Bryophyte propagule banks in a feldmark on subantarctic Macquarie Island

Subantarctic Macquarie Island has substantial areas of feldmark on its plat eau above 200 m altitude. Samples of the substrate (5.5 cm in depth) from b are areas of feldmark contained viable propagules of bryophyte species foun d at adjacent and distant sites on the island. In laboratory conditions pro pagules of 15 bryophyte taxa germinated, allowing interpretation of reasons for bare patches in feldmark: bryophytes were successful at colonizing sta ble ground but when surface movement was present, burial and/or damage of p ropagules and young plants prevented colonization. Spherical moss polsters found in cryoturbatic areas in feldmark, however, represent a growth form t hat can tolerate surface movement. A conceptual model illustrating processe s associated with colonization dynamics of bryophytes on feldmark terraces is presented. Ten of the 15 germinated taxa were nonlocal taxa which curren tly grow in plant communities at lower and hence warmer altitudes on Macqua rie Island. The presence of viable propagules of these taxa provide an imme diate and constant potential for dramatic vegetation change with climate ch ange.