Water availability drives gradients of tree diversity,structure and functional traits in the Atlantic-Cerrado-Caatinga transition,Brazil

Aims Climate and soil are among the most important factors determin-ing variation in tree communities,but their effects have not been thoroughly elucidated to date for many vegetation features.In this study,we evaluate how climate and soil gradients affect gradients of vegetation composition,species diversity and dominance,structure and functional traits(seed mass and wood density)using over 327000 trees in 158 sites distributed along environmental gradients in the transitions among the Atlantic forest,Cerrado and Caatinga in Minas Gerais State(MG),Brazil(nearly 600000 km2).Methods Gradients in species,genus and family abundance in addition to basal area,stem density,species diversity(Fisher’s alpha),domin-ance percentage,seed mass and wood density were correlated using multiple regressions with environmental variables,as summarized in four principal component analysis axes(two climatic-precipi-tation seasonality and temperature range-and two edaphic-soil fertility and soil moisture).Additionally,ordinary kriging maps were used to better illustrate the gradients.Important Findings Multiple regression models indicate that all variables but domin-ance percentage were affected by one or more of the environmental gradients,but the average R2 was low(26.25%).Kriging maps rein-forced the patterns observed in the regression models.Precipitation seasonality and soil moisture gradients were the most important gra-dients affecting vegetation features.This finding suggests that water availability is an important determinant of vegetation features in these vegetation transitions.

Soil and altitude drive diversity and functioning of Brazilian Páramos(campo de altitude)

Aims the vegetation on Brazilian Páramos consists of assemblages that are driven mainly by the influence of strong environmental filtering.It is very important to understand the effect of environmental varia-tion on taxonomic diversity and on functional diversity.considering the lack of information about the functional diversity in Brazilian Páramos,we analyzed for the first time the effects of altitude and edaphic attributes on functional traits,as well as on taxonomic and functional diversity.We also wanted to answer the questions:Which ecological strategies are favorable in high-altitude grassland?Does soil attributes determine distributions of traits in high-altitude grassland?considering the studied altitudinal gradient is altitude an important variable in the community assembly?Methods the study was conducted on three mountains:Mammoth(1850 m),Elephant(1790 m)and totem(1690 m)in Serra do Brigadeiro State Park,Minas Gerais State,Brazil.those mountains represent the‘Serra das cabeças’,a smaller ridge that is surrounded by the Atlantic Forest,one of the 25 hotspot of biodiversity.the samples were taken using 100 plots of 1 m2 per mountain that were randomly distributed.All plants except mosses were sampled.the taxonomic diversity was evaluated using richness,Shannon diversity,effective number of species and Pielou evenness.For the functional diver-sity,we considered the functional richness,functional evenness and functional divergence.Generalized linear models(GLM/Poisson and quasi-Poisson)were used to evaluate the effect of abiotic variables(altitude,soil depth and soil chemical attributes)on biotic variables(number of species and individuals,life form,dispersal and fruit type)and ordinary least squares regression to evaluate the effect of abiotic variables on the functional and taxonomic diversity.Important Findingsthe soil variables presented a considerable edaphic gradient associated with altitude.the soil in Serra das cabeças plays an important role for the plant diversity:richness and diversity index were positively related with fertility.With regard to the life form,nanophanerophytes tended to increase with altitude and soil depth,while therophytes tended to decrease with altitude.the dispersal type was also associated with the abiotic variables:autochory decreases with altitude,while zoochory increases.Functional richness increases with fertility and the functional evenness with altitude.the studied gradient showed that altitude is working as a filter for functional traits and indices and is,together with soil attributes,an important determinant for the distribution of plants on Brazilian Páramos.