Summary

This PhD study aims at understanding how biotic, abiotic and stochastic factors interact to structure a heathland vegetation community managed under different traditional land-use practices for centuries prior to abandonment ca. 120 years ago.

This study is part of one of the longest spontaneous successional studies of heathland vegetation, where tree colonization and understory vegetation patterns were measured in successive vegetation surveys initiated in 1921. This data was complemented with an intensive survey of the current vegetation patterns and ecological factors.

I found that land-use legacies are still present in the soil and were important determinants of vegetation dynamics and community assembly. However, the effects of land-use legacies were mostly mediated by the understory vegetation and differed according to the functional groups. The distance to the edge, a proxy for the proximity to external seed sources, was an important factor affecting different components of the structure of the vegetation, demonstrating the importance of dispersal in the development of the community.

My results indicate that the effect of the biotic interactions varies along abiotic gradients (e.g. soil fertility) and interacts with the functional strategies of species to determine the establishment of colonizing species, species’ performances and diversity patterns in the local community. These results have implications for understanding the maintenance of biodiversity, the coexistence of species and the stability of heathland communities, which can be helpful when designing conservation and management actions.