The impact of large herbivores on woodland–grassland dynamics in fragmented landscapes: The role of spatial configuration and disturbance

Abstract

The vegetation structure of natural ecosystems is usually considered independent of their size and their location in the landscape. In this study, we examine the effect of size, spatial configuration and disturbances on the dynamic interactions of large herbivores and vegetation in a patchy environment using a metapopulation model. Simulations indicate that small, isolated or unfenced patches have low herbivore numbers and high tree cover whereas large, well-connected or fenced patches support high herbivore densities and are covered by grassland. Recovery of both herbivore numbers and forest cover in response to disturbance is slow (>100 years). These long recovery times are partly attributable to negative feedbacks between herbivore numbers and tree cover. When the population of large herbivores is disturbed, forest is able to expand, subsequently inhibiting herbivore population recovery. Likewise, forest disturbance allows herbivore population expansion, which inhibits forest recovery. Additionally, infrequent and limited disturbances like hunting and forest removal also affect the vegetation cover in patches of nature. Thus, our work indicates that the location and size of patches, together with disturbances, largely determine the structure of the vegetation in fragmented landscapes.