Influence of land use and climate on recent forest expansion: a case study in the Eurosiberian-Mediterranean limit of northwest Spain

1. In Mediterranean mountainous areas, forests have expanded in recent decades because traditional management practices have been abandoned or reduced. However, understanding the ecological mechanism behind landscape change is a complex undertaking as the effects of land use may be influenced (reinforced or constrained) by other factors such as climate. 2. We used orthorectified aerial photographs to monitor changes in forest distribution in a set of 20 head-water basins (located in the Cantabrian Mountains of northwest Spain, at the Eurosiberian-Mediterranean limit) during the second half of the 20th century (1956, 1974, 1983, 1990 and 2004). In particular, we evaluated the combined effects of both land use history (comparing natural vs. anthropic basins) and microclimate (comparing shaded vs. sunny aspects) for assessing gain/loss rates and spatial distribution shifts of forests. Finally, in the stated scenarios of land use history and microclimate, we applied Species Distribution Mod...