Ecological diversity and resilience of Mediterranean vegetation to disturbance

Abstract

SummaryIn the Mediterranean region, plant communities are highly diverse with high total and local species richness, and a high spatial heterogeneity. They are also highly resilient to disturbance, which has been related to their evolutionary history of disturbance, and conceptually, although without formal proof, to their high ecological diversity. These ideas take on a new importance in the context of global change. In order to predict potential effects of future land use change, mechanisms underlying the resilience of ecosystems need to be understood. However, a review of the recent literature shows that confusion abounds as to the nature and measurement of resilience. In this paper we present a brief conceptual and methodological clarification and propose avenues for the analysis of mechanisms underlying the relationships between diversity and resilience, using Mediterranean ecosystems as an example.In Mediterranean ecosystems, rapid recovery from fire, soil disturbance and grazing has been attributed to two complementary causes. Firstly, disturbances often modify species relative abundances rather than composition, and recovery only involves the return to initial abundances. Secondly, life histories of dominant life forms in Mediterranean communities include efficient regeneration strategies that allow for recovery from dormant seeds or buds. In this paper, I use experimental results obtained in abandoned agricultural fields of southern France to investigate the mechanisms underlying the resilience of Mediterranean herbaceous communities to soil disturbance. These suggest that ecological diversity contributes to resilience in at least three ways.1.Post‐disturbance dynamics involve shifts in abundances of response groups to disturbance.2.Within response groups, processes of lottery competition account for the dynamic maintenance of numerous species.3.At the landscape scale, the fine grained distribution of communities at different successional stages allows for patch dynamics to operate with dispersal of species between patches.Further progress in the understanding of the relationships between ecological diversity and resilience of Mediterranean ecosystems can be achieved along two main avenues. Firstly, resilience of experimentally manipulated communities with differing levels of diversity needs to be assessed. Secondly, comparisons of those experiments across mediterranean‐climate regions with different evolutionary disturbance histories need to be coordinated.