Variação sazonal de estoques e fluxos de nutrientes em áreas sob caatinga e pastagem em solo da região semiárida.

Abstract

The caatinga biome has greater diversity than any biome in semiarid climate. However, much of this biome has been deforested, which caused reduction of soil fertility, which depends directly on the nutrient cycling of litterfall. The use of biological indicators sensitive to changes in land use are critical for understanding the decomposition rate of litter. This study aimed to quantify the production, stock and decomposition of litter in the area of caatinga trees and shrubs evaluate the microbiological following attributes: biological activity, microbial biomass and microbial community structure of soil during the dry season and wet season grazing areas in two and two areas in the semiarid caatinga Paraiba. The study was conducted at the experimental station of the Emepa in Soledade-PB for 12 months. Collectors were installed to monitor the deposition and stock litter from caatinga. To study the biological attributes of soil were collected in two areas of caatinga, scrub (CA) and arboreal (CF) and two grassland areas in two positions in relief, high pasture (PA) and low (PB). We quantified the levels of C, N and P litter, the emission of CO2 by the method of static closed chamber carbon (MBC) and nitrogen (NBM) of soil microbial biomass by fumigation extraction method and structure of the microbial community soil by analysis of microbial fatty acid profile by the method of quantification of ester linked fatty acid (ELFA). The largest litter production in the savanna occurred in the late rainy season and early dry season, while the higher amount of C and N of litter occurs in the rainy season. Ratios of C/N and C/P found for both deposition and for the stock of litter were very high. The average change of CO2 -C was generally higher in areas of scrub at all sampling times. The highest density of vegetation in the areas of caatinga, and lowest position in relief in the pastures positively influenced the carbon and nitrogen content of the soil microbial biomass microbial community was altered by land use and vegetation type and correlated with environmental variables, the highest concentrations of markers of bacteria and actinomycetes occurred in the Caatinga, while on grassland predominated arbuscular mycorrhizal fungi and fungi in the pastures.