Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help
 

Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (783 KB)

Title: Weighted linear regression using D2H and D2 as the independent variables

Author: Schreuder, Hans T.; Williams, Michael S.;

Date: 1998

Source: Res. Pap. RMRS-RP-6. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 10 p.

Publication Series: Research Paper (RP)

Description: Several error structures for weighted regression equations used for predicting volume were examined for 2 large data sets of felled and standing loblolly pine trees (Pinus taeda L.). The generally accepted model with variance of error proportional to the value of the covariate squared ( D2H = diameter squared times height or D2 = diameter squared) remains the best. Although D2H is a better covariate than D2, we found no significant difference between them when testing model accuracy for felled trees, but there were significant differences for standing trees. When we predicted the total volume of a population using equations based on felled tree data, assuming known frequencies for diameter classes and using D2H as the covariate, we obtained essentially the same estimate as that predicted using D2 (0.1 % difference). Using the conventional approach of D2H for all trees (standing and felled) yielded an estimate of volume of 5.6% less than using the equation with D2H for felled trees only. Trees are more accurately measured for volume when felled, and total heights are often not measured accurately on standing trees. Therefore, we recommend that volume equations be based on felled tree data only and that when they are intended to be applied to standing trees, D2 be used as the covariate in prediction.

Keywords: best volume equations, felled trees, standing trees, measured heights, basal area

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
  • You may send email to rmrspubrequest@fs.fed.us to request a hard copy of this publication. (Please specify exactly which publication you are requesting and your mailing address.)

XML: View XML

Citation:


Schreuder, Hans T.; Williams, Michael S. 1998. Weighted linear regression using D2H and D2 as the independent variables. Res. Pap. RMRS-RP-6. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 10 p.

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.