Climate change effects on above- and below-ground interactions in a dryland ecosystem

Individual species respond to climate change by altering their abundance, distribution and phenology. Less is known, however, about how climate change affects multitrophic interactions, and its consequences for food-web dynamics. Here, we investigate the effect of future changes in rainfall patterns on detritivore-plant-herbivore interactions in a semiarid region in southern Spain by experimentally manipulating rainfall intensity and frequency during late spring-early summer. Our results show that rain intensity changes the effect of below-ground detritivores on both plant traits and above-ground herbivore abundance. Enhanced rain altered the interaction between detritivores and plants affecting flower and fruit production, and also had a direct effect on fruit and seed set. Despite this finding, there was no net effect on plant reproductive output. This finding supports the idea that plants will be less affected by climatic changes than by other trophic levels. Enhanced rain also affected the interaction between detritivores and free-living herbivores. The effect, however, was apparent only for generalist and not for specialist herbivores, demonstrating a differential response to climate change within the same trophic level. The complex responses found in this study suggest that future climate change will affect trophic levels and their interactions differentially, making extrapolation from individual species' responses and from one ecosystem to another very difficult.