Dinâmica sazonal do carbono orgânico em solos com diferentes históricos de uso no semiárido de Pernambuco

Abstract

Drying-rewetting events promote changes in chemical and biological processes and soil fertility, as well as reduce or enhance the effects of management practices and soil use on organic matter. The present study analyzed the impacts of the conversion of native forests in agricultural areas on soil carbon and its relation with climatic variations in the semi-arid region of Pernambuco. Soil samples were collected in periods with different climatic conditions during two years of study in layers 0-5, 5-10 and 10-20 cm depth in seven areas with different vegetation cover and land use: Caatinga native forest, Angico forest, Ipe forest, capoeira grass and native Caatinga converted into areas of irrigated maize crop, dry maize crop and elephant grass. Carbon stocks (CST), total organic carbon (TOC), water-soluble carbon (WSC), microbial biomass carbon (MBC), microbial respiration (CO2), microbial quotient (qMic), and metabolic quotient (qCO2) were evaluated. All areas showed variations in soil organic carbon throughout the study. The highest stocks and concentrations of TOC were found in the preserved forest, as well as the best conditions for the development and accumulation of carbon by the microbial biomass. The conversion of caatinga to irrigated maize crop was promising, however, with the absence of management the accumulation of carbon decayed severely. Elephant grass showed higher concentrations of WSC, but it was the system that most emitted CO2 into the atmosphere. The variations found in all the fractions of the carbon accompany the climatic changes, which act regulating their entrances and exits in the soil and the action of the microorganisms in the mineralization of the organic matter.