Ministry of Forests

Cariboo Region Research Section

Grass and Legume Seeding for Vegetation on Blade Scarified Sites in the ICH and ESSf Zones in the Centeral Interior of British Columbia


Competing shrub and herbaceous vegetation is a principal obstacle to successful reforestation of moist, backlog brushfields in the Interior Cedar Hemlock (ICH) and Engelmann Spruce Subalpine Fir (ESSF) zones. Treatments to control the competing vegetation are usually necessary before crop trees can be successfully established. Herbicide application is a potentially effective tool to reduce the vegetation competition, but may be unacceptable for sites where it affects water quality or wildlife resources. An alternative vegetation management option for these sites may be mechanical clearing of vegetation followed by seeding of low growing grasses and legumes to reduce native vegetation regrowth.

Seeding of low growing grasses and legumes on mechanically prepared or broadcast burned sites has been used as a vegetation management tool in the U.S. Pacific Northwest since the mid-1 970's (G. Klingler, USDA Forest Service, pers. comm., Sept. 1989) and in the Horsefly Forest District in the Interior of British Columbia since 1983 (D. Trigg, B.C. Min. For., Horsefly For. Dist., pers. comm., 1987). Although effects of grass/legumeseedingonvegetationregrowthandcroptreeperformancehavebeendocumentedintheU.S.,1 no long-term studies have been conducted in the British Columbia Interior. Matters that need to be addressed include: the effectiveness of grass/legume seeding on the re-establishment and growth of native species; the effects of seeded species on the performance of crop trees; and the effects of this treatment on long-term site productivity, resource values, and timber production.

The overall objectives of this project are to evaluate and dernonstrate the effectiveness of grass/clover seeding for controlling the regrowth of native competing vegetation and for establishing a free-growing crop tree plantation on moist, blade scarified sites in the central Interior of British Columbia. This is a preliminary, exploratory project.

This project, initiated in 1988 in the Horsefly Forest District, has two parts. Part 1, conducted in 1989, is a retrospective survey of all sites operationally seeded before 1987. The survey documented vegetation cover as well as stocking and growth of planted crop trees on 11 sites. Part 2 is a research and demonstration trial. Seeded and unseeded treatments were established on three mechanically scarified backlog sites, including one in the ESSF and two in the ICH zones. All sites in this trial were seeded with the same seed mix and seeding rate, at the same time of the year (fall) . The effects of broadcast fertilizer application on establishment and growth of seeded grasses and clovers were also assessed.

Results of the retrospective survey are summarized in Section 3; the first- and second-year results of the research and demonstration trials are described in Section 4; conclusions are contained in Section 5. A brief summary of some previous studies on grass/legume seeding for vegetation management is contained in the following section.

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