Sucessão primária em bancos de sedimentos no rio Pandeiros-MG

Abstract

Ecological succession in previously unoccupied areas has been a central theme throughout the history of ecology. Such succession happens, among other situations, in new landforms resulting from fluvial processes, when they are colonized by plants, most of which are pioneers in successional processes. The objectives of this work were to understand how primary succession occurs in the sediment banks located on the banks of the Pandeiros River, to investigate the patterns of diversity and richness of communities in the sediment banks during each seasonal cycle and to analyze how environmental variations (distance to the d 'water, unevenness in relation to the river and canopy opening) influence the plant composition. For this purpose, in the 10 sediment banks selected for the study, we estimated the vegetation cover of individuals in continuous permanent plots of 1m², distributed in 5 transects per sediment bank. The environmental variables were obtained with the aid of measuring tapes and a clinometer. For the evaluation of changes in plant communities influenced by the seasonal cycle, we calculated the absolute and relative frequencies for each species, as well as elaborated extrapolation curves to compare each sediment bank in periods of drought and rain. We calculated diversity indices, Shannon and Simpson and Pielou Equability to analyze the species richness of the areas. We also produced redundancy analyzes (RDA) and built generalized linear models to analyze how environmental and response variables are related, and indirectly how they could affect species distribution. Also, in order to understand the organization of the plant community in these banks, we performed an NMDS. Intending to understand how the distance and the increase in the slope of the plots in relation to the river affect the species richness in the plots, we produced linear regressions. In total, 3039 individuals were sampled, with 919 recorded in the dry season and 2120 in the flood season. These individuals belonged to 97 species of 61 genera distributed in 30 families (Table 2). The Cyperaceae family had the highest number of sampled species (18 species), followed by Poaceae (15 species) and Fabaceae (13 species). In general, richness was higher during the flood period records. Banks 1 (H'=3.40) and 2 (H'=3.38) had the highest species diversity, according to the Shannon Index. The difference in level and the distance from the riverbed were the main variables that contributed to the characterization of the areas, especially regarding the vegetation cover in the dry season, when the environment was strongly influenced by the drought.