METHODS 



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The purpose of topping is to stimulate profuse twig growth from live branches 

 below the level at which the old shrub is cut off. The treatment was applied only once, 

 and the magnitude of twig production assessed following each of the subsequent four 

 growing seasons. 



Figures 1 through 3 illustrate the three study areas and table 1 tabulates de- 

 scriptive information about them. The overmature bitterbrush shrubs (those that have 

 reached an age at which annual twig production is small compared to that of young 

 shrubs) were slightly larger in height and canopy spread on the Boise site than on 

 either of the other study sites. Shrubs on the Modoc area tended to branch more from 

 the base and, on the whole, were more vigorous. Many of the old shrubs on the Sawtooth 

 area were of small stature, possibly because they were growing along a ridge site. 



Topping was accomplished the last week of March 1966 on the Boise and Sawtooth 

 sites, and during the third week in April on the Modoc. Treatment was completed before 

 flower buds developed. (New twig growth does not begin on bitterbrush until the flower- 

 ing stage is nearly complete.) Approximately 10 acres were treated at each site. 



Each study area was divided into four sections. Lightweight, direct drive chain 

 saws were used on two sections and lopping shears on the alternate two sections. 

 Overmature shrubs, 5 to 7 feet tall, were cut off 3 to 4 feet above the ground. Smaller 

 overmature shrubs, more common on the Sawtooth site, were cut so as to remove about one- 

 half of the canopy volume. All shrubs were cut on a horizontal plane through the canopy. 



Prior to topping, 20 shrubs were chosen at random from the stand on each study 

 area. These old shrubs were randomly divided and assigned to either the topped or the 

 control shrub group. The topped shrubs were cut at the time the stands were treated. 

 All sample shrubs were marked by numbered alumintim tags and plastic flagging. Follow- 

 ing topping, a complete count was made of all shrubs on each study area. 



At the end of each growing season (1966 through 1969), all annual twigs 0.2 inch 

 long or longer were measured on two branches of each sample shrub. Measurements were 

 started at a point where the diameter of the branch was approximately 1 inch. These 

 branches had also been selected and tagged prior to topping to preclude bias in their 

 selection. The same branches were remeasured each year, unless flagging and tags had 

 been torn off by deer or a branch had died. In these few instances, new sample 

 branches were chosen. 



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