Natural revegetation and afforestation in abandoned cropland areas: Hydrological trends and changes in Mediterranean mountains

Abstract

AbstractWater resources availability is one of the main concerns for policy makers around the world in present and future management plans. In the Mediterranean basin, this concern is increased given the extreme variability in climate and the intrinsic aridity conditions. Water resources in the Mediterranean region depend mainly on surface and subsurface supply from mountain areas. Because evapotranspiration comprises a substantial portion of the water budget, recent land cover changes due to cropland abandonment may change transpiration (TRANS) and water supply. Therefore, land management plans must account for these potential hydrologic changes to guarantee water availability in the upcoming decades. Short‐term changes to water yield have been shown to follow afforestation or natural revegetation, the main management strategies in abandoned cropland areas. Studies comparing long‐term trends of these management practices, however, are scarce due to the lack of long‐term hydrological data. In this study, we use the regional hydro‐ecological simulation system (RHESSys), to analyse long‐term changes and annual and seasonal trends in streamflow (STR) and transpiration following management of abandoned cropland areas. Annual mean values show significant differences between the three management scenarios for both streamflow and transpiration, while differences between climate scenarios are not significant. The Mann Kendall trend analysis shows significant changes to water yield compared to the situation before management. Depending on the total afforested area, afforestation could significantly decrease annual streamflow between 2.3%·decade−1 and 5.9%·decade−1 and increase annual transpiration between 1.1%·decade−1 and 3.5%·decade−1. These trends are attributed to changes during the first 30 years after management, while during the fourth and fifth decade, changes to water yield tend to stabilize or decrease. These results are substantial to optimize land management plans, ensuring sustainable hydrological and ecological ecosystem services.