Marking to Improve Stand Structure

By Thembi Borras

Sustainable forestry is largely determined by how a forest management strategy is interpreted on the ground. Single tree selection does not imply sustainable forestry as it can easily be corrupted by high grading; taking the biggest and best trees. Tree marking, deciding which trees will be cut and which trees will be retained is the most important way a forester translates single tree selection on the ground. Although there are a hundred things to consider before marking a tree, the core criteria to improve stand structure, in descending order of priority, are:

1. Remove damaged, dying, or diseased trees. Generally, trees which may die prior to the next harvest. However, some dying trees may be retained to become snags, which are important to wildlife. This is a “sanitation” strategy.
2. Remove suppressed and intermediate crown class trees. These are trees that neither are presently contributing growth to the stand, nor are they expected to do so prior to the next harvest. This is a "thinning from below” strategy.
3. Remove selected larger trees that improve spacing for the higher quality trees, which will be retained. This is a “spacing improvement” strategy.

Target diameters also guide tree marking. For example, at age 50 the largest redwoods in the Jones Family Forest have not yet reached the target diameter of 36" specified in the long term management plan. Therefore, selection leans toward retaining the largest trees.

At age 80, the largest redwoods in the Jones Family Forest have reached the target diameter and selection leans toward removing them to benefit smaller diameter trees. However, not all trees that have reached the target diameter are cut. They are simply preferred if the situation warrants. In a situation where 18" to 24" redwood trees on the north side of the clump would benefit if the 36" tree on the south side were removed, then cutting the target diameter redwood may be warranted. If the removal of the target diameter tree will not benefit surrounding conifer trees because it is out on its own then retaining it may be warranted.

In conclusion, each harvest is used as an opportunity to upgrade overall stand quality by choosing which trees are retained and how they are spaced.

A portion of this production was gleaned from an unpublished paper by Craig Blencowe entitled, Craig Blencowe: Building up the Forest.

A Type of Forest Management

By Thembi Borras

I did not leave college knowing how to practice sustainable forestry on the ground. In fact, if I had depended solely on what I had learned in college I would not have thought the type of forest management I have learned and been privileged to implement for the last seven years was viable because, in part, economic return is not maximized. The type of forest management that I now use is quite simple. First, establish a long-range sustained yield goal based on the productive capacity of the site and a reasonable growth rate. After the long range sustained yield goal is established, build inventory by cutting less than growth until the goal is met. Once the goal is met, growth can be harvested. The other aspect of this approach is to improve stand structure by not cutting the biggest and best trees.

Although short-term profit is not maximized this approach provides a periodic income to the landowner and is an effective way to support forest related values. Pre harvest habitat is the same as post harvest habitat, so wildlife habitat does not decline. Aesthetics are bolstered by maintaining a continuous forest canopy and encouraging fewer large stems as opposed to many small stems. Also, this type of forest management can minimize adverse watershed effects through the low level of canopy removal. The lower the level of canopy removal the lower the increase in peak flow. Conversely, an increase in peak flows can mean an increase in sediment production.

Other arguments against this type of forest management, which can be described as a light intensity single tree selection, are natural regeneration suffers due to lack of adequate light and reentry every 10 to 15 years does not allow the land to rest. While these arguments have some validity, they are not insurmountable. Redwood sprouting is usually adequate post harvest but it is sometimes necessary to remove trees in small groups to encourage Douglas-fir seedlings. In addition, seedlings can be interplanted in openings created by the harvest to supplement natural regeneration. Finally, periodic entry every 10 to 15 years is an opportunity to improve a permanent truck road and skid trail network and correct accessible legacy problems.

A portion of this production was gleaned from an unpublished paper by Craig Blencowe entitled, Craig Blencowe: Building up the Forest.