United States 

 Department of 

 Agriculture 



Forest Service 



Intermountain 

 Forest and Range 

 Experiment Station 

 Ogden, UT 84401 



Research Paper 

 INT-296 



Influence of Tree and 

 Site Factors On 

 Western Redcedar's 

 Response to 

 Release: 



A Modeling 

 Analysis 



Russell T. Graham 



INTRODUCTION 



Western redcedar [Thuja plicata Donn.}, occupying 

 approximately 330,000 acres (133 500 hectares), with a 

 total live volume of 10 billion board feet (Bolsinger 

 1979). is one of the more important commercial species 

 in the Northern Rocky Mountains. The natural durabil- 

 ity and good wood working properties of western red- 

 cedar make it desirable for use by the building indus- 

 try. Because of its natural resistance to decay, western 

 redcedar is ideally suited for use as posts, poles, shakes, 

 shingles, and for siding. In recent years the demand for 

 split products and lumber has caused large price in- 

 creases for western redcedar. In western Washington 

 and northwestern Oregon, western redcedar log prices 

 increased from $57.30 per thousand board feet in 1965 

 to $320.80 per thousand board feet in 1977 (Bolsinger 

 1979) and continued to show an increase in current 

 markets. Of the estimated 950 million board feet of 

 western redcedar harvested between 1975 and 1976, 

 66 percent consisted of trees that were 21 inches (53.3 

 cm) diameter at breast height and larger (Bolsinger 

 1979). 



Western redcedar in the Northern Rocky Mountains 

 grows on many different sites where it occurs as a 

 climax or accidental species on five different habitat 

 types (Daubenmire and Daubenmire 1968; Steele and 

 others 1976). Western redcedar is the major climax 

 species on the Thuja plicata/ Pachistima myrsinites, 

 Thuja plicata/ Athyrium filix-foemina, and Thuja 

 plicata/ Oplopanax horridium habitat types. On the 

 Tsuga heterophyla/Pachistima myrsinites habitat 



type, western redcedar is a minor climax species; it is 

 an accidental species on the Abies lasiocarpa/Pachis- 

 tima myrsinites habitat type. 



Western redcedar usually grows in association with 

 other tree species, such as western white pine (Ptnus 

 monticola Dougl. ex. D. Don). Douglas-fir {Pseudotsuga 

 menziesii [Mirb.] Franco), western larch (Larix occi- 

 dentalis Nutt.), grand fir (Abies grandis [Dougl.] Lindl.). 

 ponderosa pine (Pinus ponderosa Dougl. ex Laws.), 

 western hemlock (Tsuga heterophylla [Raf.] Sarg.), and 

 lodgepole pine (Pinus contorta Dougl.). Western 

 redcedar is one of the most shade-tolerant species grow- 

 ing in the cedar-hemlock ecosystems of the Northern 

 Rocky Mountains. It is capable of reproducing and 

 becoming established under the shade of faster growing 

 serai species. The prolific nature of its seed production 

 often leads to regeneration of thousands of seedlings 

 per acre, creating dense, overstocked, slow-growing 

 stands. 



Northern Idaho, eastern Washington, and western 

 Montana have large forested acreage in which western 

 redcedar is a major component of the understory. 

 Because western redcedar is shade tolerant, these 

 understory trees may be multiaged and diverse in size. 

 The question of how to manage these stands using 

 practices such as overstory removal, cleaning, weeding, 

 or thinning is becoming increasingly relevant. There- 

 fore, the objectives of this study were to identify the 

 tree, site, and stand characteristics that were associated 

 with the diameter increment responses of western red- 

 cedar to release from overhead and surrounding compe- 

 tition. 



I 



