Native Shrubs: Suitability for 

 Revegetating Road Cuts in 

 Northwestern Montana 



Roger D. Hungerford 



INTRODUCTION 



Constructing roads to harvest timber or explore for 

 minerals creates problems ranging from slope erosion 

 and stream siltation to loss of scenic value. Rcvegetation 

 can eliminate or reduce these problems. Many road 

 cuts on National Forests in the Northern Region of the 

 U.S. Department of Agriculture, Forest Service are 

 seeded with grasses and legumes to aid revegetation. 

 Fill banks respond well to this treatment, but harsh 

 sites and cut banks usually remain barren. In these 

 problem areas, planting appropriate shrubs and forbs 

 can accelerate revegetation. 



The use of shrubs for revegetation is not new. In the 

 1930's Juhren successfully used them for soil stabiliza- 

 tion on slopes in California (Gallup 1974). Plummcr 

 (1970) reported on plants for revegetating road cuts in 

 the Intermountain area (Utah, Nevada, and southern 

 Idaho). Several species of shrubs have been tested for 

 revegetating winter game ranges in southwestern Idaho 

 (Holmgren 1954; Medin and Ferguson 1980). Plummer 

 and others (1968) also used shrubs to restore big game 

 habitat in Utah. 



The purpose of this study was to evaluate the use of 

 shrubs and forbs native to northern Idaho and western 

 Montana for revegetation along western Montana road 

 cuts. Eighteen species were chosen based on previous 

 research results and each plant's potential for soil 

 stabilization, availability, and survivability. The primary 

 objective was to evaluate survival capability and soil 

 stabilization potential of the planted shrubs and forbs 

 on road cuts. A second objective was to evaluate shrubs 

 and forbs together with a locally used grass and legume 

 seeding mixture for revegetation effectiveness. Survival 

 data 4 years after planting are presented and effectiveness 



for site stabilization is discussed by species. Interactions 

 between shrubs and forbs and grasses and legumes are 

 discussed. 



STUDY AREA 



An effort was made to conduct the study in repre- 

 sentative areas along forest roads. Test sites were located 

 on the Coram Experimental Forest (fig.l) along two 

 logging roads: a new road and a 20-year-old road with 

 unvegetated cut slopes. Douglas-fir/ninebark (Pseudot- 

 suga menziesiil Physocarpus malvaceus) and subalpinc 

 fir/queencup beadlily (Abies lasioearpalClintonia unif- 

 lora) habitat types are predominant in the study area. 

 The area ranges in elevation from 4,200 to 5,200 feet 

 (1 280 to 1 585 m) and receives an average of 33 

 inches (84 cm) of precipitation annually. 



Approximately 3,700 feet (1 128 m) of road cuts 

 were selected for planting on south, east, and west 

 slopes. Cut bank slopes of Va:\, and a terraced 



cut through fractured rock were planted. Slope distances 

 (from road to top of cut) varied from 10 to 70 feet (3 

 to 21 m). Soils along the cut banks are weathered limes- 

 tone and calcareous argillites, with a pH of 7.0 to 8.0 

 (Klagcs and others 1976). Subsoils (from the B and C 

 horizons) and fractured rock range in depth from to 

 4 feet (0 to 1.2 m) below the undisturbed surface. Soil 

 structure varies from weak, fine, subangular blocky to 

 massive, with 20 to 80 percent rock. Soil texture varies 

 from gravelly, silty clay loam to gravelly silt loam. 

 The soils in the study area are characterized by a low 

 organic content (0.6 to 1 .4 percent) and a cation ex- 

 change capacity (CEC) of 8.2 to 19.6 meq/100 g. Soils 

 contain from 0.03 to 0.07 percent total nitrogen and 

 3.8 to 28.0 ppm available phosphorus. 



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