Fatores edáficos determinando composição, riqueza e cobertura de plantas na savana de Roraima

Abstract

The Savanna of Roraima presents a mosaic of vegetation types with distinct structures and floristic composition that may be associated with different edaphic factors (fertility, texture and seasonal flooded soils). The objective of this study was to determine whether soil factors determine composition, richness and coverage of species and taxonomic groups (botany families) of plants in the savanna areas of Roraima. The study was conducted in 20 permanent plots located in the Campus Cauamé (UFRR) and the Campo Experimental Água Boa (Embrapa Roraima). A floristic inventory (composition and richness) was carried out and cover (%) of individuals and species was used as descriptor variable of habitats taking account three categories of flooded soils (well-, poor- and imperfectly drained). Multivariate techniques were used to determine patterns of occurrence and clustering. It was found 130 species classified into 34 plant families. The Cyperaceae, Poaceae and Fabaceae families were the most species richness in the plots. By linear regression it was found that the herbaceous layer has negative relation to seasonal flooding. The vegetation cover (%) of taxonomic groups in the flood category was dominated by herbaceous. However, in the plots with imperfectly drained soils (72.3%) and poorly drained (79.5%) was observed a higher average coverage of herbaceous related to well-drained soils (50.5%). The largest families coverage (%) in all categories were Poaceae and Cyperaceae. P. carinatum (Poaceae) was the most common kind of coverage present in different habitats for drainage. Thus, it is concluded that soil factors, particularly drainage, determine floristic and structural distinctions in the areas of savannah studied in Roraima.