Hydrology of a Water-Limited Forest under Climate Change Scenarios: The Case of the Caatinga Biome, Brazil

Given the strong interactions between climate and vegetation, climate change effects on natural and agricultural ecosystems are common objects of research. Reduced water availability is predicted to take place across large regions of the globe, including Northeastern Brazil. The Caatinga, a complex tropical water-limited ecosystem and the only exclusively Brazilian biome, prevails as the main natural forest of this region. The aim of this study was to examine the soil-water balance for this biome under a climate-warming scenario and with reduced rainfall. Climate change projections were assessed from regional circulation models earlier applied to the Brazilian territory. A statistical climate data generator was used to compose a synthetic weather dataset, which was later integrated into a hydrological model. Compared to simulations with current climate for the same site, under the scenario with climate change, transpiration was enhanced by 36%, and soil-water evaporation and interception were reduced by 16% and 34%, respectively. The greatest change in soil-water components was observed for deep drainage, accounting only for 2% of the annual rainfall. Soil-plant-atmosphere fluxes seem to be controlled by the top layer (0.0-0.2 m), which provides 80% of the total transpiration, suggesting that the Caatinga forest may become completely soil-water pulse dominated under scenarios of reduced water availability.