Slow-growing ponderosa pines may have a better chance of surviving longer than fast-growing ones, especially considering climate change

New research from scientists at the University of Montana found that slow-growing ponderosa pines may have a better chance of surviving longer than fast-growing ones, especially as climate change increases the frequency and intensity of drought,

This new research is important because the timber industry and U.S. Forest Service often justify “thinning” in ponderosa pine forests on public lands to increase the growth rate and “restore” resilience. But what if in their zeal to “restore” the forest and increase the growth rate of the remaining ponderosa pines, the timber industry and Forest Service might actually be destroying the very forest they are trying to create?

As George Wuerthner (who has degrees in wildlife biology and botany, and has worked as a biologist for the federal government) wrote in an email when he shared this new research, “Here’s another example of how foresters are ignorant and damaging our forests when they suggest that they are thinning to ‘restore’ resilience. When they thin the forest they have no idea of the genetic make up of the trees. But some trees naturally grow slowly and are more resistant to drought. This has been documented in other species like lodgepole pine as well. Foresters with a paint gun have no idea which trees are genetically resistant to bark beetles, drought, cold, etc. but they often take out 50% of the trees in thinning projects. In their efforts to ‘restore’ the forest they may destroy it.”

According to the press release from the University of Montana:

The study, led by UM alumna Beth Roskilly and Professor Anna Sala, was published in the Proceedings of the National Academy of Sciences this week. The researchers sampled growth rates of ponderosa pine trees of varying ages at two remote sites in Idaho. They also studied structural traits of the trees’ xylem — vascular tissue that transports water and minerals through the wood and provides structural support.

Their findings reveal that some young trees grow quickly while others grow slowly. But old ponderosa pine trees — those older than 350 years — are slow growers compared to younger trees, and these individual trees have always been slow growing, even when they were young.

In contrast to predictions, slow-growing trees, whether old or young, did not produce denser, tougher wood, which might have made the trees more resistant to disease or decay. Instead, a key difference between fast and slow growers resides in a microscopic valve-like structure between the cells that transport water in the wood, called the pit membrane. The unique shape of this valve in slow-growing trees provides greater safety against drought, but it slows down water transport, limiting growth rate.

“Ponderosa pines, like people, cannot have it all,” said Roskilly, the paper’s lead author. “Drought resistance contributes to longevity but also to slow growth. In other words, there is a fundamental tradeoff based on xylem structure. Our study suggests that trees with fast growth become large quickly, which can be beneficial for young trees competing for resources, but they are more vulnerable to drought and can die at earlier ages. On the other hand, trees that grow slowly are more drought resistant, which enhances longevity.”

Roskilly earned her UM master’s degree in organismal biology, ecology and evolution in 2018, and the study is a result of her degree work in UM’s College of Humanities and Sciences.

“Ancient trees are special for many reasons,” said Sala, a professor in UM’s Division of Biological Sciences and an adjunct professor in the W.A. Franke College of Forestry and Conservation. “They are beautiful, they make the highest quality musical instruments, they help maintain diversity, and they store atmospheric carbon in wood for a long time. But the results of this research also suggest they are special because forest managers cannot make just any ponderosa pine tree live for centuries no matter how hard they try. For ponderosa pines to become centennials, their wood must possess this unique structure.”

21 thoughts on “Slow-growing ponderosa pines may have a better chance of surviving longer than fast-growing ones, especially considering climate change”

  1. Matthew, is this the same study? Because the abstract is so different from the press release, it’s hard to tell..

    Understanding life history trade-offs is important because they present limits to adaptation in organisms. Life history trade-offs are usually thought to result from resource allocation conflicts among multiple traits, but functional constraints based on individual morphological traits can also contribute. We show that a fundamental life history trade-off between growth and longevity in a conifer species is related to a single morphological trait in the xylem that has conflicting functional effects. Our results demonstrate that, in addition to resource allocation trade-offs among multiple traits, functional constraints based on individual morphological traits provide mechanistic insight into how and when life history trade-offs arise.

    Consistent with a ubiquitous life history trade-off, trees exhibit a negative relationship between growth and longevity both among and within species. However, the mechanistic basis of this life history trade-off is not well understood. In addition to resource allocation conflicts among multiple traits, functional conflicts arising from individual morphological traits may also contribute to life history trade-offs. We hypothesized that conflicting functional effects of xylem structural traits contribute to the growth-longevity trade-off in trees. We tested this hypothesis by examining the extent to which xylem morphological traits (i.e., wood density, tracheid diameters, and pit structure) relate to growth rates and longevity in two natural populations of the conifer species Pinus ponderosa. Hydraulic constraints arise as trees grow larger and xylem anatomical traits adjust to compensate. We disentangled the effects of size through ontogeny in individual trees and growth rates among trees on xylem traits by sampling each tree at multiple trunk diameters. We found that the oldest trees had slower lifetime growth rates compared with younger trees in the studied populations, indicating a growth-longevity trade-off. We further provide evidence that a single xylem trait, pit structure, with conflicting effects on xylem function (hydraulic safety and efficiency) relates to the growth-longevity trade-off in a conifer species. This study highlights that, in addition to trade-offs among multiple traits, functional constraints based on individual morphological traits like that of pit structure provide mechanistic insight into how and when life history trade-offs arise.

    • Sharon, Yes, as the information provided by the University of Montana clearly says at the bottom of the press release:

      Journal Reference:

      Beth Roskilly, Eric Keeling, Sharon Hood, Arnaud Giuggiola, Anna Sala. Conflicting functional effects of xylem pit structure relate to the growth-longevity trade-off in a conifer species. Proceedings of the National Academy of Sciences, 2019; 201900734 DOI: 10.1073/pnas.1900734116

      Is it unusual for scientists and researchers to use a different tone and words when writing an abstract for scientific publication versus providing quotes for a general press release? Certainly you are not allegeding that what was said by the scientistic experts in the official scientific paper differs greatly from what the same exact scientific experts said in the official press release.

      • Absolutely I am saying that.. there is a difference between what the study finds and what the authors claim it finds in the press release. I’m not saying that that’s unusual.

        • Sorry, Sharon, but I don’t believe what you are claiming is true. You are welcome to contact Dr. Anna Sala directly and tell her that she’s apparently making stuff up and/or lying. I also have just written Dr. Sala and told her to look at this blog post to read your allegation.

          • No I’m not saying anyone is making stuff up or lying. I am just saying that I think the abstract and the news release are very different. In my experience, more different than most of them we have run across on the blog. Why is this? I don’t think it’s because of Dr. Sala lying or making stuff up.

            • Ok, so you are changing your tune and tone on this it appears.

              Anyway, so are you claiming that the research of Dr. Anna Sala and others doesn’t support the statements made by Dr. Anna Sala and others in the press release?

              • No I am not changing my tune or tone (?). But I can’t compare what’s in the paper to the press release until I get a copy (I’ve written for one). So I’m waiting because I would bet a six pack that the paper is more nuanced in its conclusions.

              • But Dr. Anna Sala isn’t a “climate scientist” *smirk*

                Dr. Sala has a PhD in biology and is a professor within the University of Montana’s College of Forestry and Conservation, one of the top forestry schools in the nation. *smirk*

                • Obviously she knows how to tailor her conclusions to match her audience’s preferences. Studies are often ‘crafted’ to meet the funder’s narratives. Many studies are pretty worthless, in real world terms, not including variables that radically affect what they say in the conclusions.

                  In this particular study, the conclusions have no value in the real world of the Forest Service, and our forests. How much money was spent on this useless and contrived study? *smirk*

                  • Nobody has brought up anything in the actual study, or the press release, that points to anything other than the fact that some of you don’t like the findings.

            • I notice a lot of differences these days in university press releases vs. what is in the paper/abstract. Sometimes you have to dig deep into the paper to find the information that relates to the claims made in the press release – and then you find all of the caveats about those claims that is not included in the press release. I’ve learned to take the press releases with a grain of salt and read the paper if I really want to understand the research.

    • The press release and the abstract seem consistent to me. Different language has to be used for different audiences. What’s useful for someone with a doctorate in botany isn’t likely to be palatable to someone reading The Missoulian at the breakfast table.

      I am struck by the vituperation in this thread that’s coming from two guys. Bad environmental news is everywhere. Just today I read an alarming Wall Street Journal article on insect-species declines and listened to an alarming Canadian Broadcasting Corporation from a First Nations chief in Old Crow, Yukon, about the effects of climate change on Canada’s northwesternmost settlement. (Link below; forward to 2:35 in the audio clip.) The Wall Street Journal had an article yesterday on how we could greatly lower the U.S.’s electricity-generation carbon footprint, except that three U.S. senators and an ancient Arkansas law are blocking the initiative. It’s quite maddening.

      With all of this, it seems wasteful to wrangle on this topic. I could complain about George Wuerthner, the deep ecologist who is mentioned here. He regularly posts voluminous screeds about the evils of mountain biking to whatever audience reads The Wildlife News. But why take up the time? With regard to tree-thinning, he might even be right.

      • I don’t think he’s right about thinning, though… why? about 40 years ago, people were interested in selecting trees for superior growth, rust resistance and so on. There’s a great body of literature on how to do that, and how poorly it works in practice. Unfortunately, I’m away from home right now and don’t have access to paper copies of my work from the 80’s.

        But when I find them I’ll post on it. It’s kind of interesting from a history of science perspective as well- the things people used to study and how they used to study them and how they stop studying them and people forget the info was ever known…

  2. In a pine-dominated forest, the slower growing ones are shaded-out and left behind to wither and die. No, they don’t ‘release’ very often because they will die before an opening appears. There’s also that certainty of wildfires, in a world full of human realities.

    As a person who has ‘selected’ many trees with a paintgun, spacing and health are way more of a selection criteria than imagined genetic tendencies. There are very few characteristics to compare to other trees, and you cannot write impossible predictions into a silvicultural prescription that Temporary Employees can implement.

    Pretending that the Forest Service will adopt a hands-off approach because of Wuerthner is just not rational or helpful. When 300 years old pines are dying, right and left, that indicates additional problems that weren’t included in the study.

    • Again, this is not at all a claim that the actual study made. Larry is making one of his typical strawman arguments here.


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