Sapwood and heartwood width relationship to tree age in Pinusbanksiana

Abstract

The relationships of sapwood and heartwood width with tree age were studied in 101 trees of Pinusbanksiana Lamb. The sample trees were selected from natural stands growing at various stand densities at the Lakehead University woodlot, Thunder Bay, Ontario, and ranged in age from 6 to 97 years at breast height. The number of rings in both sapwood and heartwood and their respective widths were recorded. The sapwood basal area was expressed as the difference between the stem basal area and the heartwood basal area. A linear relationship was found between tree age and sapwood width, sapwood basal area, and heartwood width. A curvilinear relationship was observed between the number of rings in the sapwood or heartwood and tree age. The number of rings in sapwood increased at an average rate of 0.43 ring per year until the tree reached the age of about 70 years. The number of rings in sapwood was, more or less, constant after 70 years. Heartwood began to form at about the age of 6 years. Heartwood was produced at the average rate of 0.57 ring per year until the tree reached approximately 70 years. After 70 years, the average rate of heartwood expansion was 1 ring per year. It is concluded that tree age is one of the main factors that controls sapwood and heartwood width.