Impacto das alterações de usos do solo na diversidade funcional bacteriana

Abstract

Changes in land use result in a differentiation of organic matter input that influences the availability of the resource and, as a consequently, its biodiversity. Microorganisms are widely present in soil and are part of most biogeochemical cycles. Thus, variations in microbial diversity present as a biological indicator to understand the impact of these soil changes on the ecological functions of microorganisms and their ecosystem functions. Considering that changes in soil vegetation structure have consequences on the resources available to microorganisms and can alter their functional diversity, we investigated the abundance and diversity of functional bacterial groups in soils with different vegetation coverages. In this context, the work was developed with 28 soil samples from different areas of the Ecological Station of Aiuaba – Ceará and surrounding area, classified according to their vegetation and land use. The abundance and functional diversity of five functional groups (actinobacteria, cellulolytic bacteria, amylolytic bacteria, phosphate solubilizing bacteria and free-living diazotrophic bacteria) present in these samples and the soil chemical parameters were evaluated. Abundance was described by counting colonies on plates, following the methodology for each bacterial group and expressed as Log CFU g-1 and functional diversity was determined from the Shannon index. In addition, an ANOVA and comparisons of means by Pearson's correlation test were performed, then a Principal Component Analysis (PCA). The abundances of actinobacteria and diazotrophic bacteria were higher in a preserved area; and in conserved areas, the greatest abundances were of cellulolytic bacteria and amylolytic bacteria; the solubilizing bacteria were more abundant in the agricultural area. Regarding functional diversity, the highest value was found in the conserved area and the lowest in the agricultural area, which also showed lower values in nine of the fifteen chemical parameters analyzed. In contrast, the preserved area showed higher values in chemical parameters also in nine of the fifteen determined; moreover, the correlations were positive in most cases. The results, although they suggested the functional redundancy of the groups, presented the importance and influence of soil properties and plant community on the abundance and diversity of bacterial functional groups.