Questions: Which factors affect the diversity and species composition of tropical secondary rain forests in a region with little information regarding their contribution to global biodiversity? Can older secondary forests approach the... more
Questions: Which factors affect the diversity and species composition of tropical secondary rain forests in a region with little information regarding their contribution to global biodiversity? Can older secondary forests approach the diversity and composition of mature forests following 100 yr of pasture use? Location: Tropical secondary rain forest, northeast Australia. Methods: We identified trees, shrubs and vines ≥2.5 cm DBH in a chronosequence comprising 33 sites, aged 3–60 yr since the formation of closed canopy (9–69 yr since pasture abandonment) and compared them with eight sites in nearby mature forest remnants. Results: Species richness and community composition were strongly influenced by secondary forest age but did not attain values of mature forest. Sites in close proximity to mature forests had higher plant richness, whereas low soil fertility appeared to depress species recruitment. Thus, multiple factors operated in secondary forest community assembly. Unusual tree community patterns that suggest accelerated or slowed successional trajectories were observed at several sites. Conclusions: Secondary forests in our study region contained important plant diversity for conservation, particularly in older sites, however, even the oldest secondary forests (60 yr) did not converge with the species composition and diversity of mature forests. The protection of mature forest tracts and remnants must be a priority if we are to maintain high levels of plant diversity in tropical landscapes, conserve rare species and facilitate the recruitment of plant species in recovering forests.
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Habitat loss and fragmentation are a key threat to the survival of several small carnivore species in Southeast Asia. Enhancing habitat connectivity is therefore an important conservation strategy. In Peninsular Malaysia, the government... more
Habitat loss and fragmentation are a key threat to the survival of several small carnivore species in Southeast Asia. Enhancing habitat connectivity is therefore an important conservation strategy. In Peninsular Malaysia, the government plans to connect its fragmented forests via 17 habitat linkages to form a large contiguous forest complex known as the Central Forest Spine. Small carnivore species composition in these linkages remains poorly documented. Of the 12 species detected in and around Linkage 7, in the state of Terengganu, four are categorised as Vulnerable by The IUCN Red List of Threatened Species: Binturong Arctictis binturong, Banded Civet Hemigalus derbyanus, Oriental Small-clawed Otter Aonyx cinereus and Smooth-coated Otter Lutrogale perspicillata. A photograph of Crab-eating Mongoose Herpestes urva with young is the first record of this species from Terengganu, extending eastwards its known distribution in Peninsular Malaysia. Forests in and around this linkage are threatened by disturbance associated with an existing road, and the construction of a nearby dam. The study area’s relatively high recorded small carnivore species richness, and its complement of globally threatened small carnivore species, supports its inclusion into a proposed protected area (known as the Kenyir Wildlife Corridor). Information on small carnivores in other linkages warrants publication, especially from camera-trap surveys that consciously account for microhabitat use and behavioural variation between different species. This would allow a clearer understanding of small carnivore communities in Peninsular Malaysia.
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Human-induced forest fragmentation poses one of the largest threats to global diversity yet its impact on rattans (climbing palms) has remained virtually unexplored. Rattan is arguably the world's most valuable non-timber forest... more
Human-induced forest fragmentation poses one of the largest threats to global diversity yet its impact on rattans (climbing palms) has remained virtually unexplored. Rattan is arguably the world's most valuable non-timber forest product though current levels of harvesting and land-use change place wild populations at risk. To assess rattan response to fragmentation exclusive of harvesting impacts we examined rattan abundance, demography and ecology within the forests of northeastern, Australia. We assessed the community abundance of rattans, and component adult (>3 m) and juvenile (≤3 m) abundance in five intact forests and five fragments (23-58 ha) to determine their response to a range of environmental and ecological parameters. Fragmented forests supported higher abundances of rattans than intact forests. Fragment size and edge degradation significantly increased adult rattan abundance, with more in smaller fragments and near edges. Our findings suggest that rattan increas...
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Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these... more
Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable ...
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Summary Understanding the anatomical basis of plant water transport in forest ecosystems is crucial for contextualizing community‐level adaptations to drought, especially in life‐form‐rich tropical forests. To provide this context, we... more
Summary Understanding the anatomical basis of plant water transport in forest ecosystems is crucial for contextualizing community‐level adaptations to drought, especially in life‐form‐rich tropical forests. To provide this context, we explored wood functional anatomy traits related to plant hydraulic architecture across different plant functional groups in a lowland tropical rain forest. We measured wood traits in 90 species from six functional groups (mature‐phase, understorey and pioneer trees; understorey and pioneer shrubs; vines) and related these traits to intrinsic water‐use efficiency (WUEi) as a measure of physiological performance. We also examined vessel size distribution patterns across groups to determine trade‐offs in theoretical hydraulic safety vs. efficiency. Some plant functional groups exhibited significant differences in vessel parameters and WUEi. Vessel diameters in vines and pioneer trees were two‐ to threefold greater on average than in understorey trees and ...
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Strawberry guava (Psidium cattleianum) is a shade‐tolerant shrub or small tree invader in tropical and subtropical regions and is considered among the world's top 100 worst invasive species. Studies from affected regions report... more
Strawberry guava (Psidium cattleianum) is a shade‐tolerant shrub or small tree invader in tropical and subtropical regions and is considered among the world's top 100 worst invasive species. Studies from affected regions report deleterious effects of strawberry guava invasion on native vegetation. Here we examine the life history demographics and environmental determinants of strawberry guava invasions to inform effective weed management in affected rainforest regions. We surveyed the vegetation of 8 mature rainforest and 33 successional sites at various stages of regeneration in the Australian Wet Tropics and found that strawberry guava invasion was largely restricted to successional forests. Strawberry guava exhibited high stem and seedling densities, represented approximately 8% of all individual stems recorded and 20% of all seedlings recorded. The species also had the highest basal area among all the non‐native woody species measured. We compared environmental and community...
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Research Interests: Geography, Hydrology, Agroforestry, Ecology, Forest Fragmentation, and 15 moreClimate, Wildlife Conservation, Edge effects, Hunting, Wildlife, Forests, Deforestation, Habitat fragmentation, Environmental degradation, Environmental Impact, Logging, Amazon rainforest, Microclimate, Amazon basin, and ENVIRONMENTAL SCIENCE AND MANAGEMENT
Research Interests: Botany, Geography, Forestry, Conservation Biology, Conservation, and 15 moreBiology, Ecology, Agriculture, Biodiversity, Forest Ecology, Endangered Species, Environmental Pollution, Biodiversity Research, Habitat, Animals, Data Collection, Fires, Conservation of Natural Resources, Alpine and Arctic Research, and Habitat Destruction
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Research Interests: Landscape Ecology, Geography, Biology, Ecology, Biogeography, and 15 moreSpecies invasions, Biological Sciences, Small Mammals, Environmental Sciences, Biological Conservation, Habitat, Fauna, Biological, Habitat Use, Fragmentation, Habitat fragmentation, South America, Species Invasion, Amazonian Rainforest, and Forest fragments
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Understanding how tropical rainforest trees may respond to the precipitation extremes predicted in future climate change scenarios is paramount for their conservation and management. Tree species clearly differ in drought susceptibility,... more
Understanding how tropical rainforest trees may respond to the precipitation extremes predicted in future climate change scenarios is paramount for their conservation and management. Tree species clearly differ in drought susceptibility, suggesting that variable water transport strategies exist. Using a multi-disciplinary approach, we examined the hydraulic variability in trees in a lowland tropical rainforest in north-eastern Australia. We studied eight tree species representing broad plant functional groups (one palm and seven eudicot mature-phase, and early-successional trees). We characterised the species' hydraulic system through maximum rates of volumetric sap flow and velocities using the heat ratio method, and measured rates of tree growth and several stem, vessel, and leaf traits. Sap flow measures exhibited limited variability across species, although early-successional species and palms had high mean sap velocities relative to most mature-phase species. Stem, vessel, ...
Research Interests: Climate Change, Australia, Biology, Ecology, Ecophysiology, and 15 moreDrought Stress, Medicine, Multidisciplinary, Plant Hydraulics, Drought and Water Stress, Trait, Rainforest, Trees, Plant Functional Traits, Droughts, PLoS one, Plant Ecology and Functional Traits, Tropical Climate, Plant Leaves, and Plant Transpiration
Biodiversity loss is one of the main challenges of our time and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of... more
Biodiversity loss is one of the main challenges of our time and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space. While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes vast areas of the tropics remain understudied. In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity, but it remains among the least known forests in America and is often underrepresented in biodiversity databases. To worsen this situation, human-induced modifications may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost.
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For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter... more
For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regi...
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AimTo investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional... more
AimTo investigate the geographic patterns and ecological correlates in the geographic distribution of the most common tree dispersal modes in Amazonia (endozoochory, synzoochory, anemochory and hydrochory). We examined if the proportional abundance of these dispersal modes could be explained by the availability of dispersal agents (disperser‐availability hypothesis) and/or the availability of resources for constructing zoochorous fruits (resource‐availability hypothesis).Time periodTree‐inventory plots established between 1934 and 2019.Major taxa studiedTrees with a diameter at breast height (DBH) ≥ 9.55 cm.LocationAmazonia, here defined as the lowland rain forests of the Amazon River basin and the Guiana Shield.MethodsWe assigned dispersal modes to a total of 5433 species and morphospecies within 1877 tree‐inventory plots across terra‐firme, seasonally flooded, and permanently flooded forests. We investigated geographic patterns in the proportional abundance of dispersal modes. We ...
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In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy... more
In a time of rapid global change, the question of what determines patterns in species abundance distribution remains a priority for understanding the complex dynamics of ecosystems. The constrained maximization of information entropy provides a framework for the understanding of such complex systems dynamics by a quantitative analysis of important constraints via predictions using least biased probability distributions. We apply it to over two thousand hectares of Amazonian tree inventories across seven forest types and thirteen functional traits, representing major global axes of plant strategies. Results show that constraints formed by regional relative abundances of genera explain eight times more of local relative abundances than constraints based on directional selection for specific functional traits, although the latter does show clear signals of environmental dependency. These results provide a quantitative insight by inference from large-scale data using cross-disciplinary ...
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ABSTRACT: The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into... more
ABSTRACT: The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater rate of decline in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth's climate.
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Atmospheric CO2 records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink likely located in the tropics, particularly in the Amazon. Nevertheless, it is... more
Atmospheric CO2 records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink likely located in the tropics, particularly in the Amazon. Nevertheless, it is unclear how the terrestrial carbon sink will evolve as climate and atmospheric composition continue to change. Here we analyse the historic evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that the Amazon has acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation. Rates of net increase in above ground biomass declined by a third during the last decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while reduction in biomass due to tree mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortali...
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AimPalms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and... more
AimPalms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change.LocationTropical and subtropical moist forests.Time periodCurrent.Major taxa studiedPalms (Arecaceae).MethodsWe assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimat...
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The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die,... more
The carbon sink capacity of tropical forests is substantially affected by tree mortality. However, the main drivers of tropical tree death remain largely unknown. Here we present a pan-Amazonian assessment of how and why trees die, analysing over 120,000 trees representing > 3800 species from 189 long-term RAINFOR forest plots. While tree mortality rates vary greatly Amazon-wide, on average trees are as likely to die standing as they are broken or uprooted—modes of death with different ecological consequences. Species-level growth rate is the single most important predictor of tree death in Amazonia, with faster-growing species being at higher risk. Within species, however, the slowest-growing trees are at greatest risk while the effect of tree size varies across the basin. In the driest Amazonian region species-level bioclimatic distributional patterns also predict the risk of death, suggesting that these forests are experiencing climatic conditions beyond their adaptative limit...
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Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes conspecific spatial aggregation to an extended... more
Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes conspecific spatial aggregation to an extended database of forest plots with up-to-date taxonomy. We show that the species abundance distribution of Amazonia is best approximated by a logseries with aggregated individuals, where aggregation increases with rarity. By averaging several methods to estimate total richness, we confirm that over 15,000 tree species are expected to occur in Amazonia. We also show that using ten times the number of plots would result in an increase to just ~50% of those 15,000 estimated species. To get a more complete sample of all tree species, rigorous field campaigns may be needed but the number of trees in Amazonia will remain an estimate for years to come.
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Thermal sensitivity of tropical treesA key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivanet al.measured carbon stocks and fluxes in permanent... more
Thermal sensitivity of tropical treesA key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivanet al.measured carbon stocks and fluxes in permanent forest plots distributed globally. This synthesis of plot networks across climatic and biogeographic gradients shows that forest thermal sensitivity is dominated by high daytime temperatures. This extreme condition depresses growth rates and shortens the time that carbon resides in the ecosystem by killing trees under hot, dry conditions. The effect of temperature is worse above 32°C, and a greater magnitude of climate change thus risks greater loss of tropical forest carbon stocks. Nevertheless, forest carbon stocks are likely to remain higher under moderate climate change if they are protected from direct impacts such as clearance, logging, or fires.Science, this issue p.869
Research Interests: Marine Biology, Environmental Science, Climate Change, Climate change policy, Science, and 12 moreCarbon Cycle, Climate Change Adaptation And Mitigation Strategies, Biodiversity, Medicine, Multidisciplinary, Climate Change Impacts, Tropics, Tropical forest, Amazon forest, Ecosystem, Tropical forests, and Tropical Climate
Competition among trees is an important driver of community structure and dynamics in tropical forests. Neighboring trees may impact an individual tree’s growth rate and probability of mortality, but large‐scale geographic and... more
Competition among trees is an important driver of community structure and dynamics in tropical forests. Neighboring trees may impact an individual tree’s growth rate and probability of mortality, but large‐scale geographic and environmental variation in these competitive effects has yet to be evaluated across the tropical forest biome. We quantified effects of competition on tree‐level basal area growth and mortality for trees ≥10‐cm diameter across 151 ~1‐ha plots in mature tropical forests in Amazonia and tropical Africa by developing nonlinear models that accounted for wood density, tree size, and neighborhood crowding. Using these models, we assessed how water availability (i.e., climatic water deficit) and soil fertility influenced the predicted plot‐level strength of competition (i.e., the extent to which growth is reduced, or mortality is increased, by competition across all individual trees). On both continents, tree basal area growth decreased with wood density and increase...
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AimLarge tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid... more
AimLarge tropical trees form the interface between ground and airborne observations, offering a unique opportunity to capture forest properties remotely and to investigate their variations on broad scales. However, despite rapid development of metrics to characterize the forest canopy from remotely sensed data, a gap remains between aerial and field inventories. To close this gap, we propose a new pan‐tropical model to predict plot‐level forest structure properties and biomass from only the largest trees.LocationPan‐tropical.Time periodEarly 21st century.Major taxa studiedWoody plants.MethodsUsing a dataset of 867 plots distributed among 118 sites across the tropics, we tested the prediction of the quadratic mean diameter, basal area, Lorey's height, community wood density and aboveground biomass (AGB) from the ith largest trees.ResultsMeasuring the largest trees in tropical forests enables unbiased predictions of plot‐ and site‐level forest structure. The 20 largest trees per h...
Research Interests: Geography, Environmental Science, Climate Change, Tropical Ecology, Carbon, and 14 moreForest Ecology And Management, Ecology, Carbon Sequestration, Forest Ecology, Canopy, REDD, Tropics, Tropical Forest Ecology, Tropical forest, Trees, Forest Structure, Tropical forests, Ecological Applications, and Basal Area
Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate‐induced biodiversity changes are widely documented elsewhere, few studies have addressed... more
Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate‐induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long‐term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO2 concentrations): maximum tree size, biogeographic water‐deficit affiliation and wood density. Tree communities have become increasingly dominated by large‐statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry sea...
Research Interests: Geography, Climate Change, Diversity, Ecology, Amazonia, and 15 moreGlobal Change Biology, Medicine, Biological Sciences, Functional Traits, Biodiversity Conservation, Growth, Environmental Sciences, Carbon Storage, Traits, Amazon rainforest, Science Technology, Functional, Amazon basin, Temporal Trends, and Neotropical Forest
Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are... more
Species distribution models (SDMs) are widely used in ecology and conservation. Presence-only SDMs such as MaxEnt frequently use natural history collections (NHCs) as occurrence data, given their huge numbers and accessibility. NHCs are often spatially biased which may generate inaccuracies in SDMs. Here, we test how the distribution of NHCs and MaxEnt predictions relates to a spatial abundance model, based on a large plot dataset for Amazonian tree species, using inverse distance weighting (IDW). We also propose a new pipeline to deal with inconsistencies in NHCs and to limit the area of occupancy of the species. We found a significant but weak positive relationship between the distribution of NHCs and IDW for 66% of the species. The relationship between SDMs and IDW was also significant but weakly positive for 95% of the species, and sensitivity for both analyses was high. Furthermore, the pipeline removed half of the NHCs records. Presence-only SDM applications should consider th...
Research Interests: Landscape Ecology, Environmental Science, Science, Brazil, Floristics, and 15 moreMedicine, Multidisciplinary, Humans, Polygonaceae, Humanities and Social Sciences, Species Distribution, IUCN Red List, Inverse Distance Weighting, Fabaceae, Indian Geography and Travel, DDC, Conservation of Natural Resources, Occupancy, Plant Dispersal, and Chrysobalanaceae
The role of the world's forests as a “sink” for atmospheric carbon dioxide is the subject of active debate. Long-term monitoring of plots in mature humid tropical forests concentrated in South America revealed that biomass gain by... more
The role of the world's forests as a “sink” for atmospheric carbon dioxide is the subject of active debate. Long-term monitoring of plots in mature humid tropical forests concentrated in South America revealed that biomass gain by tree growth exceeded losses from tree death in 38 of 50 Neotropical sites. These forest plots have accumulated 0.71 ton, plus or minus 0.34 ton, of carbon per hectare per year in recent decades. The data suggest that Neotropical forests may be a significant carbon sink, reducing the rate of increase in atmospheric carbon dioxide.
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The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the... more
The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the distributions and abundances of 85 woody species domesticated by pre-Columbian peoples. Domesticated species are five times more likely than nondomesticated species to be hyperdominant. Across the basin, the relative abundance and richness of domesticated species increase in forests on and around archaeological sites. In southwestern and eastern Amazonia, distance to archaeological sites strongly influences the relative abundance and richness of domesticated species. Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples.
Research Interests: Ancient History, Geography, Cultural Landscapes, Science, Brazil, and 15 moreEcology, Amazonia, Indian ancient history, Forest Ecology, Ancient Greek History, Medicine, Multidisciplinary, Historical Ecology, Prehistory, Humans, Forests, Domestication, Species Richness, Amazon rainforest, and Amazonian
Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative... more
Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic sig...
Research Interests: Evolutionary Biology, Geography, Community Ecology, Biomass, Biology, and 15 moreLife Sciences, Ecology, Evolutionary Ecology, Medicine, Biological Sciences, Functional Traits, Growth, Forests, Phylogenetic comparative methods, Biological evolution, Phylogenetic Diversity, Divergent Selection, Amazon rainforest, Convergent Evolution, and Medical and Health Sciences
The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin‐wide losses of biomass. A drought of similar climatological magnitude occurred again in 2010;... more
The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin‐wide losses of biomass. A drought of similar climatological magnitude occurred again in 2010; however, there has been no basin‐wide ground‐based evaluation of effects on vegetation. We examine to what extent the 2010 drought affected forest dynamics using ground‐based observations of mortality and growth from an extensive forest plot network. We find that during the 2010 drought interval, forests did not gain biomass (net change: −0.43 Mg ha−1, confidence interval (CI): −1.11, 0.19, n = 97), regardless of whether forests experienced precipitation deficit anomalies. This contrasted with a long‐term biomass sink during the baseline pre‐2010 drought period (1998 to pre‐2010) of 1.33 Mg ha−1 yr−1 (CI: 0.90, 1.74, p < 0.01). The resulting net impact of the 2010 drought (i.e., reversal of the baseline net sink) was −1.95 Mg ha−1 yr−1 (CI:−2.77, −...
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Understanding the processes that determine above‐ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation... more
Understanding the processes that determine above‐ground biomass (AGB) in Amazonian forests is important for predicting the sensitivity of these ecosystems to environmental change and for designing and evaluating dynamic global vegetation models (DGVMs). AGB is determined by inputs from woody productivity [woody net primary productivity (NPP)] and the rate at which carbon is lost through tree mortality. Here, we test whether two direct metrics of tree mortality (the absolute rate of woody biomass loss and the rate of stem mortality) and/or woody NPP, control variation in AGB among 167 plots in intact forest across Amazonia. We then compare these relationships and the observed variation in AGB and woody NPP with the predictions of four DGVMs. The observations show that stem mortality rates, rather than absolute rates of woody biomass loss, are the most important predictor of AGB, which is consistent with the importance of stand size structure for determining spatial variation in AGB. ...
Research Interests: Environmental Science, Biomass, Productivity, Amazonia, Global Change Biology, and 13 moreMedicine, Biological Sciences, Environmental Sciences, Forests, Dynamic Global Vegetation Models, Trees, South America, Tropical Forest Dynamics, Primary Production, Theoretical Models, Aboveground biomass, Tropical Climate, and Woody plant
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Introduction Recent decades have seen a major international effort to inventory tree communities in the Amazon Basin and Guiana Shield (Amazonia), but the vast extent and record diversity of these forests have hampered an understanding of... more
Introduction Recent decades have seen a major international effort to inventory tree communities in the Amazon Basin and Guiana Shield (Amazonia), but the vast extent and record diversity of these forests have hampered an understanding of basinwide patterns. To overcome this obstacle, we compiled and standardized species-level data on more than half a million trees in 1170 plots sampling all major lowland forest types to explore patterns of commonness, rarity, and richness. Methods The ~6-million-km 2 Amazonian lowlands were divided into 1° cells, and mean tree density was estimated for each cell by using a loess regression model that included no environmental data but had its basis exclusively in the geographic location of tree plots. A similar model, allied with a bootstrapping exercise to quantify sampling error, was used to generate estimated Amazon-wide abundances of the 4962 valid species in the data set. We estimated the total number of tree species in the Amazon by fitting t...
Research Interests: Botany, Geography, Plant Ecology, Conservation Biology, Science, and 15 moreBiodiversity and Ecosystem Function, Biology, Ecology, Rivers, Biodiversity, Medicine, Multidisciplinary, Biodiversity Research, Population, Habitat, South America, Floral diversity, Amazon rainforest, Amazon basin, and Amazonian
Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such “monodominant” forests are known from all of the main tropical regions. For Amazonia, we... more
Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such “monodominant” forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree specie...
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1. Understanding the anatomical basis of plant water transport in forest ecosystems is crucial for contextualizing community-level adaptations to drought, especially in lifeform-rich tropical forests. To provide this context, we... more
1. Understanding the anatomical basis of plant water transport in forest ecosystems is crucial for contextualizing community-level adaptations to drought, especially in lifeform-rich tropical forests. To provide this context, we explored wood functional anatomy traits related to plant hydraulic architecture across different plant functional groups in a lowland tropical rainforest.
2. We measured wood traits in 90 species from six functional groups (mature-phase, understorey and pioneer trees; understorey and pioneer shrubs; vines) and related these traits to intrinsic water-use efficiency (WUEi) as a measure of physiological performance. We also examined vessel size distribution patterns across groups to determine tradeoffs in theoretical hydraulic safety versus efficiency.
3. Plant functional groups exhibited significant differences in vessel parameters and WUEi. Vessel diameters in vines and pioneer trees were two- to three-fold greater on average than in understorey trees and shrubs. Contrastingly, vessels in understorey-trees and -shrubs fell within the smaller size classes, suggesting greater safety mechanisms. In addition to these trends, large vessel dimensions were important predictors of WUEi among the functional groups.
4. We conclude that plant functional groups in tropical rainforest have distinctive functional anatomy profiles. These groups can therefore serve as a framework for further investigations on structure-function relationships, and a sound basis for modeling species responses to drought.
2. We measured wood traits in 90 species from six functional groups (mature-phase, understorey and pioneer trees; understorey and pioneer shrubs; vines) and related these traits to intrinsic water-use efficiency (WUEi) as a measure of physiological performance. We also examined vessel size distribution patterns across groups to determine tradeoffs in theoretical hydraulic safety versus efficiency.
3. Plant functional groups exhibited significant differences in vessel parameters and WUEi. Vessel diameters in vines and pioneer trees were two- to three-fold greater on average than in understorey trees and shrubs. Contrastingly, vessels in understorey-trees and -shrubs fell within the smaller size classes, suggesting greater safety mechanisms. In addition to these trends, large vessel dimensions were important predictors of WUEi among the functional groups.
4. We conclude that plant functional groups in tropical rainforest have distinctive functional anatomy profiles. These groups can therefore serve as a framework for further investigations on structure-function relationships, and a sound basis for modeling species responses to drought.
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Questions: Which factors affect the diversity and species composition of tropical secondary rain forests in a region with little information regarding their contribution to global biodiversity? Can older secondary forests approach the... more
Questions: Which factors affect the diversity and species composition of tropical secondary rain forests in a region with little information regarding their contribution to global biodiversity? Can older secondary forests approach the diversity and composition of mature forests following 100 yr of pasture use? Location: Tropical secondary rain forest, northeast Australia. Methods: We identified trees, shrubs and vines ≥2.5 cm DBH in a chronose-quence comprising 33 sites, aged 3–60 yr since the formation of closed canopy (9–69 yr since pasture abandonment) and compared them with eight sites in nearby mature forest remnants. Results: Species richness and community composition were strongly influenced by secondary forest age but did not attain values of mature forest. Sites in close proximity to mature forests had higher plant richness, whereas low soil fertility appeared to depress species recruitment. Thus, multiple factors operated in secondary forest community assembly. Unusual tree community patterns that suggest accelerated or slowed successional trajectories were observed at several sites. Conclusions: Secondary forests in our study region contained important plant diversity for conservation, particularly in older sites, however, even the oldest secondary forests (60 yr) did not converge with the species composition and diversity of mature forests. The protection of mature forest tracts and remnants must be a priority if we are to maintain high levels of plant diversity in tropical landscapes, conserve rare species and facilitate the recruitment of plant species in recovering forests.
Full floristic data, tree demography, and biomass estimates incorporating non-tree lifeforms are seldom collected and reported for forest plots in the tropics. Established research stations serve as important repositories of such... more
Full floristic data, tree demography, and biomass estimates incorporating non-tree lifeforms are seldom collected and reported for forest plots in the tropics. Established research stations serve as important repositories of such biodiversity and ecological data. With a canopy crane setup within a tropical lowland rainforest estate, the 42-ha Daintree Rainforest Observatory (DRO) in Cape Tribulation, northern Australia is a research facility of international significance. We obtained an estimate of the vascular plant species richness for the site, by surveying all vascular plant species from various mature-phase, remnant and open vegetation patches within the site. We also integrate and report the demography and basal areas of trees ≥ 10 cm diameter at breast height (dbh) in a new 1-ha core plot, an extension to the pre-existing forest 1-ha plot under the canopy crane. In addition, we report for the canopy crane plot new demography and basal areas for smaller-size shrubs and treelets subsampled from nine 20 m2 quadrats, and liana basal area and abundance from the whole plot. The DRO site has an estimated total vascular plant species richness of 441 species, of which 172 species (39%) are endemic to Australia, and 4 species are endemics to the Daintree region. The 2 x 1-ha plots contains a total of 262 vascular plant species of which 116 (1531 individuals) are tree species ≥ 10 cm dbh. We estimate a stem basal area of 34.9 m2 ha-1, of which small stems (tree saplings and shrubs <10cm dbh) and lianas collectively contribute c.4.2%. Comparing the stem density-diversity patterns of the DRO forest with other tropical rainforests globally, our meta-analysis shows that DRO forests has a comparatively high stem density and moderate species diversity, due to the influence of cyclones. These data will provide an important foundation for ecological and conservation studies in lowland tropical forest.
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Land use changes, such as deforestation and urbanization, can influence interactions between vectors, hosts, and pathogens. The consequences may result in the appearance and rise of mosquito-borne diseases, especially in remote tropical... more
Land use changes, such as deforestation and urbanization, can influence interactions between vectors, hosts, and pathogens. The consequences may result in the appearance and rise of mosquito-borne diseases, especially in remote tropical regions. Tropical regions can be the hotspots for the emergence of diseases due to high biological diversity and complex species interactions. Furthermore, frontier areas are often haphazardly surveyed as a result of inadequate or expensive sampling techniques, which limit early detection and medical intervention. We trialed a novel sampling technique of nonpowered traps and a carbon dioxide attractant derived from yeast and sugar to explore how land use influences mosquito communities on four remote, tropical islands in the Australian Torres Strait. Using this technique, we collected > 11,000 mosquitoes from urban and sylvan habitats. We found that human land use significantly affected mosquito communities. Mosquito abundances and diversity were ...