Stem Sinuosity Changes in Young and Merchantable Stands of Pinus taeda

A survey of stem sinuosity severity and occurrence was conducted on six sites in North Carolina and South Carolina (USA) in Pinus taeda stands approximately 2 years after establishment. Approximately 1,400 trees on each site were measured for height, diameter, and degree of sinuosity in the stem at the beginning of the growing season and again after the completion of the growing season. Fifty-two percent of the trees increased in sinuosity over the growing season. Using stand records and observations by local foresters, two mature stands of loblolly pine (Pinus taeda) were located in the Atlantic Coastal Plain, where excessive stem sinuosity was reported to be present at ages 1 to 3 years. Seven trees were felled from each site. The 2.4-m butt logs were removed from each tree along with a 0.61-m bolt from the remaining felled tree. Slices were then cut through the log progressing through the pith. A single veneer containing the pith from each log was then selected for calculation of log volume, juvenile wood volume, and the volume of sinuous growth. Seven trees at the two sites were found to have had severe sinuosity earlier in their lives. Of the seven sinuous trees, three trees took only 1 year to correct the sinuous growth and return to a normal growth pattern. Two trees took an additional year to return to cylindrical growth, one tree returned to normal growth after the third year, and a single tree returned to a straight appearance by the end of the fifth year after the initiation of sinuous growth. Therefore, the sinuous portions of all seven trees were entirely contained within the juvenile core of the tree. Clear static bending specimens were machined and tested. Trees that were found to be nonsinuous produced mature wood that was significantly stiffer than the sinuous trees.