Assessing the role of seed banks and fire in the restoration of coastal prairie

Changing the fire regime of a plant community can result in significant alterations to its structure and composition. Seed banks have the potential to increase a population's ability to survive in areas where fire regimes have been altered by fire-suppression practices and, therefore, to preserve a community similar in composition to the original one. This study attempted to assess the potential contribution of the seed bank in restoration efforts utilizing either prescribed burning or logging of a historic coastal prairie community whose fire regime has been altered. To assess the role of seed banks and fire, mineral soils from two horizons were exposed to a burn and control treatment and germinated in the greenhouse. Compositional differences between the seed bank and aboveground vegetation were found within prairie, baccharis, alder, and Sitka spruce vegetation types. Compositional differences within the seed bank were found in both soil horizons and in both the burn and control treatments for all but the prairie vegetation type. The richness of the Sitka spruce forest seed bank appeared impoverished. Burning the seed bank created differences in the abundance of numerous native and non-native species, but did not significantly influence the richness of native or non-native plant assemblages. Plant species germinating from the seed bank after burning had no tendency to be native or non-native compared to those germinating without burning. Regardless of the treatment, the majority of the seed bank germinants were not native coastal prairie species and therefore the seed bank cannot be relied upon as the sole source of these types of plants. Colonization from on-site residual individuals and natural dispersal of propagules from nearby populations will likely contribute to overall site restoration.