Ed: Speaking of tree rings, someone just pointed out this new paper on how to use tree rings to detect earthworms invasions, is already available online:
Larson, E.R., K.F. Kipfmueller, C.M. Hale, L.E. Frelich, and P.B. Reich. 2009. Tree rings detect earthworm invasion and their effects in northern hardwood forests. In press. Biological Invasions. We just submitted the revised version of this paper to the editor two weeks ago, he accepted it immediately, the galley proofs came one week later, were sent back last week, and the paper is published online this week (printed version will follow in a few months)! That definitely beats the old days when it took years of back and forth by snail mail to get something published. The basic story is that when European earthworms invade, there is a period of a few decades where tree-ring width declines by 20-30% in sugar maple. This tree ring signature is independent of droughts and other causes of variation in tree rings, and therefore dates the time of invasion by the worms. The mechanism is probably loss of fine roots in the organic horizon (aka duff layer) of the soils, loss of mycorrhizae that sugar maple need, and warming and drying of the soil caused by loss of the insulating properties of the duff layer. Lee Edward Frank wrote: > Hello, > > There are many dendrochronology people on the list and they may be > able to address the question better. There are a couple of basic > assumptions in tree ring dating: basically a tree grows one year, > every year. So by counting the number of rings you can determine the > age of the tree. The thicker the ring obviously the more the tree > grew during that year. This overall is a pretty good assumption. > There are some caveats however. In some trees there are locally > missing rings - a ring does form every year, but if it has been a > really dry year, for example, there may have been little growth > between on set of rings and the next. The two adjacent sets of > rings formed during this period of little growth in a particular > cross-section or core may be impossible to distinguish. What appears > to be 1 ring may in fact be two. Then by simply counting rings the > age of the tree will be understated because of the "missing" ring. > Cross-sections are better for seeing these rings as the amount of > growth may vary in different portions of the tree, but still there is > a possibility that some rings are missing. If the ring thickness is > relatively uniform across the the cross-section, that is one > indication that missing rings may be less likely. The other caveat is > the phenomena of false or double rings. In this case a dark colored > late-wood and appears within the lighter colored early wood of the > band. In the false ring both edges of the dark band tend to blend > with the lighter wood on either side. In a true ring the transition > on the outer edge of the ring is abrupt. This can be seen with a hand > lens on a sanded surface. This doesn't always work well with all > species. > > In dendrochronology they use things like skeleton plots and > statistical analysis packages to compare a series of rings from > different trees in the same area. The missing rings and false rings > will not be present in al of the specimens, so through cross-dating > between multiple specimens these problem rings can be eliminated from > the dataset. When looking at cross-sections from downed trees, likely > the best you can do is to simply count the rings present. Without > many samples of the same species from the same area you can't really > cross-date between specimens and presence of false rings and absence > of missing rings will not be distinguishable. I most cases these make > up only a small percentage of the total number of rings present in a > sample. So basically it is that simple. Just count the rings, and > realize that the numbers you are generating may be off by a few years, > > There are many sites on the internet that discuss these situations and > have examples of photos. You can start on a site like the Ultimate > Tree Ring Website: Henry writes: > > *The Ultimate Tree Ring Web Pages* http://web.utk.edu/~grissino/ > <http://web.utk.edu/%7Egrissino/> Welcome and thank you for visiting > the Ultimate Tree-Ring web pages, designed to be the ULTIMATE source > for information on the science of Dendrochronology. I've designed > these pages to be easily understood by people at all levels of > education, from elementary school students to high school students, > from first grade teachers to college professors. You won't find > anything fancy here - I want these pages to be readable, enjoyable, > and (most of all) educational. My goal is to make available as much > information about dendrochronology as I can possibly find on the > Internet, from the basics of tree-ring dating, to reference and > bibliographic information, to products and supplies, to books, and > more! My mission was born from an overwhelming need among > dendrochronologists for a permanent repository of information that was > free to the public, easily understandable, and as comprehensive as > humanly possible. Come back and visit from time to time to learn more > about new or updated software, new educational tools, new institutions > conducting tree-ring research, new publications, and more! > > You can also search the internet for information via one of the search > engines (I like www.metacrawler.com <http://www.metacrawler.com>) > > I have been trying to collect data from such ring counts of trees like > you are doing. For many of the trees found in both eastern and > western United States there is little actual information on how old > these trees may grow. Commonly only the trees know to live the > longest are heavily sampled, because the information is being used for > archaeological and environmental reconstructions of the past. Trees > not know for great age are not routinely or systematically sampled. > Many of the tree species commonly referred to as short living species > that live perhaps a hundred years have individuals well over two years > in age. Only a fraction of the hundreds of species of trees existing > in the US have any published ages from cross-dating or ring counts > published at all. There is a table on the ENTS website where I am > compiling this information. So if you have ring counts to contribute, > that information would be appreciated. > > > Ed Frank > > "The most beautiful thing we can experience is the mysterious. > It is the source of all true art and all science." - Albert Einstein > > > > > > --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
