Tongass National Forest

Timber Stand Improvement

Precommercial Thinning

As prolific regeneration reaches about 15 years of age in young-growth (second-growth) stands of Southeast Alaska, dense canopies begin to promote competition for available resources. Precommercial thinning, which is the removal of trees not for immediate financial return but to reduce stocking to concentrate growth on the more desirable trees, has been the preferred treatment.

The objectives of precommercial thinning include:

1. Increasing timber yields by delaying the occurrence of competition for growing space between fast growing young trees. The site's wood growing potential is distributed over a few trees instead of many. This results in larger diameter stems over a shorter time span.
2. Favoring a stand's particular species composition and ultimate yield and value through favoring of that species as future crop trees.
3. Removing the deformed, diseased trees.
4. Prolonging the understory vegetation for wildlife use by delaying crown closure.

Young-growth stands in Southeast Alaska suffer from excessive competition for light because of the large number of young trees that grow back in harvest areas. Because hemlock and spruce are shade tolerant, the young stands have low mortality rates and trees do not express strong dominance in the first half of a rotation. Significant natural thinning through competition occurs late in the stand's life. Precommercial thinning will result in larger diameter trees over shorter time periods, increasing sawlog yields about 10-12% and reducing rotation length by 10 to 20 years. Funding has been available to treat about 2/3 of past harvest areas. Recent targets in precommercial thinning on POW have averaged 2000-3000 acres per year. Most of the thinning is contracted out through the bidding process. Contracts open for bidding are listed on the internet at FedBizOpps. Use "thinning contracts Prince of Wales Island" in the search. More information is available at the district offices and at the contracting department, Ketchikan Forest Service office.