Mineral soil carbon and nitrogen still low three decades following clearcut harvesting in a typical Acadian Forest stand

- Decrease in mineral SOM was observed 3 decades following clearcut harvesting.
- Losses of soil C and N may not be evident without inclusion of deep soil.
- Mineral soil pool is more susceptible to harvesting impacts than previously thought.

Intensive forest management practices can alter forest soil organic matter (SOM) storage (kg C ha− 1) due to changes in the environmental variables that control SOM cycling and stability. Here we investigate whether SOM losses are observed three decades following clearcut harvesting in a temperate forest ecosystem that includes the deep mineral soil (to a depth of 50 cm). We compared SOM stored as carbon (C) and nitrogen (N) in paired (35-year-old; 110-year-old reference) Acadian Forest sites that differed only in their time since harvest. We found lower mineral soil carbon (C) and nitrogen (N) storage (27% and 26% respectively), and lower C and N concentrations at the 35-year-old site compared with the 110-year-old reference site. Isotopic compositions of C and N through the soil profile did not provide insight into the dominant mechanisms driving SOM losses at the 35-year-old site in this study. This is the second study to document decreases in mineral soil C and N storage in a red spruce forest within the Acadian Forest Region three decades following clearcut harvesting.