Observations on the Vegetation of Screes in Canterbury, New Zealand

Abstract

Large unstable screes in the mountains of the South Is. of N.Z. lie at approx. 32[degree] and consist of an upper layer of coarse stones which moves irregularly over a firm dry crust. This layer merges beneath into the soil proper where moisture is usually abundant. No significant chemical differences were found for the scree soils. Wind, low humidity, high temperatures, and intense radiation of light and of heat from the stones contribute to a strong evaporation potential in the air above the scree plants. In the Cass district 299 [1953] ECOLOGY 3169-3178 only 8 spp. of plants are found on the screes and 7 are confined to them. All 8 are succulent microphyllous herbs with very large root systems and well developed conducting systems. Damage by scree movements is minimized by fast regeneration of annual shoots, and by flexible branches in some spp. A biennial spp. is less common on the most unstable screes. Consolidation results in the replacement of the specialized scree plants and initiates a succession to a grassland climax.