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Aims We aimed at disentangling the effects of spatial distance, current and past environmental dissimilarity, and their combinations on tree community taxonomic and phylogenetic turnover by addressing the following questions: (i) Is tree community taxonomic and phylogenetic turnover related to the indirect effects of spatial distance via environmental dissimilarity? (ii) Does tree community taxonomic and phylogenetic turnover respond to paleoclimate (Last Glacial Maximum and Mid-Holocene)? Methods The study was carried out in 14 Atlantic rainforest sites in Brazil (20.4 ha sampled) containing 615 tree species from 83 plant families. We obtained plot-level geographic coordinates and soil variables and site-level bioclimatic variables in the current, Mid-Holocene and Last Glacial Maximum. We used structural equation models with a distance-based approach to (i) test the direct effects of spatial distance and environmental dissimilarity and (ii) test the indirect effects of spatial distance via environmental dissimilarity on taxonomic (Bray–Curtis distance) and phylogenetic turnover (Comdist and Comdistnt distances). Important Findings Our results suggest a weak indirect effect of spatial distance via environmental dissimilarity on taxonomic and phylogenetic turnover. Tree community turnover was driven by the direct effects of neutral, niche-based and historical processes. Thus, we inferred that the paleoclimate (historical processes) promoted the selection of the clades that gave rise to the current flora, while spatial distances (neutral processes) limited the dispersal range of species from the regional pool and environmental conditions (niche-based processes) locally selected the taxa that are able to persist.

In tropical montane forests, compositional and structural changes are commonly driven by broad-scale altitudinal variation. Here, given the lack of knowledge on small-scale vegetation changes and temporal dynamics, we address the effects of small-scale variations in soil and altitude on tree community structure, temporal dynamics and phylogenetic diversity in a semi-deciduous tropical forest of the Atlantic Forest Domain, southeastern Brazil. In 2010 and 2015 we sampled thirty plots of 400 m2, set up along an altitudinal gradient between 1000 and 1500 m a.s.l.. In each plot, we collected soil samples for chemical and textural analyses. We fitted linear models to test the effects of altitude and soil on community dynamics and phylogenetic parameters. Altitude and soil explained the spatial variation in number of individuals and phylogenetic diversity metrics. From lower to higher altitudes, we found decreasing fertility, increasing tree density and decreasing phylogenetic diversity. Altitude significantly influenced the increases in total biomass (from 240.9 to 255.4 t ha−1) and individual biomass (from 0.15 to 0.17 t) recorded in the interval. And while community temporal dynamics had rates of 1.96% for mortality, 1.02% for recruitment, 1.61% for biomass loss and 2.81% for biomass gain, none of them were explained by altitude or soil. Temporal species substitution averaged 0.1 in the interval. Altogether, these results suggest that the small-scale variations in altitude and soil likely determine the conditions and resources that drive community assembly and structure, which are expressed by spatial variations along the altitudinal gradient. At the same time, temporal patterns were not influenced by altitude-related environmental variation, resulting in a similar dynamic behaviour across the gradient, suggesting that broad-scale factors may play a more important role than local ones.

Species–habitat associations can be used as a proxy for species niches. Previous research has shown that niche plasticity may increase diversity in plant communities, and that plasticity may be linked to variations in species fitness. Spatial and temporal aspects of the niche are of interest to understand community structure, but the temporal dimension is often difficult to incorporate in ecological research. In this study, we investigated if species–habitat associations are stable across time, and if they are not, whether niche plasticity promotes variations in species fitness and increases in diversity. We modeled the representativity of 36 species as a function of soil variables and slope in an Atlantic tropical wet forest located in southeast Brazil, as well as their interactions with time, monitored over a period of 17 years. We found niche plasticity to be a common mechanism among the studied species in the studied time period. Niche plasticity was neither significantly related to variations in species fitness nor to changes in species richness, but had a negative effect on diversity when species abundance was accounted for (Shannon and Simpson indexes). We were able to make relevant observations of species–environment relationships over time, such as their niche stability and its effects on the community. We argue that this knowledge is useful in a context of climate change for revealing mechanisms used by plants to cope with environmental oscillations.

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 Sao 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.

Our work aimed to test the hypothesis that soil microscale heterogeneity act as a community ecological driver, increasing diversity and promoting structural shifts on the Seasonally Dry Tropical Forest (SDTF) tree community. We evaluated the relationship between microscale edaphic variations and floristic–structural patterns of tree communities in a SDTF fragment located in the southern end of the Brazilian Caatinga domain. Vegetation and soil data were obtained through 27 sample units of 400 m2 (20 m × 20 m), within each one we measured and identified at species level all arboreal individuals with Circumference at the Breast Height greater or equal to 10 cm, and also collected the soil samples. Through the data we evaluated soil variation influence on the tree community structural and floristic patterns trough generalized linear models. Soil explained the small-scale structural and floristic variations, contributing significantly to biomass, sprouting and to floristic relationships between sample units. It was also observed a possible relation of the result with the Caatinga domain biogeographic history, due the presence of Sedimentary Caatinga species, which are not expected for the study region. Soil plays an important role in driving small-scale complexity and diversity of SDTF, but we also suggest that Caatinga biogeographic events have influence on the high heterogeneity patterns.

Background: Seasonally Dry Tropical Forests (SDTF) are recognized by their great biological diversity, but little is known about their temporal patterns, which may be crucial in a changing world. Here we aimed to characterize the SDTF dynamic patterns in floristic and structural changes, and also to evaluate shifts in dynamic rates and structural attributes such as richness, number of trees and biomass. Our hypothesis is that SDTF tree communities have their dynamic characterized by temporal fluctuations related to an instability pattern, in according to the already found for others tropical forests. For this we used a data of 42 400 m² plots in three fragments in the Brazilian Arboreal Caatinga, measured in 2005, 2010 and 2015. We evaluated temporal changes in richness, species composition, trees density, biomass and rates of tree mortality and recruitment; and also rates of biomass gain and loss. Results: We found a pattern of floristic composition stability, but with changes in structure and dynamics. There was a tree density decrease driven by constant mortality and by recruitment decrease, and biomass increase due to decrease in biomass loss and to increase in biomass gain. The biomass increase was main related to a small set of dominant species that are the most representative in the community dynamics. Conclusion: SDTF dynamics are related to stability in species composition, but with structural changes towards higher biomass stocks. The results are main related to community dynamics and to SDTF attributes such as climatic seasonality that drives the local ecological processes.

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.

Our objective was to evaluate the floristic and structural relationships between Canga tree communities and other vegetation types inserted in the physiognomic units set, in order to test the hypothesis that these communities have unique characteristics due to their specific environmental conditions. For this, we compared the structural and floristic attributes of Canga vegetation with adjacent semideciduous seasonal forest, Savanna and ecotone areas, evaluating the similarity in its behavior. Our results demonstrate the existence of distinct relationships among vegetation types in relation to different perspectives, related to macro-scale environmental attributes and to the phytogeographic context. In general, Canga tree vegetation has its structure associated with open vegetation types, such as the Cerrado (Savanna) and its composition associated with forest vegetation types, constituted by a community with specific ecological characteristics. Our results suggest the presence of ferruginous soils as a factor that contributes to environmental and ecological heterogeneity in vegetation matrices.

The knowledge about the influence of habitat variables is essential to understand the underlying ecological patterns in vegetation. This study compared the floristic composition of two forest communities located in different altitudes. Associated with this comparison, we used a methodology where habitat descriptor variables were scaled and interpreted by the biotic set sampled. We constructed one matrix with scores given to physical, biotic, vegetation, and anthropogenic variables in the field and one matrix with the species sampled and performed multivariate analyses. We found that the floristic communities differ between the different altitudes and that the methodology used showed significant variables for the ecological characterization of the sampled habitat. RESUMO O conhecimento sobre a influência das variáveis ambientais é essencial para que se compreenda os padrões ecológicos atuantes sobre a vegetação. Este trabalho comparou a composição florística de duas comunidades florestais localizadas em diferentes altitudes. Associada a essa comparação, foi utilizada uma metodologia onde variáveis descritoras do ambiente foram escalonadas e interpretadas junto ao conjunto biótico amostrado. Através de uma matriz, com a pontuação dada em campo para variáveis físicas, bióticas, da estrutura da vegetação e de antropização, e de outra, contendo as espécies amostradas, análises multivariadas foram utilizadas. Constatou-se que as comunidades diferem floristicamente entre as diferentes altitudes e que a metodologia utilizada indicou variáveis importantes para a caracterização ecológica dos ambientes amostrados.

Seasonally Dry Tropical Forests (SDTF) are gaining recognition as a habitat of global conservation significance. However, these forests often occur on rich soils, and are therefore prone to disturbance by agricultural activities. Across their range, many SDTFs are in various stages of regeneration, although little is known about their regeneration dynamics and temporal change in general. To fill this knowledge gap, we studied the changes in species diversity and community structure of an SDTF tree community with a history of past selective logging located in northern Minas Gerais, Brazil. We hypothesized an increase in species diversity and biomass-related parameters, along with a reduction in stem density for the community after five years of regeneration. In 2005, we measured all tres (diameter ≥ 3.18 cm at 1.3 m) within twenty 20 x 20 m (400 m²) plots in the patch, and we remeasured the trees in 2010. Between the two censuses, we found no significant changes in species richness and diversity, suggesting that species accumulation had leveled out. However, we found significant gains in tree basal area and recruitment, suggesting continual regeneration. Diameter class distributions of the five most abundant tree species showed similar patterns. We conclude that past disturbances can have ongoing effects on SDTF vegetation, although inter-annual variations may also play a regulatory role on community dynamics., Los Bosques Tropicales Secos Estacionales (BTSE) gozan de reconocimiento como hábitat de importancia global para la conservación. Sin embargo, estos bosques se encuentran a menudo en suelos ricos, y, por lo tanto, son propensos a perturbación por actividades agrícolas. En su rango de distribución, muchos BTSE están en varias etapas de regeneración, pero se sabe poco acerca de su dinámica de regeneración y cambio temporal en general. Para llenar este vacío de conocimiento, se estudiaron cambios en la diversidad de especies y la estructura de una comunidad de árboles de un BTSE con una historia de tala selectiva en el norte de Minas Gerais, Brasil. Se hipotetizó un aumento en la diversidad de especies y parámetros relacionados con la biomasa, junto con una reducción de la densidad para la comunidad después de cinco años de regeneración. En 2005, todos los árboles (diámetro ≥ 3,18 cm a 1,3 m) fueron medidos dentro de veinte parcelas de 20x20 m (400 m²), y fue repetido el mismo procedimiento en 2010. Entre ambos censos, no hubo cambios significativos en riqueza de especies ni diversidad, lo que sugiere que la acumulación de especies se había estabilizado. Sin embargo, hubo ganancias significativas en área basal y en el reclutamiento, lo que sugiere una regeneración continua. Las distribuciones diamétricas de las cinco especies de árboles más abundantes mostraron patrones similares. Se concluyó que los disturbios pasados pueden tener efectos continuos sobre la vegetación del BTSE, aunque las variaciones interanuales también pueden desempeñar un papel regulador en la dinámica de la comunidad.

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.

A 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. Forest 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 Correspondence Analysis (DCA) to verify whether there were significant distinctions between the sectors. It was noticed that the sector where there was clear cutting and vegetation burning in a recent past had higher abundance and richness but also the worst equability. That corresponds to the effects of perturbation as confirmed by the tree diameters and the presence of species of greater importance value. The sector that had no record of disturbance, situated in a location with greater variety of microenvironments, presented diversity, structure, and composition consistent with a no disturbance scenario. The other sector, which did not have clear cutting, was subjected to cattle trampling presented ecological parameters consistent with the absence of major disturbances. On the other hand, this third sector had the smallest environmental diversity, which puts this last sector in an intermediate situation.

We tested the hypothesis that plant populations in natural fragments have distinct ecological behavior in relation to anthropic fragments. We selected the species Myrcia splendens (SW.) DC. in 2 forest fragments located in southeastern Brazil that present different origins and landscape contexts. The natural fragment originates from landscape relief variations and is inserted in a native grassland matrix, while the anthropic fragment originates from fragmentation due to area conversion and is inserted in an agricultural matrix. We established transects covering an area from one border to the other in each fragment, and we established subunits of 400 m2 within them. Within each subunit we measured all individuals of M. splendens at all establishment stages (seedlings to established trees). We monitored population behavior in the two fragments for 4 years, evaluating their spatial structure, temporal behavior, and age structure. The two populations present distinct ecological behaviors associated with their different origins and landscape contexts; the natural fragment is exposed to disturbances it has adapted to throughout the evolutionary process, whereas the anthropic fragment is subject to new evolutionary disturbances, such as effect edge, cattle, and recurrent fire.

The objective of this work was to evaluate if the soil heterogeneity expressed by the different soil classes would condition tree communities with different dynamic behaviors. The data were collected from 25 plots sized 20 × 20 (400 m²), 10 of them with Inceptisols, 9 with Ultisols, 5 with Entisols B and 1 with Entisols A. All individuals with DBH ≥ 5.0 cm in the plots were sampled in 2000, 2005, 2009 and 2015. Rates of mortality, recruitment, gain, loss and turnover dynamics in number of individuals and basal area were estimated for each soil class. The tree communities present in the soil classes showed no differences in the dynamic behavior to the point of expressing edaphic fragment heterogeneity. The differences are associated with stochastic fluctuations in rates caused by small disturbances, suggesting little influence of the soils on the dynamics of small-scale communities.