Description of the research objectives

par Berangere Leys

The present plant species composition in the Mediterranean area is the result of the past fire regime. Since Neolithization (ca. 7000 years ago), fire was used to open up the Mediterranean landscape to create arable and grazing land. This treatment led to the hotspot of terrestrial biodiversity that we can observe today in this area. But high fire intensities reduce the rate of species regeneration and limit the resilience of the vegetation. Due to global warming, temperatures in the Mediterranean region are expected to be 25% warmer than the rest of the planet with up to 40% warming peak in summer. These heatwaves combined with increasing drought and land-use changes will likely result in more intense and more frequent fire events spreading to areas that used to be less affected. This fire activity increase poses a threat to the Mediterranean biodiversity due to changes in key habitats and species dynamics.

Understanding the historical relationship between the fire regime and the vegetation dynamics is crucial to assess the vulnerability of the vegetation to fire regime changes. Within this project, we aim to assess whether there is a general pattern of plant functional diversity in response to long-term variations of the fire regime in Mediterranean ecosystems to predict the future trajectory of the biodiversity facing climate change.

To achieve this, Holocene vegetation and the past fire regime are analyzed for five sites covering a great variation of the Mediterranean climate. While data already exists for three of them, sedimentary core samples are taken and charcoals and pollen are analyzed at the Etang des Aulnes and Etang du Pourra in southern France. In addition, the long-term dynamics between the fire regime and the vegetation dynamics are modelled using LandClim model which includes the impact of fire, herbivore load and human land use on vegetation dynamics at the landscape level. Then, the role of fire regime on plant trait distribution will be quantified both from modelled and reconstructed vegetation assemblages. With these results, public awareness will be increased and affective actions will be taken to maintain the Mediterranean plant biodiversity in times of changing climate conditions.