COMPETITION AND RESOURCE AVAILABILITY IN HEATH AND GRASSLAND IN THE SNOWY MOUNTAINS OF AUSTRALIA

1. Competition, resource availability and biomass were studied in thre e heath plots near the tree-line and three grassland plots 200 m highe r in the Snowy Mountains of south-eastern Australia. Heath and grassla nd did not differ in root mass, but shoot mass was higher in heath. Av ailable N and soil moisture, measured five times in one year, was high er in grassland than in heath. 2. Transplants of a timberline tree, a mid-altitude grass, and a high-altitude rosette composite were grown f or two summers and the intervening winter. Transplants were grown in s ubplots either unmodified, or with all neighbours removed, or with onl y neighbour roots present and neighbour shoots tied back. 3. Neighbour s promoted survivorship in one species but suppressed growth in all sp ecies. Based on growth, below-ground competition was more intense in g rassland than in heath. Above-ground competition did not vary between vegetation types. 4. Species varied in below-ground competitive abilit y. The strongest below-ground competitors had the highest root:shoot r atios and were found at the highest altitudes. The most intense compet ition was experienced by tree seedlings transplanted into grass plots, suggesting that below-ground competition may contribute to the exclus ion of the least effective below-ground competitors from this high-alt itude grassland.