Assessing Change in Soil-Site Productivity of Intensively Managed Loblolly Pine Plantations

摘要

Intensively managed forests are among the most important sources of wood fiber and timber in the southern United States. There is a great deal of concern that wet-weather harvesting disturbances might diminish long-term soil-site productivity. Determining the true effect of harvesting disturbance and silvicultural treatments on long-term productivity of pine plantations is difficult because growth and yield are affected by changes in climate, silviculture, and genetics. Change in productivity rank among treatments was used as a new approach to evaluate harvest disturbance effects on changes in soil-site quality because it is less influenced by the confounding factors that affect tree growth. Three 20-ha loblolly pine (Pinus taeda L.) plantations were subjected to combinations of wet- and dry-weather harvesting and mechanical site preparations. Wet-weather harvesting had no discernable effect at the operational scale (3.3 ha) compared to dry harvesting on changes in soil-site quality when standard site preparation methods were used; however, results based on change in rank for site index indicated that the combination of wet harvesting and flat planting diminished productivity. Polypedon-scale (0.008 ha) investigations indicated that silviculture, inherent site factors, and disturbance affected drainage and changes in soil-site productivity. This study showed that the industrial practice of bedding maintained site productivity of wet-weather harvested stands on wet pine flats. These results are potentially important to nonindustrial private landowners whose plantations are not commonly bedded before replanting.