Until recently, it was generally held that in the Mediterranean Basin post-fire vegetation composition returned directly to the pre-fire state even after recurrent disturbances by fire. This high degree of vegetation resilience was explained by the adaptation of species to frequent historical fire occurrence. In the last few years, however, the idea of strong vegetation resilience was criticised as local observations provided evidence for changes in vegetation composition after fire events which possibly result in a rise of enhanced degradation. Knowledge on the specific success of different regeneration mechanisms and their interrelation with ecological factors is essential for the understanding of the high variability of vegetation in response to ongoing changes in land-use and climate. Thus, the focus of the present thesis was on the description of the natural process of secondary vegetation succession on post-fire sites in south-eastern Spain and on the study of underlying plant regeneration mechanisms including the impact of driving factors such as disturbance regime, soil and microclimate. The study was carried out in Murcia (south-eastern Spain) at different fire sites in thermo-Mediterranean and meso-Mediterranean climate zones. The regeneration processes usually followed direct succession. Regeneration mechanisms changed clearly between the different climatic areas and direction aspects showing higher success of sprouting species in the mountainous area and very successful regeneration of facultative sprouters close to the coast. Germination experiments were carried out for all abundant seeder species. Heat stimulated germination was found for several species of Cistaceae and Fabaceae, while no species showed enhanced germination after diverse treatments with smoke. The species with heat stimulated germination were hardly found in the soil seedbanks, and seed longevity studies showed low survival rates of the seeds in the soil. The impact of the fire for the germination success of such "fire seeders" is not necessary, as the species were equally distributed at sites which had suffered other types of disturbance. This work contributes to the knowledge of various important aspects of post-fire succession in south-eastern Spain including details on all abundant species. Although strong limitations for vegetation recovery could not be found, this study shows that climatic differences between the coast and the mountains and, at a microclimatic level, between contrasting aspects have a great influence on successional processes and on the specific success of species with different regeneration mechanisms. Moreover, such climatic changes, possibly paralleled by land abandonment, may alter the frequency of fire events which, in turn, influences the specific success of plant strategies. |