Tag Archives: thinning

Thinning and selective management of maturing Douglas-fir forests (part 1)

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Glenn Ahrens, OSU Forestry and Natural Resources Extension Agent – Clackamas, Marion, and Hood River Counties

Many family forest owners I meet have older trees and forests – 60 to 80 or more years old – and they would like to retain mature forest conditions. They are interested in periodic thinning, selective harvesting of trees or small patches, and keeping options open for the future. But landowners with larger older timber often hear that they are better off, from an economic and operational standpoint, to clearcut a patch and regenerate it all at once.

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Potential drawbacks of Young Stand Thinning

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Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension agent, Benton, Linn and Polk Counties.

We have been dedicating a fair amount of screen space and class time lately to the idea that many family forest landowners would benefit from thinning their young stands. We explored the reasons to consider young stand thinning (YST) as well as some approaches in a series of posts on YST .  YST is consistent with the situation and goals of many family forest landowners, which often include growing older and more diverse forests.

That said, like many other well-grounded activities, YST is not without some potential drawbacks.

Few of them are significant enough to justify not thinning at all, but each requires some thought and consideration to avoid unintended consequences. We present some of those potential drawbacks that you need to consider when planning a YST, along with some links to other information, below. Continue reading →

Measuring plots in the woods

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Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension agent for Benton, Linn and Polk Counties

In this series about young stand thinning , I’ve worked on the assumption that people know the density of trees in their woods. I realize that in many cases, people don’t really know that, so cannot easily apply that information to deciding if they have enough room for healthy growth or if trees need to be thinned.

If you know what distance the trees were said to have been planted, you may have a fair idea of the density (a 10’ x 10’ spacing is about 440 trees per acre, a 12’ x 12’ is about 300 tpa). This is a good start, but not necessarily very accurate.   Actual planting spacing can vary quite a bit according to the conditions in the field and experience of the planters.  And of course some seedlings die during establishment, or some other trees may seed in from outside.  So it is probably a good idea to go out and get a better idea of what you’ve got.  The basic way to do this is to measure some plots. Continue reading →

Preparing for thinning

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By Amy Grotta, OSU Forestry & Natural Resources Extension, Columbia, Washington & Yamhill Counties

This month we have been spending some time at the Matteson Demonstration Forest getting ready for a commercial thinning project. The actual logging will happen next summer, but we are taking care of road improvements, surveying property lines, laying out the harvest boundaries and marking the stand now, so that we are ready to go when the contractor is available.  OSU forestry students who are summer interns with the OSU Research Forests gained hands-on experience by doing a lot of this work.

OSU Research Forests staff Brent Klumph and Steve Fitzgerald, and interns Becca and Zane discussing harvest layout

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Growing a Diverse Forest: Steps to a Structural Diversity “Forest Makeover”

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By Amy Grotta and Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension

Through a creative and carefully planned harvest, this mature forest has undergone a structural diversity makeover.

Continuing our series, we’ll now look at steps that woodland owners can take to enhance structural diversity in their forests.  Recall that “structural diversity” refers to the amount of three-dimensional variation in the forest. In other words, a structurally diverse forest has trees of different sizes arranged in uneven patterns across the site.

Why do we care about structural diversity? Structural diversity is important to creating an “older” or “natural” forest look that many people want on their property.

Structural diversity is also a very important part of wildlife habitat. Continue reading →

Young Stand Thinning Strategies

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Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.

DSCN3241Continuing on the general theme of young stand management and especially the need for thinning, I’d like to look at strategies for thinning a young stand. Let’s start with some things to keep in mind about Young Stand Thinning or YST (also called precommercial thinning or PCT):

  • The idea of young stand thinning (YST) is to avoid harmful overcrowding later by removing excess trees early on.
  • The impact of thinning out a tree is very local. The overall stocking level (trees per acre) can be misleading. It is the spacing among immediate neighbors that counts.
  • The greatest benefit of YST is increased growing space rather than selection among trees. Creating more growing space to benefit as many leave trees as possible is the primary goal. Culling is secondary.
  • YST is key to achieving longer rotations and many non-timber objectives many family forest landowners desire.

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Don’t forget about young stand thinning

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Many aesthetic and habitat objectives of family forest landowners come with older, less dense stands like this stand of about 70 years. It is important to get on this path early.
Many aesthetic and habitat objectives of family forest landowners come with older, less dense stands like this stand of about 70 years. It is important to get on this path early.

Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.

In previous segments I argued that many people have too many trees in their young stands   which may be costly and harmful to the long term growth of the stand. Most importantly, having too many trees at this stage can undermine common landowner objectives of growing attractive, longer rotation diverse forest habitats and can force landowners into shorter rotations than imagined.

While this suggests that people should think about planting fewer trees per acre in the future (a step deserving some careful consideration), it highlights the need for thinning in many existing young stands to correct overstocking at an early age. This may include your stand.

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Spacing young conifer stands

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Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.

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In a previous article , I wrote that many folks in NW Oregon are growing too many trees in young stands given some common family forest landowners’ objectives, including doing a selective thinning harvest when the trees are in their mid-20s.  While on their way towards a variety of longer-term objectives and stand conditions, most people are hoping that their initial harvest will at least break even (when it is sometimes called a commercial thinning).  So we need to focus on reaching that first thinning harvest in a timely manner and leaving the stand in a good condition to meet future objectives. Let’s begin by looking at what it takes to have a successful thinning harvest.

My contacts in the business around the mid-Valley tell me that while the first thinning harvest should provide a mix of saw logs and chip logs, most of the surplus trees removed in the thinning need to produce a sawlog or two if you hope to break even or make a little money (a mix of around 2/3 saw logs and the remaining 1/3 chip logs is a rule of thumb used by some). Too many small logs and the operation is costing money. That sawlog will vary according to the mill it is headed to, but is generally 20 feet to 32 feet long with a 6 or 7 inch top. Smaller wood goes to chip and saw or pulp.

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Many young stands too crowded

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Brad Withrow-Robinson, Forestry & Natural Resources Extension Agent, Benton, Linn and Polk Counties.

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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.

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