The Extent and Role of Seed Dormancy in Alpine Plants

Seed dormancy is an adaptive mechanism of growth cessation which often confers upon some species a selective advantage in distribution and abundance. Although relatively few alpine species exhibit seed dormancy, the dominant or abundant species of most communities do so. The causes of seed dormancy in alpine plants appear to be as diverse and typical as for any other ecologic group. Seed coat inhibition is probably the most common cause of alpine seed dormancy. A requirement for pregermination chilling (stratification) or for after-ripening account for very little alpine seed dormancy. Of some 60 species investigated which set viable seed, 8 require scarification of the seed coat for germination, 3 require pregermination chilling, 2 require after-ripening, and 6 exhibit weak or vague photosensitivity. Data are inconclusive and fragmentary respecting the viability, germinability, and ripening of alpine seeds, primarily because of variation in latitude, altitude, and variable dates of collection. Consequently, natural germination requirements are known for relatively few alpine species. Significant correlations exist between type of seed dormancy in alpine plants and certain environmental factor. Soil disturbance is the most characteristic feature of the alpine environment. Seed coat inhibition appears correlated with most frequent occurrence of species exhibiting seed dormancy on sites of severe soil disturbance. As an ecologic phenomenon, seed dormancy appears to be represented in at least one species in each major alpine community type. It is proposed that seed dormancy may account for the relative abundance and successional success of the dominant species. With regard to the nature and extend of seed dormancy, intraspecific variations among ecotypes occur, and may contribute to the relative abundance and success of a species in different communities.