COS 147-6 - The Gorongosa Savanna Ecology Experiment: A comprehensive study of the effects of fire and large mammals on savanna biodiversity

Abstract: Tropical savannas are dynamic ecosystems governed from the top-down by large mammal herbivores (LMH) and fire. These very distinct but interacting consumers influence soil quality and plant communities as well as each other. Nonetheless very few studies have analyzed fire and the presence of LMH in a well-replicated factorial design. This short-coming exists in spite of the importance of understanding fire for the management of protected areas and the accelerating decline of large mammal populations. In addition, fire and the presence of LMH influence savanna biodiversity broadly, but this is rarely quantified. This talk will describe a study addressing this research gap by manipulating the presence of LMH and early and late season fires in Gorongosa National Park, Mozambique, a mesic savanna recovering from conflict-related loss of large wildlife. Results from the first year of what will be a long-term study dedicated to (i) a holistic understanding savanna ecology and (ii) training Mozambican conservation biologists will be presented. Students in the Gorongosa Master’s in Conservation Biology Program tested hypotheses about the response of biodiversity to indirect and direct effects of fire and LMH.
We found grasses responded positively to hot burns and increased in the absence of LMH. Forbs, in contrast, were unaffected by fire but more abundant in plots open to LMH. Even after one year, shrub abundance and richness responded positively to the exclusion of LMH. Total phenolics increased in plant species protected from LMH. Faunal biodiversity was evaluated in response to fire, the presence of LMH, and multiple environmental variables. Crickets were the focal taxa representing insects and were highly seasonal as well as more abundant and species rich where shrubs were less abundant. Amphibians were more species rich in plots open to LMH and nearer to water; richness declined in plots experiencing early season burns. Reptiles were not directly affected by fire or LMH. Small mammal abundance and richness increased in the absence of LMH. LMH were observed feeding more often in plots experiencing late season burns. These data represent the most comprehensive analysis to date of the response of savannas to fire and LMH in a single, factorial experiment. The talk will also highlight a unique education program training a new generation of conservation biologists in Mozambique.