Intra-annual rainfall variability and grassland productivity: can the past predict the future?
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Precipitation quantity has been shown to influence grassland aboveground net primary productivity (ANPP) positively whereas experimental increases in of temporal variability in water availability commonly exhibit a negative relationship with ANPP. We evaluated long term ANPP datasets from the Konza Prairie Long Term Ecological Research (LTER) program (1984–1999) to determine if similar relationships could be identified based on patterns of natural variability (magnitude and timing) in precipitation. ANPP data were analyzed from annually burned sites in native mesic grassland and productivity was partitioned into graminoid (principally C4 grasses) and forb (C3 herbaceous) components. Although growing season precipitation amount was the best single predictor of total and grass ANPP (r 2=0.62), several measures of precipitation variability were also significantly and positively correlated with productivity, independent of precipitation amount. These included soil moisture variability, expressed as CV, for June (r 2=0.45) and the mean change in soil moisture between weekly sampling periods in June and August (%wv) (r 2=0.27 and 0.32). In contrast, no significant relationships were found between forb productivity and any of the precipitation variables (p>0.05). A multiple regression model combining precipitation amount and both measures of soil moisture variability substantially increased the fit with productivity (r 2=0.82). These results were not entirely consistent with those of short-term manipulative experiments in the same grassland, however, because soil moisture variability was often positively, not negatively related to ANPP. Differences in results between long and short term experiments may be due to low variability in the historic precipitation record compared to that imposed experimentally as experimental levels of variability exceeded the natural variability of this dataset by a factor of two. Thus, forecasts of ecosystem responses to climate change (i.e. increased climatic variability), based on data constrained by natural and recent historical rainfall patterns may be inadequate for assessing climate change scenarios if precipitation variability in the future is expected to exceed current levels.
Key wordsANPP Climate change Grassland Precipitation variability Soil moisture Tallgrass prairie
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We would like to thank the undergraduates who tirelessly harvest and sort aboveground biomass, and the LTER personnel of KPBS, specifically Rosemary Ramundo and Amanda Kuhl. The NSF LTER program at Konza Prairie and the Department of Biology, Colorado State University supported this research.
- Freeman C.C. (1998). The flora of Konza Prairie: a historical review and contemporary patterns. In: Knapp A.K., Briggs J.M., Hartnett D.C., Collins S.L. (eds), Grassland dynamics: long-term ecological research in tallgrass prairie. Oxford University Press, New York, pp. 69–80Google Scholar
- Groisman P.Y., Karl T.R., Easterling D.R., Knight R.W., Jamason P.F., Hennessy K.J., Suppiah R., Page C.M., Wibig J., Fortuniak K., Razuvaev V.N., Douglas A., Forland E., Zhai P.-M. (1999). Changes in the probability of heavy precipitation: important indicators of climatic change. Climate Change 42:243–283CrossRefGoogle Scholar
- Houghton J.T., Ding Y., Griggs D.J., Noguer M., van der Linden P.J., Dai X., Maskell K., Johnson C.A. (2001). Climate Change 2001: The scientific basis Contribution of working group 1 to the third assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge United KingdomGoogle Scholar
- Jobággy E.G., Sala O.E., Paruelo J.M. (2002). Patterns and controls of primary production in the Patagonian steppe: a remote sensing approach. Ecology 83:307–319Google Scholar
- Johnson I.R., Kinghorn B.P., Murphy S.R., Lodge G.M. and Meszaros S.A. 2002. Estimating soil physical parameters using simulation and differential evolution. Proceedings of the IASTED International Conference: Applied Simulation and Modeling. June 25–28, Crete, Greece, pp. 274–279Google Scholar
- Knapp A.K., Briggs J.M., Blair J.M., Turner C. (1998). Patterns and controls of aboveground net primary production in tallgrass prairie. In: Knapp A.K., Briggs J.M., Hartnett D.C., Collins S.L. (eds), Grassland dynamics: long-term ecological research in tallgrass prairie. Oxford University Press, New York, pp. 193–221Google Scholar
- Le Houérou H.N., Bingham R.L., Skerbek W. (1988). Relationship between the variability of primary production and the variability of annual precipitation in world arid lands. Journal of Arid Environments 15:1–18Google Scholar
- USGCRP 2003. The Fiscal Year 2003 US Global Change Research Program and Climate Change Research Initiative. http://www.usgcrp.gov/usgcrp/
- Weltzin J.F., Loik M.E., Schwinning S., Williams D.G., Fay P.A., Haddad B.M., Harte J., Huxman T.E., Knapp A.K., Lin G., Pockman W.T., Shaw M.R., Small E.E., Smith M.D., Smith S.D., Tissue D.T., Zak J.C. (2003). Assessing the response of terrestrial ecosystems to potential changes in precipitation. BioScience 53:941–952CrossRefGoogle Scholar