METHODS 



We repeated the scalping test on three aspects (north- 

 east, southeast, and northwest) within the study area. 

 Test sites on the northwest and southeast sites were 

 fenced to exclude sheep grazing. The northeast site was 

 left unprotected in order to determine effects of sheep 

 grazing. We used a completely randomized block 

 experimental design with five blocks on each aspect. We 

 conducted 3X3X3 factorial analysis of variances for sur- 

 viving trees, gopher-caused mortality, and height growth 

 (measured from the ground to the top of the terminal 

 bud or tallest lateral if no terminal) after the fifth grow- 

 ing season. Where significant differences were revealed, 

 we did multiple comparisons of means using the studen- 

 tized maximum modulus (Gabriel 1978). 



Each block contained three experimental units (scalp- 

 ing treatments); each unit was 120 ft (37 m) long. One 

 unit consisted of a single row of 2- by 2-ft (0.61- by 

 0.61-m) hand scalps spaced 4 ft (1.2 m) apart from center 

 to center. Ten trees each of Douglas-fir, ponderosa pine, 

 and lodgepole pine were planted in the scalps. The order 

 of the species in the first three scalps was determined 

 randomly. The same order was repeated in each subse- 

 quent group of three scalps. A second unit contained 

 two rows of 4- by 4-ft (1.2- by 1.2-m) scalps made by a 

 hydraulically operated 4-ft blade mounted on the rear of 

 a small tractor. The two rows were 8 ft (2.4 m) apart 

 with 8 ft between scalp centers within a row. The third 

 unit was one row of trees planted 4 ft apart down the 

 middle of an 8-ft-wide dozer-scalped strip. The three spe- 

 cies were planted in the 4-ft scalps and dozer strips in 

 the same alternating pattern described above for the 2-ft 

 scalps. Each experimental unit contained 30 planted 

 trees, 10 of each species. All three site preparation treat- 

 ments removed up to 6 inches (15 cm) of topsoil from the 

 immediate vicinity of the planted trees. 



Trees (2-0 stock) were planted in spring 1975. Roots 

 were pruned to 12-inch (30-cm) length at Lucky Peak 

 Nursery and relatively uniform-sized trees of each spe- 

 cies were selected for the study. The trees were hand 

 planted in auger holes. The initial height of each seed- 

 ling was measured and recorded as well as the height at 

 the end of each of the first five growing seasons. Mortal- 

 ity was determined each year and the likely cause of 

 death recorded. 



The unfenced area on the northeast aspect was lightly 

 grazed by a herd of 2,800 sheep once during the second 

 growing season (1976). Again in the third growing sea- 

 son (1977), a herd of 2,865 sheep grazed through the 

 unprotected blocks of the study. This time the grazing 

 was slower and heavier. Finally, the unfenced blocks 

 were very heavily grazed for a few hours in the fifth 

 growing season (1979) by 2,074 sheep. Visible damage to 

 seedlings caused by sheep was recorded in 1976, the first 

 year of grazing, and each of the subsequent 4 years. 

 (Erosion is not expected to be a problem with any of the 

 three treatments. The 2-ft scalps have the least potential 

 for erosion.) 



We did not use an unscalped control plot because after 

 two plantation failures it was apparent that the site 

 required site preparation in order to establish tree see- 

 dlings. The 2-ft scalp was accepted as the standard for 

 comparison. 



RESULTS 



At the end of the first five growing seasons, we 

 gathered data on survival and mortality and on height 

 growth and frost damage. 



Survival 



The 86 percent survival rate of the lodgepole pine was 

 significantly greater than the 73 percent survival for 

 ponderosa pine at the 95 percent level of confidence 

 (table 1). In turn, ponderosa pine survival was signifi- 

 cantly greater than the 65 percent survival of Douglas- 

 fir. Survival of all species on the 2-ft (0.61-m) scalps was 

 61 percent, significantly less than on 4-ft (1.2-m) scalps 

 (80 percent) and on dozer strips (83 percent). We found 

 no significant difference in survival between the three 

 aspects. 



The difference between survival on the 2-ft scalps and 

 the other two site treatments has widened each "year 

 since planting (fig 3). When the three species were com- 

 bined, average first-year survival ranged from 95 percent 

 in the 2-ft scalps to 98 percent on the dozer strips. At 

 the end of the fifth year, average survival ranged from 

 63 percent on the 2-ft scalps to 82 percent on the dozer 

 strips. For nearly all nine combinations of species and 

 site preparation, the mortality rates declined sharply 

 during the fifth growing season. 



Table 1.— Fifth year survival and mean height of surviving 

 trees 



Tree species 

 and 



treatment 



Survival 



Height 





Pet 



cm 



Douglas-fir 







2-ft scalp 



49a 1 



20.2a 



4-ft scalp 



69bc 



21.9a 



dozer strip 



77bcd 



24.7ab 



species total 



65 



22.3 



Ponderosa pine 







2-ft scalp 



59ab 



20.8a 



4-ft scalp 



80cd 



29.6bc 



dozer strip 



81cd 



32.0cd 



species total 



73 



27.5 



Lodgepole pine 







2-ft scalp 



75bcd 



26.4abc 



4-ft scalp 



91d 



36.1de 



dozer strip 



92d 



39.9e 



species total 



86 



34.1 



1 Means followed by the same letter are not significantly different, 

 a = 0.05. Mean comparisons methods according to Gabriel (1978). 



3 



