Species-level Compensatory Responses Buffer Drought and Nitrogen Eutrophication Impacts on Plant-Arthropod Interactions in Species-Rich Grasslands
How drought and nitrogen deposition impact plant-arthropod dynamics is unclear due to interactions between water and nitrogen availability and plant quality for herbivores. Drought and eutrophication can increase plant quality (i.e., foliar nitrogen), the former doing so via physiological changes. Alternatively, drought may decrease plant quality by reducing ion transport and turgor. Re-occurrence of rainfall post-drought may result in the greatest plant quality by restoring ion transport and turgor. We employed a full factorial experiment in an old field and a tallgrass prairie to quantify interactions among drought, drought followed by a water pulse, and nitrogen addition on plants (biomass, cover, quality) and arthropods (herbivory, abundance, diversity). Community-level drought effects on plants were minor, explained by species-level compensation. Nitrogen addition increased biomass and foliar nitrogen, but not herbivory. Rather, arthropod-based responses were explained by grassland type. Our work demonstrates grassland plant-arthropod dynamics can be resistant to short-term drought and eutrophication.