Tracking nutrients in space and time: Interactions between grazing lawns and drought drive abundances of tallgrass prairie grasshoppers

Abstract

Abstract We contrast the response of arthropod abundance and composition to bison grazing lawns during a drought and non‐drought year, with an emphasis on acridid grasshoppers, an important grassland herbivore. Grazing lawns are grassland areas where regular grazing by mammalian herbivores creates patches of short‐statured, high nutrient vegetation. Grazing lawns are predictable microsites that modify microclimate, plant structure, community composition, and nutrient availability, with likely repercussions for arthropod communities. One year of our study occurred during an extreme drought. Drought mimics some of the effects of mammalian grazers: decreasing above‐ground plant biomass while increasing plant foliar percentage nitrogen. We sampled arthropods and nutrient availability on and nearby (“off”) 10 bison‐grazed grazing lawns in a tallgrass prairie in NE Kansas. Total grasshopper abundance was higher on grazing lawns and the magnitude of this difference increased in the wetter year of 2019 compared to 2018, when drought led to high grass foliar nitrogen concentrations on and off grazing lawns. Mixed‐feeding grasshopper abundances were consistently higher on grazing lawns while grass‐feeder and forb‐feeder abundances were higher on lawns only in 2019, the wetter year. In contrast, the abundance of other arthropods (e.g., Hemiptera, Hymenoptera, and Araneae) did not differ on and off lawns, but increased overall in 2019, relative to the drought of 2018. Understanding these local scale patterns of abundances and community composition improves predictability of arthropod responses to ongoing habitat change.

Keywords

• Acrididae
• bison
• grassland
• grazers
• herbivore
• Konza Prairie