Field incubations with 18O-H2O at the Marcell Experimental Forest, Minnesota, USA from the Spruce and Peatland Responses Under Climatic and Environmental Change Experiments (SPRUCE). Peat was collected from just below the live sphagnum and incubated in the treatment enclosures that are warmed +0, +2.25, +4.5, +6.75, +9 degrees C above ambient temperature, half the enclosures receive elevated CO2 treatments 500ppm above ambient CO2