The Marcell Experimental Forest (MEF) in northern Minnesota, USA may be the longest running research and monitoring program on the hydrology of peatland catchments. The MEF sits astride a continental divide where the headwaters of the Mississippi, St. Lawrence, and Hudson Bay adjoin. When established in 1961, the MEF, with little topographic relief and large fractions of watersheds in peatlands, was distinct from the steep, mountainous catchments that typified other research catchments of the USDA Forest Service. This terrain and the presence of peatlands are representative of vast areas of the Northern Hemisphere, and the research program fills an important role in environmental monitoring and research in hydrology, ecology, biogeochemistry, and environmental change. During the 1960s, six research catchments were established and hydrological, meteorological, and water chemistry monitoring were initiated. Since then, the research and collaborations have proliferated to include new monitoring and ecosystem manipulations, with several paired-watershed studies, that allow the assessment of land management and environmental change effects on forests, water availability, and biogeochemical cycles. Research at the MEF remains vibrant, especially now that the site hosts a large-scale climate manipulation study (the SPRUCE Experiment). Herein, we present information on the site, contacts, long-term monitoring, experiments, and key findings.

Check out our video abstract: https://youtu.be/CGzFNU70yUg To date, the perspective of forest ecohydrologists has heavily focused on leaf-water interactions – leaving the ecohydrological roles of bark under-studied, oversimplified, or omitted from the forest water cycle. Of course, the lack of study, oversimplification, or omission of processes is not inherently problematic to advancing ecohydrological theory or operational practice. Thus, this perspective outlines the relevance of bark-water interactions to advancing ecohydrological theory and practice: (i) across scales (by briefly examining the geography of bark); (ii) across ecosystem compartments (i.e., living and dead bark on canopies, stems, and in litter layers); and, thereby, (iii) across all major hydrologic states and fluxes in forests (providing estimates and contexts where available in the scant literature). The relevance of bark-water interactions to biogeochemical aspects of forest ecosystems is also highlighted, like canopy-soil nutrient exchanges and soil properties. We conclude that a broad ecohydrological perspective of bark-water interactions is currently merited.