Study investigating long-term effects of wet-weather forest harvesting

Wet weather harvesting is a common practice in the US Southeast Coastal Plain and has the potential to compact soils, restrict drainage, and alter survival and growth of intensively managed pine forests. Mechanical site preparation and fertilization are common ameliorative techniques used on such areas and have been shown to be beneficial, particularly at the stand level.

Twenty-five years ago, a study was established in the Francis Marion National Forest in South Carolina to evaluate soil and vegetative effects of primary skid trail rutting and churning as ameliorated with four types of mechanical site preparation (none, disk, bed, disk and bed) with two levels of fertilization (none vs. 10-10-10). Non-trafficked controls for treatment combinations were located adjacent to the trails. Four-year study results indicated positive effects of bedding and fertilization on both survival and growth of planted pine. 

Twenty-five years later, a project is underway on these same sites to examine the long-term effects of these practices on tree and stand growth and soil physical properties. Dr. Michael Aust of the Department of Forest Resources and Environmental Conservation at Virginia Tech is leading the project with NCASI support. Dr. Eric Vance is managing NCASI involvement in the project.

Investigators were able to relocate almost all of the plots installed 25 years ago, and data collection has been completed. Investigators collected soil cores and bulk core samples and made measurements of mechanical resistance, soil moisture, tree density, diameters, and heights, and soil profile descriptions. Laboratory analysis is ongoing for bulk density, porosity, saturated hydraulic conductivity, nutrient analysis, and soil carbon. The investigators anticipate completing the study by mid-2017.


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