Thinning increases forest resiliency

This open-access paper provides more science that supports thinning projects. As important as the findings are, it’s common sense that thinning is a positive: Fewer trees competing for water = more water in soils and watersheds. Granted, this study looked at conditions during an unprecedented drought in 2021. The principles apply during average summers, too, in arid regions. What’s more, thinning reduces competition for light and nutrients.


Regional droughts are now widespread and are projected to further increase. Semi-arid ponderosa pine forests across the western USA, which occupy > 56 million ha, are experiencing unprecedented levels of drought due to the currently ongoing North American megadrought. Using unpiloted aerial vehicle (UAV) thermal images and ground-based hyperspectral data, here we show that ponderosa pine forest canopy temperatures increased during the 2021 summer drought up to 34.6 °C, far above a typical canopy temperature when ponderosa pine trees no longer uptake carbon. We infer that much of the western US ponderosa pine forests likely served as a net carbon source rather than a sink during the 2021 summer drought period. We also demonstrate that regional forest restoration thinning significantly reduced the drought impacts. Thinned ponderosa pine forests had significantly lower increase in canopy temperature and canopy water stress during the drought period compared to the non-thinned forest stands. Furthermore, our extensive soil moisture network data indicate that available soil moisture in the thinned forest was significantly greater at all soil depths of 25 cm, 50 cm, and 100 cm compared to the non-thinned forest, where soil moisture dry-down in the spring started significantly earlier and stayed dry for one month longer causing critical water stress for trees. Forest restoration thinning benefits that are otherwise unappreciated during average precipitation years are significantly amplified during unprecedented drought periods.

17 thoughts on “Thinning increases forest resiliency”

  1. Thanks for sharing this paper. It continues to amaze me how poorly understood the “drought monitor” is. There are several webinars going on right now (and they have been recorded) about how the Drought Monitor is developed and what it is based on. It is not simply a measure of ecological drought – but many people treat it like that is what it measures.

    • Anonymous, if I recall correctly, the IPCC AR6 had three different drought measures. Please send any links to recordings about drought measures, or would you be willing to write a blog post on what you have learned? It’s quite puzzling to me.

  2. That’s a pretty broad brush you’re painting with Mr. Willent. There’s all different types of thinnings… And all the rhizopsheric science point to underground mycelial networks working with the trees to conserve / share water and other resources rather than “compete” for them.

    Furthermore, opening up the canopy to too much sun will deplete way more water to evaporation than trees, which have the physiological ability to shut down evapotranspiration during the hottest driest parts of the day.

    And yes thinning/branch pruning is a a good way to prevent trees from dying due to being shaded out, but much like the guy at the gym on steroids with huge muscles, too much tree growth from too much sun is unhealthy even if it looks impressive.

    In much the same way climate studies have found that trees growing on the forest edge are overexposed and fueling much more rapid growth which has negative impacts on the soils and causes those areas to emitting more carbon than they sequester compared to interior close canopy forests where water and carbon is more efficiently conserve in a more stable and natural system that sequesters more carbon than it emits.

    Therefore, certain types of overly aggressive thinning that turns the whole forest into forest edges is alot like that unhealthy roid-raged dude at the gym who will have lots of unexpected health issues in his future.

      • Firstly, Mr. Wilent, no painter has ever held a job longer than a day if they told their co-workers they only need one width of brush with which to paint. But if you’re a logger and your chainsaw is not quite big enough…

        Secondly, I’ve clarified to you multiple times for two years that you’re misgendering me and that my name is “Dean” with an ‘e’ on the end and I am a man and I’m six feet tall and 200 pounds of muscle and never back down to bullies because I do hard core physical exercise moving mountains with hard labor everyday pruning, gardening and forestry with hand tools, rather than sitting on my but inside a piece of planet destroying heavy equipment all day.

        Furthermore, if you lived in any other country in the world than the US you’d have to be fluent in more than one language and you’d understand the ‘e’ at the end of my name as nothing to be presumptive about. You’d also be far more open-minded to the perspective of not knowing what other people are saying because we’re always learning other languages so you could meaningfully connect rather than assume you have it all figured out in oppressing everyone around you in anti-social ways.

        All that being said, do you want to actually have a well referenced intelligent discussion about the entire spectrum of thinning prescriptions that includes the side of the spectrum that’s harmful versus the other side of the spectrum that’s relatively benign and sometimes beneficial? Or does your monomaniacal focus not allow for understanding the entire silvicultural spectrum/nuance?

        Because if misgendering me is your way of ending the discussion and not posting my comment, maybe we’ll have to escalate your oppressive urges in ways that will be far more unpleasant to you?

    • Deane, when I read about “overly aggressive thinning” I think of the scientists to your south, in the Sierra, who have found that historically stands were much more open due to burning by Native Americans. More open than people are comfortable with today. They would probably all look like edges to you.

      I don’t know if you were around for discussions of “forest health” and “ecosystem health.” I can summarize by saying that in the natural world “health” is in the eye of the beholder. Even if we think of just a few wildlife species.. conditions best for one are not necessarily better for another.

      It’s true that interventions sometimes produce unexpected and undesirable results. It’s also true that not-intervening by not-doing fire suppression is not a realistic choice. Also that the forests we have after 100 years of fire suppression are not the ones we might have had (nor after 100 years of removing Native Americans from the landscape.) Then there’s climate change, to which organisms/species respond to behaviorally and genetically, but not “the forest” as a whole.

      As a result, I don’t think we know the very best things to do right now for our communities and our forests. Time will tell what works and what doesn’t, and that has always been the case.

      • Same old rhetorical gimmick from you and all the others on here Sharron.

        Any time someone offer alternatives to limit fine fuels and soils drying out and wind penetrating deeper into the forest from too much thinning which combines to make wildfires way more destructive…

        Any time someone even simply asks for a rational discussion about about the entire spectrum of silvicultural thinnings from too much thinning on one end and no thinning on the other end…

        The response is always an irrational hair on fire approach about how some forests (usually Ponderosa) are overly dense and we’re evil for telling everyone we should do nothing. We rarely suggest doing nothing, but when you’re blinded by domga that’s the canned response you make so you don’t actually have to think about the advancement of science as well as where on the spectrum forest thinning shift from beneficial to destructive when a wildfire hits.

        It’s like getting an RX prescription of opiates to manage pain without any dosage advice on the bottle and when someone questions the spectrum of dosage based on your pain levels you act like someone is going to take all you pain pills away and you’ll have to do without.

        It’s totally irrational and it’s get really old and so incredibly dim-witted and unsophisticated compared to many, many new studies as well as actual on the ground knowledge about how logging makes wildfire more severe not less severe.

        And yet again, where are your references? Do you really think you’re going to keep your lies accepted as truth inperpetuity when you fail to reference or update with new references when it comes to all your ancient outdated research papers that are so old you don’t even reference them anymore and resort to vague dogma rather than the advancement of actual science?

        There’s plenty of science out there that proves you wrong Sharon. Like these two papers that are the latest that I just added to my collection today:

        Forest Harvest Can Increase Subsequent Forest Fire Severity by Carter Stone, Andrew Hudak, Penelope Morgan:

        Does increased forest protection correspond to higher fire severity in frequent- fire forests of the western United States?

        • In your desire to have an “rational discussion,” Deane, it’s important too remember that “it takes two to tango.” Your incessant name-calling, belittling, inaccurate statements, and rudimentary knowledge of forest management makes it difficult to take your rants seriously. Someone here suggested you start your own blog, if that is your idea of a “rational discussion.” But maybe it’s you that is too “dimwitted” to take a hint or form an intelligent statement. Just saying. Using your words.

  3. Ponderosa pine sucks billions of gallons from aquifer recharges, needles absorb heat and accelerate snow melt while aspen leaves reflect sunlight in the summer months and hold snowpacks in winter. Insects like the mountain pine beetle and spruce bud worm can help promote drought- and fire-tolerant species like aspen.

    Overstory removal can work because conscientious land managers have learned that where fire is introduced after mechanical harvest emerging aspen and other hardwoods add the biodiversity necessary to sustain healthy ecosystems while sequestering carbon.

    • Larry, just because you removed pondos doesn’t mean aspen or other hardwoods will grow back.
      What have you got against ponderosas?

    • Totally irrational and unreferenced BS Larry… Please provide valid references if you want to be taken seriously.

  4. Turpentine distilled from the California pines such as Ponderosa Pine (Pinus ponderosa) and Gray Pine (Pinus sabiniana) yield a form of turpentine that is almost pure heptane. When producing chemical wood pulp from pines or other coniferous trees with the Kraft process, turpentine is collected as a byproduct. Often it is burned at the mill for energy production. The average yield of crude turpentine is 5–10 kg/t pulp. In 1946, Soichiro Honda used turpentine as a fuel for the first Honda motorcycles as gasoline was almost totally unavailable following World War II.

  5. Yup. Thinning is part of producing healthy trees – within a niche- depauperate, species depauperate forest. (Hint, the forest is much more than just a few species of trees.)


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