Interactions among functional groups in the cycling of, carbon, nitrogen and phosphorus in the rhizosphere of three successional species of tropical woody trees

During the natural revegetation process, which occurs after rain forest destruction, there are different types of successional groups of woody tree species (pioneer (PN), early secondary (ES), late secondary (LS) and climax). A study of interactions among these plant groups, and the functional groups of microorganisms, is fundamental in improving revegetation programs in south Brazil. The revegetation processes are related directly to the functional communities of microorganisms, because several stages of the nutrient cycle are mediated exclusively by microorganisms, and some of these microorganisms can participate in one or more biogeochemical cycles. The interactions between some successional groups of woody species inoculated with native arbuscular mycorrhizal (AM) fungi and the C, P and N cycling functional groups of microorganisms were assessed. The results showed that the AM fungi play an important role in regulating the cycling functional populations in the plant rhizosphere. The characteristics of the plant successional groups also influenced the functional microbial groups. Two populations of free-living N-fixing bacteria were evaluated. Inhibition occurred in the community that used glucose as a carbon source in the pioneer rhizosphere, whereas no differences were observed in the community of N-fixing bacteria that used malate as carbon source.