Dynamics of grazing lawn formation in African savanna grasslands: an experimental test of the role of scale-dependent processes
Friday seminar by Joris Cromsigt.
Grazing lawns are characteristic for African savanna grasslands, standing out as intensely grazed patches of stoloniferous grazing-tolerant grass species. They from a great example of a positive consumer-resource feedback that can lead to very high densities of large herbivores. The mechanisms and conditions under which these feedbacks develop are, however, not well understood. Grazing lawn development has been associated with grazing and increased nutrient input by large migratory herds in the Serengeti. However, we argue that in systems without mass migrations other mechanisms play a role. Based on theory on self-organized patchiness we hypothesize that the consumer-resource feedbacks that lead to lawn development are scale-dependent. We experimentally tested these ideas in a natural savanna grassland in Hluhluwe-iMfolozi Game Reserve, South Africa. Our results provide an alternative mechanism for the development of grazing lawns in systems that lack mass migrating herds. Moreover, we add a new spatial dimension to the processes behind grazing lawn development, and hence help to understand how herbivores might create and maintain spatial heterogeneity in grassland systems.