Impacts of trail running and mountain biking: Resilience of a Mediterranean mountain ecosystem.

Rising outdoor activities have created major challenges for managing protected natural areas due to uncertain ecological effects. This study analyzes the impacts of two expanding sports, trail running and mountain biking, on flat and sloped terrains in a Mediterranean mountain setting in the Sierra de Guadarrama National Park, where transects were subjected to different use intensities. Early short-term impacts and subsequent recovery were monitored over a year using biotic and abiotic indicators: soil compaction, vegetation (total cover, Simpson's diversity index, and composition), bacterial colony-forming units, and edaphic microfauna. Results show that soil compaction and vegetation cover are the most affected among the variables analyzed, with significant alterations when applying a high number of passes on foot or by bicycle, but without significant differences between the two sports. Vegetation recovered faster than soil compaction, and Mediterranean seasonality strongly modulates impacts. Management measures are proposed to balance recreation and conservation.