Nitrogen dynamics in upland and peatland Boreal Shield soils before and after clearcutting

Patterns of nitrogen (N) dynamics among upland deciduous and conifer stands and peatlands were measured before and after clearcutting in three Boreal Shield catchments. Net mineralization and nitrification rates did not differ among forest stands due to similar soil C and N content, pH, moisture and temperature. Gross mineralization and nitrification rates were generally 10 to 100 times larger than net rates. Gross nitrification rates were higher in the recently logged conifer stand and peatland compared to the uncut stands. However, net nitrification remained low because nitrate limited conditions led to 100% immobilization. Examination of net mineralization and nitrification rates in conifer regeneration plots of varying ages showed elevated net nitrification but not mineralization rates in 2 and 11 yr old conifer stands. No coincident increase in soil nitrate was observed. These data imply a low potential for N loss post-harvest and little change in N availability for regenerating vegetation.