The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
David B Clark - One of the best experts on this subject based on the ideXlab platform.
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diversity distribution and dynamics of large trees across an old growth lowland Tropical Rain Forest landscape
PLOS ONE, 2019Co-Authors: David B Clark, James R Kellner, Deborah A. Clark, Antonio Ferraz, Susan G Letcher, Sassan SaatchiAbstract:Large trees, here defined as ≥60 cm trunk diameter, are the most massive organisms in Tropical Rain Forest, and are important in Forest structure, dynamics and carbon cycling. The status of large trees in Tropical Forest is unclear, with both increasing and decreasing trends reported. We sampled across an old-growth Tropical Rain Forest landscape at the La Selva Biological Station in Costa Rica to study the distribution and performance of large trees and their contribution to Forest structure and dynamics. We censused all large trees in 238 0.50 ha plots, and also identified and measured all stems ≥10 cm diameter in 18 0.50 ha plots annually for 20 years (1997-2017). We assessed abundance, species diversity, and crown conditions of large trees in relation to soil type and topography, measured the contribution of large trees to stand structure, productivity, and dynamics, and analyzed the decadal population trends of large trees. Large trees accounted for 2.5% of stems and ~25% of mean basal area and Estimated Above-Ground Biomass, and produced ~10% of the estimated wood production. Crown exposure increased with stem diameter but predictability was low. Large tree density was about twice as high on more-fertile flat sites compared to less fertile sites on slopes and plateaus. Density of large trees increased 27% over the study interval, but the increase was restricted to the flat more-fertile sites. Mortality and recruitment differed between large trees and smaller stems, and strongly suggested that large tree density was affected by past climatic disturbances such as large El Nino events. Our results generally do not support the hypothesis of increasing biomass and turnover rates in Tropical Forest. We suggest that additional landscape-scale studies of large trees are needed to determine the generality of disturbance legacies in Tropical Forest study sites.
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pervasive canopy dynamics produce short term stability in a Tropical Rain Forest landscape
Ecology Letters, 2009Co-Authors: James R Kellner, David B Clark, Stephen P HubbellAbstract:A fundamental property of all Forest landscapes is the size frequency distribution of canopy gap disturbances. But characterizing Forest structure and changes at large spatial scales has been challenging and most of our understanding is from permanent inventory plots. Here we report the first application of light detection and ranging remote sensing to measurements of canopy disturbance and regeneration in an old-growth Tropical Rain Forest landscape. Pervasive local height changes figure prominently in the dynamics of this Forest. Although most canopy gaps recruited to higher positions during 8.5 years, size frequency distributions were similar at two points in time and well-predicted by power-laws. At larger spatial scales (hundreds of ha), height increases and decreases occurred with similar frequency and changes to canopy height that were analysed using a height transition matrix suggest that the distribution of canopy height at the beginning of the study was close to the projected steady-state equilibrium under the recent disturbance regime. Taken together, these findings show how widespread local height changes can produce short-term stability in a Tropical Rain Forest landscape.
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first direct landscape scale measurement of Tropical Rain Forest leaf area index a key driver of global primary productivity
Ecology Letters, 2007Co-Authors: David B Clark, Deborah A. Clark, Steven F Oberbauer, Michael G Ryan, Paulo C OlivasAbstract:Leaf Area Index (leaf area per unit ground area, LAI) is a key driver of Forest productivity but has never previously been measured directly at the landscape scale in Tropical Rain Forest (TRF). We used a modular tower and stratified random sampling to harvest all foliage from Forest floor to canopy top in 55 vertical transects (4.6 m 2 ) across 500 ha of old growth in Costa Rica. Landscape LAI was 6.00 ± 0.32 SEM. Trees, palms and lianas accounted for 89% of the total, and trees and lianas were 95% of the upper canopy. All vertical transects were organized into quantitatively defined strata, partially resolving the long-standing controversy over canopy stratification in TRF. Total LAI was strongly correlated with Forest height up to 21 m, while the number of canopy strata increased with Forest height across the full height range. These data are a benchmark for understanding the structure and functional composition of TRF canopies at landscape scales, and also provide insights for improving ecosystem models and remote sensing validation.
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small footprint lidar estimation of sub canopy elevation and tree height in a Tropical Rain Forest landscape
Remote Sensing of Environment, 2004Co-Authors: Matthew L Clark, David B Clark, Dar A RobertsAbstract:Meso-scale digital terRain models (DTMs) and canopy-height estimates, or digital canopy models (DCMs), are two lidar products that have immense potential for research in Tropical Rain Forest (TRF) ecology and management. In this study, we used a small-footprint lidar sensor (airborne laser scanner, ALS) to estimate sub-canopy elevation and canopy height in an evergreen Tropical Rain Forest. A fully automated, local-minima algorithm was developed to separate lidar ground returns from overlying vegetation returns. We then assessed inverse distance weighted (IDW) and ordinary kriging (OK) geostatistical techniques for the interpolation of a sub-canopy DTM. OK was determined to be a superior interpolation scheme because it smoothed fine-scale variance created by spurious understory heights in the ground-point dataset. The final DTM had a linear correlation of 1.00 and a root-mean-square error (RMSE) of 2.29 m when compared against 3859 well-distributed ground-survey points. In old-growth Forests, RMS error on steep slopes was 0.67 m greater than on flat slopes. On flatter slopes, variation in vegetation complexity associated with land use caused highly significant differences in DTM error distribution across the landscape. The highest DTM accuracy observed in this study was 0.58-m RMSE, under flat, open-canopy areas with relatively smooth surfaces. Lidar ground retrieval was complicated by dense, multi-layered evergreen canopy in old-growth Forests, causing DTM overestimation that increased RMS error to 1.95 m. A DCM was calculated from the original lidar surface and the interpolated DTM. Individual and plot-scale heights were estimated from DCM metrics and compared to field data measured using similar spatial supports and metrics. For old-growth Forest emergent trees and isolated pasture trees greater than 20 m tall, individual tree heights were underestimated and had 3.67- and 2.33-m mean absolute error (MAE), respectively. Linear-regression models explained 51% (4.15-m RMSE) and 95% (2.41-m RMSE) of the variance, respectively. It was determined that improved elevation and field-height estimation in pastures explained why individual pasture trees could be estimated more accurately than old-growth trees. Mean height of tree stems in 32 young agroForestry plantation plots (0.38 to 18.53 m tall) was estimated with a mean absolute error of 0.90 m (r 2 =0.97; 1.08-m model RMSE) using the mean of lidar returns in the plot. As in other small-footprint
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quantifying mortality of Tropical Rain Forest trees using high spatial resolution satellite data
Ecology Letters, 2004Co-Authors: David B Clark, Carlomagno Soto Castro, Luis Diego Alfaro Alvarado, Jane M ReadAbstract:Assessment of Forest responses to climate change is severely hampered by the limited information on tree death on short temporal and broad spatial scales, particularly in Tropical Forests. We used 1-m resolution panchromatic IKONOS and 0.7-m resolution QuickBird satellite data, acquired in 2000 and 2002, respectively, to evaluate tree death rates at the La Selva Biological Station in old-growth Tropical Wet Forest in Costa Rica, Central America. Using a calibration factor derived from ground inspection of tree deaths predicted from the images, we calculated a landscape-scale annual exponential death rate of 2.8%. This corresponds closely to data for all canopy-level trees in 18 Forest inventory plots, each of 0.5 ha, for a mostly-overlapping 2-year period (2.8% per year). This study shows that high-spatial-resolution satellite data can now be used to measure old-growth Tropical Rain Forest tree death rates, suggesting many new avenues for Tropical Forest ecology and global change research.
W. Sahle - One of the best experts on this subject based on the ideXlab platform.
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Single particle analysis of the accumulation mode aerosol over the northeast Amazonian Tropical Rain Forest, Surinam, South America
Atmospheric Chemistry and Physics, 2005Co-Authors: R. Krejci, J. StrÖm, M. De Reus, W. SahleAbstract:Single particle analysis of aerosols particles larger than 0.2 ?m diameter was performed on 24 samples collected over Surinam Tropical Rain Forest and in the adjacent marine boundary layer (MBL) during the LBA-CLAIRE 98 campaign in March 1998. Elemental composition and morphology of 2308 particles was determined using SEM-EDX. The aerosol particles were divided into seven groups according to their chemical composition: organic particles, mineral dust, aged mineral dust, sea salt, aged sea salt, Ca-rich, and biogenic aerosol. However the organic material in aerosol particles cannot be identified directly by SEM-EDX, we present indirect method of detection of organic material using this technique. Samples were further divided with respect to the distinct atmospheric layers present in the Tropical troposphere including MBL, continental mixed layer, cloud convective layer, free troposphere and region of deep convection outflow. The organic and mineral dust particles are two major groups observed over the RainForest. In the MBL also sea salt particles represented a large fraction between 15 and 27%. The organic particles control much of the chemical characteristic of the aerosol in the continental Tropical troposphere. Their abundance ranged from less than 20% in the MBL to more than 90% in the free troposphere between 4.5- and 12.6-km altitude. During the transport of the air masses from the MBL over the Rain Forest, fraction of organic aerosol particles more than doubled, reaching 40?60% in the continental boundary layer. This increase was attributed to direct emissions of biogenic aerosols from the Tropical vegetation. The high fraction of the organic accumulation mode particles in the upper Tropical troposphere could be a good indicator for the air masses originated over the Tropical Rain Forest.
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Single particle analysis of the accumulation mode aerosol over the northeast Amazonian Tropical Rain Forest, Surinam, South America
Atmospheric Chemistry and Physics Discussions, 2004Co-Authors: R. Krejci, J. StrÖm, M. De Reus, W. SahleAbstract:Single particle analysis of aerosols particles larger than 0.2 µm diameter was performed on 24 samples collected over Surinam Tropical Rain Forest and in the adjacent marine boundary layer (MBL) during the LBA-CLAIRE 98 campaign in March 1998. Elemental composition and morphology of 2308 particles was determined using SEM-EDX. The aerosol particles were divided into seven groups according to their chemical composition: organic particles, mineral dust, aged mineral dust, sea salt, aged sea salt, Ca-rich, and biogenic aerosol. Samples were further divided with respect to the distinct atmospheric layers present in the Tropical troposphere including MBL, continental mixed layer, cloud convective layer, free troposphere and region of deep convection outflow. The organic and mineral dust particles are two major groups observed over the RainForest. In the MBL also sea salt particles represented a large fraction between 15 and 27%. The organic particles control much of the chemical characteristic of the aerosol in the continental Tropical troposphere. Their abundance ranged from less than 20% in the MBL to more than 90% in the free troposphere between 4.5 and 12.6 km altitude. During the transport of the air masses from the MBL over the Rain Forest, fraction of organic aerosol particles more than doubled, reaching 40-60% in the continental boundary layer. This increase was attributed to direct emissions of biogenic aerosols from the Tropical vegetation. The high fraction of the organic accumulation mode particles in the upper Tropical troposphere could be a good indicator for the air masses originated over the Tropical Rain Forest.
R. Krejci - One of the best experts on this subject based on the ideXlab platform.
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Single particle analysis of the accumulation mode aerosol over the northeast Amazonian Tropical Rain Forest, Surinam, South America
Atmospheric Chemistry and Physics, 2005Co-Authors: R. Krejci, J. StrÖm, M. De Reus, W. SahleAbstract:Single particle analysis of aerosols particles larger than 0.2 ?m diameter was performed on 24 samples collected over Surinam Tropical Rain Forest and in the adjacent marine boundary layer (MBL) during the LBA-CLAIRE 98 campaign in March 1998. Elemental composition and morphology of 2308 particles was determined using SEM-EDX. The aerosol particles were divided into seven groups according to their chemical composition: organic particles, mineral dust, aged mineral dust, sea salt, aged sea salt, Ca-rich, and biogenic aerosol. However the organic material in aerosol particles cannot be identified directly by SEM-EDX, we present indirect method of detection of organic material using this technique. Samples were further divided with respect to the distinct atmospheric layers present in the Tropical troposphere including MBL, continental mixed layer, cloud convective layer, free troposphere and region of deep convection outflow. The organic and mineral dust particles are two major groups observed over the RainForest. In the MBL also sea salt particles represented a large fraction between 15 and 27%. The organic particles control much of the chemical characteristic of the aerosol in the continental Tropical troposphere. Their abundance ranged from less than 20% in the MBL to more than 90% in the free troposphere between 4.5- and 12.6-km altitude. During the transport of the air masses from the MBL over the Rain Forest, fraction of organic aerosol particles more than doubled, reaching 40?60% in the continental boundary layer. This increase was attributed to direct emissions of biogenic aerosols from the Tropical vegetation. The high fraction of the organic accumulation mode particles in the upper Tropical troposphere could be a good indicator for the air masses originated over the Tropical Rain Forest.
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Single particle analysis of the accumulation mode aerosol over the northeast Amazonian Tropical Rain Forest, Surinam, South America
Atmospheric Chemistry and Physics Discussions, 2004Co-Authors: R. Krejci, J. StrÖm, M. De Reus, W. SahleAbstract:Single particle analysis of aerosols particles larger than 0.2 µm diameter was performed on 24 samples collected over Surinam Tropical Rain Forest and in the adjacent marine boundary layer (MBL) during the LBA-CLAIRE 98 campaign in March 1998. Elemental composition and morphology of 2308 particles was determined using SEM-EDX. The aerosol particles were divided into seven groups according to their chemical composition: organic particles, mineral dust, aged mineral dust, sea salt, aged sea salt, Ca-rich, and biogenic aerosol. Samples were further divided with respect to the distinct atmospheric layers present in the Tropical troposphere including MBL, continental mixed layer, cloud convective layer, free troposphere and region of deep convection outflow. The organic and mineral dust particles are two major groups observed over the RainForest. In the MBL also sea salt particles represented a large fraction between 15 and 27%. The organic particles control much of the chemical characteristic of the aerosol in the continental Tropical troposphere. Their abundance ranged from less than 20% in the MBL to more than 90% in the free troposphere between 4.5 and 12.6 km altitude. During the transport of the air masses from the MBL over the Rain Forest, fraction of organic aerosol particles more than doubled, reaching 40-60% in the continental boundary layer. This increase was attributed to direct emissions of biogenic aerosols from the Tropical vegetation. The high fraction of the organic accumulation mode particles in the upper Tropical troposphere could be a good indicator for the air masses originated over the Tropical Rain Forest.
Stephen P Hubbell - One of the best experts on this subject based on the ideXlab platform.
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pervasive canopy dynamics produce short term stability in a Tropical Rain Forest landscape
Ecology Letters, 2009Co-Authors: James R Kellner, David B Clark, Stephen P HubbellAbstract:A fundamental property of all Forest landscapes is the size frequency distribution of canopy gap disturbances. But characterizing Forest structure and changes at large spatial scales has been challenging and most of our understanding is from permanent inventory plots. Here we report the first application of light detection and ranging remote sensing to measurements of canopy disturbance and regeneration in an old-growth Tropical Rain Forest landscape. Pervasive local height changes figure prominently in the dynamics of this Forest. Although most canopy gaps recruited to higher positions during 8.5 years, size frequency distributions were similar at two points in time and well-predicted by power-laws. At larger spatial scales (hundreds of ha), height increases and decreases occurred with similar frequency and changes to canopy height that were analysed using a height transition matrix suggest that the distribution of canopy height at the beginning of the study was close to the projected steady-state equilibrium under the recent disturbance regime. Taken together, these findings show how widespread local height changes can produce short-term stability in a Tropical Rain Forest landscape.
Michael G Ryan - One of the best experts on this subject based on the ideXlab platform.
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first direct landscape scale measurement of Tropical Rain Forest leaf area index a key driver of global primary productivity
Ecology Letters, 2007Co-Authors: David B Clark, Deborah A. Clark, Steven F Oberbauer, Michael G Ryan, Paulo C OlivasAbstract:Leaf Area Index (leaf area per unit ground area, LAI) is a key driver of Forest productivity but has never previously been measured directly at the landscape scale in Tropical Rain Forest (TRF). We used a modular tower and stratified random sampling to harvest all foliage from Forest floor to canopy top in 55 vertical transects (4.6 m 2 ) across 500 ha of old growth in Costa Rica. Landscape LAI was 6.00 ± 0.32 SEM. Trees, palms and lianas accounted for 89% of the total, and trees and lianas were 95% of the upper canopy. All vertical transects were organized into quantitatively defined strata, partially resolving the long-standing controversy over canopy stratification in TRF. Total LAI was strongly correlated with Forest height up to 21 m, while the number of canopy strata increased with Forest height across the full height range. These data are a benchmark for understanding the structure and functional composition of TRF canopies at landscape scales, and also provide insights for improving ecosystem models and remote sensing validation.
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wood co2 efflux in a primary Tropical Rain Forest
Global Change Biology, 2006Co-Authors: Molly A Cavaleri, Steven F Oberbauer, Michael G RyanAbstract:The balance between photosynthesis and plant respiration in Tropical Forests may substantially affect the global carbon cycle. Woody tissue CO2 efflux is a major component of total plant respiration, but estimates of ecosystem-scale rates are uncertain because of poor sampling in the upper canopy and across landscapes. To overcome these problems, we used a portable scaffolding tower to measure woody tissue CO2 efflux from ground level to the canopy top across a range of sites of varying slope and soil phosphorus content in a primary Tropical Rain Forest in Costa Rica. The objectives of this study were to: (1) determine whether to use surface area, volume, or biomass for modeling and extrapolating wood CO2 efflux, (2) determine if wood CO2 efflux varied seasonally, (3) identify if wood CO2 efflux varied by functional group, height in canopy, soil fertility, or slope, and (4) extrapolate wood CO2 efflux to the Forest. CO2 efflux from small diameter woody tissue (o10cm) was related to surface area, while CO2 efflux from stems 410cm was related to both surface area and volume. Wood CO2 efflux showed no evidence of seasonality over 2 years. CO2 efflux per unit wood surface area at 251 (FA) was highest for the N-fixing dominant tree species Pentaclethra macroloba, followed by other tree species, lianas, then palms. Small diameter FA increased steeply with increasing height, and large diameter FA increased with diameter. Soil phosphorus and slope had slight, but complex effects on FA. Wood CO2 efflux per unit ground area was 1.34 � 0.36lmolm � 2 s � 1 , or 508 � 135gCm � 2 yr � 1 . Small diameter wood, only 15% of total woody biomass, accounted for 70% of total woody tissue CO2 efflux from the Forest; while lianas, only 3% of total woody biomass, contributed one-fourth of the total wood CO2 efflux.
