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Abstract
Six plant communities growing on soils associated with the Dun Mountain Ophiolite Belt on the western flanks of West Dome, Southland arc described. The most widespread communities within the study area are Nothofagus solandri var. cliffortioides forest, tall Leptospermum scoparium scruland, and an open Leptospermum scoparium shrubland and an open Leptospermum scoparium shrubland variant with the rare ultramafic endemic Celmisia spedenii G. Simpson. Less extensive are mixed divaricate shrubland and Chionochloa rubra (red tussock) grassland. Soil properties for each community were compared.
Surface horizons under Nothofagus forest were the most acid and had the highest CEC and lowest base saturation of all the soils studied. In contrast surface horizon under open Leptospermum with Celmisia spedenii and divaricate shrubland had very high base saturation and were slightly acid. The former community, however, had soils formed mostly in in situ serpentinite in which the exchange complex was dominated by Mg, whereas soils in the latter community were formed in scree and had an exchange complex dominated by Ca. The tall and open Leptospermum communities (without Celmisia pedenii) had intermediate chemical properties in surface horizons, and the Chionochloa rubra soils were similar to those under Nothofaous forest.
Soil chemistry and susceptibility of soils to wind erosion appears to have determined the distribution of the open Leptospermum with Celmisia spedenii community on West Dome, and soil chemistry and physical factors probably also control the distribution of divaricate shrubland. The distribution of Nothofagus forest, Leptospermum communities without Celmisia spedenii, and Chionochloa rubra grassland are probably largely determined by past fires.