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Description
Ecosystem restoration is a critical component of land management, countering the loss of native biodiversity. Restoration efforts are enhanced by reintroducing naturally occurring ecosystem processes, including disturbances that may impact species characteristics such as niche position or niche size. In North American tallgrass prairie, restoration efforts include the implementation of two historically important disturbances: reintroduction of the large mammalian grazer, the American bison, and fire. Both bison and prescribed fires affect grassland plant species diversity and habitat complexity, which potentially influence the dietary behavior of organisms such as insect communities. Using carbon and nitrogen stable isotopes, I characterize the abundance and variation in dietary behavior of six ground beetle species (Coleoptera: Carabidae) in response to fire and grazing disturbances in restored grasslands. Ground beetle activity density (an index of abundance) was not impacted by management disturbances for most species. Although mean trophic position was mostly unaffected by disturbances, five of six species exhibited increases in their isotopic niche area and trophic niche breadth, indicating a switch to a more generalist diet that incorporated a wider range of food items. Changes in beetle isotopic niches may be due to increased vegetation patchiness and heterogeneity that results from bison reintroduction and prescribed burns. Beetle traits such as flight ability and environmental preferences might mediate response to these disturbances and resulting heterogeneity. Combining prescribed fire and grazing, which increase plant diversity and vegetation structure, can help beetle communities establish over time and support the ecological functions to which these insects contribute.
