Estimating Crown Height for Unthinned Planted Pines in East Texas

Stand-level models were derived to predict crown height or the distance from ground to the first live branch of unthinned planted loblolly (Pinus taeda L.) and slash (Pinus elliottii Engelm.) pine trees in East Texas. Average height of the tallest trees was the principal predictor in the models. In addition, the influence of number of planted trees per acre, nonplanted basal area and fusiform rust (Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme ) was considered. The models quantify the plantation ages when the butt log and successive lower stem logs are clear of live branches. This information may assist with merchandising the planted pines. South. J. Appl. For. 21(3):130-133. One aspect of pine plantation ma agement is merchandising the planted trees into appropriate products. Many tree factors can influence the merchandising process, such as diameter, height, crown condition, stem quality, incidence of disease, and the length of lower stem from ground to the first live branch. This length of the lower stem is equivalent to crown height, while the length of the upper stem from the first live branch to the top of the tree is the crown length. Crown ratio is defined as crown length divided by tree height. In addition to merchandising the trees, reliable information on expected values of crown length, crown ratio and crown height may assist in planning: s Number of trees per acre to plant. s Pruning specifications. s Timing and intensity of intermediate harvests. s Specifying optimum rotation ages. Models for estimating crown ratio and crown height for individual trees have been developed in several studies (Ward 1964, Wykoff et al. 1982, Dell et al. 1979, Feduccia et al. 1979, Ek and Monserud 1975, Daniels and Burkhart 1975, Van Deusen and Biging 1985, Dyer and Burkhart 1987). Average stand crown ratio and average stand crown height have been estimated by Holdaway et al. (1979) and Cole and Jensen (1982). A "crown rise" model that estimated crown height on a stand-level basis was developed by Valentine et al. (1994). Several papers presented crown height increment prediction models for individual trees (Short and Burkhart NOTE: Manuscript received December 14, 1995, accepted August 13, 1996. 1992, Maguire and Hann 1990a,b and Liu et al. 1995). In this paper, models are presented to estimate average stand crown height for unthinned loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) plantations in East Texas. Plantation Measurements Information from permanent plots located in unthinned industrial loblolly and slash pine plantations throughout East Texas was analyzed inthis study. 1 In 1982-1984, 256 plots were established in separate plantations to start the East Texas Pine Plantation Research Project (ETPPRP). By 1995, about 25 % of the original ETPPRP plots have been destroyed by inadvertent acts of nature and man. The plots are measured on a 3 yr cycle, and each plot consists of two subplots. A subplot is 100 ft x 100 ft, and all planted pines within a subplot were tagged and numbered At each measurement, values such as dbh, total height, crown height, and occurrence of fusiform rust (Cronartium quercuum [Berk.] Miyabe ex Shirai f. sp. fusiforme) are measured and recorded for each surviving planted pine tree in a subplot In addition, two sampling points are situated within each subplot for measuring and recording dbh values of nonplanted trees. For this study, each subplot was a sampling unit. For an observation to be included in the data sets, crown height had to be 1 ft or more. As a result, the total number of observations 1 Support from participating companies--Champion International Corporation, International Paper Company, Louisiana-Pacific Corp., Resource Management Services, Inc. and Temple-Inland Forest Products Corp --lS appreciated.