R. Michael Miller, ANL contact (rmmiller@anl.gov) 

This project is a manipulative experiment using open-top chambers on the Oak Ridge National Environmental Research Park to investigate the interactive effects of CO2, temperature, and water on a constructed ecosystem with plants typical of an old-field system, including C3 and C4 grasses, forbs, and legumes (see OCCAM web site for a description of the experiment). Our hypotheses and research approach are built around four general predictions: (1) The response of an old-field community to elevated [CO₂] and increased air temperatures will be mediated by the availability of soil water; (2) community composition and production will be driven by interactions between the component taxa and their individual and combined responses; (3) ecosystem level responses will depend on the interactions between above- and belowground processes; (4) a mechanistic understanding will be necessary to explain the responses to temperature and the net ecosystem response to the multiple factor interactions and feedbacks. The experiment consists of 12 4-m diameter open-top chambers (whole plots) to be exposed to ambient or elevated [CO₂] combined with ambient or elevated temperature. Two levels of soil moisture are being maintained as split-plots within the chambers. Measures of response include above and belowground production, community composition, net ecosystem carbon exchange, nitrogen mineralization, and mycorrhizal growth and activity. This project is part of the DOE-BER Program for Ecosystem Research (PER), conducted within the US Global Change Research Program.

Links:

OCCAM web site: http://warming.ornl.gov/OCCAM.html
DOE-BER Program for Ecosystem Research: http://www.sc.doe.gov/ober/CCRD/per.html