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A portion of this production was gleaned from an unpublished paper by Craig Blencowe entitled, Craig Blencowe: Building up the Forest.