From Wiley-Blackwell, via Eurekalert, something just plain surprising.
Nibbling by herbivores can have a greater impact on the width of tree rings than climate, new research has found. The study, published this week in the British Ecological Society’s journal Functional Ecology, could help increase the accuracy of the tree ring record as a way of estimating past climatic conditions.
Many factors in addition to climate are known to affect the tree ring record, including attack from parasites and herbivores, but determining how important these other factors have been in the past is difficult.
Working high in the mountains of southern Norway, midway between Oslo and Bergen, a team from Norway and Scotland fenced off a large area of mountainside and divided it into different sections into each of which a set density of domestic sheep was released every summer.
After nine summers, cross sections of 206 birch trees were taken and tree ring widths were measured. Comparing these with local temperature and the numbers of sheep at the location where the tree was growing allowed the team to disentangle the relationship between temperature and browsing by sheep and the width of tree rings.
According to lead author Dr James Speed of the NTNU Museum of Natural History and Archaeology: “We found tree ring widths were more affected by sheep than the ambient temperature at the site, although temperatures were still visible in the tree ring records. This shows that the density of herbivores affects the tree ring record, at least in places with slow-growing trees.”
The impact of large herbivores on tree rings has, until now, been largely unknown, so these findings could help increase the accuracy of the tree ring record as a way of estimating past climatic conditions, says Dr Speed: “Our study highlights that other factors interact with climate to affect tree rings, and that to increase the accuracy of the tree ring record to estimate past climatic conditions, you need to take into account the history of wild and domestic herbivores. The good news is that past densities of herbivores can be estimated from historic records, and from the fossilised remains of spores from fungi that live on dung.”
“This study does not mean that using tree rings to infer past climate is flawed as we can still see the effect of temperatures on the rings, and in lowland regions tree rings are less likely to have been affected by herbivores because they can grow out of reach faster,” he explains.
Tree rings give us a window into the past, and have been widely used as climate recorders since the early 1900s. The growth rings are visible in tree trunk cross sections, and are formed in seasonal environments as the wood is laid down faster in summer than winter. In years with better growing conditions (in cool locations this usually means warmer) tree rings are wider, and because trees can be very long-lived and wood is easily preserved, for example in bogs and lakes, this allows very long time-series to be established, and climatic conditions to be estimated from the ring widths.
The study was funded by the Norwegian Research Council and the Norwegian Directorate for Nature Management.
James D. M. Speed, Gunnar Austrheim, Alison J. Hester and Atle Mysterud (2011), ‘Browsing interacts with climate to determine tree ring increment’, doi: 10.1111/j.1365-2435.2011.01877.x, is published in Functional Ecology on 27 July 2011.
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When asked for comment about their effects on tree ring widths, possibly affecting paleoclimate studies based on tree rings, the sheep denied complicity and said repeatedly “Maaaa aaa aann Maaaa aaa aann“.
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For those wanting a primer on all the things that can affect tree growth, may I suggest this primer.
Jessie wool still is one of our biggest exports particularly fine wool. But remember our ‘woolly jumpers’ also provide meat. And one of the Greens objectives and Gaunaut’s suggestions was to cut methane emissions, beef and sheep should be taxed $11 per head and $7 per year respectively. NZ is considering introducing agriculture into carbon taxing that Garnaut suggested also. Gaunaut also suggested that farmers ‘farm’ kangaroos also. Ever tried to milk or shear a kangaroo, not withstanding they have defied domestication as they are marsupials. Just Google
Ross Garnaut on methane emissions. The man is a nut! Suggested that farmers through carbon credits from soil sequestration could make more money than farming and wool production.
Well wind farms are giving farmers $10,000 dollars a year per wind turbine as rent on their land.
One farmer has fifteen on his land, probably more than he would recover from farming without any expenditure at all. That’s what is happening in Oz. Four corners had a good program
on Monday 25th July about health and farmers near wind turbines. (Available from ABC TV Four Corners). Interesting stuff.
But did they control for the higher albedo of the sections with the sheep? 😉
richard verney says:
July 27, 2011 at 3:32 am
Yes, it’s amusing, stupid and all that but someone paid these idiots to do this rubbish and with whose money ?
Wife’s friend says their section of Oregon has not gotten above 84F while we in Kansas have not gotten below 84F for more than a few minutes each night. What sort of proxy for world wide temperatures would come from trees in these locations?
“sheep pun – they’ve all been used up”
No, it’s airy stuff, perhaps, butt perpetrators of the rampant AGW scam wool need to be thoroughly lambasted, and there a får more plays on words and puns to horn in on yet, shor nuff (especially if we schapen our multilingual skills).
The biggest unknown about tree rings is the effect of precipitation and evaporation, especially where water is in short supply. Take a look at any mountainous desert area and you will see trees above a certain elevation but none below where it is hotter and drier. If you look at slopes in the Rocky Mts., you will see trees on north-facing slopes but none on south-facing slopes. The reason is that south-facing slopes in the Northern Hemisphere get more direct sunshine, hence are drier and difficult for trees to grow. For a given area, imagine comparing the relative widths of rings from trees on slopes intermediate between north and south facing. A small increase in precipitation will have a much greater effect than a change in temperature. A more telling experiment than the sheep study would be to divide an area into plots (all of which will have the same temp) and vary the amount of water each plot receives rather than the number of sheep each plot receives).
Pete in Cumbria UK says:
July 27, 2011 at 2:54 am
The one closest to the petrol station was maybe 7ft tall and each tree was about 6″ less than the previous one, decreasing in size in a perfectly linear fashion as they got further from the filling station.
Could be sunshine and shade. The taller one was in the sun longer.
As co2 is always increasing I would expect bigger rings now, not because it’s warmer but because the trees have more co2 to extract.
Lightning creates NOX which would create nitrogen-based acids in the humid atmosphere and with the rain which would, either or both, attack and damage leaves or soak into the ground with the rain and fertilize the trees. A gentle rain produces no lightning, so maybe trees are also a proxy for lightning activity?
This is such a great site. Got my daily dose of face palm again. Where else could you find all of this stuff. Baaaa Humbug.
i don’t know much about elks, moose and reindeer. But Deer do eat bristlecone pines when there is nothing else to eat. It is possible the big guys ( elk, moose, reindeer ) do to. May be someone in this site enlighten us.
Because generally there are not a whole lot of leaves on these plants, and they don’t really grow straight up all the time, and the leaves do not regrow very fast, it is possible Deer could do a lot of damage to any one particular bristlecone tree, even if it is a couple of hundred years old tree. Eat some 1000 needles, not a whole lot left. next year’s tree ring is probably not too good.
Don’t know if they eat the bark as well, and what the effect of de-barking them will be on the tree rings. I know nothing about the tree selection process used for the Yamal or any other dendro studies
SO, SO many unknowns!!!
You should do a story on how Ice core rings are also not accurate because they aren’t annual rings.
Hey, what’s this business about separating the trees into areas and putting different sets of animals into the areas and controlling for other variables?
Don’t they know the CORRECT way to do science is to make up some numbers, write some random equations, run the fake numbers through the random equations, then declare your hypothesis is proved?
How’d they get this hopelessly obsolete “controlled experiment” stuff through peer review?
Do warmists dream of electric sheep?
/justkidding
Clay Marley says:
July 26, 2011 at 10:09 pm
This study suggests tree rings can also be a proxy for the density of mann.
Jessie says:
July 27, 2011 at 5:08 am
Dave Wendt says: July 27, 2011 at 4:27 am
…….. i.e. the infamous crocabalone.
Excellent. Do they design necklaces? And where can one purchase such?
Unfortunately, no. The creatures shell, when given a thorough professional polishing, will briefly display the iridescent luster of the abalone, but very quickly reverts to a more croc like presentation. Also, as an “unexpected” and unintended consequence it gives off a powerful smell that makes a durian seem like a bouquet of roses and lavender by comparison.
As a young pup in in Cyprus I do remember seeing sheep in the lower parts of whatever olive trees they could climb. They were going after the new growth.
Mutton heads! Mr. Mann can not bring himself to sheepishly admit that using tree growth rings for temperature proxies is just baaaaaaaaaaa-d science…
The problems with tree ring proxies are well known which is why they are matched against other proxies.
The link itself notes:
Many factors in addition to climate are known to affect the tree ring record, including attack from parasites and herbivores, but determining how important these other factors have been in the past is difficult.
The lead author states:
The good news is that past densities of herbivores can be estimated from historic records, and from the fossilised remains of spores from fungi ..This study does not mean that using tree rings to infer past climate is flawed as we can still see the effect of temperatures on the rings, and in lowland regions tree rings are less likely to have been affected by herbivores because they can grow out of reach faster”
I am amazed, but today I noticed sheep nibbling at the base of some trees. This was more or less at head height – no joke. I couldn’t photograph it becasue I was driving at the time. So they do it for sure, but whether this is the significant nibbling or not I don’t know.
Its not so much the nibbling of the trees themselves but the eating of the grasses and clover etc.
the sheep rip out the plants at the roots, leaving barren ground behind. one result of course is that with this vegetation gone less water is absorbed down into the soil for use by the trees. it simply runs off too quickly. second is the decimation of nitrogen fixer species. less nitrogen in the soil also prohibits the tree growth.
So the reason they use tree rings is because its much easier to find trees that are conform and “support” the political established UNFCCC?