The effects of extreme floods on the biophysical heterogeneity of river landscapes

Studies of large infrequent disturbances, such as the Mount St Helens volcanic eruption, the 1988 Yellowstone National Park fires, and Hurricane Hugo, show that such events leave a heterogeneous imprint on a landscape, and that this imprint subsequently influences ecological response. But what imprint does a large infrequent flood disturbance leave on a river landscape, and how does the imprint influence river ecosystem response to disturbance? We used a landscape ecological framework to examine the associations between the imprint of an extreme flood and the response of woody riparian vegetation in the Sabie River (Kruger National Park, South Africa) landscape. We found that the flood left a heterogeneous imprint, consisting of remnant vegetated patches, remnant physical patches, and newly created physical patches. The structure and composition of riparian vegetation assemblages subsequently differed among these patches. Heterogeneity of the river landscape mosaic may result in multiple trajectories of ecological response to the flood, with important consequences for biodiversity conservation in Kruger National Park.