Aims 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...Aims 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.Methods 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.Important Findings 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.展开更多
Camivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up con- trol in ecosystems throughout the world, yet, little is known about how fire affects short-term carni...Camivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up con- trol in ecosystems throughout the world, yet, little is known about how fire affects short-term carnivore distributions across the landscape. Through the use of a long-term data set we investigated the distribution of lions, during the daytime, in relation to burned areas in Serengeti National Park, Tanzania. We found that lions avoid burned areas despite the fact that herbivores, their prey, are attracted to burned areas. Prey attraction, however, likely results from the reduction in cover caused by burning, that may thereby decrease lion hunting success. Lions also do not preferentially utilize the edges of burned areas over unburned areas de- spite the possibility that edges would combine the benefit of cover with proximity to abundant prey. Despite the fact that lions avoid burned areas, lion territory size and reproductive success were not affected by the proportion of the territory burned each year. Therefore, burning does not seem to reduce lion fitness perhaps because of the heterogeneity of burned areas across the landscape or because it is possible that when hunting at night lions visit burned areas despite their daytime avoidance of these ar- eas .展开更多
基金This research was partially funded by the Tufts Institute of the Environment and the Department of Biology at Tufts University.
文摘Aims 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.Methods 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.Important Findings 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.
基金We thank the Tanzania Wildlife Re- search Institute, Tanzania National Parks and Tanzania Com- mission for Science and Technology for permission to conduct research in the Serengeti. This work was supported by Na-tional Science Foundation grants DEB 0308486 to C.E and M.R., 9903416 and 0343960 to C.P., and 0543398, and 0842230 to M.R.
文摘Camivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up con- trol in ecosystems throughout the world, yet, little is known about how fire affects short-term carnivore distributions across the landscape. Through the use of a long-term data set we investigated the distribution of lions, during the daytime, in relation to burned areas in Serengeti National Park, Tanzania. We found that lions avoid burned areas despite the fact that herbivores, their prey, are attracted to burned areas. Prey attraction, however, likely results from the reduction in cover caused by burning, that may thereby decrease lion hunting success. Lions also do not preferentially utilize the edges of burned areas over unburned areas de- spite the possibility that edges would combine the benefit of cover with proximity to abundant prey. Despite the fact that lions avoid burned areas, lion territory size and reproductive success were not affected by the proportion of the territory burned each year. Therefore, burning does not seem to reduce lion fitness perhaps because of the heterogeneity of burned areas across the landscape or because it is possible that when hunting at night lions visit burned areas despite their daytime avoidance of these ar- eas .
