Resiliência do banco de sementes do solo de Floresta Estacional Semidecidual frente às mudanças climáticas

Abstract

Seasonal forests can be more negatively impacted by climate change when compared to humid forests, as they are under environmental stress due to fluctuations in water and thermal regimes. The soil seed bank is one of the mechanisms that guarantee the perpetuity of vegetation in forests, and it is important to study it to understand its behavior in the face of climate change in the present and in the future. As well as, studies on the ecophysiological behavior of species in the initial stage of ecological succession, in different environmental conditions, are important for understanding the functioning of ecosystems in future climate scenarios. Thus, the objective of this work is to evaluate the impact of climate change on the soil seed bank in a remnant of Semideciduous Seasonal Forest, in the National Forest of Pacotuba. The hypotheses were tested that: the seed bank will respond to climate change by modifying its composition and density of emerging species; the ecophysiology of emerging seedlings will be influenced by the different climatic conditions imposed. In 12 plots (40 m x 50 m = 2.4 ha) 48 composite samples of the seed bank were collected, with 12 replications for each of the four treatments. Conditioned in plastic trays, the samples were distributed in acclimatized greenhouses, where two environments with controlled climatic conditions were established (current and future scenarios - Representative Concentration Pathways 8.5 (RCP8.5), with two levels of water (maximum retention capacity of water and 50% of the maximum water retention capacity), where Cur: current scenario without water restriction; Cur_WR: current scenario with water restriction; RCP8.5: future scenario without water restriction; RCP8.5_WR: future scenario with water restriction Species identification was carried out, as well as obtaining phytosociological parameters (density and frequency) and ecological classifications (ecological group, dispersal syndrome and way of life). Leaf area and dry mass production were also evaluated. In order to verify the influence of climate changes on the seed bank, differences in composition, density were evaluated (non-metric multidimensional scale analysis - NMDS and multivariate analysis of similarity - ANOSIM) and statistical analyzes were performed (analysis of variance (ANOVA)) to assess the interaction between water levels and environments. Three species that occurred in the four environments were selected (Solanum asperum Rich., Solanum cordifolium Dunal and Trema micrantha (L.) Blume) to carry out the ecophysiological analyses. To verify the influence of climate changes for the three species studied, analysis of variance was performed and the means of each treatment were compared using the Tukey test (p≤0.05). The results revealed differences in the floristic composition between the current and future scenarios, and it was observed that in all environments there were exclusive species. In the current scenario, there was a greater occurrence of individuals and species richness, regardless of the water condition. The invasive species Muntingia calabura L. occurred in all evaluated environments. The results showed a strong influence of climate change on the ecophysiological aspects of early successional stage species. The knowledge obtained about the ecophysiology of the species studied revealed the susceptibility of the species to climate change.