Crownvetch.--Cover of this perennial species increased steadily after the first growing season and averaged 93 percent during the ninth growing season. Moreover, this was the only species to spread from all original plots. Although crownvetch was initially slow to cover the plots at Steelhead Creek and Acker Rock, it attained nearly complete coverage by the 9th year (fig. 4). Fertilizer apparently provided little increase in final stocking or stand height; however, the chlorotic unfertilized stand at Acker Rock contrasted sharply with the dark green of both fertilized plots. The three varieties of crownvetch adapt to a wide range of site conditions (McKee 1964, McKee and Langille 1967). Crownvetch is frequently used to revegetate cut and fill slopes along highways and mine spoils in the East and Midwest. Although crownvetch can penetrate imperfectly drained, heavy clay soils, it generally is less effective than birdsfoot deervetch (trefoil) on imperfectly or poorly drained soil (Hawk 1964, Waddington 1968). Crownvetch grows well in medium shade of Eastern conifers and deciduous trees; however, it grows best in full sunlight and poorly in full shade.2/ Root growth is affected more by shaded conditions than is top growth (Langille and McKee 1970). Local experience with crownvetch is limited and generally unsuccessful. Dyrness (1967) sowed inoculated seed of the "Emerald" variety in both fall and spring on a compacted landing at 520-m elevation in the western Cascade Range. Although seed germination was good to excellent, mortality was high during the next growing season and winter; final survival and vigor were poor. The Soil Conservation Service has had little success with crownvetch in the Northwest.3/ Although crownvetch is not listed as a suggested species to control erosion along forest roads in Oregon (Berglund 1976), our observations justify new interest. Birds foot deervetch (trefoil).-The average cover of birdsfoot declined from 65 percent after the first growing season to 25 percent by the ninth growing season; this perennial species spread about 1 m beyond the original plots. Fertilization had no consistent effect on either foliage cover or plant height. Dyrness (1967) reported good to excellent germination and initial establishment at his test location in the Coast Ranges and at one in the western Cascade Range; however, final stocking was seriously reduced by frost heaving. In contrast, Klock et al. (1975) observed no emergence of fall-sown birds foot at 2written correspondence with Fred V. Grau, President, Grasslyn Company, College Park, Maryland, on January 5, 1965. 3Personal correspondence with Jack R. Carlson, Plant Material Specialist, Soil Conservation Service, Spokane, Washington, on June 5, 1978. four locations in the cooler, drier mountain slopes in north central Washington (900- to 2 100-m elevations). Birds foot is generally considered a longlived, winter hardy species adapted to subalpine conditions and annual precipitation between 460 and 1 500 mm (Berglund 1976). Our field trial supports this general observation. Wetland deervetch (big trefoil).--This perennial deervetch or trefoil performed poorer than birds foot in our trial. Survivors were present only at the more mesic Calf Creek location, where cover averaged about 30 percent. Fertilization had no apparent effect. Dyrness (1967) reported good initial survival and growth but much winter mortality at his location in the Oregon Cascade Range. The better performance reported for his Coast Ranges site and our findings are consistent with general recommendations to use this species where effective precipitation exceeds 1 524 mm (Berglund 1976). The Washington lupine.--Initial and final establishment of this perennial lupine was limited to Calf Creek and Acker Rock; no seedlings emerged at Steelhead Creek, probably because our late sowing was in a dry soil. 9-year-old plants were robuts (Fig. 5). Although some new plants developed from seed, they were few in number presumably because of seed depredation by birds or rodents. An auxiliary sowing on a highly compacted skid road at Acker Rock produced vigorous and persistent plants. This species has been used in Germany and elsewhere in Europe to improve nitrogen and organic conditions of raw humus soils (Miller 1964). Bitter-blue lupine.--No live plants of this annual were present after the first growing season. The original seedlings produced second generation plants at Calf Creek and Steelhead Creek, but Figure 5.--Nine-year-old Washington lupine and ponderosa pine at Calf Creek. not at Acker Rock. Seed produced by these plants was probably consumed by birds; thus, the complete dependence of this annual on seed propagation lowered its chances to produce a long-lived stand. Flatpea.--Initial and final establishment of this long-lived perennial was limited to Calf Creek; the few surviving plants appeared healthy but were confined to a single plot. Dyrness (1967) also reported poor germination at both his Cascade and Coast Ranges locations; however, his transplanted seedlings did well. Grunder and Dickson (1948) summarized the use and cultural practices necessary for flatpea in the Pacific Northwest. They stressed its slow early development but ability to compete with native vegetation. Hairy vetch. --This annual established itself initially at Calf Creek and Steelhead Creek and persisted there. Hairy vetch bested other species at both locations by spreading up to 8 m from the original plots; vigorous plants climbed and dominated associated vegetation. The effects of fertilization were indefinite. Effects of Fertilization In some species at some locations, the complete NPKS fertilizer applied at seeding time. apparently increased initial cover and plant vigor. Fertilization with nitrogen and phosphorous is generally assumed necessary for successful grass establishment along forest roads. of Oregon (Berglund 1976). Unexplainably, however, the effect of superphosphate was to reduce 1st-year foliage cover, especially of alfalfa. Suitability in Forest Management Some of these species could be used in forest management to stabilize soils disturbed by road construction or logging or to improve growth of associated trees. Characteristics of some species are desirable for both applications; others are not. For example, ease of initial plant establishment over a wide range of site conditions is desirable for stabilizing soil and improving growth of associated trees. Alfalfa, birds foot deervetch, and particularly crownvetch provided well-stocked stands at all locations when sown with 22.4 kg of seed per hectare. This was equivalent to about 939, 1,927, and 519 live pure seeds per square meter respectively, compared to 1,550 per square meter recommended for adequate erosion control along forest roads (Berglund 1976). Long-lived perennials are generally preferable to annuals whose performance depends on regular production, survival, and germination of seeds. of the eight legumes tested were perennial; the exceptions were the two annuals, bitter-blue lupine and hairy vetch. Of the three top performers, crownvetch was particularly well adapted. perennial legume normally seeds profusely and also spreads with new shoots from widely ramifying lateral roots.4/ Stems range from 0.6- to 1.8-m long and are strongly branched. Its deeply penetrating root system has numerous lateral roots (McKee 1964). Three of the legumes frequently dominated associated vegetation. This trait is more desirable for soil protection than for silvicultural uses, especially if legumes are admixed with seedlings during plantation establishment. Sowing crownvetch or climbing legumes like flatpea or hairy vetch under pole-sized trees, however, may be desirable to ensure competitiveness with natural vegetation. Finally, shade tolerance is another trait that influences species choice. If continued nitrogen fixation is desired, then the ability to grow well in the partial shade of other plants is essential. Crownvetch (McKee 1964, Hawk 1964), flatpea5/, and Washington lupine have this desired trait. Day, Paul R. 1956. Report of the Committee on Physical Analyses, 19541955, Soil Science Society of America. Soil Sci. Soc. Am. Proc. 20:167-169. Dyrness, C. T. 1967. Grass-legume mixtures for roadside soil stabilization. USDA For. Serv. Res. Note PNW-71, 19 p. Pac. Northwest For. and Range Exp. Stn., Portland, Oreg. Grunder, Maynard S., and Newell D. Dickson. 1948. Flat pea. Agric. Exp. Stn. Mimeogr. Circ. 104, 8 p. Puyallup. Hadas, A., and D. Russo. 1974a. Water uptake by seeds as affected by water stress, capillary conductivity, and seed-soil water contact. West. Wash. Exp. Stn., 1964. Soil requirements and Klock, Glen O., Arthur R. Tiedemann, and William Lopushinsky. 1975. Seeding recommendations for disturbed mountain slopes PNW-244, 8 p. Pac. Northwest Langille, Alan R., and Guy W. 1970. Early growth of crownvetch 1964. Geology of the central and northern parts of the United States Salinity Laboratory 1954. Diagnosis and improve ment of saline and alkali Waddington, D. V. 1968. Effects of soil drainage GPO 988-280 |