Site disturbance and soil impacts resulting from mechanized thinning of upland hardwood stands in Southeastern Kentucky
A large scale silvicultural trial was designed to examine the effectiveness of five treatments in reducing the potential future impacts of gypsy moth infestation and oak decline on upland hardwood forests in the Daniel Boone National Forest in southeastern Kentucky. Three of the five prescriptions were implemented with a mechanical harvesting system. The system consisted of a swing-to-tree feller buncher, chainsaw limbing and topping in the woods and skidding with a grapple skidder. The three mechanically harvested prescriptions were shelterwood with reserves, thinning to B-line, and woodland thinning. Each prescription was designed to test the effectiveness of varying degrees of basal area reduction in limiting the impact of gypsy moth infestation and oak decline. After harvesting was complete the point transect method was used to measure site disturbance caused by the harvesting operations. An assessment of soil response was conducted in one area that was subjected to the most intense thinning – shelterwood with reserves. This treatment thinned each stand to 10 – 25 ft2/ac to create a 2 aged stand. Primary soil variables measured included bulk density and soil strength in both pre- treatment and post treatment condition. Bulk density within the soil profile increased in response to thinning. Conversely, soil strength was reduced after thinning that may be the result of higher moisture levels. Soil bulk density increased in response to traffic intensity, as measured by the site disturbance survey, but the reverse was noted for soil strength. The impact of trafficking on carbon and nitrogen was also evaluated by monitoring nitrogen mineralization and carbon efflux. Disturbance intensity influenced nitrogen mineralization while carbon efflux was detected on a limited basis.