Might also want to think about Rosenzweig's famous plot of ecosystem productivity against potential evapotranspiration. With all due respect, Wayne, that finding wasn't next to worthless either.
By the way, our study of tree height is NOT in Wisconsin, and it covers nearly the entire range of angiosperm tree heights found on Earth. 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: > Thanks to Givnish for pointing this out. > > I said NEXT to worthless, not ENTIRELY worthless. I don't doubt that in some > contexts that include huge transects across fairly homogenous conditions > (like Wisconsin?), unlike fairly heterogeneous environments common in the > western US, depending upon which two variables produce such results. In the > absence of knowing what those two variables are, however, I can't comment > further, but until then I will take Givnish's word for it--in his case. > > But given the context of "most contemporary studies," I wonder what the > evidence is for all or most of those studies? Also, given contemporary and > past studies (in each of those cases), how many of those studies actually > proved anything, and what did they prove? How many didn't prove much of > anything? > > How broadly can methodologies be applied without taking differences not > considered by the investigators (e.g., topography, aspect, geology, soils, > microclimates, and other possibly relevant variables) be applied without > considerable modification? > > The problem with means is what they mean. > > "The more you generalize about a population, the less you know about any > individual in that population." --Henry Geiger > > Especially in heterogeneous environments, the chances of randomly sampling an > outlier organism are great, as are the chances of getting skewed results. But > I grant you, that ain't all bad--depending upon what one is trying to prove. > > WT > > ----- Original Message ----- From: "Thomas J. Givnish" > <[email protected]> > To: <[email protected]> > Sent: Friday, March 08, 2013 10:05 AM > Subject: Re: [ECOLOG-L] need help > > > 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 > > -- > > > ----- > 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 --
