Print PageMany distribution models have been developed to predict species distribution shifts due to climate change, most of which are habitat models. One of the key questions concerning this kind of projections remains: will species be able to migrate fast enough to track their climate optimum? So far, no study has been able to tackle this question because at large scale (spatial and temporal), dispersal mechanisms have never been taken into account into such predictions. In this study we investigate how a process-based species distribution model and a new kind of phenomenological dispersal model, both of which have been parameterized using species specific modern ecological data, were able to reproduce the post-glacial recolonization of European beech from 12kyr BP to present. Our dispersal model is based on the Gibbs point pattern process and takes into account dispersal and post-dispersal processes (intraspecific competition, predation, parasitism and facilitation) within a single integrative function representing the spatial pattern of cohorts in the landscape. We focused our study on the European beech because its postglacial expansion is well documented by sedimentary (pollen and macrofossils) and genetic data. More specifically, we used our models to disentangle the effects of climate and dispersal in the response of Fagus sylvatica to climate change.
Results/Conclusions
Surprisingly, our results showed that the process-based species distribution model was able to reproduce correctly the North-eastern boundary of beech distribution all along the Holocene without taking account for dispersal processes. However, it largely overestimated the North-western distribution. Thus, it seems that beech distribution was at equilibrium with climate at the Eastern boundary but not at the Western boundary. Our results also highlighted the importance of some refugees, which had been neglected by paleobotanists in their former analyses due to a lack of data, in the recolonization dynamics of beech. While the progression of the North-eastern boundary of beech distribution was entirely controlled by climate, dispersal and refuges controlled the progression of the North-western boundary. According to our simulations, European beech migrated at a mean rate of 200 m/yr (SD: ± 100 m/yr) with some long distance dispersal events of 800 m/yr, which is in agreement with the different estimation of dispersal published in the literature for this species. According to these results, our models might provide for the first time an accurate prediction of European beech distribution shift for the next centuries.
