Seed germination, seedling demography, and growth of Salix setchelliana on glacial river gravel bars in Alaska

Abstract

This study examines the recruitment from seed of Salix setchelliana Ball, a prostrate clonal willow, which grows in the gravel-bar habitat of glacial rivers in Denali National Park, Alaska. Seeds of this species did not exhibit any dormancy. Under laboratory conditions, seeds moistened immediately after collection showed 100% germination, and percent germination decreased with an increase in the length of dry storage. Since summer precipitation is generally frequent in this region, this is probably not a factor limiting recruitment. Most seedlings observed in the field were located on gravel bars with greater plant cover, as opposed to those with sparse plant cover. The survivorship of seedlings over their first winter averaged 11%; in comparison, yearly survivorship in years 1–6 averaged 69%. The most likely cause of mortality was insufficient carbohydrate accumulation. Seedling leaf area differed between years and locations. An inverse relationship was found between leaf area and age-class for seedlings of younger age-classes. Key words: alpine, clonal, recruitment.