Relationship between vegetation and soil seed banks in an arctic coastal marsh

1 The effects of habitat degradation on the soil seed bank at La Perouse Bay, Manitoba are described. Foraging by lesser snow geese leads to loss of vegetation, coupled with changes in soil abiotic conditions and an increase in salinity. 2 The density of seeds and the relative abundance in the seed bank of species characteristic of undisturbed sites decrease following degradation, while the relative abundance of invasive species increases. Vegetation loss had the greatest impact on seed banks of stress-tolerant species and the least impact on species with many widely dispersed seeds. 3 The above-ground vegetation and below-ground seed bank were less similar in undamaged plots than in disturbed plots. In spite of the low degree of similarity, redundancy analysis of the data indicated that approximately half of the variation in the soil seed bank could be explained by the vegetation data and vice versa. 4 More recently degraded soils had richer soil seed banks than those from older disturbances. Site-specific factors not only influenced the species present but also the time lag between loss of vegetation and loss of the seed bank. Seed banks in these impacted and fragmented sites do not recover quickly. 5 Seed banks in sandy beach-ridges were less affected by degradation due to the greater proportion of ruderals present in the original vegetation and the absence of the high soil salinities that are characteristic of degraded salt-marsh soils.