Resumo

Sugarcane is the major important crop system in Brazil and it have mostly been related to the worldwide demand for its sub-products, ethanol and sugar. In this context many approaches have been ascribed to the productivity, but in a sustainable point of view, the microbial communities dynamics come as one of the crucial points to acquire a better understand of the process involving soil development and sugarcane production. This context may suggest, two important question: "What are the processes that explain the species abundance distribution (SAD) in these agroecosystems?”. This question will rely on the future previsions of the mechanisms structuring microbial communities, species interactions, random chance or some other factors that could help to increase the sugarcane production. Traditionally, there are two important models that explain the SAD. The first one is the niche-based in the deterministic processes, where the microbial community composition is a result of an environmental filtering when related to some resource gradient. The second one is the neutral, high lighting the stochastic processes, where all the species are ecologically equivalent and its distribution is related to an immigration dynamics. Using molecular techniques, we surveyed the archaea community, by T-RFLP analyses. 119 samples were collected in areas with distinct soil managements, distributed along 11 different producer regions to test the species abundance distribution models. . A total of four niche models (pre-emption, broken stick, lognormal and Zipf-Mandlebrot) and one neutral model (Zero-Sum multinomial - ZSM), were evaluated using the Tetame 2.1 and R software, from the comparison of the Akaike information criterion (AIC). The results demonstrated that in general the ZSM model was more suitable, and an exception to three regions being suited to the Zipf-Mandlebrot and pre-emption model. This suggests that the archaeal community is determined by the Neutral and Stochastic model, and the effects of distance, dispersion and environmental variations are responsible for its distribution in sugarcane crop systems.