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The influence of precipitation amount vs. pattern on grassland net primary production.
Nippert, Jesse *,1, Knapp, Alan1, Smith, Melinda2, Briggs, John3, 1 Division of Biology, Manhattan, KS, USA2 National Center for Ecological Analysis and Synthesis, Santa Barbara, CA, USA3 Department of Plant Biology, Tempe, AZ, USA
ABSTRACT- Both rainfall amount and variability (seasonal timing and event size) have been shown to influence grassland aboveground net primary productivity (ANPP) in controlled field experiments. Using long-term data sets from the Konza Prairie LTER program, we analyzed patterns of natural variability in precipitation (event size, timing, event variability and length of intra-event dry periods) to assess their influence on ANPP in a tallgrass prairie ecosystem. Data were analyzed from an annually burned watershed comprising both upland and lowland plots and an experimentally irrigated site. Our results showed that seasonal precipitation amount was the best predictor of total and grass ANPP in three of the four long-term datasets analyzed (r2 ≥ 0.656). In the lowland burned watershed site, there were no significant correlations with any of the variables measured. Significant relationships were found between total and grass ANPP and several precipitation timing and event size variables, but these relationships were each weaker than for precipitation amount alone (r2 ≤ 0.664). No significant relationships were found between forb productivity and any of the precipitation variables measured (P > 0.05). These results imply that while precipitation variability can influence total and grass ANPP in tallgrass prairie under controlled conditions, variation in other abiotic and biotic factors in these long-term experiments makes it difficult to detect the impact of variability in precipitation patterns under natural conditions.
Key words: precipitation patterns, global change, tallgrass prairie, aboveground net primary productivity