United States 

 Department of 

 Agriculture 



Forest Service 



Intermountain 

 Forest and Range 

 Experiment Station 



Research Paper 

 INT-283 



August 1981 



Crown Width and 

 Foliage Weight of 

 Northern Rocl<y 

 IVIountain Conifers 



Melinda Moeur 



INTRODUCTION 



This paper reports on the development of multiple linear 

 regression models predicting individual tree crown width and 

 foliage weight for 1 1 conifer species in northern Idaho and 

 western Montana. The equations have been applied in a spruce 

 budworm version' of the stand prognosis model (Stage 1973) 

 being currently developed. The crown width and foliage bio- 

 mass equations, when linked with other relationships in the 

 spruce budworm system, help predict insect damage and dis- 

 persal of larvae dunng simulated outbreaks. The crown width 

 function has also been used to predict percent stand crown 

 cover in the prognosis model (Stage 1973) for linkage with 

 proposed watershed^ and big game habitat prediction-^ sub- 

 models. 



The relationship between crown width and tree diameter has 

 been of interest to several researchers in developing crown 

 competition indices (see for example Krajicek and others 1961 

 or Vezina 1963). This relationship has been expressed as: 



crown width = a + b (d.b.h.) 



'Crookston. N L The interface between the stand prognosis model and the 

 western spruce budworm model — Version 1 2 Unpubl rep on file. Intermt For 

 and Range Exp Stn.. Forestry Sciences Laboratory. Moscow. Idaho. October 

 1980. 30 p 



^Simons. D.B . R.M Li. and T.J Ward 1980 Development of a generalized 

 planning model for assessing effects of land use .changes on watershed re- 

 sponses and aquatic habitat conditions Unpubl study plan. 14 p Colo State 

 Univ. Dep Civil Eng . Fort Collins. 



^Peek. J M 1970 Study plan: evaluations of elk habitat use patterns and 

 relationships in the Gospel-Hump area of central Idaho. 10 p Univ Idaho. Wlldl. 

 Resouf.. Dep. For . Wlldl and Range Sci.. Moscow. 



In some studies, for example S:iell (1966). stand density in- 

 versely influenced tree crown width. Vezina (1954) used stand 

 basal area to predict stand crov/n closure. Bonnor (1964), in 

 studying the relationship between diameter at breast height 

 (d.b.h.) and crown width on vertical photography, found no 

 effect from stand density. The current study investigates the 

 contribution of a number of stand and individual tree character- 

 istics in predicting crown width by species. 



The second part of this study looks at the 'elationship be- 

 tween individual tree foliage weight and measured tree and 

 stand characteristics. Kittredge (1944) developed the following 

 logarithmic expression to estimate leaf weight for several conif- 

 er ano hardwood species: 



In (leaf weight) = b (In d.b.h.) - a 



He noted conflicting site and age effects, possibly confounded 

 by geographical location. The effects of density and crown class 

 as sources of variation were not separated out in his study. 



Brown (1978) approached the problem of estimating foliage 

 weight indirectly by first developing total crown weight as a 

 function of tree diameter, height, and crown length, and then 

 estimating the proportion of the total crown in foliage in a sepa- 

 rate equation. In addition, Brown presented more than one 

 model form for each species depending on crown class and size 

 class. The current study used Brown s data with the purpose of 

 simplifying the direct estimation of foliage weight by inve'Sti- 

 gating one or two model forms applicable to all tree species 

 considered. 



1 



