Legume Tree Dominance in Central Amazonian Floodplain Forests

Studying the patterns of dominance and species composition of legumes can contribute to more precise models for nutrient cycling, especially the N-cycle. Leguminosae is the most important family in Central Amazonian floodplain forests surrounding large rivers. The floodplains are classified as nutrient-poor (igapó) and nutrient-rich (várzea) ecosystems. In this study, we contrast patterns of dominance and composition of legume tree species between both floodplain ecosystems based on floristic data from 22 plots. We observed significant differences in species dominance and the absolute and relative density of individuals, which were significantly higher in igapó than in várzea. A significant floristic difference between várzea and igapó was found. Higher legume species dominance and absolute and relative legume tree density suggest that legumes are more prominent in igapó. Low nutrition contents in igapó water and alluvial substrates possibly act as an environmental filter favoring the dominance of well-adapted legume tree species, which markedly contributes to the difference in floristic composition between both ecosystems.