Understanding how biotic and abiotic factors combine to affect species interactions is an important challenge in ecology. Because the effects of biotic and abiotic factors on species interactions are often studied separately, it can be difficult to predict potential non-linear and indirect interactions among factors. We manipulated three key biotic and abiotic factors (temperature, food quality, predation) in field experiments in continental grassland using a plant – grasshopper – spider food chain. We examined whether temperature manipulations could alter grasshopper performance and predator-prey interactions, including the occurrence of trophic cascades.

Field enclosures containing one-, two-, and three- level food chains were set up at the Konza Prairie Biological Station in Manhattan, KS. Temperature was manipulated with plastic sheeting to increase temperatures or 50% shade cloth to decrease temperatures, which were compared with ambient controls. We measured vegetation biomass to identify trophic cascades and also measured grasshopper performance.

Our data show that temperature can fundamentally alter predator-prey interactions in our system, mainly by altering encounters between grasshoppers, which prefer warmer temperatures, and wolf spiders, which prefer cooler temperatures. Trophic cascades were only observed in shaded treatments, where reduced temperatures strengthened the effects of predators. This was observed as reduced survival and feeding by grasshoppers when spiders were present. In the warmed treatment, spiders had no effect on grasshopper survival or behavior, in part because spiders are less active at warmer temperatures. Our research indicates that temperature change has the potential to alter community structure and function by affecting predator-prey interactions.