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Updated: 9 hours 35 min ago

Don’t forget about pre-commercial thinning

Wed, 03/30/2016 - 10:01am
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 pre-commercial thinning in many existing stands to correct overstocking at an early age. This may include your stand.

But pre-commercial thinning (PCT) seems to have fallen out of common practice lately. It has come to be seen (mistakenly, I think) as an avoidable expense rather than an important investment in the stand. An investment that begins to shape how the stand will look and behave in the future and which adds resilience and options to the landowners’ woodland portfolio.

The idea of PCT is to avoid harmful overcrowding later by removing excess trees early on. PCT lets the remaining “leave trees” grow faster and larger before serious crowding sets in. This means that trees reach a usable size sooner, and hopefully allows the very important first thinning harvest (also called a commercial thinning) to be done “on time” when the stand is in its 20’s.  This first thinning harvest  is costly and the difference between it being another  big expense for the landowner rather than breaking even or even paying some small profit, often comes down to the size of the trees harvested.  PCT is meant to ensure that this very important thinning harvest operation can pay for itself.

Ideally, young Douglas-fir stands in Western Oregon should be thinned when the dominant trees are about 15 feet tall, or about 10 years old around here.  Yikes, that seems early.  Frankly I don’t know many people who are thrilled about thinning trees they just barely got established and free to grow.  People are looking forward to the trees’ shade suppressing hated weeds like blackberries and broom and are inclined to postpone PCT until the weeds decline and the stand begins to “look crowded”.

Why thin so early? Even by the time trees are 15 feet, you can already begin to distinguish the good trees from the bad.  The trees are past browse and should be beating the weeds.  Once that has happened, the sooner you remove the extras and limit competition among trees, the stronger the beneficial effects and the less the costs of the PCT will be.  Yes, it may be possible to delay until trees are 30 feet tall, but waiting until crowns close and competition begins means a loss of some growth that you would rather have on your leave trees.  Also by the time trees look crowded to many people, it is getting very late.

Referring to the illustrations of the previous article, the recommended  timing of a PCT is meant to occur well down in the uncrowded green zone, well before competition gets going in the Goldilocks zone.   The PCT is meant to shift your stand from the right-hand column to the left-hand column, with more room and  new growth potential until it is time to you your first thinning harvest.

An earlier PCT also means it can be done more efficiently and cheaply. Small trees can be felled much more quickly with less slash building up. There is little concern about stand stability, or delayed growth response when trees are thinned early.

My point is that if an area was planted at a 10×10 spacing (440 TPA) and had good survival, the stand will get too crowded before the trees are big enough for a thinning harvest.  If that is the case, it should be PCT’ed down to at least 300 TPA, meaning you may need to remove a quarter to a third of the trees (110 to 145 TPA).  This is a lot of work, even when trees are small, which takes us to some good advice for many family forest landowners: “Thin early and thin often”.

I’ll give some strategies for thinning in a later article.

The post Don’t forget about pre-commercial thinning appeared first on TreeTopics.

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Resources in the fight against weeds

Tue, 02/23/2016 - 9:21am

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


Pretty much every landowner I know has a weed issue.

Some are fairly short term and narrow, such as controlling common weeds in a new tree planting. Others are much longer term and less defined, such as keeping invasive species at bay in the woodland, or perhaps encouraging  native plants in a meadow or streamside restoration.

There are multiple approaches to weed management, including preventing new weed introductions, mechanical or physical control such as mulching or mowing and the use of herbicides. Most people use a mix of two or more of these approaches, with many including herbicides as one of the methods they use.

Here are some key resources to help you manage your weed issues.


Invasive Weed Identification and Management EC 1563 

It is important to know the enemy, and this is a good place to start, beginning with the 3-page introduction. This publication goes on to describe the identifying characteristics, origin, habitat, ecology and management strategies for selected invasive weeds in the Pacific Northwest. This list is not inclusive of all invasive weeds, but focuses on the most dominant or potentially invasive species that plague us. Check PNW Weed Management Handbook for current herbicide recommendations.


The Nature Conservancy’s Weed Control Methods Handbook

A useful resource for many types of landowners, the Weed Control Methods Handbook: Tools & Techniques for Use in Natural Areas provides detailed information about weed control techniques including manual and mechanical methods, grazing, prescribed fire, biological control, and herbicides.  Check PNW Weed Management Handbook for current herbicide recommendations.


2015 PNW Weed Management Handbook  

This handbook is designed as a quick and ready reference for weed control practices and herbicides. It covers an array of weed control issues, but its real value is in providing professionals with current information about herbicides used in agriculture, forestry and other situations. If you use herbicides as part of your weed management strategy, then you ought to be consulting this book to find important details on the effectiveness and selectivity, rates, and timing of individual herbicides. Like so many other things in life, timing is everything in weed control too.

Important sections include:

  • Pesticide Safety (Section B)
  • Agrichemicals and their Properties (Section c)
  • Forestry and Hybrid Cottonwood (Section K)
  • Christmas Trees (Section P)

The pesticide safety section is essential reading.

Hardly Shakespeare’s sonnets, the chemical properties section has important facts about individual herbicides, including both common name and trade name, mode of action and toxicity.

The forestry section includes an excellent discussion of vegetation control with herbicides, covering woody and non-woody (herbaceous) plants separately. The section includes a table indicating effectiveness and selectivity of forestry-registered herbicides on different species of plants; recommendations for control of woody species, and recommendations for grass and herb control for planting and establishment. Herbicides will be listed by their common name (e.g. clopyralid or metsulfuron) so many readers will need to refer to Section C to find familiar trade names.

The Handbook is available in print but since it is revised annually, it is recommended to go on-line to refer to or download relevant sections.

Caution! The handbook is not intended as a complete guide to herbicide use. Before using any chemical, read the container’s label. A chemical must be thoroughly tested before it can be recommended for a specific use. Following the label’s recommendation can prevent many problems from arising due to wrong use of a chemical. Any use of a pesticide contrary to instructions on the printed label is illegal and is not recommended. Herbicide application is a forest operation requiring notification of ODF.


Calibrating and Using Backpack Sprayers

Backpack sprayers are relatively easy to use – and to misuse. This video (EM 9039)   and printable pdf of PNW 320 describe basic sprayers, their components and how to use them appropriately. It also outlines how to calibrate the sprayer, calculate application rates, and mix pesticides.


Preventing Herbicide Drift and Injury to Grapes  EM 8860   

Anyone using herbicides near a vineyard needs to understand the damaging effects that common herbicides can have on grapevines and steps you need to take to reduce the risk of herbicide drift and injury.

So good luck out there and please be smart and be careful in all your weed control efforts. Chemicals and power equipment each have dangers and justify judicious and cautious use, especially on rugged ground and sensitive areas.


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Spacing young conifer stands

Fri, 01/29/2016 - 11:26am

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

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 commercial thinning when the trees are in their mid 20s.  Since most people are hoping to do a commercial thinning on their way towards a variety of longer-term objectives and stand conditions, we need to focus on reaching that first commercial thinning 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 commercial thinning.

My contacts in the business around the mid-Valley tell me that while the first thinning 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 you are losing 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.

Roughly speaking, you need a stand with an average size of about 10 inches dbh (or bigger) to get this desired mix of products to have a profitable operation in recent market conditions ($475 to $500 per MBF).

So why are people having trouble achieving that? It has to do with how trees grow in stands.  Let’s review nature’s rules:

  • Bigger trees need to use more site resources (mainly light, water and nutrients) than little trees.
  • The resources available on any given site are limited.
  • As a group of trees grows, it reaches a point where there are not enough resources to go around and trees begin to compete, leading to winners and losers.
  • Eventually some trees have to die (the losers) for others (the winners) to have room to grow.

What’s neat is that there is a regular and reliable pattern to this process which applies generally to all species (when growing in groups of similar age). There is a predictable maximum number of trees of a given size that can grow together in a group.

So it follows that there is a predictable maximum average size for any given number of trees growing together in a group, according to its species.  As a group of trees grows towards its maximum size for that number (its spacing or density), it will pass through certain stages along the way.  These stages (e.g. crown closure) or zones (e.g. self-thinning) all correspond to different and increasing levels of competition among the trees, each occurring a  predictable point. See illustration below.




As covered before, the idea in spacing a young stand is to have the “right” number of well-distributed trees to allow them to grow until they are big enough to support a commercial thinning, and to be able to do it “on time”, before future opportunities are affected by overly-intense competition. This generally means aiming to thin the stand when it is in the Goldilocks zone (yellow or gold), and avoiding slipping into the self- thinning zone (red).  Bad things happen in the red zone. Trees start dying, starved to death for want of resources by excessive competition among their neighbors.  This is euphemistically called “self-thinning”.  Self-thinning is an entirely natural process that gradually allows room for surviving trees to grow larger.  But in the process live crowns get smaller, individual tree growth slows down and all the trees suffer.  If allowed to proceed too far (approaching the brown zone), the stand becomes  too weak and unstable to be thinned effectively.  That leaves few options besides letting the stand grow (and self-thin) for another decade or so until it can be clear cut, then start over.  This is not necessarily a bad decision, but not the outcome many family landowners are aiming for.

This relationship of predictable stages (commonly expressed as a ratio of the maximum) also gives us predictable average tree sizes at which different stages are reached. This lets us know if trees growing at any particular spacing will reach a given target, like the 10 inch average size needed for a commercial thinning, before becoming too crowded and stressed.


Let’s consider some young Douglas-fir stands.

Growing at the commonly planted spacing of 10×10 (about 440 tpa, the column on the right), trees will just be 6” (on average) when they enter the Goldilocks zone, and barely 8” when they are pushing up against the red zone. We saw why it is hard to have a profitable operation at that size.  But delaying the thinning operation is unlikely to fix the situation, since we won’t have reached even a  10” average before approaching the brown zone.  Generally many the trees we’d like to remove in an early thinning will be smaller than average.  A delay for any reason at this spacing is likely a big step towards a short rotation.



Trees planted and growing at an 11×11 spacing (360 tpa) may do a little better, growing into the Goldilocks zone at an average size of about 6½”, and reaching the red zone at about 8½”. Still shy of the thinning target while avoiding intense stress, but it might work for some people.


So what about a still wider spacing? Trees growing at a 12×12 (300 tpa) spacing have a lot more room to grow before crowding and competition begins to undermine other management objectives. At a 12×12 spacing trees will be about 7½”, when they fully occupy the site and 10″ on average when they approach the self-thinning red zone. It is much easier to see a profitable thinning operation in this type of stand, and less temptation to delay and push beyond the upper end of the desired thinning window. But should life or market conditions mandate a delay, this spacing gives a bit more breathing room. Other advantages of this stocking level include an earlier (if small) cash flow to offset some establishment costs, fewer, larger trees to handle in the thinning harvest, and a residual stand of deep-crowned, wind firm, rapidly growing trees which provides the landowner a wider range of silvicultural options.


Oh oh, so what if you planted at 10×10? Watch for an article soon on the nearly-forgotten practice of pre-commercial thinning (PCT).

The post Spacing young conifer stands appeared first on TreeTopics.

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Many young stands too crowded

Fri, 01/22/2016 - 4:40pm

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 do a commercial thinning (meaning sell the harvested trees to make at least a small profit) when their stand is about 25 years old.


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 thinning operation yet. 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 operation profitable is appealing. 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 commercial thinning, 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 first commercial thinning 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 commercial thinning while avoiding excessive competition. This will keep the most options open for the landowner in the future.
We’ll look at what that number might be in another article.

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Understanding vegetation in young plantations: It’s what they do

Wed, 01/13/2016 - 1:02pm

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


photo: VMRC

Last month I spent a morning at OSU attending the annual science meeting of the Vegetation Management Research Cooperative (VMRC). It was well worth the time.

The VMRC’s mission includes conducting applied reforestation research of young plantations from seedling establishment through crown closure and, to promote reforestation success. The VMRC’s research has an emphasis on practical, operational vegetation control, and their research is broadly relevant and readily applied to the needs of family forest landowners, so I do try to keep up on their work.

Since many of the member groups do use herbicides in their forest management, their research frequently does involve herbicides. But the work is not generally about herbicides per se, but rather about understanding the nature of weed competition and how different degrees of competition and disturbance affect seedling growth and vegetation community dynamics. They are interested in knowing the influence of the timing of competition control efforts on survival and growth, how the length and timing control each affects growth and survival (“critical period threshold”), or the interaction of different seedling stock types and vegetation control methods affects seedling growth and vegetation community dynamics. Good stuff to know.

The meeting was also a chance to meet the VMRC’s new Director and Associate Director, Dr Carlos Gonzalez-Benecke and Max Wightman. They kicked things off with an excellent summary of the past decade’s research conducted around western Oregon and southwest Washington. They also did some broader synthesis of results to help lead the coop forward in another decade of work.

The VMRC currently has 14 members including forestry companies, state and federal agencies. It is one of 11 research coops at OSU’s College of Forestry ( Each conducts research and applies the results to solve problems, develop new products, support long-term field studies, and develop decision support tools. A CoF faculty member leads each cooperative and members work together to develop a mutually agreeable research program, pool dues payments to support the cooperative’s operating budget, and provide significant in-kind support to leverage dues payments.

You may have seen my earlier posting on the Swiss Needle Cast Cooperative , and can expect to hear more about the work of the VMRC, SNCC and some of our other research coops in the future.

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Thirty years of private timber harvest trends in northwest Oregon

Thu, 12/31/2015 - 3:53pm

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

“What’s with all the logging going on?” is a comment I’ve heard more than once recently. Rural residents of northwest Oregon seem to be noticing an uptick in timber harvest from their industrial neighbors over the past year or so. I wondered whether these observations were simply anecdotal, or if they signaled a rebound from the recession, or if they were evidence of a more historic rise in harvest rates. So I decided to dig into some local data on recent forest ownership and harvest trends.

Forest land ownership by county. Source: OFRI

For this discussion, I focus only on harvest statistics on private lands – and I will further distinguish between private industrial (i.e. large timber companies) and private non-industrial (i.e. small woodlands, or family-owned forestlands). I looked at data for the three counties I work in.

Did you know that Columbia County ranks #1 among all Oregon counties in terms of the percentage of privately owned forest land? 94% of all the forestland in Columbia County is privately owned – with about two-thirds of that land owned by industry and one-third by small woodland owners. In both Washington and Yamhill Counties, roughly 70% of the forest land is privately owned with the balance in state or federal ownership; the private land is about 50/50 industry/small woodlands (plus a fraction in Yamhill County in tribal ownership). Across the three counties combined, forest industry owns 56% of the private forest land, small woodlands account for 43%, and the remaining 1% is in tribal ownership. These figures come from the Oregon Forest Resources Institute and can be found on the Know Your Forest website,

The data shown in the next chart come from the Oregon Department of Forestry and illustrate a few further points about timber harvest trends in this part of northwest Oregon.

First, and most obviously, we see that the vast majority of timber harvested in these counties is on industrial land. In any given year over the last thirty, industrial forest owners account for between 69 – 92% of the total private harvest volume, while the amount coming from small woodlands (NIP on the graph) is between 7 – 31%. Since forest industry owns only 56% of the private forest acres, we see that more volume per acre is harvested by the timber industry on an annual basis than by small woodland owners.

The data support some assumptions often made about small woodland owners; for instance, that they typically use less intensive harvest practices such as partial cuts or longer rotations than industry.  Some small woodland owners, especially those with the smallest acreages, do not harvest at all.  Another interpretation is that small woodland owners’ harvested acres tend to be less productive on a board-foot basis, in that they are less fully stocked or more dominated by non-commercial material.  A combination of all of the above is likely.

Second, we see that harvest rates fluctuate a lot year to year, but patterns are evident. Harvest volume dropped dramatically in the recession, and though it’s been rising rather steadily since then, it had not yet reached pre-recession levels by 2014. Small woodland owners, whose harvest behavior as a whole tend to be very price sensitive, were more affected by the recession – those were the years (2007-09) when they made up the smallest percentage (6-7%) of the total private harvest. And since the recession, small woodland owners’ harvest rates have rebounded more quickly than industrial rates. In fact, in 2013, a year of relatively high log prices, small woodland owners’ share of the three counties’ total private harvest reached 25%, a level not seen since 1993.

Finally, there have been some differences among the counties in terms of forest industry harvests, as the third chart shows. Specifically, in Columbia County industry harvests rose rather sharply in 2014, to the highest level in a decade, whereas industry harvests in Washington and Yamhill Counties dropped that year. Industry patterns are driven by many factors including changes in corporate ownership.  In 2013, the dominant industry owner in Columbia County, Longview Timber, was bought by Weyerhaeuser. Aggressive harvesting often follows a purchase in order to reduce the debt load incurred by the purchase.  Small woodland owners are really no different, in that often timber is harvested to finance the buyout of a family member.

Data for 2015 were not available at this writing. Given what we know about harvesting behavior, what might we predict? Log prices in 2015 were down overall from the year before. So, small woodland owners’ harvests might have dropped as well. On the industry side, the “uptick” noticed by many, noted at the beginning of this article may well play out in the data.

A final note: this analysis addresses only volume, and says nothing about value. Fortunately for small woodland owners, volume isn’t the end of the story. The practices espoused by many small woodland owners alluded to earlier (i.e. longer rotations) can lead to a higher value product, as long as there are markets for that wood.

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