The role of wild boar and bryophytes in the network of forest interactions: implications for the coexistence of woody species
Abstract
Interest in the study of mixed forest stands is increasing both for managers and scientists because they are often more productive and less vulnerable to uncertainties than pure stands. However, the renewal and maintenance of mixed stands is a major challenge for managers because of the differences in autecology between tree species. To meet this challenge, managers need to understand the mechanisms and parameters that allow the coexistence of species. According to modern theory of species coexistence, coexistence is determined by (i) ‘equalizing mechanisms’ that reduce the relative difference in fitness between species, and (ii) ‘stabilizing mechanisms’ that increase the relative importance of intraspecific competition to interspecific competition. This thesis project will explore the coexistence of a pioneer species, Scots pine (Pinus sylvestris), and a post-pioneer species, sessile oak (Quercus petraea) in temperate lowland forest ecosystems. The objective is to study the different mechanisms that allow the coexistence of these two species by focusing on the unknown role of bryophytes and modulated by the disturbances of wild large ungulates and especially wild boar. In particular, the thesis aims at distinguishing between direct and indirect interactions within the undergrowth community (focusing on the triplet forest regeneration-bryophytes-wild boar) in order to evaluate the magnitude of the negative (competition) and positive (facilitation) interactions. The thesis will focus on two stages of forest renewal processes, germination of seeds and establishment of seedlings of our two target tree species. The thesis project benefits from the OPTMix long-term experimental site (http://optmix.irstea.fr), set up in the Orléans State Forest to study mixed sessile oak-Scots pine stands, with a control of wild large ungulates by selective fences.
