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 soilwater 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.

Core Ideas: A multi‐layer root water uptake model is developed based on matric flux potential. Soil hydraulic properties from two important ecological zones in Brazil are assessed. Water supplying capacity to plants is higher in semiarid than in humid zone soils. Reduction of root suction below −150 m does virtually not affect water availability. Predicting soil water availability to plants is important for agricultural and ecological models. Models that explicitly take into account root water uptake and transpiration reduction describe the ability of soil to supply water to plants based on soil hydraulic properties that depend on soil water content. The objective of this study was to further develop an existing single‐layer root water uptake model based on matric flux potential to allow for multi‐layer scenarios; and to illustrate its functionality using soil hydraulic properties from layered soils from two climate zones in Brazil: a semiarid zone and a humid zone. For each soil layer, the hydraulic properties were determined by inverse modeling of laboratory evaporation experiment data available for pressure heads between −165 and −1.5 m. The water supplying capacities of soils were evaluated using the newly developed multi‐layer root water uptake model. Soils from the semiarid zone were able to supply water to plants over a wider range of pressure heads. Soils from the humid zone showed slightly stronger hydraulic restrictions for supplying transpirable water. For the analyzed soils, only a negligible increase in available water results from decreasing the root water potential below −150 m. Therefore, based on this analysis, it is reasonable to expect plant adaptation to move toward an increase of root length density rather than to a decrease of minimum root water potential.

Brazil is one of the world’s largest producers of beef cattle and dairy products, which requires high forage yield to attend grass-fed animals’ demand. Among the grass species adopted in the forage production system in Brazil, the Brachiaria genus stands out. This genus comprises nearly 85% of all planted forage area. In general, forage production systems in Brazil are essentially rainfed, and thus susceptible to seasonal soil water stresses. Selecting the suitable Brachiaria cultivar for lands susceptible to periodic waterlogging and dry spells is crucial to enhance forage yield, and consequently, to reduce the environmental footprint of the livestock sector. In this research, we investigated the performance of three recent commercial Brachiaria brizantha cultivars (Piatã, BRS Paiaguás, and MG13 Braúna) extensively adopted in Brazil’s grazing systems subjected to different ranges of soil water potential. For three cutting periods, yield related-variables (e.g., plant height, leaf area, dry biomass, and water use efficiency) were measured. Our results point to the existence of a low drought-resistant trait among cultivars, indicating the need for releasing better-adapted cultivars to cope with reduced soil water availability. All cultivars achieved higher performance at soil water pressure head between −15 kPa and −25 kPa; and in general, the cultivar. Piatã showed slightly superior results to most of the treatments.