Drought timing differentially affects above- and belowground productivity in a mesic grassland
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Climate models forecast an intensification of the global hydrological cycle with droughts becoming more frequent and severe, and shifting to times when they have been historically uncommon. Droughts, or prolonged periods of precipitation deficiency, are characteristic of most temperate grasslands, yet few experiments have explored how variation in the seasonal timing of drought may impact ecosystem function. We investigated the response of above- and belowground net primary production (ANPP & BNPP) to altered drought timing in a mesic grassland in NE Kansas. Moderate drought treatments (25% reduction from the mean growing season precipitation [GSP]) were imposed by erecting rainout shelters in late spring (LSP), early summer (ESM), and mid-summer (MSM, n = 10 plots/treatment). These treatments were compared to two controls (long-term average GSP [LTA] and ambient GSP [AMB]) and a wet treatment (+30% of the long-term average GSP [WET]). We found that LSP drought did not significantly reduce ANPP relative to control plots while the ESM and MSM drought did despite equivalent reductions in soil moisture. In contrast, the WET treatment did not affect ANPP. Neither the WET nor the drought treatments altered BNPP as compared to the controls. Our results suggest that forecasts of ecosystem responses to climate change will be improved if both the seasonal timing of alterations in precipitation as well as differential responses of above- and belowground productivity to drought are incorporated into models.
KeywordsGrasslands Drought timing Climate change Aboveground net primary production Belowground net primary production
We would like to thank the many people who have worked at Konza Prairie Biological Station over the years that have made comparison to the long-term record possible, as well at the National Climate Data Center for providing such accessible climate records online. The assistance from the Kansas State Soil Testing Lab was also invaluable. In addition, a large thanks goes out to all those individuals who, through their time and labor, made the present experiment a success: J. O’Malley, L. Baur, M. Johnson, J. Carroll, A. Czerwinski, S. Mackenzie, K. Dennison, M. Merrill, W. Mowll, A. Hoffman, J. Gray, B. Leinwetter, F. Chaves Rodriguez, P. O’Neal, and J. Larkin. Finally, additional thanks go to J. Hoeting for assistance in analyzing our results. Support was provided by the National Science Foundation Konza Long-Term Ecological Research program.
This study was supported in part by funding from the National Science Foundation (NSF) for the Konza Long-Term Ecological Research program and the NSF Macrosystems Biology Program’s support of the Extreme Drought in Grasslands Experiment (EDGE) project.
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Conflict of interest
The authors declare that they have no conflict of interest.
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