Compartimentos de fósforo orgânico e comunidade microbiana em solos após a retirada da caatinga

Abstract

The Brazilian Caatinga biome should hold the attention of researchers on its preservation because of its singularity, but is constantly neglected, which made it be considered as one of the most endangered biomes due to both anthropic actions and climatic seasonality. In the last fifteen years the anthropic extractive actions and conversion of forest areas into agricultural areas have transformed about 40,000 km² of caatinga into desertified areas. The present study aimed to evaluate the impact of management systems and seasonal variation on the phosphorus fractions in the soil, activity and composition of microbial comunities in the caatinga soil. The study was carried out in an area of Caatinga, in the municipality of Serra Talhada - PE at the Buenos Aires farm. In the rainy season, on April, 2014 (PC1), dry period on October 2015 (PS) and rainy season on April 2016 (PC2), three soil samples were taken in a depth of 0-5 cm with five replicates. in areas with different historical and management: preserved area with native vegetation of the caatinga, three areas of succession covered by angico, ipê and capoeira and an area of agricultural cultivation with dry maize. The analysis consisted on fractioning the soil phosphorus and the phosphorus presente in the microbial biomass, quantify soil basal respiration with an incubation period of 64 days and analysis of the Phospholipid Profiles (FAMEs). The data referring to the evaluated variables were submitted to a descriptive analysis of central tendency measures (means), plus dispersion measures (standard deviation). The labile organic phosphorus (Pol) was sensitive to variations in soil moisture. Total inorganic phosphorus fractions were higher than the total organic phosphorus in all evaluated periods and the relative changes in total organic phosphorus were 22 to 34, 8 to 54 and 11 to 31%, respectively, at the PCI, PS and PCII, respectively. The P present in the soil microbial biomass presented variable values, reaching its maximum point of 32.2 mg kg in the area of Capoeira at the PS. Soil respiration was slightly sensitive to the type of management and seasonality, but other parameters such as FAMEs, showed to be influenced by the soil management and seasonality, soil microbial biomass was composed predominantly of bacteria, being affected by soil pH and humidity.