BURIED PROPAGULE BANK OF A HIGH SUB-ALPINE SITE - MICROSITE VARIATIONAND COMPARISONS WITH ABOVEGROUND VEGETATION

We assessed the composition and spatial pattern of the persistent buri ed propagule bank (seeds and vegetative structures) of a treeline site in the Oregon Cascade Mountains. We monitored emergence from soil cor es removed from four microsite types and recorded vegetation cover and seedling abundance on the site. Over 3 100 seedlings/m2 emerged from the greenhouse soil cores; the seed bank was dominated by Juncus speci es. Few vegetative sprouts emerged. Vegetated microsites produced sign ificantly more emergents than did bare soils, but even bare soils cont ained abundant seeds. Overall site cover was low and few seedlings occ urred on the site. Discrepancies between aboveground and belowground a bundance were common. Phyllodoce empetriformis and Luetkea pectinata w ere abundant in the vegetation and produced many seeds but were poorly represented in the seed bank and as seedlings on the site. Other spec ies were abundant in the seed bank, but rare in the vegetation. Our re sults indicate that despite the abundance of seeds in bare soil, colon ization is likely to be extremely slow.