Effects of vegetation succession and shrub clearing after land abandonment on the hydrological dynamics in the Central Spanish Pyrenees
Makki Khorchani, Estela Nadal‐Romero, Teodoro Lasanta Martínez, C. Tague
Abstract
Cropland abandonment is a global problem that has affected countries worldwide since the 19th century. Abandoned lands usually undergo a process of plant succession. This process has been widely shown to have implications for ecosystem services, including water provision. Mediterranean mountains are currently in the middle of these land transformations: for example, in the Pyrenees, 80% of the agricultural lands have been abandoned. During the last decades, the management of these areas have become a target of environmental policy makers to ensure the sustainability of ecosystem services. Targeting available resources for land management, however, requires estimates of the effectiveness of different treatment options. This study address this need by relating the management of the abandoned lands to plant succession and hydrological dynamics. We used the Regional Hydro-Ecological Simulation System (RHESSys) to predict the changes to land cover and hydrological dynamics following land abandonment in the Estarrún watershed in the Central Spanish Pyrenees. Projections from passive management allowing vegetation succession, and active management via shrub clearing were defined and their effects on annual streamflow (STR) and annual evapotranspiration (ET) are compared. Results show a high increase in forest cover due to the conversion of all the currently existing shrubs to forest during the upcoming three decades. This conversion to forest cover, would decrease STR by 19%, increase ET by 34%, and reduce the target area for shrub clearing by 72% within 30 years of plant succession. However, shrub clearing would similarly increase STR and decrease ET by 6%, if 7.5% of the study area is cleared. For both STR and ET changes decline rapidly if the management is delayed and the vegetation succession process continues. This study confirms the need to take into account succession following land abandonment in designing land management strategies to preserve water resources in Mediterranean mountain areas.