Over time, unthinned stands produce more total fiber per acre than stands that have been thinned, even though unthinned stands produce less vigorous, smaller diameter trees. While this is acceptable for pulpwood production, landowners may be able to get a greater total financial return over the life span or rotation of the stand by making several thinnings to produce more valuable, larger trees suitable for sawtimber and other solid wood products. Intermediate commercial thinnings provide landowners with periodic income as a stand develops. Depending on the growth of the stand, commercial thinning can occur as early as age 12. Most pine stands gain the greatest benefit from thinnings started before age 20.
Subsequent thinnings follow at five to eight year intervals.
Final harvests generally occur between ages 25 to 35 years. Determining when to thin is an important decision. One way to estimate when to thin is by keeping track of the 'live crown ratio' of trees in the stand. Before the average live crown ratio falls below 35 percent, the stand should be thinned. For example, if the average tree height is 40 feet and the average length of the live crown is 14 feet, then the live crown ratio is 35 percent and the stand should be thinned soon.