Rainfall Mesocosm Experiment
Background & Objectives
Together with large ungulate grazers and periodic fires, climate is a key driver of ecosystem structure and function in grasslands worldwide (Knapp et al. 1998). Climatic variability is a hallmark of the North American Central Plains grasslands. Paleoclimatic records and historical accounts from early settlers document a long history of climatic extremes in the Central Plains (Miner 1986, Gates 1993, Graham 1999). These extremes continue into modern times, with severe droughts in the 1930s and 1950s, and excessive rainfall in the early 1950s and 1990s (Easterling et al. 2000).
Current climate models suggest that climatic extremes in
The objective of the research described here is to experimentally determine the impact of rainfall patterns on above- and belowground grassland net primary productivity (ANPP, BNPP), using tallgrass prairie as a model system. Altered rainfall patterns will accompany warming and elevated CO2, and together they will impact the future productivity and biodiversity of grassland ecosystems. Rainfall is one of the most strongly limiting resources in grasslands, governing both the productivity and geographic extent of this biome. Climate model predictions regarding future rainfall regimes in the Great Plains are considerably uncertain, with some models predicting wetter (larger, more frequent rainfall events), and others predicting dryer (smaller, less frequent rainfall) weather patterns during the 21st century (Giorgi et al. 1994, National Assessment Synthesis Team 2000).
The research plan is to examine the above- and belowground responses of
synthetic tallgrass prairie plant assemblages grown in microcosms subjected
to sixteen combinations of growing season rainfall quantity and rainfall
frequency. The treatments will include both decreases and increases in
variability from present rainfall patterns in eastern
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Regional climate change scenarios over the
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Cenozoic history of North American vegetation, north of
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settling the high plains of
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Climate change impacts on the