Control of competition from sedge and grass is often 

 necessary for a successful plantation. But how large is 

 the vegetation-free area needed by each tree to assure 

 survival and a reasonable rate of growth? 



According to Gutzwiler (1976), the primary considera- 

 tions in determining the minimum effective size of 

 cleared spots are the condition of the forest floor and the 

 rooting characteristics of existing vegetation. When 

 vegetation completely occupies a planting site, scalp size 

 and depth must be increased in order to prevent compe- 

 tition from underlying roots. Lotan and Perry (1983) say 

 that scalps must be a minimum of 18 inches by 18 inches 

 (46 by 46 cm), and on droughty sites they should be 

 larger. Stewart and Beebe (1974) found no significant 

 increase in second-year ponderosa pine survival when 

 they compared 2-ft (0.61-m) scalps to no site preparation 

 in hard fescue and pinegrass on two different soils of 

 central Washington. Heidmann (1963) tested scalp sizes 

 on an Arizona site covered with mixed grasses consist- 

 ing mainly of mountain muhly and Arizona fescue. He 

 found that scalping as opposed to no site preparation 

 significantly increased survival of ponderosa pine. How- 

 ever, survival differences between scalp sizes of 16-inch 

 (41-cm) diameter, 26-inch (66-cm) diameter, and complete 

 removal of all vegetation on the plot were not statisti- 

 cally significant. 



Hall (1971) found that ponderosa pine seedling sur- 

 vival 5 years after planting was higher on 4-ft (1.2-m) 

 scalps than on 2-ft or 6-ft (0.61-m or 1.8-m) scalps in cen- 

 tral Idaho. Slit scalps 1.5 to 2 ft (0.46 to 0.61 m) long 

 and 6 to 10 inches (15 to 25 cm) wide have sometimes 

 been successful on pumice soils of central Washington 

 (Stewart 1978). Loewenstein and others (1968) showed 

 that scalping increased first-year ponderosa pine survival 

 dramatically, but differences in survival between see- 

 dlings on scalps of 1, 3, and 5 ft (30, 91, or 152 m) were 

 small. However, favorable moisture conditions through- 

 out the season may have been partially responsible for 

 the lack of significant differences. Larson and Schubert 

 (1969) recommend that in order to establish ponderosa 

 pine in the Southwest, grass must be killed or removed 

 from the site before trees are planted. 



Miller and Brewer (1984) found that, in northern 

 Idaho, dozer scarification significantly reduced 3-year 

 height growth of containerized Douglas-fir compared to 

 no treatment where competing vegetation was light and 

 first-year precipitation was above normal. Lotan and 

 Perry (1983) maintain that discontinuous furrows or 

 scarified strips are preferable because animals will use 

 continuous strips as walkways. 



This paper contains the results of a 5-year study com- 

 paring Douglas-fir, ponderosa pine, and lodgepole pine 

 [Pinus contorta var. latifolia Engelm.) survival and 

 height growth after planting in three sizes of hand-made 

 and machine-made scalps. Though competition may also 

 be reduced by other means such as spot applications of 

 herbicides, this study involved only mechanical scalping. 



STUDY SITE 



The study site was within a large clearcut in the 

 Grouse Creek drainage on the Mountain Home Ranger 



District of the Boise National Forest. Characterized by 

 strongly dissected faulted bench land, Grouse Creek is in 

 the southern part of the Idaho batholith. Well-drained, 

 gravelly sandy loam skeletal soils of granitic genesis pre- 

 dominate. The amount of soil moisture available to 

 young trees depends largely on summertime precipita- 

 tion. The site is approximately 6,000 ft (1 830 m) in ele- 

 vation and is a Pseudotsuga menziesii/Berberis repens 

 habitat type (PSME/BERE; Douglas-fir/Oregongrape) 

 (Steele and others 1981). 



The PSME/BERE habitat type occurs mainly in south- 

 eastern Idaho and adjacent Utah, and extends into 

 southern portions of central Idaho. The elk sedge phase 

 of this type occurs mainly in the southern batholith sec- 

 tion in central Idaho. 



This habitat type has moderate to high timber yield 

 capability (Steele and others 1981). It occupies a variety 

 of aspects at lower to midelevations— 4,500 to 7,700 ft 

 (1 370 to 2 350 m)— of the forested zone. Usually 

 Douglas-fir is the only tree species that grows on these 

 sites, but in the elk sedge phase ponderosa pine is a 

 major serai species within its elevational range. Lodge- 

 pole pine is an associated species in some areas. 



The Grouse Creek study area has gently rolling topog- 

 raphy with slopes generally less than 30 percent. Cold 

 air appears to drain less rapidly here than in other areas 

 of similar elevation, and extremes in temperature may be 

 a major hinderance in regenerating Douglas-fir, esper 

 cially in a large clearcut. 



Coverage of elk sedge was estimated on 10 randomly 

 located 4-milacre plots on each aspect of the study area. 

 Coverage ranged from 10 percent on areas greatly dis- 

 turbed during logging to 65 percent on areas with mini- 

 mal disturbance. The average for each aspect was 

 between 35 and 40 percent (fig 2). 



Clearcuts in the area have been heavily grazed by 

 sheep each year since logging in the early 1960 's. 

 Douglas-fir has been planted twice on the site with little 

 success. Seven years separate the last planting and the 

 beginning of this study. 



Figure 2.— Grouse Creek study site with typi- 

 cal ground coverage of elk sedge. 



2 



