I 



Introduction 



Management planning for timber production commonly states its goals in terms of 

 tree size at harvest. Tree size, especially diameter at breast height Cd.b.h.)i has 

 become an Increasingly important element of such planning. In addition, tree size 

 influences the quality and production costs of timber products and the biological and 

 esthetic character of growing stands. 



Growth and yield information is grossly inadequate for lodgepole pine (Pinus 

 contorta Dougl . ) in Montana, Idaho, and Utah, although results from some studies in 

 surrounding areas may be extrapolated to fill immediate needs for approximate data on 

 volume yields per acre (Dahms 1966; Myers 1967). The development of tree size has not 

 been studied as intensively as stand growth and volume yield; therefore, such studies 

 hold great promise for refining growth and yield estimates. 



The purpose of this paper is to report the development of equations for predicting 

 future tree diameters at breast height for lodgepole pines in Montana, Idaho, and 

 northern Utah. A related report^ describes a stand growth prognosis program that uses 

 growth equations like the ones in this report to synthesize the development of stands. 



^A. R. Stage. A model for the prognosis of forest stand development. Intermoun- 

 tain Forest and Range Experiment Station. (In preparation.) 



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