Paper reports on productivity of loblolly pines on wet sites 23 years after harvesting

Intensively managed pine forests occur throughout the southeastern United States and provide a large proportion of global demand for forest products. Many of these forests are located on coastal plain wet flats.
Managers typically seek to avoid using heavy equipment during wet site conditions, but sometimes use of heavy equipment cannot be avoided and can potentially affect soil properties and site productivity. Some sites have natural mechanisms, such as sediment deposition, that facilitate long-term recovery from soil disturbances. However, site preparation techniques, such as bedding, also can be used to enhance soil properties and productivity.

Recently, Virginia Tech, the U.S. Forest Service, and NCASI collaborated to study the long-term response of loblolly pine forests on wet sites 23 years after harvest and site preparation. The investigators reported study results in a paper published in Forest Ecology and Management. Authors include Charles M. Neaves III, W. Michael Aust, Chad Bolding, and Scott M. Barrett of Virginia Tech, Carl C. Trettin of the USDA Forest Service, and Eric D. Vance of NCASI.

The abstract for the paper follows.

“Ground based timber harvesting on wet sites has been linked to alteration of soil properties that may result in reduced long term site productivity. Following Hurricane Hugo in the fall of 1989, numerous salvage logging operations were conducted under high soil moisture conditions to reduce wildfire risk and salvage timber within the Francis Marion National Forest in the lower coastal plain of South Carolina. Study sites were established on wet pine flats to examine the long term effects of primary skid trails and site preparation on planted loblolly pine (Pinus taeda L.) growth. Treatment effects were analyzed as a split-plot within a randomized complete block design with 12 blocks, four levels of site preparation (none, disking, bedding, disking with bedding), and two levels of machine traffic (primary skid trail, no obvious traffic). After 23 years, bedding and disking with bedding enhanced stand density (p < 0.0001) and above ground stand biomass (p < 0.0001) relative to the disking and non-site prepared treatments. None of the site preparation treatments were effective at increasing biomass of individual trees. Mean height (p < 0.0001), DBH (p < 0.0001), and biomass of individual trees (p < 0.0001) were lower on primary skid trails than in non-trafficked areas. Traffic did not have a significant effect on stand density (p < 0.4662) or stand biomass (p = 0.1564). Selected soil physical properties and productivity measurements were similar for the non-site prepared treatment on and off primary skid trails, suggesting that 23 years is sufficient time for soils in wet flats to naturally recover from wet weather harvest disturbance. This study indicates that bedding may be the most efficient management practice to enhance long term stand productivity for loblolly pine on aeration-limited sites by increasing seedling survival. Minimizing the spatial extent of skid trails may increase growth of individual trees.”

 

Reference 

Neaves, C.M., W.M. Aust, M.C. Bolding, S.M. Barrett, C.C. Trettin, and E.Vance. 2017. Loblolly pine (Pinus taeda L.) productivity 23 years after wet site harvesting and site preparation in the lower Atlantic coastal plain. Forest Ecology and Management 401:207-214. https://doi.org/10.1016/j.foreco.2017.07.007