An Individual-Tree, Merchantable Stem, Green Weight Equation for Loblolly Pine Pulpwood in Arkansas, Including Seasonal Effects

An individual-tree, merchantable stem (3-in. top), outside-bark, green weight equation was developed for loblolly pine pulpwood trees in southeast Arkansas. Trees were sampled from the same eight stands over the four seasons of the year; therefore, stand-to-stand variation did not impact results. Specific gravity did not differ within stem position across seasons. However, seasonal differences in moisture content led to different weight scaling factors by season, the largest weight scaling factor occurring in spring. As a result, the weight equation is parameterized differently based on season of the year. Stand origin (natural regeneration versus plantation) did not significantly impact weight scaling factor. The fitted equation explained 97% of the variation present in the data and possessed a mean absolute error of 24.1 lb per tree. Assuming the climatic conditions during the project were typical; up to a 6% difference in estimated merchantable stem weight occurs based on season of the year. Use of this equation and these results should assist those inventorying, buying, and selling loblolly pine pulpwood by weight in southeast Arkansas and nearby surrounding regions.