Scale influence in water resources management for heterogeneous oak-savanna distinctive microclimates.

Dehesas are savanna-type ecosystems subject to regular water deficits; they have a complex structure with multiple vegetation layers that differ in phenology, physiology, and function, and each one contributes differently to turbulent exchanges and the radiative transfer budget. The combined differential functioning and characteristics of the vegetation components affect water dynamics, resulting in high spatio-temporal variability that creates distinct intra-ecosystem microclimates. This structure influences ecological processes, such as plant growth, and plays an important role in Dehesa resilience, making the system an efficient convector of sensible heat and keeping the canopy surface temperature within the survival range. Dehesas are productive landscapes, and one of their multiple uses, extensive livestock farming, requires an environment that is comfortable for animals and produces sufficient biomass yields. Thus, microclimate regulation and stability are key to maintaining the ecosystem’s profitability. We need to better understand the interactions between vegetation structure and dynamics, and microclimate delineation and regulation, at scales relevant to both farming management and the dominant mesoscale hydrologic regime. 

We evaluated the water use patterns estimated by different modeling approaches (FAO56, ALEXI - DisAlexi with STARFM, and SEBS) with different spatial resolutions (5 km to 10 m) of the herbaceous stratum and other typical vegetation patches (scrubs, humid areas, creek shore), which shape the distinctive dehesa microclimates. From a farm management viewpoint, we demonstrated the need for sufficient spatial and temporal resolution when evaluating water consumption. Higher spatial-temporal scales were crucial to determining the pasture drying cycle and can benefit the assessment of the nutritional quality for livestock feeding. In humid or denser areas that provide essential ecosystem services (e.g. shelter, soils with increased water retention) transpiration rates were higher throughout the year and often underestimated when using coarse data. Over mixed patches (grass and trees with low coverage fraction) products with coarse resolution (1 km to 5 km) reflected well the water use pattern. From a hydrological viewpoint, the 30 m resolution ET product may be useful to identify and delineate areas with different water storage capacities and runoff processes within the basin. Nevertheless, coarse resolutions are enough for regional managing purposes.