Deborah A Clark

• Ph.D.
• Professor (Associate) at University of Missouri–St. Louis

High abundance of trees capable of biological N-fixation (henceforth “N-fixers”) in tropical forests has been hypothesized to drive higher stream nitrate (NO3) concentrations compared to temperate counterparts. However, to date there have been no empirical linkages of stream NO3 concentrations with the productivity of tropical forests. Here, we com...

NASAs Global Ecosystem Dynamics Investigation (GEDI) is collecting space-borne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDIs footprint-level (~25 m) AGBD (GEDI04_A) product, including a descript...

is collecting spaceborne full waveform lidar data with a primary science goal of producing accurate estimates of forest aboveground biomass density (AGBD). This paper presents the development of the models used to create GEDI's footprint-level (~25 m) AGBD (GEDI04_A) product, including a description of the datasets used and the procedure for final...

Yearly changes in tropical carbon‐cycling have been a major biotic determinant of the interannual variation in the rise of atmospheric carbon dioxide ([CO2]). The environmental responses underlying these changes remain poorly understood. A 21‐year field study (1997–2018) in a Costa Rican rainforest has produced the first multi‐decade record of land...

The distribution of canopy heights in tropical rain forests directly affects carbon storage and the maintenance of biodiversity. We report results from a unique 20‐yr record of annual monitoring of canopy‐height distributions across an old‐growth tropical rain forest landscape at the La Selva Biological Station in Costa Rica. Canopy heights to 15 m...

The area of tropical secondary forests is increasing rapidly, but data on the physical and biological structure of the canopies of these forests are limited. To obtain such data and to measure the ontogeny of canopy structure during tropical rainforest succession, we studied patch-scale (5 m²) canopy structure in three areas of 18–36 year-old secon...

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 a...

In lowland tropical rainforest, hundreds of tree species typically occur within mesoscale landscapes (50‐500 ha). There is no consensus ecological theory that accounts for the coexistence of so many species with similar morphologies and the same fundamental requirements of light, nutrients, water, and physical space. In part this is due to the limi...

For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely...

Have tropical rain forest landscapes changed directionally through recent decades? To answer this question requires tracking forest structure and dynamics through time and across within-forest environmental heterogeneity. While the impacts of major environmental gradients in soil nutrients, climate and topography on lowland tropical rain forest (TR...

Turnover. Mean rates of turnover ± 1 S.E.M. for old growth forest in 18 0.50 ha plots at the La Selva Biological Station, Costa Rica. (TIF)

CARBONO plots static structure data. CARBONO plot stem inventory data 1997–2014 for 18 0.5 ha plots in old-growth Tropical Wet Forest at the La Selva Biological Station, Costa Rica. (CSV)

Multidecadal trends in recruitment. Multidecadal trends in recruitment in old-growth forests on residual and alluvial soils at the La Selva Biological Station, Costa Rica. Data from 1969–1982 are from OTS Plot 1 (4.4 ha, alluvial soil) and OTS Plot 3 (4.0 ha, residual soil) [17]). Data from 1997 onward are from the 6 0.5 ha CARBONO Project plots on...

Stem density through time in three different edaphic conditions. Mean stem density in 18 0.50 ha plot in three edaphic conditions ±1 S.E.M. (TIF)

CARBONO plot growth data. CARBONO plot stem growth data 1997–2014 for 18 0.5 ha plots in old-growth Tropical Wet Forest at the La Selva Biological Station, Costa Rica. (CSV)

Location of CARBONO project forest inventory plots. Locations of the 18 0.50 ha 50 x 100 m permanent forest inventory plots at the La Selva Biological Station, Puerto Viejo de Sarapiquí, Costa Rica. Plots were sited with a stratified random design within three principal upland landscape units: flat sites on old alluvial soils (plots shown in tan),...

Estimated basal area by edaphic condition. Mean basal area (±1 S.E.M.) in three different landscape types at the La Selva Biological Station, Costa Rica. N = 6 0.50 ha plots per edaphic category. (TIF)

Recruitment. Mean rates of recruitment ± 1 S.E.M. for old growth forest in 18 0.50 ha plots at the La Selva Biological Station, Costa Rica. (TIF)

For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely...

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and...

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and...

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approx...

1.Successional gradients are ubiquitous in nature, yet few studies have systematically examined the evolutionary origins of taxa that specialize at different successional stages. Here we quantify successional habitat specialization in Neotropical forest trees and evaluate its evolutionary lability along a precipitation gradient. Theoretically, succ...

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approx...

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher’s alpha and an approx...

Young secondary forests and plantations in the moist tropics often have rapid rates of biomass accumulation and thus sequester large amounts of carbon. Here, we compare results from mature forest and nearby 15-20 year old tree plantations in lowland Costa Rica to evaluate differences in allocation of carbon to aboveground production and root system...

Tropical rainforests have experienced major episodes of severe heat and drought in recent decades, and climate models project a warmer and potentially drier tropical climate over this century. But likely responses of tropical rainforests are poorly understood due to a lack of frequent long-term measurements of forest structure and dynamics. We anal...

A directional change in tropical-forest productivity, a large component in the global carbon budget, would affect the rate of increase in atmospheric carbon dioxide ([CO2]). One current hypothesis is that “CO2 fertilization” has been increasing tropical forest productivity. Some lines of evidence instead suggest climate-driven productivity declines...

In this study, we investigated whether landscape-scale variation of soil P accounts for 13 C and 15 N composition of detrital invertebrates in a lowland tropical rain forest in Costa Rica. The top 10-cm soil, leaf-litter samples and plant foliage were collected among 18 plots representing a threefold soil P gradient during 2007–2009. Body tissue of...

Tree species richness in a tropical rain forest typically exceeds several hundred species over mesoscale landscapes. There is no generally accepted ecological theory that accounts for the coexistence of so many species with the same general morphologies and the same basic requirements of light, nutrients, water, and physical space. In part this lac...

Relations between crown width and tree height and trunk diameter and tree height were measured for trees of all sizes of six large emergent species (Balizia elegans, Dipteryx panamensis, Hieronyma alchorneoides, Hymenolobium mesoamericanum, Lecythis ampla and Terminalia oblonga) in the lowland tropical wet forest at La Selva, Costa Rica. Thirty to...

Bioavailable P is recognized as a major constraint on productivity in many tropical rain forests. Nevertheless, insufficient knowledge about short-term temporal patterns in soil labile P limits our understanding of the mechanisms controlling soil P supply in tropical forest soils. The use of field-deployed anion exchange resin membranes (AEMs) to d...

Background/Question/Methods How tropical-forest net primary productivity (NPP) responds to climate change will have large implications for the biome’s rich biota and for the global carbon budget. Current global vegetation process models project declining tropical-forest NPP with higher temperatures and increased drought stress; however, such mode...

Background/Question/Methods: The responses of tropical rain forest (TRF) landscapes to changing global climate will have major impacts on global carbon cycling and biodiversity conservation. Meta-analyses of TRF forest inventory plots in old growth have suggested the following changes are already underway: increased rates of mortality and recruitme...

Both within and between species, leaf physiological parameters are strongly related to leaf dry mass per area (LMA, g/m2), which has been found to increase from forest floor to canopy top in every forest where it has been measured. Although vertical LMA gradients in forests have historically been attributed to a direct phenotypic response to light,...

Analyses relating long-term records of tree growth to interannual climatic variation at La Selva, Costa Rica have revealed marked forest sensitivities to both temperature and dry-season intensity (Clark et al. 2010). The tropical-forest biome is certain to become warmer, and many areas may become drier. Testing the generality of the La Selva findin...

In tropical rain forests, rates of forest turnover and tree species' life-history differences are shaped by the life expectancy of trees and the time taken by seedlings to reach the canopy. These measures are therefore of both theoretical and applied interest. However, the relationship between size, age, and life expectancy is poorly understood. In...

Background/Question/Methods The nearterm fate of the enormous quantities of carbon stored by tropical rain forests will have substantial impacts on the global carbon cycle and on future climate change. Three drivers of change in carbon stocks of tropical forests are increasing temperature and drought intensity (negative impacts) and increasing atm...

Background/Question/Methods In tropical rain forests, the density of arthropods in the detrital food web is predicted by the biomass of detritus and the abundance of limiting nutrients, usually P. The trophic structure of this food web is likely to respond to spatial differences in biomass and nutrient inputs, and here we test competing models tha...

Increased atmospheric [CO2] could theoretically lead to increased forest productivity (‘CO2 fertilization’). This mechanism was hypothesized as a possible explanation for biomass increases reported from tropical forests in the last 30+ years. We used unique long-term records of annually measured stands (eighteen 0.5 ha plots, 10 years) and focal tr...

The nutritional demands of animals vary by taxon. Across landscapes, communities of animals experience variability in the stoichiometry of carbon and nutrients within their resource base. Thus, we expect stoichiometry to contribute to the spatial variance in the demographic parameters of animal communities. Here, we measure how the composition of a...

Estimation of tree growth is generally based on repeated diameter measurements. A buttress at the height of measurement will lead to overestimates of tree diameter. Because buttresses grow up the trunk through time, it has become common practice to increase the height of measurement, to ensure that measurements remain above the buttress. However, t...

Litter-induced pulses of nutrient availability could play an important role in the productivity and nutrient cycling of forested ecosystems, especially tropical forests. Tropical forests experience such pulses as a result of wet-dry seasonality and during major climatic events, such as strong El Niños. We hypothesized that (1) an increase in the qu...

Background/Question/Methods Because tropical rain forests store globally-significant amounts of carbon and annually process vast quantities of CO2, the response of this biome to climate change can strongly influence the rate of planetary warming. Understanding the relation between forest productivity and climate variation in tropical forests has re...

The relationship between phenology and tree stem diameter increment is largely unexplored in tropical species, especially in wet tropical forests. To explore links between these phenomena, we measured stem diameter increment and phenology of ten canopy tree species from a range of functional types in the Atlantic lowlands of Costa Rica to test for...

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 50...

Understanding the dependency of ecosystem processes on spatial and temporal scales is crucial in current efforts to model ecosystem responses to global change. Here we present a case of nonlinear interactions between temporal and spatial scales in a high spatial- and temporal-resolution study of fine-root biomass responses to edaphic and climatic v...

Tropical rain forests are one of the most productive ecosystems in the world and play a significant role in the global carbon budget. Changes in phosphorus cycling dynamics as a result of on-going climate change have the potential to limit productivity in this ecosystem. Our objective was to determine hourly patterns in labile soil phosphorus throu...

The stoichiometry of resources may explain bottom-up regulation of higher trophic levels. We tested the effects of soil and litter nutrient stoichiometry on the invertebrate litter fauna of a Costa Rican tropical rain forest. Animal densities were estimated from 15 sites across a phosphorus gradient. The density of the invertebrate litter fauna var...

Because of tropical forests' disproportionate importance for world biodiversity and for the global carbon cycle, we urgently need to understand any effects on these ecosystems from the ongoing changes in climate and atmosphere. This review, intended to complement existing data reviews on this topic, focuses on three major classes of challenges that...

Recent projections of climatic change have focused a great deal of scientific and public attention on patterns of carbon (C) cycling as well as its controls, particularly the factors that determine whether an ecosystem is a net source or sink of atmospheric carbon dioxide (CO2). Net ecosystem production (NEP), a central concept in C-cycling researc...

We investigated the influence of landscape-level variation in soil fertility and topographic position on leaf litter nutrient dynamics in a tropical rain forest in Costa Rica. We sampled across the three main edaphic conditions (ultisol slope, ultisol plateau, and inceptisol) to determine the effect of soil nutrients on leaf litter nutrient concent...

The goal of this long-term research has been to assess the relationship between annually measured tree performance and microsite conditions for nine canopy and emergent tree species in old-growth lowland tropical rain forest. The study site, the La Selva Biological Station in northeast Costa Rica, is tropical wet forest (annual mean precipitation 4...

We used strontium isotopes and analysis of foliar and soil nutrients to test whether erosion can rejuvenate the supply of rock-derived nutrients in the lowland tropical rain forest of La Selva, Costa Rica. We expected that these nutrients would be depleted from soils on stable surfaces, a result of over one million years of weathering in situ. In f...

By assessing current leaf litter nutrient dynamics, we may be able to predict responses of nutrient cycling in tropical ecosystems to future environmental change. The goal of this study was to assess whether nutrient cycling is related to seasonal variation in rainfall in a wet tropical forest. We examined leaf litter of an old-growth tropical rain...

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 towe...

Disjunct eddy covariance in conjunction with continuous in-canopy gradient measurements allowed for the first time to quantify the fine-scale source and sink distribution of some of the most abundant biogenic (isoprene, monoterpenes, methanol, acetaldehyde, and acetone) and photooxidized (MVK+MAC, acetone, acetaldehyde, acetic, and formic acid) VOC...

1 Symbiotic arbuscular mycorrhizal (AM) fungi produce a recalcitrant AM-specific glycoprotein, glomalin, which could be a substantial contributor to soil carbon (C). In this study we made a first assessment of the standing stocks of glomalin in a tropical lowland rain forest (the La Selva Biological Station, Costa Rica) and tested whether glomalin...

How tropical rainforests are responding to the ongoing global changes in atmospheric composition and climate is little studied and poorly understood. Although rising atmospheric carbon dioxide (CO2) could enhance forest productivity, increased temperatures and drought are likely to diminish it. The limited field data have produced conflicting views...

The world's tropical forests take up and emit large amounts of carbon (C) through photosynthesis and respiration. Their response to global changes in the atmosphere and climate could therefore act as a feedback. Only recently has research been focused on the possibility that tropical forests may not be in C balance. There is currently a vigorous de...

Understanding the current status of the world's tropical rain forests (TRF) can be greatly advanced by global coverage of remotely sensed data at the scale of individual tree crowns. In 1999 the IKONOS satellite began offering worldwide 1-m panchromatic and 4-m multispectral data. Here we show that these data can be used to address diverse aspects...

Clark, D.B, J.M. Read, M.L. Clark, A. Murillo Cruz, M. Fallas Dotti & D.A. Clark. 2004. Application of 1-m and 4-m resolution satellite data to studies of tree demography, stand structure and land use classification in tropical rain forest landscapes. Ecological Applications 14:61-74.

In an old-growth tropical wet forest at La Selva, Costa Rica, we combined radiocarbon (C-14) dating and tree-ring analysis to estimate the ages of large trees of canopy and emergent species spanning a broad range of wood densities and growth rates. We collected samples from the trunks, of 29 fallen, dead individuals. We found that all eight sampled...

In an old-growth tropical wet forest at La Selva, Costa Rica, we combined radiocarbon (14C) dating and tree-ring analysis to estimate the ages of large trees of canopy and emergent species spanning a broad range of wood densities and growth rates. We collected samples from the trunks of 29 fallen, dead individuals. We found that all eight sampled s...

Contrary to large areas in Amazonia of tropical moist forests with a pronounced dry season, tropical wet forests in Costa Rica do not depend on deep roots to maintain an evergreen forest canopy through the year. At our Costa Rican tropical wet forest sites, we found a large carbon stock in the subsoil of deeply weathered Oxisols, even though only 0...

During 1984-2000, canopy tree growth in old-growth tropical rain forest at La Selva, Costa Rica, varied >2-fold among years. The trees' annual diameter increments in this 16-yr period were negatively correlated with annual means of daily minimum temperatures. The tree growth variations also negatively covaried with the net carbon exchange of the te...

Allocation of C to belowground plant structures is one of the most important, yet least well quantified fluxes of C in terrestrial ecosystems. In a literature review of mature forests worldwide, Raich and Nadelhoffer (1989) suggested that total belowground carbon allocation (TBCA) could be estimated from the difference between annual rates of soil...

Twenty common plant species were screened for emissions of biogenic volatile organic compounds (BVOCs) at a lowland tropical wet forest site in Costa Rica. Ten of the species examined emitted substantial quantities of isoprene. These species accounted for 35–50% of the total basal area of old-growth forest on the major edaphic site types, indicatin...

Large pieces of standing or fallen dead wood, known as coarse woody debris (CWD), play important roles in temperate forest carbon and nutrient cycles, and affect the abundance and distribution of many classes of organisms. CWD biomass and inputs are poorly documented in tropical rain forests (TRF), and the causes for their variation at landscape-sc...

In a recent (1998) publication of Science, data from a large number of forest inventory plots were used to estimate biomass trends in old-growth tropical forests. Al-though no evidence was found of net biomass change in mature Paleotropical forests, old growth of the humid Neotropics was inferred to have been a substantial biomass carbon sink in re...

There is still limited understanding of the processes underlying forest dy- namics in the world's tropical rain forests, ecosystems of disproportionate importance in terms of global biogeochemistry and biodiversity. Particularly poorly documented are the nature and time scale of upward height growth during regeneration by the tree species in these...

There are pressing reasons for developing a better understanding of net primary production (NPP) in the world's forests. These ecosystems play a large role in the world's carbon budget, and their dynamics, which are likely to be responding to global changes in climate and atmospheric composition, have major economic implications and impacts on glob...

Information on net primary production in tropical forests is needed for the development of realistic global carbon budgets, for projecting how these ecosystems will be affected by climatic and atmospheric changes, and for evaluating eddy covariance mea- surements of tropical forest carbon flux. However, a review of the database commonly used to add...

A better understanding of the reasons for variation in tropical rain forest (TRF) structure is important for quantifying global above-ground biomass (AGBM). We used three data sets to estimate stem number, basal area, and AGBM over a 600-ha old-growth TRF landscape (La Selva, N.E. Costa Rica). We analyzed the effects of soil type, slope angle, topo...

Tree species richness is remarkably high in many tropical forests, even at very fine spatial scales. However, the study of fine-scale richness is complicated by the rarefaction effect: that is, a trivial correlation between the number of individuals and the number of species. We developed null models to test whether fine-scale species richness diff...

The goal of this long-term research has been to assess the relationship between annually measured tree performance and microsite conditions for nine canopy and emergent tree species in old-growth lowland tropical rain forest. The study site, the La Selva Biological Station in northeast Costa Rica, is tropical wet forest (annual mean precipitation 4...

Tropical rain forests have the highest tree diversity on earth. Nonrandom spatial distributions of these species in relation to edaphic factors could be one mechanism responsible for maintaining this diversity. We examined the prevalence of nonrandom dis-tributions of trees and palms in relation to soil type and topographic position (''edaphic bias...

Growth performance was assessed for a diverse suite of canopy and emergent tree species in a lowland neotropical rain forest (the La Selva Biological Station, north-eastern Costa Rica). Species were evaluated based on annual diameter measurements of large samples of individuals in all post-seedling size classes, over a 12-yr period. The study speci...

Light fluctuations and crown traits were studied for saplings of four tree species in a Costa Rican rain forest. Light fluctuations (1988–1994) were assessed by annual light estimations above saplings, using a visual crown position index. Crown traits in 1994 and growth between 1994 and 1995 were measured. Crown position values varied between 1.5 a...

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1 Do local edaphic factors over short environmental gradients affect the distribution and abundance of tree species in tropical rain forests? We addressed this question by examining the responses of tree species to soil type, topographic position and slope angle in an upland old-growth tropical rain forest landscape in Costa Rica, Central America....

How are tree species within tropical rainforests distributed at the landscape scale? One research site, the La Selva Biological Station in Costa Rica, offers exceptional tools for addressing this question: a documented flora, soil and topographic maps. a reserve-wide grid, and a Geographical Information System (CIS). My colleagues and I have combin...

Knowledge of the amount of carbon in the environment, especially in the form of carbon dioxide, is important for understanding global climate change. Old-growth forests in particular have been thought to be steady-state systems in which carbon uptake is balanced by carbon emission. In their Perspective, Keller et al . discuss a recent article by Gr...

Light is a key resource controlling tree regeneration in the understory of closed-canopy old-growth forests. To evaluate the distribution of understory light environments at a landscape scale, we used stratified random sampling in a 500-ha stand of Costa Rican tropical rain forest. Fifteen 100 m long transects were placed using random coordinates w...

Very large trees, arbitrarily defined as those over 70 cm diameter above buttresses, account for a major portion of the above-ground biomass in neotropical rain forests. Owing to the scarcity of individuals of a given species and the difficulty of accurate measurement, there are few species-level data on the growth, mortality, and abundance of spec...