Palaeoecological insights into the long-term dynamics of forest ecosystems of south-western Europe: implications for current and future conservation and management
Disturbance regimes have long affected (sub-)Mediterranean ecosystems, largely shaping their current composition and structure. Fire plays a prominent role in the Mediterranean Basin, where it has usually triggered significant ecosystem changes. We currently know that human activities have altered Mediterranean fire regimes for millennia. However, our knowledge about the magnitude of these changes and their effects on the long-term dynamics of Mediterranean forest communities is far from complete at present. Land-use history, mostly comprising livestock raising and arable farming, has also been a significant landscape disturbance and has largely modified natural fire regimes. In this communication I present several case studies where land-use and the changes that it has directly or indirectly induced in fire regimes contribute to understand present landscapes and guide current and future nature management. (1) First, we studied fire regime changes associated to the introduction and establishment of Castanea sativa cultivation in the southern Swiss Alps. Then, we assessed the importance of the use of fire as a management tool as well as the consequences of recent and ongoing land-use abandonment on this valuable cultural landscape. (2) Later, we focused on the fire ecology of the once dominant and widespread but currently extinct Pinus nigra forests of the Northern Iberian Plateau. We showed how land-use intensification and the changes it induced on the natural fire regime caused the demise of these pine forests in the Middle Ages. (3) Finally, we have investigated the effects of disturbance regimes (fire, grazing) and land-use history on the vegetation dynamics of two National Parks of central Spain, Sierra de Guadarrama and Cabañeros. Here we have found that current densities of wild and/or domestic ungulates are unprecedented in the context of the last millennia and population control is consequently needed to guarantee forest regeneration.