BIOMASS ALLOCATION IN A SUB-ANTARCTIC CLONAL PLANT (ACAENA-MAGELLANICA) UNDER GRAZING BY INTRODUCED REINDEER

Biomass allocation and growth by the clonal plant Acaena magellanica w ere characterized for three populations grazed by introduced reindeer on the subantarctic island of South Georgia. Annual growth markers (in ternode lengths) were used to divide each rhizome into current year's shoots, one-year-old and two-year-old rhizome segments. Total dry weig hts were significantly smaller in grazed than in ungrazed populations. Leaf biomass of current year's shoots was very much lower in grazed s hoots. Rhizome length and number of leaves were less affected than dry weight by grazing, and the reindeer grazing thus seems to mainly infl uence biomass accumulation rather than morphology in Acaena. Interacti ons with Festuca contracta in both grazed and ungrazed areas were also studied in a two-year competition experiment. No apparent release of soil resources (as measured by an increase in plant growth) was appare nt in plots where Festuca was removed, but the current year's shoots o f Acaena were smaller and more numerous in these plots than in control s, especially in the ungrazed area.