Dinâmica das leguminosas e não leguminosas em uma floresta secundária sazonalmente seca

Abstract

In forest succession there are changes in the structure and niches of arboreal vegetation. In neotropical forests, several species coexist, however the soil and climatic characteristics act as an ecological filter and select the species most adapted to the imposed characteristics. The knowledge of the functional traits of the species allows the formulation of conservation strategies, through the foreseen climatic changes. The objectives of the present study were to investigate the performance of species from different functional groups, as well as their contribution to litter input, nutrients (N, P and C) and decomposition in the legume-dominated community, subjected to water seasonality. The study was carried out in a secondary fragment that makes up the Legal Reserve of the Environmental Education Pole of the Federal Institute of Espírito Santo, Ifes - Campus de Alegre (PEAMA), Alegre - ES. In 2013, 19 plots of 400 m2 of area (20 x 20 m) were installed, distributed every 200 m throughout the entire area of the fragment in order to study the tree size. In 2017, 11 plots were selected from these to measure DBH greater than or equal to 5 cm to evaluate the performance of functional groups (N-fixing legumes, non-fixing legumes and non-legumes). Litter deposited and the canopy coverage index (ICC) were collected for two years (Oct/2017 to Sep/2019). The accumulated litter collections were carried out in the rainy and dry periods, being Mar/2019 and Sep/2019, respectively. In addition, a study of litter decomposition of leguminous and non legume functional groups was carried out, through "litterbag" bags to verify the K index, such as collection of green leaves (Mar/2020) of seven species for analysis of abundance of 13C and 15N. In the study, it was observed that the functional group of fixing legumes and non-fixing legumes had better survival compared to the non legumes group, in which most of the dead individuals were from the non-legumes group, with a diameter class between 5-20 cm. Legumes had a greater increase compared to non-legumes, however, it was observed that the performance of the functional groups fits with the facultative theory of biological nitrogen fixation (BNF) in SDTF. Legumes have higher concentrations of C in the leaves and lower abundance of 13C, which suggests better resistance to drought and more efficient use of water in relation to the non-legumes group. Although 15N abundance and N concentration were higher in legumes, there was no significant difference. Legumes had great representation in the contribution of litter and nutrients. Legumes provide 11%, 48% and 25% more N, P and C, respectively, than non-legumes and have a higher K index, which suggests that they have chemical characteristics that make their decomposition difficult. Therefore, further studies are suggested to evaluate the functional traits of species in the face of predicted climate changes to better understand the dynamics of SDTF