Effects of Disturbance and Grazing by Cattle on the Dynamics of Heathland and Grassland Communities on the Bogong High Plains, Victoria

Abstract

Within the high subalpine tract of the Bogong High Plains there has been a gradual increase in the cover of shrubs over the past 40 years, especially within open heathland and grassland communities. A field trial, using permanent 1 m² plots, has confirmed that the establishment of shrub seedlings such as Asterolasia trymalioides, Grevillea australis, Phebalium squamulosum and Prostanthera cuneata occurs primarily upon bare ground, and is absent where the cover of vegetation or fixed Poa hiemata litter remains intact. The survival of Poa hiemata seedlings on bare ground is low, except where local shelter is afforded. Disturbances which cause bare ground, including domestic cattle activity, can create microsites suitable for the establishment of shrub seedlings. Shrub establishment and development may be inhibited by cattle trampling, and some palatable shrubs, e.g. Asterolasia and Grevillea, are especially affected. If cattle are removed from previously grazed grassland and heathland sites where shrubs such as Asterolasia and Grevillea have established, the encroachment of such shrubs will be more rapid than on similar sites subject to continued grazing. However, continued cattle activity is unlikely to inhibit the development of non-palatable, vegetatively reproducing shrubs such as Prostanthera cuneata and Phebalium squamulosum within closed heath communities.