Precipitation extremes - such as droughts and deluges - have been demonstrated to be powerful determinants of ecological change, with the frequency and intensity of these extremes only expected to increase in the future. There is evidence that ecosystems may respond differentially to dry vs. wet extremes and that ecosystem responses may be dependent upon the degree of extremity with respect to the historical record. However, few studies to date have experimentally tested the relationship between historic climatic extremity and the degree of responses across ecological scales, and whether responses differ for dry vs. wet extremes. To test this, we experimentally exposed an intact grassland ecosystem to multiple levels of growing season precipitation extremity, both wet and dry.
We observed consistent asymmetry in ecological responses to precipitation extremity, such as in aboveground net primary production and soil CO2 flux, with thresholds observed in carbon fixation of the dominant grasses. Such asymmetry in ecological responses occurred within the context of significantly increased mobilization of soil ions associated with flooded conditions at the highest precipitation inputs, suggesting frequent soil oxygen depletion and an intensification of biogeochemical cycling. In total, our results demonstrate that differential sensitivities among ecological processes to dry vs. wet extremes precipitation extremes likely underlie asymmetrical responses observed at the ecosystem level.