Our Valuable Native Grasslands, Better Pastures Naturally   Proceedings of the Second National Conference of the Native Grasses Association

Grass-tree/shrub interactions in a semi-arid wooded grassland after burning or grazing

Ken C. Hodgkinson and Rod A. Edmundson

CSIRO Sustainable Ecosystems, GPO Box 284, Canberra, ACT 2601.
Email: ken.hodgkinson@cse.csiro.au or rod.edmundson@cse.csiro.au

A woodland area near Coolabah, New South Wales has been studied since 1982. The paddock has been lightly grazed in an irregular manner since the 1880's. Trees were ringbarked in 1890's, early 1900's and in 1945 and shrubs have episodically increased since the last wildfire in the summer of 1920/21.

Four treatments are applied to plots in the paddock: no grazing & no fire (control), no grazing & spring fires, no grazing & autumn fires and paddock grazing & no fire. Trees and shrubs have increased in all treatments. The build-up of woody biomass has been slight in the burn and grazed treatments but large in the no grazing & no fire control treatment. However, the steady and large build-up of woody biomass did not suppress grass and forb production until recently.

Grazing shifted the botanical composition of the grassland by decreasing the proportion of palatable grass species. The data indicate that competition between woody vegetation and grasses for scarce water and nutrient resources may occur less frequently than generally thought. Furthermore, tactical grazing to avoid "death-traps" for perennial grasses should be an important component of vegetation management in addition to prescribed burning.