Desertificação no semiárido brasileiro: o papel dos microrganismos no processo de recuperação de áreas degradadas

Abstract

Desertification is characterized by the degradation of arid, semi-arid and dry sub-humid lands, caused by climatic factors and anthropic activities. In Brazil desertification affects the semiarid and sub-humid regions of the Northeast, and in Ceará the municipality of Irauçuba is the most affected area. This study was carried out to get information about the influence of the desertification on structure and function of the bacterial community in the Irauçuba desertification nucleus, aiming to contribute to the development of biotechnological solutions for the recovery degraded soils. This study evaluated chemical and microbiological variables of soils collected from natural recovery areas, excluded from grazing since the year 2000, pasture areas, in advanced desertification process, and in native vegetation areas of Caatinga. Four indicators of soil quality (organic matter (MO), moisture, pH and number of bacterial colony forming units (CFU/g)), besides phosphate solubilization activity and siderophore production were analyzed. Data were subjected to analysis of variance and the media compared by Tukey test. OM, CFU/g and moisture were considered lower in the desertification areas, compared to those native and in recovery areas. pH was the only indicator that did not show significant differences between areas, although soils are responding differently to environmental stresses. Among 69 bacterial species analyzed, 8 were selected based on the high rates of phosphate solubilization and siderophores production. The most promising isolate was identified molecularly as Enterobacter sp., a Gram-negative bacterial species, known as plant growth promoting bacteria (BPCV). Bacterial isolates obtained in the current study are potential candidates to be used as inoculants to accelerate the recovery of degraded soils in desertification areas.