NITROGEN MINERALIZATION IN BOREAL FOREST STANDS OF ISLE-ROYALE, NORTHERN MICHIGAN

The correlation of soil temperature and moisture with inorganic N concentrations and net mineralization beneath major species types in mature boreal and northern hardwood forests was examined over a two year period. Soils beneath species types where the canopy was dominated by Betula papyrifera, Picea glauca, Alnus rugosa or, in northern hardwoods, Acer saccharum were studied. Net NO3- mineralization varied by species type and net total inorganic nitrogen (N) mineralization varied by month and the interaction of species type with month. Soil NO3- concentration and NO3- mineralization were correlated for spruce, and inversely correlated for alder and maple. Soil NH4+ concentration and NH4+ mineralization were inversely correlated for alder and maple. In laboratory temperature and moisture treatments of birch, spruce and maple soils, NH4+ and total inorganic N-mineralization increased with temperature. The response to moisture was most evident for NO3- mineralization in maple soils.