Rehabilitation of understocked loblolly-shortleaf pine stands. I. Recently cutover natural stands.

Two loblolly-shortleafpine (Pinus taeda L.-P. echinata Mill.) stands were cut to stocking levels of IO, 20, 30, 40, and 50% to simulate recently cutover, understocked, uneven-aged stands. Number of trees rangedfrom 38peracrefor 10% stocking to 213peracreforSO% stocking; comparable total basal areas were 4 and 16ft2/ac, respectively. One stand was on a good site (site index = 9Oft at age 50), the other on a medium site (site index = 75 ft at age 50). As a rehabilitation treatment, all hardwoods 1 in. groundline diameter and larger were injected with a herbicide. At 2, 5, IO, and 15 yr after treatment, the stands were inventoried to determine: (1) rate at which the understocked stands recovered, and (2) minimum stocking levels requiredfor successful rehabilitation. During 15 yr of rehabilitation, the understocked stands changed dramatically, and because of rapidgrowth of residualpines, stocking levels, basal areas, and tree volumes increasedmarkedly. Stands having at least 20% residual stocking and .5ji2/ac ofpine basal area reachedan acceptable stocking level of 60% (based on number and size of trees), or 45ft2/ac of basal area within 15 yr. Stands at this minimum stocking thresholdproduced 4,600 bdft(Doyle)/ac of sawtimber volume on the good site and 3,000 bdft/ac of sawtimber volume on the medium site during the 15 yrperiod. The study indicates that recently cutover, or damaged, understocked stands with at least 20% to 30% stocking or 5 to 10 ft2/ac of pine basal area can be rehabilitated to produce respectable sawtimber volumes. This management strategy provides a low-cost alternative to establishing a new stand at considerable cost to the landowner. South. J. Appl. For. 22(1):35-40. A 1988 USDA Forest Service report indicated that 22% (40 million ac) of the commercial timberland in the South was understocked (less than 60% stocking) with desirable tree species for timber production (USDA Forest Service 1988). The understocked stands are usually the result of past harvesting practices, natural catastrophes, or regeneration failures. Understocked conditions can occur in three stand types: (1) recently cutover or damaged stands, (2) stands cutover or damaged some years ago, but left unmanaged, and (3) seedling or sapling stands following a regeneration failure or damage. A forester encountering an understocked stand must decide whether to manage the existing stand, with a possible Note: Manuscript received July 1, 1996, accepted March 3, 1997. James Baker is the corresponding author and can be reached at (870) 3673464; Fax (870) 367-l 164. This research was done in cooperation with the Mid-Continent Division of Georgia-Pacific Corporation and the Arkansas Forestry Commission, both of which provided the study sites and assisted in timber harvesting operations, Use of trade names is for reader information and does not imply endorsement by the U.S. Department of Agriculture to the exclusion of any suitable product or process. All uses of pesticides must be registered by sacrifice in production, or to prepare the site and regenerate the area to obtain better stocking, at an additional cost to the landowner. Before a prudent decision can be made, the forester must have answers to the following questions: (1) How long will it take the understocked stand to approach an acceptable 60% stocking level? (2) What is the threshold of stocking that is feasible to manage? During the early to mid1980s a series of studies was established in southern Arkansas and northern Louisiana to help answer these questions for several understocked stand conditions. Results of these studies are given in a series of papers, beginning with this one. The study described here was conducted in recently cutover, uneven-aged loblolly-shortleaf pine (Pinus taeda L.-P. echinata Mill.) stands on two sites. Recovery and development of the stands are reported for a 15 yr rehabilitation period. An earlier paper reported 5 yr results (Baker 1989).