Ditch Restoration in a Large Northern Michigan Fen: Vegetation Response and Basic Porewater Chemistry

Abstract

Following a prolonged drought, more than 7,250 ha of a large fen complex in Michigan’s Upper Peninsula burned in late summer of 2007. As part of fire-fighting efforts, over 48 km of bulldozed firebreaks were made in and around the peatland. In 2008, the State of Michigan restored over 32 km of firebreak in upland areas, but 14.5 km through the fen proper remained as open-water ditches. In the fall of 2009, we restored 2 km of ditch by replacing spoils with an excavator. In addition to ditch filling, we conducted experimental plantings of 18 species of vascular plants and 6 mosses to test the effectiveness of seeding, moss diaspore application and mulching. Surveys during the first and second summers found excellent regrowth of vegetation both within the treatment plots and the controls. Contrary to most published results, the unmulched plots had the greatest vegetative cover and richness of plant species, followed by the mulched plots and the unplanted controls. By 2011, mean vegetative cover on the treatment plots had exceeded the undisturbed ones. Our results indicate that filling is an excellent method of ditch restoration in fens and that seeding increases both plant cover and species richness. Conversely, the addition of moss diaspores and mulch were apparently unnecessary in this case, as moss cover in treatment and control plots was similar along the length of the ditch, likely because of the perennially high water table and the presence of living diaspores in the replaced spoils.