ORCID Profile
0000-0002-8066-6851
Current Organisations
University of Leeds
,
University College London
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Publisher: Springer Science and Business Media LLC
Date: 10-03-2013
DOI: 10.1038/NGEO1741
Publisher: Springer Science and Business Media LLC
Date: 28-04-2015
DOI: 10.1038/NCOMMS7857
Abstract: While Amazonian forests are extraordinarily erse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their ersity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/FP14040
Publisher: Wiley
Date: 03-03-2014
DOI: 10.1111/ELE.12252
Publisher: Copernicus GmbH
Date: 05-05-2011
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Springer Science and Business Media LLC
Date: 31-08-2025
DOI: 10.1038/S41467-017-01997-0
Abstract: Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha −1 per year (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon. These results closely match those from African and Amazonian plot networks, suggesting that the world’s remaining intact tropical forests are now en masse out-of-equilibrium. Although both pan-tropical and long-term, the sink in remaining intact forests appears vulnerable to climate and land use changes. Across Borneo the 1997–1998 El Niño drought temporarily halted the carbon sink by increasing tree mortality, while fragmentation persistently offset the sink and turned many edge-affected forests into a carbon source to the atmosphere.
Publisher: The Royal Society
Date: 29-03-2004
Abstract: Previous work has shown that tree turnover, tree biomass and large liana densities have increased in mature tropical forest plots in the late twentieth century. These results point to a concerted shift in forest ecological processes that may already be having significant impacts on terrestrial carbon stocks, fluxes and bio ersity. However, the findings have proved controversial, partly because a rather limited number of permanent plots have been monitored for rather short periods. The aim of this paper is to characterize regional–scale patterns of ‘tree turnover’ (the rate with which trees die and recruit into a population) by using improved datasets now available for Amazonia that span the past 25 years. Specifically, we assess whether concerted changes in turnover are occurring, and if so whether they are general throughout the Amazon or restricted to one region or environmental zone. In addition, we ask whether they are driven by changes in recruitment, mortality or both. We find that: (i) trees 10 cm or more in diameter recruit and die twice as fast on the richer soils of southern and western Amazonia than on the poorer soils of eastern and central Amazonia (ii) turnover rates have increased throughout Amazonia over the past two decades (iii) mortality and recruitment rates have both increased significantly in every region and environmental zone, with the exception of mortality in eastern Amazonia (iv) recruitment rates have consistently exceeded mortality rates (v) absolute increases in recruitment and mortality rates are greatest in western Amazonian sites and (vi) mortality appears to be lagging recruitment at regional scales. These spatial patterns and temporal trends are not caused by obvious artefacts in the data or the analyses. The trends cannot be directly driven by a mortality driver (such as increased drought or fragmentation–related death) because the biomass in these forests has simultaneously increased. Our findings therefore indicate that long–acting and widespread environmental changes are stimulating the growth and productivity of Amazon forests.
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
DOI: 10.1038/S41559-022-01747-6
Abstract: Tropical forests are some of the most bio erse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forests' functional ersity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional ersity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits s led from 2,461 in idual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional ersity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally erse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional ersity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional ersity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.
Publisher: Springer Science and Business Media LLC
Date: 03-2015
DOI: 10.1038/NATURE14283
Abstract: Atmospheric carbon dioxide records indicate that the land surface has acted as a strong global carbon sink over recent decades, with a substantial fraction of this sink probably 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 historical evolution of the biomass dynamics of the Amazon rainforest over three decades using a distributed network of 321 plots. While this analysis confirms that Amazon forests have 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 one-third during the past decade compared to the 1990s. This is a consequence of growth rate increases levelling off recently, while biomass mortality persistently increased throughout, leading to a shortening of carbon residence times. Potential drivers for the mortality increase include greater climate variability, and feedbacks of faster growth on mortality, resulting in shortened tree longevity. The observed decline of the Amazon sink erges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models.
Publisher: Springer Science and Business Media LLC
Date: 26-04-2023
DOI: 10.1038/S41586-023-05971-3
Abstract: Tropical forests face increasing climate risk 1,2 , yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for ex le, $$\\varPsi $$ Ψ 50 ) and hydraulic safety margins (for ex le, HSM 50 ) are important predictors of drought-induced mortality risk 3–5 , little is known about how these vary across Earth’s largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters $$\\varPsi $$ Ψ 50 and HSM 50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both $$\\varPsi $$ Ψ 50 and HSM 50 influence the biogeographical distribution of Amazon tree species. However, HSM 50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM 50 are gaining more biomass than are low HSM 50 forests. We propose that this may be associated with a growth–mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM 50 in the Amazon 6,7 , with strong implications for the Amazon carbon sink.
Publisher: Wiley
Date: 29-04-2004
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
DOI: 10.1038/S41467-020-18996-3
Abstract: 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 limits. These results provide not only a holistic pan-Amazonian picture of tree death but large-scale evidence for the overarching importance of the growth–survival trade-off in driving tropical tree mortality.
Publisher: Springer Science and Business Media LLC
Date: 10-10-2019
DOI: 10.1038/S41597-019-0196-1
Abstract: Forest biomass is an essential indicator for monitoring the Earth’s ecosystems and climate. It is a critical input to greenhouse gas accounting, estimation of carbon losses and forest degradation, assessment of renewable energy potential, and for developing climate change mitigation policies such as REDD+, among others. Wall-to-wall mapping of aboveground biomass (AGB) is now possible with satellite remote sensing (RS). However, RS methods require extant, up-to-date, reliable, representative and comparable in situ data for calibration and validation. Here, we present the Forest Observation System (FOS) initiative, an international cooperation to establish and maintain a global in situ forest biomass database. AGB and canopy height estimates with their associated uncertainties are derived at a 0.25 ha scale from field measurements made in permanent research plots across the world’s forests. All plot estimates are geolocated and have a size that allows for direct comparison with many RS measurements. The FOS offers the potential to improve the accuracy of RS-based biomass products while developing new synergies between the RS and ground-based ecosystem research communities.
Publisher: Springer Science and Business Media LLC
Date: 04-01-2021
DOI: 10.1038/S41467-020-20537-X
Abstract: A Correction to this paper has been published: 0.1038/s41467-020-20537-x
Publisher: Wiley
Date: 04-01-2010
Publisher: Routledge
Date: 16-10-2015
Publisher: Springer Science and Business Media LLC
Date: 09-2023
Publisher: Wiley
Date: 12-12-2020
DOI: 10.1111/GEB.13231
Publisher: Wiley
Date: 05-05-2020
DOI: 10.1002/ECY.3052
Abstract: Competition among trees is an important driver of community structure and dynamics in tropical forests. Neighboring trees may impact an in idual 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 in idual trees). On both continents, tree basal area growth decreased with wood density and increased with tree size. Growth decreased with neighborhood crowding, which suggests that competition is important. Tree mortality decreased with wood density and generally increased with tree size, but was apparently unaffected by neighborhood crowding. Across plots, variation in the plot‐level strength of competition was most strongly related to plot basal area (i.e., the sum of the basal area of all trees in a plot), with greater reductions in growth occurring in forests with high basal area, but in Amazonia, the strength of competition also varied with plot‐level wood density. In Amazonia, the strength of competition increased with water availability because of the greater basal area of wetter forests, but was only weakly related to soil fertility. In Africa, competition was weakly related to soil fertility and invariant across the shorter water availability gradient. Overall, our results suggest that competition influences the structure and dynamics of tropical forests primarily through effects on in idual tree growth rather than mortality and that the strength of competition largely depends on environment‐mediated variation in basal area.
Publisher: The Royal Society
Date: 29-03-2004
Abstract: A previous study by Phillips et al . of changes in the biomass of permanent s le plots in Amazonian forests was used to infer the presence of a regional carbon sink. However, these results generated a vigorous debate about s ling and methodological issues. Therefore we present a new analysis of biomass change in old–growth Amazonian forest plots using updated inventory data. We find that across 59 sites, the above–ground dry biomass in trees that are more than 10 cm in diameter (AGB) has increased since plot establishment by 1.22 ± 0.43 Mg per hectare per year (ha −1 yr −1 ), where 1 ha = 10 4 m 2 ), or 0.98 ± 0.38 Mg ha −1 yr −1 if in idual plot values are weighted by the number of hectare years of monitoring. This significant increase is neither confounded by spatial or temporal variation in wood specific gravity, nor dependent on the allometric equation used to estimate AGB. The conclusion is also robust to uncertainty about diameter measurements for problematic trees: for 34 plots in western Amazon forests a significant increase in AGB is found even with a conservative assumption of zero growth for all trees where diameter measurements were made using optical methods and/or growth rates needed to be estimated following fieldwork. Overall, our results suggest a slightly greater rate of net stand–level change than was reported by Phillips et al . Considering the spatial and temporal scale of s ling and associated studies showing increases in forest growth and stem turnover, the results presented here suggest that the total biomass of these plots has on average increased and that there has been a regional–scale carbon sink in old–growth Amazonian forests during the previous two decades.
Publisher: Springer Science and Business Media LLC
Date: 19-01-2018
DOI: 10.1038/S41467-018-02920-X
Abstract: The original version of this Article contained an error in the third sentence of the abstract and incorrectly read “Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha −1 year −1 (95% CI 0.14–0.72, mean period 1988–2010) above-ground live biomass”, rather than the correct “Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha −1 year −1 (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon”. This has now been corrected in both the PDF and HTML versions of the Article.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-05-2020
Abstract: A key uncertainty in climate change models is the thermal sensitivity of tropical forests and how this value might influence carbon fluxes. Sullivan et 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
Publisher: Wiley
Date: 21-04-2004
Publisher: Wiley
Date: 31-12-2019
DOI: 10.1111/GCB.14904
Abstract: Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to bio ersity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on in idual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
Publisher: Copernicus GmbH
Date: 21-05-2015
Publisher: Oxford University PressOxford
Date: 30-06-2007
DOI: 10.1093/ACPROF:OSO/9780198567066.003.0010
Abstract: Previous work found that tree turnover, biomass, and large liana densities increased in mature tropical forests in the late 20th century, indicating a concerted shift in forest ecological processes. However, the findings have proved controversial. Here, regional-scale patterns of tree turnover are characterized, using improved datasets available for Amazonia that span the last twenty-five years. The main findings include: trees at least 10 cm in diameter recruit and die twice as fast on the richer soils of western Amazonia compared to trees on the poorer soils of eastern Amazonia turnover rates have increased throughout Amazonia over the last two decades mortality and recruitment rates have tended to increase in every region and environmental zone recruitment rates consistently exceed mortality rates and increases in recruitment and mortality rates are greatest in western Amazonia. These patterns and trends are not caused by obvious artefacts in the data or the analyses, and cannot be directly driven by a mortality driver such as increased drought because the biomass in these forests has simultaneously increased. Apparently, therefore, widespread environmental changes are stimulating the growth and productivity of Amazon forests.
Publisher: Oxford University PressOxford
Date: 30-06-2007
DOI: 10.1093/ACPROF:OSO/9780198567066.003.0011
Abstract: This chapter discusses a previous study by Phillips et al. (1998) on biomass changes in Amazonian permanent s le plots which has been used to infer the presence of a regional carbon sink, generating vigorous debate about s ling and methodological issues. A new analysis of biomass change in old-growth Amazonian forest plots is presented here using new inventory data. It has been found that across fifty-nine sites, the above-ground dry biomass in trees of more than 10 cm in diameter has increased since plot establishment by about 1.22 Mg per hectare per year, or about 0.98 Mg per hectare per year if in idual plot values are weighted by the number of hectare years of monitoring. This significant increase is not confounded by spatial or temporal variation in wood specific gravity, nor does it depend on the allometric equation used to estimate biomass. Overall, these results suggest a slightly greater rate of net stand-level change than reported in 1998, and indicate the presence of a significant regional-scale carbon sink in old-growth Amazonian forests during the past two decades.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-10-2016
Abstract: The relationship between bio ersity and ecosystem productivity has been explored in detail in herbaceous vegetation, but patterns in forests are far less well understood. Liang et al. have amassed a global forest data set from ,000 s le plots in 44 countries. A positive and consistent relationship can be discerned between tree ersity and ecosystem productivity at landscape, country, and ecoregion scales. On average, a 10% loss in bio ersity leads to a 3% loss in productivity. This means that the economic value of maintaining bio ersity for the sake of global forest productivity is more than fivefold greater than global conservation costs. Science , this issue p. 196
Publisher: Wiley
Date: 22-05-2006
Publisher: Informa UK Limited
Date: 02-10-2012
Publisher: Springer Science and Business Media LLC
Date: 08-08-2022
DOI: 10.1038/S41559-022-01831-X
Abstract: The latitudinal ersity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with in idual tree information and local biophysical characteristics from ~1.3 million s le plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of bio ersity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers.
Publisher: Springer Science and Business Media LLC
Date: 25-08-2021
DOI: 10.1038/S41586-021-03728-4
Abstract: Tropical forests store 40-50 per cent of terrestrial vegetation carbon
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Simon Lewis.