Germinable Seed Banks of Interior Alaskan Tundra

Abstract

Germinable seed numbers in the surface soil were estimated across three snowbank gradients in montane tundra of interior Alaska. Vegetation, productivity, and disturbance change with distance across these gradients. Seed densities are in the range 500 to 1800 seeds m^-2 in the upper 5 cm of soil. An earlier study in Eriophorum tussock tundra nearby revealed over 2000 seeds m^-2 in the upper 5 cm of soil. These results show that tundra seed banks (and presumably seed rain) are relatively larger than expected. Published reports do however suggest that seed bank size decreases with latitude in montane grassland, heath and tundra vegetations. Contrary to published theories, there was no significant relation between seed bank size and disturbance. Seed bank size increased with above ground vascular plant productivity. This is most simply explained by the conjecture that reproduction and seed rain increase with productivity. The relative abundance of graminoids in the seed bank is higher (and that of dicots, less) than what would be expected from their relative cover in the vegetation.