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Title: Projected Ecosystem Impact of the Prairie Heating and CO2 Enrichment Experiment

item Morgan, Jack
item Del Grosso, Stephen - Steve

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2007
Publication Date: 5/1/2007
Citation: Parton, W.J., Morgan, J.A., Wang, G., Del Grosso, S.J. 2007. Projected Ecosystem Impact of the Prairie Heating and CO2 Enrichment Experiment. New Phytologist 174:823-834.

Interpretive Summary: The anthropogenic release of significant quantities of greenhouse gases into the atmosphere began in the Industrial Age, and continues today at increasingly higher rates. Global climate change, including world-wide warming, is predicted to result from increased concentrations of these gases in Earth’s atmosphere. Further, one of the important greenhouse gases, carbon dioxide (CO2) is known to have direct effects on photosynthesis and plant water relations, and may have already led to important ecosystem changes in rangelands over the past 100 years. A new field research experiment is underway in a native mixed-grass prairie in southeastern Wyoming to investigate the combined influence of rising CO2 and warmer temperatures on various ecological properties to determine how global climate change will impact the functioning of semi-arid rangelands of the western Great Plains. This report describes an initial computer simulation experiment that was undertaken to help interpret the results of the global change field experiment. The model results suggest that global climate change will affect rangelands primarily through its influence on the water and N cycles.

Technical Abstract: The High Plains Global Change Experiment( HPGCE) has been initiated at a site in southern Wyoming and set up to simulate the impact of soil warming, elevated atmospheric CO2 levels, and species shift on ecosystem dynamics for short grass steppe ecosystems. Ceramic heaters are used to warm the system, and mini-face technology is used to elevate atmospheric CO2 levels. The ecosystem dynamics will be evaluated by measuring plant production, soil carbon dynamics, and nutrient cycling variables, along with detailed soil water and temperature data. The Daycent ecosystem model was set up to simulate the impact of elevated CO2 levels at the northeastern Colorado open top chamber elevated CO2 experiment site (1996-2001), and was then used to simulate the projected ecosystem impact of the HPGCE experiments during the next 10 years. The model results for the elevated CO2 experiment show that soil water content, plant production, soil respiration, and nutrient mineralization will all be increased for the high CO2 treatment. The model results for the warming show that soil water content will decrease, while N mineralization, soil respiration, and plant production will increase for most years. The warming treatment reduces plant production, soil respiration, and N mineralization for 10% of the years when enhanced drying from the treatment has a negative impact on the ecosystem. Model results suggest that adding 25% extra precipitation with each event will reduce the negative impact of warming on soil drying, and will possibly better represent the projected impact of future warming since current warming experiments do not include the projected increase in atmospheric water vapor.