Trees – Not adjusting to climate change

November 4, 2011


DURHAM, N.C., Oct. 31 (UPI) — More than half of tree species in eastern U.S. forests aren’t adapting to climate change as quickly or consistently as predicted, researchers said.

Nearly 59 percent of the species examined in a study by Duke University researchers showed signs that their geographic ranges are contracting from both the north and south, a Duke release said Monday.

“Many models have suggested that trees will migrate rapidly to higher latitudes and elevations in response to warming temperatures, but evidence for a consistent, climate-driven northward migration is essentially absent in this large analysis,” James S. Clark, a professor of environment, said.

Fewer species — only about 21 percent — appeared to be shifting northward than predicted, the researchers said.

“Warm zones have shifted northward by up to 100 kilometers (62 miles) in some parts of the eastern United States, but our results do not inspire confidence that tree populations are tracking those changes,” Clark said.


20 Responses to “Trees – Not adjusting to climate change”

  1. daveburton Says:

    Here’s the good news


    “The results of a 12-year study at an experimental forest in northeastern Wisconsin challenge several long-held assumptions about how future forests will respond to the rising levels of atmospheric carbon dioxide blamed for human-caused climate change, said University of Michigan microbial ecologist Donald Zak, lead author of a paper published online this week in Ecology Letters.

    trees bathed in elevated carbon dioxide continued to grow at an accelerated rate throughout the 12-year experiment.

    In the final three years of the study, the CO2-soaked trees grew 26 percent more than those exposed to normal levels of carbon dioxide. It appears that the extra carbon dioxide allowed trees to grow more small roots and “forage” more successfully for nitrogen in the soil, Zak said. At the same time, the rate at which microorganisms released nitrogen back to the soil, as fallen leaves and branches decayed, increased.

    “The greater growth has been sustained by an acceleration, rather than a slowing down, of soil nitrogen cycling,” Zak said. “Under elevated carbon dioxide, the trees did a better job of getting nitrogen out of the soil, and there was more of it for plants to use.”

    Ground-level ozone is known to damage plant tissues and interfere with photosynthesis. Conventional wisdom has held that in the future, increasing levels of ozone would constrain the degree to which rising levels of carbon dioxide would promote tree growth, canceling out some of a forest’s ability to buffer projected climate warming.

    In the first few years of the Rhinelander experiment, that’s exactly what was observed. Trees exposed to elevated levels of ozone did not grow as fast as other trees. But by the end of study, ozone had no effect at all on forest productivity.

    “What happened is that ozone-tolerant species and genotypes in our experiment more or less took up the slack left behind by those who were negatively affected, and that’s called compensatory growth,” Zak said. The same thing happened with growth under elevated carbon dioxide, under which some genotypes and species fared better than others.

    • daveburton Says:

      Unfortunately, the UofM paper is paywalled, but here’s the abstract:

    • daveburton Says:

      Imagine if we were anticipating a climate change that could be expected to reduce plant growth rates substantially, world-wide. Imagine if it were known to be a 21% growth reduction for trees, and probably similar amounts for other plants. The prospect would be universally & correctly considered to be an enormous disaster.

      Well, that’s the zero-CO2-growth scenario. 1 – (100%/126%) = 21%. So if we want to avoid that disaster we’d better not curb CO2 emissions!

      • greenman3610 Says:

        we’ll look for the accelerated plant productivity in Texas this year.

        • daveburton Says:

          Actually, greenman, one of the recognized benefits of increased CO2 is increased drought tolerance. With higher CO2 levels, plants can get by with fewer stoma and less respiration, leading to reduced water loss.

          • greenman3610 Says:

            Well, there you go. What are those dumb ass farmers complaining about?
            Obviously they just want more government subsidies.

            Honestly I read some of the dumbest damn statements in these comments, but you’ve set a new bar right here.

    • Gorbin Wafflemunch Says:

      You missed a spot in your almost complete copy & paste from the University of Michigan article:

      “Zak stressed that growth-enhancing effects of CO2 in forests will eventually “hit the wall” and come to a halt. The trees’ roots will eventually “fully exploit” the soil’s nitrogen resources. No one knows how long it will take to reach that limit, he said. The ozone portion of the 12-year experiment also held surprises.”

      There you go.

      Would it be too meta to direct you to the CO2 is plant food crock video?

      The “some is good for me so lots will be great for me” idea is the line of reasoning a child uses when they think about medicine. In case you’ve forgotten, let’s review: Some is good, but too much will either, at best, have little to no effect or, at worst, injure or even kill you.

      We are screwing with the balance of nature on a global scale and there are consequences to doing that. The narrow filter you’re using to make your argument ignores those consequences in favour of some minor point.

      • daveburton Says:

        Indeed, as my mama the chemist used to say, “the dose makes the poison.” Inhaling too much of anything will kill you. E.g., even though it is harmless and even beneficial in small amounts, thousands of children die every year from inhaling too much deadly di-hydrogen-oxide.

        Nevertheless, Dr. Zak’s “hit the wall” remark is unsupported by the team’s research. It is just conjecture.

        The “CO2 is plant food is crock” assertion is crock, too, as this video or any greenhouse operator could tell you. The reason that there’s more carbon in plants than in the atmosphere, and the reason that CO2 is a trace gas, measured in ppm, is that lack of CO2 is the most important limiting factor for plant growth.

        I’ve written Dr. Zak and asked how much CO2 they used. That would give us a good idea of a minimum of how far out “the wall” might be.

        Is there anyone here who has access to the paper? If so, please post how much CO2 and O3 they used!

        • Gorbin Wafflemunch Says:

          Curious. The article and Zak’s words are good enough to use almost the entire article, but when it comes to his thoughts on the limits of more CO2 for plants it’s conjecture and not worth acknowledging…apparently.

          I can’t help it Dave, I’m sensing more cherry picking on your part – or is it cherry coring if you take the majority of something but leave out the inconvenient bits?

          More CO2 and even ground level ozone for plants in greenhouses and experiments like this might be great and for now I’ll even go with you on CO2 being the most important limiting factor for plant growth.

          Di-hydrogen-oxide, I’d wager, is high up in the list of limiting factors for plant growth as well. Too much water is just as bad for plants as it is for us. Same goes for too little, as the folks in Texas are acutely aware of this year.

          I’m certain so long as water, nutrients and temperatures remain nice and stable more CO2 would do, at least some, plants quite well…but growth isn’t everything – you have the flip-side of that coin where you may get more plant but less nutrition from it. Leaving organisms that feed on said plants to consume more to gain the same benefits – which seems akin to “diluting” a plant.

          Increased temperatures can push plants outside their comfort zones, stressing and weakening the plant, as I’m certain any greenhouse operator can tell you (likewise on the too much/too little water bit).

          Higher temperatures can also encourage pests that would’ve been otherwise controlled by lower temperatures. Stressed and weakened plants have a diminished capacity to defend themselves and combined with more pests can easily result rampant destruction as is currently happening in the boreal forests of northern Canada.

          Then of course you have a destabilizing environment surrounding said plants – record floods, droughts and temperatures in both directions would seem to be negating any perceived benefits that more CO2 would make for plants.

          They have to survive in order to reap those benefits, and what of plants that don’t see benefits or are in fact negatively impacted by more CO2? This threatens bio-diversity, which Zak also referenced but then again I guess that was more conjecture and not worth pointing out. For the sake of completeness that point is below:

          “The interesting take home point with this is that aspects of biological diversity—like genetic diversity and plant species compositions—are important components of an ecosystem’s response to climate change,” he said. “Biodiversity matters, in this regard.”

        • daveburton Says:

          One of the papers to which witsendnj linked seems to have the answer to the question which I asked Dr. Zak:

          …elevated CO2 (+CO2) of 560 mmol/mol…

          That’s another way of saying ppm. I.e., the 26% growth improvement resulted from a relatively modest increase to 560 ppm CO2.

          That is very good news!

          Thanks, witsendnj.

          • witsendnj Says:


            “In a famous 1950s psychology experiment, researchers showed students from two Ivy League colleges a film of an American football game between their schools in which officials made a series of controversial decisions against one side. Asked to make their own assessments, students who attended the offending team’s college reported seeing half as many illegal plays as did students from the opposing institution.”

            Congratulations, daveburton! You obviously attended a prestigious Ivy League college!

          • daveburton Says:

            Okay, that’s weird. I did a straight copy-paste from the pdf article, yet μmol (or (µmol)) turned into mmol, changing micromoles into millimoles.

            Anyhow, that’s 560 micromoles/mol = 560 ppmv, probably chosen as double a presumed pre-industrial level of 280 ppm.

  2. witsendnj Says:

    This is from my post yesterday, about this research (link to the full article below0:

    You might think that this arboreal refutation might inspire Dr. Clark to reconsider the role of ozone in forest decline, since apparently, climate change isn’t explaining what is actually happening with the trees! I wrote him last April about an earlier study, and this was his reply, as I reported in the spring:

    “Gail, thanks for the note, a few thoughts.

    Ozone is a problem for plants, hard to study for large trees. For crops, it’s increasingly evident that rising CO2 can mitigate effects of rising ozone (or if you prefer, ozone offsets the stimulation that would have occurred with rising CO2). [This is wishful thinking, it is only true for low levels of ozone.] For large trees, it’s difficult to obtain more than leaf to branch level responses. For juvenile trees the evidence for a CO2 stimulation of growth is mixed–when experimentally increased as in FACE experiments, the initial stimulation of growth is not maintained, but it’s hard to manipulate ozone at that scale (whole trees competing for light in closed forests). Nonetheless, all evidence is that ozone is bad for all plants and certainly contributes to the health of trees in our study.

    In any study of mortality, there are risk factors that cannot be experimentally manipulated, so they become the background factors. Ozone levels have been high in our region throughout the duration of this study, and mortality rates could be higher throughout for that reason alone. What we studied are the factors that varied against this background, and they show the differing impacts of temperature, drought, and competition for light on different species. Ozone is not included in the study, because we could not experimentally manipulate it or design the experiment to benefit from a broad range of ozone levels. That does not mean it is unimportant.


    So basically, it is what it is. They study what is happening to trees with the level of ozone in the background as a given, because they can’t make it go away. It’s not unimportant, but it’s not important enough to design a study to see if air pollution is the reason tree range is “contracting from both the north and south” – in other words, they are in total dieback!!

  3. witsendnj Says:

    daveburton, unfortunately, I suspect that study is, shall we way, suffering from “optimism bias”.

    First of all, the FACE experimenters cut down all the trees in the chambers a year or two ago. They told me it over the phone that it was because they had gotten too big, and that it wouldn’t affect the results of the experiments, because the roots of the newly regenerated saplings were the same.

    It doesn’t take a professional forester to see that this reasoning is bogus, because one of the most important negative affects of ozone (although certainly not the only one) is a marked increase in the predations of insects, disease and fungus – which was demonstrated in their own previously published research. Now, all that going on in the branches and trunks would have been removed when they cut the trees down, thus vastly extending the life of the root stock.

    Why would they lie about something so obvious? Let’s look at the funding for this latest paper.

    DOE. ‘nuf said. Other?

    Forest Service. Just by coincidence, I happened upon a facebook post with beautiful photos, about how lovely and magnificent trees are, where someone had left this comment:

    “I agree, that is why I became a forester, unfortunately teh USFS is in the hip pocket of teh timber industry, so My trees were harvested in mass genocide, (clear-cuts) LOL ”

    I wrote the author last night for clarification – he told me he has since retired from what he called the “forest circus.”

    Here’s an excerpt of a post I just wrote about the Forest Service: (

    This is the time of year when I generally check in with the USDA Forest Service’s annual national Biomonitering Program, which has been collecting and analyzing samples of leaves for ozone damage at plots around the country, every year since 1994. I wouldn’t want the friendly fellow at the Northern Research Station who returned my call to get in trouble, so I’m not going to reveal his name….because this is pretty much how the conversation went, after I asked him about the most recent results:

    “Because of anticipated budget cuts, we didn’t collect any data this year. Nobody went out in the field.”

    After a moment of silent, incredulous astonishment, I started laughing a little hysterically. “Seriously? What are you guys doing with all that time on your hands?”

    He laughed too. “Well, we’re pushing a lot of paper around on our desks.”

    I’m NOT kidding. That’s what he said. Now, presumably foresters are still getting paid their salaries and benefits so, how much savings did the Forest Service realize by NOT sending them out to collect the leaves??

    Answer: just about nothing. So, why did they decide to stop collecting?

    Answer: the results are getting too scary. Don’t even ask WHO exactly made the decision.

    • daveburton Says:

      Seriously? Because of anticipated budget cuts (i.e., budget cuts that haven’t happened yet), they stopped collecting data??

      (However, I wouldn’t worry too much about the O3. In the USA, at least, ground level O3 is declining, not increasing. It is the CO2 results that are interesting.)

  4. witsendnj Says:

    daveburton, that is just wrong. PEAK levels have declined, but the BACKGROUND level of ambient tropospheric ozone is inexorably rising, everywhere. The precursors travel across continents and oceans. Now this whole crock has so annoyed me that I’ve wasted the whole day practically, reading the most recent FACE research, my favorites of which you can access yourself, by clicking on the clickies. The last sentence of the first abstract copied below is pretty scary.

    Click to access Wittig%20et%20al%20GCB%202009.pdf

    Abstract from above paper:

    The northern hemisphere temperate and boreal forests currently provide an important carbon sink; however, current tropospheric ozone concentrations ([O3]) and [O3] projected for later this century are damaging to trees and have the potential to reduce the carbon sink strength of these forests. This meta-analysis estimated the magnitude of the impacts of current [O3] and future [O3] on the biomass, growth, physiology and biochemistry of trees representative of northern hemisphere forests. Current ambient [O3] (40 ppb on average) significantly reduced the total biomass of trees by 7% compared with trees grown in charcoal-filtered (CF) controls, which approximate preindustrial [O3].

    Above- and belowground productivity were equally affected by ambient [O3] in these studies. Elevated [O3] of 64 ppb reduced total biomass by 11% compared with trees grown at ambient [O3] while elevated [O3] of 97 ppb reduced total biomass of trees by 17% compared with CF controls. The root-to-shoot ratio was significantly reduced by elevated [O3] indicating greater sensitivity of root biomass to [O3]. At elevated [O3], trees had significant reductions in leaf area, Rubisco content and chlorophyll content which may underlie significant reductions in photosynthetic capacity.

    Trees also had lower transpiration rates, and were shorter in height and had reduced diameter when grown at elevated [O3]. Further, at elevated [O3], gymnosperms were significantly less sensitive than angiosperms. There were too few observations of the interaction of [O3] with elevated [CO2] and drought to conclusively project how these climate change factors will alter tree responses to [O3]. Taken together, these results demonstrate that the carbonsink strength of northern hemisphere forests is likely reduced by current [O3] and will be further reduced in future if [O3] rises. This implies that a key carbon sink currently offsetting a significant portion of global fossil fuel CO2 emissions could be diminished or lost in the future.

    Click to access Uddling%20Stomatal%20uptake.pdf

    Click to access Darbah%20etal%202011%20JEnvironMonit.pdf

    Click to access Onandia%20etal%202011.pdf

    Click to access Hillstrom_et_al_2010.pdf

    Click to access Tai%20et%20al.%202010%20ENPO.pdf

    Click to access Riikonen_2010.pdf

    Click to access Uddling%20Stomatal%20uptake.pdf

    Abstract from above paper:

    Rising atmospheric carbon dioxide (CO2) may alleviate the toxicological impacts of concurrently rising tropospheric ozone (O3) during the present century if higher CO2 is accompanied by lower stomatal conductance (gs), as assumed by many models. We investigated how elevated concentrations of CO2 and O3, alone and in combination, affected the accumulated stomatal flux of O3 (AFst) by canopies and sun leaves in closed aspen and aspen-birch forests in the free-air CO2–O3 enrichment experiment nearRhinelander, Wisconsin. Stomatal conductance for O3 was derived from sap flux data and AFst was estimated either neglecting or accounting for the potential influence of non-stomatal leaf surface O3 deposition. Leaf-level AFst (AFstl) was not reduced by elevated CO2. Instead, there was a significant CO2 O3 interaction on AFstl, as a consequence of lower values of gs in control plots and the combination treatment than in the two single-gas treatments. In addition, aspen leaves had higher AFstl than birch leaves, and estimates of AFstl were not very sensitive to non-stomatal leaf surface O3 deposition. Our results suggest that model projections of large CO2-induced reductions in gs alleviating the adverse effect of rising tropospheric O3 may not be reasonable for northern hardwood forests.

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