A single vigorous shrub on the Boise site produced a large proportion (74, 36, 

 and 52 percent) of the total growth measured on the control shrubs for the years 1967, 

 1968, and 1969, respectively. The large twig production of this one shrub resulted in 

 a large statistical variance for control shrubs each year, and was responsible for the 

 failure to find significant differences between topped and control shrubs, 



Retc^ping 



In an earlier report by Ferguson and Basile (1966), the effects of topping were 

 based upon the response of 15 topped and 15 untopped shrubs. Topping was accomplished 

 the spring of 1960. Since 1963, occasional observations and several photographs have 

 been made of these shrubs, but no quantitative data have been obtained. In March 1966, 

 eight of the original topped shrubs were topped again. The new cutting was about 5 

 inches above the level of the original cut. During the suiraner of 1966, the retopped 

 shrubs exhibited a flush of new twig growth similar to that which occurred after the 

 first topping 6 years earlier. Figure 4 shows one of these retopped shrubs in the 

 autumn of 1967, two growing seasons after retopping, and in July 1970, five seasons 

 after retopping. 



Longevity Following Topping 



Periodic observations of the 30 shrubs involved in the 1960 trial disclosed that 

 by July 1970 only one shrub (untopped) had died. The estimated percent dead canopy 

 averaged 22 percent for topped shrubs and 33 percent for untopped shrubs. Thus, top- 

 ping does not appear to decrease longevity of old shrubs. 



Seed Production 



Because topping removes one-third to one-half of the canopy from each shrub, cut- 

 ting unquestionably decreases the production of seed from an old stand- -and older 

 bitterbrush shrubs often produce the largest quantities of seed. This decrease in seed 

 production is most pronounced the first growing season after topping. From the second 

 season on, seed production should increase rapidly, as flower buds are formed on 

 branch wood . 



Damage by Insects and Disease 



There is a possibility that wounds caused by topping serve as entrance points for 

 disease, or attract wood-destroying insects. During this 4 -year study on the Boise, 

 Modoc, and Sawtooth sites, we observed no evidence that topping encouraged either 

 disease or insect damage. 



Safety Precautions 



The use of chain saws requires some safety precautions. Chain saw users should 

 always wear protective chaps , ^ goggles, and sturdy gloves. Cutting with the top of 

 the chain, instead of the bottom as one would be inclined to do, causes most of the 

 debris to be thrown away from the sawyer, and also keeps the chain sprocket clean. 



■^USDA Forest Service. Chaps, protective (for chainsaw operator), specification 

 6170-4a, 20 p. Northern Region, Missoula Equipment Development Center, Missoula, 

 Montana. 1971. 



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