Plant colonization of actively sorted stone stripes in the subantarctic

Three grasses (Phleum alpinum L., Deschampsia antarctica Desv., Festuca contracta T. Kirk) and one perennial herb (Acaena tenera Alboff) are the earliest important colonizers of small-scale sorted stone stripes in fellfield areas on South Georgia. Survival potential differs considerably between the grass species and appears to be related to both tiller and root morphology. The principal species, Phleum alpinum, produces stable "islands" later colonized by other species. Its growth form and life cycle appear to be especially well adapted to this habitat. The rate of downslope movement of plants on a given slope appears to be directly related to size. The age of individual Phleum plants was assessed using morphological features and a relationship derived between age and number of tillers. A model is proposed describing the development of Phleum in fellfield areas, and its relationship to stabilization of the soil.