The Effects of Clear-Cutting on Mineral Soil Carbon Pools in Northeastern Hardwood Forests.

Harvesting forests introduces substantial changes to biogeochemical processes of forests, including physical and chemical alterations to the soil. In the northeastern US, soils account for approximately 50% of total ecosystem carbon (C) storage, with mineral soils comprising the majority of that storage. However, mineral soils are omitted from C accounting models due to variability, lack of data, and challenges to sample collection.

The present study investigated mineral soil C pools in forests that were harvested in the last century and compared them to pristine forests in the same region. We hypothesized that mineral soil C pools would be lower in harvested forests versus forests that had not been harvested for  >100 years. We collected 60-cm mineral soil cores from twenty forest stands across the Northeastern US, representing seven geographic areas and a range of times since last harvest. We compared recently harvested forests to >100-year-old forests and used an information theoretic approach to model C pool dynamics over time after disturbance. We used py-GCMS to quantify and describe the suite of C compounds present in three density fractions of the mineral soil at sites with different management histories. 

There was a trend of higher soil C pools in >100-year-old forests than in harvested forests, but the differences were not statistically significant. Differences between harvested and older forests increased with mineral soil depth. We found a significant negative relationship between time since forest harvest and mineral soil C pools. The relationship between C:N ratio and percent soil organic matter (SOM) varied between harvested and >100-year-old forests. Soil C compounds varied among sites with different management histories, particularly in the heavy fraction of the mineral soil. Our results are consistent with previous studies that found that soil C pools recover slowly to disturbance,