Dinâmica do carbono na interface solo-água no Pantanal matogrossense

Abstract

The dynamics of soil carbon and the contribution of edaphic microflora to soil carbon cycling were investigated at the terrestrial-aquatic interface during periods of flood and ebb of a hydrological cycle in the Pantanal wetland, in Brazil. Our hypothesis was that the decomposition of organic matter during the change from aquatic to terrestrial environments can result in the substitution of carbon from terrestrial soil carbon with carbon of aquatic origin. Further, we predicted the microbial activity in soil tends to be reduced in aquatic environments, thus contributing to a greater accumulation of soil carbon. Soils were sampled from three areas with different vegetation types in the northern Pantanal of Mato Grosso. We used the stable isotope methods to determine the sources of soil carbon during the two periods. This study evaluated soil physical and chemical properties, microbial biomass carbon (C-BM), carbon respiration (C-CO2), metabolic quotient and soil enzymatic activity. With the change to flood tide there was a decrease in acid phosphatase, urease, C-CO2 and C-BM. The carbon isotope ratio (δ 13C) showed a negative correlation with the logarithm of the concentration of carbon for the three areas sampled in two periods of the hydrological cycle studied. The sources of soil carbon along the phases of flood and ebb originated from both C3 plants and C4 plants. The dynamics of soil carbon during periods of inundation in the Pantanal have resulted in the accumulation of carbon. This increase is associated with reduced microbial activity in soil under anaerobic conditions generated by flooding, thus slowing the decomposition of soil organic matter, and allowing a greater accumulation of carbon in this compartment of the trophic network.