SEED BANKS OF FORESTED AND DISTURBED SOILS IN SOUTHWESTERN BRITISH-COLUMBIA

The species composition and density of seed banks in the forest floors and mineral soils of several undisturbed (immature, midseral forests) and disturbed (transmission line rights-of-way) ecosystems in southwe stern British Columbia were estimated using the seedling-emergence met hod. The total soil surface area sampled was 9.4 m(2). Germination beh aviour of seven dominant species in response to depth of burial and su bstrate was also studied in a greenhouse experiment. A total of 16 289 seedlings germinated, representing 62 native and naturalized vascular plant species and several unidentified grass species. Most seedlings emerged from the forest floor, and the number of germinants generally decreased with increasing sample depth. Drier ecosystems had the lowes t number and density of germinants. Burial depth significantly affecte d germination of all species tested. Mineral soil was equal, or superi or, to forest floor as a germination substrate for all species tested. Depth - substrate interactions for several species indicated that the pattern of influence of burial depth in relation to substrate varied with species. Caution is urged extrapolating greenhouse seed-bank stud ies to potential weed populations in the field. Establishment of speci es from the seed bank will be a function of the depth to which the soi l is disturbed and the kind of disturbance (burning, scarification) im posed.