Effects of past land use on Mediterranean forest understory vegetation

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; In the last twenty years, several studies have stressed the importance of including a historical approach in ecological studies. It helps understand structure and functioning of present ecosystems but also assess conservation objectives. In temperate regions, several studies showed that forest vascular plants differ according to forest temporal continuity. This difference is caused by a modification of forest habitats by past land use, especially soil physico-chemical properties, but is also conditioned by species colonisation potential. For instance, species more frequent in forests with a long temporal continuity, also known as ancient forest species, have life-history traits associated to poor dispersal abilities. However, the effect of past land use on the present flora has not yet been investigated in the Mediterranean. Our aim is thus to analyse floristic differences between ancient and recent forests and to identify life-history traits associated to those differences in the Natural Regional Park of Luberon. We also explore the effect of past land use on forest plant communities and soil physico-chemical properties. We hypothesised that: (1) species more frequent in ancient forests were typical forest species, more shade-tolerant and with poor dispersal ability (dispersal syndrome, soil seedbank); (2) ancient forest soils had less nutrients, more organic matter and are more superficial compared to recent forests; (3) those differences varied according to past land use (pastoral vs. cultural); (4) those differences are less pronounced than in temperate regions because former pasturelands were dominant in the Mediterranean. This study will enable us to better understand past land use effects on vegetation and soil dynamics in Mediterranean forests, and to compare our results with other biogeographical and sociological contexts.