Extracellular enzyme activities in plots dominated by trees that associate with arbuscular mycorrhizal or ectomycorrhizal fungi in the nitrogen fertilized and reference watershed at the Bear Brook Watershed in Maine, USA during the final year of N fertilization (2016) and during the year after N fertilization ceased (2017).

Our objective was to detect possible differences in N fertilization responses of extracellular enzymes in plots dominated by trees that associate with arbuscular mycorrhizal fungi (AM) or ectomycorrhizal fungi (ECM). To do this, we established a plot network of 6 AM and 6 ECM dominated (>65% diameter at breast height) 10 x 10 m plots in the lower elevation hardwood zone of both the reference and N fertilized watersheds (N=24 plots) at Bear Brook Watershed, in Maine USA. We assayed the potential activity of hydrolytic enzymes that release N (N-acetylglucosaminidase; NAG), phosphorus (acid phosphatase; AP), and simple carbon (ß-glucosidase; BG). The activities of these enzymes were measured separately in bulk mineral, rhizosphere, and organic horizon soils in the final year of N fertilization at Bear Brook in 2016 and during the year after N fertilization ceased in 2017.