Topic of Research

by ABADIE Juliet


Doctoral dissertation project:

Forest ecological networks and floristic biodiversity: role of landscape connectivity and history

After centuries of deforestation in Europe, forest cover is increasing on the French national territory since the nineteenth century, most of all in the Mediterranean region. Thus, we define too types of forest according to their temporal continuity: ancient forests, which have been forested since several centuries (at least 150 years in France), and recent forests, developed on former differing land use during the last 150 years. Ancient and recent forests are characterised by differing soil physical-chemical properties and understory vegetation. Indeed, several forest specialist plant species have limited dispersal capacities and ecological legacies of past land use is strongly marked in forest habitats, thus leading to a limited colonisation of recent forests by those species. The effect of temporal continuity on forest plant species and soils have been thoroughly studied in temperate regions but very poorly in the Mediterranean area.

To answer these questions, the main objectives of this PhD thesis are to analyse the drivers of forest cover change and the effect of temporal continuity and past land uses on forest soils and vegetation in the Mediterranean region.

A first part consists in studying biophysical and socioeconomic drivers of land use (forest, pasture, arable land) and forest recovery spatial distribution and their change since 1860, from the comparison of an ancient land use maps of 1860, 1958 and 2010.

Based upon this first part, the second one aims at clarifying the ecological differences between forests of differing temporal continuity (ancient, recent or very recent forests) and past land uses (forest, pasture or crop): how are they distributed according to biophysical conditions (slope, substrate type, etc.) ; what are the effects of past land uses on soil physico-chemical properties and understory vegetation (species and their life-history traits or ecological preferences)? Is the Etat-Major map the best tool to evaluate the effects of past land use on current forests in a Mediterranean forests, characterised by a traditional agro-sylvo-pastoral system?

This work relies mainly on the territory of the Natural Regional Park of Luberon (PNRL) and especially on the use of past and present land use maps (this thesis would never have been possible without the digitization of the Map of Etat-Major in 2011 by the PNRL team), floristic and pedological data collected in the field in 2015 and gathered from existing databases (SILENE for plant species and BASECO, Baseflor, Pignatti and the French Mediterranean flora for plant traits).

Supervisor: Dr Thierry Tatoni, IMBE
Co-supervisor: Dr Laurent Bergès, IRSTEA

Thesis funded by the PACA Region and IRSTEA

IRSTEA - RECOVER

Juliet Abadie