Pattern of distribution of Townsville stylo, annual grasses and perennial grasses in relation to soil variation.
The patterns of variation of soil conditions and vegetation were mapped on a mosiac area (4 ha) of solodized-solonetz and solodic soils at Lansdown, Queensland. The soil variables measured included topography, available P, depth of A horizon, pH, basic exchangeable cations and the total soluble salts profile. Vegetation attributes included the total herbage yield and yield of perennial grasses, annual grasses, Townsville stylo (Stylosanthes humilis) and forbs. Only the total soluble salts profile accounted for a significant amount of the variation in vegetation attributes. Since the salt profile is known to be dependent upon the normal depth of wetting in the B horizon, it is concluded that the pattern of perennial grass distribution was determined primarily by variation in subsoil permeability, i.e. water storage capacity. The yield of other vegetation components were negatively correlated with the perennial grass component, and it is concluded that the edaphic factors influence these components mainly indirectly via competition with the taller growing perennial grasses.