Contrasting Effects of Precipitation Manipulations on Production in Two Sites within the Central Grassland Region, USA
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In grassland ecosystems, where soil water most frequently controls ecosystem processes, expected changes in precipitation and temperature may have dramatic effects on ecosystem dynamics. Previous observational studies have reported that aboveground net primary production (ANPP) in grasslands is very sensitive to changes in precipitation. Yet, we lack experimentally based evidence to support these observations. Further, most of the studies have focused solely on ANPP, neglecting belowground production (BNPP). This is an important gap in our knowledge, as BNPP represents 50% or more of total net primary production (NPP) in grasslands. Here, we present results from a 3-year water manipulation experiment (2008–2010) at two sites in the central grassland region of North America, USA. We were successful in changing the soil water content in our treatments, but these changes resulted in different, but significant responses in ANPP and BNPP at our two sites. At the shortgrass steppe, we found that neither NPP nor ANPP were sensitive to treatment precipitation, and although we found BNPP was sensitive to changes in treatment precipitation, the direction of the response varied between years. In contrast, ANPP was very sensitive to treatment precipitation on the mixed-grass prairie, whereas BNPP was insensitive. Based on our finding that two grassland ecosystems showed dramatically different above and belowground production responses to soil water manipulations, we cannot assume that predicted changes in climate will cause similar above- and belowground production responses. Second, our results demonstrated that sites within the same region may differ markedly in the sensitivity of ANPP to changes in growing season precipitation.
KeywordsANPP BNPP climate change ecosystem sensitivity soil water
This study was conducted in part at the Central Plains Experimental Range (CPER), which is administered by the USDA Agricultural Research Service (ARS) and was a Long Term Ecological Research site (SGS-LTER), funded by the National Science Foundation (Grant No. 1027319). This research was supported in part by the Utah Agricultural Experiment Station (to PBA), Utah State University, and approved as journal paper number 8356. The Nature Conservancy provided partial support for this work through the Nebraska Chapter’s J.E. Weaver Competitive Grants Program (to KMB). We thank J. A. Klein, A. K. Knapp, and two anonymous reviewers for their constructive comments and suggestions on the manuscript. The authors thank J.A. Leiker, M. Lindquist, and the Shortgrass Steppe Field Crew for their assistance designing and constructing the rainout shelters, conducting fieldwork, and applying water to the water addition treatment.
- CCSP. 2008. The effects of climate change on agriculture, land resources, water resources, and biodiversity. A report by the US Climate Change Science Program and the Subcommittee on Global Change Research. Washington, DC: US Environmental Protection Agency. Google Scholar
- Christensen JH, Hewitson B, Busuioc A et al. 2007. Regional climate projections. In: Solomon S, Qin D, Manning M et al., Eds. Climate Change 2007: The physical science basis. Contribution of working Group I to the fourth assessment report of the intergovernmental panel on climate change. Cambridge, UK/New York, NY, USA: Cambridge University Press.Google Scholar
- Hyder DN. 1975. Ecological responses of native plants and guidelines for management of shortgrass range. United States Department of Agriculture Technical Bulletin No. 1503.Google Scholar
- Lauenroth WK, Burke IC. 1995. Great plains, climate variability. In: Nierenberg WA, Ed. Encyclopedia of environmental biology. San Diego, CA: Academic Press. p 237–49.Google Scholar
- Lauenroth WK, Burke IC, Gutmann MP. 1999. The structure and function of ecosystems in the central North American grassland region. Gt Plains Res 9:223–59.Google Scholar
- USDA, NRCS. 2011. The PLANTS Database (http://plants.usda.gov). National Plant Data Team, Greensboro, NC 27401-4901 USA.
- Weaver JE. 1954. North American Prairie. Lincoln, NE, USA: Johnsen Publishing Company.Google Scholar
- Weltzin JF, Loik ME, Schwinning S, Williams DG, Fay PA, Haddad BM, Harte J, Huxman TE, Knapp AK, Lin G, Pockman WT, Shaw MR, Small EE, Smith MD, Smith SD, Tissue DT, Zak JC. 2003. Assessing the response of terrestrial ecosystems to potential changes in precipitation. Bioscience 53:941–52.CrossRefGoogle Scholar
- White RP, Murray S, Rohweder M, Prince SD, Thompson KMJ. 2000. Grassland ecosystems. Washington, DC: World Resources Institute.Google Scholar