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Questions Riverine and associated vegetation communities are periodically affected by floods. However, there have been few quantitative studies on the structural responses of Neotropical tree communities in semi‐arid regions to this perturbance. Here, we ask whether flooding regimes and soil attributes affect tree species diversity, composition, community structure, and soil attributes in Neotropical dry forests. Locations Southeast Brazil. Methods We sampled 120 forest plots of 400 m² totaling 4.8 ha across four tributaries of the São Francisco River with plots situated in areas representing three flooding regimes: (a) annually flooded; (b) occasionally flooded; and (c) never subjected to flooding. Using linear mixed‐effects models, we modelled how flooding regime and soil properties (fertility and texture) affect vegetation diversity (species richness), species composition and structural attributes (abundance of individuals, above‐ground biomass [AGB], and a community‐weighted trait average of multistemness [CWMms]) of these forest plots. Results Species richness in the annually flooded forests was significantly lower than in occasionally flooded or never flooded forests, in agreement with our models, which showed that flooding regime was a significant predictor for this variable. Flooding regime was a significant predictor of CWMms, with plots in annually flooded forest sites having the highest CWMms values. Soil chemical attributes were a significant predictor of AGB across all plots but not between flooding regime categories. Conclusions In Neotropical dry forests, environmental filters established by flooding can lead to differences among distinct biomes in vegetation structure, diversity patterns as well as system productivity. Conservation strategies for dry forests should therefore take these factors into consideration. Our study also highlights annually flooded dry forest as a significant component of the regional diversity of dry forests deserving of management attention.

Tropical forests have played an important role as a carbon sink over time. However, the carbon dynamics of Brazilian non-Amazon tropical forests are still not well understood. Here, we used data from 32 tropical seasonal forest sites, monitored from 1987 to 2020 (mean site monitoring length, ~15 years) to investigate their long-term trends in carbon stocks and sinks. Our results highlight a long-term decline in the net carbon sink (0.13 Mg C ha−1 year−1) caused by decreasing carbon gains (2.6% by year) and increasing carbon losses (3.4% by year). The driest and warmest sites are experiencing the most severe carbon sink decline and have already moved from carbon sinks to carbon sources. Because of the importance of the terrestrial carbon sink for the global climate, policies are needed to mitigate the emission of greenhouse gases and to restore and protect tropical seasonal forests.

1. Large-scale data compilation is increasing steadily in tropical forest research, but the lack of standardized methods for data collection limits drawing inference from large datasets and cross-biome analyses. Different inclusion methods and minimum tree diameter threshold are among these varying factors. To tackle this issue, we evaluated how different approaches for tree sampling affects our understanding of diversity and functioning in different tropical vegetation types.2. We used a unique dataset of 44 inventory plots (43.54 ha) encompassing an aridity gradient: evergreen moist forests, semideciduous and deciduous tropical forests.Data were collected using the by-tree inclusion method, in which, all stems are measured if the equivalent diameter of the tree reaches the minimum threshold.We simulated the impact of adopting different inclusion methods (by-stem and by-tree) and different minimum diameter thresholds on the estimation of number of trees and stems, biomass and species richness. We used linear and nonlinear mixed models to investigate the effect of minimum diameter threshold and inclusion method on our different response variables. We also evaluated species chance to be sampled under different minimum inclusion criteria.3. Inclusion method and minimum diameter threshold mainly affect the estimation of number of trees and stems and species richness, especially in deciduous and semideciduous forests, where resprouting is a prevalent strategy. In these forests, many trees that have several stems do not reach the minimum size individually when adopting the by-stem method, yet they do reach the minimum size threshold when all stems are considered together. For these environments under water stress, our analysis showed that using large minimum sizes, such as the 10 cm typically used in rainforests, implies large sampling losses, especially when used jointly with the by-stem inclusion method.4. The by-tree inclusion method represents an alternative approach that offers a more reliable sampling in different vegetation types, particularly in those habitats where resprouting is a widely encountered strategy along all age classes. 2018 | Methods in Ecology and Evoluঞon de SOUZA et Al.

The aim of this study was to evaluate the vegetation identity of local-scale ecotones and its importance to landscape biodiversity in a transition between savanna and forest vegetation types in Brazil. We surveyed the tree community (diameter at breast height ≥5 cm) within 25 plots of 400 m2 across three core vegetation types and two ecotones among them (totalling five vegetation types). We then evaluated similarities in species composition, community structure and phylogenetic diversity across the transitions in order to assess the relationship between the ecotones and the core areas. Ecotones were distinct floristic units with a high number of unique species and floristic and phylogenetic clustering, and hence these environments are additional vegetation types in relation to the core areas. Some species showed maximum abundance in ecotones, which harboured distinct ecological patterns, demonstrating the importance of the ecotones in the overall ecosystem. Results are related to the distribution of the species present in the regional pool across local-scale microhabitats, with ecotones being a product of a distinct environmental conditions resulting from the distinct adjacent biomes (savanna and forest), which enable the maintenance of biological diversity.

RESUMOA fragmentação florestal é um dos principais agentes de redução da biodiversidade, interferindo diretamente nos processos ecológicos da comunidade arbórea. Este trabalho teve como objetivo avaliar parâmetros de diversidade, estrutura e composição em três setores de um remanescente florestal com históricos distintos de perturbações. A vegetação arbórea foi avaliada em 24 parcelas de 10 × 10 m, amostrando um total de 1228 indivíduos vivos. Foram quantificados o índice de diversidade de Shannon, a equabilidade de Pielou e os estimadores jackknife de primeira e segunda ordem. Os indivíduos amostrados foram distribuídos em classes de diâmetro e o valor de importância (VI) foi calculado para as espécies. Foi também realizada uma Análise de Correspondência Retificada (DCA) para verificar se há distinção entre os três setores. Constatou-se que o setor onde ocorreu corte raso e queima da vegetação possui maior abundância e riqueza, porém, tem a pior equabilidade, o que condiz com os efeitos das perturbações, corroborado também pela distribuição nas classes diamétricas e pelas espécies de maior VI. O setor que não possui perturbações e que está situado em um local com maior variedade de ambientes apresentou diversidade, estrutura e composição condizentes com estas situações. Já o outro setor, que não sofreu corte raso, está submetido ao pisoteio pelo gado e é ambientalmente semelhante ao primeiro setor, apresenta parâmetros condizentes com a ausência de perturbações severas. Por outro lado, a menor diversidade ambiental também o diferencia, o que o coloca em uma situação intermediária. Palavras-chave: ecologia florestal; impactos ambientais; Floresta Estacional Semidecidual. ABSTRACTForest fragmentation is one of the main causes of biodiversity loss, directly affecting the ecological processes. This study aimed to evaluate tree diversity, structure, and composition parameters in three sectors of a forest fragment with distinct disturbance records. The arboreal vegetation was evaluated in twenty-four 10 × 10 m plots, sampling a total of 1,228 living individuals. We calculated Shanon's diversity index, Pielou's equability, and jackknife estimators of first and second orders. The sampled individuals were distributed in diameter classes and the importance value (VI) was calculated for each species. It was made a Detrended

Soil is a relevant driver of taxonomic, functional and phylogenetic composition at local scales. However, the mechanisms by which the soil act in these components or how these components interact with each other are not elucidated. Herein, we propose to understand the role of soil (environmental filtering) on the turnover of taxonomic and phylogenetic components and their role in determining the functional composition of Seasonally Dry Tropical Forest (SDTF) communities. We sampled all the arboreal individuals with Diameter at Breast Height equal to or higher than 3 cm and collected soil variables of 25 units from five SDTF fragments located in the Brazilian Caatinga Domain. These data enabled us to obtain the taxonomic, functional and phylogenetic composition of each plot, which were then analyzed by Structural Equation Models jointly with the soil variables. Our results suggest that the soil conditions select specific phylogenetic lineages from a regional species pool according to the adaptive potential, which affects the distribution and abundance of species (taxonomic composition). However, it was not possible to establish a direct relationship between the phylogenetic composition and the taxonomic composition, possibly due to the use of labile functional traits in the analysis. We also found that soil acts directly on the functional composition, leading to a differential success of individuals which would represent a direct and indirect effect of taxonomic composition on the functional composition. Thus, we found community aspects result from different ecological mechanisms which act in a continuous and progressive way between functional, phylogenetic and taxonomic composition.

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