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Intensively managed forests of the Southern United States are among the most important sources of wood fiber and timber in this country. There is a great deal of concern that disturbances associated with trafficking by heavy machinery might diminish long-term soil-site productivity. However, determining the effect of harvesting disturbance and silvicultural treatments on the long-term productivity of pine plantations is difficult because, in addition to harvesting effects, growth distributions are affected by changes in climate, silviculture, and genetics. The primary objectives of this study were to determine (1) whether logging disturbances under operationally realistic circumstances affect soil quality, hydrologic function, and loblolly pine (Pinus taeda L.) productivity on wet pine flats, and (2) whether intensive forest management practices mitigate disturbance effects if they exist. Three 20-ha loblolly pine plantations located on wet pine flats in South Carolina were subjected to combinations of wet- and dry-weather harvesting and mechanical site preparations. Changes in soil-site productivity after five years were evaluated using a new rank method. The key advantage of the rank change method is that it is largely independent of the confounding factors (e.g. genetics, silvicultural practices, and climate) that affect comparisons of tree growth and soil quality between growth cycles. After five years, loblolly pine site indexes (base age 25) ranged between 13 and 33 m, and production ranged between 0.5 and 95 Mg ha-1. Soil bulk densities increased from 1.15 to as high as 1.44 g cm-3 after harvesting; by age 7 years it had decreased to approximately 1.25 g cm-3. At the sub-stand scale (0.008 ha), visually assessed soil physical and harvesting residue disturbances had little influence on relative changes in soil-site productivity after five years. Factors that specifically reflect site drainage were the most influential on changes in productivity. At the operational scale (3.3 ha), there were no differences between wet- and dry- harvested sites as long as bedding was applied as a site treatment. These results indicate that when standard site preparation is employed, fertile, wet pine flats such as these are resilient in that they recover from severe, but operationally realistic, harvesting disturbances.

Headwater riparian wetlands form an important hydrologic link between terrestrial and aquatic systems. These wetlands are small and account for only nine percent of the total wetland area in the US, however, they account for nearly half of the upland/wetland edge. Three headwater riparian wetlands were instrumented with flumes, solution samplers and shallow wells to monitor hydrologic and chemical interactions between physiographic positions and streams within the watersheds. The objectives of this study were to examine the general hydrologic and chemical characteristics of such wetlands. Water sampling was conducted in soils and streams during baseflow and stormflow conditions. Cross sections of water tables on wetlands had distinctive differences from those on non-wetlands. Wetland areas had generally level, shallow water tables, while non-wetland bottoms had deeper, more sloping water tables. Calcium concentrations in streams and soils ranged from 2 mg L-1 to 25 mg L-1, and were usually highest on wetland physiographic positions. Magnesium concentrations ranged from 1 mg L-1 to 4 mg L-1 and had similar patterns to those seen for calcium. Dissolved organic carbon concentrations ranged from 5 to 17 mg L-1 and were also highest in wetlands. Total nitrogen concentrations were consistently less than 1 mg L-1 at all positions. Although these wetlands were small, the hydrogeochemical processes occurring were sufficient to alter soil water chemistry. Although wetlands generally had the highest concentrations of the observed solutes, the solute concentrations of non-wetland bottom was closer to wetland values during drier periods on the watersheds.