Accuracy of tree grade projections for five Appalachian hardwood species

摘要

The potential value increase of individual trees is an important factor in planning effective forest management strategies. Similar to other investments, trees with high potential value increase are retained and allowed to grow, and those with relatively low potential value increase are harvested so that the proceeds may earn a higher rate of return elsewhere. Tree grade is used to assess the quality and value of wood within a tree; thus, projecting tree grade is an integral part of estimating potential value increase. This study measured the accuracy of projected tree grades over a period of 12-15 years for 588 black cherry, 404 northern red oak, 167 red maple, 191 white and chestnut oaks, and 450 yellow-poplar sawtimber trees in both thinned and unthinned stands. Projected grade was based on surface defects and percent volume deductions for sweep, crook, and rot at the time of the projection with the assumption that the threshold dbh for the highest possible grade would be reached in the future. This approach allows the forest manager to make grade projections based on what is visible and measurable on the tree, even if the tree is currently too small to qualify for higher grades. In general, grade projections were somewhat accurate, with 9% of trees higher than the projected grade, 80% projected correctly, and 11% lower than the projected grade. Trees that had a lower-than-projected grade usually exhibited additional deductions for percent cull volume and/or new epicormic branches. Grade projections were less accurate for larger, higher-quality trees because requirements for the top grade are more constraining and sensitive to changes in butt log characteristics than lower grades. For black cherry and northern red oak, grade projections in thinned stands were less accurate compared with unthinned stands because of resulting logging wounds or new epicormic branches.