I think it might be helpful to look at dendrochronology here. Ring width (and therefore diameter growth) is commonly used to infer climate-growth patterns of tree growth.
That said, Wayne and Dev bring up a number of relevant points: 1. Time scale: years or decades of data are needed to get a reasonable picture of climate response. Fortunately, tree rings can extend your records back until the birth of the trees at relatively low cost. 2. Microclimate: this is often an important consideration, especially in topographically diverse habitats. Ideally this is controlled for during sample collection but you might be able to include it as a predictor variable. 3. Site-level factors affecting growth: like Wayne says, a great number of non-climatic factors (esp. fertility) influence tree growth. As a result, it's much more helpful to examine year-to-year response to climate, whether you're looking at height or diameter. 4. Age has an extremely strong effect on diameter and height, as well as their rate of change. This needs to be controlled for, either by using a published age-growth equation, or via standardization. Dendrochronology has a long history of controlling for age-related effects using detrending curves or regional curve standardization (which identifies and remove common age-related effects). If you have a long enough record of growth, these techniques could likely be adapted to DBH measurements. The one final caution, make sure to include climate covariates and look beyond linear responses. -Jacob On Fri, Mar 8, 2013 at 1:05 PM, Thomas J. Givnish <[email protected] > wrote: > While in general I concur with Wayne's view that "all kinds" of site > variables can affect tree height and dbh - most meaningfully, asymptotic > tree height - I disagree with the flip statement that "mean annual anything > as independent variables are next to worthless". My colleagues and I have a > paper we are about to submit that predicts max tree height from two "mean > anything" environmental variables over a 600-km transect with an r2 = 0.88. > That is NOT "next to worthless". > > Thomas J. Givnish > Henry Allan Gleason Professor of Botany > University of Wisconsin > > [email protected] > http://botany.wisc.edu/givnish/Givnish/Welcome.html > > > > > On 03/08/13, Wayne Tyson wrote: > > Dev (and Ecolog): > > > > Climate is highly variable from place-to-place, even in the "same" > location, and "all kinds" of site variables can affect tree height and dbh > (not to mention age). Mean annual anything as independent variables are > next to worthless (or worse, misleading) unless you have years, decades, to > devote to the project (and even then they are very questionable), largely > because such variable can vary too much from year to year. DBH is a very > crude measure, and cores are also crude (except for the single tree being > cored). > > > > I must be missing something if this is the way "most contemporary > studies" are done. I hope someone can point out the errors of my thinking. > > > > WT > > > > ----- Original Message ----- From: "D Chakraborty" <[email protected]> > > To: <[email protected]> > > Sent: Friday, March 08, 2013 5:51 AM > > Subject: [ECOLOG-L] need help > > > > > > Dear Colleagues > > I am working on developing growth response functions to investigate the > > effects of climate on growth performance of Douglas fir provenances. Most > > of the contemporary studies use multivariate models with tree height at > > specific age as dependent variable and climate parameters(eg. Mean annual > > temperature, degree days , Annual heat mositure index etc) as independent > > variable. > > > > We all know that tree height is least influenced by management and > > therefore its most logical to use tree height as the dependent variable. > > However in my case I have very little tree height data. > > > > In this circumstance I am looking for your valuable opinion that can > > justify the use of DBH as a dependent variable. > > > > Looking forward to hearing from you. > > best regards > > Dev > > > > > > > > -- > > Debojyoti Chakraborty > > Wissenschaftlicher Mitarbeiter > > Department of forest and soil sciences, Universität für Bodenkultur Wien > > Ph: Vienna +43 6764871296 (m) > > > > Lecturer, Amity Institute of Global Warming and Ecological Studies > > Amity University campus, Block D, II floor,Sector 125, NOIDA > > India www.amity.edu/aigwes > > India +919868001750 (M India), 01204392562 (O) 0120-4392606 (Fax) > > alternate email id: [email protected], [email protected] > > skype: d-chakraborty > > > > > > ----- > > No virus found in this message. > > Checked by AVG - www.avg.com > > Version: 10.0.1430 / Virus Database: 2641/5656 - Release Date: 03/08/13 > > -- >
