Temperature Influences on Peatland Decomposition: Early Results from the Spruce Experiment.

In autumn 2015 we deployed litterbags containing black spruce needles and roots, Labrador tea leaves and roots, two Sphagnum species, mixed bags (Sphagnum plus either black spruce needles or Labrador tea leaves) and cotton strips in the Spruce and Peatlands Under Climatic and Environmental Change (SPRUCE) experiment. SPRUCE is an ecosystem-scale warming (both air and soil) and CO₂ elevation experiment located in a peatland in northern Minnesota that has temperature treatments of 0, 2.25, 4.5, 6.75, and 9^oC above ambient conditions, with and without elevated carbon dioxide (+500 ppm). Litterbags were deployed in hummock and hollow landscape positions in triplicate in each of the 10 treatments. Here we present initial results from time points at installation, 0.5 and 1 year for mass loss and carbon, nitrogen and phosphorus. The early results indicate little influence of temperature (or carbon dioxide) or landscape position on litterbag mass loss, carbon or nutrients. Labrador tea leaves and spruce needles are decomposing at a higher rate than the Sphagnum species and in the mixed bags, Sphagnum is increasing the decomposition rates of Labrador tea leaves and spruce needles. We did see a temperature effect on cotton strip tensile strength with higher temperatures leading to less tensile strength (i.e. more decomposition). We are continuing to deploy cotton strips and will be collecting litterbags at year 2, 5, and 10 of the SPRUCE experiment.