Anthropogenic disturbances and ecological modification on Atlantic Forest tree community

Abstract

The disturbances in tropical forests are a fundamental mechanism for tree community dynamics and the maintenance of ecosystem ecological processes. However, when these are from anthropogenic origin, they can negatively affect biodiversity on its structure, composition and functionality. The present study sought to evaluate the history effects of anthropogenic disturbances, their relationship with abiotic factors in the structuring Atlantic domain tree communities. For this purpose, two hypotheses were tested, namely: (i) the history of anthropogenic disturbances affect the floristic composition over time, and it is expected that most impacted areas will change in the temporal gradient composition, and (ii) past anthropogenic disturbances modify the communities’ functionality, and increasing its intensity would decrease carbon uptake, seed dispersal capacity and successional dynamics. Tree community survey consisted of 12 forest fragments sampling in the south of Minas Gerais state, making up 544 plots, where the diameter at breast heigth (DBH) was measured from 5.0 cm for vegetation inclusion; textural and chemical variables for the soil and 19 bioclimatic variables for mesoregion climatic characterization from the Worldclim 1.4 database. The past anthropogenic impacts characterization in the region made by Pereira (2003) was also obtained, and using the same methodology, another characterization was also made by this study for the year 2019. Subsequently, mixed generalized linear models (GLMMs) were created in order to evaluate if the communities’ ecological variables respond to the disturbances effects, with this, the fragment was used as a random factor to deal with pseudoreplication. A total of 36638 individuals from 550 species representing 76 families were found in the 12 fragments sampled. The results showed that anthropogenic disturbances significantly influenced the zoochory and autochory dispersion syndromes in the models, where its greater intensity results in greater autochorous species abundance and lower zoochoric species abundance. Productivity responded inversely to anthropogenic disturbances, thus its increase implied a productivity decrease. The community-weighted mean of wood density (CWMWD) responded significantly, and the anthropogenic disturbances increasing impact implied its increase. On the other hand, the anthropogenic disturbances and soil variables had no significant effect on aboveground biomass. Soil was an important driver of beta temporal diversity, CWMWD, and autochory, unlike the climate that did not show any effect on ecological variables. Therefore, our results clearly demonstrate that, in fact, anthropogenic disturbances can be an important driver in modifying the tree communities ecological parameters, and can affect ecosystem services upon which humanity depends.