Bob, For the past few months I've been immersed in crossdating junipers, but I have no idea if my experience with J. virginiana and J. communis is applicable to Rocky Mountain juniper. The first step is to get a very clear surface on the specimens; going to 400 grit sandpaper is a minimum, and 600 or 1000 grit wouldn't be a bad idea. With a good microscope and careful examination of the ring boundaries, many of the false rings may be visually identifiable. Collecting cross sections from dead individuals could also help with learning to recognize false rings since false rings often vary in their sincerity at different points on the circumference. If false rings can be reliable recognized, they may actually be a great aid to crossdating since they give individual rings a distinct and can act as a second pattern to match; hence, false rings should be noted on skeleton plots or other crossdating aids. Using false rings also gets around the problem of poor circuit uniformity (when the width of one ring relative to other rings varies at different points on the circumference), but it may not be possible to use this strategy with Rocky Mountain Juniper. A relatively large sample size, and collecting multiple cores per tree may also be essential. I've had problems where I collected from only 21 individuals, seven of them dead, but have not had any serious difficulty where I sampled over 30 individuals. In any case, spending a lot of time looking at the samples to learn the appearances of individual years and patterns will probably be necessary.
Much better advice could probably be obtained from more experienced individuals who have worked with this species. Contacting the tree ring lab at the University of Arizona would be a good starting point. Connie Woodhouse at the University of Colorado and Peter Brown with the Rocky Mountain Tree-Ring Research, Inc are also experienced dendrochronologists in that region. Jess On Thu, Jun 11, 2009 at 7:32 PM, <[email protected]> wrote: > Neil, > I visited the Forest Service regional office today in Durango to get > information on the whereabouts of big trees and old growth. It was my > extreme good fortune to be introduced to Laura Stransky of the Forest > Service. She is an expert on old growth in the San Juans, having > participated in the inventory of old growth in the San Juan National Forest. > She aslo knows the whereabouts of big timber. She is going to dig out some > data on tree sizes for me. She remembered that the largest ponderosa that > the Forest Service has measured in the San Juans was 63 inches in diameter > at the time of measurement and the Forest Service has measured ponderosas up > to 151 feet in height. That is impressive. Laura gave me places to go to > find big ponderosa pines and Doug firs, which I will soon visit. I will, of > course, share all the data I gather with the Forest Service. That goes > without saying. > In my conversation with Laura, she mentioned that the Forest Service was > interested in determining the ages of Rocky Mountain juniper, but they are > having trouble determining ages for the species because of the small amount > of live tissue juxtaposed to the large amount of dead. I think I interpreted > correctly the problem she described. Do you have any experience dating the > species, or if not, know of another dendrochronologist who does have? I > would really love for us to establish a good working relationship with the > Forest Service here in Durango. Can you help with advice on dating the > junipers? > Laura, > Neil is Doctor Neil Pederson of Eastern Kentucky University. Neil has > worked under several of the top dendrochronologists in the world, and that > is no stretch. Foremost are the scientists at Lamont-Doherty Earth > Observatory at Columbia University, including Dr. Edward Cook. Neil is also > a colleague of Dr. Dave Stahle of the University of Arkansas's Tree-Ring > Laboratory. I'm sure that among this group, we can get you some advice on > dating the San Juan junipers. I can measure trees, but dating ancient trees > or developing tree ring chronologies is out of my league. Again, thank you > so much for the help you gave me this afternoon. I look forward to working > with the Forest Service to determine the maximum growth potential of the > species I mentioned across their full ranges. > Bob > > > --~--~---------~--~----~------------~-------~--~----~ 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] -~----------~----~----~----~------~----~------~--~---
