Competition and resource availability in heath and grassland in the Snowy Mountains of Australia
1993
Wilson, S.D.
Competition, resource availability and biomass were studied in three heath plots near the tree-line and three grassland plots 200 m higher in the Snowy Mountains of south-eastern Australia. Heath and grassland did not differ in root mass, but shoot mass was higher in heath. Available N and soil moisture, measured five times in one year, was higher in grassland than in heath. Transplants of a timberline tree, a mid-altitude grass, and a high-altitude rosette composite were grown for two summers and the intervening winter. Transplants were grown in subplots either unmodified, or with all neighbours removed, or with only neighbour roots present and neighbour shoots tied back. Neighbours promoted survivorship in one species but suppressed growth in all species. Based on growth, below-ground competition was more intense in grassland than in heath. Above-ground competition did not vary between vegetation types. Species varied in below-ground competitive ability. The strongest below-ground competitors had the highest root:shoot ratios and were found at the highest altitudes. The most intense competition was experienced by tree seedlings transplanted into grass plots, suggesting that below-ground competition may contribute to the exclusion of the least effective below-ground competitors from this high-altitude grassland.
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