The influence of fire frequency on the abundance of Maerua subcordata in the Serengeti National Park, Tanzania

Invasive species alter the composition and function of communities, threatening the conservation of important ecosystems worldwide. In savanna ecosystems, fire plays a key role by modifying biogeochemical cycles and shaping the composition and structure of vegetation communities. Although many studies have examined the long-term effects of fire frequency on grassland communities, few studies have examined the relationship between fire regime and woody species invasions. The Serengeti ecosystem is an ecologically and economically valuable natural resource in East Africa whose conservation is currently threatened by a variety of factors, including invasive species. We determined the abundance of Maerua subcordata, a noxious woody shrub, in three different regions of the Serengeti National Park, Tanzania. We then examined the influence of fire frequency, developed through the use of 7 years of Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, on M. subcordata abundance. In all regions, burned transects had significantly greater abundances of M. subcordata compared to unburned transects. Furthermore, the number of times each transect burned from 2000 to 2006 had a significant positive effect on the abundance of M. subcordata and the number of years since a transect last burned had a significant negative relationship with abundance. These results are particularly important as this species provides little forage value and is potentially toxic to wildlife and cattle. Additional studies are needed to determine the ecological consequences of increasing M. subcordata abundance, as the potential expansion of noxious shrubs into protected areas of important conservation status is of serious concern.