addition to these efforts since 2003, we established an open-field warming experiment on the branches of the canopy trees, to investigate the possible influence of temperature increase on leaf photosynthetic and optical properties and then to examine whether the optical satellite remote sensing can detect the changes in photosynthetic capacity and phenology by ongoing global warming.

  6. Stochastic Transport Theory for Investigating the Three-Dimensional Canopy Structure from Space Measurements

    NASA Technical Reports Server (NTRS)

    Huang, Dong; Knyazikhin, Yuri; Wang, Weile; Deering, Donald W,; Stenberg, Pauline; Shabanov, Nikolay; Tan, Bin; Myneni, Ranga B.

    2008-01-01

    Radiation reflected from vegetation canopies exhibits high spatial variation. Satellite-borne sensors measure the mean intensities emanating from heterogeneous vegetated pixels. The theory of radiative transfer in stochastic media provides the most logical linkage between satellite observations and the three-dimensional canopy structure through a closed system of simple equations which contains the mean intensity and higher statistical moments directly as its unknowns. Although this theory has been a highly active research field in recent years, its potential for satellite remote sensing of vegetated surfaces has not been fully realized because of the lack of models of a canopy pair-correlation function that the stochastic radiative transfer equations require. The pair correlation function is defined as the probability of finding simultaneously phytoelements at two points. This paper presents analytical and Monte Carlo generated pair correlation functions. Theoretical and numerical analyses show that the spatial correlation between phytoelements is primarily responsible for the effects of the three-dimensional canopy structure on canopy reflective and absorptive properties. The pair correlation function, therefore, is the most natural and physically meaningful measure of the canopy structure over a wide range of scales. The stochastic radiative transfer equations naturally admit this measure and thus provide a powerful means to investigate the three-dimensional canopy structure from space. Canopy reflectances predicted by the stochastic equations are assessed by comparisons with the PARABOLA measurements from coniferous and broadleaf forest stands in the BOREAS Southern Study Areas. The pair correlation functions are derived from data on tree structural parameters collected during field campaigns conducted at these sites. The simulated canopy reflectances compare well with the PARABOLA data.

  7. Performance of the Cray T3D and Emerging Architectures on Canopy QCD Applications

    NASA Astrophysics Data System (ADS)

    Fischler, Mark; Uchima, Mike

    1996-03-01

    The Cray T3D, an MIMD system with NUMA shared memory capabilities and in principle very low communications latency, can support the Canopy framework for grid-oriented applications. CANOPY has been ported to the T3D, with the intent of making it available to a spectrum of users. The performance of the T3D running Canopy has been benchmarked on five QCD applications extensively run on ACPMAPS at Fermilab, requiring a variety of data access patterns. The net performance and scaling behavior reveals an efficiency relative to peak Gflops almost identical to that achieved on ACPMAPS. Detailed studies of the major factors impacting performance are presented. Generalizations applying this analysis to the newly emerging crop of commercial systems reveal where their limitations will lie. On these applications, efficiencies of above 25% are not to be expected; eliminating overheads due to Canopy will improve matters, but by less than a factor of two.

  8. NDVI as a predictor of canopy arthropod biomass in the Alaskan arctic tundra.

    PubMed

    Sweet, Shannan K; Asmus, Ashley; Rich, Matthew E; Wingfield, John; Gough, Laura; Boelman, Natalie T

    2015-04-01

    The physical and biological responses to rapid arctic warming are proving acute, and as such, there is a need to monitor, understand, and predict ecological responses over large spatial and temporal scales. The use of the normalized difference vegetation index (NDVI) acquired from airborne and satellite sensors addresses this need, as it is widely used as a tool for detecting and quantifying spatial and temporal dynamics of tundra vegetation cover, productivity, and phenology. Such extensive use of the NDVI to quantify vegetation characteristics suggests that it may be similarly applied to characterizing primary and secondary consumer communities. Here, we develop empirical models to predict canopy arthropod biomass with canopy-level measurements of the NDVI both across and within distinct tundra vegetation communities over four growing seasons in the Arctic Foothills region of the Brooks Range, Alaska, USA. When canopy arthropod biomass is predicted with the NDVI across all four growing seasons, our overall model that includes all four vegetation communities explains 63% of the variance in canopy arthropod biomass, whereas our models specific to each of the four vegetation communities explain 74% (moist tussock tundra), 82% (erect shrub tundra), 84% (riparian shrub tundra), and 87% (dwarf shrub tundra) of the observed variation in canopy arthropod biomass. Our field-based study suggests that measurements of the NDVI made from air- and spaceborne sensors may be able to quantify spatial and temporal variation in canopy arthropod biomass at landscape to regional scales.

  9. Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests.

    PubMed

    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

  10. 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

  11. Steady state stresses in ribbon parachute canopies

    NASA Technical Reports Server (NTRS)

    Garrard, W. L.; Wu, K. Y.; Muramoto, K. K.

    1984-01-01

    An experimental study of the steady state stresses in model ribbon parachute canopies is presented. The distribution of circumferential stress was measured in the horizontal ribbons of two parachutes using Omega sensors. Canopy pressure distributions and overall drag were also measured. Testing was conducted in the University of Minnesota Low-Speed Wind Tunnel at dynamic pressures ranging from 1.0 to 1.5 inches of water. The stresses in the parachute canopies were calculated using the parachute structural analysis code, CANO. It was found that the general shape of the measured and calculated stress distributions was fairly similar; however, the measured stresses were somewhat less than the calculated stresses.

  12. Modeling canopy-level productivity: is the "big-leaf" simplification acceptable?

    NASA Astrophysics Data System (ADS)

    Sprintsin, M.; Chen, J. M.

    2009-05-01

    The "big-leaf" approach to calculating the carbon balance of plant canopies assumes that canopy carbon fluxes have the same relative responses to the environment as any single unshaded leaf in the upper canopy. Widely used light use efficiency models are essentially simplified versions of the big-leaf model. Despite its wide acceptance, subsequent developments in the modeling of leaf photosynthesis and measurements of canopy physiology have brought into question the assumptions behind this approach showing that big leaf approximation is inadequate for simulating canopy photosynthesis because of the additional leaf internal control on carbon assimilation and because of the non-linear response of photosynthesis on leaf nitrogen and absorbed light, and changes in leaf microenvironment with canopy depth. To avoid this problem a sunlit/shaded leaf separation approach, within which the vegetation is treated as two big leaves under different illumination conditions, is gradually replacing the "big-leaf" strategy, for applications at local and regional scales. Such separation is now widely accepted as a more accurate and physiologically based approach for modeling canopy photosynthesis. Here we compare both strategies for Gross Primary Production (GPP) modeling using the Boreal Ecosystem Productivity Simulator (BEPS) at local (tower footprint) scale for different land cover types spread over North America: two broadleaf forests (Harvard, Massachusetts and Missouri Ozark, Missouri); two coniferous forests (Howland, Maine and Old Black Spruce, Saskatchewan); Lost Creek shrubland site (Wisconsin) and Mer Bleue petland (Ontario). BEPS calculates carbon fixation by scaling Farquhar's leaf biochemical model up to canopy level with stomatal conductance estimated by a modified version of the Ball-Woodrow-Berry model. The "big-leaf" approach was parameterized using derived leaf level parameters scaled up to canopy level by means of Leaf Area Index. The influence of sunlit

  13. Ecohydrological responses of dense canopies to environmental variability: 1. Interplay between vertical structure and photosynthetic pathway

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    Vegetation acclimation to changing climate, in particular elevated atmospheric concentrations of carbon dioxide (CO2), has been observed to include modifications to the biochemical and ecophysiological functioning of leaves and the structural components of the canopy. These responses have the potential to significantly modify plant carbon uptake and surface energy partitioning, and have been attributed with large-scale changes in surface hydrology over recent decades. While the aggregated effects of vegetation acclimation can be pronounced, they often result from subtle changes in canopy properties that require the resolution of physical, biochemical and ecophysiological processes through the canopy for accurate estimation. In this paper, the first of two, a multilayer canopy-soil-root system model developed to capture the emergent vegetation responses to environmental change is presented. The model incorporates both C3 and C4 photosynthetic pathways, and resolves the vertical radiation, thermal, and environmental regimes within the canopy. The tight coupling between leaf ecophysiological functioning and energy balance determines vegetation responses to climate states and perturbations, which are modulated by soil moisture states through the depth of the root system. The model is validated for three growing seasons each for soybean (C3) and maize (C4) using eddy-covariance fluxes of CO2, latent, and sensible heat collected at the Bondville (Illinois) Ameriflux tower site. The data set provides an opportunity to examine the role of important environmental drivers and model skill in capturing variability in canopy-atmosphere exchange. Vertical variation in radiative states and scalar fluxes over a mean diurnal cycle are examined to understand the role of canopy structure on the patterns of absorbed radiation and scalar flux magnitudes and the consequent differences in sunlit and shaded source/sink locations through the canopies. An analysis is made of the impact of

  14. Canopy reflectance modelling of semiarid vegetation

    NASA Technical Reports Server (NTRS)

    Franklin, Janet

    1994-01-01

    Three different types of remote sensing algorithms for estimating vegetation amount and other land surface biophysical parameters were tested for semiarid environments. These included statistical linear models, the Li-Strahler geometric-optical canopy model, and linear spectral mixture analysis. The two study areas were the National Science Foundation's Jornada Long Term Ecological Research site near Las Cruces, NM, in the northern Chihuahuan desert, and the HAPEX-Sahel site near Niamey, Niger, in West Africa, comprising semiarid rangeland and subtropical crop land. The statistical approach (simple and multiple regression) resulted in high correlations between SPOT satellite spectral reflectance and shrub and grass cover, although these correlations varied with the spatial scale of aggregation of the measurements. The Li-Strahler model produced estimated of shrub size and density for both study sites with large standard errors. In the Jornada, the estimates were accurate enough to be useful for characterizing structural differences among three shrub strata. In Niger, the range of shrub cover and size in short-fallow shrublands is so low that the necessity of spatially distributed estimation of shrub size and density is questionable. Spectral mixture analysis of multiscale, multitemporal, multispectral radiometer data and imagery for Niger showed a positive relationship between fractions of spectral endmembers and surface parameters of interest including soil cover, vegetation cover, and leaf area index.

  15. A state-space modeling approach to estimating canopy conductance and associated uncertainties from sap flux density data.

    PubMed

    Bell, David M; Ward, Eric J; Oishi, A Christopher; Oren, Ram; Flikkema, Paul G; Clark, James S

    2015-07-01

    Uncertainties in ecophysiological responses to environment, such as the impact of atmospheric and soil moisture conditions on plant water regulation, limit our ability to estimate key inputs for ecosystem models. Advanced statistical frameworks provide coherent methodologies for relating observed data, such as stem sap flux density, to unobserved processes, such as canopy conductance and transpiration. To address this need, we developed a hierarchical Bayesian State-Space Canopy Conductance (StaCC) model linking canopy conductance and transpiration to tree sap flux density from a 4-year experiment in the North Carolina Piedmont, USA. Our model builds on existing ecophysiological knowledge, but explicitly incorporates uncertainty in canopy conductance, internal tree hydraulics and observation error to improve estimation of canopy conductance responses to atmospheric drought (i.e., vapor pressure deficit), soil drought (i.e., soil moisture) and above canopy light. Our statistical framework not only predicted sap flux observations well, but it also allowed us to simultaneously gap-fill missing data as we made inference on canopy processes, marking a substantial advance over traditional methods. The predicted and observed sap flux data were highly correlated (mean sensor-level Pearson correlation coefficient = 0.88). Variations in canopy conductance and transpiration associated with environmental variation across days to years were many times greater than the variation associated with model uncertainties. Because some variables, such as vapor pressure deficit and soil moisture, were correlated at the scale of days to weeks, canopy conductance responses to individual environmental variables were difficult to interpret in isolation. Still, our results highlight the importance of accounting for uncertainty in models of ecophysiological and ecosystem function where the process of interest, canopy conductance in this case, is not observed directly. The StaCC modeling

  16. Insights to fossil and geochemical archives of forest structure from foliar flux, isotopic and biomarker gradients in modern canopies

    NASA Astrophysics Data System (ADS)

    Graham, H. V.; Patzkowsky, M.; Wing, S. L.; Freeman, K. H.

    2012-12-01

    Paleoecologists and paleoclimatologists alike are interested in the geological history of closed-canopy forests because of their evolutionary and climatic significance. In order to develop chemical tools for inferring closed-canopy forests in the geological record we have studied the relationships among foliar carbon isotope compositions (δ13C), litter flux and leaf-wax properties in the context of environmental gradients (light, moisture, CO2) within extant forest canopies. Leaves in a tropical closed-canopy forest exhibit a greater range of vertical isotopic enrichment (10‰) compared with similarly sampled temperate open-canopy forest (6‰). We used these data and a statistical resampling (bootstrap) method to form expectations for isotopic variation in fossil leaf assemblages and sediments that formed under different forest types. According to this model, there is a robust likelihood of identifying canopy closure by isotopic analysis of as few as 50 fossil leaves selected randomly. By sampling many thousands of leaves, the model estimates the influence of leaf biomass on organic matter in ancient soils and other terrestrial archives. The model predicts that soil organic matter in a tropical closed-canopy will be ~1‰ more depleted than in a temperate open-canopy forest. Modeled closed-canopy litter coincides with observed δ13C values for litterfall and humic soils in the tropical forest. Despite variability within a canopy and among individual leaves and species, sedimentary organic matter potentially captures global-scale biome patterns, provided diagenetic influences can be constrained. Thus to allow insights to isotopic differences between litter input and preserved signals in ancient environments, we can incorporate biomarker abundance and isotopic data for six n-alkanes (n-C25 to n-C35) into the model. This model allows us to predict the sediment lipid profiles that would result from a variety of canopy conditions and taxonomic dominance patterns.

  17. VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine

    PubMed Central

    De Bei, Roberta; Fuentes, Sigfredo; Gilliham, Matthew; Tyerman, Steve; Edwards, Everard; Bianchini, Nicolò; Smith, Jason; Collins, Cassandra

    2016-01-01

    Leaf area index (LAI) and plant area index (PAI) are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI), canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants. PMID:27120600

  18. A canopy-type similarity model for wind farm optimization

    NASA Astrophysics Data System (ADS)

    Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando

    2013-04-01

    The atmospheric boundary layer (ABL) flow through and over wind farms has been found to be similar to canopy-type flows, with characteristic flow development and shear penetration length scales (Markfort et al., 2012). Wind farms capture momentum from the ABL both at the leading edge and from above. We examine this further with an analytical canopy-type model. Within the flow development region, momentum is advected into the wind farm and wake turbulence draws excess momentum in from between turbines. This spatial heterogeneity of momentum within the wind farm is characterized by large dispersive momentum fluxes. Once the flow within the farm is developed, the area-averaged velocity profile exhibits a characteristic inflection point near the top of the wind farm, similar to that of canopy-type flows. The inflected velocity profile is associated with the presence of a dominant characteristic turbulence scale, which may be responsible for a significant portion of the vertical momentum flux. Prediction of this scale is useful for determining the amount of available power for harvesting. The new model is tested with results from wind tunnel experiments, which were conducted to characterize the turbulent flow in and above model wind farms in aligned and staggered configurations. The model is useful for representing wind farms in regional scale models, for the optimization of wind farms considering wind turbine spacing and layout configuration, and for assessing the impacts of upwind wind farms on nearby wind resources. Markfort CD, W Zhang and F Porté-Agel. 2012. Turbulent flow and scalar transport through and over aligned and staggered wind farms. Journal of Turbulence. 13(1) N33: 1-36. doi:10.1080/14685248.2012.709635.

  19. Interaction between photons and leaf canopies

    NASA Technical Reports Server (NTRS)

    Knyazikhin, Yuri V.; Marshak, Alexander L.; Myneni, Ranga B.

    1991-01-01

    The physics of neutral particle interaction for photons traveling in media consisting of finite-dimensional scattering centers that cross-shade mutually is investigated. A leaf canopy is a typical example of such media. The leaf canopy is idealized as a binary medium consisting of randomly distributed gaps (voids) and regions with phytoelements (turbid phytomedium). In this approach, the leaf canopy is represented by a combination of all possible open oriented spheres. The mathematical approach for characterizing the structure of the host medium is considered. The extinction coefficient at any phase-space location in a leaf canopy is the product of the extinction coefficient in the turbid phytomedium and the probability of absence gaps at that location. Using a similar approach, an expression for the differential scattering coefficient is derived.

  20. Canopy architecture of a walnut orchard

    NASA Technical Reports Server (NTRS)

    Ustin, Susan L.; Martens, Scott N.; Vanderbilt, Vern C.

    1991-01-01

    A detailed dataset describing the canopy geometry of a walnut orchard was acquired to support testing and comparison of the predictions of canopy microwave and optical inversion models. Measured canopy properties included the quantity, size, and orientation of stems, leaves, and fruit. Eight trees receiving 100 percent of estimated potential evapotranspiration water use and eight trees receiving 33 percent of potential water use were measured. The vertical distributions of stem, leaf, and fruit properties are presented with respect to irrigation treatment. Zenith and probability distributions for stems and leaf normals are presented. These data show that, after two years of reduced irrigation, the trees receiving only 33 percent of their potential water requirement had reduced fruit yields, lower leaf area index, and altered allocation of biomass within the canopy.

  1. Vortex generation in oscillatory canopy flow

    NASA Astrophysics Data System (ADS)

    Ghisalberti, Marco; Schlosser, Tamara

    2013-03-01

    In this paper, we demonstrate for the first time the generation of coherent vortices at the top of a canopy in oscillatory (i.e., wave-dominated) flow. Through a series of flow visualization experiments, vortex formation is shown to occur when two conditions described by the Keulegan-Carpenter (KC) and Reynolds (Re) numbers are met. First, the wave period must be sufficiently long to allow the generation of the shear-driven instability at the top of the canopy; this occurs when KC ≳ 5. Second, the vortex instability must be able to overcome the stabilizing effects of viscosity; this occurs when Re ≳ 1000. The vortices greatly increase the rate of vertical mixing within the canopy, such that any prediction of residence time in a coastal canopy requires an understanding of whether vortex generation is occurring.

  2. Habitat use by the endangered Karner blue butterfly in oak woodlands: The influence of canopy cover

    USGS Publications Warehouse

    Grundel, Ralph; Pavlovic, Noel B.; Sulzman, Christina L.

    1998-01-01

    The Karner blue butterfly Lycaeides melissa samuelis is an endangered species residing in the Great Lakes and northeastern regions of the United States. Increased canopy cover is a major factor implicated in the decline of the Karner blue at many locales. Therefore, we examined how the butterfly's behavior varied with canopy cover. Adult males at Indiana Dunes National Lakeshore used habitat under canopy openings for nearly 90% of their activities; females used openings and shaded areas more equally. The frequency of oviposition on the sole host plant, wild lupine Lupinus perennis, was highest under 30–60% canopy cover even though lupine was more abundant in more open areas. Larvae fed preferentially on larger lupine plants and on lupines in denser patches. However, lupines were generally larger in the shade. Therefore, shade-related trade-offs existed between lupine abundance and distribution of larval feeding and oviposition. Also, heterogeneity of shading by sub-canopy woody vegetation was greater at oviposition sites than at sites where lupine did not grow. Given the importance of shade heterogeneity, a mixture of canopy openings and shade, on a scale similar to daily adult movement range, should be beneficial for this butterfly.

  3. Weak vertical canopy gradients of photosynthetic capacities and stomatal responses in a fertile Norway spruce stand.

    PubMed

    Tarvainen, Lasse; Wallin, Göran; Uddling, Johan

    2013-12-01

    The sensitivity of carbon (C) assimilation to within-canopy nitrogen (N) allocation and of stomatal conductance (g s) to environmental variables were investigated along a vertical canopy gradient in a fertile Norway spruce [Picea abies (L.) Karst.] stand. Maximum rates of ribulose bisphosphate-saturated carboxylation (V (cmax)) and electron transport (J (max)) exhibited weak relationships with needle N content. Using these relationships together with a combined stomatal-photosynthesis model, it was found that the sensitivity of C assimilation of 12 1-year old shoots to within-canopy N allocation pattern was very weak. Modelled C assimilation based on optimal compared to observed N allocation pattern increased by only 1-2 %, and altering total needle N content by ± 30 % resulted in a 2-4 % change in modelled C assimilation. C assimilation was more sensitive to water use and changed by 8-12 % in response to ± 30 % altered stomatal conductance. No indications of significant limitations of photosynthesis by other nutrients or non-optimal within-canopy allocation of water were detected. The sensitivity of g s to photosynthetic photon flux density (PPFD) was found to be stronger in the lower canopy, while no significant within-canopy variation was observed in light-saturated g( s) or stomatal sensitivity to vapour pressure deficit (VPD). The results of this study show that, at this N rich site, photosynthesis integrated for shoots at different canopy positions is only marginally affected by N allocation pattern and that increased stand-scale N availability would only be truly beneficial to canopy photosynthesis if it resulted in increased leaf area.

  4. Interactions between Fragmented Seagrass Canopies and the Local Hydrodynamics

    PubMed Central

    El Allaoui, Nazha; Colomer, Jordi; Soler, Marianna; Casamitjana, Xavier; Oldham, Carolyn

    2016-01-01

    The systematic creation of gaps within canopies results in fragmentation and the architecture of fragmented canopies differs substantially from non-fragmented canopies. Canopy fragmentation leads to spatial heterogeneity in hydrodynamics and therefore heterogeneity in the sheltering of canopy communities. Identifying the level of instability due to canopy fragmentation is important for canopies in coastal areas impacted by human activities and indeed, climate change. The gap orientation relative to the wave direction is expected to play an important role in determining wave attenuation and sheltering. Initially we investigated the effect of a single transversal gap within a canopy (i.e. a gap oriented perpendicular to the wave direction) on hydrodynamics, which was compared to fully vegetated canopies (i.e. no gaps) and also to bare sediment. The wave velocity increased with gap width for the two canopy densities studied (2.5% and 10% solid plant fraction) reaching wave velocities found over bare sediments. The turbulent kinetic energy (TKE) within the gap also increased, but was more attenuated by the adjacent vegetation than the wave velocity. As expected, denser canopies produced a greater attenuation of both the wave velocity and the turbulent kinetic energy within an adjacent gap, compared to sparse canopies. Using non-dimensional analysis and our experimental data, a parameterization for predicting TKE in a canopy gap was formulated, as a function of easily measured variables. Based on the experimental results, a fragmented canopy model was then developed to determine the overall mixing level in such canopies. The model revealed that canopies with large gaps present more mixing than canopies with small gaps despite having the same total gap area in the canopy. Furthermore, for the same total gap area, dense fragmented canopies provide more shelter than sparse fragmented canopies. PMID:27227321

  5. Plant Canopy Temperature and Heat Flux Profiles: What Difference Does an Isothermal Skin Make?

    NASA Astrophysics Data System (ADS)

    Crago, R. D.; Qualls, R. J.

    2015-12-01

    Land surface temperature Ts plays a vital role in the determination of sensible (H) and latent heat flux, upwelling long-wave radiation, and ground heat flux. While it is widely recognized that there is a range of skin temperatures represented in even a homogeneous canopy, it is often necessary or convenient to treat the surface as isothermal. This study investigates, at the sub-canopy scale, the implications of assuming that a canopy is isothermal. The focus is on profiles within the canopy of air, foliage, and soil surface temperature, and of sensible and latent heat flux source strength. Data from a dense grassland at the Southern Great Plains experiment in 1997 (SGP97) were used to assess the ability of a multi-layer canopy model to match measured sensible and latent heat fluxes along with radiometric surface temperatures. In its standard mode, the model solves the energy balance for each canopy layer and uses Localized Near Field (LNF) theory to model the turbulent transport. The results suggest the model captures the most important features of canopy flux generation and transport, and support its use to investigate scalar profiles within canopies. For 112 data points at SGP97, the model produced realistic temperature and sensible heat flux source profiles. In addition, it was run in a mode that seeks the isothermal (soil and foliage) skin temperature (Ti) that provides the same Hproduced by the model in its standard mode. This produces profiles of air and foliage temperature and of sensible heat source strength that differ significantly from profiles from the standard mode. Based on these simulations, realistic canopies may have a mixture of positive and negative sensible heat flux sources at various heights, typically with large contributions from the soil surface. There is frequently a discontinuity between foliage temperatures near the soil and the actual soil surface temperature. For isothermal canopies, heat sources at all levels had the same sign and

  6. In situ hyperspectral data analysis for canopy chlorophyll content estimation of an invasive species spartina alterniflora based on PROSAIL canopy radiative transfer model

    NASA Astrophysics Data System (ADS)

    Ai, Jinquan; Gao, Wei; Shi, Runhe; Zhang, Chao; Sun, Zhibin; Chen, Wenhui; Liu, Chaoshun; Zeng, Yuyan

    2015-09-01

    Spartina alterniflora is one of the most serious invasive species in the coastal saltmarshes of China. An accurate quantitative estimation of its canopy leaf chlorophyll content is of great importance for monitoring plant physiological state and vegetation productivity. Hyperspectral reflectance data representing a range of canopy chlorophyll content were simulated by using the PROSAIL radiative transfer model at a 1nm sampling interval, which was based on prior knowledge of S.alterniflora. A set of indices was tested for estimating canopy chlorophyll content. Subsequently, validation were performed for testing the performance of indices, based on the PROSAIL model using in situ data measured by a Spectroradiometer with spectral range of 350-2500nm in a late autumn in a sub-tropical estuarine marsh. PROSAIL simulations showed that the most readily available indices were not good to be directly used in canopy chlorophyll estimation of S.alterniflora. The modified Chlorophyll Absorption in Reflectance Index MCARI[705,750] was linear related to the canopy chlorophyll content (R2=0.94) , but did not achieve a satisfactory estimation results with a high RMSE (RMSE=0.95 g.m-2). We optimized the index MCARI[705,750] by introducing a scale conversion coefficient to the formula to solve data units inconsistent, which is between the practical application unit and the unit used in the process of establishing the index, and balance scale transformation through radiative transfer models and examing corresponding canopy reflectance index values. We proposed index Optimized modified Chlorophyll Absorption in Reflectance Index OMCARI[705, 750]. The results showed that the index OMCARI[705, 750] had higher precision of prediction of chlorophyll for S.alterniflora (R2=0.94,RMSE=0.41 g.m-2 ).

  7. Experimental Methods Using Photogrammetric Techniques for Parachute Canopy Shape Measurements

    NASA Technical Reports Server (NTRS)

    Jones, Thomas W.; Downey, James M.; Lunsford, Charles B.; Desabrais, Kenneth J.; Noetscher, Gregory

    2007-01-01

    NASA Langley Research Center in partnership with the U.S. Army Natick Soldier Center has collaborated on the development of a payload instrumentation package to record the physical parameters observed during parachute air drop tests. The instrumentation package records a variety of parameters including canopy shape, suspension line loads, payload 3-axis acceleration, and payload velocity. This report discusses the instrumentation design and development process, as well as the photogrammetric measurement technique used to provide shape measurements. The scaled model tests were conducted in the NASA Glenn Plum Brook Space Propulsion Facility, OH.

  8. Validating spatial structure in canopy water content using geostatistics

    NASA Technical Reports Server (NTRS)

    Sanderson, E. W.; Zhang, M. H.; Ustin, S. L.; Rejmankova, E.; Haxo, R. S.

    1995-01-01

    Heterogeneity in ecological phenomena are scale dependent and affect the hierarchical structure of image data. AVIRIS pixels average reflectance produced by complex absorption and scattering interactions between biogeochemical composition, canopy architecture, view and illumination angles, species distributions, and plant cover as well as other factors. These scales affect validation of pixel reflectance, typically performed by relating pixel spectra to ground measurements acquired at scales of 1m(exp 2) or less (e.g., field spectra, foilage and soil samples, etc.). As image analysis becomes more sophisticated, such as those for detection of canopy chemistry, better validation becomes a critical problem. This paper presents a methodology for bridging between point measurements and pixels using geostatistics. Geostatistics have been extensively used in geological or hydrogeolocial studies but have received little application in ecological studies. The key criteria for kriging estimation is that the phenomena varies in space and that an underlying controlling process produces spatial correlation between the measured data points. Ecological variation meets this requirement because communities vary along environmental gradients like soil moisture, nutrient availability, or topography.

  9. Consistent Coupling of Canopy Structure with Stem Diameter Distributions and Demography Reveals Organizing Principles of Amazonian Forest Architecture

    NASA Astrophysics Data System (ADS)

    Stark, S. C.; Enquist, B. J.; Saleska, S. R.; Leitold, V.; de Castilho, C. V.; Longo, M.; Alves, L. F.; Schietti, J.; Costa, F. R.; Shimabukuro, Y. E.; Lefsky, M. A.; Camargo, P. B.; de Oliveira, R. C.

    2013-12-01

    The spatial structure of leaf area and light in forest canopies (canopy structure) critically influences ecosystem production and forest dynamics. Increasing light limitation (H1) with greater depth in the canopy may influence growth, mortality and the fluxes of individuals over size classes, which in turn determine the distribution of individuals over tree size (diameter distribution). On the other hand, physiological adaptations may allow trees to grow and survive in low light such that competition for canopy space (H2) regulates demographic fluxes and the diameter distribution. While there is acute need for theory that connects canopy structure with forest dynamics to predict the consequences of global increases in tree mortality, these hypotheses remain little explored and have never been evaluated in a model framework that quantitatively links (i) observations of canopy structure including light and leaf area, (ii) tree demography and (iii) diameter distributions. Building from metabolic scaling theory of tree architecture, we provide such a framework and show that diameter distributions from two sites with contrasting dynamics in the central Amazon can be predicted from remote observations of canopy structure, but only by incorporating crown plasticity to enhance light interception (H3). Uniquely, we derived light absorption estimates for size classes from this model and compared these estimates with plot-based observations of demographic transitions. We found similar relationships between absorption and demographic flux rates in sites, in spite of large differences in patterns of growth and mortality over tree size. This suggested that competition for canopy space may coordinate demographic rates and influence diameter distributions, but with an additional consistent influence of light limitation. Site differences in light absorption over tree size, furthermore, partially explained site differences in diameter distributions. The rapid remote detection of

  10. Backscattering of Individual LIDAR Pulses from Forest Canopies Explained by Photogrammetrically Derived Vegetation Structure

    NASA Astrophysics Data System (ADS)

    Korpela, I.; Hovi, A.; Korhonen, L.

    2013-05-01

    In recent years, airborne LiDAR sensors have shown remarkable performance in the mapping of forest vegetation. This experimental study looks at LiDAR data at the scale of individual pulses to elucidate the sources behind interpulse variation in backscattering. Close-range photogrammetry was used for obtaining the canopy reference measurements at the ratio scale. The experiments illustrated different orientation techniques in the field, LiDAR acquisitions and photogrammetry in both leaf-on and leaf-off conditions, and two-waveform recording LiDAR sensors. The intrafootprint branch silhouettes in zenith-looking images, in which the camera, footprint, and LiDAR sensor were collinear, were extracted and contrasted with LiDAR backscattering. An enhanced planimetric match (refinement of strip matching) was achieved by shifting the pulses in a strip and searching for the maximal correlation between the silhouette and LiDAR intensity. The relative silhouette explained up to 80-90% of the interpulse variation. We tested whether accounting for the Gaussian spread of intrafootprint irradiance would improve the correlations, but the effect was blurred by small-scale geometric noise. Accounting for receiver gain variations in the Leica ALS60 sensor data strengthened the dependences. The size of the vegetation objects required for triggering a LiDAR observation was analyzed. We demonstrated the use of LiDAR pulses adjacent to canopy vegetation, which did not trigger a canopy echo, for canopy mapping. Pulses not triggering an echo constitute the complement to the actual canopy. We conclude that field photogrammetry is a useful tool for mapping forest canopies from below and that quantitative analysis is feasible even at the scale of single pulses for enhanced understanding of LiDAR observations from vegetation.

  11. Anisotropy of thermal infrared exitance in sunflower canopies

    NASA Technical Reports Server (NTRS)

    Tha Paw u, Kyaw; Ustin, Susan L.; Zhang, Chang-An

    1989-01-01

    Anisotropy of thermal infrared exitance above and within a relatively closed fully irrigated sunflower canopy is detailed. Azimuthal variation in thermal infrared exitance above canopies was weakly (statistically) related to solar position and was comparable to or larger than errors in satellite-based canopy estimates. Anisotropy within canopies was significantly lower and decreased with canopy closure and depth into the canopy. Measured azimuthal isotropy within canopies supports the use of this assumption in radiative transfer models. Significant differences in canopy temperature measurements were found depending upon whether the instruments were within or above the canopy. These differences could produce errors of 20-35 percent in latent energy estimates during periods of high evapotranspiration (ET) and greater errors in periods of restricted ET.

  12. Elements of a dynamic systems model of canopy photosynthesis.

    PubMed

    Zhu, Xin-Guang; Song, Qingfeng; Ort, Donald R

    2012-06-01

    Improving photosynthesis throughout the full canopy rather than photosynthesis of only the top leaves of the canopy is central to improving crop yields. Many canopy photosynthesis models have been developed from physiological and ecological perspectives, however most do not consider heterogeneities of microclimatic factors inside a canopy, canopy dynamics and associated energetics, or competition among different plants, and most models lack a direct linkage to molecular processes. Here we described the rationale, elements, and approaches necessary to build a dynamic systems model of canopy photosynthesis. A systems model should integrate metabolic processes including photosynthesis, respiration, nitrogen metabolism, resource re-mobilization and photosynthate partitioning with canopy level light, CO(2), water vapor distributions and heat exchange processes. In so doing a systems-based canopy photosynthesis model will enable studies of molecular ecology and dramatically improve our insight into engineering crops for improved canopy photosynthetic CO(2) uptake, resource use efficiencies and yields.

  13. Forest canopy interactions with nucleation mode particles

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.; Novick, K. A.

    2014-11-01

    Ultrafine particle size distributions through a deciduous forest canopy indicate that nucleation mode particle concentrations decline with depth into the canopy, such that number concentrations at the bottom of the canopy are an average of 16% lower than those at the top. However, growth rates of nucleation mode particles (diameters 6-30 nm) are invariant with height within the canopy, which implies that the semi-volatile gases contributing to their growth are comparatively well-mixed through the canopy. Growth rates of nucleation mode particles during a meteorological drought year (2012) were substantially lower than during a meteorologically normal year with high soil water potential (2013). This may reflect suppression of actual biogenic volatile organic compound (BVOC) emissions by drought and thus a reduction in the production of condensable products during the drought-affected vegetation season. This hypothesis is supported by evidence that growth rates during the normal year exhibit a positive correlation with emissions of BVOC modeled on observed forest composition, leaf area index, temperature and photosynthetically active radiation (PAR), but particle growth rates during the drought-affected vegetation season are not correlated with modeled BVOC emissions. These data thus provide indirect evidence that drought stress in forests may reduce BVOC emissions and limit growth of nucleation mode particles to climate-relevant sizes.

  14. Modelling Canopy Flows over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Grant, Eleanor R.; Ross, Andrew N.; Gardiner, Barry A.

    2016-12-01

    Recent studies of flow over forested hills have been motivated by a number of important applications including understanding CO_2 and other gaseous fluxes over forests in complex terrain, predicting wind damage to trees, and modelling wind energy potential at forested sites. Current modelling studies have focussed almost exclusively on highly idealized, and usually fully forested, hills. Here, we present model results for a site on the Isle of Arran, Scotland with complex terrain and heterogeneous forest canopy. The model uses an explicit representation of the canopy and a 1.5-order turbulence closure for flow within and above the canopy. The validity of the closure scheme is assessed using turbulence data from a field experiment before comparing predictions of the full model with field observations. For near-neutral stability, the results compare well with the observations, showing that such a relatively simple canopy model can accurately reproduce the flow patterns observed over complex terrain and realistic, variable forest cover, while at the same time remaining computationally feasible for real case studies. The model allows closer examination of the flow separation observed over complex forested terrain. Comparisons with model simulations using a roughness length parametrization show significant differences, particularly with respect to flow separation, highlighting the need to explicitly model the forest canopy if detailed predictions of near-surface flow around forests are required.

  15. 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.

  16. A laser technique for characterizing the geometry of plant canopies

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Silva, L. F.; Bauer, M. E.

    1977-01-01

    The interception of solar power by the canopy is investigated as a function of solar zenith angle (time), component of the canopy, and depth into the canopy. The projected foliage area, cumulative leaf area, and view factors within the canopy are examined as a function of the same parameters. Two systems are proposed that are capable of describing the geometrical aspects of a vegetative canopy and of operation in an automatic mode. Either system would provide sufficient data to yield a numerical map of the foliage area in the canopy. Both systems would involve the collection of large data sets in a short time period using minimal manpower.

  17. Simulation of solar radiation absorption in vegetation canopies

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.; Smith, J. A.

    1980-01-01

    A solar radiation canopy absorption model, including multiple scattering effects, was developed and tested for a lodgepole pine (Pinus contorta) canopy. Reflectance above the canopy, spectral transmittance to the ground layer, and geometric and spectral measurements of canopy elements were made. Relatively large differentials occurred in spectral absorption by canopy layers, especially in the photosynthetically active region, as a function of solar zenith angle. In addition, the proportion of total global irradiance absorbed by individual layers varied greatly as a function of solar zenith angle. However, absorption by the entire canopy system remained relatively constant.

  18. Reconciling leaf physiological traits and canopy flux data: Use of the TRY and FLUXNET databases in the Community Land Model version 4

    NASA Astrophysics Data System (ADS)

    Bonan, Gordon B.; Oleson, Keith W.; Fisher, Rosie A.; Lasslop, Gitta; Reichstein, Markus

    2012-06-01

    The Community Land Model version 4 overestimates gross primary production (GPP) compared with estimates from FLUXNET eddy covariance towers. The revised model of Bonan et al. (2011) is consistent with FLUXNET, but values for the leaf-level photosynthetic parameterVcmaxthat yield realistic GPP at the canopy-scale are lower than observed in the global synthesis of Kattge et al. (2009), except for tropical broadleaf evergreen trees. We investigate this discrepancy betweenVcmaxand canopy fluxes. A multilayer model with explicit calculation of light absorption and photosynthesis for sunlit and shaded leaves at depths in the canopy gives insight to the scale mismatch between leaf and canopy. We evaluate the model with light-response curves at individual FLUXNET towers and with empirically upscaled annual GPP. Biases in the multilayer canopy with observedVcmaxare similar, or improved, compared with the standard two-leaf canopy and its lowVcmax, though the Amazon is an exception. The difference relates to light absorption by shaded leaves in the two-leaf canopy, and resulting higher photosynthesis when the canopy scaling parameterKn is low, but observationally constrained. Larger Kndecreases shaded leaf photosynthesis and reduces the difference between the two-leaf and multilayer canopies. The low modelVcmaxis diagnosed from nitrogen reduction of GPP in simulations with carbon-nitrogen biogeochemistry. Our results show that the imposed nitrogen reduction compensates for deficiency in the two-leaf canopy that produces high GPP. Leaf trait databases (Vcmax), within-canopy profiles of photosynthetic capacity (Kn), tower fluxes, and empirically upscaled fields provide important complementary information for model evaluation.

  19. Four things we don't know about scalar transfer from plant canopies

    NASA Astrophysics Data System (ADS)

    Finnigan, J. J.

    2009-04-01

    In terrestrial plant canopies, turbulent exchange of water through evapotranspiration is intimately bound up with exchange of other scalars, heat and carbon dioxide in particular. Turbulent transport is rarely the process limiting exchange of these scalars between the biosphere and the atmosphere. However, in measurement programs like FLUXNET or when we parameterise surface exchange at the canopy scale in climate or weather models we must understand the mechanism of turbulent exchange in detail. In this talk we survey four current obstacles to extending our understanding of canopy turbulence from the idealised case of homogeneous flow in neutral stratification to complex flows in stable and unstable conditions. 1. Canopy eddy structure and the hydrodynamic instability Recent analysis of canopy LES and wind tunnel simulations has revealed the ‘two hairpin' structure of a characteristic canopy eddy. This structure explains a large body of results from a wide range of canopies and redefines the Roughness Sub Layer (RSL) as an asymptotic layer similar to the logarithmic and outer layers of the Planetary Boundary Layer. However, the nature of the non-linear ‘mixing-layer' instability process that gives canopy/RSL eddies their coherence and enhanced transport efficiency (as compared to eddies in the logarithmic layer above) is poorly understood so we do not know how resilient this instability and the eddies that depend upon it are to large scale flow perturbations or to changes in stability. 2. Turbulent Schmidt and Prandtl Numbers The scalar RSL can be defined as the layer across which the turbulent Schmidt (Sc) and Prandtl (Pr) numbers in neutral stratification change from their canopy top values of ~0.5, typical of mixing layers, to their logarithmic layer values of ~1.0, typical of boundary layers. The value of Sc or Pr is a critical parameter when adjusting Monin-Obukhov similarity theory (MOST) for the proximity of the canopy. The need for such adjustments has

  20. BOREAS TE-9 NSA Canopy Biochemistry

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Charest, Martin; Sy, Mikailou

    2000-01-01

    The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves. This data set contains canopy biochemistry data collected in 1994 in the NSA at the YJP, OJR, OBS, UBS, and OA sites, including biochemistry lignin, nitrogen, cellulose, starch, and fiber concentrations. These data were collected to study the spatial and temporal changes in the canopy biochemistry of boreal forest cover types and how a high-resolution radiative transfer model in the mid-infrared could be applied in an effort to obtain better estimates of canopy biochemical properties using remote sensing. The data are available 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) Distributed Active Archive Center (DAAC).

  1. Large eddy simulations as a parameterization tool for canopy-structure X VOC-flux interactions

    NASA Astrophysics Data System (ADS)

    Kenny, William; Bohrer, Gil; Chatziefstratiou, Efthalia

    2015-04-01

    We have been working to develop a new post-processing model - High resolution VOC Atmospheric Chemistry in Canopies (Hi-VACC) - which resolves the dispersion and chemistry of reacting chemical species given their emission rates from the vegetation and soil, driven by high resolution meteorological forcing and wind fields from various high resolution atmospheric regional and large-eddy simulations. Hi-VACC reads in fields of pressure, temperature, humidity, air density, short-wave radiation, wind (3-D u, v and w components) and sub-grid-scale turbulence that were simulated by a high resolution atmospheric model. This meteorological forcing data is provided as snapshots of 3-D fields. We have tested it using a number of RAMS-based Forest Large Eddy Simulation (RAFLES) runs. This can then be used for parameterization of the effects of canopy structure on VOC fluxes. RAFLES represents both drag and volume restriction by the canopy over an explicit 3-D domain. We have used these features to show the effects of canopy structure on fluxes of momentum, heat, and water in heterogeneous environments at the tree-crown scale by modifying the canopy structure representing it as both homogeneous and realistically heterogeneous. We combine this with Hi-VACC's capabilities to model dispersion and chemistry of reactive VOCs to parameterize the fluxes of these reactive species with respect to canopy structure. The high resolution capabilities of Hi-VACC coupled with RAFLES allows for sensitivity analysis to determine important structural considerations in sub-grid-scale parameterization of these phenomena in larger models.

  2. Forest canopy interactions with nucleation mode particles

    NASA Astrophysics Data System (ADS)

    Pryor, S. C.; Hornsby, K. E.; Novick, K. A.

    2014-07-01

    Forests play a key role in removal of particles from the atmosphere but may also significantly contribute to formation and growth of ultrafine particles. Ultrafine particle size distributions through a deciduous forest canopy indicate substantial capture of nucleation mode particles by the foliage. Concentrations decline with depth into the canopy, such that nucleation mode number concentrations at the bottom of the canopy are an average of 16% lower than those at the top. However, growth rates of nucleation mode particles (diameters 6-30 nm) are invariant with height within the canopy, which implies that the semi-volatile gases contributing to their growth are comparatively well-mixed through the canopy. Growth rates of nucleation mode particles during a meteorological drought year (2012) were substantially lower than during a meteorologically normal year with high soil water potential (2013). This may reflect suppression of actual BVOC emissions by drought and thus reduced production of condensable products (and thus particle growth) during the drought-affected vegetation season. This hypothesis is supported by evidence that growth rates during the normal year exhibit a positive correlation with emissions of biogenic volatile organic compounds (BVOC) modeled based on observed forest composition, leaf area index, temperature and PAR, but particle growth rates during the drought-affected vegetation season are not correlated with modeled BVOC emissions. These data thus provide direct evidence for the importance of canopy capture in atmospheric particle budgets and indirect evidence that drought-stress in forests may reduce BVOC emissions and limit growth of nucleation mode particles to climate-relevant sizes.

  3. Canopy photosynthesis estimated from sapflux and stable carbon isotope ratios in northern Idaho

    NASA Astrophysics Data System (ADS)

    Marshall, J. D.; Ubierna, N.; Kavanagh, K.; Pangle, R.; Powers, E.

    2008-12-01

    Canopy-scale estimates of photosynthesis have traditionally required either scaling up from a sample of leaf measurements or scaling down from eddy flux measurements contaminated by opposing carbon dioxide fluxes. We propose an alternative based on transpiration estimates using the well established Granier sapflux sensor and scaled by modifications of standard measurements of forest structure. The resulting sapflux estimates are converted to carbon uptake measurements by first estimating canopy conductance and then using stable carbon isotope ratios to estimate the ratio of carbon to water exchange. Carbon isotope ratios were measured on leaf bulk material, phloem contents, and the highly concentrated stem CO2 pool. As found elsewhere, leaves were highly depleted and did not provide adequate estimates. We used transfer conductances estimated in other work to adjust the carbon isotope ratios prior to estimating carbon-water exchange ratios. The resulting estimates were 11 Mg C ha-1 yr-1, well within the range to be expected based on net primar production (3.6 Mg C ha-1 yr-1) in these stands. We observed seasonal variation caused by both canopy conductance and changes in \\d13C. This method of estimating canopy photosynthesis provides an important test of one of the key, and hitherto poorly constrained, components of carbon budget analyses.

  4. An overview of the 2003 Chemical Emission, Loss, Transformation and Interactions within Canopies (CELTIC) study

    NASA Astrophysics Data System (ADS)

    Guenther, A.; Geron, C.; Baker, B.; Greenberg, J.; Harley, P.; Huey, G.; Jardine, K.; Karl, T.; Matsunaga, S.; Mielke, L.; Nemitz, E.; Potosnak, M.; Rapparini, F.; Rasmussen, R.; Sparks, J.; Stroud, C.; Turnipseed, A.; Vizuete, W.; Jimenez, J.

    2003-12-01

    The Chemical Emission, Loss, Transformation and Interactions within Canopies (CELTIC) study was conducted from June 30 to July 25, 2003 at the Duke Forest FACTS-1 Site. The primary objective of CELTIC is to improve our ability to predict regional air quality (e.g., particulates and ozone) and climate through a quantitative understanding of the processes controlling the exchange of trace gases and aerosols between the atmosphere and vegetation canopies. CELTIC researchers used an unprecedented array of enclosure and whole canopy trace gas and aerosol measurement systems to compile a unique database that is being used to develop and evaluate models of biosphere-atmosphere chemical exchange. Analytical systems included twelve real-time, fast-response and continuous analyzers capable of quantifying key trace gases (>10 VOC species, NH3, PANs, NOy, CO2) and CCN and total particle numbers and chemical composition. The measurements demonstrate that our current understanding of the controlling biological, chemical and physical factors is limited and that current models are not able to accurately simulate observed biosphere-atmosphere exchange of trace gases and particles. Leaf, branch and soil enclosure systems characterized the response of isoprene, monoterpenes, sesquiterpenes, oxygenated VOC, ozone and NOx emission and uptake to changes in chemical (e.g., ozone and CO2) and physical (e.g., temperature, light, soil moisture) conditions. Major findings include observations that 1) isoprene emission increases with elevated ozone, 2) canopy scale isoprene emission increases with elevated CO2, 3) soil and leaf litter are a net sink of oxygenated VOC, and 4) sesquiterpene emissions may be higher than monoterpene emissions under certain environmental conditions. Above canopy fluxes and within canopy vertical profiling systems characterized variations in trace gases (isoprene, monoterpenes, oxygenated VOC, NOx, ozone, CO2, PANs, NH3), particles (numbers, size distribution

  5. Vertical and horizontal transport of energy and matter by coherent motions in a tall spruce canopy

    NASA Astrophysics Data System (ADS)

    Serafimovich, A.; Siebicke, L.; Foken, T.

    2009-04-01

    In a forested ecosystem low frequency coherent events contribute significantly to the budgets of momentum, heat and matter. In the frame of EGER (ExchanGE processes in mountainous Regions) project the contribution of coherent structures to the vertical and horizontal transfer of energy and matter in a tall spruce canopy was investigated. Two measuring campaigns were carried out in North-Eastern Bavaria at the Waldstein site in the Fichtelgebirge mountains. Observations of coherent structures were obtained by a vertical profile of sonic anemometers equipped with fast CO2 and H2O analyzers covering all parts of the forest up to the lower part of the roughness sub layer. In addition five small masts were set up in the trunk space of the forest and equipped with sonic anemometers, humidity and temperature sensors as well as CO2 analyzers. Combination of measurements done in vertical and horizontal directions allows us to investigate coherent structures, their temporal scales, their role in flux transport and vertical coupling between the subcanopy, canopy and air above the canopy level. To extract coherent structures from the turbulent time series, the technique based on the wavelet transform has been used. Conditional sampling analysis showed a domination of coherent structure signatures in vertical wind measurements with probable temporal scales in the order of 10 s to 30 s. The mean temporal scale of coherent structures detected in the trunk space of the forest was 30 - 40 s. The number of coherent structures detected at the slim and tall tower was found to be 40% less than the number of coherent structures detected at the heavy main tower. In contrast to the slim tower the main tower is more massive and was equipped with more instruments resulting for additional generation of turbulence. The Reynolds-averaged flux and flux contribution of coherent structures were derived using a triple decomposition for the detected and conditionally averaged time series, when

  6. 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.

  7. Analysing particulate deposition to plant canopies

    NASA Astrophysics Data System (ADS)

    Bache, D. H.

    Experimental measurements of the deposition of Lycopodium spores to a plant canopy were analysed to generate specific estimates of the relative significance of sedimentation, impaction and the effective foliage density fp. For the particular case analysed impaction appeared to be the dominating trapping mechanism and it was demonstrated that considerable aerodynamic shading was present. Using an estimate of fp. a consistant picture emerged in the behaviour of the canopy when both wet and dry and when tested against independent data on the trapping characteristics of individual elements. These conclusions differed significantly from those derived using a model in which impaction was neglected and lead to an apparent overestimate of fp.

  8. A simple and complete two-interface model for spatially developing flow in rigid and flexible canopies

    NASA Astrophysics Data System (ADS)

    Sadri, Samaneh; Luzzatto-Fegiz, Paolo

    2015-11-01

    At the front of a canopy, flow deceleration is associated with strong vertical fluxes of mass and momentum. Accurately describing this region is important in many applications, including terrestrial and aquatic vegetation, as well as large wind farms. Simple models can provide a framework to analyze these flows, thereby guiding and complementing more refined and computationally intensive tools. Jerram et al. (2003) introduced a linearised model that describes the flow field through sparse canopies, albeit at the cost of solving a PDE. A simpler approach involves vertically integrating the governing equations across the canopy, yielding scalings that relate key variables (e.g. Chen & Nepf 2013), which in turn can be used to construct empirical fits. We build a simple and complete model, by separating the flow in three horizontal layers. These comprise the canopy, the overlying boundary layer, and the outer flow, such that exchanges of mass and momentum occur at two interfaces. We parameterize turbulent exchanges by means of the entrainment hypothesis; this is a closure that has been used extensively in other problems in geophysical fluid dynamics. We neglect pressure gradients inside the canopy, but account for upstream pressure variations and retain nonlinear terms. Our two-interface model quantitatively describes the flow velocities and boundary layer heights in developing canopy flows, and successfully accounts for the effect of ambient stratification. Finally, we discuss developments accounting for the effects of flexibility in vegetation canopies.

  9. Leaf Area Index Estimation in Vineyards from Uav Hyperspectral Data, 2d Image Mosaics and 3d Canopy Surface Models

    NASA Astrophysics Data System (ADS)

    Kalisperakis, I.; Stentoumis, Ch.; Grammatikopoulos, L.; Karantzalos, K.

    2015-08-01

    The indirect estimation of leaf area index (LAI) in large spatial scales is crucial for several environmental and agricultural applications. To this end, in this paper, we compare and evaluate LAI estimation in vineyards from different UAV imaging datasets. In particular, canopy levels were estimated from i.e., (i) hyperspectral data, (ii) 2D RGB orthophotomosaics and (iii) 3D crop surface models. The computed canopy levels have been used to establish relationships with the measured LAI (ground truth) from several vines in Nemea, Greece. The overall evaluation indicated that the estimated canopy levels were correlated (r2 > 73%) with the in-situ, ground truth LAI measurements. As expected the lowest correlations were derived from the calculated greenness levels from the 2D RGB orthomosaics. The highest correlation rates were established with the hyperspectral canopy greenness and the 3D canopy surface models. For the later the accurate detection of canopy, soil and other materials in between the vine rows is required. All approaches tend to overestimate LAI in cases with sparse, weak, unhealthy plants and canopy.

  10. Regional Estimates of Drought-Induced Tree Canopy Loss across Texas

    NASA Astrophysics Data System (ADS)

    Schwantes, A.; Swenson, J. J.; González-Roglich, M.; Johnson, D. M.; Domec, J. C.; Jackson, R. B.

    2015-12-01

    The severe drought of 2011 killed millions of trees across the state of Texas. Drought-induced tree-mortality can have significant impacts to carbon cycling, regional biophysics, and community composition. We quantified canopy cover loss across the state using remotely sensed imagery from before and after the drought at multiple scales. First, we classified ~200 orthophotos (1-m spatial resolution) from the National Agriculture Imagery Program, using a supervised maximum likelihood classification. Area of canopy cover loss in these classifications was highly correlated (R2 = 0.8) with ground estimates of canopy cover loss, measured in 74 plots across 15 different sites in Texas. These 1-m orthophoto classifications were then used to calibrate and validate coarser scale (30-m) Landsat imagery to create wall-to-wall tree canopy cover loss maps across the state of Texas. We quantified percent dead and live canopy within each pixel of Landsat to create continuous maps of dead and live tree cover, using two approaches: (1) a zero-inflated beta distribution model and (2) a random forest algorithm. Widespread canopy loss occurred across all the major natural systems of Texas, with the Edwards Plateau region most affected. In this region, on average, 10% of the forested area was lost due to the 2011 drought. We also identified climatic thresholds that controlled the spatial distribution of tree canopy loss across the state. However, surprisingly, there were many local hot spots of canopy loss, suggesting that not only climatic factors could explain the spatial patterns of canopy loss, but rather other factors related to soil, landscape, management, and stand density also likely played a role. As increases in extreme droughts are predicted to occur with climate change, it will become important to define methods that can detect associated drought-induced tree mortality across large regions. These maps could then be used (1) to quantify impacts to carbon cycling and regional

  11. CO2-induced decrease of canopy stomatal conductance of mature conifer and broadleaved trees

    NASA Astrophysics Data System (ADS)

    Tor-ngern, P.; Oren, R.; Ward, E. J.; Palmroth, S.; McCarthy, H. R.; domec, J.

    2013-12-01

    Together with canopy leaf area, mean canopy stomatal conductance (GS) controls forest-atmosphere exchanges of energy and mass. Expectations for stomatal response to elevated atmospheric [CO2] (CO2E) based on seedling studies range from large decreases of conductance in foliage of broadleaved species to little or no response in conifers. These responses are not directly translatable to forest canopies, and their underlying mechanisms are ill-defined. The uncertainty of canopy-scale stomatal response to CO2E reduces confidence in modeled predictions of future forest productivity and carbon sequestration, and of partitioning of net radiation between latent and sensible heat flux. Thus, debates on the potential effects of CO2E-induced stomatal closure continue. We used a Free-Air CO2 Enrichment (FACE) experiment in a 27-year-old, 25 m tall forest, to generate a whole-canopy CO2-response and test whether canopy-scale GS response to CO2E of widely distributed, fast growing shade-intolerant species, Pinus taeda (L.) and co-occurring broadleaved species dominated by Liquidambar styraciflua (L.), was indirectly affected by slow changes such as hydraulic adjustments and canopy development, as opposed to quickly responding to CO2 concentrations in the leaf-internal air space. Our results show indirect CO2E-induced reductions of GS of 10% and 30%, respectively, and no signs of a direct stomatal response even as CO2E was pushed to 685 μmol mol-1 (~1.8 of ambient). Modeling the effect of CO2E on the water, energy and carbon cycles of forests must consider slow-response indirect mechanisms producing large variation in the reduction of GS, such as the previously observed inconsistent CO2E effect on canopy leaf area and plant hydraulics. Moreover, the new generation of CO2E studies in forests must allow indirect effects caused by, e.g., hydraulic adjustments and canopy development, to play out. Such acclimation will be particularly prolonged in slowly developing ecosystems, such

  12. Making direct use of canopy profiles in vegetation - atmosphere coupling

    NASA Astrophysics Data System (ADS)

    Ryder, James; Polcher, Jan; Peylin, Philippe; Ottlé, Catherine; Chen, Yiying; van Gorsel, Eva; Haverd, Vanessa; McGrath, Matthew; Naudts, Kim; Otto, Juliane; Valade, Aude; Luyssaert, Sebastiaan

    2015-04-01

    Most coupled land-surface regional models use the 'big-leaf' approach for simulating the sensible and latent heat fluxes of different vegetation types. However, there has been a progression in the types of questions being asked of these models, such as the consequences of land-use change or the behaviour of BVOCs and aerosol. In addition, recent years has seen growth in the availability of in-canopy datasets across a broaded range of species, with which to calibrate these simulations. Hence, there is now an argument for transferring some of the techniques and processes previously used in local, site-based land surface models to the land surface components of models which operate on a regional or even global scale. We describe here the development and evaluation of a vertical canopy energy budget model (Ryder, J et al., 2014) that can be coupled to an atmospheric model such as LMDz. Significantly, the model preserves the implicit coupling of the land-surface to atmosphere interface, which means that run-time efficiences are preserved. This is acheived by means of an interface based on the approach of Polcher et al. (1998) and Best et al. (2004), but newly developed for a canopy column. The model makes use of techniques from site-based models, such as the calculation of vertical turbulence statistics using a second-order closure model (Massman & Weil, 1999), and the distribution of long-wave and short-wave radiation over the profile, the latter using an innovate multilayer albedo scheme (McGrath et al., in prep.). Complete profiles of atmospheric temperature and specific humidity are now calculated, in order to simulate sensible and latent heat fluxes, as well as the leaf temperature at each level in the model. The model is shown to perform stably, and reproduces well flux measurements at an initial test site, across a time period of several days, or over the course of a year. Further applications of the model might be to simulate mixed canopies, the light

  13. 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.

  14. Spatial and diurnal below canopy evaporation in a desert vineyard: Measurements and modeling

    NASA Astrophysics Data System (ADS)

    Kool, D.; Ben-Gal, A.; Agam, N.; Šimůnek, J.; Heitman, J. L.; Sauer, T. J.; Lazarovitch, N.

    2014-08-01

    Evaporation from the soil surface (E) can be a significant source of water loss in arid areas. In sparsely vegetated systems, E is expected to be a function of soil, climate, irrigation regime, precipitation patterns, and plant canopy development and will therefore change dynamically at both daily and seasonal time scales. The objectives of this research were to quantify E in an isolated, drip-irrigated vineyard in an arid environment and to simulate below canopy E using the HYDRUS (2-D/3-D) model. Specific focus was on variations of E both temporally and spatially across the inter-row. Continuous above canopy measurements, made in a commercial vineyard, included evapotranspiration, solar radiation, air temperature and humidity, and wind speed and direction. Short-term intensive measurements below the canopy included actual and potential E and solar radiation along transects between adjacent vine-rows. Potential and actual E below the canopy were highly variable, both diurnally and with distance from the vine-row, as a result of shading and distinct wetted areas typical to drip irrigation. While the magnitude of actual E was mostly determined by soil water content, diurnal patterns depended strongly on position relative to the vine-row due to variable shading patterns. HYDRUS (2-D/3-D) successfully simulated the magnitude, diurnal patterns, and spatial distribution of E, including expected deviations as a result of variability in soil saturated hydraulic conductivity.

  15. Increases in atmospheric CO2 have little influence on transpiration of a temperate forest canopy.

    PubMed

    Tor-ngern, Pantana; Oren, Ram; Ward, Eric J; Palmroth, Sari; McCarthy, Heather R; Domec, Jean-Christophe

    2015-01-01

    Models of forest energy, water and carbon cycles assume decreased stomatal conductance with elevated atmospheric CO2 concentration ([CO2]) based on leaf-scale measurements, a response not directly translatable to canopies. Where canopy-atmosphere are well-coupled, [CO2 ]-induced structural changes, such as increasing leaf-area index (LD), may cause, or compensate for, reduced mean canopy stomatal conductance (GS), keeping transpiration (EC) and, hence, runoff unaltered. We investigated GS responses to increasing [CO2] of conifer and broadleaved trees in a temperate forest subjected to 17-yr free-air CO2 enrichment (FACE; + 200 μmol mol(-1)). During the final phase of the experiment, we employed step changes of [CO2] in four elevated-[CO2 ] plots, separating direct response to changing [CO2] in the leaf-internal air-space from indirect effects of slow changes via leaf hydraulic adjustments and canopy development. Short-term manipulations caused no direct response up to 1.8 × ambient [CO2], suggesting that the observed long-term 21% reduction of GS was an indirect effect of decreased leaf hydraulic conductance and increased leaf shading. Thus, EC was unaffected by [CO2] because 19% higher canopy LD nullified the effect of leaf hydraulic acclimation on GS . We advocate long-term experiments of duration sufficient for slow responses to manifest, and modifying models predicting forest water, energy and carbon cycles accordingly.

  16. Wave propagation in a solar quiet region and the influence of the magnetic canopy

    NASA Astrophysics Data System (ADS)

    Kontogiannis, I.; Tsiropoula, G.; Tziotziou, K.

    2016-01-01

    Aims: We seek indications or evidence of transmission/conversion of magnetoacoustic waves at the magnetic canopy, as a result of its impact on the properties of the wave field of the photosphere and chromosphere. Methods: We use cross-wavelet analysis to measure phase differences between intensity and Doppler signal oscillations in the Hα, Ca ii h, and G-band. We use the height of the magnetic canopy to create appropriate masks to separate internetwork (IN) and magnetic canopy regions. We study wave propagation and differences between these two regions. Results: The magnetic canopy affects wave propagation by lowering the phase differences of progressive waves and allowing the propagation of waves with frequencies lower than the acoustic cut-off. We also find indications in the Doppler signals of Hα of a response to the acoustic waves at the IN, observed in the Ca ii h line. This response is affected by the presence of the magnetic canopy. Conclusions: Phase difference analysis indicates the existence of a complicated wave field in the quiet Sun, which is composed of a mixture of progressive and standing waves. There are clear imprints of mode conversion and transmission due to the interaction between the p-modes and small-scale magnetic fields of the network and internetwork.

  17. Mixed-Grass Prairie Canopy Structure and Spectral Reflectance Vary with Topographic Position

    NASA Astrophysics Data System (ADS)

    Phillips, Rebecca L.; Ngugi, Moffatt K.; Hendrickson, John; Smith, Aaron; West, Mark

    2012-11-01

    Managers of the nearly 0.5 million ha of public lands in North and South Dakota, USA rely heavily on manual measurements of canopy height in autumn to ensure conservation of grassland structure for wildlife and forage for livestock. However, more comprehensive assessment of vegetation structure could be achieved for mixed-grass prairie by integrating field survey, topographic position (summit, mid and toeslope) and spectral reflectance data. Thus, we examined the variation of mixed-grass prairie structural attributes (canopy leaf area, standing crop mass, canopy height, nitrogen, and water content) and spectral vegetation indices (VIs) with variation in topographic position at the Grand River National Grassland (GRNG), South Dakota. We conducted the study on a 36,000-ha herbaceous area within the GRNG, where randomly selected plots (1 km2 in size) were geolocated and included summit, mid and toeslope positions. We tested for effects of topographic position on measured vegetation attributes and VIs calculated from Landsat TM and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data collected in July 2010. Leaf area, standing crop mass, canopy height, nitrogen, and water content were lower at summits than at toeslopes. The simple ratio of Landsat Band 7/Band 1 (SR71) was the VI most highly correlated with canopy standing crop and height at plot and landscape scales. Results suggest field and remote sensing-based grassland assessment techniques could more comprehensively target low structure areas at minimal expense by layering modeled imagery over a landscape stratified into topographic position groups.

  18. Progressive forest canopy water loss during the 2012–2015 California drought

    PubMed Central

    Asner, Gregory P.; Brodrick, Philip G.; Anderson, Christopher B.; Vaughn, Nicholas; Knapp, David E.; Martin, Roberta E.

    2016-01-01

    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. PMID:26712020

  19. 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.

  20. 22. DRAWING #8 OF 15, FRONT AND REAR ELEVATIONS, CANOPY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. DRAWING #8 OF 15, FRONT AND REAR ELEVATIONS, CANOPY ROOF PLAN AND CANOPY DETAIL, AND ELEVATIONS OF NEW TOILETS - U. S. Post Office, Custom House & Courthouse, 401 Center Street, Fernandina Beach, Nassau County, FL

  1. Wireless sensor networks for canopy temperature sensing and irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For researchers, canopy temperature measurements have proven useful in characterizing crop water stress and developing protocols for irrigation management. Today, there is heightened interest in using remote canopy temperature measurements for real-time irrigation scheduling. However, without the us...

  2. THE EVOLUTION OF DARK CANOPIES AROUND ACTIVE REGIONS

    SciTech Connect

    Wang, Y.-M.; Robbrecht, E.; Muglach, K. E-mail: eva.robbrecht@oma.be

    2011-05-20

    As observed in spectral lines originating from the chromosphere, transition region, and low corona, active regions are surrounded by an extensive 'circumfacular' area which is darker than the quiet Sun. We examine the properties of these dark moat- or canopy-like areas using Fe IX 17.1 nm images and line-of-sight magnetograms from the Solar Dynamics Observatory. The 17.1 nm canopies consist of fibrils (horizontal fields containing extreme-ultraviolet-absorbing chromospheric material) clumped into featherlike structures. The dark fibrils initially form a quasiradial or vortical pattern as the low-lying field lines fanning out from the emerging active region connect to surrounding network and intranetwork elements of opposite polarity. The area occupied by the 17.1 nm fibrils expands as supergranular convection causes the active-region flux to spread into the background medium; the outer boundary of the dark canopy stabilizes where the diffusing flux encounters a unipolar region of opposite sign. The dark fibrils tend to accumulate in regions of weak longitudinal field and to become rooted in mixed-polarity flux. To explain the latter observation, we note that the low-lying fibrils are more likely to interact with small loops associated with weak, opposite-polarity flux elements in close proximity, than with high loops anchored inside strong unipolar network flux. As a result, the 17.1 nm fibrils gradually become concentrated around the large-scale polarity inversion lines (PILs), where most of the mixed-polarity flux is located. Systematic flux cancellation, assisted by rotational shearing, removes the field component transverse to the PIL and causes the fibrils to coalesce into long PIL-aligned filaments.

  3. TLS monitoring of snowpack distribution in a mountain forested areas: Analysis of canopy disturbance on snow evolution.

    NASA Astrophysics Data System (ADS)

    Revuelto, Jesús; López-Moreno, Juan Ignacio; Azorin-Molina, Cesar; Alonso, Esteban; San Miguel, Alba

    2016-04-01

    Forested mountain areas at high elevations show important interaction with snowpack distribution and its evolution in time, and thus in many cases are the limit of the cryosphere in mountain zones. Such interactions have significant consequences in the hydrologic response of mountain rivers. Thereby observing the evolution of snowpack in forested areas has a big importance form a basic science perspective and also for water management. This work presents a detailed comparison of small scale effect of forest characteristics on snowpack distribution in Central Pyrenees, before and after a strong modification of canopies features. The snowpack distribution has been obtained using a novel remote sensing technology (Terrestrial Laser Scanner, TLS), with high spatial resolution (0.25m) over a 1000m2 study area for 27 survey dates along three snow seasons. Between the second and the third snow season a strong canopy pruning was performed in the study site, and thereby the snowpack evolution with both canopy configurations was compared. A Principal Component Analysis has been applied to analyze the snowpack distributions observed during the study period. Results obtained have shown that despite large differences in Canopy radius (1.2 m) and Canopy height (2.5m), not a different snowpack evolution was observed. For both Canopy configurations the variable with higher importance on snowpack distribution is the snow depth amount. The change in forest structure has important implications in the decrease of Canopy areas and the increase of Open areas (proportionally to Canopy change), but not a different interaction with forest structure was observed. The canopy pruning realized in the study site is typically accomplished for fire risk reduction and this shows the consequences that such action has in snowpack distribution and that hereby these may have in water management possibly delaying peak runoff.

  4. Ground-Based Lidar Measurements of Forest Canopy Structure as Predictors of Net Primary Production Across Successional Time

    NASA Astrophysics Data System (ADS)

    Scheuermann, C. M.; Gough, C. M.; Nave, L. E.

    2015-12-01

    Forest canopy structure is a key predictor of gas exchange processes that control carbon (C) uptake, including the allocation of photosynthetically fixed C to new plant biomass growth, or net primary production (NPP). Prior work suggests forest canopy structural complexity (CSC), the arrangement of leaves within a volume of canopy, changes as forests develop and is a strong predictor of NPP. However, the expressions of CSC that best predict NPP over decadal to century timescales is unknown. Our objectives were to use multiple remote sensing observations to characterize forest canopy structure in increasing dimensional complexity over a forest age gradient, and to identify which expressions of physical structure best served as proxies of NPP. The study at the University of Michigan Biological Station in Pellston, MI, USA uses two parallel forest chronosequences with different harvesting and fire disturbance histories and includes three old-growth ecosystems varying in canopy composition. We have derived several expressions of 2-D and 3-D forest canopy structure from hemispherical images, a ground-based portable canopy lidar (PCL), and a 3-D terrestrial lidar scanner (TLS), and are relating these structural metrics with NPP and light and nitrogen allocation within the canopy. Preliminary analysis shows that old-growth stands converged on a common mean CSC, but with substantially higher within-stand variation in complexity as deciduous tree species increased in forest canopy dominance. Forest stands that were more intensely disturbed were slower to recover leaf area index (LAI) as they regrew, but 2-D measures of CSC increased similarly as forests aged, regardless of disturbance history. Ongoing work will relate long-term trends in forest CSC with NPP and resource allocation to determine which forest structure remote sensing products are most useful for modeling and scaling C cycling processes through different stages of forest development.

  5. Simulation of within-canopy radiation exchange

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Radiation exchange at the surface plays a critical role in the surface energy balance, plant microclimate, and plant growth. The ability to simulate the surface energy balance and the microclimate within the plant canopy is contingent upon simulation of the surface radiation exchange. A validation a...

  6. Towards a High Temporal Frequency Grass Canopy Thermal IR Model for Background Signatures

    NASA Technical Reports Server (NTRS)

    Ballard, Jerrell R., Jr.; Smith, James A.; Koenig, George G.

    2004-01-01

    In this paper, we present our first results towards understanding high temporal frequency thermal infrared response from a dense plant canopy and compare the application of our model, driven both by slowly varying, time-averaged meteorological conditions and by high frequency measurements of local and within canopy profiles of relative humidity and wind speed, to high frequency thermal infrared observations. Previously, we have employed three-dimensional ray tracing to compute the intercepted and scattered radiation fluxes and for final scene rendering. For the turbulent fluxes, we employed simple resistance models for latent and sensible heat with one-dimensional profiles of relative humidity and wind speed. Our modeling approach has proven successful in capturing the directional and diurnal variation in background thermal infrared signatures. We hypothesize that at these scales, where the model is typically driven by time-averaged, local meteorological conditions, the primary source of thermal variance arises from the spatial distribution of sunlit and shaded foliage elements within the canopy and the associated radiative interactions. In recent experiments, we have begun to focus on the high temporal frequency response of plant canopies in the thermal infrared at 1 second to 5 minute intervals. At these scales, we hypothesize turbulent mixing plays a more dominant role. Our results indicate that in the high frequency domain, the vertical profile of temperature change is tightly coupled to the within canopy wind speed In the results reported here, the canopy cools from the top down with increased wind velocities and heats from the bottom up at low wind velocities. .

  7. Canopy structure of sagebrush ecosystems leading to differences in carbon and water fluxes

    NASA Astrophysics Data System (ADS)

    Reed, D. E.; Ewers, B. E.; Peckham, S. D.; Pendall, E. G.; Kelly, R. D.

    2013-12-01

    The sagebrush steppe ecosystem covers nearly 15% of Western North America, and its productivity is sensitive to warming and increasingly variable precipitation. Previous work has shown that interannual variability of precipitation is the largest factor in carbon and water cycling in these semi-arid ecosystems and that the relationship of traditional drivers of fluxes (VPD, net radiation, soil temperature) to carbon and water fluxes as well as ecosystem water use efficiency does not change along an elevation gradient. We seek to expand on that work by using multiple site-years from eddy covariance data near the upper (2469m) and lower (2069m) elevation range of sagebrush to answer the question 'How does canopy structure and canopy leaf area index combine to control the ecosystem carbon and water fluxes from rocky mountain sagebrush ecosystems'. We are answering this question by quantifying ecosystem scale carbon and water using eddy covariance measurements and a standard suite of atmospheric, soil and vegetation monitoring instruments. This data will be used with the Terrestrial Regional Ecosystem Exchange Simulator (TREES) Bayesian framework model that utilizes a coupled plant hydraulic and carbon uptake. For this work we use the TREES model to simulate canopy structure and leaf area based on seven years of eddy covariance data from the two different locations. This canopy information will be compared with canopy structure ground measurements within the eddy covariance footprint, and then we will compare the relationship between canopy structure and ecosystem fluxes. During well watered growing season time periods, the high elevation site has average water flux of 1.06 mmol m-2 s-1 and carbon flux of 1.54 μmol m-2 s-1 of uptake. Average water and carbon fluxes at the lower elevation site were 0.84 mmol m-2 s-1 and 1.09 μmol m-2 s-1 of uptake respectively. This is a reduction of 20% for water flux and 30% and carbon flux down the elevation gradient. With the

  8. Heat and moisture flux modeling of the FIFE grassland canopy aided by satellite derived canopy variables

    NASA Technical Reports Server (NTRS)

    Smith, Eric A.; Crosson, William L.; Cooper, Harry J.; Weng, Heng-Yi

    1990-01-01

    Satellite data corresponding to radiance variables are used to derive three canopy properties which describe slowly modulating boundary conditions of the interface between the biosphere and the atmosphere. The canopy properties are key factors in the regulation of heat and moisture transfer and are found to be radiance patterns within a homogeneous ecosystem. The physical modeling technique is enhanced by the satellite data, and the surface fluxes are represented more accurately in the resulting biosphere-interface model.

  9. Scales

    MedlinePlus

    Scales are a visible peeling or flaking of outer skin layers. These layers are called the stratum ... Scales may be caused by dry skin, certain inflammatory skin conditions, or infections. Eczema , ringworm , and psoriasis ...

  10. Evaluation of improved land use and canopy representation in ...

    EPA Pesticide Factsheets

    Biogenic volatile organic compounds (BVOC) participate in reactions that can lead to secondarily formed ozone and particulate matter (PM) impacting air quality and climate. BVOC emissions are important inputs to chemical transport models applied on local to global scales but considerable uncertainty remains in the representation of canopy parameterizations and emission algorithms from different vegetation species. The Biogenic Emission Inventory System (BEIS) has been used to support both scientific and regulatory model assessments for ozone and PM. Here we describe a new version of BEIS which includes updated input vegetation data and canopy model formulation for estimating leaf temperature and vegetation data on estimated BVOC. The Biogenic Emission Landuse Database (BELD) was revised to incorporate land use data from the Moderate Resolution Imaging Spectroradiometer (MODIS) land product and 2006 National Land Cover Database (NLCD) land coverage. Vegetation species data are based on the US Forest Service (USFS) Forest Inventory and Analysis (FIA) version 5.1 for 2002–2013 and US Department of Agriculture (USDA) 2007 census of agriculture data. This update results in generally higher BVOC emissions throughout California compared with the previous version of BEIS. Baseline and updated BVOC emission estimates are used in Community Multiscale Air Quality (CMAQ) Model simulations with 4 km grid resolution and evaluated with measurements of isoprene and monoterp

  11. Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

    NASA Astrophysics Data System (ADS)

    Wehr, Richard; Commane, Róisín; Munger, J. William; McManus, J. Barry; Nelson, David D.; Zahniser, Mark S.; Saleska, Scott R.; Wofsy, Steven C.

    2017-01-01

    Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface-atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem-atmosphere exchange of OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further

  12. Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

    DOE PAGES

    Wehr, Richard; Commane, Róisín; Munger, J. William; ...

    2017-01-26

    Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange ofmore » OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is

  13. Analytical Modelling of Canopy Interception Loss from a Juvenile Lodgepole Pine (Pinus contorta var. latifolia) Stand

    NASA Astrophysics Data System (ADS)

    Carlyle-Moses, D. E.; Lishman, C. E.

    2015-12-01

    In the central interior of British Columbia (BC), Canada, the mountain pine beetle (Dendroctonus ponderosae Hopkins) (MPB) has severely affected the majority of pine species in the region, especially lodgepole pine (Pinus contorta Douglas ex Louden var. latifolia Engelm. ex S. Watson). The loss of mature lodgepole pine stands, including those lost to salvage logging, has resulted in an increase in the number of juvenile pine stands in the interior of BC through planting and natural regrowth. With this change from mature forests to juvenile forests at such a large spatial scale, the water balance of impacted areas may be altered, although the magnitude of such change is uncertain. Previous studies of rainfall partitioning by lodgepole pine and lodgepole pine dominated canopies have focused on mature stands. Thus, rainfall, throughfall and stemflow were measured and canopy interception loss was derived during the growing season of 2010 in a juvenile lodgepole pine dominated stand located approximately 60 km NNW of Kamloops, BC at 51°12'49" N 120°23'43" W, 1290 m above mean sea level. Scaling up from measurements for nine trees, throughfall, stemflow and canopy interception loss accounted for 87.7, 1.8 and 10.5 percent of the 252.9 mm of rain that fell over 38 events during the study period, respectively. The reformulated versions of the Gash and Liu analytical interception loss models estimated cumulative canopy interception loss at 24.7 and 24.6 mm, respectively, compared with the observed 26.5 mm; an underestimate of 1.8 and 1.9 mm or 6.8 and 7.2% of the observed value, respectively. Our results suggest that canopy interception loss is reduced in juvenile stands compared to their mature counterparts and that this reduction is due to the decreased storage capacity offered by these younger canopies. Evaporation during rainfall from juvenile canopies is still appreciable and may be a consequence of the increased proportion of the canopy exposed to wind during events.

  14. Photosynthesis and resource distribution through plant canopies.

    PubMed

    Niinemets, Ulo

    2007-09-01

    Plant canopies are characterized by dramatic gradients of light between canopy top and bottom, and interactions between light, temperature and water vapour deficits. This review summarizes current knowledge of potentials and limitations of acclimation of foliage photosynthetic capacity (A(max)) and light-harvesting efficiency to complex environmental gradients within the canopies. Acclimation of A(max) to high light availability involves accumulation of rate-limiting photosynthetic proteins per unit leaf area as the result of increases in leaf thickness in broad-leaved species and volume: total area ratio and mesophyll thickness in species with complex geometry of leaf cross-section. Enhancement of light-harvesting efficiency in low light occurs through increased chlorophyll production per unit dry mass, greater leaf area per unit dry mass investment in leaves and shoot architectural modifications that improve leaf exposure and reduce within-shoot shading. All these acclimation responses vary among species, resulting in species-specific use efficiencies of low and high light. In fast-growing canopies and in evergreen species, where foliage developed and acclimated to a certain light environment becomes shaded by newly developing foliage, leaf senescence, age-dependent changes in cell wall characteristics and limited foliage re-acclimation capacity can constrain adjustment of older leaves to modified light availabilities. The review further demonstrates that leaves in different canopy positions respond differently to dynamic fluctuations in light availability and to multiple environmental stresses. Foliage acclimated to high irradiance respond more plastically to rapid changes in leaf light environment, and is more resistant to co-occurring heat and water stress. However, in higher light, co-occurring stresses can more strongly curb the efficiency of foliage photosynthetic machinery through reductions in internal diffusion conductance to CO(2). This review

  15. Biophysical information in asymmetric and symmetric diurnal bidirectional canopy reflectance

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern C.; Caldwell, William F.; Pettigrew, Rita E.; Ustin, Susan L.; Martens, Scott N.; Rousseau, Robert A.; Berger, Kevin M.; Ganapol, B. D.; Kasischke, Eric S.; Clark, Jenny A.

    1991-01-01

    The authors present a theory for partitioning the information content in diurnal bidirectional reflectance measurements in order to detect differences potentially related to biophysical variables. The theory, which divides the canopy reflectance into asymmetric and symmetric functions of solar azimuth angle, attributes asymmetric variation to diurnal changes in the canopy biphysical properties. The symmetric function is attributed to the effects of sunlight interacting with a hypothetical average canopy which would display the average diurnal properties of the actual canopy. The authors analyzed radiometer data collected diurnally in the Thematic Mapper wavelength bands from two walnut canopies that received differing irrigation treatments. The reflectance of the canopies varied with sun and view angles and across seven bands in the visible, near-infrared, and middle infrared wavelength regions. Although one of the canopies was permanently water stressed and the other was stressed in mid-afternoon each day, no water stress signature was unambiguously evident in the reflectance data.

  16. Airborne Imaging Spectroscopy of Forest Canopy Chemistry in the Andes-Amazon Corridor

    NASA Astrophysics Data System (ADS)

    Martin, R.; Anderson, C.; Knapp, D. E.; Asner, G. P.

    2013-12-01

    The Andes-Amazon corridor is one of the most biologically diverse regions on Earth. Elevation gradients provide opportunities to explore the underlying sources and environmental controls on functional diversity of the forest canopy, however plot-based studies have proven highly variable. We used airborne imaging spectroscopy from the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS) to quantify changes canopy functional traits in a series of eleven 25-ha landscapes distributed along a 3300 m elevation gradient from lowland Amazonia to treeline in the Peruvian Andes. Each landscape encompassed a 1 ha field plot in which all trees reaching the canopy were climbed and leaves were sampled for 20 chemical traits. We used partial least squares regression to relate plot-level chemical values with airborne spectroscopy from the 1 ha area. Sixteen chemical traits produced predictable relationships with the spectra and were used to generate maps of the 25 ha landscape. Ten chemical traits were significantly related to elevation at the 25 ha scale. These ten traits displayed 35% greater accuracy (R2) and precision (rmse) when evaluated at the 25 ha scale compared to values derived from tree climbing alone. The results indicate that high-fidelity imaging spectroscopy can be used as surrogate for laborious tree climbing and chemical assays to understand chemical diversity in Amazonian forests. Understanding how these chemicals vary among forest communities throughout the Andes-Amazon corridor will facilitate mapping of functional diversity and the response of canopies to climate change.

  17. Two-color, Polarimetric Laser Altimeter Measurements of Forest Canopy Structure and Composition

    NASA Astrophysics Data System (ADS)

    Dabney, P.; Yu, A. W.; Harding, D. J.; Valett, S. R.; Hicks, E.; Shuman, C. A.; Vasilyev, A. A.

    2010-12-01

    Over the past decade lidar remote sensing has proven to be a highly effective method for characterization of forest canopy structure and estimation of biomass stocks. However, traditional measurements only provide information on the vertical distribution of surfaces without ability to differentiate surface types. Also, an unresolved aspect of traditional measurements is the contribution of within-canopy multiple scattering to the lidar profiles of canopy structure. Slope Imaging Multi-polarization Photon-counting Lidar (SIMPL) data was acquired in July and August, 2010 for three sites with well-characterized forest structure in order to address these issues. SIMPL is an airborne, four-beam laser altimeter developed through the NASA Earth Science Technology Office Instrument Incubator Program. It acquires single-photon laser ranging data at 532 and 1064 nm, recording range-resolved measurements of reflected energy parallel and perpendicular to the transmit pulse polarization plane. Prior work with a non-ranging, multi-wavelength laser polarimetry demonstrated differentiation of tree species types based on depolarization differences related to surface and volume multiple scattering at the leaf scale. By adding the ranging component, SIMPL provides a means to investigate the vertical and horizontal distribution of optical scattering properties to better understand the interaction of pulsed laser energy with the foliage, stem and branch components of forest canopies. Data were acquired for the deciduous forest cover at the Smithsonian Environmental Research Center in Maryland and mixed deciduous and pine cover in the New Jersey Pine Barrens, two sites being used by the ICESat-2 project to assess micropulse, single-photon measurements of forest canopies. A third site, in the Huron National Forest in Michigan, has had diverse forest silviculture management practices applied to pine stands. The contrasts in forest stands between these sites will be used to illustrate

  18. A model of plant canopy polarization

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.

    1980-01-01

    A model for the amount of linearly polarized light reflected by the shiny leaves of grain crops is based on the morphological and phenological characteristics of the plant canopy and upon the Fresnel equations which describe the light reflection process at the smooth boundary separating two dielectrics. The theory used demonstrates that, potentially, measurements of the linearly polarized light from a crop canopy may be used as an additional feature to discriminate between crops such as wheat and barley, two crops which are so spectrally similar that they are misclassified with unacceptable frequency. Examination of the model suggests that, potentially, satellite polarization measurements may be used to monitor crop development stage, leaf water content, leaf area index, hail damage, and certain plant diseases. The information content of these measurements is needed to evaluate the proposed polarization sensor for the satellite-borne multispectral resource sampler.

  19. C-band backscattering from corn canopies

    NASA Technical Reports Server (NTRS)

    Daughtry, C. S. T.; Ranson, K. J.; Biehl, L. L.

    1991-01-01

    A frequency-modulatad continuous-wave C-band (4.8 GHz) scatterometer was mounted on an aerial lift truck, and backscatter coefficients of corn (Zea mays L.) were acquired as functions of polarizations, view angles, and row directions. As phytomass and green-leaf area index increased, the backscatter also increased. Near anthesis, when the canopies were fully developed, the major scattering elements were located in the upper 1 m of the 2.8 m tall canopy and little backscatter was measured below that level for view angles of 30 deg or greater. C-band backscatter data could provide information to monitor tillage operations at small view zenith angles and vegetation at large view zenith angles.

  20. Diurnal variations of vegetation canopy structure

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.; Kirchner, J. A.

    1983-01-01

    The significance and magnitude of diurnal variations of vegetation canopy structure are reviewed. Diurnal leaf inclination-azimuth angle distributions of a soybean and cotton canopy were documented using a simple measurement technique. The precision of the measurements was on the order of + or -5 deg for the inclination and + or -14 deg for the azimuth. The experimental results and a review of the literature showed that this distribution can vary significantly on a diurnal basis due to vegetation type, heliotropic leaf movement, environmental conditions, and vegetation stress. The study also showed that it is erroneous to treat two separate distributions of azimuth and inclination angles rather than one three-dimensional distribution of leaf orientation. The latter distribution needs to be routinely collected in studies which document variations of diurnal spectral reflectance with changes in solar zenith angle.

  1. Electromagnetic wave extinction within a forested canopy

    NASA Technical Reports Server (NTRS)

    Karam, M. A.; Fung, A. K.

    1989-01-01

    A forested canopy is modeled by a collection of randomly oriented finite-length cylinders shaded by randomly oriented and distributed disk- or needle-shaped leaves. For a plane wave exciting the forested canopy, the extinction coefficient is formulated in terms of the extinction cross sections (ECSs) in the local frame of each forest component and the Eulerian angles of orientation (used to describe the orientation of each component). The ECSs in the local frame for the finite-length cylinders used to model the branches are obtained by using the forward-scattering theorem. ECSs in the local frame for the disk- and needle-shaped leaves are obtained by the summation of the absorption and scattering cross-sections. The behavior of the extinction coefficients with the incidence angle is investigated numerically for both deciduous and coniferous forest. The dependencies of the extinction coefficients on the orientation of the leaves are illustrated numerically.

  2. AVIRIS data quality for coniferous canopy chemistry

    NASA Technical Reports Server (NTRS)

    Swanberg, Nancy A.

    1988-01-01

    An assessment of AVIRIS data quality for studying coniferous canopy chemistry was made. Seven flightlines of AVIRIS data were acquired over a transect of coniferous forest sites in central Oregon. Both geometric and radiometric properties of the data were examined including: pixel size, swath width, spectral position and signal-to-noise ratio. A flat-field correction was applied to AVIRIS data from a coniferous forest site. Future work with this data set will exclude data from spectrometers C and D due to low signal-to-noise ratios. Data from spectrometers A and B will be used to examine the relationship between the canopy chemical composition of the forest sites and AVIRIS spectral response.

  3. Design of a Parachute Canopy Instrumentation Platform

    NASA Technical Reports Server (NTRS)

    Alshahin, Wahab M.; Daum, Jared S.; Holley, James J.; Litteken, Douglas A.; Vandewalle, Michael T.

    2015-01-01

    This paper discusses the current technology available to design and develop a reliable and compact instrumentation platform for parachute system data collection and command actuation. Wireless communication with a parachute canopy will be an advancement to the state of the art of parachute design, development, and testing. Embedded instrumentation of the parachute canopy will provide reefing line tension, skirt position data, parachute health monitoring, and other telemetry, further validating computer models and giving engineering insight into parachute dynamics for both Earth and Mars entry that is currently unavailable. This will allow for more robust designs which are more optimally designed in terms of structural loading, less susceptible to adverse dynamics, and may eventually pave the way to currently unattainable advanced concepts of operations. The development of this technology has dual use potential for a variety of other applications including inflatable habitats, aerodynamic decelerators, heat shields, and other high stress environments.

  4. Modeling of forest canopy BRDF using DIRSIG

    NASA Astrophysics Data System (ADS)

    Rengarajan, Rajagopalan; Schott, John R.

    2016-05-01

    The characterization and temporal analysis of multispectral and hyperspectral data to extract the biophysical information of the Earth's surface can be significantly improved by understanding its aniosotropic reflectance properties, which are best described by a Bi-directional Reflectance Distribution Function (BRDF). The advancements in the field of remote sensing techniques and instrumentation have made hyperspectral BRDF measurements in the field possible using sophisticated goniometers. However, natural surfaces such as forest canopies impose limitations on both the data collection techniques, as well as, the range of illumination angles that can be collected from the field. These limitations can be mitigated by measuring BRDF in a virtual environment. This paper presents an approach to model the spectral BRDF of a forest canopy using the Digital Image and Remote Sensing Image Generation (DIRSIG) model. A synthetic forest canopy scene is constructed by modeling the 3D geometries of different tree species using OnyxTree software. The field collected spectra from the Harvard forest is used to represent the optical properties of the tree elements. The canopy radiative transfer is estimated using the DIRSIG model for specific view and illumination angles to generate BRDF measurements. A full hemispherical BRDF is generated by fitting the measured BRDF to a semi-empirical BRDF model. The results from fitting the model to the measurement indicates a root mean square error of less than 5% (2 reflectance units) relative to the forest's reflectance in the VIS-NIR-SWIR region. The process can be easily extended to generate a spectral BRDF library for various biomes.

  5. Radiative Transfer in Submerged Macrophyte Canopies

    DTIC Science & Technology

    2001-09-30

    the canopy in Monterey Bay , California and Lee Stocking Island, Bahamas. Years 3 and 4 continued to evaluate inherent optical properties of individual...both the clear waters of Lee Stocking Island, Bahamas and the much more turbid environment of Elkhorn Slough, in Monterey Bay (Fig. 1A, C). Since...data sets consisting of water column optical property observations of nearshore waters in Monterey Bay were transferred to J. Smart (APL, Johns

  6. A two-layer canopy model with thermal inertia for an improved snowpack energy balance below needleleaf forest (model SNOWPACK, version 3.2.1, revision 741)

    NASA Astrophysics Data System (ADS)

    Gouttevin, I.; Lehning, M.; Jonas, T.; Gustafsson, D.; Molder, M.

    2015-08-01

    A new, two-layer canopy module with thermal inertia as part of the detailed snow model SNOWPACK (version 3.2.1) is presented and evaluated. As a by-product of these new developments, an exhaustive description of the canopy module of the SNOWPACK model is provided, thereby filling a gap in the existing literature. In its current form, the two-layer canopy module is suited for evergreen needleleaf forest, with or without snow cover. It is designed to reproduce the difference in thermal response between leafy and woody canopy elements, and their impact on the underlying snowpack or ground surface energy balance. Given the number of processes resolved, the SNOWPACK model with its enhanced canopy module constitutes a sophisticated physics-based modeling chain of the continuum going from atmosphere to soil through the canopy and snow. Comparisons of modeled sub-canopy thermal radiation to stand-scale observations at an Alpine site (Alptal, Switzerland) demonstrate improvements induced by the new canopy module. Both thermal heat mass and the two-layer canopy formulation contribute to reduce the daily amplitude of the modeled canopy temperature signal, in agreement with observations. Particularly striking is the attenuation of the nighttime drop in canopy temperature, which was a key model bias. We specifically show that a single-layered canopy model is unable to produce this limited temperature drop correctly. The impact of the new parameterizations on the modeled dynamics of the sub-canopy snowpack is analyzed. The new canopy module yields consistent results but the frequent occurrence of mixed-precipitation events at Alptal prevents a conclusive assessment of model performance against snow data. The new model is also successfully tested without specific tuning against measured tree temperature and biomass heat-storage fluxes at the boreal site of Norunda (Sweden). This provides an independent assessment of its physical consistency and stresses the robustness and

  7. A virtual canopy generator (V-CaGe) for modelling complex heterogeneous forest canopies at high resolution

    NASA Astrophysics Data System (ADS)

    Bohrer, Gil; Wolosin, Michael; Brady, Rachael; Avissar, Roni

    2007-07-01

    The structure of tree canopies affects turbulence in the atmospheric boundary layer, and light attenuation, reflection and emission from forested areas. Through these effects, canopy structure interacts with fluxes of heat, water, CO2, and volatile organic compounds, and affects patterns of soil moisture and ecosystem dynamics. The effects of canopy structure on the atmosphere are hard to measure and can be studied efficiently with large-eddy simulations. Remote sensing images that can be interpreted for biophysical properties are prone to errors due to effects of canopy structure, such as shading. However, the detailed 3-D canopy structure throughout a large spatial domain (up to several km2) is rarely available. We introduce a new method, namely the virtual canopy generator (V-CaGe), to construct finely detailed, 3-D, virtual forest canopies for use in remote sensing, and atmospheric and other environmental models. These virtual canopies are based on commonly observed mean and variance of biophysical forest properties, and a map (or a remotely-sensed image) of leaf area, or canopy heights, of a canopy subdomain. The canopies are constructed by inverse 2-D Fourier-transform of the observed spatial autocorrelation function and a random phase. The resulting field is expanded to 3-D by using empirical allometric profiles. We demonstrate that the V-CaGe can generate realistic simulation domains.

  8. Dual redundant display in bubble canopy applications

    NASA Astrophysics Data System (ADS)

    Mahdi, Ken; Niemczyk, James

    2010-04-01

    Today's cockpit integrator, whether for state of the art military fast jet, or piston powered general aviation, is striving to utilize all available panel space for AMLCD based displays to enhance situational awareness and increase safety. The benefits of a glass cockpit have been well studied and documented. The technology used to create these glass cockpits, however, is driven by commercial AMLCD demand which far outstrips the combined worldwide avionics requirements. In order to satisfy the wide variety of human factors and environmental requirements, large area displays have been developed to maximize the usable display area while also providing necessary redundancy in case of failure. The AMLCD has been optimized for extremely wide viewing angles driven by the flat panel TV market. In some cockpit applications, wide viewing cones are desired. In bubble canopy cockpits, however, narrow viewing cones are desired to reduce canopy reflections. American Panel Corporation has developed AMLCD displays that maximize viewing area, provide redundancy, while also providing a very narrow viewing cone even though commercial AMLCD technology is employed suitable for high performance AMLCD Displays. This paper investigates both the large area display architecture with several available options to solve redundancy as well as beam steering techniques to also limit canopy reflections.

  9. Evaluation of an ARPS-based canopy flow modeling system for use in future operational smoke prediction efforts

    NASA Astrophysics Data System (ADS)

    Kiefer, M. T.; Zhong, S.; Heilman, W. E.; Charney, J. J.; Bian, X.

    2013-06-01

    Efforts to develop a canopy flow modeling system based on the Advanced Regional Prediction System (ARPS) model are discussed. The standard version of ARPS is modified to account for the effect of drag forces on mean and turbulent flow through a vegetation canopy, via production and sink terms in the momentum and subgrid-scale turbulent kinetic energy (TKE) equations. Additionally, a downward decaying net radiation profile inside the canopy is used to account for the attenuation of net radiation by vegetation elements. As a critical step in the model development process, simulations performed with the new canopy model, termed ARPS-CANOPY, are examined and compared to observations from the Canopy Horizontal Array Turbulence Study (CHATS) experiment. Comparisons of mean and turbulent flow properties in a statistically homogeneous atmosphere are presented for two cases, one when the trees are dormant without leaves and another when the trees are full of mature leaves. The model is shown to reproduce the shape of the vertical profiles of mean wind, temperature, and TKE observed during the CHATS experiment, with errors generally smaller in the afternoon and in the case with stronger mean flow. Sensitivity experiments with relatively coarse (90 m) horizontal grid spacing retain the overall mean profile shapes and diurnal trends seen in the finer-resolution simulations. The work described herein is part of a larger effort to develop predictive tools for close-range (on the order of 1 km from the source) smoke dispersion from low-intensity fires within forested areas.

  10. Improved regional mapping of carbon, water, and energy land-surface fluxes through indicators of canopy light use efficiency

    NASA Astrophysics Data System (ADS)

    Schull, M. A.; Anderson, M. C.; Kustas, W. P.; Houborg, R.

    2013-12-01

    Recent studies have shown that canopy-scale estimates of chlorophyll (Cab) can be useful for constraining canopy light-use-efficiency (LUE) parameters used in many models of carbon fluxes. LUE is the amount of carbon that a plant can assimilate for a given amount of absorbed Photosynthetically Active Radiation (PAR), making it a key parameter for estimating carbon assimilation. Cab has been recognized as a vital pigment in the process of PAR absorption, and because of this radiative connection it is a quantity that can be estimated from remotely sensed data. The Two-Source Energy Balance (TSEB) model has been modified with a LUE-based sub-model of canopy resistance to facilitate coupled simulations of transpiration and carbon assimilation. The TSEB uses a daily estimate of nominal canopy LUE (LUEn), modulated over the diurnal cycle by varying conditions in light, humidity, CO2 concentration and temperature. We investigate the ability of canopy level chlorophyll as a proxy for capturing seasonal trends in the canopy LUEn required as input to the TSEB. The study uses field measured Cab over rain-fed and irrigated fields of corn and soybean. Initial results show that field-measured canopy Cab is non-linearly related to LUEn, with variability primarily relating to phenological changes due to senescence. Allowing a seasonally varying LUEn, derived based on an empirical relationship with observed Cab, resulted in improvements in carbon flux estimates from TSEB, and adjustments to the partitioning of total latent flux between canopy transpiration and soil evaporation. The observed Cab-LUE relationship provides an avenue for integrating the remotely sensed Cab and the TSEB model, facilitating improved mapping of coupled carbon, water, and energy fluxes across vegetated landscapes.

  11. 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

  12. Shifts in southern Wisconsin forest canopy and understory richness, composition, and heterogeneity.

    PubMed

    Rogers, David A; Rooney, Thomas P; Olson, Daniel; Waller, Donald M

    2008-09-01

    We resurveyed the under- and overstory species composition of 94 upland forest stands in southern Wisconsin in 2002-2004 to assess shifts in canopy and understory richness, composition, and heterogeneity relative to the original surveys in 1949-1950. The canopy has shifted from mostly oaks (Quercus spp.) toward more mesic and shade-tolerant trees (primarily Acer spp.). Oak-dominated early-successional stands and those on coarse, nutrient-poor soils changed the most in canopy composition. Understories at most sites (80%) lost native species, with mean species density declining 25% at the 1-m2 scale and 23.1% at the 20-m2 scale. Woody species have increased 15% relative to herbaceous species in the understory despite declining in absolute abundance. Initial canopy composition, particularly the abundance of red oaks (Quercus rubra and Q. velutina), predicted understory changes better than the changes observed in the overstory. Overall rates of native species loss were greater in later-successional stands, a pattern driven by differential immigration rather than differential extirpation. However, understory species initially found in early-successional habitats declined the most, particularly remnant savanna taxa with narrow or thick leaves. These losses have yet to be offset by compensating increases in native shade-adapted species. Exotic species have proliferated in prevalence (from 13 to 76 stands) and relative abundance (from 1.2% to 8.4%), but these increases appear unrelated to the declines in native species richness and heterogeneity observed. Although canopy succession has clearly influenced shifts in understory composition and diversity, the magnitude of native species declines and failure to recruit more shade-adapted species suggest that other factors now act to limit the richness, heterogeneity, and composition of these communities.

  13. Ground based remote sensing and physiological measurements provide novel insights into canopy photosynthetic optimization in arctic shrubs

    NASA Astrophysics Data System (ADS)

    Magney, T. S.; Griffin, K. L.; Boelman, N.; Eitel, J.; Greaves, H.; Prager, C.; Logan, B.; Oliver, R.; Fortin, L.; Vierling, L. A.

    2014-12-01

    Because changes in vegetation structure and function in the Arctic are rapid and highly dynamic phenomena, efforts to understand the C balance of the tundra require repeatable, objective, and accurate remote sensing methods for estimating aboveground C pools and fluxes over large areas. A key challenge addressing the modelling of aboveground C is to utilize process-level information from fine-scale studies. Utilizing information obtained from high resolution remote sensing systems could help to better understand the C source/sink strength of the tundra, which will in part depend on changes in photosynthesis resulting from the partitioning of photosynthetic machinery within and among deciduous shrub canopies. Terrestrial LiDAR and passive hyperspectral remote sensing measurements offer an effective, repeatable, and scalable method to understand photosynthetic performance and partitioning at the canopy scale previously unexplored in arctic systems. Using a 3-D shrub canopy model derived from LiDAR, we quantified the light regime of leaves within shrub canopies to gain a better understanding of how light interception varies in response to the Arctic's complex radiation regime. This information was then coupled with pigment sampling (i.e., xanthophylls, and Chl a/b) to evaluate the optimization of foliage photosynthetic capacity within shrub canopies due to light availability. In addition, a lab experiment was performed to validate evidence of canopy level optimization via gradients of light intensity and leaf light environment. For this, hyperspectral reflectance (photochemical reflectance index (PRI)), and solar induced fluorescence (SIF)) was collected in conjunction with destructive pigment samples (xanthophylls) and chlorophyll fluorescence measurements in both sunlit and shaded canopy positions.

  14. Contribution of lianas to plant area index and canopy structure in a Panamanian forest.

    PubMed

    Rodríguez-Ronderos, M Elizabeth; Bohrer, Gil; Sanchez-Azofeifa, Arturo; Powers, Jennifer S; Schnitzer, Stefan A

    2016-12-01

    Lianas are an important component of tropical forests, where they reduce tree growth, fecundity, and survival. Competition for light from lianas may be intense; however, the amount of light that lianas intercept is poorly understood. We used a large-scale liana-removal experiment to quantify light interception by lianas in a Panamanian secondary forest. We measured the change in plant area index (PAI) and forest structure before and after cutting lianas (for 4 yr) in eight 80 m × 80 m plots and eight control plots (16 plots total). We used ground-based LiDAR to measure the 3-dimensional canopy structure before cutting lianas, and then annually for 2 yr afterwards. Six weeks after cutting lianas, mean plot PAI was 20% higher in control vs. liana removal plots. One yr after cutting lianas, mean plot PAI was ~17% higher in control plots. The differences between treatments diminished significantly 2 yr after liana cutting and, after 4 yr, trees had fully compensated for liana removal. Ground-based LiDAR revealed that lianas attenuated light in the upper- and middle-forest canopy layers, and not only in the upper canopy as was previously suspected. Thus, lianas compete with trees by intercepting light in the upper- and mid-canopy of this forest.

  15. Daily and seasonal dynamics of remotely sensed photosynthetic efficiency in tree canopies.

    PubMed

    Pieruschka, Roland; Albrecht, Hendrik; Muller, Onno; Berry, Joseph A; Klimov, Denis; Kolber, Zbigniew S; Malenovský, Zbyněk; Rascher, Uwe

    2014-07-01

    The photosynthesis of various species or even a single plant varies dramatically in time and space, creating great spatial heterogeneity within a plant canopy. Continuous and spatially explicit monitoring is, therefore, required to assess the dynamic response of plant photosynthesis to the changing environment. This is a very challenging task when using the existing portable field instrumentation. This paper reports on the application of a technique, laser-induced fluorescence transient (LIFT), developed for ground remote measurement of photosynthetic efficiency at a distance of up to 50 m. The LIFT technique was used to monitor the seasonal dynamics of selected leaf groups within inaccessible canopies of deciduous and evergreen tree species. Electron transport rates computed from LIFT measurements varied over the growth period between the different species studied. The LIFT canopy data and light-use efficiency measured under field conditions correlated reasonably well with the single-leaf pulse amplitude-modulated measurements of broadleaf species, but differed significantly in the case of conifer tree species. The LIFT method has proven to be applicable for a remote sensing assessment of photosynthetic parameters on a diurnal and seasonal scale; further investigation is, however, needed to evaluate the influence of complex heterogeneous canopy structures on LIFT-measured chlorophyll fluorescence parameters.

  16. Discriminating crop and other canopies by overlapping binary image layers

    NASA Astrophysics Data System (ADS)

    Doi, Ryoichi

    2013-02-01

    For optimal management of agricultural fields by remote sensing, discrimination of the crop canopy from weeds and other objects is essential. In a digital photograph, a rice canopy was discriminated from a variety of weed and tree canopies and other objects by overlapping binary image layers of red-green-blue and other color components indicating the pixels with target canopy-specific (intensity) values based on the ranges of means ±(3×) standard deviations. By overlapping and merging the binary image layers, the target canopy specificity improved to 0.0015 from 0.027 for the yellow 1× standard deviation binary image layer, which was the best among all combinations of color components and means ±(3×) standard deviations. The most target rice canopy-likely pixels were further identified by limiting the pixels at different luminosity values. The discriminatory power was also visually demonstrated in this manner.

  17. Modeling directional thermal radiance from a forest canopy

    NASA Technical Reports Server (NTRS)

    Mcguire, M. J.; Balick, L. K.; Smith, J. A.; Hutchison, B. A.

    1989-01-01

    The thermal vegetation canopy radiance model of Smith et al. (1981) is extended to account for the geometrically rough structure of a forest canopy. Fourier series expansion of a canopy height profile is used to calculate improved view facts which partially account for directional variations in canopy thermal radiance transfers. Predictions from the Smith model and the modified model are compared with experimental data obtained over a deciduous forest site in Tennessee. The results show that thermal radiance from a forest canopy depends on sensor viewing angle, solar position, and the degree of geometric roughness of the canopy surface. The maximum off-nadir angle variation in the original model was 1.6 deg C, compared with 4.4 C for the modified model.

  18. Determining density of maize canopy. 1: Digitized photography

    NASA Technical Reports Server (NTRS)

    Stoner, E. R.; Baumgardner, M. F.; Swain, P. H.

    1972-01-01

    The relationship between different densities of maize (Zea mays L.) canopies and the energy reflected by these canopies was studied. Field plots were laid out, representing four growth stages of maize, on a dark soil and on a very light colored surface soil. Spectral and spatial data were obtained from color and color infrared photography taken from a vertical distance of 10 m above the maize canopies. Estimates of ground cover were related to field measurements of leaf area index. Ground cover was predicted from leaf area index measurements by a second order equation. Color infrared photography proved helpful in determining the density of maize canopy on dark soils. Color photography was useful for determining canopy density on light colored soils. The near infrared dye layer is the most valuable in canopy density determinations.

  19. Modelling variability in radiative fluxes on snow surfaces beneath coniferous canopies

    NASA Astrophysics Data System (ADS)

    Essery, R.; Hardy, J.; Link, T.; Marks, D.; Pomeroy, J.; Rowlands, A.; Rutter, N.

    2005-12-01

    Absorption, scattering and emission of solar and thermal radiation by coniferous canopies can have a large influence on the surface energy balance of snow in forests. The high variability of radiative fluxes in sparse or discontinuous forests cannot be captured by simple two-stream canopy radiation models, and sophisticated ray-tracing models are too computationally and data intensive for practical applications. An efficient spatial model representing individual trees as simple geometric primitives with a stochastic component for smaller scales is presented, and model results are compared with measurements from radiometer arrays. Forest structure information for the model can be obtained from manual mapping, hemispherical photography, aerial photography or airborne laser scanning. The model is used to investigate spatial and temporal scaling of radiative fluxes at the snow surface.

  20. Anisotropy of thermal infrared exitance above and within plant canopies

    NASA Technical Reports Server (NTRS)

    Pawu, Kyaw Tha

    1991-01-01

    Any significant angular dependence of the emitted long wave radiation could result in errors in remotely estimated energy budgets or evapotranspiration. Empirical data and thermal infrared radiation models are reviewed in reference to anisotropic emissions from the plant canopy. The biometeorological aspects of linking longwave models with plant canopy energy budgets and micrometeorology are discussed. A new soil plant atmosphere model applied to anisotropic longwave emissions from a canopy is presented. Time variation of thermal infrared emission measurements is discussed.

  1. Leaf Phenology of Amazonian Canopy Trees as Revealed by Spectral and Physiochemical Measurements

    NASA Astrophysics Data System (ADS)

    Chavana-Bryant, C.; Gerard, F. F.; Malhi, Y.; Enquist, B. J.; Asner, G. P.

    2013-12-01

    The phenological dynamics of terrestrial ecosystems reflect the response of the Earth's biosphere to inter- and intra-annual dynamics of climatic and hydrological regimes. Some Dynamic Global Vegetation Models (GDVMs) have predicted that by 2050 the Amazon rainforest will begin to dieback (Cox et al. 2000, Nature) or that the ecosystem will become unsustainable (Salazar et al. 2007, GRL). One major component in DGVMs is the simulation of vegetation phenology, however, modelers are challenged with the estimation of tropical phenology which is highly complex. Current modeled phenology is based on observations of temperate vegetation and accurate representation of tropical phenology is long overdue. Remote sensing (RS) data are a key tool in monitoring vegetation dynamics at regional and global scales. Of the many RS techniques available, time-series analysis of vegetation indices (VIs) has become the most common approach in monitoring vegetation phenology (Samanta et al. 2010, GRL; Bradley et al. 2011, GCB). Our research focuses on investigating the influence that age related variation in the spectral reflectance and physiochemical properties of leaves may have on VIs of tropical canopies. In order to do this, we collected a unique leaf and canopy phenological dataset at two different Amazonian sites: Inselberg, French Guyana (FG) and Tambopata, Peru (PE). Hyperspectral reflectance measurements were collected from 4,102 individual leaves sampled to represent different leaf ages and vertical canopy positions (top, mid and low canopy) from 20 different canopy tree species (8 in FG and 12 in PE). These leaf spectra were complemented with 1) leaf physical measurements: fresh and dry weight, area and thickness, LMA and LWC and 2) leaf chemical measurements: %N, %C, %P, C:N and d13C. Canopy level observations included top-of-canopy reflectance measurements obtained using a multispectral 16-band radiometer, leaf demography (tot. number and age distribution) and branch

  2. 9. North Plant, View of Canopied Loading Dock with Powerhouse ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. North Plant, View of Canopied Loading Dock with Powerhouse to Left, Looking Northwest - Atwater Kent Manufacturing Company, North Plant, 5000 Wissahickon Avenue, Philadelphia, Philadelphia County, PA

  3. Specular, diffuse and polarized imagery of an oat canopy

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern C.; De Venecia, Kurt J.

    1988-01-01

    Light, polarized by specular reflection, has been found to be an important part of the light scattered by several measured plant canopies. The authors investigate for one canopy the relative importance of specularly reflected sunlight, specularly reflected light from other sources including skylight, and diffusely upwelling light. Polarization images are used to gain increased understanding of the radiation transfer process in a plant canopy. Analysis of the results suggests that properly analyzed polarized remotely sensed data, acquired under specific atmospheric conditions by a specially designed sensor, potentially provide measures of physiological and morphological states of plants in a canopy.

  4. 13. Detail showing canopy at southeast corner; note single column ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. Detail showing canopy at southeast corner; note single column supporting structure - Fort Hood, World War II Temporary Buildings, Cold Storage Building, Seventeenth Street, Killeen, Bell County, TX

  5. Radar return from a continuous vegetation canopy

    NASA Technical Reports Server (NTRS)

    Bush, T. F.; Ulaby, F. T.

    1975-01-01

    The radar backscatter coefficient, sigma deg, of alfalfa was investigated as a function of both radar parameters and the physical characteristics of the alfalfa canopy. Measurements were acquired with an 8-18 GHz FM-CW mobile radar over an angular range of 0 - 70 deg as measured from nadir. The experimental data indicates that the excursions of sigma deg at nadir cover a range of nearly 18 dB during one complete growing cycle. An empirical model for sigma deg was developed which accounts for its variability in terms of soil moisture, plant moisture and plant height.

  6. LASER ALTIMETER CANOPY HEIGHT PROFILES: METHODS AND VALIDATION FOR CLOSED-CANOPY, BROADLEAF FORESTS. (R828309)

    EPA Science Inventory

    Abstract

    Waveform-recording laser altimeter observations of vegetated landscapes provide a time-resolved measure of laser pulse backscatter energy from canopy surfaces and the underlying ground. Airborne laser altimeter waveform data was acquired using the Scanning Lid...

  7. Predicting Photosynthetic Fluxes from Spectral Reflectance of Leaves and Canopies

    NASA Technical Reports Server (NTRS)

    Gamon, John A.

    1997-01-01

    The central hypothesis of this study has been that photosynthetic efficiency and capacity can be predicted from 'physiological reflectance indices' derived from spectral reflectance of leaves and canopies. I have approached this topic with a combination of laboratory and field experiments, and have also explored the potential of deriving a meaningful physiological index from imaging spectrometry (e.g. AVIRIS). A few highlights are presented below. The main emphasis has been on the 'Photochemical Reflectance Index' (PRI), derived from reflectance at 531 nm and 570 nm. Unlike most 'conventional' vegetation indices (e.g. NDVI), PRI changes rapidly both with illumination and physiological state, because it detects the interconversion of xanthophyll cycle pigments, which serve as photoregulatory pigments and control energy distribution for the photosynthetic system. This approach has differed dramatically from most remote sensing in that it has emphasized temporal variation in narrow-band spectral signatures, instead of spatial patterns of broadband indices. Our primary conclusion has been that PRI works well as an index of photosynthetic light-use efficiency at the leaf scale, much in the same way as the fluorescence index DeltaF/Fm. However, unlike DeltaF/Fm which must be measured at close scales, PRI can be sampled at a range of spatial scales, presenting the possibility of monitoring photosynthetic fluxes remotely.

  8. Linkages of Biodiversity and Canopy Lidar Metrics in Central Africa

    NASA Astrophysics Data System (ADS)

    Laporte, N. T.; Horning, N.; Morgan, D.

    2012-12-01

    Central Africa contains the second largest dense humid forest in the world, and one of the largest carbon and biodiversity reservoirs on Earth. With 60% of the forest currently under logging concessions, the Congo basin is poised to undergo extensive land use change. Increases in bushmeat trade, resulting from extensification of logging roads, have already been well documented. From a quantitative standpoint, little is known of the structure of these forests, how logging affects forest biomass or functioning, and how canopy habitat heterogeneity relates to animal species richness or diversity. Here we document, using random forest and MaxEnt, how information from GLAS lidar metrics, ALOS-PalSAR and Landsat imagery, combined with field observations of great ape nest locations ( figure 1) and vegetation types, can be merged to create a map of gorilla and chimpanzee habitat in a region spanning Cameroon, the Republic of Congo, and the Central African Republic. From an initial selection of 48 variables we found the most important for mapping habitat suitability were a combination of PalSAR backscatter, NDVI image texture. Landsat ETM+ top of the atmosphere reflectance and principle component images. While NDVI from ETM+bands was an important predictor of gorilla and chimpanzee nest presence, species-specific differences in habitat use were also identified. Tree canopy height from GLAS was the most important variable predicting chimpanzee nesting habitat, while Landsat ETM+ bands were most important for gorilla nesting habitat. These preliminary results indicate merging field observations with satellite imagery promises to significantly improve our understanding of ape habitat-use at the landscape scale.ombining GLAS lidar metrics, ALOS-PalSAR and Landsat imager with field observations of great ape nest locations for habitat mapping in C. Africa

  9. Modelling bidirectional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

    NASA Astrophysics Data System (ADS)

    Ashworth, Kirsti; Chung, Serena H.; McKinney, Karena A.; Liu, Ying; Munger, J. William; Martin, Scot T.; Steiner, Allison L.

    2016-12-01

    The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem scale, a process not currently considered in regional- or global-scale atmospheric chemistry models.We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions, FORCAsT was able to successfully simulate the observed bidirectional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

  10. A sensor network driven micrometeorology study in the Serro do Mar rainforest canopy, southeast Brazil

    NASA Astrophysics Data System (ADS)

    Fatland, D. R.; Da Rocha, H. R.; Carlson, D.; Gupchup, J. A.; Salles, J.; Terzis, A.; Nobre, C.

    2009-12-01

    We have engaged in a collaborative micrometeorology pilot study towards a deeper understanding of the rainforest canopy coupling to the lower atmosphere. As motivated by researchers at the University of Sao Paulo the statement of the scientific problem is: To what extent can fine-scale spatio-temporal measurement of temperature and humidity be used to better understand and refine estimates of surface heat and water vapor flux between rainforest canopy and the lower atmosphere? Here the desired spatial scale is meters and the sampling interval is thirty seconds. To address this scientific problem in an expansible manner we have adapted Johns Hopkins University Life Under Your Feet soil ecology wireless sensor networks to a scaffold grid placed high in the rainforest canopy. The deployment is at an experimental site in the Parque Estadual da Serro do Mar, a state reserve and coastal rainforest approximately 200 km east of Sao Paulo Brazil. Project support and coordination has been provided by Microsoft Research (MSR) with the idea of continuing from the pilot study to larger-scale research in Amazonia and towards making the project technology broadly adoptable. The underlying technological challenge is the optimization of good data harvested from remote study sites per research budget dollar. We present here a description of the constituent technology, methods of adaptation, cost of implementation, overview of environmental obstacles and preliminary study results.

  11. Validation of Vegetation Canopy Lidar sub-canopy topography measurements for a dense tropical forest

    NASA Astrophysics Data System (ADS)

    Hofton, M. A.; Rocchio, L. E.; Blair, J. B.; Dubayah, R.

    2002-11-01

    Large footprint (greater than 10 m wide) laser altimetry is a useful technique for mapping topography (including sub-canopy), canopy height and vertical structure in densely vegetated areas. In March 1998, the Laser Vegetation Imaging Sensor (LVIS), an airborne laser altimeter, mapped a ˜800 km 2 area of Costa Rica including the La Selva Biological Station using 25 m-diameter footprints as part of the pre-launch activities of the Vegetation Canopy Lidar (VCL) Mission. To investigate the utility of the lidar technique for making sub-canopy topography measurements, the precision and accuracy of the LVIS elevation measurements from this mission are assessed. Crossover analysis using laser shots whose recorded waveforms contained more than 50% of the total returned energy within their lowest reflections show the elevations have a precision of better than 1 m. Comparison of the LVIS elevations with coincident in situ ground elevation data reveals that the measurements are within ˜1.5 m of each other on less than 3° slopes. All measurements are within ˜5 m of each other (on slopes of up to 30°). These are very encouraging results given that the forests of this region are some of the densest, most complex on Earth, and that mapping their sub-canopy topography are near-impossible using any other remote sensing technique. Given the similarity of the measurement processes of the LVIS and VCL systems, these results suggest that the topographic measurements made by the VCL will meet stated accuracy goals under the majority of measurement conditions.

  12. A tree canopy height delineation method based on Morphological Reconstruction—Open Crown Decomposition

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Jing, L.; Li, Y.; Tang, Y.; Li, H.; Lin, Q.

    2016-04-01

    For the purpose of forest management, high resolution LIDAR and optical remote sensing imageries are used for treetop detection, tree crown delineation, and classification. The purpose of this study is to develop a self-adjusted dominant scales calculation method and a new crown horizontal cutting method of tree canopy height model (CHM) to detect and delineate tree crowns from LIDAR, under the hypothesis that a treetop is radiometric or altitudinal maximum and tree crowns consist of multi-scale branches. The major concept of the method is to develop an automatic selecting strategy of feature scale on CHM, and a multi-scale morphological reconstruction-open crown decomposition (MRCD) to get morphological multi-scale features of CHM by: cutting CHM from treetop to the ground; analysing and refining the dominant multiple scales with differential horizontal profiles to get treetops; segmenting LiDAR CHM using watershed a segmentation approach marked with MRCD treetops. This method has solved the problems of false detection of CHM side-surface extracted by the traditional morphological opening canopy segment (MOCS) method. The novel MRCD delineates more accurate and quantitative multi-scale features of CHM, and enables more accurate detection and segmentation of treetops and crown. Besides, the MRCD method can also be extended to high optical remote sensing tree crown extraction. In an experiment on aerial LiDAR CHM of a forest of multi-scale tree crowns, the proposed method yielded high-quality tree crown maps.

  13. Studying the Impact of the Three Dimensional Canopy Structure on LIDAR Waveforms Evaluated with Field Measurements

    NASA Astrophysics Data System (ADS)

    Xu, L.; Knyazikhin, Y.; Myneni, R. B.; Strahler, A. H.; Schaaf, C.; Antonarakis, A. S.; Moorcroft, P. R.

    2011-12-01

    The three-dimensional structure of a forest - its composition, density, height, crown geometry, within-crown foliage distribution and properties of individual leaves - has a direct impact on the lidar waveform. The pair-correlation function defined as the probability of finding simultaneously phytoelements at two points is the most natural and physically meaningful descriptor of the canopy structure over wide range of scales. The stochastic radiative transfer equations naturally admit this measure and thus provide a powerful means to investigate 3D canopy from space. NASA's Airborne Laser Vegetation Imaging Sensor (LVIS) and ground based data on canopy structure acquired over 5 sites in New England, California and La Selva (Costa Rica) tropical forest were analyzed to assess the impact of 3D canopy structure on lidar waveform and the ability of stochastic radiative transfer equations to simulate the 3D effects. Our results suggest the pair correlation function is sensitive to horizontal and vertical clumping, crown geometry and spatial distribution of trees. Its use in the stochastic radiative transfer equation allows us to accurately simulate the effects of 3D canopy structure on the lidar waveform. Specifically, we found that (1) attenuation of the waveform occurs at a slower rate than 1D models predict; this may result in an underestimation of foliage profile if 3D effects are ignored; (2) 1D model is unable to match simulated waveform and measured surface reflectance, i.e., an unrealistic high value of surface reflectance needs to be used to simulate ground return of sparse vegetation; (3) spatial distribution of trees has a strong impact on the lidar waveform. Simple analytical models of the pair-correlation function will also be discussed.

  14. Canopy Water Balance of an Elfin Cloud Forest at Alakahi, Hawaii

    NASA Astrophysics Data System (ADS)

    Delay, J. K.; Giambelluca, T. W.; Juvik, J. O.

    2006-12-01

    The contribution of cloudwater or fog, to the water balance of tropical mountain forests has been the subject of increasing attention in recent decades. This study estimates the water falling to the forest floor as a result of cloud water interception (CWI) by the canopy in a short stature tropical montane cloud forest (TMCF) with abundant epiphytic vegetation. The study site, located in the Alakahi region of Kohala on the island of Hawai'i, receives abundant orographic rainfall and is frequently immersed in clouds. Cloudwater interception was estimated from meteorological data using the Gash interception model to calculate canopy water balance at the event scale for precipitation events with, and without fog precipitation recorded by a mechanical collector in the forest canopy. Cloudwater interception was derived as a residual by comparison of measured and predicted throughfall during events with fog precipitation. Storage capacity of the major canopy bryophytes and ferns, as well as that of the mossy mat carpeting the forest floor, was also estimated from observed distribution and storage capacity. The calculated contribution of CWI was equivalent to 11% of the total throughfall. The annualized 219 mm is substantially lower than for CWI previously estimated at a nearby exposed, forest-edge location where estimated CWI and throughfall exceeded rainfall. Canopy epiphyte water storage capacity accounted for 3.53 mm and the mossy mat on the forest floor was estimated to store up to 22 mm. The epiphyte storage during precipitation events was far less than the estimated storage capacity; however, epiphytes represented a significant potential moisture source for interception loss between precipitation events.

  15. EFFECTS OF ELEVATED ATMOSPHERIC CO{sub 2} ON CANOPY TRANSPIRATION IN SENESCENT SPRING WHEAT

    SciTech Connect

    GROSSMAN,S.; KIMBALL,B.A.; HUNSAKER,D.J.; LONG,S.P.; GARCIA,R.L.; KARTSCHALL,TH.; WALL,G.W.; PINTER,P.J,JR.; WECHSUNG,F.; LAMORTE,R.L.

    1998-12-31

    The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s} the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to 20% and a decrease in simulated seasonal canopy transpiration by 10%. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about 5%.

  16. Canopy hot-spot as crop identifier

    SciTech Connect

    Gerstl, S.A.W.; Simmer, C.; Powers, B.J.

    1986-05-01

    Illuminating any reflective rough or structured surface by a directional light source results in an angular reflectance distribution that shows a narrow peak in the direction of retro-reflection. This is called the Heiligenschein or hot-spot of vegetation canopies and is caused by mutual shading of leaves. The angular intensity distribution of the hot-spot, its brightness and slope, are therefore indicators of the plant's geometry. We propose the use of hot-spot characteristics as crop identifiers in satellite remote sensing because the canopy hot-spot carries information about plant stand architecture that is more distinctive for different plant species than, for instance, their spectral reflectance characteristics. A simple three-dimensional Monte Carlo/ray tracing model and an analytic two-dimensional model are developed to estimate the angular distribution of the hot-spot as a function of the size of the plant leaves. The results show that the brightness-distribution and slope of the hot-spot change distinctively for different leaf sizes indicating a much more peaked maximum for the smaller leaves.

  17. The Spatio-temporal Statistical Structure and Ergodic Behaviour of Scalar Turbulence Within a Rod Canopy

    NASA Astrophysics Data System (ADS)

    Ghannam, Khaled; Poggi, Davide; Porporato, Amilcare; Katul, Gabriel G.

    2015-12-01

    Connections between the spatial and temporal statistics of turbulent flow, and their possible convergence to ensemble statistics as assumed by the ergodic hypothesis, are explored for passive scalars within a rod canopy. While complete ergodicity is not expected to apply over all the spatial domain within such heterogeneous flows, the fact that canopy turbulence exhibits self-similar characteristics at a given depth within the canopy encourages a discussion on necessary conditions for an `operational' ergodicity framework. Flows between roughness elements such as within canopies exhibit features that distinguish them from their well-studied classical boundary-layer counterparts. These differences are commonly attributed to short-circuiting of the energy cascade and the prevalence of intermittent von Kármán vortex streets in the deeper layers of the canopy. Using laser-induced fluorescence measurements at two different depths within a rod canopy situated in a large flume, the spatio-temporal statistical properties and concomitant necessary conditions for ergodicity of passive scalar turbulence statistics are evaluated. First, the integral time and length scales are analyzed and their corresponding maximum values are used to guide the construction of an ensemble of independent realizations from repeated spatio-temporal concentration measurements. As a statistical analysis for an operational ergodicity check, a Kolmogorov-Smirnov test on the distributions of temporal and spatial concentration series against the ensemble was conducted. The outcome of this test reveals that ergodicity is reasonably valid over the entire domain except close to the rod elements where wake-induced inhomogeneities and damped turbulence prevail. The spatial concentration statistics within a grid-cell (square domain formed by four corner rods) appear to be less ergodic than their temporal counterparts, which is not surprising given the periodicity and persistence of von Kármán vortices in

  18. 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.

  19. Scales

    ScienceCinema

    Murray Gibson

    2016-07-12

    Musical scales involve notes that, sounded simultaneously (chords), sound good together. The result is the left brain meeting the right brain — a Pythagorean interval of overlapping notes. This synergy would suggest less difference between the working of the right brain and the left brain than common wisdom would dictate. The pleasing sound of harmony comes when two notes share a common harmonic, meaning that their frequencies are in simple integer ratios, such as 3/2 (G/C) or 5/4 (E/C).

  20. Scales

    SciTech Connect

    Murray Gibson

    2007-04-27

    Musical scales involve notes that, sounded simultaneously (chords), sound good together. The result is the left brain meeting the right brain — a Pythagorean interval of overlapping notes. This synergy would suggest less difference between the working of the right brain and the left brain than common wisdom would dictate. The pleasing sound of harmony comes when two notes share a common harmonic, meaning that their frequencies are in simple integer ratios, such as 3/2 (G/C) or 5/4 (E/C).

  1. Simulation of Canopy CO2/H2O Fluxes for a Rubber (Hevea Brasiliensis) Plantation in Central Cambodia: The Effect of the Regular Spacing of Planted Trees

    SciTech Connect

    Kumagai, Tomo'omi; Mudd, Ryan; Miyazawa, Yoshiyuki; Liu, Wen; Giambelluca, Thomas; Kobayashi, N.; Lim, Tiva Khan; Jomura, Mayuko; Matsumoto, Kazuho; Huang, Maoyi; Chen, Qi; Ziegler, Alan; Yin, Song

    2013-09-10

    We developed a soil-vegetation-atmosphere transfer (SVAT) model applicable to simulating CO2 and H2O fluxes from the canopies of rubber plantations, which are characterized by distinct canopy clumping produced by regular spacing of plantation trees. Rubber (Hevea brasiliensis Müll. Arg.) plantations, which are rapidly expanding into both climatically optimal and sub-optimal environments throughout mainland Southeast Asia, potentially change the partitioning of water, energy, and carbon at multiple scales, compared with traditional land covers it is replacing. Describing the biosphere-atmosphere exchange in rubber plantations via SVAT modeling is therefore essential to understanding the impacts on environmental processes. The regular spacing of plantation trees creates a peculiar canopy structure that is not well represented in most SVAT models, which generally assumes a non-uniform spacing of vegetation. Herein we develop a SVAT model applicable to rubber plantation and an evaluation method for its canopy structure, and examine how the peculiar canopy structure of rubber plantations affects canopy CO2 and H2O exchanges. Model results are compared with measurements collected at a field site in central Cambodia. Our findings suggest that it is crucial to account for intensive canopy clumping in order to reproduce observed rubber plantation fluxes. These results suggest a potentially optimal spacing of rubber trees to produce high productivity and water use efficiency.

  2. 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.

  3. Technological Advancement in Tower-Based Canopy Reflectance Monitoring: The AMSPEC-III System

    PubMed Central

    Tortini, Riccardo; Hilker, Thomas; Coops, Nicholas C.; Nesic, Zoran

    2015-01-01

    Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and few cross-comparisons have been undertaken. This paper discusses the design evolution of the Automated Multiangular SPectro-radiometer for Estimation of Canopy reflectance (AMSPEC) series of instruments. Specifically, we assess the performance of the PP-Systems Unispec-DC and Ocean Optics JAZ-COMBO spectro-radiometers installed on an updated, tower-based AMSPEC-III system. We demonstrate the interoperability of these spectro-radiometers, and the results obtained suggest that JAZ-COMBO can successfully be used to substitute more expensive measurement units for detecting and investigating photosynthesis and canopy spectra. We demonstrate close correlations between JAZ-COMBO and Unispec-DC measured canopy radiance (0.75 ≤ R2 ≤ 0.85) and solar irradiance (0.95 ≤ R2 ≤ 0.96) over a three month time span. We also demonstrate close agreement between the bi-directional distribution functions obtained from each instrument. We conclude that cost effective alternatives may allow a network of AMSPEC-III systems to simultaneously monitor various vegetation types in different ecosystems. This will allow to scale and improve our understanding of the interactions between vegetation physiology and spectral characteristics, calibrate broad-scale observations to stand-level measurements, and ultimately lead to improved understanding of changing vegetation spectral features from satellite. PMID:26703602

  4. Technological Advancement in Tower-Based Canopy Reflectance Monitoring: The AMSPEC-III System.

    PubMed

    Tortini, Riccardo; Hilker, Thomas; Coops, Nicholas C; Nesic, Zoran

    2015-12-19

    Understanding plant photosynthesis, or Gross Primary Production (GPP), is a crucial aspect of quantifying the terrestrial carbon cycle. Remote sensing approaches, in particular multi-angular spectroscopy, have proven successful for studying relationships between canopy-reflectance and plant-physiology processes, thus providing a mechanism to scale up. However, many different instrumentation designs exist and few cross-comparisons have been undertaken. This paper discusses the design evolution of the Automated Multiangular SPectro-radiometer for Estimation of Canopy reflectance (AMSPEC) series of instruments. Specifically, we assess the performance of the PP-Systems Unispec-DC and Ocean Optics JAZ-COMBO spectro-radiometers installed on an updated, tower-based AMSPEC-III system. We demonstrate the interoperability of these spectro-radiometers, and the results obtained suggest that JAZ-COMBO can successfully be used to substitute more expensive measurement units for detecting and investigating photosynthesis and canopy spectra. We demonstrate close correlations between JAZ-COMBO and Unispec-DC measured canopy radiance (0.75 ≤ R² ≤ 0.85) and solar irradiance (0.95 ≤ R² ≤ 0.96) over a three month time span. We also demonstrate close agreement between the bi-directional distribution functions obtained from each instrument. We conclude that cost effective alternatives may allow a network of AMSPEC-III systems to simultaneously monitor various vegetation types in different ecosystems. This will allow to scale and improve our understanding of the interactions between vegetation physiology and spectral characteristics, calibrate broad-scale observations to stand-level measurements, and ultimately lead to improved understanding of changing vegetation spectral features from satellite.

  5. Plot-level aboveground woody biomass modeling using canopy height and auxiliary remote sensing data in a heterogeneous savanna

    NASA Astrophysics Data System (ADS)

    Gwenzi, David; Lefsky, Michael Andrew

    2016-01-01

    Remote sensing studies aiming at assessing woody biomass have demonstrated a strong relationship between canopy height and plot-level aboveground biomass, but most of these studies focused on closed canopy forests. To date, a few studies have examined the strength and reliability of this relationship using large footprint lidar in savannas. Furthermore, there have been few studies of appropriate methods for the comparison of models that relate aboveground biomass to canopy height metrics without consideration of variation in species composition (generic models) to models developed for individual species composition or vegetation types. We developed generic models using the classical least-squares regression modeling approach to relate selected canopy height metrics to aboveground woody biomass in a savanna landscape. Hierarchical Bayesian analysis (HBA) was then used to explore the implications of using generic or composition-specific models. Our study used the estimates of aboveground biomass from field data, canopy height estimates from airborne discrete return lidar, and a proxy for canopy cover (the Normalized Difference Vegetation Index) from Landsat 5 Thematic Mapper data, collected from the oak savannas of Tejon Ranch Conservancy in Kern County, California. Models were developed and analyzed using estimates of canopy height and aboveground biomass calculated at the level of 50-m diameter plots, comparable with footprint diameter of existing large footprint spaceborne lidar data. The two generic models that incorporated canopy cover proxies performed better than one model that did not use canopy cover information. From the HBA, we found out that for all models both the intercept and slope had interspecific variability. The valley oak dominated plots consistently had higher slopes and intercepts, whereas the plots dominated by blue oaks had the lowest. However, the intercept and slope values of the composition-specific models did not differ much from the

  6. Wind—Friend or Foe of Canopy Management?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Trellising and training in vineyards represent money and effort invested to maximize canopy photosynthesis and to optimize solar radiation exposure at the fruit. Canopies that are symmetrical around the cordon are desired, and vineyard managers often follow conventional wisdom of orienting vine rows...

  7. Identifying Roads and Trains Under Canopy Using Lidar

    DTIC Science & Technology

    2007-09-01

    NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited IDENTIFYING ROADS AND...identifying roads and trails hidden under dense jungle and forest canopies. The four analyzed regions include the Elkhorn Slough in Central California ...canopies. The four analyzed regions include the Elkhorn Slough in Central California (2005), Kahuku Training Area on the North side of Oahu Island in Hawaii

  8. Thermal Infrared Hot Spot and Dependence on Canopy Geometry

    NASA Technical Reports Server (NTRS)

    Smith, James A.; Ballard, Jerrell R., Jr.; Smith, David E. (Technical Monitor)

    2001-01-01

    We perform theoretical calculations of the canopy thermal infrared (TIR) hot spot using a first principles 3-D model described earlier. Various theoretical canopies of varying leaf size and for differing canopy height are used to illustrate the magnitude of the TIR effect. Our results are similar to predicted behavior in the reflective hot spot as a function of canopy geometry and comparable to TIR measurements from the literature and our own simple ground experiments. We apply the MODTRAN atmospheric code to estimate the at-sensor variation in brightness temperature with view direction in the solar principal plane. For simple homogeneous canopies, we predict canopy thermal infrared hot spot variations of 2 degrees C at the surface with respect to nadir viewing. Dependence on leaf size is weak as long as the ratio of leaf size to canopy height is maintained. However, the angular width of the hot spot increases as the ratio of leaf diameter to canopy height increases. Atmospheric effects minimize but do not eliminate the TIR hot spot at satellite altitudes.

  9. Estimation of Canopy Foliar Biomass with Spectral Reflectance Measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Canopy foliar biomass, defined as the product of leaf dry matter content and leaf area index, is an important measurement for global biogeochemical cycles. This study explores the potential for retrieving foliar biomass in green canopies using a spectral index, the Normalized Dry Matter Index (NDMI)...

  10. Canopy position has a profound effect on soybean seed composition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although soybean seeds appear homogenous their composition (protein, oil and mineral concentrations) can vary significantly with canopy position. Seeds produced at the top of the canopy have higher concentrations of protein but less oil and minerals such as Mg, Fe, and Cu compared to seeds produced ...

  11. Aerially released spray penetration of a tall coniferous canopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An aerial spray deposition project was designed to evaluate aerial application to an Eastern Hemlock (Tsuga canadensis) canopy to combat Hemlock Woolly Adelgid (Adelges tsugae). This adelgid offers a difficult target residing in the forest canopy at the nodes of branchlets. The study collected 1680 ...

  12. Effect of Stability on Mixing in Open Canopies. Chapter 4

    NASA Technical Reports Server (NTRS)

    Lee, Young-Hee; Mahrt, L.

    2005-01-01

    In open canopies, the within-canopy flux from the ground surface and understory can account for a significant fraction of the total flux above the canopy. This study incorporates the important influence of within-canopy stability on turbulent mixing and subcanopy fluxes into a first-order closure scheme. Toward this goal, we analyze within-canopy eddy-correlation data from the old aspen site in the Boreal Ecosystem - Atmosphere Study (BOREAS) and a mature ponderosa pine site in Central Oregon, USA. A formulation of within-canopy transport is framed in terms of a stability- dependent mixing length, which approaches Monin-Obukhov similarity theory above the canopy roughness sublayer. The new simple formulation is an improvement upon the usual neglect of the influence of within-canopy stability in simple models. However, frequent well-defined cold air drainage within the pine subcanopy inversion reduces the utility of simple models for nocturnal transport. Other shortcomings of the formulation are discussed.

  13. Water stress effects on spatially referenced cotton crop canopy properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    rop canopy temperature is known to be affected by water stress. Canopy reflectance can also be impacted as leaf orientation and color respond to the stress. As sensor systems are investigated for real-time management of irrigation and nitrogen, it is essential to understand how the data from the sen...

  14. A plant canopy light absorption model with application to wheat

    NASA Technical Reports Server (NTRS)

    Chance, J. E.; Lemaster, E. W.

    1977-01-01

    From the light absorption model the absorption of light in the photosynthetically active region of the spectrum was calculated for a Penjamo wheat crop for several situations including: (1) the percent absorption of the incident radiation by a canopy having a four layer structure; (2) the percent absorption of light by the individual layers within a four layer canopy and by the underlying soil; (3) the percent absorption of light by each vegetative canopy layer for variable sun angle; and (4) the cumulative solar energy absorbed by the developing wheat canopy as it progresses from a single layer through its growth stages to a three layer canopy. This calculation was also presented as a function of the leaf area index.

  15. Thermal IR exitance model of a plant canopy

    NASA Technical Reports Server (NTRS)

    Kimes, D. S.; Smith, J. A.; Link, L. E.

    1981-01-01

    A thermal IR exitance model of a plant canopy based on a mathematical abstraction of three horizontal layers of vegetation was developed. Canopy geometry within each layer is quantitatively described by the foliage and branch orientation distributions and number density. Given this geometric information for each layer and the driving meteorological variables, a system of energy budget equations was determined and solved for average layer temperatures. These estimated layer temperatures, together with the angular distributions of radiating elements, were used to calculate the emitted thermal IR radiation as a function of view angle above the canopy. The model was applied to a lodgepole pine (Pinus contorta) canopy over a diurnal cycle. Simulated vs measured radiometric average temperatures of the midcanopy layer corresponded with 2 C. Simulation results suggested that canopy geometry can significantly influence the effective radiant temperature recorded at varying sensor view angles.

  16. Microwave backscattering and emission model for grass canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; Lang, Roger H.; Levine, David M.

    1991-01-01

    A two-layer model is developed that treats the grass canopy as a collection of randomly oriented elliptical dielectric discs over a layer of thatch with underlying soil surface. The distorted Born approximation in conjunction with the Peake formulation is used to calculate the backscattering coefficient and the emissivity from the canopy. Two particular features of this model which are unique for grass canopies are the variation of the canopy structure and the presence of the thatch layer. The basic parameters in the model such as the size and orientation of grass blades, dielectric constant of soil and vegetation, and thickness and water content of the thatch layer have been obtained from ground truth data. To interpret the available experimental observations of grasslands, numerical results from both passive and active models at L-band (1.4 GHz) are generated and various scattering and emission properties of the grass canopies are discussed.

  17. Geological control of canopy structure and function in Panamanian forests as identified by CAO-AToMS

    NASA Astrophysics Data System (ADS)

    Higgins, M.; Asner, G. P.; Martin, R. E.; Knapp, D. E.

    2012-12-01

    Geological formations and their edaphic properties are known to control plant species composition in tropical forests. It has been speculated that these edaphic and compositional patterns might also be translated into functional patterns, but this has been difficult to test due to a lack of broad-scale but detailed canopy structural and functional data. Here we use the Carnegie Airborne Observatory (CAO) Airborne Taxonomic Mapping System (AToMS), which combines a 480-band visible-to-shortwave imaging spectrometer (VSWIR) with dual waveform LiDAR, to generate ultra-high resolution data on geomorphology, canopy structure, and canopy chemistry for forests in the vicinity of the Panama Canal. Using these remotely-sensed data, in conjunction with field data on soils and plant species composition, we demonstrate that geological formations regulate forest structure and chemistry in these forests via changes in soils and plant species composition. These chemical properties, moreover, correspond to canopy functional properties including photosynthetic investment and anti-herbivore defenses. Together, our findings indicate that forest canopy structure and function in these forests are an expression their geological history, over which variations due to contemporary variables such as climate are overlaid.

  18. Efficient retrieval of vegetation leaf area index and canopy clumping factor from satellite data to support pollutant deposition assessments.

    PubMed

    Nikolov, Ned; Zeller, Karl

    2006-06-01

    Canopy leaf area index (LAI) is an important structural parameter of the vegetation controlling pollutant uptake by terrestrial ecosystems. This paper presents a computationally efficient algorithm for retrieval of vegetation LAI and canopy clumping factor from satellite data using observed Simple Ratios (SR) of near-infrared to red reflectance. The method employs numerical inversion of a physics-based analytical canopy radiative transfer model that simulates the bi-directional reflectance distribution function (BRDF). The algorithm is independent of ecosystem type. The method is applied to 1-km resolution AVHRR satellite images to retrieve a geo-referenced data set of monthly LAI values for the conterminous USA. Satellite-based LAI estimates are compared against independent ground LAI measurements over a range of ecosystem types. Verification results suggest that the new algorithm represents a viable approach to LAI retrieval at continental scale, and can facilitate spatially explicit studies of regional pollutant deposition and trace gas exchange.

  19. Wind sheltering of lakes and wetlands: the effect of stability on turbulent canopy wakes and evaporation

    NASA Astrophysics Data System (ADS)

    Markfort, C. D.; Porte-Agel, F.; Stefan, H. G.

    2010-12-01

    Topographic features and heterogeneous vegetation cover of the landscape, as well as atmospheric stability present significant challenges for predicting fluxes of momentum, heat, moisture, and climate-controlling trace gases across land and water surfaces from and into the atmospheric boundary layer (ABL). Changes in landscape roughness and boundary layer separation in the wake of canopies, buildings and large-scale topographic obstructions contribute to these challenges. The particular case of a canopy edge at the shoreline of a lake or wetland is known to significantly reduce momentum transport to the surface of these water bodies, especially if they are of small size. The wind sheltering effect of canopies must be considered to predict surface layer mixing as well as mass transfer at the air-water interface, but few studies have addressed how canopy heterogeneity affects the ABL. Finding ideal field cases, and uncertainty in numerical approaches to high Reynolds number simulation of separated flows within the ABL have been major obstacles. Atmospheric stability can also affect sheltering due to the suppression of turbulence, potentially decreasing surface flux. The effect of atmospheric stability is of particular interest because it poses significant challenges for subgrid-scale models in large-eddy simulations. Wind tunnel experiments provide an ideal environment to simulate a stationary stable boundary layer and test how the ABL adjusts across the transition from a canopy to a lake. We conducted experiments in the St. Anthony Falls Laboratory thermally stratified boundary layer wind tunnel to determine the effects of atmospheric stability on the boundary layer evolution in the wake of a homogeneous (2h x 1v) canopy patch over a smooth flat surface. We applied the findings to investigate the potential effect on wind sheltering of lakes. We compared results from PIV and custom x-wire/cold-wire anemometry for stable and neutral conditions and find marked

  20. Deploying Fourier Coefficients to Unravel Soybean Canopy Diversity

    PubMed Central

    Jubery, Talukder Z.; Shook, Johnathon; Parmley, Kyle; Zhang, Jiaoping; Naik, Hsiang S.; Higgins, Race; Sarkar, Soumik; Singh, Arti; Singh, Asheesh K.; Ganapathysubramanian, Baskar

    2017-01-01

    Soybean canopy outline is an important trait used to understand light interception ability, canopy closure rates, row spacing response, which in turn affects crop growth and yield, and directly impacts weed species germination and emergence. In this manuscript, we utilize a methodology that constructs geometric measures of the soybean canopy outline from digital images of canopies, allowing visualization of the genetic diversity as well as a rigorous quantification of shape parameters. Our choice of data analysis approach is partially dictated by the need to efficiently store and analyze large datasets, especially in the context of planned high-throughput phenotyping experiments to capture time evolution of canopy outline which will produce very large datasets. Using the Elliptical Fourier Transformation (EFT) and Fourier Descriptors (EFD), canopy outlines of 446 soybean plant introduction (PI) lines from 25 different countries exhibiting a wide variety of maturity, seed weight, and stem termination were investigated in a field experiment planted as a randomized complete block design with up to four replications. Canopy outlines were extracted from digital images, and subsequently chain coded, and expanded into a shape spectrum by obtaining the Fourier coefficients/descriptors. These coefficients successfully reconstruct the canopy outline, and were used to measure traditional morphometric traits. Highest phenotypic diversity was observed for roundness, while solidity showed the lowest diversity across all countries. Some PI lines had extraordinary shape diversity in solidity. For interpretation and visualization of the complexity in shape, Principal Component Analysis (PCA) was performed on the EFD. PI lines were grouped in terms of origins, maturity index, seed weight, and stem termination index. No significant pattern or similarity was observed among the groups; although interestingly when genetic marker data was used for the PCA, patterns similar to canopy

  1. Deploying Fourier Coefficients to Unravel Soybean Canopy Diversity.

    PubMed

    Jubery, Talukder Z; Shook, Johnathon; Parmley, Kyle; Zhang, Jiaoping; Naik, Hsiang S; Higgins, Race; Sarkar, Soumik; Singh, Arti; Singh, Asheesh K; Ganapathysubramanian, Baskar

    2016-01-01

    Soybean canopy outline is an important trait used to understand light interception ability, canopy closure rates, row spacing response, which in turn affects crop growth and yield, and directly impacts weed species germination and emergence. In this manuscript, we utilize a methodology that constructs geometric measures of the soybean canopy outline from digital images of canopies, allowing visualization of the genetic diversity as well as a rigorous quantification of shape parameters. Our choice of data analysis approach is partially dictated by the need to efficiently store and analyze large datasets, especially in the context of planned high-throughput phenotyping experiments to capture time evolution of canopy outline which will produce very large datasets. Using the Elliptical Fourier Transformation (EFT) and Fourier Descriptors (EFD), canopy outlines of 446 soybean plant introduction (PI) lines from 25 different countries exhibiting a wide variety of maturity, seed weight, and stem termination were investigated in a field experiment planted as a randomized complete block design with up to four replications. Canopy outlines were extracted from digital images, and subsequently chain coded, and expanded into a shape spectrum by obtaining the Fourier coefficients/descriptors. These coefficients successfully reconstruct the canopy outline, and were used to measure traditional morphometric traits. Highest phenotypic diversity was observed for roundness, while solidity showed the lowest diversity across all countries. Some PI lines had extraordinary shape diversity in solidity. For interpretation and visualization of the complexity in shape, Principal Component Analysis (PCA) was performed on the EFD. PI lines were grouped in terms of origins, maturity index, seed weight, and stem termination index. No significant pattern or similarity was observed among the groups; although interestingly when genetic marker data was used for the PCA, patterns similar to canopy

  2. Impacts of differing aerodynamic resistance formulae on modeled energy exchange at the above-canopy/within-canopy/soil interface

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Application of the Two-Source Energy Balance (TSEB) Model using land surface temperature (LST) requires aerodynamic resistance parameterizations for the flux exchange above the canopy layer, within the canopy air space and at the soil/substrate surface. There are a number of aerodynamic resistance f...

  3. Forest canopy interception loss exceeds wet canopy evaporation in Japanese cypress (Hinoki) and Japanese cedar (Sugi) plantations

    NASA Astrophysics Data System (ADS)

    Saito, Takami; Matsuda, Hiroki; Komatsu, Misako; Xiang, Yang; Takahashi, Atsuhiro; Shinohara, Yoshinori; Otsuki, Kyoichi

    2013-12-01

    Physical process of canopy interception loss remains to be explained.Rainfall partitioning to interception was similar between the stands.The rate of interception increased with rainfall intensity.Observed amount of interception was greater than estimated amount of evaporation.We suggest that splash droplets transport by canopy ventilation is the primary process of interception loss.

  4. A model of plant canopy polarization response

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.

    1980-01-01

    Sensors to remotely measure the linear polarization of ground scenes have been proposed for the Multispectral Resource Sampler (MRS), a satellite sensor system proposed to complement the Thematic Mapper. At present justification for a sensor on MRS to measure scene polarization is limited. This paper discusses a model for the amount of linearly polarized light reflected by the shiny leaves of such crops as wheat, corn, and sorghum. The theory demonstrates that, potentially, measurements of the linearly polarized light from a crop canopy may be used as an additional feature to discriminate between crops. Examination of the model suggests that, potentially, satellite polarization measurements may be used to monitor crop development stage, leaf water content, leaf area index, hail damage, and certain plant diseases. The model adds to the understanding of the potential information content of scene polarization measurements acquired by future satellite sensor systems such as MRS.

  5. Working group on chromospheric fields - Canopies

    NASA Technical Reports Server (NTRS)

    Jones, H. P.

    1985-01-01

    Although there are many points of uncertainty and controversy, the working group on chromospheric fields focussed its discussion on the concept of canopies; i.e., no one disagreed that a central issue relating to magnetic fields and chromospheric models is to learn how the photospheric field spreads with height. However, it quickly became apparent that in the time available, there was little prospect of building new unified models of magnetic field phenomena in the chromosphere beyond the scope of the formal presentations. Thus, the discussion was devoted to formulating questions which seemed both possible to address in future work and important for advancing understanding of the chromosphere. It began by discussing unresolved physical issues (almost everything) and then proceeded to consider means, both observational and synthetic, to address them.

  6. Microwave backscattering from an anisotropic soybean canopy

    NASA Technical Reports Server (NTRS)

    Lang, R. H.; Saatchi, S.; Levine, D. M.

    1986-01-01

    Electromagnetic backscattering from a soybean canopy is modeled in the L band region of the spectrum. Mature soybean plants are taken as an ensemble of leaves and stems which are represented by lossy dielectric disks and rods respectively. Field data indicated that leaves and stems are not distributed uniformly in the azimuth coordinate. The plant has a tendency to grow out into the area between the rows. The effects on backscattered radar waves was computed by the distorted Born approximation. Results for look directions along the rows and perpendicular to the rows show that only a modest difference occurs in the L band frequency range. The use of another nonuniform distribution, different from those observed experimentally, results in a significant effect due to vegetation asymmetry.

  7. Forward Canopy Feasibility and Thru-the-Canopy (TTC) Ejection System Study

    DTIC Science & Technology

    1990-01-01

    Include Area Code) 22c. OFFICE SYMBOL Lt. Tong C. Choe, William R. Pinnell (513) 255-6524 WRDC/FIVR DO FORM 1473,84 MAR 83 APR edition may be used until...configuration. Figure 4 illustrates two configurations for forward and aft arch edge attachment. In each case the structural integrity for bird resistance is...Number 1 utilizes independent initi- ators for ground egress. In some ground egress cases it may be desirable to select either the primary canopy

  8. Trait coordination, mechanical behaviour and growth form plasticity of Amborella trichopoda under variation in canopy openness

    PubMed Central

    Trueba, Santiago; Isnard, Sandrine; Barthélémy, Daniel; Olson, Mark E.

    2016-01-01

    Understanding the distribution of traits across the angiosperm phylogeny helps map the nested hierarchy of features that characterize key nodes. Finding that Amborella is sister to the rest of the angiosperms has raised the question of whether it shares certain key functional trait characteristics, and plastic responses apparently widespread within the angiosperms at large. With this in mind, we test the hypothesis that local canopy openness induces plastic responses. We used this variation in morphological and functional traits to estimate the pervasiveness of trait scaling and leaf and stem economics. We studied the architecture of Amborella and how it varies under different degrees of canopy openness. We analyzed the coordination of 12 leaf and stem structural and functional traits, and the association of this covariation with differing morphologies. The Amborella habit is made up of a series of sympodial modules that vary in size and branching pattern under different canopy openness. Amborella stems vary from self-supporting to semi-scandent. Changes in stem elongation and leaf size in Amborella produce distinct morphologies under different light environments. Correlations were found between most leaf and stem functional traits. Stem tissue rigidity decreased with increasing canopy openness. Despite substantial modulation of leaf size and leaf mass per area by light availability, branches in different light environments had similar leaf area-stem size scaling. The sympodial growth observed in Amborella could point to an angiosperm synapomorphy. Our study provides evidence of intraspecific coordination between leaf and stem economic spectra. Trait variation along these spectra is likely adaptive under different light environments and is consistent with these plastic responses having been present in the angiosperm common ancestor. PMID:27672131

  9. Estimating leaf chlorophyll of barley at different growth stages using spectral indices to reduce soil background and canopy structure effects

    NASA Astrophysics Data System (ADS)

    Yu, Kang; Lenz-Wiedemann, Victoria; Chen, Xinping; Bareth, Georg

    2014-11-01

    for individual growth stages (R2 < 0.59). Accordingly, RRDIs optimized for open and closed canopies improved the estimations of Chl for individual stages before and after canopy closure, respectively, with R2 of 0.65 (p < 0.0001) and 0.78 (p < 0.0001). This study shows that RRDI can efficiently eliminate the effects of structural properties on canopy reflectance response to canopy biochemistry. The results yet are limited to the datasets used in this study; therefore, transferability of the methods to large scales or other datasets should be further evaluated.

  10. A specific PFT and sub-canopy structure for simulating oil palm in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Knohl, A.; Roupsard, O.; Bernoux, M.; LE Maire, G.; Panferov, O.; Kotowska, M.; Meijide, A.

    2015-12-01

    Towards an effort to quantify the effects of rainforests to oil palm conversion on land-atmosphere carbon, water and energy fluxes, a specific plant functional type (PFT) and sub-canopy structure are developed for simulating oil palm within the Community Land Model (CLM4.5). Current global land surface models only simulate annual crops beside natural vegetation. In this study, a multilayer oil palm subroutine is developed in CLM4.5 for simulating oil palm's phenology and carbon and nitrogen allocation. The oil palm has monopodial morphology and sequential phenology of around 40 stacked phytomers, each carrying a large leaf and a fruit bunch, forming a natural multilayer canopy. A sub-canopy phenological and physiological parameterization is thus introduced, so that multiple phytomer components develop simultaneously but according to their different phenological steps (growth, yield and senescence) at different canopy layers. This specific multilayer structure was proved useful for simulating canopy development in terms of leaf area index (LAI) and fruit yield in terms of carbon and nitrogen outputs in Jambi, Sumatra (Fan et al. 2015). The study supports that species-specific traits, such as palm's monopodial morphology and sequential phenology, are necessary representations in terrestrial biosphere models in order to accurately simulate vegetation dynamics and feedbacks to climate. Further, oil palm's multilayer structure allows adding all canopy-level calculations of radiation, photosynthesis, stomatal conductance and respiration, beside phenology, also to the sub-canopy level, so as to eliminate scale mismatch problem among different processes. A series of adaptations are made to the CLM model. Initial results show that the adapted multilayer radiative transfer scheme and the explicit represention of oil palm's canopy structure improve on simulating photosynthesis-light response curve. The explicit photosynthesis and dynamic leaf nitrogen calculations per canopy

  11. Large Eddy Simulations to determine the role of dispersive stresses in the urban canopy layer

    NASA Astrophysics Data System (ADS)

    Christen, Andreas; Giometto, Marco; Parlange, Marc

    2013-04-01

    Urban-scale weather and air pollution forecasting models need to realistically predict conditions in the urban canopy layer (UCL) - the atmosphere in-between buildings where people live and most activities take place. Nevertheless, for performance reasons, forecasting models cannot resolve every detail of the flow field around individual buildings and obstacles in a city. In common urban canopy parameterizations (UCPs), exchange processes between the UCL and the overlying atmosphere - including momentum transfer - are simplified to one-dimensional bulk flow representations, where the time-averaged flow field is also horizontally averaged over a larger spatial subset of the urban canopy. In the spatial averaging process of RANS equations, additional covariance terms arise in the time-averaged momentum balance, called 'dispersive stresses'. Physically, a dispersive stress can be explained as spatial correlation between the mean horizontal flow and mean vertical flow around buildings at a given height layer. Due to lack of knowledge on the role of dispersive fluxes, they are neglected in all current UCPs and transfer formulations. Only limited CFD studies for idealized cubical arrays show that dispersive fluxes are relevant and important to properly describe the overall momentum transfer in those specific rigid canopies. The current contribution determines the role of dispersive stresses to the overall momentum transfer for a more realistic urban canopy by means of large eddy simulation (LES). LES takes into account the unsteadiness that characterizes canopy layer flows, offering indisputably superior performances in predicting momentum exchange with respect to traditional methods, in particular when the effects of canopy elements play a major role. LES also showed to be able to properly represent the flow in areas of strong separation and in wakes, features that are strongly present in urban canopies, where most RANS and URANS models fail due to their under

  12. An evaluation of imaging spectrometry for estimating forest canopy chemistry

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    High spectral resolution Airborne Imaging Spectrometer (AIS) data were acquired over 20 well-studied Wisconsin forest sites to evaluate the potential of remote sensing for estimating forest canopy chemistry. Intensive nutrient cycling research in these forests demonstrates that canopy lignin content is strongly related to measured annual nitrogen mineralization at the undisturbed sites and may serve as an accurate index for nitrogen cycling rates. Ground measurements were made of foliar biomass and canopy nitrogen and lignin content, the latter within two weeks of the AIS overflight. The spectral data were transformed using derivative techniques modified from laboratroy spectroscopy. Stepwise regression assisted in determining combinations of wavelengths most highly correlated with canopy chemistry and biomass. Strong correlations between AIS data and total canopy lignin content in deciduous forests and canopy lignin concentration (total lignin/biomass) in both deciduous and coniferous stands indicate that imaging spectrometry can be used to estimate canopy lignin content and, from that, the spatial distribution of annual nitrogen mineralization rates.

  13. 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.

  14. Forest Canopy Height Estimation from Calipso Lidar Measurement

    NASA Astrophysics Data System (ADS)

    Lu, Xiaomei; Hu, Yongxiang; Lucker, Patricia L.; Trepte, Charles

    2016-06-01

    The canopy height is an important parameter in aboveground biomass estimation. Lidar remote sensing from airborne or satellite platforms, has a unique capability for forestry applications. This study introduces an innovative concept to estimate canopy height using CALIOP two wavelengths lidar measurements. One main advantage is that the concept proposed here is dependent on the penetration depths at two wavelengths without making assumption about the last peak of waveform as the ground location, and it does not require the ancillary Digital Elevation Model (DEM) data in order to obtain the slope information of terrain. Canopy penetration depths at two wavelengths indicate moderately strong relationships for estimating the canopy height. Results show that the CALIOP-derived canopy heights were highly correlated with the ICESat/GLAS-derived values with a mean RMSE of 3.4 m and correlation coefficient (R) of 0.89. Our findings present a relationship between the penetration difference and canopy height, which can be used as another metrics for canopy height estimation, except the full waveforms.

  15. Flow within and above heterogeneous and homogeneous canopies

    NASA Astrophysics Data System (ADS)

    Hamed, Ali M.; Sadowski, Matthew J.; Chamorro, Leonardo P.

    2016-11-01

    The flow development above and within homogeneous and heterogeneous canopies was studied using planar and stereo PIV in a refractive-index-matching open channel. The homogeneous model is constituted of elements of height h arranged in staggered configuration; whereas the heterogeneous canopy consisted of elements of two heights h1 = h + 1/3 h and h2 = h - 1/3 h alternated every two rows. Both canopies had the same roughness density, element geometry, and mean height. The flow was studied under three submergences H/h = 2, 3, 4, where H denotes the flow depth. Turbulence statistics complemented with quadrant analysis and proper orthogonal decomposition reveal richer flow dynamics induced by height heterogeneity. Topography-induced spatially-periodic mean flows are observed for the heterogeneous canopy. In contrast to the homogeneous case, non-vanishing vertical velocity is maintained across the entire length of the heterogeneous canopy with increased levels at lower submergence depths. The results indicate that heterogeneous canopies exhibit greater vertical turbulent exchange at the canopy interface, suggesting a potential for greater scalar exchange and greater impact on channel hydraulic resistance.

  16. Ground-based imaging spectrometry of canopy phenology and chemistry in a deciduous forest

    NASA Astrophysics Data System (ADS)

    Toomey, M. P.; Friedl, M. A.; Frolking, S. E.; Hilker, T.; O'Keefe, J.; Richardson, A. D.

    2013-12-01

    Phenology, annual life cycles of plants and animals, is a dynamic ecosystem attribute and an important feedback to climate change. Vegetation phenology is commonly monitored at canopy to continental scales using ground based digital repeat photography and satellite remote sensing, respectively. Existing systems which provide sufficient temporal resolution for phenological monitoring, however, lack the spectral resolution necessary to investigate the coupling of phenology with canopy chemistry (e.g. chlorophyll, nitrogen, lignin-cellulose content). Some researchers have used narrowband (<10 nm resolution) spectrometers at phenology monitoring sites, yielding new insights into seasonal changes in leaf biochemistry. Such instruments integrate the spectral characteristics of the entire canopy, however, masking considerable variability between species and plant functional types. There is an opportunity, then, for exploring the potential of imaging spectrometers to investigate the coupling of canopy phenology and the leaf biochemistry of individual trees. During the growing season of April-October 2013 we deployed an imaging spectrometer with a spectral range of 371-1042 nm and resolution of ~5 nm (Surface Optics Corporation 710; San Diego, CA) on a 35 m tall tower at the Harvard Forest, Massachusetts. The image resolution was ~0.25 megapixels and the field of view encompassed approximately 20 individual tree crowns at a distance of 20-40 m. The instrument was focused on a mixed hardwoods canopy composed of 4 deciduous tree species and one coniferous tree species. Scanning was performed daily with an acquisition frequency of 30 minutes during daylight hours. Derived imagery were used to calculate a suite of published spectral indices used to estimate foliar content of key pigments: cholorophyll, carotenoids and anthocyanins. Additionally, we calculated the photochemical reflectance index (PRI) as well as the position and slope of the red edge as indicators of mid- to

  17. Aerosol dry deposition on vegetative canopies. Part II: A new modelling approach and applications

    NASA Astrophysics Data System (ADS)

    Petroff, Alexandre; Mailliat, Alain; Amielh, Muriel; Anselmet, Fabien

    2008-05-01

    This paper presents a new approach for the modelling of aerosol dry deposition on vegetation. It follows a companion article, in which a review of the current knowledge highlights the need for a better description of the aerosol behaviour within the canopy [Petroff, A., Mailliat, A., Amielh, M., Anselmet, F., 2008. Aerosol dry deposition on vegetative canopies. Part I: Review of present knowledge. Atmospheric Environment, in press, doi:10.1016/j.atmosenv.2007.09.043]. Concepts from multi-phase flow studies are used for describing the canopy medium and deriving a time and space-averaged aerosol balance equation and the associated deposition terms. The closure of the deposition terms follows an up-scaling procedure based on the statistical distribution of the collecting elements. This aerosol transport model is then applied in a stationary and mono-dimensional configuration and takes into account the properties of the vegetation, the aerosol and the turbulent flow. Deposition mechanisms are Brownian diffusion, interception, inertial and turbulent impactions, and gravitational settling. For each of them, a parameterisation of the particle collection is derived and the quality of their predictions is assessed by comparison with wind-tunnel deposition measurements on coniferous twigs [Belot, Y., Gauthier, D., 1975. Transport of micronic particles from atmosphere to foliar surfaces. In: De Vries, D.A., Afgan, N.H. (Eds.), Heat and Mass Transfer in the Biosphere. Scripta Book, Washington, DC, pp. 583-591; Belot, Y., 1977. Etude de la captation des polluants atmosphériques par les végétaux. CEA, R-4786, Fontenay-aux-Roses; Belot, Y., Camus, H., Gauthier, D., Caput, C., 1994. Uptake of small particles by canopies. The Science of the Total Environment 157, 1-6]. Under a real canopy configuration, the predictions of the aerosol transport model compare reasonably well with detailed on-site deposition measurements of Aitken mode particles [Buzorius, G., Rannik, Ü., M

  18. Specular, diffuse, and polarized light scattered by two wheat canopies

    NASA Technical Reports Server (NTRS)

    Vanderbilt, V. C.; Grant, L.; Biehl, L. L.; Robinson, B. F.

    1985-01-01

    Using polarization measurements, the reflectance factor of two wheat canopies is divided into components due to specularly and diffusely reflected light. The data show that two key angles may be predicted, the angle of the polarizer for minimum flux and the angle of incidence of sunlight specularly reflected by a leaf to a sensor. The results show that specular reflection is a key aspect to radiation transfer by two canopies. Results suggest that the advent of heading in wheat may be remotely sensed from polarization measurements of the canopy reflectance.

  19. Potential Sources of Polarized Light from a Plant Canopy

    NASA Technical Reports Server (NTRS)

    Vanderbilt, Vern; Daughtry, Craig; Dahlgren, Robert

    2016-01-01

    Field measurements have demonstrated that sunlight polarized during a first surface reflection by shiny leaves dominates the optical polarization of the light reflected by shiny-leafed plant canopies having approximately spherical leaf angle probability density functions ("Leaf Angle Distributions" - LAD). Yet for other canopies - specifically those without shiny leaves and/or spherical LADs - potential sources of optically polarized light may not always be obvious. Here we identify possible sources of polarized light within those other canopies and speculate on the ecologically important information polarization measurements of those sources might contain.

  20. Shinnery oak bidirectional reflectance properties and canopy model inversion

    NASA Technical Reports Server (NTRS)

    Deering, Donald W.; Eck, Thomas F.; Grier, Toby

    1992-01-01

    Field measurements are presented, together with the results of a 3D canopy-model inversion for sand shinnery oak community in western Texas. The spectral bidirectional radiance measurements were in three spectral channels encompassing both the complete land surface and sky hemispheres. The changes in canopy reflectance that occur with variations in solar zenith angle and view direction for two seasons of the year were evaluated, and the 3D radiation-interaction model was inverted to estimate the oak leaf area index and canopy density from the reflectance data.

  1. Forest and Shrub Canopy Structure from Multiangle and High Resolution Passive Remote Sensing

    NASA Astrophysics Data System (ADS)

    Chopping, M. J.; Wang, Z.; Bull, M. A.; Duchesne, R.; North, M.

    2015-12-01

    The 3-D structure of forest and shrub canopies can be mapped using diverse technologies, with the most advanced being lidar and interferometric radar. Other approaches include various modes of interpretation of multi-angle imagery, high-resolution stereo photogrammetry, plant identification, delineation, and measurement from high-resolution panchromatic imagery, and image texture metrics. While active remote sensing will revolutionize mapping of canopy structure, there are currently limitations. High precision lidar will remain limited geographically until the launch of NASA's innovative Global Ecosystem Dynamics Investigation to the International Space Station in 2019 but even this mission will not see high latitude boreal forest, taiga, or shrubs in tundra because of the orbit. Radar-based methods must be calibrated using high quality data. Imagery from passive imagers acquired at a range of scales therefore has much value if it can be used to provide structure data at broader geographic and temporal scales. Here we report on canopy mapping at scales from 0.5 m to 250 m using high-resolution panchromatic imagery from satellite imagers and NASA's Multiangle Imaging Spectro-Radiometer (MISR), respectively. MISR-based 250 m aboveground biomass maps for the southwestern U.S. were assessed against the radar-derived North American Carbon Program National Biomass and Carbon Dataset 2000, showing good agreement (R2=0.80, RMSE=31 Mg ha-1 for the validation data set; and 0.76 and 18 Mg ha-1, respectively, for 1013 random points). For Oregon forests the best and worst cases were R2=0.90, RMSE=42 Mg ha-1 and R2=0.78, RMSE=62 Mg ha-1, respectively. For improved validation, the CANAPI algorithm was used to interpret high-resolution panchromatic imagery. In Sierra National forest, California, canopy cover estimates agreed well with those from field inventory (R2=0.92, RMSE=0.03). Height estimates gave R2=0.94 and relative RMSE=0.25 m for the range 3 m - 60 m, vs. lidar

  2. Could the canopy structure of bryophytes serve as an indicator of microbial biodiversity? A test for testate amoebae and microcrustaceans from a subtropical cloud forest in Dominican Republic.

    PubMed

    Acosta-Mercado, D; Cancel-Morales, N; Chinea, J D; Santos-Flores, C J; De Jesús, I Sastre

    2012-07-01

    The mechanisms that ultimately regulate the diversity of microbial eukaryotic communities in bryophyte ecosystems remain a contentious topic in microbial ecology. Although there is robust consensus that abiotic factors, such as water chemistry of the bryophyte and pH, explain a significant proportion of protist and microcrustacean diversity, there is no systematic assessment of the role of bryophyte habitat complexity on such prominent microbial groups. Water-holding capacity is correlated with bryophyte morphology and canopy structure. Similarly, canopy structure explains biodiversity dynamics of the macrobiota suggesting that canopy structure may also be a potential parameter for understanding microbial diversity. Canopy roughness of the dominant bryophyte species within the Bahoruco Cloud Forest, Cachote, Dominican Republic, concomitant with their associated diversity of testate amoebae and microcrustaceans was estimated to determine whether canopy structure could be added to the list of factors explaining microbial biodiversity in bryophytes. We hypothesized that smooth (with high moisture content) canopies will have higher species richness, density, and biomass of testate amoebae and higher richness and density of microcrustaceans than rough (desiccation-prone) canopies. For testate amoebae, we found 83 morphospecies with relative low abundances. Species richness and density differed among bryophytes with different bryophyte canopy structures and based on non-metric multidimensional scaling, canopy roughness explained 25% of the variation in species composition although not as predicted. Acroporium pungens (low roughness, LR) had the lowest species richness (2 ± 0.61 SD per gram dry weight bryophyte), and density (2.1 ± 0.61 SD individual per gram of dry weight bryophyte); whereas Thuidium urceolatum (high roughness) had the highest richness (24 ± 10.82 SD) and density (94 ± 64.30 SD). The fact that the bryophyte with the highest roughness had the highest

  3. Tree-mycorrhizal associations detected remotely from canopy spectral properties.

    PubMed

    Fisher, Joshua B; Sweeney, Sean; Brzostek, Edward R; Evans, Tom P; Johnson, Daniel J; Myers, Jonathan A; Bourg, Norman A; Wolf, Amy T; Howe, Robert W; Phillips, Richard P

    2016-07-01

    A central challenge in global ecology is the identification of key functional processes in ecosystems that scale, but do not require, data for individual species across landscapes. Given that nearly all tree species form symbiotic relationships with one of two types of mycorrhizal fungi - arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi - and that AM- and ECM-dominated forests often have distinct nutrient economies, the detection and mapping of mycorrhizae over large areas could provide valuable insights about fundamental ecosystem processes such as nutrient cycling, species interactions, and overall forest productivity. We explored remotely sensed tree canopy spectral properties to detect underlying mycorrhizal association across a gradient of AM- and ECM-dominated forest plots. Statistical mining of reflectance and reflectance derivatives across moderate/high-resolution Landsat data revealed distinctly unique phenological signals that differentiated AM and ECM associations. This approach was trained and validated against measurements of tree species and mycorrhizal association across ~130 000 trees throughout the temperate United States. We were able to predict 77% of the variation in mycorrhizal association distribution within the forest plots (P < 0.001). The implications for this work move us toward mapping mycorrhizal association globally and advancing our understanding of biogeochemical cycling and other ecosystem processes.

  4. A photosynthesis-based two-leaf canopy stomatal ...

    EPA Pesticide Factsheets

    A coupled photosynthesis-stomatal conductance model with single-layer sunlit and shaded leaf canopy scaling is implemented and evaluated in a diagnostic box model with the Pleim-Xiu land surface model (PX LSM) and ozone deposition model components taken directly from the meteorology and air quality modeling system—WRF/CMAQ (Weather Research and Forecast model and Community Multiscale Air Quality model). The photosynthesis-based model for PX LSM (PX PSN) is evaluated at a FLUXNET site for implementation against different parameterizations and the current PX LSM approach with a simple Jarvis function (PX Jarvis). Latent heat flux (LH) from PX PSN is further evaluated at five FLUXNET sites with different vegetation types and landscape characteristics. Simulated ozone deposition and flux from PX PSN are evaluated at one of the sites with ozone flux measurements. Overall, the PX PSN simulates LH as well as the PX Jarvis approach. The PX PSN, however, shows distinct advantages over the PX Jarvis approach for grassland that likely result from its treatment of C3 and C4 plants for CO2 assimilation. Simulations using Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) rather than LAI measured at each site assess how the model would perform with grid averaged data used in WRF/CMAQ. MODIS LAI estimates degrade model performance at all sites but one site having exceptionally old and tall trees. Ozone deposition velocity and ozone flux along with LH

  5. Measuring turbulent gust impressions in a forested canopy

    NASA Astrophysics Data System (ADS)

    Hiscox, A.; Ertell, K.

    2014-12-01

    The temporal and spatial characteristics of tree-sway motions and their aerodynamic interactions with coherent turbulence wind fields in a forest (Howland Forest, ME) are examined. Year round measurements of turbulence where taken at heights, above, below, and in the live crown. Additionally measurements of tree bole motion were taken simultaneously for 150 trees surrounding the main meteorological tower. To identify the gust impressions and further understand the timing, spacing and intensity of momentum flux, a a multi-resolution decomposition (MRD) technique was used to find the dominant eddy size. Fourier analysis was applied to each tree for the corresponding time and changes in dominant tree frequency were mapped over time. Results indicate that the most coherency in stand-scale motion occurs when frequency changes are mapped at the same time resolution of the dominant eddy size. Through a mapping-displacement comparison, the sub-mesoscale motions of a canopy atmosphere and their effect on the tree's movement as well as fluxes of energy will be better understood.

  6. High-resolution tree canopy mapping for New York City using LIDAR and object-based image analysis

    NASA Astrophysics Data System (ADS)

    MacFaden, Sean W.; O'Neil-Dunne, Jarlath P. M.; Royar, Anna R.; Lu, Jacqueline W. T.; Rundle, Andrew G.

    2012-01-01

    Urban tree canopy is widely believed to have myriad environmental, social, and human-health benefits, but a lack of precise canopy estimates has hindered quantification of these benefits in many municipalities. This problem was addressed for New York City using object-based image analysis (OBIA) to develop a comprehensive land-cover map, including tree canopy to the scale of individual trees. Mapping was performed using a rule-based expert system that relied primarily on high-resolution LIDAR, specifically its capacity for evaluating the height and texture of aboveground features. Multispectral imagery was also used, but shadowing and varying temporal conditions limited its utility. Contextual analysis was a key part of classification, distinguishing trees according to their physical and spectral properties as well as their relationships to adjacent, nonvegetated features. The automated product was extensively reviewed and edited via manual interpretation, and overall per-pixel accuracy of the final map was 96%. Although manual editing had only a marginal effect on accuracy despite requiring a majority of project effort, it maximized aesthetic quality and ensured the capture of small, isolated trees. Converting high-resolution LIDAR and imagery into usable information is a nontrivial exercise, requiring significant processing time and labor, but an expert system-based combination of OBIA and manual review was an effective method for fine-scale canopy mapping in a complex urban environment.

  7. Spatial Variability of Canopy Structure and Function in Tussock Tundra of Alaska

    NASA Astrophysics Data System (ADS)

    Ryu, Y.; Lee, J.; Kim, J. M.; Lee, Y. K.

    2015-12-01

    Understanding the type of canopy structure and function is important to link the effects of climate change on carbon, water, and energy exchanges between vegetation in tussock tundra and the atmosphere. Interpreting vegetation spatial variability with satellite products alone is a challenge, due to the patchiness of vegetation in the Arctic ecosystems with transient cloud over during the summer season that obstructs retrieval of land surface images. To compare and correlate spatial variation of vegetation with satellite data, we collected leaf area index (LAI) and hyperspectral reflectance data in Council, Alaska. To better understand canopy structure and functional variables, we further examined arctic leaf traits by measuring C:N ratio, leaf mass area (LMA), chlorophyll content, and hyperspectral leaf optical properties. We obtained WorldView-2 Satellite data, which has 8 multispectral bands with 0.5 m resolution, centered on our study site. Preliminary results showed remarkable variation in spectral reflectance and LAI across three 100-m transects. We discuss how to upscale the information from in-situ observed canopy properties into a landscape scale in tandem with the high-resolution satellite image.

  8. Diagnosing Model Errors in Canopy-Atmosphere Exchange Using Empirical Orthogonal Functions

    NASA Astrophysics Data System (ADS)

    Drewry, D.; Albertson, J.

    2004-12-01

    Multi-layer canopy process models (MLCPMs) have been established as tools for estimating local-scale canopy-atmosphere scalar (carbon dioxide, heat and water vapor) exchange as well as testing hypotheses regarding the mechanistic functioning of complex vegetated land surfaces and the interactions between vegetation and the local microenvironment. These model frameworks are composed of a coupled set of component submodels relating radiation attenuation and absorption, photosynthesis, turbulent mixing, stomatal conductance, surface energy balance and soil and subsurface processes. Submodel formulations have been validated for a variety of ecosystems under varying environmental conditions. However, each submodel component requires parameter values that are known to vary seasonally as canopy structure changes, and over shorter periods characterized by shifts in the environmental regime. The temporal dependence of submodel parameters limits application of MLCPMs to short-term integrations for which a specific parameterization can be trusted. We present a novel application of empirical orthogonal function (EOF) analysis to the identification of the primary source of MLCPM error. Carbon dioxide (CO2) concentration profiles, a commonly collected and underutilized data source, are the observed quantity in this analysis. The technique relies on an ensemble of model runs transformed to EOF space to determine the characteristic patterns of model error associated with specific submodel parameters. These patterns provide a basis onto which error residual (modeled - measured) CO2 concentration profiles can be projected to identify the primary source of model error. Synthetic tests and application to field data collected at Duke Forest (North Carolina, USA) are presented.

  9. Spatial and phylogenetic variation in plant defense in a tropical moist forest canopy community

    NASA Astrophysics Data System (ADS)

    McManus, K. M.; Asner, G. P.; Martin, R.

    2013-12-01

    Plants employ physical and chemical defenses to mitigate damage caused by herbivory. Spatial patterns of plant defense may provide insight into the role of plant-herbivore interactions in the assembly of plant communities. Within plant communities, the spatial overdispersion of anti-herbivore defenses by individuals may reflect a strategy to avoid host shifts from herbivore assemblages of neighboring plants. However, variation in plant defense may also result from trade-offs between foliar investment into defense and growth, mediated by variations in abiotic nutrient availability, or constrained by phylogeny. We measured four defensive traits (leaf toughness, total phenols, condensed tannins, and hydrolysable tannins) and three growth traits (LMA, C:N, total protein) of outer canopy foliage for 345 canopy trees representing 78 species, 65 genera, and 34 families in a moist tropical rainforest on Barro Colorado Island, Panama. The outer canopy provides an important, but rarely evaluated, cross-sectional image of the tropical forest ecosystem, and observations at this scale may provide an important link between field and remote sensing based studies. We used existing data on edaphic and geological properties to investigate the relationships of abiotic nutrient variation on variation in defense. Using regression and nested random-effects variance modeling, we found strong phylogenetic association with defensive traits at the family and species level, and little evidence for a trade-off between defensive traits. Greater understanding of phylogenetic structure in trait variation may yield improved characterizations of tropical biodiversity, from functional traits to risk assessments.

  10. Ecohydrological responses of dense canopies to environmental variability: 2. Role of acclimation under elevated CO2

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Kumar, P.; Long, S.; Bernacchi, C.; Liang, X.-Z.; Sivapalan, M.

    2010-12-01

    The ability to accurately predict land-atmosphere exchange of mass, energy, and momentum over the coming century requires the consideration of plant biochemical, ecophysiological, and structural acclimation to modifications of the ambient environment. Amongst the most important environmental changes experienced by terrestrial vegetation over the last century has been the increase in ambient carbon dioxide (CO2) concentrations, with a projected doubling in CO2 from preindustrial levels by the middle of this century. This change in atmospheric composition has been demonstrated to significantly alter a variety of leaf and plant properties across a range of species, with the potential to modify land-atmosphere interactions and their associated feedbacks. Free Air Carbon Enrichment (FACE) technology has provided significant insight into the functioning of vegetation in natural conditions under elevated CO2, but remains limited in its ability to quantify the exchange of CO2, water vapor, and energy at the canopy scale. This paper addresses the roles of ecophysiological, biochemical, and structural plant acclimation on canopy-scale exchange of CO2, water vapor, and energy through the application of a multilayer canopy-root-soil model (MLCan) capable of resolving changes induced by elevated CO2 through the canopy and soil systems. Previous validation of MLCan flux estimates were made for soybean and maize in the companion paper using a record of six growing seasons of eddy covariance data from the Bondville Ameriflux site. Observations of leaf-level photosynthesis, stomatal conductance, and surface temperature collected at the SoyFACE experimental facility in central Illinois provide a basis for examining the ability of MLCan to capture vegetation responses to an enriched CO2 environment. Simulations of control (370 [ppm]) and elevated (550 [ppm]) CO2 environments allow for an examination of the vertical variation and canopy-scale responses of vegetation states and fluxes

  11. 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

  12. Development of a multispectral sensor for crop canopy temperature measurement

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantifying spatial and temporal variability in plant stress has precision agriculture applications in controlling variable rate irrigation and variable rate nutrient application. One approach to plant stress detection is crop canopy temperature measurement by the use of thermographic or radiometric...

  13. 11. Detail of front of building and inspection canopy. View ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. Detail of front of building and inspection canopy. View to north. - U.S. Customs Service Port of Roosville, Main Port Building, U.S. Highway 93, immediately south of U.S.-Canadian border, Eureka, Lincoln County, MT

  14. Detail of metal canopy on south elevation of loading dock, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of metal canopy on south elevation of loading dock, looking west toward two story section of Railway Express Building - Southern Pacific Railroad Depot, Railroad Terminal Post Office & Express Building, Fifth & I Streets, Sacramento, Sacramento County, CA

  15. Detail of metal canopy on north elevation of loading dock, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of metal canopy on north elevation of loading dock, looking west - Southern Pacific Railroad Depot, Railroad Terminal Post Office & Express Building, Fifth & I Streets, Sacramento, Sacramento County, CA

  16. 12. VIEW OF CANOPY OVER NORTHWEST LOADING PLATFORM, RUNNING NEARLY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. VIEW OF CANOPY OVER NORTHWEST LOADING PLATFORM, RUNNING NEARLY THE ENTIRE LENGTH OF THE BUILDING - Oakland Army Base, Transit Shed, East of Dunkirk Street & South of Burma Road, Oakland, Alameda County, CA

  17. North view; Canopy detail and platformlevel freight elevator North ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    North view; Canopy detail and platform-level freight elevator - North Philadelphia Station, 2900 North Broad Street, on northwest corner of Broad Street & Glenwood Avenue, Philadelphia, Philadelphia County, PA

  18. View of American Railway Express Building, facing east. Metal Canopy ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of American Railway Express Building, facing east. Metal Canopy projects above roll-up doors and elevated dock - Southern Pacific Railroad Depot, Railroad Terminal Post Office & Express Building, Fifth & I Streets, Sacramento, Sacramento County, CA

  19. BOREAS TE-18 GeoSail Canopy Reflectance Model

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Huemmrich, K. Fred

    2000-01-01

    The SAIL (Scattering from Arbitrarily Inclined Leaves) model was combined with the Jasinski geo metric model to simulate canopy spectral reflectance and absorption of photosynthetically active radiation for discontinuous canopies. This model is called the GeoSail model. Tree shapes are described by cylinders or cones distributed over a plane. Spectral reflectance and transmittance of trees are calculated from the SAIL model to determine the reflectance of the three components used in the geometric model: illuminated canopy, illuminated background, shadowed canopy, and shadowed background. The model code is Fortran. sample input and output data are provided in ASCII text files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  20. Detail of metal canopy on west elevation of Railway Express ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Detail of metal canopy on west elevation of Railway Express Building, facing east - Southern Pacific Railroad Depot, Railroad Terminal Post Office & Express Building, Fifth & I Streets, Sacramento, Sacramento County, CA

  1. 18. DETAIL OF ROLLING DOORS AND CANOPY AT SOUTH SIDE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. DETAIL OF ROLLING DOORS AND CANOPY AT SOUTH SIDE ENTRANCE, ALSO SEEN FROM A DISTANCE IN VIEW NO. CA-295-A-15. - United Engineering Company Shipyard, Inspection & Repair Shops, 2900 Main Street, Alameda, Alameda County, CA

  2. F-16 Through-Canopy Crew Egress From Fighter Aircraft

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A proposed method for pilots to eject from aircraft, in which the canopy fractures from an embedded explosive cord and then opens in a French-door pattern. Takes approximately half the time as current methods.

  3. East view general left to right; Platform, trackage, canopies, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    East view - general left to right; Platform, trackage, canopies, and roof of Station Building at right - North Philadelphia Station, 2900 North Broad Street, on northwest corner of Broad Street & Glenwood Avenue, Philadelphia, Philadelphia County, PA

  4. 13. DETAIL VIEW OF LOADING DOCK CANOPY, SHOWING TWIN TIMBER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. DETAIL VIEW OF LOADING DOCK CANOPY, SHOWING TWIN TIMBER SUPPORT MEMBERS AND SUSPENDER BAR MOUNTING HARDWARE - Oakland Army Base, Transit Shed, East of Dunkirk Street & South of Burma Road, Oakland, Alameda County, CA

  5. Are leaf chemistry signatures preserved at the canopy level?

    SciTech Connect

    Borel, C.C.; Gerstl, S.A.W.

    1994-05-01

    Imaging spectrometers have the potential to be very useful in remote sensing of canopy chemistry constituents such as nitrogen and lignin. In this study under the HIRIS project the question of how leaf chemical composition which is reflected in leaf spectral features in the reflectance and transmittance is affected by canopy architecture was investigated. Several plants were modeled with high fidelity and a radiosity model was used to compute the canopy spectral signature over the visible and near infrared. We found that chemical constituent specific signatures such as absorptions are preserved and in the case of low absorption are actually enhanced. For moderately dense canopies the amount of a constituent depends also on the total leaf area.

  6. [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.

  7. Canopy effects droplet size distribution and meteorological change.

    PubMed

    Barber, Jane A S; Greer, Mike; Latham, Mark; Stout, Gail

    2008-03-01

    Wind speed fluctuations measured via a 3-dimensional sonic anemometer recording at 10 Hz returned detailed information both above and within the canopy. The information returned facilitated detailed descriptions of atmospheric energy. In short, large energetic motions equal spray transfer into the target zone, the plant canopy. Data are presented on the physical and biological characterization of spray flux. When nontarget mortality was high the conditions were stable, and large volumes of pesticide descended via aircraft vortices and sedimentation. On the neutral night where there was turbulence in the atmosphere a large proportion of the spray was transported from the target, by winds at altitude. Therefore nontarget mortality and the overall volume entering the canopy were low. That chemical, however, which did enter the canopy was well mixed and transported horizontally as opposed to the more vertical sedimentation on the stable night creating more consistent control.

  8. Estimating sources, sinks and fluxes of reactive atmospheric compounds within a forest canopy

    NASA Astrophysics Data System (ADS)

    Ghannam, K.; Duman, T.; Walker, J. T.; Bash, J. O.; Huang, C. W.; Khlystov, A.; Katul, G. G.

    2015-12-01

    While few dispute the significance of within-canopy sources or sinks of reactive gaseous and particulate compounds, their estimation continues to be the subject of active research and debate. Reactive species undergo turbulent dispersion within an inhomogeneous flow field, and may be subjected to chemical, biological and/or physical deposition, emissions or transformations on leaves, woody elements, and the forest floor. This system involves chemical reactions and biological processes with multiple time scales and represents the terrestrial ecosystem's exposure to nutrient and acid deposition and atmospheric oxidants. The quantification of these processes is a first step in better understanding the ecological impact of air pollution and feedback to atmospheric composition. Hence, it follows that direct measurements of sources or sinks is difficult to conduct in the presence of all these processes. However, mean scalar concentration profiles measured within the canopy can be used to infer the profile distribution of effective sinks and sources if the flow field is known. This is commonly referred to as the 'inverse problem'. In-canopy and above-canopy multi-level concentration measurements of reactive nitrogen compounds (ammonia, nitric acid, nitrous acid), as well as other compounds that are highly reactive to ammonia and its secondary products (hydrochloric acid and sulfur dioxide), are presented within a deciduous second-growth 180 year old oak-hickory forest situated within the Southeastern U.S. Two different approaches are used to solve for the source-sink distribution from the measured mean scalar concentration profiles: (1) an Eulerian high-order closure model that solves the scalar flux budget equation and (2) a new Lagrangian stochastic model that estimates the dispersion matrix. As each of these methods is subject to different assumptions, the combination of the two can be used to constrain the solution to the inverse problem and permit inference on the

  9. Plant physiological and environmental controls over the exchange of acetaldehyde between forest canopies and the atmosphere

    NASA Astrophysics Data System (ADS)

    Jardine, K.; Harley, P.; Karl, T.; Guenther, A.; Lerdau, M.; Mak, J. E.

    2008-11-01

    We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated throughout the canopies. Net ecosystem emission rates were inversely related to foliar density due to the extinction of light in the canopy and a respective decrease of the acetaldehyde compensation point. This is supported by branch level studies revealing much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex) implying a higher light/temperature sensitivity for acetaldehyde production relative to consumption. The view of stomata as the major pathway for acetaldehyde exchange is supported by strong linear correlations between branch transpiration rates and acetaldehyde exchange velocities for both species. In addition, natural abundance carbon isotope analysis of gas-phase acetaldehyde during poplar branch fumigation experiments revealed a significant kinetic isotope effect of 5.1±0.3‰ associated with the uptake of acetaldehyde. Similar experiments with dry dead poplar leaves showed no fractionation or uptake of acetaldehyde, confirming that this is only a property of living leaves. We suggest that acetaldehyde belongs to a potentially large list of plant metabolites where stomatal resistance can exert long term control over both emission and uptake rates due to the presence of both source(s) and sink(s) within the leaf which strongly buffer large changes in concentrations in the substomatal airspace due to changes in stomatal resistance. We conclude that the exchange of acetaldehyde between plant canopies and the atmosphere is fundamentally controlled by ambient acetaldehyde concentrations, stomatal resistance, and the compensation point which is a function of light/temperature.

  10. Plant physiological and environmental controls over the exchange of acetaldehyde between forest canopies and the atmosphere

    NASA Astrophysics Data System (ADS)

    Jardine, K.; Harley, P.; Karl, T.; Guenther, A.; Lerdau, M.; Mak, J. E.

    2008-06-01

    We quantified fine scale sources and sinks of gas phase acetaldehyde in two forested ecosystems in the US. During the daytime, the upper canopy behaved as a net source while at lower heights, reduced emission rates or net uptake were observed. At night, uptake generally predominated thoughout the canopies. Net ecosystem emission rates were inversely related to foliar density which influenced the extinction of light and the acetaldehyde compensation point in the canopy. This is supported by branch level studies revealing much higher compensation points in the light than in the dark for poplar (Populus deltoides) and holly oak (Quercus ilex) implying a higher light/temperature sensitivity for acetaldehyde production relative to consumption. The view of stomata as the major pathway for acetaldehyde exchange is supported by strong linear correlations between branch transpiration rates and acetaldehyde exchange velocities for both species. In addition, natural abundance carbon isotope analysis of gas-phase acetaldehyde during poplar branch fumigation experiments revealed a significant kinetic isotope effect of 5.1±0.3‰, associated with the uptake of acetaldehyde. Similar experiments with dry dead poplar leaves showed no fractionation or uptake of acetaldehyde, confirming that this is only a property of living leaves. We suggest that acetaldehyde belongs to a potentially large list of plant metabolites where stomatal conductance can exert long term control over both emission and uptake rates due to the presence of both source(s) and sink(s) within the leaf which strongly buffer large changes in concentrations in the substomatal airspace due to changes in stomatal conductance. We conclude that the exchange of acetaldehyde between plant canopies and the atmosphere is fundamentally controlled by ambient acetaldehyde concentrations, stomatal conductance, and the acetaldehyde compensation point.

  11. Large-Eddy Simulation of Coherent Flow Structures within a Cubical Canopy

    NASA Astrophysics Data System (ADS)

    Inagaki, Atsushi; Castillo, Marieta Cristina L.; Yamashita, Yoshimi; Kanda, Manabu; Takimoto, Hiroshi

    2012-02-01

    Instantaneous flow structures "within" a cubical canopy are investigated via large-eddy simulation. The main topics of interest are, (1) large-scale coherent flow structures within a cubical canopy, (2) how the structures are coupled with the turbulent organized structures (TOS) above them, and (3) the classification and quantification of representative instantaneous flow patterns within a street canyon in relation to the coherent structures. We use a large numerical domain (2,560 m × 2,560 m × 1,710 m) with a fine spatial resolution (2.5 m), thereby simulating a complete daytime atmospheric boundary layer (ABL), as well as explicitly resolving a regular array of cubes (40 m in height) at the surface. A typical urban ABL is numerically modelled. In this situation, the constant heat supply from roof and floor surfaces sustains a convective mixed layer as a whole, but strong wind shear near the canopy top maintains the surface layer nearly neutral. The results reveal large coherent structures in both the velocity and temperature fields "within" the canopy layer. These structures are much larger than the cubes, and their shapes and locations are shown to be closely related to the TOS above them. We classify the instantaneous flow patterns in a cavity, specifically focusing on two characteristic flow patterns: flushing and cavity-eddy events. Flushing indicates a strong upward motion, while a cavity eddy is characterized by a dominant vortical motion within a single cavity. Flushing is clearly correlated with the TOS above, occurring frequently beneath low-momentum streaks. The instantaneous momentum and heat transport within and above a cavity due to flushing and cavity-eddy events are also quantified.

  12. Maximum Entropy Production Modeling of Evapotranspiration Partitioning on Heterogeneous Terrain and Canopy Cover: advantages and limitations.

    NASA Astrophysics Data System (ADS)

    Gutierrez-Jurado, H. A.; Guan, H.; Wang, J.; Wang, H.; Bras, R. L.; Simmons, C. T.

    2015-12-01

    Quantification of evapotranspiration (ET) and its partition over regions of heterogeneous topography and canopy poses a challenge using traditional approaches. In this study, we report the results of a novel field experiment design guided by the Maximum Entropy Production model of ET (MEP-ET), formulated for estimating evaporation and transpiration from homogeneous soil and canopy. A catchment with complex terrain and patchy vegetation in South Australia was instrumented to measure temperature, humidity and net radiation at soil and canopy surfaces. Performance of the MEP-ET model to quantify transpiration and soil evaporation was evaluated during wet and dry conditions with independently and directly measured transpiration from sapflow and soil evaporation using the Bowen Ratio Energy Balance (BREB). MEP-ET transpiration shows remarkable agreement with that obtained through sapflow measurements during wet conditions, but consistently overestimates the flux during dry periods. However, an additional term introduced to the original MEP-ET model accounting for higher stomatal regulation during dry spells, based on differences between leaf and air vapor pressure deficits and temperatures, significantly improves the model performance. On the other hand, MEP-ET soil evaporation is in good agreement with that from BREB regardless of moisture conditions. The experimental design allows a plot and tree scale quantification of evaporation and transpiration respectively. This study confirms for the first time that the MEP-ET originally developed for homogeneous open bare soil and closed canopy can be used for modeling ET over heterogeneous land surfaces. Furthermore, we show that with the addition of an empirical function simulating the plants ability to regulate transpiration, and based on the same measurements of temperature and humidity, the method can produce reliable estimates of ET during both wet and dry conditions without compromising its parsimony.

  13. [Satellite remote sensing retrieval of canopy nitrogen nutritional status of apple trees at blossom stage].

    PubMed

    Wang, Ling; Zhao, Geng-Xing; Zhu, Xi-Cun; Wang, Rui-Yan; Chang, Chun-Yan

    2013-10-01

    Taking Qixia City of Shandong, China as the study area, and based on the Landsat-5 TM and ALOS AVNIR-2 images, the canopy retrieval reflectance of apple trees at blossom stage was acquired. In combining with the measured reflectance of sample trees, the nitrogen-sensitive spectral indices were constructed and selected. By using the sensitive spectral indices as the independent variables, the nitrogen retrieval models were established, and the model with the best accuracy was used for spatial retrieve. The correlations between the spectral indices and the nitrogen nutritional status were in the order of canopy > leaf > flower. The sensitive indices were mainly composed of green, red, and near infrared bands. The accuracy of the retrieval models was in the order of support vector regression > multi-variable stepwise regression > one-variable regression. The retrieval results based on different images were similar, and showed that the leaf nitrogen content was mainly of grades 3-4 (27-33 g x kg(-1)), and the canopy nitrogen nutrient indices were mainly of grades 2-4 (TM: 38-47 g x kg(-1); ALOS: 32-41 g x kg(-1)). The spatial distribution of the retrieval nitrogen nutritional status based on different images also showed the similar trend, i. e., the nitrogen nutritional status was higher in the north and south than that in the middle part of the study area, and the areas with the high grades of leaf nitrogen and canopy nitrogen were mainly located in Sujiadian Town and Songshan subdistrict in the northwest, Zangjiazhuang Town and Tingkou Town in the northeast, and Shewopo Town in the south, which were consistent with the distribution of the key towns for apple production in Qixia City. This study provided a feasible method for the acquisition of nitrogen nutritional status of apple trees on macroscopic scale, and also, provided reference for other similar remote sensing retrievals.

  14. Throughfall and its spatial variability beneath xerophytic shrub canopies within water-limited arid desert ecosystems

    NASA Astrophysics Data System (ADS)

    Zhang, Ya-feng; Wang, Xin-ping; Hu, Rui; Pan, Yan-xia

    2016-08-01

    Throughfall is known to be a critical component of the hydrological and biogeochemical cycles of forested ecosystems with inherently temporal and spatial variability. Yet little is understood concerning the throughfall variability of shrubs and the associated controlling factors in arid desert ecosystems. Here we systematically investigated the variability of throughfall of two morphological distinct xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) within a re-vegetated arid desert ecosystem, and evaluated the effects of shrub structure and rainfall characteristics on throughfall based on heavily gauged throughfall measurements at the event scale. We found that morphological differences were not sufficient to generate significant difference (P < 0.05) in throughfall between two studied shrub species under the same rainfall and meteorological conditions in our study area, with a throughfall percentage of 69.7% for C. korshinskii and 64.3% for A. ordosica. We also observed a highly variable patchy pattern of throughfall beneath individual shrub canopies, but the spatial patterns appeared to be stable among rainfall events based on time stability analysis. Throughfall linearly increased with the increasing distance from the shrub base for both shrubs, and radial direction beneath shrub canopies had a pronounced impact on throughfall. Throughfall variability, expressed as the coefficient of variation (CV) of throughfall, tended to decline with the increase in rainfall amount, intensity and duration, and stabilized passing a certain threshold. Our findings highlight the great variability of throughfall beneath the canopies of xerophytic shrubs and the time stability of throughfall pattern among rainfall events. The spatially heterogeneous and temporally stable throughfall is expected to generate a dynamic patchy distribution of soil moisture beneath shrub canopies within arid desert ecosystems.

  15. Leaf Aging of Amazonian Canopy Trees: Insights to Tropical Ecological Processes and Satellited Detected Canopy Dynamics

    NASA Astrophysics Data System (ADS)

    Chavana-Bryant, C.; Malhi, Y.; Gerard, F.

    2015-12-01

    Leaf aging is a fundamental driver of changes in leaf traits, thereby, regulating ecosystem processes and remotely-sensed canopy dynamics. Leaf age is particularly important for carbon-rich tropical evergreen forests, as leaf demography (leaf age distribution) has been proposed as a major driver of seasonal productivity in these forests. We explore leaf reflectance as a tool to monitor leaf age and develop a novel spectra-based (PLSR) model to predict age using data from a phenological study of 1,072 leaves from 12 lowland Amazonian canopy tree species in southern Peru. Our results demonstrate monotonic decreases in LWC and Pmass and increase in LMA with age across species; Nmass and Cmassshowed monotonic but species-specific age responses. Spectrally, we observed large age-related variation across species, with the most age-sensitive spectral domains found to be: green peak (550nm), red edge (680-750 nm), NIR (700-850 nm), and around the main water absorption features (~1450 and ~1940 nm). A spectra-based model was more accurate in predicting leaf age (R2= 0.86; %RMSE= 33) compared to trait-based models using single (R2=0.07 to 0.73; %RMSE=7 to 38) and multiple predictors (step-wise analysis; R2=0.76; %RMSE=28). Spectral and trait-based models established a physiochemical basis for the spectral age model. The relative importance of the traits modifying the leaf spectra of aging leaves was: LWC>LMA>Nmass>Pmass,&Cmass. Vegetation indices (VIs), including NDVI, EVI2, NDWI and PRI were all age-dependent. This study highlights the importance of leaf age as a mediator of leaf traits, provides evidence of age-related leaf reflectance changes that have important impacts on VIs used to monitor canopy dynamics and productivity, and proposes a new approach to predicting and monitoring leaf age with important implications for remote sensing.

  16. Flow past 2-D Hemispherical Rigid Canopies

    NASA Astrophysics Data System (ADS)

    Carnasciali, Maria-Isabel

    2013-11-01

    The flow past a 2-dimensional rigid hemispherical shape is investigated using PIV. Flow field measurements and images were generated with the use of a Thermoflow® apparatus. Results of this study are compared to prior work (APS DFD 2012 Session E9.00003) which employed CFD to investigate the flow in the near wake of hemispherical parachutes. The various sized gaps/open areas were positioned at distinct locations. The work presented here is part of a larger research project to investigate flow fields in deceleration devices and parachutes. Understanding the pitch-stability of parachutes is essential for accurate design and implementation of these deceleration devices but they present a difficult system to analyze. The flexibility of the parachute fabric results in large variations in the parachute geometry leading to complex fluid-structure interactions. Such flow, combined with flow through gaps and open areas, has been postulated to shed alternating vortices causing pitching/oscillations of the canopy. The results presented provide some insight into which geometric features affect vortex shedding and may enable the redesign of the baseline parachute to minimize instabilities.

  17. The Golden Canopies (Infant Radiant Warmer)

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The cradle warmer is based on technology in heated transparent materials developed by Sierracin Corporation, Sylmar, California he original application was in heated faceplates for the pressure suit heated faceplates worn by pilots of an Air Force/NASA reconnaissance and weather research plane. Later, Sierracin advanced the technology for other applications, among them the cockpit windows of the NASA X-15 supersonic research vehicle and the helmet faceplates of Apollo astronauts. Adapting the technology to hospital needs, Sierracin teamed with Cavitron Corporation, Anaheim, California, which produces the cradle warmer and two other systems employing Sierracin's electrically-heated transparencies. Working to combat the infant mortality rate, hospitals are continually upgrading delivery room and nursery care techniques. Many have special procedures and equipment to protect infants during the "period of apprehension," the critical six to 12 hours after delivery. One such item of equipment is an aerospace spinoff called the Infant Radiant Warmer, a "golden canopy" which provides uniform, controlled warmth to the infant's cradle. Warmth is vitally important to all newborns, particularly premature babies; they lose heat more rapidly than adults because they have greater surface area in comparison with body mass.

  18. Development of the F-22 Canopy Container, CNU-692/E

    DTIC Science & Technology

    2008-02-27

    E is a sealed , welded aluminum, controlled breathing, reusable container (Appendix 2, Figure 1). The container is engineered for the physical and...Engineer susan.evans@us.af.mil DSN 787-7445 Comm (937) 257-7445 Development of the F-22 Canopy Container, CNU-692/E AFMC LSO/LOP...AIR FORCE PACKAGING TECHNOLOGY & ENGINEERING FACILITY WRIGHT PATTERSON AFB, OH 45433-5540 27 February 2008 AFPTEF Report No. 08-R-03 F-22 Canopy C

  19. Constraining canopy biophysical simulations with MODIS reflectance data

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Duveiller, G.

    2013-05-01

    Modern vegetation models incorporate ecophysiological details that allow for accurate estimates of carbon dioxide uptake, water use and energy exchange, but require knowledge of dynamic structural and biochemical traits. Variations in these traits are controlled by genetic factors as well as growth stage and nutrient and moisture availability, making them difficult to predict and prone to significant error. Here we explore the use of MODIS optical reflectance data for constraining key canopy- and leaf-level traits required by forward biophysical models. A multi-objective optimization algorithm is used to invert the PROSAIL canopy radiation transfer model, which accounts for the effects of leaf-level optical properties, foliage distribution and orientation on canopy reflectance across the optical range. Inversions are conducted for several growing seasons for both soybean and maize at several sites in the Central US agro-ecosystem. These inversions provide estimates of seasonal variations, and associated uncertainty, of variables such as leaf area index (LAI) that are then used as inputs into the MLCan biophysical model to conduct forward simulations. MLCan characterizes the ecophysiological functioning of a plant canopy at a half-hourly timestep, and has been rigorously validated for both C3 and C4 crops against observations of canopy CO2 uptake, evapotranspiration and sensible heat exchange across a wide range of meteorological conditions. The inversion-derived canopy properties are used to examine the ability of MODIS data to characterize seasonal variations in canopy properties in the context of a detailed forward canopy biophysical model, and the uncertainty induced in forward model estimates as a function of the uncertainty in the inverted parameters. Special care is made to ensure that the satellite observations match adequately, in both time and space, with the coupled model simulations. To do so, daily MODIS observations are used and a validated model of

  20. An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies

    PubMed Central

    Zhou, Xijia; Liu, Zhigang; Xu, Shan; Zhang, Weiwei; Wu, Jun

    2016-01-01

    Detecting sun-induced chlorophyll fluorescence (SIF) offers a new approach for remote sensing photosynthesis. However, to analyse the response characteristics of SIF under different stress states, a long-term time-series comparative observation of vegetation under different stress states must be carried out at the canopy scale, such that the similarities and differences in SIF change law can be summarized under different time scales. A continuous comparative observation system for vegetation canopy SIF is designed in this study. The system, which is based on a high-resolution spectrometer and an optical multiplexer, can achieve comparative observation of multiple targets. To simultaneously measure the commonly used vegetation index and SIF in the O2-A and O2-B atmospheric absorption bands, the following parameters are used: a spectral range of 475.9 to 862.2 nm, a spectral resolution of approximately 0.9 nm, a spectral sampling interval of approximately 0.4 nm, and the signal-to-noise ratio (SNR) can be as high as 1000:1. To obtain data for both the upward radiance of the vegetation canopy and downward irradiance data with a high SNR in relatively short time intervals, the single-step integration time optimization algorithm is proposed. To optimize the extraction accuracy of SIF, the FluorMOD model is used to simulate sets of data according to the spectral resolution, spectral sampling interval and SNR of the spectrometer in this continuous observation system. These data sets are used to determine the best parameters of Fraunhofer Line Depth (FLD), Three FLD (3FLD) and the spectral fitting method (SFM), and 3FLD and SFM are confirmed to be suitable for extracting SIF from the spectral measurements. This system has been used to observe the SIF values in O2-A and O2-B absorption bands and some commonly used vegetation index from sweet potato and bare land, the result of which shows: (1) the daily variation trend of SIF value of sweet potato leaves is basically same

  1. Remotely estimating photosynthetic capacity, and its response to temperature, in vegetation canopies using imaging spectroscopy

    SciTech Connect

    Serbin, Shawn P.; Singh, Aditya; Desai, Ankur R.; Dubois, Sean G.; Jablonski, Andrew D.; Kingdon, Clayton C.; Kruger, Eric L.; Townsend, Philip A.

    2015-06-11

    To date, the utility of ecosystem and Earth system models (EESMs) has been limited by poor spatial and temporal representation of critical input parameters. For example, EESMs often rely on leaf-scale or literature-derived estimates for a key determinant of canopy photosynthesis, the maximum velocity of RuBP carboxylation (Vcmax, μmol m–2 s–1). Our recent work (Ainsworth et al., 2014; Serbin et al., 2012) showed that reflectance spectroscopy could be used to estimate Vcmax at the leaf level. Here, we present evidence that imaging spectroscopy data can be used to simultaneously predict Vcmax and its sensitivity to temperature (EV) at the canopy scale. In 2013 and 2014, high-altitude Airborne Visible/Infrared Imaging Spectroscopy (AVIRIS) imagery and contemporaneous ground-based assessments of canopy structure and leaf photosynthesis were acquired across an array of monospecific agroecosystems in central and southern California, USA. A partial least-squares regression (PLSR) modeling approach was employed to characterize the pixel-level variation in canopy Vcmax (at a standardized canopy temperature of 30 °C) and EV, based on visible and shortwave infrared AVIRIS spectra (414–2447 nm). Our approach yielded parsimonious models with strong predictive capability for Vcmax (at 30 °C) and EV (R2 of withheld data = 0.94 and 0.92, respectively), both of which varied substantially in the field (≥ 1.7 fold) across the sampled crop types. The models were applied to additional AVIRIS imagery to generate maps of Vcmax and EV, as well as their uncertainties, for agricultural landscapes in California. The spatial patterns exhibited in the maps were consistent with our in-situ observations. As a result, these findings highlight the considerable promise of airborne and, by implication, space-borne imaging spectroscopy, such as the proposed HyspIRI mission, to map spatial and

  2. An Automated Comparative Observation System for Sun-Induced Chlorophyll Fluorescence of Vegetation Canopies.

    PubMed

    Zhou, Xijia; Liu, Zhigang; Xu, Shan; Zhang, Weiwei; Wu, Jun

    2016-05-27

    Detecting sun-induced chlorophyll fluorescence (SIF) offers a new approach for remote sensing photosynthesis. However, to analyse the response characteristics of SIF under different stress states, a long-term time-series comparative observation of vegetation under different stress states must be carried out at the canopy scale, such that the similarities and differences in SIF change law can be summarized under different time scales. A continuous comparative observation system for vegetation canopy SIF is designed in this study. The system, which is based on a high-resolution spectrometer and an optical multiplexer, can achieve comparative observation of multiple targets. To simultaneously measure the commonly used vegetation index and SIF in the O₂-A and O₂-B atmospheric absorption bands, the following parameters are used: a spectral range of 475.9 to 862.2 nm, a spectral resolution of approximately 0.9 nm, a spectral sampling interval of approximately 0.4 nm, and the signal-to-noise ratio (SNR) can be as high as 1000:1. To obtain data for both the upward radiance of the vegetation canopy and downward irradiance data with a high SNR in relatively short time intervals, the single-step integration time optimization algorithm is proposed. To optimize the extraction accuracy of SIF, the FluorMOD model is used to simulate sets of data according to the spectral resolution, spectral sampling interval and SNR of the spectrometer in this continuous observation system. These data sets are used to determine the best parameters of Fraunhofer Line Depth (FLD), Three FLD (3FLD) and the spectral fitting method (SFM), and 3FLD and SFM are confirmed to be suitable for extracting SIF from the spectral measurements. This system has been used to observe the SIF values in O₂-A and O₂-B absorption bands and some commonly used vegetation index from sweet potato and bare land, the result of which shows: (1) the daily variation trend of SIF value of sweet potato leaves is

  3. 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.

  4. 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

  5. Sensitivity of LIDAR Canopy Height Estimate to Geolocation Error

    NASA Astrophysics Data System (ADS)

    Tang, H.; Dubayah, R.

    2010-12-01

    Many factors affect the quality of canopy height structure data derived from space-based lidar such as DESDynI. Among these is geolocation accuracy. Inadequate geolocation information hinders subsequent analyses because a different portion of the canopy is observed relative to what is assumed. This is especially true in mountainous terrain where the effects of slope magnify geolocation errors. Mission engineering design must trade the expense of providing more accurate geolocation with the potential improvement in measurement accuracy. The objective of our work is to assess the effects of small errors in geolocation on subsequent retrievals of maximum canopy height for a varying set of canopy structures and terrains. Dense discrete lidar data from different forest sites (from La Selva Biological Station, Costa Rica, Sierra National Forest, California, and Hubbard Brook and Bartlett Experimental Forests in New Hampshire) are used to simulate DESDynI height retrievals using various geolocation accuracies. Results show that canopy height measurement errors generally increase as the geolocation error increases. Interestingly, most of the height errors are caused by variation of canopy height rather than topography (slope and aspect).

  6. Estimating canopy fuel parameters for Atlantic Coastal Plain forest types.

    SciTech Connect

    Parresol, Bernard, R.

    2007-01-15

    Abstract It is necessary to quantify forest canopy characteristics to assess crown fire hazard, prioritize treatment areas, and design treatments to reduce crown fire potential. A number of fire behavior models such as FARSITE, FIRETEC, and NEXUS require as input four particular canopy fuel parameters: 1) canopy cover, 2) stand height, 3) crown base height, and 4) canopy bulk density. These canopy characteristics must be mapped across the landscape at high spatial resolution to accurately simulate crown fire. Currently no models exist to forecast these four canopy parameters for forests of the Atlantic Coastal Plain, a region that supports millions of acres of loblolly, longleaf, and slash pine forests as well as pine-broadleaf forests and mixed species broadleaf forests. Many forest cover types are recognized, too many to efficiently model. For expediency, forests of the Savannah River Site are categorized as belonging to 1 of 7 broad forest type groups, based on composition: 1) loblolly pine, 2) longleaf pine, 3) slash pine, 4) pine-hardwood, 5) hardwood-pine, 6) hardwoods, and 7) cypress-tupelo. These 7 broad forest types typify forests of the Atlantic Coastal Plain region, from Maryland to Florida.

  7. Flow over a Modern Ram-Air Parachute Canopy

    NASA Astrophysics Data System (ADS)

    Mohammadi, Mohammad; Johari, Hamid

    2010-11-01

    The flow field on the central section of a modern ram-air parachute canopy was examined numerically using a finite-volume flow solver coupled with the one equation Spalart-Allmaras turbulence model. Ram-air parachutes are used for guided airdrop applications, and the canopy resembles a wing with an open leading edge for inflation. The canopy surfaces were assumed to be impermeable and rigid. The flow field consisted of a vortex inside the leading edge opening which effectively closed off the canopy and diverted the flow around the leading edge. The flow experienced a rather bluff leading edge in contrast to the smooth leading of an airfoil, leading to a separation bubble on the lower lip of the canopy. The flow inside the canopy was stagnant beyond the halfway point. The section lift coefficient increased linearly with the angle of attack up to 8.5 and the lift curve slope was about 8% smaller than the baseline airfoil. The leading edge opening had a major effect on the drag prior to stall; the drag is at least twice the baseline airfoil drag. The minimum drag of the section occurs over the angle of attack range of 3 -- 7 .

  8. Modeling intra-crown and intra-canopy interactions in red maple: assessment of light transfer on carbon dioxide and water vapor exchange.

    PubMed

    Bauerle, William L; Bowden, Joseph D; McLeod, Michael F; Toler, Joe E

    2004-05-01

    Daily and seasonal net photosynthesis (Anet), transpiration (E), absorbed photosynthetically active radiation (Qa) and light-use efficiency (epsilonc) in a red maple container nursery were simulated with MAESTRA, a three-dimensional canopy model. Effects of canopy heterogeneity were simulated by imposing changes in crown spacing. The light transfer sub-model, a distribution model of incident, direct, diffuse and scattered radiation within MAESTRA, was validated against field measurements of light interception on an intra-crown scale. In the container nursery, we found that a fiber-optic-based method of integrating photosynthetically active radiation (Q) was more suitable for crown-layer light transfer measurements and adjustments than either orthogonal line or individual quantum sensor measurements. The model underestimated intercepted Q by 9.3, 18 and 11.1% for crown layers 1, 2 and 3, respectively; however, there were linear relationships between model estimates and observations made with each of the three measurement methods. We used the validated and parameterized light transfer model to assess intra-crown and intra-canopy light transfer on a layer, crown and canopy basis, and investigated effects of tree size ratio and tree spacing interactions on Anet, E, Qa and epsilonc in the container nursery. Heterogeneous crown and canopy photosynthesis were predicted to exceed values for a uniform canopy under space-limiting conditions. Tree size ratio had large effects on Anet, E, Qa and epsilonc when light to lower-canopy layers was limited by inadequate space between crowns. Increasing Qa at lower-crown layers had the largest impact on whole-crown and whole-canopy Anet, E, Qa and epsilonc. Increases in canopy productivity led to increased water use. Simulations of heterogeneous stands with adequate soil water indicated that light absorption is maximized under space-limiting conditions as a canopy crown moves toward heterogeneity. Nursery and plantation productivity

  9. Identification of turbulence structures above a forest canopy using a wavelet transform

    NASA Technical Reports Server (NTRS)

    Turner, B. J.; Leclerc, M. Y.; Gauthier, M.; Moore, K. E.; Fitzjarrald, D. R.

    1994-01-01

    The wavelet transform is used to identify scales of large coherent structures present in atmospheric turbulence above the subarctic forest at Schefferville. Individual coherent structures contributing to much of the exchange between the forest and the atmosphere are depicted in terms of both scale and location using contour diagrams of wavelet transform coefficients. Three typical case studies of turbulence and flux observations were selected to examine the physical characteristics of these flux-filled events and their evolution with distance away from the forest canopy. A wavelet transform spectral technique is applied to vertical velocity, temperature, and turbulent heat flux data observed over the sparse coniferous forest to extract the relative importance of each scale present in those data series. The scale of turbulence structures in relation with their characteristic spacing is discussed.

  10. A test of the Suits vegetative-canopy reflectance model with LARS soybean-canopy reflectance data

    NASA Technical Reports Server (NTRS)

    Chance, J. E.; Lemaster, E. W.

    1985-01-01

    The Suits vegetative-canopy reflectance model is tested with an extensive set of field reflectance measurements made by the Laboratory for Application of Remote Sensing (LARS) for soybean canopies. The model is tested for the full hemisphere of observer directions as well as the nadir direction. The results show moderate agreement for the visible channels of the Landsat MSS and poor agreement in the near-infrared channel of Landsat MSS. An analysis of errors is given.

  11. Processes of ammonia air-surface exchange in a fertilized Zea mays canopy

    NASA Astrophysics Data System (ADS)

    Walker, J. T.; Jones, M. R.; Bash, J. O.; Myles, L.; Meyers, T.; Schwede, D.; Herrick, J.; Nemitz, E.; Robarge, W.

    2013-02-01

    Recent incorporation of coupled soil biogeochemical and bi-directional NH3 air-surface exchange algorithms into regional air quality models holds promise for further reducing uncertainty in estimates of NH3 emissions from fertilized soils. While this represents a significant advancement over previous approaches, the evaluation and improvement of such modeling systems for fertilized crops requires process-level field measurements over extended periods of time that capture the range of soil, vegetation, and atmospheric conditions that drive short-term (i.e., post-fertilization) and total growing season NH3 fluxes. This study examines the processes of NH3 air-surface exchange in a fertilized corn (Zea mays) canopy over the majority of a growing season to characterize soil emissions after fertilization and investigate soil-canopy interactions. Micrometeorological flux measurements above the canopy, measurements of soil, leaf apoplast and dew/guttation chemistry, and a combination of in-canopy measurements, inverse source/sink, and resistance modeling were employed. Over a period of approximately 10 weeks following fertilization, daily mean and median net canopy-scale fluxes yielded cumulative total N losses of 8.4% and 6.1%, respectively, of the 134 kg N ha-1 surface applied to the soil as urea ammonium nitrate (UAN). During the first month after fertilization, daily mean emission fluxes were positively correlated with soil temperature and soil volumetric water. Diurnally, maximum hourly average fluxes of ≈ 700 ng N m-2 s-1 occurred near mid-day, coincident with the daily maximum in friction velocity. Net emission was still observed 5 to 10 weeks after fertilization, although mid-day peak fluxes had declined to ≈ 125 ng N m-2 s-1. A key finding of the surface chemistry measurements was the observation of high pH (7.0-8.5) in leaf dew/guttation, which reduced the ability of the canopy to recapture soil emissions during wet periods. In-canopy measurements near peak

  12. Processes of ammonia air-surface exchange in a fertilized Zea mays canopy

    NASA Astrophysics Data System (ADS)

    Walker, J. T.; Jones, M. R.; Bash, J. O.; Myles, L.; Meyers, T.; Schwede, D.; Herrick, J.; Nemitz, E.; Robarge, W.

    2012-06-01

    Recent incorporation of coupled soil biogeochemical and bi-directional NH3 air-surface exchange algorithms into regional air quality models holds promise for further reducing uncertainty in estimates of NH3 emissions from fertilized soils. While this represents a significant advancement over previous approaches, the evaluation and improvement of such modeling systems for fertilized crops requires process level field measurements over extended periods of time that capture the range of soil, vegetation, and atmospheric conditions that drive short term (i.e., post fertilization) and total growing seasonNH3 fluxes. This study examines the processes of NH3 air-surface exchange in a fertilized corn (Zea mays) canopy over the majority of a growing season to characterize soil emissions after fertilization and investigate soil-canopy interactions. Micrometeorological flux measurements above the canopy, measurements of soil, leaf apoplast and dew/guttation chemistry, and a combination of in-canopy measurements, inverse source/sink, and resistance modeling were employed. Over a period of approximately 10 weeks following fertilization, daily mean and median net canopy-scale fluxes yielded cumulative total N losses of 8.4% and 6.1%, respectively, of the 134 kg N ha-1 surface applied to the soil as urea ammonium nitrate (UAN). During the first month after fertilization, daily mean emission fluxes were positively correlated with soil temperature and soil volumetric water. Diurnally, maximum hourly average fluxes of ≈700 ng N m-2 s-1 occurred near mid-day, coincident with the daily maximum in friction velocity. Net emission was still observed 5 to 10 weeks after fertilization, although mid-day peak fluxes had declined to ≈125 ng N m-2 s-1 A key finding of the surface chemistry measurements was the observation of high pH (7.0 - 8.5) in leaf dew/guttation, which reduced the ability of the canopy to recapture soil emissions during wet periods. In-canopy measurements near peak LAI

  13. Energy balance and canopy conductance of a boreal aspen forest: Partitioning overstory and understory components

    NASA Astrophysics Data System (ADS)

    Blanken, P. D.; Black, T. A.; Yang, P. C.; Neumann, H. H.; Nesic, Z.; Staebler, R.; den Hartog, G.; Novak, M. D.; Lee, X.

    1997-12-01

    relationship between forest leaf area index and forest canopy conductance. The timing, duration, and maximum leaf area of this deciduous boreal forest was found to be an important control on transpiration at both levels of the canopy. The full-leaf hazelnut daytime mean Priestley and Taylor [1972] α coefficient of 1.22 indicated transpiration was largely energy controlled and the quantity of energy received at the hazelnut surface was a function of aspen leaf area. The full-leaf aspen daytime mean α of 0.91 indicated some stomatal control on transpiration, with a directly proportional relationship between forest leaf area and forest canopy conductance, varying α during much of the season through a range very sensitive to regional scale transpiration and surface-convective boundary layer feedbacks.

  14. Modeling radiative transfer in tropical rainforest canopies: sensitivity of simulated albedo to canopy architectural and optical parameters.

    PubMed

    Yanagi, Sílvia N M; Costa, Marcos H

    2011-12-01

    This study evaluates the sensitivity of the surface albedo simulated by the Integrated Biosphere Simulator (IBIS) to a set of Amazonian tropical rainforest canopy architectural and optical parameters. The parameters tested in this study are the orientation and reflectance of the leaves of upper and lower canopies in the visible (VIS) and near-infrared (NIR) spectral bands. The results are evaluated against albedo measurements taken above the K34 site at the INPA (Instituto Nacional de Pesquisas da Amazônia) Cuieiras Biological Reserve. The sensitivity analysis indicates a strong response to the upper canopy leaves orientation (χup) and to the reflectivity in the near-infrared spectral band (ρNIR,up), a smaller sensitivity to the reflectivity in the visible spectral band (ρVIS,up) and no sensitivity at all to the lower canopy parameters, which is consistent with the canopy structure. The combination of parameters that minimized the Root Mean Square Error and mean relative error are χup = 0.86, ρVIS,up = 0.062 and ρNIR,up = 0.275. The parameterizations performed resulted in successful simulations of tropical rainforest albedo by IBIS, indicating its potential to simulate the canopy radiative transfer for narrow spectral bands and permitting close comparison with remote sensing products.

  15. Assimilation of Leaf and Canopy Spectroscopic Data to Improve the Representation of Vegetation Dynamics in Terrestrial Ecosystem Models

    NASA Astrophysics Data System (ADS)

    Serbin, S. P.; Dietze, M.; Desai, A. R.; LeBauer, D.; Viskari, T.; Kooper, R.; McHenry, K. G.; Townsend, P. A.

    2013-12-01

    The ability to seamlessly integrate information on vegetation structure and function across a continuum of scales, from field to satellite observations, greatly enhances our ability to understand how terrestrial vegetation-atmosphere interactions change over time and in response to disturbances. In particular, terrestrial ecosystem models require detailed information on ecosystem states and canopy properties in order to properly simulate the fluxes of carbon (C), water and energy from the land to the atmosphere as well as address the vulnerability of ecosystems to environmental and other perturbations. Over the last several decades the amount of available data to constrain ecological predictions has increased substantially, resulting in a progressively data-rich era for global change research. In particular remote sensing data, specifically optical data (leaf and canopy), offers the potential for an important and direct data constraint on ecosystem model projections of C and energy fluxes. Here we highlight the utility of coupling information provided through the Ecosystem Spectral Information System (EcoSIS) with complex process models through the Predictive Ecosystem Analyzer (PEcAn; http://www.pecanproject.org/) eco-informatics framework as a means to improve the description of canopy optical properties, vegetation composition, and modeled radiation balance. We also present this an efficient approach for understanding and correcting implicit assumptions and model structural deficiencies. We first illustrate the challenges and issues in adequately characterizing ecosystem fluxes with the Ecosystem Demography model (ED2, Medvigy et al., 2009) due to improper parameterization of leaf and canopy properties, as well as assumptions describing radiative transfer within the canopy. ED2 is especially relevant to these efforts because it contains a sophisticated structure for scaling ecological processes across a range of spatial scales: from the tree-level (demography

  16. Canopy position has a profound effect on soybean seed composition.

    PubMed

    Huber, Steven C; Li, Kunzhi; Nelson, Randall; Ulanov, Alexander; DeMuro, Catherine M; Baxter, Ivan

    2016-01-01

    Although soybean seeds appear homogeneous, their composition (protein, oil and mineral concentrations) can vary significantly with the canopy position where they were produced. In studies with 10 cultivars grown over a 3-yr period, we found that seeds produced at the top of the canopy have higher concentrations of protein but less oil and lower concentrations of minerals such as Mg, Fe, and Cu compared to seeds produced at the bottom of the canopy. Among cultivars, mean protein concentration (average of different positions) correlated positively with mean concentrations of S, Zn and Fe, but not other minerals. Therefore, on a whole plant basis, the uptake and allocation of S, Zn and Fe to seeds correlated with the production and allocation of reduced N to seed protein; however, the reduced N and correlated minerals (S, Zn and Fe) showed different patterns of allocation among node positions. For example, while mean concentrations of protein and Fe correlated positively, the two parameters correlated negatively in terms of variation with canopy position. Altering the microenvironment within the soybean canopy by removing neighboring plants at flowering increased protein concentration in particular at lower node positions and thus altered the node-position gradient in protein (and oil) without altering the distribution of Mg, Fe and Cu, suggesting different underlying control mechanisms. Metabolomic analysis of developing seeds at different positions in the canopy suggests that availability of free asparagine may be a positive determinant of storage protein accumulation in seeds and may explain the increased protein accumulation in seeds produced at the top of the canopy. Our results establish node-position variation in seed constituents and provide a new experimental system to identify genes controlling key aspects of seed composition. In addition, our results provide an unexpected and simple approach to link agronomic practices to improve human nutrition and health

  17. Canopy position has a profound effect on soybean seed composition

    PubMed Central

    Ulanov, Alexander; DeMuro, Catherine M.

    2016-01-01

    Although soybean seeds appear homogeneous, their composition (protein, oil and mineral concentrations) can vary significantly with the canopy position where they were produced. In studies with 10 cultivars grown over a 3-yr period, we found that seeds produced at the top of the canopy have higher concentrations of protein but less oil and lower concentrations of minerals such as Mg, Fe, and Cu compared to seeds produced at the bottom of the canopy. Among cultivars, mean protein concentration (average of different positions) correlated positively with mean concentrations of S, Zn and Fe, but not other minerals. Therefore, on a whole plant basis, the uptake and allocation of S, Zn and Fe to seeds correlated with the production and allocation of reduced N to seed protein; however, the reduced N and correlated minerals (S, Zn and Fe) showed different patterns of allocation among node positions. For example, while mean concentrations of protein and Fe correlated positively, the two parameters correlated negatively in terms of variation with canopy position. Altering the microenvironment within the soybean canopy by removing neighboring plants at flowering increased protein concentration in particular at lower node positions and thus altered the node-position gradient in protein (and oil) without altering the distribution of Mg, Fe and Cu, suggesting different underlying control mechanisms. Metabolomic analysis of developing seeds at different positions in the canopy suggests that availability of free asparagine may be a positive determinant of storage protein accumulation in seeds and may explain the increased protein accumulation in seeds produced at the top of the canopy. Our results establish node-position variation in seed constituents and provide a new experimental system to identify genes controlling key aspects of seed composition. In addition, our results provide an unexpected and simple approach to link agronomic practices to improve human nutrition and health

  18. 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

  19. The Canopy Conductance of a Humid Grassland

    NASA Astrophysics Data System (ADS)

    Lu, C. T.; Hsieh, C. I.

    2015-12-01

    Penman-Monteith equation is widely used for estimating latent heat flux. The key parameter for implementing this equation is the canopy conductance (gc). Recent research (Blaken and Black, 2004) showed that gc could be well parameterized by a linear function of An/ (D0* X0c), where An represents net assimilation, D0 is leaf level saturation deficit, and X0c is CO2 mole fraction. In this study, we tried to use the same idea for estimating gcfor a humid grassland. The study site was located in County Cork, southwest Ireland (51o59''N 8o46''W), and perennial ryegrass (Lolium perenne L.) was the dominant grass species in this area. An eddy covariance system was used to measure the latent heat flux above this humid grassland. The measured gc was calculated by rearranging Penman-Monteith equation combined with the measured latent heat flux. Our data showed that the gc decreased as the vapor pressure deficit and temperature increased. And it increased as the net radiation increased. Therefore, we found out that the best parameterization of gc was a linear function of the product of the vapor deficit, temperature, and net radiation. Also, we used the gc which was estimated by this linear function to predict the latent heat flux by Penman-Monteith equation and compared the predictions with those where the gc was chosen to be a fixed value. Our analysis showed that this simple linear function for gc can improve the latent heat flux predictions (R square increased from 0.48 to 0.66).

  20. Large tree crowns in closed forest canopies: Measuring structure and estimating light

    NASA Astrophysics Data System (ADS)

    Wolosin, Michael Stephen

    Trees compete for light. Crown traits are the result of an evolutionary history dominated by this fact, and species exhibit a range of strategies including characteristic shapes and light-foraging abilities in response to this competition. Shape plasticity and crown asymmetry result from the growth and death of branches over long time scales. It is impossible to track every branch in stand-scale forest models, and there are no good approaches that accurately capture the emergent tree-level properties of this branch-scale process. Most forest models therefore ignore tree shape and asymmetry. Models of tree size and shape are important in both scientific research and in evaluating policy questions. Light absorption in large canopy trees determines their own demographic rates and sets the template of light levels that drives understory growth and mortality, driving both community and ecosystem processes. Models that ignore crown shape and asymmetry could lead to faulty inferences and predictions. Our work attempts to overcome some of the difficulties in both measuring and modeling large crown shape and light availability. We develop a new approach to extracting three-dimensional crown structural information from high resolution digital stereo imagery to accurately measure crown structure of over nine hundred well-studied large canopy trees. We also present a statistical model that integrates multiple data sources into estimates of the "true" but unmeasurable light available to individual trees. Third, we develop two crown models for forest simulations that capture their space-filling nature with minimum detail, and we parameterize these models from data; one models crown shape, the other crown location. Fourth, we investigate the relationship between light availability and growth. We extract extensive fine-scale structural detail from the imagery, and generate detailed crown envelopes. We find that light availability predicts the growth rates of large trees primarily

  1. Assessing the influence of topography and canopy structure on Douglas fir throughfall with LiDAR and empirical data in the Santa Cruz mountains, USA.

    PubMed

    Griffith, K T; Ponette-González, A G; Curran, L M; Weathers, K C

    2015-05-01

    Atmospheric inputs to forest ecosystems vary considerably over small spatial scales due to subtle changes in relief and vegetation structure. Relationships between throughfall fluxes (ions that pass through the canopy in water), topographic and canopy characteristics derived from sub-meter resolution light detection and ranging (LiDAR), and field measurements were compared to test the potential utility of LiDAR in empirical models of atmospheric deposition. From October 2012 to May 2013, we measured bulk (primarily wet) deposition and sulfate-S, chloride (Cl(-)), and nitrate-N fluxes beneath eight clusters of Douglas fir trees differing in size and canopy exposure in the Santa Cruz Mountains, California. For all trees sampled, LiDAR data were used to derive canopy surface height, tree height, slope, and canopy curvature, while tree height, diameter (DBH), and leaf area index were measured in the field. Wet season throughfall fluxes to Douglas fir clusters ranged from 1.4 to 3.8 kg S ha(-1), 17-54 kg Cl(-) ha(-1), and 0.2-4 kg N ha(-1). Throughfall S and Cl(-) fluxes were highest under clusters with large trees at topographically exposed sites; net fluxes were 2-18-fold greater underneath exposed/large clusters than all other clusters. LiDAR indices of canopy curvature and height were positively correlated with net sulfate-S fluxes, indicating that small-scale canopy surface features captured by LiDAR influence fog and dry deposition. Although tree diameter was more strongly correlated with net sulfate-S throughfall flux, our data suggest that LiDAR data can be related to empirical measurements of throughfall fluxes to generate robust high-resolution models of atmospheric deposition.

  2. The effect of urban canopy parameterizations on mesoscale meteorological model simulations in the Paso del Norte area

    SciTech Connect

    Brown, M.J.; Williams, M.D.

    1997-04-01

    Since mesoscale numerical models do not have the spatial resolution to directly simulate the fluid dynamics and thermodynamics in and around urban structures, urban canopy parameterizations are sometimes used to approximate the drag, heating, and enhanced turbulent kinetic energy (tke) produced by the sub-grid scale urban elements. In this paper, we investigate the effect of the urban canopy parameterizations used in the HOTMAC mesoscale meteorological model by turning the parameterizations on and off. The model simulations were performed in the Paso del Norte region, which includes the cities of El Paso and Ciudad Juarez, the Franklin and Sierra Juarez mountains, and the Rio Grande. The metropolitan area is surrounded by relatively barren scrubland and is intersected by strips of vegetation along the Rio Grande. Results indicate that the urban canopy parameterizations do affect the mesoscale flow field, reducing the magnitude of wind speed and changing the magnitude of the sensible heat flux and tke in the metropolitan area. A nighttime heat island and a daytime cool island exist when urban canopy parameters are turned on, but associated recirculation flows are not readily apparent. Model-computed solar, net, and longwave radiation values look reasonable, agreeing for the most part with published measurements.

  3. How neighbor canopy architecture affects target plant performance

    SciTech Connect

    Tremmel, D.C.; Bazzaz, F.A. )

    1993-10-01

    Plant competition occurs through the negative effects that individual plants have on resource availability to neighboring individuals. Therefore competition experiments need to examine how different species change resource availability to their neighbors, and how different species respond to these changes-allocationally, architecturally, and physiologically-through time. In a greenhouse study we used a model system of annuals to examine how canopies of species having differing morphologies differed in their architectures and light-interception abilities, and how different species performed when grown in these canopies. Abutilon theophrasti, Datura stramonium, and Polygonum pensylvanicum were grown as [open quotes]targets[close quotes]. Plants were grown in pots, with one target plant and four neighbor plants. Detailed measurements of neighbor canopy structure and target plant canopy architecture were made at five harvests. Species with different morphologies showed large differences in canopy structure, particularly when grass and forb species were compared. Setaria, a grass, had a more open canopy than the other species (all forbs), and was a consistently weak competitor. Overall, however, the relative effects of different neighbors on target biomass varied with target species. Target biomass was poorly correlated with neighbor biomass and leaf area, but was highly correlated with a measure of target light-interception ability that took into account both target leaf deployment and neighbor light interception. Despite clear differences among neighbor species in canopy structure and effect on light penetration, the results suggest no broad generalizations about the effects of different species as neighbors. Knowledge of morphological, physiological, and life history characteristics of both the target and neighbor species may be necessary to explain the results of their competition. 53 refs., 4 figs., 4 tabs.

  4. Removing forest canopy cover restores a reptile assemblage.

    PubMed

    Pike, David A; Webb, Jonathan K; Shine, Richard

    2011-01-01

    Humans are rapidly altering natural systems, leading to changes in the distribution and abundance of species. However, so many changes are occurring simultaneously (e.g., climate change, habitat fragmentation) that it is difficult to determine the cause of population fluctuations from correlational studies. We used a manipulative field experiment to determine whether forest canopy cover directly influences reptile assemblages on rock outcrops in southeastern Australia. Our experimental design consisted of three types of rock outcrops: (1) shady sites in which overgrown vegetation was manually removed (n = 25); (2) overgrown controls (n = 30); and (3) sun-exposed controls (n = 20). Following canopy removal, we monitored reptile responses over 30 months. Canopy removal increased reptile species richness, the proportion of shelter sites used by reptiles, and relative abundances of five species that prefer sun-exposed habitats. Our manipulation also decreased the abundances of two shade-tolerant species. Canopy cover thus directly influences this reptile assemblage, with the effects of canopy removal being dependent on each species' habitat preferences (i.e., selection or avoidance of sun-exposed habitat). Our study suggests that increases in canopy cover can cause declines of open-habitat specialists, as previously suggested by correlative studies from a wide range of taxa. Given that reptile colonization of manipulated outcrops occurred rapidly, artificially opening the canopy in ecologically informed ways could help to conserve imperiled species with patchy distributions and low vagility that are threatened by vegetation overgrowth. One such species is Australia's most endangered snake, the broadheaded snake (Hoplocephalus bungaroides).

  5. Assessment of Drought Constraints on Transpiration and Canopy Conductance in Mature Aspen and Jack Pine Stands

    NASA Astrophysics Data System (ADS)

    Bernier, P. Y.; Bartlett, P. A.; Black, T. A.; Barr, A. G.; Kljun, N.; McCaughey, J. H.

    2005-12-01

    Soil water content can exert an important control on tree growth processes, an important consideration for the boreal forest in Central Canada where climate change may bring about increased drought frequency. Empirical evidence has shown the strong coupling between conductance and photosynthesis, and the effect that drought can have on both variables. In models, canopy conductance and carbon uptake are often explicitly related through feedback loops that may or may not include the consideration of soil water content. Models that are aimed towards landscape-level applications usually require the scaling up of response functions to coarse spatial and temporal scales. Although at such scales, crude models of stomatal response to environmental variables are sufficient, empirical data for parameter estimates or for validation of response functions on such scales are difficult to obtain. From 2001 to 2003, the Canadian Prairies and adjacent boreal forest were subjected to a severe drought that affected two sites over which continuous measurements of ecosystem exchanges of CO2 and water vapour had been made for a number of years: an aspen stand on a sandy clay loam soil, and a jack pine stand on coarse sand. The continuous measurements of CO2 exchanges provided an ecosystem-level experiment of drought impacts on canopy conductance. The objectives of this work were therefore to 1) determine the rooting depth at these sites based on measurements of transpiration and soil moisture 2) quantify the relationship between soil water content and canopy conductance for contrasting forested sites 3) determine whether these relationships were modified by the temporal scale at which they were analysed and 4) verify the applicability of published relationships for quantifying the impact of drought on gas exchanges. The results show that depth of water uptake (rooting depth) varies with soil texture, and tends to be shallower in coarser-textured soils. In this large drought event, soil

  6. Estimation of canopy height using lidar and radar interferometry: an assessment of combination methods and sensitivity to instrument, terrain and canopy height profile

    NASA Astrophysics Data System (ADS)

    Simard, M.; Neumann, M.; Pinto, N.; Brolly, M.; Brigot, G.

    2014-12-01

    The combined use of Lidar and radar interferometry to estimate canopy height can be classified into 3 categories: cross-validation, simple combination and fusion methods. In this presentation, we investigate the potential of each category for local and regional scale applications, and assess their sensitivity to instrument configuration, terrain topography and variations in the vertical forest canopy profiles. In addition to field data, we use data from TanDEM-X, UAVSAR (Uninhabited Aerial Vehicle Synthetic Aperture Radar), LVIS (Laser Vegetation Imaging Sensor) and a commercial discrete lidar. TanDEM-X is a pair of X-band spaceborne radars flying in formation to provide a global digital surface model and can also be used to perform polarimetric synthetic aperture radar (polinSAR) inversion of canopy height. The UAVSAR is an airborne fully polarimetric radar enabling repeat-pass interferometry and has been used for polinsar. While LVIS records the full waveform within a 20m footprint, the discrete lidar collects a cloud of points. The lidar data can be used to validate the polinSAR results (validation), to obtain ground elevation (simple combination with radar surface models) or within the polinSAR inversion model through a common model framework. The data was collected over the Laurentides Wildlife Reserve, a managed territory covering 7861km2 which is located between Québec city and Saguenay. The variety of management practices offers the possibility for long term and comparative studies of natural forest dynamics as well as the impact of human, fires and insect disturbances. The large elevational gradient of the region (~1000m) allows study of variations in structure and type of forests. Depending on the method used, several factors may degrade the accuracy of canopy height estimates from the combined use of lidar and radar interferometry. Here we will consider misregistration of datasets, differences in spatial resolution and viewing geometry, geometric

  7. Effects of elevated atmospheric CO{sub 2} on canopy transpiration in senescent spring wheat

    SciTech Connect

    Grossman, S.; Kimball, B.A.; Hunsaker, D.J.; Long, S.P. et al

    1998-12-31

    The seasonal course of canopy transpiration and the diurnal courses of latent heat flux of a spring wheat crop were simulated for atmospheric CO{sub 2} concentrations of 370 {micro}mol mol{sup {minus}1} and 550 {micro}mol mol{sup {minus}1}. The hourly weather data, soil parameters and the irrigation and fertilizer treatments of the Free-Air Carbon Dioxide Enrichment wheat experiment in Arizona (1992/93) were used to drive the model. The simulation results were tested against field measurements with special emphasis on the period between anthesis and maturity. A model integrating leaf photosynthesis and stomatal conductance was scaled to a canopy level in order to be used in the wheat growth model. The simulated intercellular CO{sub 2} concentration, C{sub i} was determined from the ratio of C{sub i} to the CO{sub 2} concentration at the leaf surface, C{sub s}, the leaf to air specific humidity deficit and a possibly unfulfilled transpiration demand. After anthesis, the measured assimilation rates of the flag leaves decreased more rapidly than their stomatal conductances, leading to a rise in the C{sub i}/C{sub s} ratio. In order to describe this observation, an empirical model approach was developed which took into account the leaf nitrogen content for the calculation of the C{sub i}/C{sub s} ratio. Simulation results obtained with the new model version were in good agreement with the measurements. If changes in the C{sub i}/C{sub s} ratio accorded to the decrease in leaf nitrogen content during leaf senescence were not considered in the model, simulations revealed an underestimation of the daily canopy transpiration of up to twenty percent and a decrease in simulated seasonal canopy transpiration by ten percent. The measured reduction in the seasonal sum of canopy transpiration and soil evaporation owing to CO{sub 2} enrichment, in comparison, was only about five percent.

  8. Throughfall deposition and canopy exchange processes along a vertical gradient within the canopy of beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst).

    PubMed

    Adriaenssens, Sandy; Hansen, Karin; Staelens, Jeroen; Wuyts, Karen; De Schrijver, An; Baeten, Lander; Boeckx, Pascal; Samson, Roeland; Verheyen, Kris

    2012-03-15

    To assess the impact of air pollution on forest ecosystems, the canopy is usually considered as a constant single layer in interaction with the atmosphere and incident rain, which could influence the measurement accuracy. In this study the variation of througfall deposition and derived dry deposition and canopy exchange were studied along a vertical gradient in the canopy of one European beech (Fagus sylvatica L.) tree and two Norway spruce (Picea abies (L.) Karst) trees. Throughfall and net throughfall deposition of all ions other than H(+) increased significantly with canopy depth in the middle and lower canopy of the beech tree and in the whole canopy of the spruce trees. Moreover, throughfall and net throughfall of all ions in the spruce canopy decreased with increasing distance to the trunk. Dry deposition occurred mainly in the upper canopy and was highest during the growing season for H(+), NH(4)(+), NO(3)(-) and highest during the dormant season for Na(+), Cl(-), SO(4)(2-) (beech and spruce) and K(+), Ca(2+) and Mg(2+) (spruce only). Canopy leaching of K(+), Ca(2+) and Mg(2+) was observed at all canopy levels and was higher for the beech tree compared to the spruce trees. Canopy uptake of inorganic nitrogen and H(+) occurred mainly in the upper canopy, although significant canopy uptake was found in the middle canopy as well. Canopy exchange was always higher during the growing season compared to the dormant season. This spatial and temporal variation indicates that biogeochemical deposition models would benefit from a multilayer approach for shade-tolerant tree species such as beech and spruce.

  9. Performance of an Ultrasonic Ranging Sensor in Apple Tree Canopies

    PubMed Central

    Escolà, Alexandre; Planas, Santiago; Rosell, Joan Ramon; Pomar, Jesús; Camp, Ferran; Solanelles, Francesc; Gracia, Felip; Llorens, Jordi; Gil, Emilio

    2011-01-01

    Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture. PMID:22163749

  10. Performance of an ultrasonic ranging sensor in apple tree canopies.

    PubMed

    Escolà, Alexandre; Planas, Santiago; Rosell, Joan Ramon; Pomar, Jesús; Camp, Ferran; Solanelles, Francesc; Gracia, Felip; Llorens, Jordi; Gil, Emilio

    2011-01-01

    Electronic canopy characterization is an important issue in tree crop management. Ultrasonic and optical sensors are the most used for this purpose. The objective of this work was to assess the performance of an ultrasonic sensor under laboratory and field conditions in order to provide reliable estimations of distance measurements to apple tree canopies. To this purpose, a methodology has been designed to analyze sensor performance in relation to foliage ranging and to interferences with adjacent sensors when working simultaneously. Results show that the average error in distance measurement using the ultrasonic sensor in laboratory conditions is ±0.53 cm. However, the increase of variability in field conditions reduces the accuracy of this kind of sensors when estimating distances to canopies. The average error in such situations is ±5.11 cm. When analyzing interferences of adjacent sensors 30 cm apart, the average error is ±17.46 cm. When sensors are separated 60 cm, the average error is ±9.29 cm. The ultrasonic sensor tested has been proven to be suitable to estimate distances to the canopy in field conditions when sensors are 60 cm apart or more and could, therefore, be used in a system to estimate structural canopy parameters in precision horticulture.

  11. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1985-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a Landsat MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95 percent of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50 percent of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73 percent of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  12. Bio-inspired canopies for the reduction of roughness noise

    NASA Astrophysics Data System (ADS)

    Clark, Ian A.; Daly, Conor A.; Devenport, William; Alexander, W. Nathan; Peake, Nigel; Jaworski, Justin W.; Glegg, Stewart

    2016-12-01

    This work takes inspiration from the structure of the down covering the flight feathers of larger species of owls, which contributes to their ability to fly almost silently at frequencies above 1.6 kHz. Microscope photographs of the down show that it consists of hairs that form a structure similar to that of a forest. The hairs initially rise almost perpendicular to the feather surface but then bend over in the flow direction to form a canopy with an open area ratio of about 70 percent. Experiments have been performed to examine the noise radiated by a large open area ratio canopy suspended above a surface. The canopy is found to dramatically reduce pressure fluctuations on the underlying surface. While the canopy can produce its own sound, particularly at high frequencies, the reduction in surface pressure fluctuations can reduce the noise scattered from an underlying rough surface at lower frequencies. A theoretical model is developed which characterizes the mechanism of surface pressure reduction as a result of the mixing layer instability of flow over forest canopies.

  13. Spectral estimators of absorbed photosynthetically active radiation in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.; Bauer, M. E.

    1984-01-01

    Most models of crop growth and yield require an estimate of canopy leaf area index (LAI) or absorption of radiation. Relationships between photosynthetically active radiation (PAR) absorbed by corn canopies and the spectral reflectance of the canopies were investigated. Reflectance factor data were acquired with a LANDSAT MSS band radiometer. From planting to silking, the three spectrally predicted vegetation indices examined were associated with more than 95% of the variability in absorbed PAR. The relationships developed between absorbed PAR and the three indices were evaluated with reflectance factor data acquired from corn canopies planted in 1979 through 1982. Seasonal cumulations of measured LAI and each of the three indices were associated with greater than 50% of the variation in final grain yields from the test years. Seasonal cumulations of daily absorbed PAR were associated with up to 73% of the variation in final grain yields. Absorbed PAR, cumulated through the growing season, is a better indicator of yield than cumulated leaf area index. Absorbed PAR may be estimated reliably from spectral reflectance data of crop canopies.

  14. Seasonal bird use of canopy gaps in a bottomland forest.

    SciTech Connect

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

    2007-04-01

    ABSTRACT.—Bird use of small canopy gaps within mature forests has not been well studied, particularly across multiple seasons. We investigated seasonal differences in bird use of gap and forest habitat within a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. Gaps were 0.13- to 0.5-ha, 7- to 8-year-old group-selection timber harvest openings. Our study occurred during four bird-use periods (spring migration, breeding, postbreeding, and fall migration) in 2001 and 2002. We used plot counts and mist netting to estimate bird abundance in canopy gaps and surrounding mature forest habitats. Using both survey methods, we observed more birds, including forest-interior species, forest-edge species, field-edge species, and several individual species in canopy gap and gap-edge habitats than in surrounding mature forest during all periods. Interactions between period and habitat type often were significant in models, suggesting a seasonal shift in habitat use. Bird activity generally shifted between the interior of canopy gaps and the immediate gap edge, but many species increased their use of forested habitat during the breeding period. This suggests that many species of birds selectively choose gap and gap-edge habitat over surrounding mature forest during the non-breeding period. Creation of small canopy gaps within a mature forest may increase local bird species richness. The reasons for increased bird activity in gaps remain unclear.

  15. Canopy reflectance modeling in a tropical wooded grassland

    NASA Technical Reports Server (NTRS)

    Simonett, David; Franklin, Janet

    1986-01-01

    Geometric/optical canopy reflectance modeling and spatial/spectral pattern recognition is used to study the form and structure of savanna in West Africa. An invertible plant canopy reflectance model is tested for its ability to estimate the amount of woody vegetation from remotely sensed data in areas of sparsely wooded grassland. Dry woodlands and wooded grasslands, commonly referred to as savannas, are important ecologically and economically in Africa, and cover approximately forty percent of the continent by some estimates. The Sahel and Sudan savannas make up the important and sensitive transition zone between the tropical forests and the arid Sahara region. The depletion of woody cover, used for fodder and fuel in these regions, has become a very severe problem for the people living there. LANDSAT Thematic Mapper (TM) data is used to stratify woodland and wooded grassland into areas of relatively homogeneous canopy cover, and then an invertible forest canopy reflectance model is applied to estimate directly the height and spacing of the trees in the stands. Because height and spacing are proportional to biomass in some cases, a successful application of the segmentation/modeling techniques will allow direct estimation of tree biomass, as well as cover density, over significant areas of these valuable and sensitive ecosystems. The model being tested in sites in two different bioclimatic zones in Mali, West Africa, will be used for testing the canopy model. Sudanian zone crop/woodland test sites were located in the Region of Segou, Mali.

  16. The nocturnal water cycle in an open-canopy forest

    NASA Astrophysics Data System (ADS)

    Berkelhammer, M.; Hu, J.; Bailey, A.; Noone, D. C.; Still, C. J.; Barnard, H.; Gochis, D.; Hsiao, G. S.; Rahn, T.; Turnipseed, A.

    2013-09-01

    The movement of moisture into, out-of, and within forest ecosystems is modulated by feedbacks that stem from processes which couple plants, soil, and the atmosphere. While an understanding of these processes has been gleaned from Eddy Covariance techniques, the reliability of the method suffers at night because of weak turbulence. During the summer of 2011, continuous profiles of the isotopic composition (i.e., δ18O and δD) of water vapor and periodic measurements of soil, leaf, and precipitation pools were measured in an open-canopy ponderosa pine forest in central Colorado to study within-canopy nocturnal water cycling. The isotopic composition of the nocturnal water vapor varies significantly based on the relative contributions of the three major hydrological processes acting on the forest: dewfall, exchange of moisture between leaf waters and canopy vapor, and periodic mixing between the canopy and background air. Dewfall proved to be surprisingly common (˜30% of the nights) and detectable on both the surface and within the canopy through the isotopic measurements. While surface dew could be observed using leaf wetness and soil moisture sensors, dew in the foliage was only measurable through isotopic analysis of the vapor and often occurred even when no dew accumulated on the surface. Nocturnal moisture cycling plays a critical role in water availability in forest ecosystems through foliar absorption and transpiration, and assessing these dynamics, as done here, is necessary for fully characterizing the hydrological controls on terrestrial productivity.

  17. 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.

  18. Microwave backscattering and emission model for grass canopies

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; Levine, David M.; Lang, Roger H.

    1994-01-01

    Microwave radar and radiometer measurements of grasslands indicate a substantial reduction in sensor sensitivity to soil moisture in the presence of a thatch layer. When this layer is wet it masks changes in the underlying soil, making the canopy appear warm in the case of passive sensors (radiometer) and decreasing backscatter in the active case (scatterometer). A model for a grass canopy with thatch will be presented in this paper to explain this behavior and to compare with observations. The canopy model consists of three layers: grass, thatch, and the underlying soil. The grass blades are modeled by elongated elliptical discs and the thatch is modeled as a collection of disk shaped water droplets (i.e., the dry matter is neglected). The ground is homogeneous and flat. The distorted Born approximation is used to compute the radar cross section of this three layer canopy and the emissivity is computed from the radar cross section using the Peake formulation for the passive problem. Results are computed at L-band (1.4 GHz) and C-band (4.75 GHz) using canopy parameters (i.e., plant geometry, soil moisture, plant moisture, etc.) representative of Konza Prairie grasslands. The results are compared to C-band scatterometer measurements and L-band radiometer measurements at these grasslands.

  19. Modeling the backscattering and transmission properties of vegetation canopies

    NASA Technical Reports Server (NTRS)

    Allen, C. T.; Ulaby, F. T.

    1984-01-01

    Experimental measurements of canopy attenuation at 10.2 GHz (X-band) for canopies of wheat and soybeans, experimental observations of the effect upon the microwave backscattering coefficient (sigma) of free water in a vegetation canopy, and experimental measurements of sigma (10.2 GHz, 50 deg, VV and VH polarization) of 30 agricultural fields over the growing season of each crop are discussed. The measurements of the canopy attenuation through wheat independently determined the attenuation resulting from the wheat heads and that from the stalks. An experiment conducted to simulate the effects of rain or dew on sigma showed that sigma increases by about 3 dB as a result of spraying a vegetation canopy with water. The temporal observations of sigma for the 30 agricultural fields (10 each of wheat, corn, and soybeans) indicated fields of the same crop type exhibits similar temporal patterns. Models previously reported were tested using these multitemporal sigma data, and a new model for each crop type was developed and tested. The new models proved to be superior to the previous ones.

  20. Comparison of four models to calculate canopy resistance of maize in North Italy

    NASA Astrophysics Data System (ADS)

    Gharsallah, O.; Ravazzani, G.; Mancini, M.; Rana, G.

    2010-05-01

    This paper examines four models for estimating canopy resistance rc, since it is not a purely physiological term, but it depends also on the prevailing climatic conditions get established over the canopy, in order to calculate the actual evapotranspiration on hourly and daily scales, for maize crop grown in North Italy. A comparison between Measured and estimated eddy covariance data was carried out by analysing in details the four models 1) Monteith, 2) Jarvis, 3) Katerji-Perrier, 4) Todorovic. They are either semi-empirical (1, 2 and 3) or mechanistic (4). Furthermore, the FAO approach was also evaluated and compared with the others techniques. In synthesis, rc has not been considered as constant but modelled in function of leaf area index through the approach of Monteith and influenced by the photo synthetically active radiation, the vapour pressure deficit, ambient temperature and the soil moisture through the approach of Jarvis. Moreover, rc has been modelled as a function of the climatic variables and water status condition through the approach of Katerji-Perrier which needs a calibration and finally as a function of only the climatic condition through the approach of Todorovic which does not need any calibration. The results confirmed the good accuracy of Katerji-Perrier method at both hourly and daily scale, while the approach of Monteith, Jarvis and Todorovic provided an overestimation respectively 12%, 27% and 30%. However, the evaluation of FAO method gave an overestimation and showed that both ET0 and Kc could be sources of errors. Key words: Canopy resistance, eddy covariance, Monteith, Jarvis, Katerji-Perrier, Todorovic, FAO

  1. Explaining the variability of Photochemical Reflectance Index (PRI): deconvolution of variability related to Light Use Efficiency and Canopy attributes.

    NASA Astrophysics Data System (ADS)

    Merlier, Elodie; Hmimina, Gabriel; Dufrêne, Eric; Soudani, Kamel

    2014-05-01

    The Photochemical Reflectance Index (PRI) was designed as a proxy of the state of xanthophyll cycle which is used as a response of plants to excess of light (Gamon et al., 1990; 1992). Strong relationships between PRI and LUE were shown at leaf and canopy scales and over a wide range of species (Garbulsky et al., 2011). However, its use at canopy scale was shown to be significantly hampered by effects of confounding factors such as the PRI sensitivity to leaf pigment content (Gamon et al. 2001; Nakaji et al. 2006) and to canopy structure (Hilker et al. 2008). Several approaches aimed at correcting such effects and recent works focused on the deconvolution of LUE related and LUE unrelated PRI variability (Rahimzadeh-Bajgiran et al. 2012).In this study, the PRI variability at canopy scale is investigated over two years on three species (Fagus sylvatica, Quercus robur and Pinus sylvestris) growing under two water regimes. At daily scale, PRI variability is mainly explained by radiation conditions. As already reported at leaf scale in Hmimina et al. (2014), analysis of PRI responses to incoming photosynthetically active radiation over seasonal scale allowed to separate two sources of variability : a constitutive variability mainly related to canopy structure and leaf chlorophyll content and a facultative variability mainly related to LUE and soil moisture content. These results highlight the composite nature of PRI signal measured at canopy scale and the importance of disentangling its sources of variability in order to accurately assess ecosystem light use efficiency. Gamon JA, Field CB, Bilger W, Björkman O, Fredeen AL, Peñuelas J. 1990. Remote sensing of the xanthophyll cycle and chlorophyll fluorescence in sunflower leaves and canopies. Oecologia 85, 1-7. Gamon JA, Field CB, Fredeen A AL, Thayer S. 2001. Assessing photosynthetic downregulation in sunflower stands with an optically-based model. Photosynthesis Research 67, 113-125. Gamon JA, Peñuelas J, Field CB

  2. Sunfleck dynamics and canopy structure in a Phaseolus vulgaris L. canopy

    NASA Astrophysics Data System (ADS)

    Barradas, Victor L.; Jones, Hamlyn G.; Clark, Jerry A.

    Photosynthetic photon flux density (PPFD) fluctuations were quantified in crops of beans (Phaseolus vulgaris L.) in the field as the canopy developed between July and October. Two different methods were used to select sunflecks and shadeflecks. Four ranges of zenith angles (60-70°, 50-60°, 40-50° and 30-40°) were selected for analysing PPFD fluctuations. At the base of the canopy, sunflecks contributed 18%, 53%, 10% and 4% during the 1st, 3rd, 5th and 7th week of growth, respectively. At a height of 20 cm above the soil surface, the respective contributions were 28% and 21% during the 6th and 7th weeks. Sunfleck lengths of 0-5 s were the most frequent, with the greatest number being found with smaller zenith angles. The proportion of short duration sunflecks increased as the growth period advanced. The number of long sunflecks decreased with time, with very few longer than 100 s by the 5th and 7th weeks. The distributions of sunfleck irradiance were similar to normal distributions and irradiance ranged in μmol m-2 s-1 from 600-900, 800-1500 and 1000-1600 respectively at zenith angles of 50-60°, 40-50° and 30-40°. A multiple regression showed that short sunflecks (<100 s) depended on zenith angle, plant height, and leaf and stem area index (Ls), whereas long sunflecks (>100 s) depended on zenith angle and Ls. Shadefleck distributions were similar to those for sunflecks but there were fewer of the shortest examples and more of the longest. The best statistical distribution to describe sunflecks and shadeflecks was the gamma distribution, which could provide the basis for the future development of a good model for sunfleck and shadefleck distributions.

  3. Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks

    PubMed Central

    Ollinger, S. V.; Richardson, A. D.; Martin, M. E.; Hollinger, D. Y.; Frolking, S. E.; Reich, P. B.; Plourde, L. C.; Katul, G. G.; Munger, J. W.; Oren, R.; Smith, M.-L.; Paw U, K. T.; Bolstad, P. V.; Cook, B. D.; Day, M. C.; Martin, T. A.; Monson, R. K.; Schmid, H. P.

    2008-01-01

    The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO2 uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO2 uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle–climate models. PMID:19052233

  4. Canopy nitrogen, carbon assimilation, and albedo in temperate and boreal forests: Functional relations and potential climate feedbacks.

    PubMed

    Ollinger, S V; Richardson, A D; Martin, M E; Hollinger, D Y; Frolking, S E; Reich, P B; Plourde, L C; Katul, G G; Munger, J W; Oren, R; Smith, M-L; Paw U, K T; Bolstad, P V; Cook, B D; Day, M C; Martin, T A; Monson, R K; Schmid, H P

    2008-12-09

    The availability of nitrogen represents a key constraint on carbon cycling in terrestrial ecosystems, and it is largely in this capacity that the role of N in the Earth's climate system has been considered. Despite this, few studies have included continuous variation in plant N status as a driver of broad-scale carbon cycle analyses. This is partly because of uncertainties in how leaf-level physiological relationships scale to whole ecosystems and because methods for regional to continental detection of plant N concentrations have yet to be developed. Here, we show that ecosystem CO(2) uptake capacity in temperate and boreal forests scales directly with whole-canopy N concentrations, mirroring a leaf-level trend that has been observed for woody plants worldwide. We further show that both CO(2) uptake capacity and canopy N concentration are strongly and positively correlated with shortwave surface albedo. These results suggest that N plays an additional, and overlooked, role in the climate system via its influence on vegetation reflectivity and shortwave surface energy exchange. We also demonstrate that much of the spatial variation in canopy N can be detected by using broad-band satellite sensors, offering a means through which these findings can be applied toward improved application of coupled carbon cycle-climate models.

  5. The influence of leaf photosynthetic efficiency and stomatal closure on canopy carbon uptake and evapotranspiration - a model study in wheat and sugar beet

    NASA Astrophysics Data System (ADS)

    Schickling, A.; Graf, A.; Pieruschka, R.; Plückers, C.; Geiß, H.; Lai, I.-L.; Schween, J. H.; Erentok, K.; Schmidt, M.; Wahner, A.; Crewell, S.; Rascher, U.

    2010-09-01

    In this study two crop species, winter wheat (Triticum aestivum) and sugar beet (Beta vulgaris), were monitored over the course of five days during the entire season. We investigated the link of the main physiological leaf-level mechanisms, stomatal conductance and efficiency of photosynthetic energy conversion on canopy transpiration and photosynthetic CO2 uptake. The physiological status of 900 leaves of different plants in a natural canopy was characterized on the leaf level using chlorophyll fluorescence. Gas exchange measurements were performed at leaves of 12 individual plants of each species. Eddy covariance flux measurements provided information on CO2, water and energy fluxes on the field scale. The diurnal pattern of stomatal resistance on the leaf level was especially for sugar beet similar to the canopy resistance, which indicates that stomatal resistance may have a large impact on the bulk canopy resistance. The diurnal changes in canopy resistance appeared to have less effect on the evapotranspiration, which was mainly dependent on the amount of incoming radiation. The similar diurnal pattern of water use efficiency on the leaf level and on the canopy level during the day, underline the influence of physiological mechanisms of leaves on the canopy. The greatest difference between water use efficiency on leaf and canopy occurred in the morning, mainly due to an increase of stomatal resistance. Limitation of CO2 uptake occurred in the afternoon when water vapor pressure deficit increased. Maxima of net ecosystem productivity corresponded to the highest values of photosynthetic capacity of single leaves, which occurred before solar noon. Within the course of a few hours, photosynthetic efficiency and stomatal resistance of leaves varied and these variations were the reason for diurnal variations in the carbon fluxes of the whole field. During the seasonal development, the leaf area index was the main factor driving carbon and water exchange, when both

  6. The Pre-penumbral Magnetic Canopy in the Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    MacTaggart, David; Guglielmino, Salvo L.; Zuccarello, Francesca

    2016-11-01

    Penumbrae are the manifestation of magnetoconvection in highly inclined (to the vertical direction) magnetic field. The penumbra of a sunspot tends to form, initially, along the arc of the umbra antipodal to the main region of flux emergence. The question of how highly inclined magnetic field can concentrate along the antipodal curves of umbrae, at least initially, remains to be answered. Previous observational studies have suggested the existence of some form of overlying magnetic canopy that acts as the progenitor for penumbrae. We propose that such overlying magnetic canopies are a consequence of how the magnetic field emerges into the atmosphere and are, therefore, part of the emerging region. We show, through simulations of twisted flux tube emergence, that canopies of highly inclined magnetic field form preferentially at the required locations above the photosphere.

  7. Canopy interactions and physical stress gradients in subtidal communities.

    PubMed

    Bennett, Scott; Wernberg, Thomas; de Bettignies, Thibaut; Kendrick, Gary A; Anderson, Robert J; Bolton, John J; Rodgers, Kirsten L; Shears, Nick T; Leclerc, Jean-Charles; Lévêque, Laurent; Davoult, Dominique; Christie, Hartvig C

    2015-07-01

    Species interactions are integral drivers of community structure and can change from competitive to facilitative with increasing environmental stress. In subtidal marine ecosystems, however, interactions along physical stress gradients have seldom been tested. We observed seaweed canopy interactions across depth and latitudinal gradients to test whether light and temperature stress structured interaction patterns. We also quantified interspecific and intraspecific interactions among nine subtidal canopy seaweed species across three continents to examine the general nature of interactions in subtidal systems under low consumer pressure. We reveal that positive and neutral interactions are widespread throughout global seaweed communities and the nature of interactions can change from competitive to facilitative with increasing light stress in shallow marine systems. These findings provide support for the stress gradient hypothesis within subtidal seaweed communities and highlight the importance of canopy interactions for the maintenance of subtidal marine habitats experiencing environmental stress.

  8. Relative influence of city structure on canopy photosynthesis

    NASA Astrophysics Data System (ADS)

    O'Rourke, P. A.; Terjung, W. H.

    1981-03-01

    No analytical models seem to exist which are capable of investigating the relative effects of the physical urban landscape on the rates of leaf net photosynthesis in canopies. This paper deals with the results of the combination of two deterministic models: a multi-layered canopy leaf energy budget-photosynthesis model CANOPY and a complex, analytical street canyon energy budget model URBAN 3. Both models were validated previously. A range of three widely contrasting plant photosynthesis response systems (C3 and C4 plants) were chosen as well as were different latitudes, seasons, and urban morphologies. The results indicated both reductions and increases of relative photosynthesis and an almost linear correlation between relative sunlit area and relative net photosynthesis.

  9. Effect of forest canopy closure on incoming solar radiance

    NASA Technical Reports Server (NTRS)

    Dottavio, C. L. (Principal Investigator)

    1981-01-01

    In order to better understand the physical processes involved in defoliation assessment from remotely sensed data, a field study was designed to investigate the effect of forest canopy closure and other environmental variables on incoming solar radiation. Diffuse radiation measurements were recorded in red, infrared, and middle infrared wavelengths using the Mark 2 three band field radiometer. Results to date indicate that the percent canopy closure is the single most important variable affecting incoming solar radiation. In the visible and near infrared regions, interaction between time of day and date (defined later as solar zenith angle) also affect radiometric response. Aspect has only limited influence on radiance response. These same variables do not influence middle infrared response, however. Uniformity of the forest canopy appears to be more important. These results are compared to LANDSAT MSS classification results of gypsy moth defoliation.

  10. Effect of forest canopy closure on incoming solar radiance

    SciTech Connect

    Dottavio, C.L.

    1981-04-01

    In order to better understand the physical processes involved in defoliation assessment from remotely sensed data, a field study was designed to investigate the effect of forest canopy closure and other environmental variables on incoming solar radiation. Diffuse radiation measurements were recorded in red, infrared, and middle infrared wavelengths using the Mark 2 three band field radiometer. Results to date indicate that the percent canopy closure is the single most important variable affecting incoming solar radiation. In the visible and near infrared regions, interaction between time of day and date (defined later as solar zenith angle) also affect radiometric response. Aspect has only limited influence on radiance response. These same variables do not influence middle infrared response, however. Uniformity of the forest canopy appears to be more important. These results are compared to LANDSAT MSS classification results of gypsy moth defoliation.

  11. Effects of vegetation canopy on the radar backscattering coefficient

    NASA Technical Reports Server (NTRS)

    Mo, T.; Blanchard, B. J.; Schmugge, T. J.

    1983-01-01

    Airborne L- and C-band scatterometer data, taken over both vegetation-covered and bare fields, were systematically analyzed and theoretically reproduced, using a recently developed model for calculating radar backscattering coefficients of rough soil surfaces. The results show that the model can reproduce the observed angular variations of radar backscattering coefficient quite well via a least-squares fit method. Best fits to the data provide estimates of the statistical properties of the surface roughness, which is characterized by two parameters: the standard deviation of surface height, and the surface correlation length. In addition, the processes of vegetation attenuation and volume scattering require two canopy parameters, the canopy optical thickness and a volume scattering factor. Canopy parameter values for individual vegetation types, including alfalfa, milo and corn, were also determined from the best-fit results. The uncertainties in the scatterometer data were also explored.

  12. Remote sensing of vegetation canopy photosynthetic and stomatal conductance efficiencies

    NASA Technical Reports Server (NTRS)

    Myneni, R. B.; Ganapol, B. D.; Asrar, G.

    1992-01-01

    The problem of remote sensing the canopy photosynthetic and stomatal conductance efficiencies is investigated with the aid of one- and three-dimensional radiative transfer methods coupled to a semi-empirical mechanistic model of leaf photosynthesis and stomatal conductance. Desertlike vegetation is modeled as clumps of leaves randomly distributed on a bright dry soil with partial ground cover. Normalized difference vegetation index (NDVI), canopy photosynthetic (Ep), and stomatal efficiencies (Es) are calculated for various geometrical, optical, and illumination conditions. The contribution of various radiative fluxes to estimates of Ep is evaluated and the magnitude of errors in bulk canopy formulation of problem parameters are quantified. The nature and sensitivity of the relationship between Ep and Es to NDVI is investigated, and an algorithm is proposed for use in operational remote sensing.

  13. Characterizing tree canopy temperature heterogeneity using an unmanned aircraft-borne thermal imager

    NASA Astrophysics Data System (ADS)

    Messinger, M.; Powell, R.; Silman, M.; Wright, M.; Nicholson, W.

    2013-12-01

    each site. Emissivity was assumed to be 0.98 for all species. Acquired images had a pixel resolution of <3 cm and measurement accuracy of ×1° C. We found the UAS-borne TIR imaging system to be an effective tool for collection of high resolution canopy imagery. The system imaged all targeted crowns quickly and reliably, providing a viable alternative to current methods of canopy Tleaf measurement. Analysis of the imagery indicated significant variability in Tleaf both within and between crowns. We identified trends in Tleaf related to average leaf size, shape, and crown structural traits. These data on the heterogeneity of Tleaf can further our understanding of canopy-atmosphere energy exchange. This pilot study demonstrates the promise of UAS-borne TIR sensors for acquiring high spatial resolution imagery at the scale of individual tree crowns.

  14. Spatial Patterns of Soil Organic Carbon Relative to Tree Size and Canopy Distribution in a Semi-Desert Grassland

    NASA Astrophysics Data System (ADS)

    Throop, H. L.; Archer, S.

    2004-12-01

    The abundance of woody species in grasslands and savannas has increased globally over the past century. Recent estimates suggest that this proliferation of woody plants may account for a significant fraction of the Northern Hemisphere C sink, although a large degree of uncertainty exists in the magnitude and spatial distribution of these plant and soil pools. While field-based inventories have made progress in assessing the role of aboveground woody growth in ecosystem C inventories, the effect of woody proliferation on soil organic carbon (SOC) remains controversial, despite the fact that the majority of ecosystem C in these systems is typically belowground. Elevated levels of SOC underneath woody plant canopies have been widely reported, but little is known about the spatial distribution of SOC relative to tree canopies. Understanding the spatial distribution of SOC is critical, however, to developing accurate landscape-scale assessments of woody proliferation impacts on ecosystem C pools. We quantified the influence of encroaching mesquite trees (Fabaceae: Prosopis velutina) on the concentration of SOC and total nitrogen (TN) in a semi-desert grassland in southern Arizona. SOC concentrations near the boles of large trees (basal diameter 85-102 cm) were approximately double that of SOC in intercanopy zones (0.9% vs. 0.4% SOC by weight). SOC declined moving out from the bole to the canopy edge, at which point it was equivalent to inter-canopy spaces. Small to medium-sized trees (basal diameters less than 85 cm) had minimal influence on SOC concentrations. Patterns of TN values mirrored those of SOC in all cases, although TN values were roughly an order of magnitude lower than SOC values. These data suggest that accurate accounting of landscape-level SOC stocks will require developing area-weighting algorithms that account for tree size and bole-to-canopy gradients.

  15. The efficient urban canopy dependency parametrization (SURY) v1.0 for atmospheric modelling: description and application with the COSMO-CLM model for a Belgian summer

    NASA Astrophysics Data System (ADS)

    Wouters, Hendrik; Demuzere, Matthias; Blahak, Ulrich; Fortuniak, Krzysztof; Maiheu, Bino; Camps, Johan; Tielemans, Daniël; van Lipzig, Nicole P. M.

    2016-09-01

    This paper presents the Semi-empirical URban canopY parametrization (SURY) v1.0, which bridges the gap between bulk urban land-surface schemes and explicit-canyon schemes. Based on detailed observational studies, modelling experiments and available parameter inventories, it offers a robust translation of urban canopy parameters - containing the three-dimensional information - into bulk parameters. As a result, it brings canopy-dependent urban physics to existing bulk urban land-surface schemes of atmospheric models. At the same time, SURY preserves a low computational cost of bulk schemes for efficient numerical weather prediction and climate modelling at the convection-permitting scales. It offers versatility and consistency for employing both urban canopy parameters from bottom-up inventories and bulk parameters from top-down estimates. SURY is tested for Belgium at 2.8 km resolution with the COSMO-CLM model (v5.0_clm6) that is extended with the bulk urban land-surface scheme TERRA_URB (v2.0). The model reproduces very well the urban heat islands observed from in situ urban-climate observations, satellite imagery and tower observations, which is in contrast to the original COSMO-CLM model without an urban land-surface scheme. As an application of SURY, the sensitivity of atmospheric modelling with the COSMO-CLM model is addressed for the urban canopy parameter ranges from the local climate zones of http://WUDAPT.org. City-scale effects are found in modelling the land-surface temperatures, air temperatures and associated urban heat islands. Recommendations are formulated for more precise urban atmospheric modelling at the convection-permitting scales. It is concluded that urban canopy parametrizations including SURY, combined with the deployment of the WUDAPT urban database platform and advancements in atmospheric modelling systems, are essential.

  16. Gross nitrogen retranslocation within a canopy of Quercus serrata saplings.

    PubMed

    Ueda, Miki U

    2012-07-01

    Nitrogen (N) retranslocation within tree canopies has been intensively studied and assumed to function as a one-way process (e.g., from older to newer leaves). However, recent studies have found that both N output and input occur in individual leaves, suggesting that 'gross' N retranslocation exists behind 'net' N retranslocation. In the present study, the amount and direction of gross N retranslocation within a canopy of deciduous oak Quercus serrata Thunb. ex. Murray saplings were investigated. Labeling was conducted with leaves of Q. serrata saplings cultivated under conditions of low-N (LN) or high-N (HN) fertility. Subsequently, N movement within the canopy was traced. Leaves at two different positions in the canopy (top and lateral) were labeled to determine the direction of gross N retranslocation. To detect seasonal differences, the leaf-labeling experiment was conducted twice during the early and late phases of the growing season. In addition, to compare the quantitative importance of gross N retranslocation and root N uptake, the latter was determined by labeling Q. serrata roots. The N-labeling experiment revealed gross N retranslocation among leaves, i.e., from top to lateral, lateral to top and lateral to lateral positions. Gross N retranslocation was quantitatively more important than root uptake, especially for plants cultivated at LN fertility. Season also affected the amount of gross N retranslocation, and these effects differed between LN and HN fertilities. These findings suggest that N allocation within a canopy is controlled dynamically by both gross N output and input. The mechanisms controlling gross N output and input likely function as key determinants of N allocation within a tree canopy.

  17. Convergent elevation trends in canopy chemical traits of tropical forests.

    PubMed

    Asner, Gregory P; Martin, Roberta E

    2016-06-01

    The functional biogeography of tropical forests is expressed in foliar chemicals that are key physiologically based predictors of plant adaptation to changing environmental conditions including climate. However, understanding the degree to which environmental filters sort the canopy chemical characteristics of forest canopies remains a challenge. Here, we report on the elevation and soil-type dependence of forest canopy chemistry among 75 compositionally and environmentally distinct forests in nine regions, with a total of 7819 individual trees representing 3246 species collected, identified and assayed for foliar traits. We assessed whether there are consistent relationships between canopy chemical traits and both elevation and soil type, and evaluated the general role of phylogeny in mediating patterns of canopy traits within and across communities. Chemical trait variation and partitioning suggested a general model based on four interconnected findings. First, geographic variation at the soil-Order level, expressing broad changes in fertility, underpins major shifts in foliar phosphorus (P) and calcium (Ca). Second, elevation-dependent shifts in average community leaf dry mass per area (LMA), chlorophyll, and carbon allocation (including nonstructural carbohydrates) are most strongly correlated with changes in foliar Ca. Third, chemical diversity within communities is driven by differences between species rather than by plasticity within species. Finally, elevation- and soil-dependent changes in N, LMA and leaf carbon allocation are mediated by canopy compositional turnover, whereas foliar P and Ca are driven more by changes in site conditions than by phylogeny. Our findings have broad implications for understanding the global ecology of humid tropical forests, and their functional responses to changing climate.

  18. Spatial variability of leaf wetness duration in different crop canopies.

    PubMed

    Sentelhas, Paulo C; Gillespie, Terry J; Batzer, Jean C; Gleason, Mark L; Monteiro, José Eduardo B A; Pezzopane, José Ricardo M; Pedro, Mário J

    2005-07-01

    The spatial variability of leaf wetness duration (LWD) was evaluated in four different height-structure crop canopies: apple, coffee, maize, and grape. LWD measurements were made using painted flat plate, printed-circuit wetness sensors deployed in different positions above and inside the crops, with inclination angles ranging from 30 to 45 degrees. For apple trees, the sensors were installed in 12 east-west positions: 4 at each of the top (3.3 m), middle (2.1 m), and bottom (1.1 m) levels. For young coffee plants (80 cm tall), four sensors were installed close to the leaves at heights of 20, 40, 60, and 80 cm. For the maize and grape crops, LWD sensors were installed in two positions, one just below the canopy top and another inside the canopy. Adjacent to each experiment, LWD was measured above nearby mowed turfgrass with the same kind of flat plate sensor, deployed at 30 cm and between 30 and 45 degrees. We found average LWD varied by canopy position for apple and maize (P<0.05). In these cases, LWD was longer at the top, particularly when dew was the source of wetness. For grapes, cultivated in a hedgerow system and for young coffee plants, average LWD did not differ between the top and inside the canopy. The comparison by geometric mean regression analysis between crop and turfgrass LWD measurements showed that sensors at 30 cm over turfgrass provided quite accurate estimates of LWD at the top of the crops, despite large differences in crop height and structure, but poorer estimates for wetness within leaf canopies.

  19. A photosynthesis-based two-leaf canopy stomatal conductance model for meteorology and air quality modeling with WRF/CMAQ PX LSM

    EPA Science Inventory

    A coupled photosynthesis-stomatal conductance model with single-layer sunlit and shaded leaf canopy scaling is implemented and evaluated in a diagnostic box model with the Pleim-Xiu land surface model (PX LSM) and ozone deposition model components taken directly from the meteorol...

  20. Distribution of Carbon Uptake Capacity of Plant Functional Groups Across the Canopy Gradient in Old-Growth Tropical Wet Forest in Costa Rica

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Cruz, H. O.; Ryan, M. G.; Clark, D. B.; Clark, D. A.; Olivas, P.

    2004-12-01

    Because of the difficulties of accessing leaves within tree crowns, little is known about the photosynthetic capacity of different functional groups within tropical rain forest canopies. To address this deficiency, we measured photosynthetic capacity (Amax) in situ along vertical transects through old-growth forest canopy using a mobile walkup tower at the La Selva Biological Station in Costa Rica. We asked: What groups are responsible for most C-fixation and at what height in the canopy does most C-fixation occur? Photosynthesis (using a LI-COR Li-6400) and total leaf area were measured for all vascular plant species encountered within the tower footprint (4.6 m2). Plants were grouped into trees, palms, ferns, lianas, epiphytes, herbs, Pentaclethra macroloba (the dominant canopy tree), and vines. Amax values differed among functional groups. The ranking of Amax among the groups was trees > P. macroloba > palms > lianas > vines > epiphytes > herbs > ferns. Trees and P. macroloba had the highest photosynthetic rates, but the maximum rates occur at different heights. Amax of P. macroloba increases with canopy height to a maximum 10.3 \\mumol m-2 s-1 at 17.5 m. Amax of trees increases with canopy height (r2 = 0.77) and attains the highest Amax at 32.5 m (10.6 \\mumol m-2 s-1). Palms and lianas presented similar patterns of Amax. However, lianas reach the canopy top whereas palms are shorter and were not observed above 27.5 m. The maximum photosynthetic rates for both groups were: lianas 9.2 \\mumol m-2 s-1 at 27.5 m and palms 9.6 \\mumol m-2 s-1 at 17.5 m. By scaling the functional group Amax values with their leaf area, we estimated that most of the photosynthetic capacity occurs between 17.5 m and 37.5 m and is attributed mainly to trees, followed by P. macroloba and then lianas.

  1. Spatial variation of corn canopy temperature as dependent upon soil texture and crop rooting characteristics

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.

    1983-01-01

    A soil plant atmosphere model for corn (Zea mays L.) together with the scaling theory for soil hydraulic heterogeneity are used to study the sensitivity of spatial variation of canopy temperature to field averaged soil texture and crop rooting characteristics. The soil plant atmosphere model explicitly solves a continuity equation for water flux resulting from root water uptake, changes in plant water storage and transpirational flux. Dynamical equations for root zone soil water potential and the plant water storage models the progressive drying of soil, and day time dehydration and night time hydration of the crop. The statistic of scaling parameter which describes the spatial variation of soil hydraulic conductivity and matric potential is assumed to be independent of soil texture class. The field averaged soil hydraulic characteristics are chosen to be representative of loamy sand and clay loam soils. Two rooting characteristics are chosen, one shallow and the other deep rooted. The simulation shows that the range of canopy temperatures in the clayey soil is less than 1K, but for the sandy soil the range is about 2.5 and 5.0 K, respectively, for the shallow and deep rooted crops.

  2. Tight coupling of leaf area index to canopy nitrogen and phosphorus across heterogeneous tallgrass prairie communities.

    PubMed

    Klodd, Anne E; Nippert, Jesse B; Ratajczak, Zak; Waring, Hazel; Phoenix, Gareth K

    2016-11-01

    Nitrogen (N) and phosphorus (P) are limiting nutrients for many plant communities worldwide. Foliar N and P along with leaf area are among the most important controls on photosynthesis and hence productivity. However, foliar N and P are typically assessed as species level traits, whereas productivity is often measured at the community scale. Here, we compared the community-level traits of leaf area index (LAI) to total foliar nitrogen (TFN) and total foliar phosphorus (TFP) across nearly three order