Since there has been a huge amount of interest in Steve McIntyre’s recent discovery of what happens to the “hockey stick” when all of the Yamal tree ring data is used rather than a special subset of 10, I thought it might be a good time to talk about how tree rings are grown.
Several readers have correctly pointed out that trees don’t respond just to temperature. The also respond to available water, available nutrients in soil, and available sunlight. For example, the only time in modern history where some trees did not produce summer growth rings occurred in the year 1816, also known as the Year Without a Summer:
Many consider the Year Without a Summer to have been caused by a combination of a historic low in solar activity (The Dalton Minimum) and a volcanic winter event; such as the powerful Mount Tambora eruption in 1815 which had four times the power of the famous Krakatoa eruption and hurled huge amounts of aerosols into the atmosphere.
Obviously, sunlight was a limiting factor for tree growth then, reduced temperature also figured in.
I touched on the idea of trees used for dendroclimatology being rain gauges before: Bristlecone Pines: Treemometers or rain gauges ? There has obviously been years of drought when trees also did not grow as much, so how do we separate temperature and moisture in the growth analysis?
But, right now what I really want to introduce readers to is Leibig’s Barrel.
While I don’t like to use Wikipedia that much, this page doesn’t seem to be controversial so appears safe enough:
Liebig’s Law of the Minimum, often simply called Liebig’s Law or the Law of the Minimum, is a principle developed in agricultural science by Carl Sprengel (1828) and later popularized by Justus von Liebig.
It states that growth is controlled not by the total of resources available, but by the scarcest resource (limiting factor). This concept was originally applied to plant or crop growth, where it was found that increasing the amount of plentiful nutrients did not increase plant growth. Only by increasing the amount of the limiting nutrient (the one most scarce in relation to “need”) was the growth of a plant or crop improved.This principle can be summed up in the aphorism, “The availability of the most abundant nutrient in the soil is as available as the availability of the least abundant nutrient in the soil.”
Liebig used the image of a barrel—now called Liebig’s barrel—to explain his law. Just as the capacity of a barrel with staves of unequal length is limited by the shortest stave, so a plant’s growth is limited by the nutrient in shortest supply.
Liebig’s Law has been extended to biological populations (and is commonly used in ecosystem models). For example, the growth of an organism such as a plant may be dependent on a number of different factors, such as sunlight or mineral nutrients (e.g. nitrate or phosphate). The availability of these may vary, such that at any given time one is more limiting than the others. Liebig’s Law states that growth only occurs at the rate permitted by the most limiting. For instance, in the equation below, the growth of population O is a function of the minimum of three Michaelis-Menten terms representing limitation by factors I, N and P.
It is limited to a situation where there are steady state conditions, and factor interactions are tightly controlled.
In the book: Forest dynamics: an ecological model, 1993, Oxford University Press, By Daniel B. Botkin the relationship between all of the different growth factors is modeled per Liebigs Law. In Chapter 3, page 64 the author talks about Liebigs Law and how it operates on forest populations. He then goes no to describe a model of forest growth.
Page 65 has a very interesting passage which I’ve highlighted:
For our readers reference, JABOWA is his forest modeling software, now in version 3 which you can read about here and download a free trial. It was designed for a specific region, the Northeastern United States. From JABOWA another similar forest growth simulator FORET was derived, which has been adapted for modeling diverse forests of the southern United States. Obviously modeling different forest regions requires specific model programming.
The point I’m making with all this is: If “the total growth response of a tree is the product of all environmental factors”, and forest modelers have to separate temperature and precipitation diameter increments, plus create different models for different forest regions, how can then one accurately divine temperature over millenia from width analysis of tree ring growth from trees in a single region?
The task is huge.
It seems to me that temperature is intertwined with so many other factors that it can’t easily be separated without at least knowing how they also changed over time. Further on in the book the author goes on to talk about other limiting growth factors, such as soil moisture, available light, nutrients etc, but a couple of pages, 71 and 72, really described how temperature (as degree days) is figured into forest growth estimates. I was surprised to see that photosynthesis is not linear with temperature, but parabolic! I’ve excerpted the pages below.
Another interesting thing I learned was that to accurately gauge forest growth, you should have nearby weather records. Missing that, you can estimate the temperature profile from January and July average temperatures. OK but how do you do that for 200, 500, or 1000 years ago?
Barring having any temperature information from the region at all, the possibility exists for doing lab growth experiments, though I don’t recall seeing anything about that in MBH98 or similar papers.
I make no claims of being an expert in either forest growth or dendroclimatology. I’m simply presenting interesting information here for discussion.
But, I am amazed at the nonlinearity and interactivity of all limiting growth factors, and especially the parabolic response to temperature.
Thus in my opinion, it seems rather difficult to estimate forest growth when parameters are known, and even then the outcome is uncertain.
Imagine trying to reverse engineer temperature from forest growth (using tree rings) with all of the simultaneously acting growth factors, population density and shade limiting, the parabolic response curves, and you realize that divining the temperature out of trees over millenia is a very difficult, nonlinear, and uncertain task.
If you see a wide tree ring, you can safely conclude the tree had a good year. If you see narrow rings you can conclude a poor growth year. But was that poor year a product of an unfavorable temperature range alone? Or was it due to lack of moisture or lack of sunlight or both? Not having local records for those, how would you know?
It seems to me that dendroclimatology has a lot of uncertainty.
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Supercritical (01:04:09) : “…Personally, I am amazed that the whole Climate Chage/Carbon thing is reliant on this somewhat wispy science. (I would prefer it were called Dendro-haruspication.)”
I prefer “dendrophrenology.”
You wrote: “I was surprised to see that photosynthesis is not linear with temperature, but parabolic!”
Do you not live in or near wine country? I’m told many hot summer area vineyards use mist systems on auto-control to moderate the temperature as it approaches that point in the curve where photosynthesis would rapidly drop. Next time you need a break from the computer screen go have a talk with a winegrower and taste a few samples – it sooths the soul.
Jon:
“Tilo … in order for a plant to process more co2 it needs more water:
6CO2 + 6H2O + Energy ® C6H12O6 + 6O2”
Jon, I’m not an expert on this, but it seems to me to be important that this is not a test tube reaction we are talking about. In order for the reaction to occur, these molecules have to find each other. Sorry, about the “find each other” but I’m not sure of the right way to describe the problem. Anyway, let’s say that you keep the amount of water constant, but you increase the amount of CO2. This would not increase the total number of possible reactions, but it could increase the number of actual reactions because more of these molecules could find each other. The same priciple would apply if there were more CO2 but slightly less water.
Does that make sense, or am I completely out to lunch here. In any case, I didn’t make up the assertion that CO2 makes plants more drought resistant. I picked it up from a paper that I read some time ago on the subject of CO2 fertilization.
Very very interesting post, specially for a botanist and plant physiologist.
I have learned and teached that there was 3 kinds of response curves for different growth limiting factors.
1) For N, P, K … and water a curve with a plateau, and perhaps a toxicity but never encountered in true ecological situation.
2)For temperature an upside down quadratic response as said McInt at CA on october 10th 2005. A +/- 5°C around optimum leads to a loss of about 15% of growth.
3) For CO2 a near straight line without optimum or plateau only a slight bent at high doses between 0 and 1000 ppm or higher. The range of growth beeing 3 to 4 folds between 200 and 1000 ppm (300 to 400%).
I think that for trees in their optimal growth area the rings which vary, in mean over 10 years and about 30 trees, from 100 to 200% around the mean between Mediev Th Opt and LIA, the main factor governing tree ring groxth is partial CO2 pressure.
So I propose to call tree ring width proxies treebarometer or treebarco2meter.
Is it a joke? Or does it match with ice cores CO2 ?
What about a lofty plastic greenhouse, (maybe inflated using CO2) to test a bunch of variables on trees. I had heard that someone in Arizona I believe had done this to an orange grove to see if growth rates and fruiting were increased with CO2 concentrations (sorry no link)
AnonyMoose (09:37:06) : That’s the picture!
Jim B in Canada (22:47:09) : The big missing link here is how does CO2 increases change tree growth? That’s the study I want to see.
It would be nice to have a guest post from the Idsos here.
Now look at this Google map with all the site locations from a poster at CA. Just fly up there over the Russian trees and zoom in. I think the landscape itself (plus ground pics like in the Hantemirov Yamal paper have highly suggestive evidence that microclimate changes happen, moisture is a major factor, tree areas are sharply bounded (why?) and the watercourse meanders change often enough to show in the aerial photos.
A river course 2km wide in which the meanders change constantly: trees grow thick up to the edge of this “valley” but they end suddenly and beyond is dead naked tundra. There are many rivercourse changes (natural with meanders like these). Microclimates caused by different balances between permafrost levels, river levels, groundwater levels, small banks, and neighbouring trees.
When you are talking fractions of a degree up or down to demonstrate global warming or cooling, (the anomaly) it seems ludicrous that tree rings as indicators of temperature could have anything like the precision needed (even without all the interesting complications revealed in this blog). I don’t believe they know what they are doing. I think the same is true of the paucity of temperature measurement sites. I can see several degrees difference between New York and my yard 25 miles away. So what does a measured temperature mean for me if it is measured 1000 miles away? Millions of accurate temperatures taken simultaneously around the world would be needed to convince me that anyone knows the”global average temperature” to within a degree or so. And what about sea bed core samples. They say they can tell the temperature by which fossils are found in a sample representing a given period because certain ones prefer a particular temperature range. I just don’t believe these tiny creatures could live at T degrees, but not at T plus or minus 1 degree or so. This whole AGW construction is such a house of cards that it seems incredible that reputable scientists go along with it.
Retired BChe
You have a point! Most organisms are able to withstand a fairly wide temperature range, definitely more than +/- 1 celcius degree. Most terrestrial organisms experience wider temperature swings between midnight and noon every day. Aquatic creatures also experience swings greater than 1 degree over the year, especially in temperate climates.
Does seem strange that all of this panic is over a few possible degrees of warming that could happen maybe, someday, someplace. Yet with nothing but this kind of shoddy evidence, AGW/CC proponents accuse skeptics of treason against humanity and forcast the destruction of the planet.
jon (04:39:27) :
Nic … you could add insect defoliants, parasites, disease, herbivores and competition etc. to your list.
Jon – I was only trying to grasp the point that a bad growing season might be due to many factors.
Now you suggest that optimum growing conditions (which should produce a “warm” ring) might give a “cold” ring because ;
a.The caterpillars thrived and ate all the leaves.
b. The increased cow/sheep/reindeer population in the benign/optimum/warm conditions ate all the bark making the tree suffer.
c. No one has yet mentioned lichen/fungus/algae – thriving in the warm but having a parasitical effect.
d. Which leads me to mistletoe (a true parasite).= Parasite thrives in good conditions but host does not.
Oooh Eck. Um. Perhaps there is not a direct correlation between ring thickness and aveage annual temperature. There seem to be number of factors at play here.
What a fascinating area for study by those who know better.
Being an agronomist I’ve always been of the opinion that dendroclimatology is a little bit of voodoo and hocus pocus blended with science. Anybody who understands plant physiology knows that there are a great number of factors, and combinations of factors, that influence plant growth. As an example, you can have a cooler than normal year with ample moisture or a year that is warmer than normal with limited moisture and yet have the same size tree ring at the end of each year.
To further confuse the issue… a cool year with ample moisture and an abundance of sunshine can produce a ring the same size as a warm year with ample moisture and limited sunlight. There are simply too many variables to be able to reliably use a tree as a treemometer. This has been demonstrated with the “divergence” problem seen in the later half of the 20th century. Rather than admit to the obvious, dendroclimatologists have developed half-baked theories such as co2 fertilization in order to explain away this obvious stumbling block. I think the dendro community is due for a rude awakening.
Patrick Davis (23:39:58) :
“I know of a place where one can study 500+ year old tress, right now, today. New Zealand. Kauri and Totora trees are natives (So too are Pohutukawa trees, though I don’t think they live anyway near as long).”
yes, my cousin, Dr Andrew Lorrey of the U of Aukland’s climate dept, did a study of subfossil Kaori recovered from bogs to extend the NZ dendro record back thousands of years: http://hol.sagepub.com/cgi/content/abstract/16/2/188
You all may remember him from his cave speleotherm ring study (similar to dendro work) put out last year that covers a 5000-odd year period and helped put out solid peer reviewed evidence that the MWP was in fact a global climate effect, not limited to northern europe and north america:
http://wattsupwiththat.com/2009/01/03/4000-year-o18-histories-of-new-zealands-north-and-south-islands/
Is ring width or surface area even a valid proxy for the volume of each tree’s yearly growth?
Another limiting factor for tree rings as a proxy for temperature is whole concept of biological growth and sexual reproduction. Organisms that reproduce sexually ‘grow’ physically in size only up to a point that reproduction can occur. This is a bit like us, where in human males, maximum Femur length is reached at about 22 years of age. Height is more or less maintained throughout life and biological ‘energy’ is then devoted to reproduction. Trees are basically no different, the size they reach is the ‘correct’ size necessary for the next stage of the life cycle of the tree,namely, reproduction. Tree rings are laid down after reproductive maturity but at a slower rate and only enough to maintain the framework. The tree itself is mealy a living ,somewhat static scaffolding, that enables reproduction .
To assume that a tree will burst in to life and record its progress with a fat growth ring every time the temperature is optimal for 1000’s of years is simplistic in the extreme.
A tree existing for 1000 years in one location and not outstripping its resources must be doing something right, and growth for growth’s sake is not one of them.
“”” J. Peden (17:33:33) :
Is ring width or surface area even a valid proxy for the volume of each tree’s yearly growth? “””
Jim, the core boring tree ring method suffers from sampling errors, since the rings aren’t constant thickness all around or up and down the tree, so it depends on sheer luck as to where a core is drilled.
So is your Dory Still out on the water, or are you mothballing it for the ice season ?
George
As a gardener, Liebig’s barrel makes a lot of sense. On occasion, I will supply a garden or individual plant with as much as I can give but I don’t alway have control over the conditions after I’ve gone. Some people don’t appear to understand that compost and fertilizer become functional only in the presence of water, relative to the specific requirements of the plant. Seems pretty simple to me.
Internode length is also a relative measure of annual tree growth. Whether it can be detected in very old wood is another matter. Probably not.
“Imagine trying to reverse engineer temperature from forest growth (using tree rings) with all of the simultaneously acting growth factors, population density and shade limiting, the parabolic response curves, and you realize that divining the temperature out of trees over millenia is a very difficult, nonlinear, and uncertain task.”
Maybe Anthony’s just being conservative here, but I don’t think he’s going far enough in saying that the task is “very difficult” or “uncertain”. Frankly, the parabolic response curve alone makes it IMPOSSIBLE to divine temperature from tree ring width.
When a function is parabolic, you can easily determine the value of Y for any given value of X (in this case, X is temperature and Y is ring width). However, for any given value of Y, there are TWO values of X. So, if you know the width of the ring, even if you have accounted for all the other factors that have a hand in determining ring width, you still have two possible values for temperature. How do you know which one to pick? It’s IMPOSSIBLE. Unless, of course, you’re Michael Mann, in which case, you simply pick the lower temperature, because you KNOW temperatures could not have been higher at any time in the past than they are right now.
To be honest, what’s new with Liebig’s barrel, if we look at our selfes we function the same way. If our food contains to little of of one component we can’t even out that by eating more of something else, common sence! A well mixed diet is the best way to health!
What do dendroclimatologists eat?
Lord Monkton is soliciting money for a court case in NA to settle the hash before big government swamps us all. See Not Evil, Just Wrong.
George E. Smith:
“Jim, the core boring tree ring method suffers from sampling errors, since the rings aren’t constant thickness all around or up and down the tree, so it depends on sheer luck as to where a core is drilled.”
Yeah, I know.
Btw, I’m not Jim who has a dory, but I do admire your thought.
MITSCHERLICH’S LAW OF PHYSIOLOGICAL RELATIONS is the response most physiologists acknowledge is a better fit to the data. Liebig is obsolete.
Some others questioned interactions, this is a general response from an abstract (my copy of the paper is behind a paywall), I’ll get others later:
Light and temperature-response curves and their resulting coefficients, obtained within ecophysiological characterization of gas exchanges at the leaf level, may represent useful criteria for breeding and cultivar selection and required tools for simulation models aimed at the prediction of potential plant behaviour in response to environmental conditions.
Leaf-scale gas exchanges, by means of an IRGA open-flow system, were measured in response to light intensity (8 levels from 0 up to 2000 μmol m−2 s−1), CO2 concentrations (ambient—350 μmol mol−1 and short-term enriched—700 μmol mol−1) and air temperature (from 7 up to 35 °C) on three Vicia faba L. genotypes, each representing one of the three cultivated groups: major, equina and minor. The net assimilation rate response to light intensity was well described by an exponential rise to max function. The short-term CO2 enrichment markedly increased the values of light response curve parameters such as maximum photosynthetic rate (+80%), light saturation point (+40%) and quantum yield (+30%), while less homogenous behaviour was reported for dark respiration and light compensation point. For each light intensity level, the major and minor genotypes studied showed assimilation rates at least a 30% higher than equina.
The positive effects of short-term CO2 enrichment on photosynthetic water use efficiency (WUE) indicate a relevant advantage in doubling CO2 concentration. In the major and minor genotypes studied, similar assimilation rates, but different WUE were observed.
The optimum leaf temperature for assimilation process, calculated through a polynomial function, was 26–27 °C and no relevant limitations were observed in the range between 21 and 32 °C.
Analysis at the single leaf level provided both rapid information on the variations in gas exchange in response to environmental factors and selection criteria.
The reason Stratevarius violins sound so good is because he picked trees with tighter tree rings that grew at higher altitudes during the last little glacial (Maunder Minimum). The global warming idiots do not even hear the violins playing their death song.
Er, I was struck by the idea that temperature was derived from ring growth thickness. That tree growth is affected by a variety of factors was nicely illustrated by the article by the guest writer about trees showing response to fertiliser. So I was struck by the problem of isolating one factor from all the others.
Thus, in fact, Liebigs law of Minimums actually clarifies and provides a foundation for the proposition that tree rings can be temperature proxies.
This is because, as presented here, the tree growth will depend not on all factors but on the minimum.
On Dr Briffa’s web information (http://www.cru.uea.ac.uk/cru/annrep94/trees/) we see he claims that for high altitude trees that minimum is temperature…. so we could accept the idea that high altitude tree growth is linked to temperature.
It isn’t, in fact, the ring width that is measured but oxygen isotope ratios, according to the Science Daily article (http://www.sciencedaily.com/releases/2008/06/080611135100.htm) that discusses the new study suggesting that tree leave temperature is largely self regulating.
The article says:
“….scientists studying climate change have measured the oxygen isotope ratio in tree-ring cellulose to determine the ambient temperature and relative humidity of past climates.”
“The assumption in all of these studies was that tree leaf temperatures were equal to ambient temperatures.
Researchers at Penn, using measures of oxygen isotopes and current climate, determined a way to estimate leaf temperature in living trees and as a consequence showed this assumption to be incorrect.”