Interactions between Vegetation, Hydrology, and Litter Inputs on Decomposition and Soil CO2 Efflux of Tropical Forests in the Brazilian Pantanal

Climate change has the capacity to alter water availability and the litter production of tropical forests, which will alter rates of carbon (C) cycling and storage. We conducted a short-term field experiment in two hydrologically diverse forests in the Brazilian Pantanal to assess the initial response of litter decomposition and soil respiration (Rsoil) to variations in litter pool size. Total annual Rsoil and decomposition significantly declined with litter removal and increased with litter addition, but the rate of litter decomposition was highest for plots where litter was removed. Rsoil was positively related to soil organic matter content and the rate of litter decomposition, but not soil moisture or temperature, suggesting that the litter treatment effects on decomposition and Rsoil were due to changes in C availability and not litter effects on the soil environment (i.e., temperature and moisture). Rsoil was not significantly different between the forests studied here even though they had large differences in hydrology; however, litter decomposition was significantly higher in seasonally flooded forest, especially when augmented with litter. These results suggest that alterations in litter production from land use and/or climate change will alter short-term rates of decomposition and Rsoil for these and other floodplain forests of the Pantanal and Amazon Basin.