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Vegetation response to right-of-way clearing procedures in coastal British Columbia McGee, Ann Bradshaw


This research was designed to assess the response of the flora of forested sites to the methods employed by B.C. Hydro and Power Authority for the initial clearing of transmission line rights-of-way in coastal British Columbia. Seven immature forest vegetation units adjacent to, and seven early seral vegetation units on, the transmission line rights-of-way were identified. The environmental parameter most highly correlated with both the immature forest and early seral vegetation units was slope position. The degree of disturbance (clearing standard) and seeding with agronomic grass and legume species complicated the determination of relationships between immature forest and early seral vegetation units. The majority of seeds (72%) in the forest samples was found in the forest floor layer. Twenty-one percent of the germinable seeds were found in the 0-5 cm layer of the mineral soil, and 7% were found in the 5-10 cm layer. Fewer germinable seeds were found in samples from drier than from moister vegetation units, regardless of disturbance level. Seed bank samples from high-disturbance sites had the fewest germinable seeds, primarily because the forest floor had been removed. The seed rain was dominated by tree species within the forests, and shrub and herbaceous species on the rights-of-way. The seed rain was greater, and percent germinability was higher, in the second year than in the first. Important species vegetatively invading after, or recovering from, plot scarification, included Gaultheria shallon, Pteridium aquilinum, and Rubus ursinus. Successful seedling establishment was rare: only Alnus rubra, Anaphalis marqaritacea, and Rubus spp. seedlings were observed in significant numbers, but few of these survived to the next year. In order to be successful in managing vegetation to meet transmission line right-of-way (or tree production) goals, more attention must be paid to the biology and reproductive ecology of pest and acceptable/crop species. If the field of vegetation management is to change from a corrective to a preventive focus, this attention, and information,' is crucial.

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