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

Abstract

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.