Land cover effects on water balance partitioning in the Colombian Andes: improved water availability in early stages of natural vegetation recovery
Résumé
Vegetation actively affects different components of the water budget in multiple spatial and temporal scales. Changes in vegetation cover and structure—such as those resulting from land use—alter natural ecohydrological dynamics, leading to changes in natural hydrologic regimes. In tropical mountain ecosystems, such as the Colombian Andes, significant areas of native forests have been converted to agro-ecosystems that include pasturelands and croplands, to supply societal demands for other ecosystem services. Yet, services such as water provision and hydropower generation that depend on the regulation of hydrologic fluxes are also demanded from these ecosystems, potentially generating conflicting societal demands. In this study, we assess the effect of vegetation cover type and rainfall seasonality on the dynamics of hydrological partitioning—an indicator of hydrologic regulation—at three temporal scales, in a simulated gradient of human disturbance characterized by seven types of vegetation cover. Overall, vegetation cover effects on hydrologic partitioning are more pronounced in shorter, weekly to seasonal, timescales than in annual timescales. Natural vegetation cover types have a higher potential for maintaining water availability, as evidenced by lower variability of soil moisture storage and hydrological fluxes both within and between seasons. Notably, among all cover types, early stages of natural vegetation recovery appear to be more effective in maintaining higher levels of soil moisture while decreasing potential overland flow and other water losses, therefore more effectively contributing to deep drainage and potentially to groundwater recharge, which relate to hydrologic regulation and, ultimately, water availability. Collectively, our results provide insights for decision-making in land management, particualrly when provisioning and regulatory ecosystem services are demanded from these strategic ecosystems.