ION-RICH PRECIPITATION AND VEGETATION PATTERN ON SUB-ANTARCTIC CAMPBELL ISLAND

Campbell Island, situated in the middle of the belt of southern ocean gales, experiences a mean windspeed above that at which sea spray forms. Ionic concentration and related parameters were measured in precipitation collected throughout a year along a transect of rain gauges extending inland from the windward. westerly coast and up to the highest point on the island (558 m). Concentrations decreased logarithmically away from the coast and varied between seasons. Seasonal variation was correlated with the frequency of gales. The calculated annual input of ions ranged from 2507 kg ha-1 yr-1 Na at 50 m from the windward coast to 187 kg ha-1 yr-1 Na at 5500 m from the windward coast. The high values are related to the exposure of the collection points and to the latitude, and hence climate, of Campbell Island. Marked spatial variations in ionic input have a controlling influence on floristic structure and productivity patterns of subantarctic vegetation. This is consistent with the dominance of the maritime factor in explaining the primary axes of vegetation ordination.