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Preparing for thinning

TreeTopics - Thu, 08/17/2017 - 5:33pm

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

This will be a cut-to-length project. A processor will travel corridors through the stand, reaching in and cutting selected trees, limbing and bucking them all in one process. There are many advantages to this type of harvest system. For example, the machinery travels over the bed of slash it produces, minimizing soil disturbance.  Also, cut-to-length is efficient in terms of time, labor and precision cutting of the logs to maximize scaling. Some of the disadvantages are that it requires advance planning, there are relatively few operators often booked out far in advance, and the fixed costs are relatively high.

Here’s a video of one type of cut-to-length machine working.

At Matteson, we will be treating about 29 acres of Douglas-fir plantation about 30 years old. Because of our education and demonstration mission, we will implement several different prescriptions in different treatment areas across the acreage, for comparison.

Getting some numbers

The first thing we needed to develop our thinning plan was some stand data. We have installed a network of 0.1-acre permanent inventory plots across the property, and eleven of those plots fall in the area to be thinned.

The plot data showed that on average, the stand density is about 250 trees/acre and most trees are between 9 and 14 inches DBH.  Putting each plot on a density table, we see that most of the stand is in the “Danger Zone” meaning that it is too dense. Ideally, thinning should have been done a few years ago.

This diagram shows how stand density, tree size, and competition interact. For an explanation of the different competition zones, see a previous post. Each blue diamond represents one of the inventory plots in the stand to be thinned. Diagram credit: B. Withrow-Robinson

Aside from the numbers, visual cues tell us that the stand is in the Danger Zone. There is very little vegetation on the ground, the trees’ live crowns are receding to around 1/3 of the total tree height, and there is scattered competition-induced mortality.

Developing prescriptions

Our objectives with the thinning are to produce income, improve stand health, and set the stand up to produce high quality timber in the future. We also want to show how thinning can be implemented in different ways, to achieve different objectives.

Over most of the unit, we chose a “future pole” thinning prescription.  Poles have high value, but trees must meet exacting specifications. In essence, this treatment involves cutting trees that will never make a pole because of defects such as spike knots, double tops, or too much sway in the trunk. Any tree that has pole potential (straight, few knots, etc.) will be left, regardless of crown class. If this prescription results in areas that are still too dense, then those areas will be thinned from below; if it would leave areas too sparse, then in those areas some non-pole trees will be left.

In this sample marked area, the painted trees are to be cut.

We set aside a few demonstration areas for other prescriptions.  We’re still working out the specifics of these alternatives, but we have a few ideas we are working with. One is a standard thin from below, removing the smallest/most defective and leaving the remaining trees as evenly distributed as possible. For example, out of each group of four trees two would be cut. This would remove half of the trees (but only about a third of the volume) and leave the remaining trees with plenty of room to grow. I estimate that most of the stand would move to the “Lower Goldilocks” zone under this scenario (not too dense, not too open, “just right”: see above table). However, one of the concerns about thinning an overly dense stand is that the trees left behind are unstable when too many of their neighbors are cut. So if we wanted to be more conservative and do a lighter thin, we could cut two of every five in the same way. But, this would be less profitable and also mean that the stand would close up again very soon.

Either of these prescriptions would be easy for us to mark and for the operator to follow. However, they perpetuate a uniform, plantation-style stand with low structural diversity. What if we wanted to mix it up? One idea is to thin from below with a diameter limit: cut anything 11” DBH and smaller, and leave anything 12” DBH and larger. Exceptions to the rule could be made, for example if a 12” tree has a defect and an 11” tree next to it has good form, the 12” tree would be cut and the 11” tree would be kept. Because this prescription is based on tree size rather than spacing, we’re expecting it would result in a patchier arrangement of leave trees that would still have plenty of room to grow.

Going further, we could do a “structural diversity makeover” thin, to demonstrate a way to actively move a uniform plantation to a more diverse forest. We could thin from below across most of this area, but then cut all the trees in a few gaps, to encourage understory vegetation or even tree regeneration. We could even strategically place these gaps in places where there is already a hardwood shrub or two. Because the processor needs to cut 12-foot corridors to travel through, and can reach in 30 feet on either side, we could also place our gaps along the corridors. Finally, we can create snags, by marking trees for the processor to cut up high – like 15 to 20 feet up. Trees with a defect in the lower bole would make good candidates for created snags.

Finally, a couple small areas won’t be thinned at all, just to demonstrate how that plays out. One of these surrounds an old piece of farm machinery left from one of the homesteads that were on the property. Because this is considered a cultural resource, we want to avoid disturbing the site, so putting our unthinned area around it makes sense.

Blending science and art

It’s often said that silviculture is a blend of science and art. We can look at data and design prescriptions on paper, but ultimately conditions in the stand will also influence what we do. And that is where marking the stand comes in. It’s very time consuming to mark an entire large stand, so the Research Forests crew marked some sample areas of the “future pole” prescription. The contractor will work in these areas first to get a feel for the prescription, then move to unmarked areas. For more complex prescriptions, such as the “structural diversity makeover”, we will probably mark the whole demonstration area (each one less than an acre).

What do you think of these thinning scenarios? Is there something else you would like to see?

The post Preparing for thinning appeared first on TreeTopics.

Categories: TreeTopics

Growing a Diverse Forest and Making Money: How Some Small Woodland Owners Do It

TreeTopics - Wed, 06/28/2017 - 8:20am

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

Lately on this blog we’ve been discussing ways to grow a diverse forest.  Many small woodland owners are interested in maintaining diversity on their land, yet strive to do it in a way that also brings in income from timber or other means. For these reasons, I was intrigued by the work of Julian Geisel, who recently wrapped up his master’s degree in the College of Forestry at OSU. His research topic, “Management Strategies for Small, Income Generating and Structurally Diverse Forests” is particularly relevant to small woodland owners. Julian’s research focused on private woodlands in western Oregon, representative of the vast majority of the owners that we work with in Extension. I interviewed Julian about his work.


Julian Geisel, former OSU graduate student

What question did you set out to explore through your research?

I wanted to know what strategies help make it possible to generate income while maintaining or improving structural diversity on a small-scale forest. Most small woodland owners want or need to produce income from their property. Society values forest diversity, and so do many woodland owners, but many believe it’s not possible to maintain without sacrificing income. However, some woodland owners have been successful at it, and so I wanted to know if there were specific strategies or things they had in common, that other woodland owners could apply.


What methods did you use to accomplish this?

I conducted extensive interviews with six owners with between 25 – 150 acres in the Willamette Valley. These owners all had stated income generation and maintaining diversity as goals in their management plans. In the interviews, we discussed their management philosophy, successes and challenges they had in achieving their management goals, and resources or people that they relied upon. I used these interviews to look for patterns and evidence, and to validate my interpretation, I had another student independently review all the interview transcripts.

In addition, I did field assessments to try to quantify the extent to which these owners’ forests were structurally diverse. I looked at features of the overstory, understory, ground cover, and dead wood, for example. Then, I reviewed each landowner’s records to evaluate how much income they were producing. Finally, after doing all of this work and coming up with my own theories and ideas, I went back to each landowner for a second interview to confirm that my interpretations of what they said were correct.


How did the woodland owners that you interviewed describe structural diversity on their property, and why was this type of management important to them?

Structurally diverse forest in Linn County

Well, structural diversity is sort of a technical term. Some talked about it in terms of having habitat, or areas for wildlife. Some described their property as being more “natural”, and others simply recognized diversity across the landscape; i.e. their property is different from their neighbors’ and that in itself created diversity. Their motivations varied, but included the desire to maintain a functioning ecosystem, reducing pest risk, having more options for selling timber, or simply wanting to do what they felt was best for the land.

Among the landowners, I found a continuum between those that were more income-driven, and those that were very passionate about the concept of diversity, but all of them incorporated some of both into the management of their forest. Some did not think there had to be a tradeoff between the two, some created diversity or income without necessarily intending to in the process of reaching another goal.


How did these owners make money from their forestland?

Some of the income generation strategies included: selling timber, selling specialty wood, renting out a residence on the property, leasing other parts of the property for grazing, selling firewood or boughs, and providing timber management services or equipment for other landowners.  Sometimes owners would reinvest the profit from a one-time timber sale into a different type of asset that would provide a more regular cash flow.

Also important were strategies to save money, such as using firewood, construction materials and residential water from one’s own land; sharing resources with other woodland owners; keeping forest operations small and manageable so that the owners could do it themselves instead of hiring out; and learning how best to navigate the tax system.

Finally, owners emphasized the secondary benefits their forests provided, that had indirect value to them, such as mental health, stress reduction, physical fitness, and recreation.


What are the challenges to achieving structural diversity and income generation on a small acreage?

Scale is a problem. Landowners said that setting aside areas as ecological “preserves” is difficult when there are fewer acres to work with. All acres need to contribute to both income and diversity goals on very small properties Additionally, landowners recognized that there are many external factors influencing their forest that are both complex to understand, and hard to control – such as markets, tax systems, and regulations. These things, if not taken into proper consideration, can impinge on their goals.


If one were interested in balancing income generation and structural diversity, what seem to be the most important strategies to be successful?

Everyone mentioned that learning is a lifelong and continuous process. They combined learning by doing, and observing nature with listening to other people’s accounts during classes or by reading up on topics. Having mentors such as family members or neighbors and conducting little documented experiments characterized even more sophisticated managers.

Integrating their actions to achieve multiple goals is another important strategy. The landowners said that without much additional effort, by making small tweaks to their management they could produce income while maintaining or improving forest diversity, or vice versa. One memorable example was thinning plantations and leaving head-high snags. This action increased future income, created snags and made falling trees a little easier and faster.

Cultivating trusting relationships with others seem to be crucial. Forest management yielded successes quicker as a joint effort. So in the end, it’s not about the trees, it’s about people.


Congratulations to Julian on successful completion of his degree.  He plans to post more information about his project at his website, 

The post Growing a Diverse Forest and Making Money: How Some Small Woodland Owners Do It appeared first on TreeTopics.

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