Spruce-Peatland Responses Under Climatic and Environmental Change (SPRUCE Experiment): An in Situ Warming by Carbon Dioxide Manipulation of a Forest Bog in Northern Minnesota.

Identification of critical environmental response functions for terrestrial organisms, communities, and ecosystems to rapidly changing climate conditions are needed to evaluate ecological consequences and feedbacks. Such research has the most ‘real-world’ relevance when conclusions are drawn from controlled manipulations operating in natural field settings. We are constructing an experimental platform to address climate change response mechanisms in a Picea/Larix/Sphagnum ombrotrophic bog ecosystem located in northern Minnesota. This ecosystem located at the southern extent of the spatially expansive boreal peatland forests is hypothesized to be especially vulnerable to climate change and to have important feedbacks on the atmosphere and climate. The replicated experiment will allow us to test mechanisms controlling vulnerability of organisms and ecosystem processes changes for multiple levels of warming (up to +9°C) combined with elevated CO₂ exposures (900 ppm). New methods for whole-ecosystem warming at plot scales of 12 diameter have been developed for this study. Through the execution of this experiment we plan to quantify thresholds for organism decline or mortality, limitations to regeneration, biogeochemical limitations to productivity, and changing greenhouse gas emissions to the atmosphere. The experiment will allow for the evaluation of responses across multiple spatial scales including: microbial communities, bryophyte populations, various higher plant types, and some faunal groups. Direct and indirect effects of these experimental perturbations will be tracked and analyzed over a decade for the development and refinement of models needed for full Earth system analyses.