Dynamics of mediterranean pine forests reforested after fires

Abstract

Forest fires are frequent under a Mediterranean climate and have shaped the landscape of the region but are currently altered by human action and climate change. Fires have historically conditioned the presence of pine forests, depending on severity and forest regeneration. Regeneration of Mediterranean pine forests is not always successful, and a transition to shrublands or stands of resprouting species can occur, even after reforestation. This study analyses vegetation changes in two Mediterranean pine forests after severe fires and both reforested. The pines had difficulty to regenerate, even despite post-fire reforestation. The problem is the difficulty of young seedlings to survive, possibly due to increased summer drought. Problems are greater in pine species at the limit of their ecological tolerance: Pinus pinea had a much better recovery success while P. sylvestris and P. nigra virtually disappeared. Pinus pinaster had intermediate results but recovery was generally poor. A transition has taken place in many burnt areas to scrubland or to thickets of the resprouting Quercus rotundifolia, although it is not possible to know whether they will evolve into forests or remain in a sub climatic state. Resprouting species may increase fire severity but facilitates post-fire colonisation. Post-fire recovery difficulties are closely linked to issues of natural regeneration. Fire could initiate the disappearance of pine forests, but even in the absence of fire they may disappear in the long-term due to the lack of regeneration. Action is needed to increase the resilience of these forests, ensuring natural regeneration, and incorporating resprouting species in the understorey.