New OSU Study on Thinning and Prescribed Burning in the Blue Mountains

This OSU study by Johnston et al. is interesting because it suggests that mechanical thinning can be useful in reducing without follow-up prescribed burning, at least for a while, at least in NE Oregon.

Mechanical thinning alone can calm the intensity of future wildfires for many years, and prescribed burns lengthen thinning’s effectiveness, according to Oregon State University research involving a seasonally dry ponderosa pine forest in northeastern Oregon.

Findings of the study, led by OSU research associate James Johnston and published in Forest Ecology and Management, are important because reducing accumulated fuels on federal forestland has been a congressional priority for nearly two decades; research such as this helps determine which techniques work.

Johnston’s team looked at years of data for multiple forest parcels – mechanically thinned stands and unthinned control stands – and used computer modeling to predict the behavior of future fires. The collaboration included his Oregon State College of Forestry colleagues Julia Olszewski, Becky Miller and Micah Schmidt, plus Lisa Ellsworth of the OSU College of Agricultural Sciences and Michael Vernon of Blue Mountains Forest Partners.

“Most of the studies that have been published so far suggest mechanical thinning that isn’t followed by prescribed fire is not as good for moderating fire severity than thinning combined with prescribed fire,” Johnston said. “Some studies have even suggested that thinning without prescribed fire can increase wildfire severity by adding to the buildup of fine fuels on the forest floor.”

Mechanical thinning refers to the use of commercial equipment such as a feller-buncher, which cuts and stacks whole trees, or a cut-to-length harvester and forwarder that results in logs of specific lengths being sent to the mill. In the study areas, all trees up to 53 centimeters in diameter at breast height were removed, and hand crews cut down trees too small for commercial use.

“Our work shows that mechanical thinning can moderate fire behavior even in the absence of prescribed fire,” Johnston said. “That’s good news since prescribed fire on national forests has remained flat over the last 20 years because of shortfalls in U.S. Forest Service capacity, a risk-averse agency culture and regulatory constraints on smoke.”

I guess I always thought “mechanical thinning” was cutting trees and removing them however you wanted, including hand piling and burning.
It’s interesting what Johnston ascribes the difficulties with PB to a “risk-averse agency culture” later he adds a few:

“Less than one-fifth of the area treated with mechanical thinning in the southern Blues has also been treated with prescribed fire,” Johnston said. “Prescribed fire has been significantly slowed by budget constraints, local opposition to fire use, and restrictions imposed by COVID-19 response measures.”

21 thoughts on “New OSU Study on Thinning and Prescribed Burning in the Blue Mountains”

  1. I was doing this in the 1980’s in the Blue Mountains; of course it moderated fire behavior! That’s what we done back then, managed the Forests….

  2. In addition to the mechanical work, the treatments included machine- or hand-piling and burning all non-commercial material. The PR material should note this fact.

    It is also important to mention this management implication stated by the authors from the discussion:

    “We do not assume that mechanical thinning in the absence of prescribed fire will moderate fire behavior for many years following thinning across the southern Blue Mountains or at other sites across the western U.S. Our study area was a relatively low productivity site near the edge of the range of ponderosa pine with significant evapotranspirative demands on trees, particularly seedlings.”

    • In non -academic words that means… if woody material doesn’t grow back ( or it does so slowly) then the effect of removing fuel will last longer. And that is true for many ponderosa sites throughout the west.

      • Yes, but this caveat is important. These sites have low productivity, even for PIPO. In contrast, the shrub and seedling response and fuel loading in general on the west side of Sierra Nevada and the Klamath is often quite dramatic. This is not to say that thinning alone is not effective in modifying fire behavior on productive sites in the Sierra or Klamath, it’s just to say that burning is more important in some places for treatment longevity and treatment effectiveness. Not to mention, low and moderate severity burning alone also works!

        The site index of the study locations is so low that a commercial harvest is unlikely to be an option for fuels retreatment for more than 50 years. The only options left will be Rx burning, mastication, or hand cut pile burn. The agency needs to figure out how to get an order of magnitude more burning done than it currently does, as it is not possible to use commercial harvest as a permanent replacement for ecological burning. In all the forests I have worked, the fuels accumulate faster than the MBF.

        • Yes, Ben, I’ve worked both on the south Central Oregon forests and on the Eldorado in the silviculture/reforestation biz. I get that they’re different. My point is that there are lots of the western US where ponderosa has low productivity, I’m thinking here, Colorado, New Mexico and so on.. and for a variety of reasons, “commercial harvest” as thought of currently may not be an option ever. That’s why many of these areas are more interested than perhaps Oregonians in alternatives for small material.

          I guess my basic point is there’s lots of ponderosa that’s not in Oregon nor California.

          • I’ve have also worked in PIPO forests where commercial harvest is rarely possible due to low productivity and/or lack of a market. I get that this area is not the Eldorado. The way I read the PR, it seemed like it was being framed that we don’t need fire, we can log. My basic point was that not getting enough good fire on the ground remains a paramount concern and we are not logging our way out of this on any acre.

            • I think what they framed it as was “if for some reason you find you can’t do PB, thinning will still get you something in the Blue Mountains.”

              As to “any acre” I happen to live in a forest area where we have plenty of thinning and no pb because of residences. Many other places along the Front Range of Colorado are the same. So I would be happy to know that thinning will do something without pb, but unfortunately the study wasn’t done here.

        • Of course, it is all about site-specific conditions. I think that timber volume should be more of a side effect to restoration treatments. Matching tree densities to annual precipitation levels is more important than volume numbers. Adjusting species compositions to a more resilient mix is always a good thing. In eastern Oregon, aspect seems to be the biggest factor in what grows on the ground.

  3. The thinning projects I worked on didn’t require the loggers to cut undersized trees, unless they are “damaged beyond recovery”. Some of those small trees get knocked over from ‘harvesting’ or skidding. The larger trees are bucked and limbed as normal, with any slash concentrations scattered. (That may have changed in the last 15 years.)

    • Things *have* changed a bit in the last 15 years, Larry; and even before that. In particular, because of fire suppression and high grade logging, there are far more small trees than large trees, and they can’t simply be “knocked over” during other harvest activities – indeed, they proliferate across the landscape. Most restoration work in the Blues focuses on removing these smaller diameter trees, retaining large old trees, and restoring fire to the landscape. Scattering slash can be done in places, but given the high fuel loads that result from thinning, slash is usually burned.

      • I was talking about trees under 9.9 inches in diameter. In the Sierra Nevada, those trees aren’t included in the contract, unless it is within an appropriately-aged plantation. Usually, sub-merchantable material is associated with a service contract. Additionally, there is no high-grading in those Sierra Nevada National Forests. Again, all smaller merchantable trees are skid to the landings with limbs and tops still attached. I guess Oregon thinning projects deal with slash the prior-millennium olde-fashioned way, eh?

  4. In his study, my colleague James “used computer modeling to predict the behavior of future fires.” Ouch. While I acknowledge it’s tough to do ecological research, I much prefer real-world measures of fire behavior over model predictions when measuring the effects of silvicultural practices.

    • Andy, I know you know that Dr. Johnston has spent – and continues to spend – years in the field gathering the data that goes into those computer models (see the image that accompanies the story). Predictions are just that: “estimates that (a specified thing) will happen in the future or will be a consequence of something.” Provided that there is “real” and “good” data that goes into those models, the results are highly relevant. And, when there is post-implementation monitoring (i.e., “real-world measures”) – which is occurring here – verification of those predicted results further solidify the likelihood that the prediction is correct.

      And yes, I agree “garbage in, garbage out” when it comes to models; but I don’t think that’s an issue here 🙂

    • Other than the crown fire experiments in the early 90s where have used actual measures of intensity of wildfire burning under wildfire conditions?

      • Measuring intensity during a fire is unusual, as you note, because it’s tough logistically. Measuring effects after a fire is common and easy; which is what I was referring to.

  5. I have no objection to the findings of this study, but creates a false impression that logging is a great solution without addressing all the complicating factors:
    – the fact that most fires are weather/climate driven, not fuel driven;
    – the low probably that fuel treatments will interact with wildfire before fuels regrow;
    – the modest effect of fuel reduction on fire size and fire severity;
    – the fact that in many cases mature forest is more resilient than logged sites. Removing canopy trees can make fire hazard worse instead of better by creating warmer/drier/windier microclimate, generating more hazardous slash; stimulating the growth of surface and ladder fuels; and increasing roads that increase ignition risk;
    – relying on commercial logging to pay for fuel reduction results in less effective fuel reduction and greater ecological trade-offs: soil, water, wildlife, snags, carbon, etc. The majority of stands that need fuel treatment the most do not support viable timber sales. Commercial logging is the most effective fuel reduction strategy in only a small fraction of situations. The FS tends to choose fuel reduction locations based on timber sale viability, rather than highest need.
    – To achieve community fire safety, the most effective fuel reduction actions are located within 100 feet of homes;
    – The majority of wildfires are still burning with a characteristic (and ecologically appropriate) mix of low, moderate, and high severity. The effects of wildfire are often more ecologically beneficial than the effects of logging alone, or logging followed by wildfire;

    • 2nd you keep making statements like this as “complicating factors” or “facts” but they are actually (highly) contested observations, based on different sources of information. You also mention the “characteristic mix” of low moderate and high severity being “ecologically appropriate”. Seems to me you need to pick a specific time and place for what might have been “characteristic”, e.g. Native American burning.. before they were here? But they’ve been here since previous climate changes.. so ?? It doesn’t seem to me that there is a good rationale for picking one time period, the mix of severities, and claim that particular one is “ecologically appropriate” and others aren’t.

  6. 2ndLaw: Are you serious? You are clearly confusing your personal opinions with facts. There is no way to do this and present a reasonable argument. Instead, you are showing your obvious biases and providing an insight as to why you choose to express your apparent thoughts behind a pseudonym. That’s how trolls operate and why it is difficult to take your statements seriously — or even bother to read them. What are you hiding from? Why do you seem so certain about your beliefs, yet are unwilling to personally back them up? So much for credibility. Also, I disagree with the majority of your statements, but you give me no reason to state why.

    • It’s not exactly very ‘new’. I worked with those same machines in a crowded post-fire plantation in the summer of 2000. Yes, they are remarkable, and part of a system that minimizes the amount of employees needed to get the job done. The harvesters bunch the logs and the forwarder transports them to empty trailers on the road. The forwarder loads up the trailers with logs and the truck drivers drops off his empty and picks up a full one. Two pairs of loggers and a number of truck drivers can get a lot of work done.


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