The SPRUCE project is a multi-year interaction among scientists at ORNL and the U.S. Forest Service at the Marcell Experimental Forest. Our objective within this large collaborative project is to define the response surface of gross photosynthesis to warming, tissue water content, and ambient CO2 concentration for dominant Sphagnum species. These results will be incorporated into peatland modeling efforts (with Paul Hanson), and plant community composition change among woody and herbaceous vegetation (with Rich Norby).