Functional and Floristic Dynamics of Amazonian Forests

Intact Amazonian forests are often considered to be in a steady-state, where gains in growth and recruitment are offset by losses in mortality and where net carbon accumulation is close to zero. However, permanent plot data have shown that this ecosystem removes ca. 0.4 Pg of carbon per year from the atmosphere, approximately 5% of annual anthropogenic emissions. This thesis tests several competing hypothesized drivers of detected shifts in the structure and dynamics of intact forest, by assessing changes in functional and floristic composition over the last 30 years in over 100 long-term tree monitoring plots distributed across the Amazon. I first show that the majority of species are restricted to wetter conditions, indicating that stronger and more frequent droughts could threaten many species (Chapter 3). I generated an index of water-deficit affiliation for more than 500 genera and 1800 species (Chapter 3), and demonstrated that this index can predict drought-induced mortality in several drought experiments (Chapter 4). Finally, I document how floristic and functional composition of Amazonian forests has shifted over the last 30 years: forests are increasingly dominated by large-statured taxa, and further, large trees are becoming even larger in absolute size (Chapters 5 and 6). However, relative gains in basal area were similar across size classes and canopy status. In addition, recruits are increasingly comprised of dry-affiliated genera, while the mortality of wet-affiliated genera has increased in plots where the dry season has become more intense. Communities are becoming more dry- affiliated, although these changes still lag behind the drying trend. Overall, this thesis shows the potential vulnerability of Amazonian biodiversity to an increase in aridity and supports the hypotheses that a changing climate and increased atmospheric CO2 are driving changes in Amazonian floristic and functional dynamics

Distribuição, riqueza, diversidade e estabelecimento de áreas prioritárias para a conservação de Melastomataceae Juss. no estado do Paraná

Orientador: Renato GoldenbergCoorientador: Eric Camargo SmidtMonografia (Bacharelado) - Universidade Federal do Paraná. Setor de Ciências Biológicas. Curso de Graduação em Ciências BiológicasResumo : A família Melastomataceae Juss. está distribuída nas regiões tropicais e subtropicais sendo encontrada em diversas unidades fitogeográficas. No estado do Paraná muitas coletas para a família foram realizadas ao longo dos anos e encontram-se reunidas em diversas coleções botânicas. Nos últimos anos estudos sobre a maioria dos gêneros da família presentes no estado foram realizados. A reunião dos dados gerados pelos diversos registros de coleções botânicas confirmados por estes estudos realizados possibilitaram o presente estudo que buscou encontrar e entender o padrão de distribuição, riqueza e diversidade (índice de Shannon) da família no Paraná e nas cinco Regiões Fitogeográficas propostas para o estado (Campos, Cerrado, Floresta Estacional Semidecidual, Floresta Ombrófila Densa e Floresta Ombrófila Mista) e através da análise de complementaridade revelar as regiões prioritárias para a conservação da família no estado. Utilizou-se quatro estimadores de riqueza (Chao 1, Chao 2, Jackknife 1 e Jackknife 2) para revelar a possibilidade de novas espécies. Foram confirmados 5028 registros de Melastomataceae no Paraná divididos em cinco tribos: Bertolonieae, Melastomeae, Merianieae, Miconieae e Microlicieae. A maioria das coletas foi registrada para a região leste do estado (Campos, Floresta Ombrófila Densa e Floresta Ombrófila Mista), os estimadores de riqueza apontaram essa região como a de maior possibilidade de novas espécies. As tribos Miconieae e Melastomeae foram as mais representativas com mais observações, maior riqueza e diversidade. 17 áreas prioritárias para a conservação foram apontadas pela análise de complementaridade. O maior número de unidades fitogeográficas na região leste; a localização de Curitiba, maior centro de pesquisa do estado; uma maior concentração da agricultura em larga escala nas regiões norte e oeste; as características das unidades fitogeográficas e a preferência de espécies da família por determinadas condições ambientais são os cinco fatores que podem haver influenciado o padrão de distribuição. As tribos Miconieae e Melastomeae são segundo a literatura as de maior representatividade, corroborando os resultados. Das áreas apontadas como prioritárias para a preservação apenas o município de Joaquim Távora não apresentou unidade de conservação já instaurada. Esse tipo de análise deve ser realizado para outros grupos fomentando a elaboração de políticas públicas

Standardized drought indices in ecological research: why one size does not fit all

Defining and quantifying drought is essential when studying ecosystem responses to such events. Yet, many studies lack either a clear definition of drought, and/or erroneously assume drought under conditions within the range of “normal climatic variability” (c.f. Slette et al., 2019). To improve the general characterization of drought conditions in ecological studies, Slette et al. (2019) propose that drought studies should consistently relate to the local climatic context, assessing whether reported drought periods actually constitute extremes in water availability

Compositional response of Amazon forests to climate change

Most of the planet\u27s 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 CO 2 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 season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO 2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change

Author Correction: Tree mode of death and mortality risk factors across Amazon forests

The original version of this Article contained an error in Table 2, where the number of individuals in the “All Amazonia” row was reported as 11,6431 instead of 116,431. Also, the original version of this Article contained an error in the Methods, where the R2 for the proportion of broken/uprooted dead trees increase per year was reported as 0.12, the correct value being 0.06. The original version of this Article contained errors in the author affiliations. The affiliation of Gerardo A. Aymard C. with UNELLEZGuanare, Herbario Universitario (PORT), Portuguesa, Venezuela Compensation International Progress S.A. Ciprogress–Greenlife

Tree mode of death and mortality risk factors across Amazon forests

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.The analysis undertaken here was largely funded by the NERC-funded TREMOR project (NE/N004655/1) to D.G., R.J.W.B., E.G. and O.L.P. A.E.-M. was funded by TREMOR and by two ERC awards (T-FORCES 291585, TreeMort 758873). D.G. acknowledges further support from a Newton-funded consortium award (ARBOLES, NE/S011811/1). O.L.P. was supported by an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. T.A.M.P. was funded by the ERC award TreeMort 758873. This is paper number 47 of the Birmingham Institute of Forest Research. T.R.F., L.E.O.C.A. and O.L.P. were supported by NERC NE/N011570/1. Support for RAINFOR has come from the Natural Environment Research Council (NERC) Urgency Grants and NERC Consortium Grants AMAZONICA (NE/F005806/1), TROBIT (NE/D005590/1) and BIO-RED (NE/N012542/1), a European Research Council (ERC) grant T-FORCES (291585), the Gordon and Betty Moore Foundation (#1656), the European Union’s Seventh Framework Programme (282664, AMAZALERT) and the Royal Society (CH160091)

Biogeographic distributions of neotropical trees reflect their directly measured drought tolerances

High levels of species diversity hamper current understanding of how tropical forests may respond to environmental change. In the tropics, water availability is a leading driver of the diversity and distribution of tree species, suggesting that many tropical taxa may be physiologically incapable of tolerating dry conditions, and that their distributions along moisture gradients can be used to predict their drought tolerance. While this hypothesis has been explored at local and regional scales, large continental-scale tests are lacking. We investigate whether the relationship between drought-induced mortality and distributions holds continentally by relating experimental and observational data of drought-induced mortality across the Neotropics to the large-scale bioclimatic distributions of 115 tree genera. Across the different experiments, genera affiliated to wetter climatic regimes show higher drought-induced mortality than dry-affiliated ones, even after controlling for phylogenetic relationships. This pattern is stronger for adult trees than for saplings or seedlings, suggesting that the environmental filters exerted by drought impact adult tree survival most strongly. Overall, our analysis of experimental, observational, and bioclimatic data across neotropical forests suggests that increasing moisture-stress is indeed likely to drive significant changes in floristic composition.A.E.M. received a PhD scholarship from the T-FORCES ERC grant. O.L.P. is supported by an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. A.E.M. and D.G. are supported by the UK Natural Environment Research Council project, “TREMOR” (NE/N004655/1). P.M. was supported by UK NERC NE/J011002/1 and ARC DP170104091