Denitrification Along a Restoration Gradient of Southeastern Massachusetts Cranberry Bogs



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American cranberry, Vaccinium macrocarpon, is a wetland fruit native to North America. Cranberries are commercially grown in bogs, which are a type of wetland. The industry has dominated southeastern Massachusetts for over a century, but decreases in yield, increases in costs of maintenance, and few changes in demand are forcing some Massachusetts cranberry farms to close. As cranberry farming stops in these historic wetlands, landowners will have to choose how to next use their land. One option under consideration is wetland restoration. Millions of hectares of wetlands are being restored in response to global wetland losses over the past several decades. While many wetland restorations replace acreage of wetlands lost, restored wetlands often do not perform ecosystem functions at the same scale as natural wetlands, such as nitrate removal and water quality improvement through the process of denitrification. This study compared denitrification potential in cranberry bogs along a restoration gradient that included an active farm, a retired farm, a restored farm, and a natural reference wetland that had not been farmed. I measured denitrification potentials as well as soil properties likely to influence denitrification, including soil organic matter, moisture, microbial biomass nitrogen, and microbial biomass carbon. Results indicate significant differences in denitrification potential along the restoration gradient, in which the natural wetland was more than 1000 times greater than the active farm. Retired farms had 20 times greater denitrification potential than an active farm and restored wetlands had 50 times the denitrification potential of the active farm. However, denitrification potential of the restored wetland was only 5% of natural reference levels. Soil organic matter, moisture, and microbial biomass nitrogen showed significant differences across the restoration gradient and showed significant positive relationships with denitrification potential. Continued monitoring of restored sites over time is critical to determine the efficacy of cranberry bog restoration in reestablishing denitrification and associated soil properties.



denitrification, restoration, wetlands, cranberry bog, soil