TEMPORAL CHANGES OF VASCULAR PLANT DIVERSITY IN RESPONSE TO TREE DIEBACK IN A MEDITERRANEAN LOWLAND FOREST

Lowland forests underwent a century long history of deforestation and degradation that left only few remnants of this forest type, especially in the Mediterranean region. These remnants have high conservation value but are threatened by tree diebacks related to different causes. Here we focused on the area of Palo Laziale (oak floodplain forest) and on the effects of the tree dieback following the summer drought of 2003. In the framework of an ecological restoration project (LIFE PRIMED LIFE17 NAT/GR/000511), we collected data on plant communities' species composition both in 2019/2020 and compared these data to those collected in 1990, also accounting for life forms, chorotypes and Ellenberg Indicator Values. This analysis was conducted to assess whether there was any change in the species composition following the forest dieback. The total flora of the site increased from 462 to 490 species. Moreover, there has been a turnover of species with the loss of some grassland and halophytic species and the entrance of allochthonous/ruderal and freshwater habitat species. Despite this, the plant diversity remained unchanged in bioindication terms, demonstrating a certain resilience of the ecosystem plant species, confirming the floristic re-survey approach to identify declining processes and support ecosystem-based restoration actions elsewhere.