Thinning

After the forest is up and growing, the next silvicultural treatment that is often considered is a thinning. Thinnings are midrotation harvests that are generally considered around age 15 for a pine forest and 30 to 40 for a natural hardwood forest. The purpose of a thinning is two-fold -- to capture the commercial value in weak or dying trees before they actually die and to improve the quality and growth of the remaining trees. In pine plantations where the trees have been planted in straight rows it is common for a row thinning to occur. With a row thinning, all of the trees in a given row, such as every third row, are removed. This would essentially remove a third of the trees in a stand. Normally a thinning is a commercial operation, in which the sale of the wood generates positive revenue. However, sometimes in areas where markets for small trees are poor, thinnings may be pre-commercial operations. These occur in areas where the sale of the wood is not sufficient to cover the costs of the operation. In most cases, these areas do not receive a thinning, at least while the trees are still quite small. In some cases, if tree value is expected to be high and the rotation length is short, pre-commercial thinnings can be economically justified. Planting seedlings at a wider spacing is one way to lessen the need for pre-commercial thinnings.