A Simple Competition Assessment System Associated with Intensive Competition Control in Natural Loblolly - Shortleaf Pine Seedling Stands1

A simple competition assessment system was evaluated a.s part of an intensive competition control study in a natural, even-aged stand of loblolly-shortleaf pine (Pinus taeda L.-P. echinata Mill.) seedlings in southern Arkansas. Four levels of competition control were 1 Cooperation was provided by the following organizations: Department of Forest Resources, University of Arkansas at Monticello; Georgia-Pacific Corp.; BASF Wyandotte Corp.; Dow Chemical Co.; E. I. duPont deNemours & Co.; and Monsanto Agricultural Products Co. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture of any product or service to the exclusion of others that may be suitable. 8 SJAF 13(1989) maintained annually for 3 years as follows: (1) no competition control, (2) woody competition control, (3) herbaceous competition control, and (4) total control of nonpine vegetation. The competition assessment system is based on a correlation of total height to groundline diameter (gld) for lob1011~ pine seedlings that are less than 6 ft tall. The correlation indicated that ifseedling glds are not within + 10 mm of total seedling height (in feet) multiplied by 10, then the seedlings would most likely show a positive growth response to competition control. South. J. Appl. For. 13(1):8-12. I n loblolly pine management, considerable emphasis is placed on site preparation to facilitate natural or artificial regeneration of cutover lands. Traditionally, operational site-preparation treatments are considered to be successful if they result in well-stocked stands of loblolly pine seedlings that grow in height at a rate equal to or exceeding that of reinvading competition, at least until the time of crown closure when the pines dominate the site. However, there has been increasing evidence in the last 10 years that supplemental control of competing vegetation during the time between pine establishment and crown closure can produce substantial pine growth gains in both height and diameter (Haywood a n d T i a r k s 1 9 8 1 , Nelson et al. 1981, Knowe et al. 1985, Tiarks and Haywood 1986, Zutter et al. 1986, Bacon and Zedaker 198’7, Miller et al. 1987). In studies where the effects of various components of competition (woody and herbaceous) have been examined, competition from herbaceous species rather than woody species has been found to contr’ibtite to significant loss in pine growth through the first 5 years following pine establishment. Results from these intensive competition control studies represent unique standards of pine growth response to which operational treatments can be compared. The problem faced by forest landowners in light of these research findings is how to assess a potential response from competition control in stands of pine reReprinted from the Southern Journal of Applied Forestry, Vol. 13, No. 1, February 1989 genera t ion . Some e labora te systems for assessing competing vegetation are being used or proposed for use in young southern pine plantations (Zedaker 1983, Zutter et al. 1985, Weise and Glover 1987). Such assessment systems can be rather labor-intensive and often subjective. The purpose of this paper is to present a competition assessment system that should help forest managers determine whether or not pines will respond to competition control in naturally regenerated stands of loblolly pine seedlings.