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United States Department of Agriculture

Agricultural Research Service

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The Prairie Heating and Carbon Dioxide Enrichment (PHACE) experiment was created in 2006 to learn how future environmental conditions will influence mixed-grass prairie. Mixed-grass prairie is the largest remaining grassland ecosystem in North America, and is integral to both agricultural productivity and conservation of biological diversity in the western United States.

PHACE Sampling

Click here for a video describing the experiment and early results.


Blumenthal, D.M., J.A. Kray, W. Ortmans, L.H. Ziska, E. Pendall. Cheatgrass is favored by warming but not CO2 enrichment in a semi-arid grassland.  Global Change Biology, doi: 10.1111/gcb.13278

Zelikova T.J., D.M .Blumenthal, D.G. Williams, L. Souza, D.R. LeCain, J.A. Morgan, E. Pendall. 2014. Long-term exposure to elevated CO2 enhances community stability by suppressing dominant plant species in a mixed-grass prairie. Proceedings of the National Academy of Sciences 111:15456-15461.

Reeves, J. L., D. M. Blumenthal, J. A. Kray, J. D. Derner. 2015. Increased seed consumption by biological control weevil tempers positive CO2 effect on invasive plant (Centaurea diffusa) fitness. Biological Control 84:36-43

LeCain D, D. Smith, J. Morgan, B.A. Kimball, E. Pendall, F. Miglietta. 2015. Microclimatic Performance of a Free-Air Warming and CO2 Enrichment Experiment in Windy Wyoming, USA. PLoS ONE 10(2): e0116834. doi:10.1371/journal.pone.0116834

Click here for a complete list of publications.


Identifying plants

Our objective is to predict the consequences of global change for plant and microbial communities and ecosystem processes. Responses of particular interest include plant metabolism, production, quality, diversity and community composition (invasive species, functional groups); microbial community composition and function; greenhouse gas sequestration and emission; and cycling of water, nitrogen and phosphorus. Read more... 


The core PHACE experiment includes five replications of the following treatments: (1) control (ambient conditions), (2) elevated CO2, (3) warming, and (4) elevated CO2 plus warming. Elevated CO2 treatments use free air CO2 enrichment technology to increase atmospheric CO2 to 600 ppm. Warming treatments use ceramic heaters to increase temperatures 1.5 C during the day and 3 C at night. Additional treatments use irrigation to separate water-mediated effects from direct effects of elevated CO2, and to learn how the seasonality of precipitation influences mixed-grass prairie. Read more about the experimental design...

Arial photo of PHACE


Installing frame

In 2005-2006, below-ground infrastructure for the PHACE plots was put in place, including hydrologic isolation of soils within plots, and installation of tubes for monitoring soil moisture and plant roots. The elevated CO2 and warming treatments began in spring 2006 and spring 2007, respectively. These treatments have been very effective in controlling environmental conditions. See Morgan et al. 2011, and associated supplementary material for details. See images of PHACE construction...


This project is a collaboration between the United States Department of Agriculture-Agricultural Research Service, the University of Wyoming, Colorado State University, the University of Sydney, Arizona State University, and the Institute for BioMeteorology (CNR, Italia). See a full list of researchers here.



Funding for this work is provided by the US Department of Agriculture-Agricultural Research Service Climate Change, Soils & Emissions Program, the US Department of Agriculture-Cooperative State Research, Education, and Extension Service Soil Processes Program (grant no. 2008-35107-18655), the US Department of Energy's Office of Science (Biological and Environmental Research) through the Western Regional Center of the National Institute for Climatic Change Research at Northern Arizona University, and the National Science Foundation (DEB no. 1021559).


Dr. Dana Blumenthal
Telephone: 970-492-7122
Fax: 970-492-7160
Postal address: 1701 Centre Ave, Fort Collins, CO 80526


Last Modified: 2/3/2017
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