The effects of disturbance on marsh seed banks

Abstract

Seed numbers and the species composition of seed banks (germinable seeds) from a marsh adjacent to the Great Salt Lake were compared among five vegetation types prior to a drawdown, during a drawdown, and prior to fire, after fire, and after restoration of normal water levels. Substrate samples were processed in the greenhouse under submersed and moist soil treatments to simulate the two germination conditions found in the field. After the fire, seed movement into the different vegetation types was also estimated. Numbers of germinable seeds were not depleted during the drawdown, possibly owing to increased salinity and the presence of standing vegetation. Fire had little effect on seed banks and subsequent seedling response. In general, seed banks were not affected by disturbance (e.g., burning, drawdown). The movement of seeds into the different vegetation types indicated that seed ingress could be important when one considers potential vegetation change. Seed banks of open water sites contained few germinable seeds when compared with Scirpus lacustris, S. maritimus, Distichlis spicata, and Typha spp. sites. Open water sites were devoid of vegetation and had few physical barriers, and seeds continued to move (air, water) across these areas until a barrier was reached, e.g., sites with vegetation.