Relationship Between Diaspore Characteristics and Distribution of Grasses Around Sheep Camps on the Northern Tablelands of New-South-Wales

Abstract

Twenty-seven common grasses on the Northern Tablelands of New South Wales were classified according to their occurrence on or off sheep camps in unfertilised natural pastures. A number of seed and seed germination attributes were examined in relation to the distribution of the individual species. Camps had a greater proportion of introduced grasses, and of annual or short-lived perennials, than off-camp zones. The sheep camp grasses in general had heavier seeds, more rapid germination, and their seeds in general did not have a sharp callus, antrorse hairs on the callus, or awns. If awns were present on sheep camp species a lower proportion were hygroscopically active than for off-camp species. There were no differences in the presence or absence of accessory floral structures in the dispersal unit, hairs on the coleorrhiza or in the shapes of seeds between sheep camp and off-camp grasses. The differences in seed and seed germination characteristics found between sheep camp and off-camp species are explained in terms of the differences in environment (water stress and damage by sheep) encountered by grasses germinating and establishing on and off the sheep camps.