RESULTS 



Annual Twig Production 



The response to topping was similar to that observed in earlier work (Ferguson 

 and Basile 1966). Twig production on the branches sampled increased severalfold the 

 first growing season after topping, then decreased each succeeding year (table 2). 



The data on inches of twig growth can be roughly converted to ovendry weight by 

 using a factor of 0.0809 pound per 1,000 inches of twig growth. This factor represents 

 the mean of 19,600 twigs collected from 1,490 shrubs in southern Idaho. By using the 

 mean shrub density (table 1) and the calculations of total twig growth per shrub, the 

 pounds of forage produced per acre can be calculated. Table 3 shows productivity per 

 acre (assuming either that all shrubs were untopped or that all were topped) and the 

 gain in pounds per acre that resulted from topping. 



Cost Per Acre 



The cost of topping a bitterbrush stand will depend on a number of variables: 



1. --Wages of personnel assigned to the work; 



2 . --experience of workers in the use of tools, particularly, the chain saw; 



3. --dependability of workers in doing assigned work efficiently and conscientiously; 



4. --density and size of overmature shrubs; 



5 . --roughness of the terrain; 



6. --availability of lightweight chain saws and protective apparel; and 



7. --distance to and from work. 



Interaction of the first five of the above factors is reflected in the data 

 shown in table 4 for the three sites treated in 1966. On the Modoc site, calculated 

 cost per acre was $18.56 when topping was done by chain saws and $33.50 when lopping 

 shears were used. Calculations included all costs charged to the project, including 

 travel time. In this case, saws and protective apparel were available. If $3.75 per 

 man-hour is used as a reasonable wage, topping could cost from $20.62 to $35.62 per 

 acre when lopping shears are used. If chain saws are employed, topping could cost 

 from $9.00 to $21.00 per acre. Most likely, the cost per acre will depend primarily 

 upon the worker's skill in handling and servicing equipment and upon the density of 

 shrubs to be cut. 



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