Evaluating resilience of tree communities in fragmented landscapes: linking functional response diversity with landscape connectivity

AimMultiple agents of change increasingly impact functioning of forest ecosystems, for which management plans often ignore how local disturbances and habitat fragmentation jointly operate on ecological resilience at different scales. We examined sensitivity of functional response diversity (FD) to variation in species diversity to predict ecological resilience to future disturbances across tree communities and evaluated the role of landscape connectivity in maintaining ecological resilience at the landscape scale. LocationCentre-du-Quebec, Quebec, Canada. MethodsWe inventoried private forests and calculated FD and community-weighted means to determine the extent to which forest-use intensity affects ecological resilience. Subsequently, we constructed a regional map of FD, from which a spatial network was extracted. To assess potential impacts of fragmentation in maintaining FD at the landscape scale, we examined how the functional connectivity of the landscape, measured by the probability of connectivity (PC), varied across a range of maximum seed dispersal distances. Lastly, we evaluated the importance of individual forest fragments in maintaining landscape FD by measuring the connectivity fractions of PC. ResultsAcross tree communities, ecological resilience was low as FD increased sharply with species diversity. Forests with high FD were dominated by species with trait values associated with greater resilience to future anthropogenic disturbances rather than to future climate change. FD was maintained across the landscape by forest fragments acting as intermediate stepping stones in the transfer of seeds. Main conclusionsWe employed a novel approach based on spatial networks to extend the functional diversity concept from the local to the landscape scale. Our results suggest that seed dispersal over sufficiently large distances can maintain ecological resilience in fragmented landscapes and buffer changes in local-scale FD. Otherwise, FD is maintained by local processes, meaning that ecological resilience of isolated forest fragments depends strongly on land use type and intensity.