EFFECT OF ROTATION AGE ON LUMBER GRADE, YIELD, AND STRENGTH OF UNTHINNED LOBLOLLY-PINE

This study examines the effect of rotation age on the grade, yield, an d strength of lumber produced from unthinned loblolly pine stands in t he coastal plain of Georgia. Six stands representing 22-, 28-, and 40- year rotations were sampled. A stratified random sample of trees with diameters at breast height ranging from 8 to 16 inches was selected fr om each stand and processed into lumber. The strength, yield, and grad e of lumber produced increased with increasing rotation age. Based on study data, equations were developed to predict total lumber volume, l umber volume by lumber grade, sawlog stem weight, and cubic volume. Be cause the yield of higher grade lumber increased in older trees, the v alue of lumber produced per cubic foot increased significantly with in creasing age. A financial analysis of a simulated plantation harvested at ages ranging from 20 to 40 years illustrates the effects of increa sing lumber value and rotation age on net present value of an unthinne d loblolly pine stand.