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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.

Studying community phylogenies along elevation gradients can inform us about the influences of environmental conditions on the structuring communities, and therefore allow predictions on how future environmental changes may affect them. The aim of the work was to evaluate the processes that govern tree communities along an altitudinal gradient in an upper montane Atlantic Forest in the Mantiqueira Range, southeastern Brazil. To do so, we analyzed the phylogenetic structure of angiosperm tree communities in four elevations (ranging from 1500 to 2100 m) and verified if it varies significantly with altitude. We also analyzed the phylogenetic beta diversity among local angiosperm tree communities along the altitudinal gradient. Further, we evaluated the soil and temperature influences over these communities. The results showed tendency of increasing phylogenetic clustering with the elevation. We also verified that the phylogenetic lineages of the tree communities are replaced along the altitudinal gradient influenced by changes in temperature and soil, indicating phylogenetic niche conservatism. This suggest that these communities could move to higher altitudes in a global warming scenario, and that would change their species composition and abundance due to changes in soil along the altitudinal gradient. Thus, the highest areas would be threatened as they would not have higher altitude locations to migrate to. In addition, phylogenetic lineages which only occur, or occur in their large majority, at highest altitudes (i.e., Cunoniaceae and Winteraceae) would be locally extinct by the current (or future) climatic scenario.

Aim of study: Aassessing the existence of consistent co-occurrence between tree species that characterize seasonal tropical forests, using the association rules analysis (ARA), that is a novel data mining methodology; and evaluate evaluating the taxonomic and functional similarities between associated species.Area of study: forty-four seasonal forest sites with permanent plots (40.2 ha of total sample) located in Southeast Brazil, from which we obtained species occurrences.Material and methods: we applied association rules analysis (ARA) to the dataset of species occurrence in sites considering the criteria of support equal to or greater than 0.63 and confidence equal to or greater than 0.8 to obtain the first set of associations rules between pairs of species. This set was then submitted to Fisher’s criteria exact p-value less than 0.05, lift equal to or greater than 1.1 and coverage equal to or greater than 0.63. We considered these criteria to be able to select non-random and consistent occurring associations.Main results: We obtained a final result of 238 rules for semideciduous forest and 11 rules for deciduous forests, composed of species characteristic of vegetation types. Co-occurrences are formed mainly by non-confamilial species, which have similar functional characteristics (potential size and wood density). There is a difference in the importance of co-occurrence between forest types, which tends to be less in deciduous forests.Research highlights: The results point to out the feasibility of applying ARA to ecological datasets as a tool for detecting ecological patterns of coexistence between species and the ecosystems functioning.Keywords: data mining; coexistence; semideciduous forests; deciduous forests; biotic interaction.

In the neotropical region, seasonally dry tropical forests (SDTF) are commonly associated with scatterly distributed limestone outcrops, known for harbouring high numbers of endemic species and genera. In the context of lacking knowledge on fine-scale vegetation and environmental heterogeneity of these geoecosystems and having a limestone outcrop in eastern Brazil as a case study, we address the question: how important are limestone outcrops for SDTF tree community composition, structure, function and evolution? We distinguished five habitats related to position and distance to the outcrop, and within each of 25 sampled plots (five per habitat), we identified and measured the diameter of all living tree individuals and collected soil samples for chemical and textural analyses. We investigated taxonomic and phylogenetic substitution across the habitats and fitted linear models to test the effects of habitat type, soil fertility and texture on taxonomic/structural, functional and phylogenetic parameters. We found striking taxonomic and phylogenetic differentiation among the habitats, especially related to recent diversification, with soil fertility and texture largely accounting for variations in all analysed parameters. Given the predominant roles of vicariance and in situ diversification believed to have given rise to the current patterns of endemism and diversity of eastern Brazil SDTF, we argue that the conditions presented by limestone outcrops, including aridity and high fertility, may have favoured the persistence of SDTF lineages during the Quaternary environmental changes, highlighting their role as litho-refugia. In order to complete this biogeographic puzzle, we encourage other fine-scale assessments of outcrop-associated SDTF from the phylogenetic viewpoint.

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.

Understanding vegetation-environment relationships enables perceiving past and present patterns and to predict responses to future scenarios, thereby being useful for conservation and understanding evolutionary processes. In this context, the objective of our study was to test the hypothesis that niche processes at local scales (< 1 km2) are significantly expressive in plant communities structuring. For this, we selected the more representative and widely distributed sampled species, and then modelled their representativeness as a function of edaphic variables. The data were obtained in four fragments of seasonal semi-deciduous forests located in a transition area between the Atlantic and Cerrado biogeographic domains, Brazil. A total of 92 plots with 63 of 400 m2 and 29 of 300 m2 were randomly distributed in the fragments. Individuals that reached the inclusion criterion (circumference at breast height ≥ 15.7 cm) in each plot were measured and identified and soil samples were also collected. Then, we calculated the relative abundance and relative basal area in each plot. All species showed significant relationships with the soil variables, as their representativeness showed to be correlated (positively and/or negatively) with at least one restrictive fertility or texture condition. Therefore, the results confirm the tested hypothesis, evidencing the niche processing role in community structuring through the species tolerance degree to soil conditions.

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.

The relationship between biodiversity and ecosystem functioning is one of the most currently acclaimed ecological topics. One remarkable aspect of tree communities in tropical forests and savannas is the concentration of individuals into few species or simply the species stem dominance. In addition, species dominance in biomass and productivity are indicators of how much it can affect ecosystem processes. Here, we investigated if tree species dominance in abundance is followed by a dominance in biomass and productivity, and if there is consistence in the functional traits associated to dominance in biomass, productivity, and stem abundance in neotropical savannas of Central and Southeastern Brazil. Our findings showed slightly stronger functional (biomass and productivity) dominance compared to the abundance dominance, with 3.4 and 4.2% of the species accounting for 50% of the biomass and productivity, respectively, and 4.3% of the species accounting for 50% of the individuals. There were overlaps, but mostly mismatches, between dominant species lists for biomass, productivity, and abundance, especially in the top three species. We found that the same traits which make a species capable to deal with savanna environmental odds (i.e., adaptations) and achieve high abundance, also make it possible for this species to reach larger diameters and consequently dominance in biomass. Species relative contributions to productivity responded to bark thickness, wood density and maximum potential size. The fact that just a few species concentrate most savanna trees, biomass, and productivity show a high level of adaptation of this species to the environmental conditions found in this biome. Regardless, the conservation of the entire pool of species is crucial because climate change, land use and species invasion might cause shifts in the vegetation structure and function.

Forest dynamics are driven by a myriad of factors and link directly to ecosystem services. The dynamics of the highly degraded Brazilian Atlantic Forest (AF) hotspot is mostly driven by its anthropogenic context. Currently, most of the AF region is composed of small disturbed secondary forest fragments that have received partial or full environmental protection with recent environmental norms. Such protection prevents further disturbances and consequently shifts the course of forest dynamics and ecosystem services in AF. Here, we assess long-term forest dynamics trends of a small secondary AF fragment to test the hypothesis that disturbed AF fragments are reaching advanced successional stages. We used a unique dataset of 126 permanent subplots (totaling 5.04 ha) monitored for 30 years (8 inventories between 1987 and 2017) of a disturbed secondary AF fragment (6.35 ha) that has been fully protected since 1986. In each inventory, we measured all living trees with a diameter at breast height (DBH) ≥ 5 cm and counted survivors, recruits and dead individuals between intervals. We monitored the temporal trends of (i) structural variables (biomass, tree density and species richness), (ii) functional composition (wood density and maximum potential size), (iii) and species dominance. Our results indicate that, now under full protection, the fragment is shifting towards a late successional stage: we observed increasing biomass, decreasing tree density (self-thinning) and increasing abundance of late-successional species with conservative strategies. Species richness and dominant species composition were stable throughout the monitoring period, suggesting an absence of substantial changes in community assembly. These results underscore the role played by small secondary AF fragments in ecosystem service provision (e.g., carbon uptake and shelter for biodiversity) and point to their forest dynamics trends.

Obtaining high-quality information on vegetation attributes directly linked to ecosystem services in tropical forests, such as carbon stock and biodiversity, is essential to develop ecological information to be used in planning conservation strategies. Defining the optimum vegetation sample plots size is an important part of the process of obtaining information, since is crucial for its quality, and also for its financial costs and time required. In this context, we evaluated whether: (i) the optimum plot size selected in two approaches (basal area/carbon stock vs biodiversity) are different since they are associated with different ecological drivers; (ii) different tropical forests vegetation types present different optimum sample plot size due to their ecological specific attributes, such as species composition, structure and functioning. For this we evaluated the vegetation sample plots optimum size of different vegetation types of tropical savanna and forest of broad occurrence in the tropics (Atlantic Semideciduous Forest – ASF; Cerrado Woodland – CW; Cerrado Forest – CF; and Seasonally Dry Tropical Forest - SDTF), in two approaches: forest basal area and carbon stock, since they are related variables; and biodiversity variables by species composition similarity and heterogeneity in communities. We used 4 forest fragments in Brazil that were sampled in a way that allowed the arrange of subplots to form different plot sizes. In order to evaluate the optimum sample plot size in the basal area/carbon stock approach we used four methodologies, in which the obtained variability was compared to a reference size (1000 m2). For the biodiversity approach we used the floristic similarity and composition heterogeneity between units as metric, evaluating differences in the similarity patterns and possible reductions or increases in variability compared to the reference size. We found there are no significant differences for biodiversity variables between sample plot sizes for all vegetation types, thus the optimum size may be selected using just the basal area/carbon stock approach. In the basal area/carbon stock approach, most of the evaluated methods generally presented lower plot size values compared to the reference size (1000 m2) in all vegetation types, except for the ASF. There are differences between vegetation types that may be grouped in two groups related to the optimum size selected, that are related to their ecological restriction patterns: CW, CF and SDTF with optimum size between 600 and 1000 m2; and the second with ASF, with optimum sample plot size between 1000 m2 and 1400 m2.

The resilience or sensitivity of seasonally dry tropical forests (SDTF) to climate change remains an important issue because of their biodiversity and ecosystem services provision. Understand the underlying ecological processes of SDTF is crucial for the development of conservation and management strategies. We tested the hypotheses that SDTF tree species richness, above-ground woody biomass (AGWB), species and phylogenetic compositions are related to climate, soil and their interactions. We sampled 16 old-growth forest sites (313 plots) of SDTF within a 290 km latitudinal gradient. The sites are located in the transition zone between Caatinga and Cerrado biogeographic domains, and are near from Atlantic domain (~100 km). In each site we collected data on vegetation (trees with diameter at breast height ≥3 cm) and soil, and obtained climate data from WorldClim. Almost all vegetation attributes were significantly related to climate and soil. Soil texture mediated the effects of precipitation for tree species richness, AGWB and phylogenetic composition. Tree species richness decreases with annual precipitation but increases under less seasonal conditions; water availability leads to increases in AGWB and drives changes in both taxonomic and phylogenetic composition in these environments. Our findings indicate that tree species richness, above-ground woody biomass, taxonomic and phylogenetic composition of SDTFs are, in general, vulnerable to drought events even from local to regional scales and show the importance of local-scale aspects to understand SDTF diversity and ecosystem functioning; and provide useful information for conservation and management strategies.

This study aimed to evaluate the occurrence patterns and role of volunteering in Brazilian protected areas in facing the scenarios of reduced public funds for conservation. Thus, we analyzed volunteer work documents in 210 Brazilian conservation units and carried out a meta-analysis on the proposed objectives, activities offered, the prerequisites for participation and the provisions offered to volunteers. Parks have the highest demand for volunteers (i.e. the type of protected area where volunteers are needed the most to perform volunteer work), as well as for the objectives, activities and prerequisites. Volunteering is motivated by objectives associated with providing practical experience, but in activities associated with public use, visitation and infrastructure. The desired profile is associated with adults with advanced education who have experience in the environmental sciences, and there is no incentive for participation by local resident. The provisions offered to volunteers are mainly related to work execution itself, such as accommodation, food and transportation, despite the relatively low supply of training courses and personal protective equipment. We argue that volunteer actions are being encouraged to meet both the need for professionals and the reduced public funds allocated to conservation. In this sense, this incentive has motivated volunteer precariousness, since the ideal volunteer activity motives are distorted, as well as the services rendered. Knowledge of this process is important to assist in planning public policies and initiatives for conservation, as well as in models for restructuring voluntary action that can achieve both the objectives of volunteer action (i.e. inclusion of the surrounding community and society in the conservation), as well as to contribute to advances in the ecology and in the effectiveness of natural area conservation. Keywords: Conservation units, Volunteering, Nature conservation, Non-remunerated activity

Caatinga represents one of the two major centers of Seasonally Dry Tropical Forests (SDTF) and is completely inserted in the Brazilian territory. The present work aimed to evaluate the structure of two micro-environments and relate them to environmental variables. Twenty 20 × 20 m plots were placed in which we measured the height and CBH and made the botanical identification of all trees with CBH ≥10 cm. The CCA and indicator species analysis presented a clear distribution of species according to the micro-environments. We concluded that the presence of limestone slabs provided the formation of microhabitats, thus influencing the distribution and composition of tree species, what characterized the phytoecological unit here referred as “furados”. RESUMO A caatinga corresponde a um dos dois maiores núcleos das Florestas Tropicais Sazonalmente Secas (FTSS) e se encontra totalmente inserida no território brasileiro. Objetivou-se com este estudo avaliar a estrutura de dois micro-habitats relacionando-a com as variáveis ambientais. Foram alocadas 24 parcelas, nas quais mensuramos o CAP e fizemos a identificação botânica de todos os indivíduos arbóreos com CAP ≥ 10 cm. Com a presença de lajedos de calcário na área, foi possível distinguir dois micro-habitats. A CCA e a análise de espécies indicadoras mostraram uma nítida distribuição das espécies de acordo com os micro-habitats. Concluímos que a presença dos lajedos de calcário proporcionou a formação dos micro-habitats, influenciando na distribuição e composição das espécies arbustiva-arbóreas, caracterizando a unidade fitoecológica aqui denominada como “furados”.

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 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.