VOLUME /A. (M.cu.ft.) 



ABOVE BELOW 



F-iguve 3. — Total stand volume by zones in relation to distance from the road. 

 (Zones connected by brackets are not significantly different ^ P <0.05.) 



Because the "edge effect" appeared negligible beyond 22 feet from the road, the 

 plots were divided into three equal 22-foot zones for analysis of volume. Above- and 

 below-road plots were analyzed separately using 6 plots and 3 zones for each test. 

 An orthogonal individual degree-of-freedom test was employed to test for significant 

 differences between zones. 



Volume in the roadside zone of below-road plots was significantly greater than 

 in the two zones within the stand (figure 3) . Roadside volume appeared greater in 

 above-road plots, but was not significant. By pooling the data for above- and below- 

 the-road plots, the total effect on utilization of road area can be determined and the 

 significant additional volume growth (130 percent of that within the stand) is apparent 

 (figure 4) . 



The average distance (road width plus cut width) was 18.5 feet. The increased 

 volume in roadside zones was sufficient to compensate for 13.1 feet of this distance, 

 leaving 5.4 feet of unproductive road area. With an average space of 400 feet between 

 roads, the unproductive road area would convert to only about 1.4 percent of the 

 total area. 



The miscellaneous plots on the Coeur d'Alene and Kaniksu National Forests showed 

 the same trend of increased growth adjacent to the road with a magnitude of response 

 very comparable to Cathedral Peak. Data from the Brett Creek plots were highly variable 

 because of heavy blister rust mortality. Volume above the road appeared unaffected, but 

 in contrast to the other plots, growth of below-road border trees was slightly dimin- 

 ished. However, this stand was established after the road was built and the trees were 

 not planted to fully utilize the road opening in much of the area. On 2 of the 3 below- 

 road plots the closest border tree was 10 feet from the edge of the road. This 10-foot 

 space was occupied by dense shrubbery evidently negating a potential growth response of 

 border trees. 



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