Submitted to: Bioscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2008
Publication Date: 5/2/2008
Citation: Knapp, A., Beier, C., Briske, D., Classen, A.T., Luo, Y., Reichstein, M., Smith, M., Smith, S.D., Bell, J.E., Fay, P.A., Heisler, J.L., Leavitt, S.W., Sherry, R., Smith, B., Weng, E. 2008. Consequences of more extreme precipitation regimes for terrestrial ecosystems. Bioscience. 58:811-821. Interpretive Summary: Global warming driven by the accumulation of ‘greenhouse gases’ in Earth’s atmosphere is expected to cause intensification of the global hydrological cycle, which will likely be expressed as changes in total annual precipitation and through more extreme precipitation regimes characterized by larger rainfall events and more severe intervening drought periods. Such changes will have clear implications for the productivity, biological diversity, and capacity for carbon sequestration of U.S. grasslands and rangelands, upon which the national livestock industry depends. This paper presents a general model for predicting the consequences of more extreme precipitation patterns for both dry and wet terrestrial ecosystems including grasslands and rangelands. The model suggests that dry ecosystems may actually benefit from more extreme precipitation patterns because they result in more effective deep soil recharge, mesic systems may experience increased stress due to prolonged dry periods, and periodically inundated ecosystems may benefit from less prolonged periods of flooding. It is currently unknown how related global change drivers such as elevated atmospheric temperatures and CO2 concentrations will interact with these effects from extreme precipitation. Thus, multi-factor comparative experiments and systems modeling approaches are needed to more fully understand and forecast the potential ecological consequences of this underappreciated aspect of climate change.
Technical Abstract: Amplification of the hydrological cycle, as a consequence of global warming, will be manifest not only by alterations in total annual precipitation, but also through more extreme precipitation regimes characterized by fewer, but larger rainfall events and more severe intervening drought periods. Based on past studies and theory, we present a conceptual framework for predicting the consequences of this forecast change in intra-annual rainfall patterns on terrestrial ecosystems arrayed along broad precipitation gradients. More extreme rainfall regimes are predicted to increase the occurrence of periodic soil water stress in mesic ecosystems based on prolonged dry periods between rainfall events. In contrast, xeric ecosystems may exhibit the opposite response because an increased number of large precipitation events will result in greater soil water recharge, alleviating soil water stress for longer periods of time. This contingent effect on the overall soil water balance of ecosystems will likely cascade through all hierarchical levels of ecological processes and interact with related global change drivers such as elevated atmospheric temperatures and CO2 concentrations, requiring multi-factor comparative experiments and systems modeling approaches to more fully understand and forecast the potential ecological consequences.