Marcell Experimental Forest, USDA Forest Service peatland research past and present

Background/Question/Methods

The Marcell Experimental Forest (MEF) is an 1141 ha tract of land located in northern Minnesota. The MEF contains 6 experimental watersheds, each consisting of an upland portion and a peatland that is the source of a stream leaving the watershed. Climatic and hydrologic data have been collected continuously since 1960.  Studies in the 1960s were instrumental in bolstering our understanding of the physical and hydrological properties of peat. Subsequent studies beginning in the late 1960’s focused on the effect of forest management (e.g. peatland and upland harvesting) on hydrologic responses and element transport.   Studies beginning in the 1970s delved deeper into processes related to element cycling across a range of hydrologic conditions.  Carbon related studies began in earnest in the 1980s as the first peatland eddy covariance measurements were at MEF. In the 1990s a series of studies began to assess the influence of peatlands on watershed cycling of mercury.  More recent studies are measuring mercury cycles across a range of peatland and upland systems including the effects of elevated sulfate deposition and upland harvesting.  Our long history of peatland research led MEF to being selected as the site for the next ecosystem scale manipulation sponsored by the Department of Energy.  The Spruce and Peatlands Under Climatic and Environmental Change (SPRUCE) experiment aims to identify the critical response functions for organisms, communities, and ecosystems to rapidly changing climate conditions. We are constructing an experimental platform to address climate change responses in a bog ecosystem at MEF. This ecosystem is located at the southern extent of the boreal peatland forests and is hypothesized to be especially vulnerable to climate change and to have important feedbacks to the atmosphere. The experiment will allow us to test mechanisms ecosystem processes for multiple levels of warming (up to +9°C) combined with elevated CO₂exposures (900 ppm). New methods for whole-ecosystem warming at plot scales of 12-m diameter have been developed.  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. SPRUCE will allow for the evaluation of responses across multiple 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 over a decade for the development and refinement of models needed for full Earth system analyses.

Results/Conclusions

Review