Towards an Understanding of Factors Controlling Seed Bank Composition and Longevity in the Alpine Environment

The ability of seeds to regenerate from soil seed banks has long been recognized as a key survival strategy for plants establishing new niches in highly variable climates of alpine environments. However, the fundamental aspects of evolutionary/selective forces for seed bank development in alpine ecosystems are largely unknown. Here, we developed a model that describes dormancy, a high temperature requirement and a specific light/darkness regime at the time of seed shedding can preclude autumn germination, thus contributing to seed persistence until the next growing season. The benefits of these factors synchronising germination with the growing season are reviewed. Additionally, the importance of climatic variations of maternal environment affecting some of these factors is also discussed. It is suggested that the environmental conditions during the growing season partly control the seed persistence and seeds that fail to germinate are carried over to the next season. Species that have small (< 3 mg) and round-shaped seeds tend to persist more easily in soil for over 5 years, than do the large or flat seeds. However, some large-seeded species also have the potential to establish short-term persistence bank. A literature survey reveals 88 % of the alpine seeds have a mass < 3 mg. Seed size has only a weak relationship with mean germination timing (MGT) indicating that reduced persistence in large-seeded species cannot be counteracted by quicker germination, but combined effects of other factors stimulating germination remain an open area to be studied. It is proposed that long distance dispersal (LDD) is limited in most-but not all-species, primarily due to the absence of specialized dispersal structures. However, among numerous dispersal modes, most species tend to be dispersed by wind. Thus, spermatophytes of alpine environments have a greater tendency to establish seed banks and spread the risk of germination to many years, rather than being dispersed to other micro-climates.