PASTURE ASSOCIATIONS AND THEIR RELATION TO ENVIRONMENT AND AGRONOMY IN THE GOULBURN DISTRICT

Pasture species form a variety of associations inn the cool temperate environment of the tablelands of New South Wales. Data from a survey of 65 paddocks on 34 farms in the Goulburn district of southern New South Wales were analysed using numerical classification methods to identify species associations. Of particular interest were the agronomic and environmental factors associated with the abundance of Danthonia spp. and Microlaena stipoides, which are persistent and useful native perennial grasses. The abundance of Danthonia spp. was negatively correlated with the abundance of exotic sown grasses (many species) and annual grass species (chiefly Vulpia spp.). M. stipoides abundance was similarly correlated with sown grass species, but had no correlation with annual grasses. It had a significant negative correlation with legume species abundance (chiefly Trifolium spp.). Sites with M. stipoides associations (n = 19 sites) had particular clearing and cultivation histories and low pH. Sites (n = 12) with a Danthonia spp. association also had particular clearing and cultivation histories, and occurred predominantly on soils derived from sedimentary parent material (11/12 sites). This association also had significantly higher annual average and total superphosphate usage. Probable mechanisms by which the concurrent environmental and agronomic factors may have determined the observed associations are discussed. It is concluded that the numerical classification system employed here revealed useful species association-site grouping units and contributed significantly to the interpretation of these data.