Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.
In my travels around the mid-Willamette Valley, I am seeing a lot of young conifer stands (generally Douglas-fir up to 20-something years old) with just too many trees. Why do I say there are too many trees?
I know many people in this part of western Oregon who are patiently waiting for their trees to grow, hoping to thin the trees in a selective harvest when the stand is about 25 years old. They plan to sell the harvested trees to cover costs and would like to break-even or make a bit back on establishment expenses.
All too often it is not working out that way. Instead, as the stand approaches the target age they find that trees have already become too crowded, with too many small, slow growing trees in the stand. The trees are still too small to support a profitable harvest thinning operation (also called a commercial thinning). To thin at that point is to do so at a cost, although it may be best for the woodland in the long-run. To delay the thinning and wait for the trees to grow enough to make the thinning harvest profitable is appealing, but deceptive. It may avoid the short term expense, but is likely to weaken the stand at a long-term cost of growth, stand stability and future options. It is a classic “pay now or pay later” situation.
In young stands, the idea is to have the “right” number of well-spaced trees to allow the trees in the stand to grow more or less unchecked until they are big enough to support a harvest (that will break-even), and to do it “on time”, that is before future opportunities are affected by intense competition. This should leave the landowner with a healthy, stable and vigorously growing stand easily shaped to meet any of a wide range of long term objectives that family landowners commonly aim for. These common objectives (see related article about objectives) including habitat diversity, recreational opportunities as well as periodic income, are generally best met by growing trees in longer rotations (>45 yrs) and with multiple thinnings over time. So it is important to get off on the right foot.
Of course there are many nuances in choosing the right spacing for any stand, but I’m saying there is a lot less nuance in the decision leading up to the initial thinning harvest of a young stand than there is in later thinning decisions. It is fairly simple. In a young stand, we want to have the right number of trees to support a timely selective harvest thinning while avoiding excessive competition. This will keep the most options open for the landowner in the future. Continue to next article where we look at what that number might be.