Role of the seed bank in providing colonizers on a tundra disturbance in Alaska

Abstract

Numbers of germinable seeds in soils from four undisturbed communities at an Alaskan Arctic Coastal Plain site ranged from 70 to 600 m −2 and numbers of distinct taxa were two to nine. Stratified soils contained more germinable taxa than unstratified soils, suggesting that seed banks in Alaskan tundra are more diverse than shown by earlier studies using unstratified soils. In contrast to temperate seed banks, which often contain early successional species no longer present in the vegetation, all seed bank taxa at this site occur within a short distance of the sample sites because of long persistence of the communities. Of the common colonizers on a nearby 30-year-old disturbance, Betula nana, Poa arctica, Salix spp., and Arctagrostis latifolia are absent or present in only small amounts in the seed bank and apparently colonize mainly from seeds dispersed following disturbance. Eriophorum angustifolium, another common colonizer, is present in the seed bank of wet areas and Carex bigelowii and C. aquatilis are abundant in the seed bank of several communities. Germination from the seed bank is an important means of colonizing disturbances for these taxa. No trend in seed bank size with intensity of disturbance (cryoturbation) was found, and comparison with other studies shows that seed bank size in Eriophorum vaginatum tussock tundra decreases with latitude.