Peatlands cover only 3% of Earth’s land surface but contain about 20% of the global soil carbon pool. Peat deposits originated from higher plants and moss-generated litter. Because of cold, oxygen-poor conditions, the carbon contained in northern peatlands has accumulated for thousands of years. Under current warming trends and consistent with climate projections, such accumulations of carbon may be vulnerable to further decomposition or mineralization. If global temperatures warm as projected at higher latitudes, these peatlands could release large amounts of greenhouse gases such as carbon dioxide (CO2) and methane (CH4) that could accelerate global warming. The ability to predict or simulate the fate of the stored carbon in response to environmental disruption remains hampered by a limited understanding of the controls of carbon turnover and the composition and functioning of peatland ecosystems.
To identify and quantify these critical environmental response mechanisms, the Terrestrial Ecosystem Science program within the Department of Energy’s (DOE) Office of Biological and Environmental Research is supporting a whole-ecosystem experiment in an ombrotrophic bog (i.e., a raised bog that receives all water and nutrients from direct precipitation) located in the Marcell Experimental Forest of northern Minnesota. The Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment project, led by Oak Ridge National Laboratory, enables the assessment of ecological responses across multiple spatial scales—including microbial communities, moss populations, various higher plant types, and some insect groups. The project is evaluating a wide range of increased temperatures and levels of elevated atmospheric CO2 concentrations. Direct and indirect effects of the experimental perturbations are being tracked and analyzed over a decade. This comprehensive suite of spruce-peatland process studies and observations is being linked to model development and application requirements for improving process representation, calibrating models, and evaluating model predictions for boreal ecosystems. SPRUCE is a cooperative joint venture by scientists from DOE national laboratories, the U.S. Department of Agriculture Forest Service, and universities.
The experiment’s overarching science questions cover ecosystem responses ranging from the microbe to landscape scale. They include:
- Will deep belowground warming in the future release 10,000 years of accumulated carbon from peatlands that store one-third of Earth’s terrestrial carbon? At what rate?
- Will these carbon releases be in the form of CO2 or CH4 with 30 times the warming potential?
- Are peatland ecosystems and organisms vulnerable to atmospheric and environmental change? What changes are likely?
- Will ecosystem services (e.g., regional water balance) be compromised or enhanced by atmospheric and climatic change?
Answers to these questions will provide insights not only for small-scale processes but also for landscape-relevant water, carbon, and energy fluxes for similar peatlands. Results will inform higher-order models of vegetation responses under various levels of climatic warming and associated end-of-century atmospheric change.