Abstract

Mountain forests affect spatial and temporal variability of snow processes through snow interception and by modifying the energy balance of snowpack. The high sensitivity of snow cover to seasonal temperatures in mid-latitude mountains is well known and is of particular interest with regard to a future warmer climate. The snowpack in the Pyrenees is expected to be the most impacted by climate change in the Mediterranean mountains, where future climate trends project rising temperatures and decreasing precipitation. This study analyzes how changes in temperature and precipitation can affect current forest-snow interactions in four forests, located near each other but under contrasting topographic settings, in the Spanish Pyrenees. This understanding will allow us to anticipate the future hydrological responses of Pyrenean forested mountain basins. The research was accomplished by performing a sensitivity analysis using simulations from the Cold Regions Hydrological Model (CRHM) and by comparing forest canopy sites (F) vs. openings (O). The CRHM platform focuses on the incorporation of physically based descriptions of snow-dominated regions hydrological processes. It was found that forest cover induced different snowpack sensibility to climatic change conditions in the studied forests. Delayed onset of snow accumulation (F: 13 days center dot degrees C- 1; O: 5 days center dot degrees C- 1) and reduced snowpack duration (F: 28 %center dot degrees C- 1; O: 23 %center dot degrees C- 1) under warmer temperatures were more intense in areas beneath the forest canopy compared to openings. A lower annual peak of snow water equivalent (SWE) (F: 81 mm center dot degrees C- 1; O: 129 mm center dot degrees C- 1), earlier meltout date (F: 8 days center dot degrees C- 1; O: 10 days center dot degrees C- 1) and slower melting rates (F: 0.4 mm center dot day- 1 center dot degrees C- 1; O: 0.5 mm center dot day- 1 center dot degrees C- 1) with increasing temperatures were more intense in forest openings. The forest-driven reduction in snowpack duration (40%) was significantly enhanced with warming (10% per degrees C). Lower precipitation (20% precipitation reduction) could increase the response of this forest effect to warming (32%), while higher precipitation (20% precipitation increment) could reduce it (-26%). There was relevant topographic variability in the forest-snow interactions in response to climate change among the study stands, despite their proximity.