Eucalyptus populnea shrub woodlands. Control of regenerating trees and shrubs

Abstract

In a Eucalyptus populnae shrub woodland, trees and shrubs more than 60 cm tall were killed by stem injections or basal stem applications of chemicals. Moody plants regenerated from seed following treatment of the original stand but numbers were fewer on plots sown to introduced grasses than on those sown to annual medics or left unsown. Intermittent heavy grazing with sheep controlled seedling regeneration of all woody species except the dominant tree, Eucalyptus populnae, and an unpalatable shrub, Pimelea pauciflora. After two years only 5 per cent (50 ha-1) of the trees and shrubs present at the commencement of grazing survived on plots sown to grasses and grazed intermittently by sheep. Burning two years after the application of the initial treatments reduced the number per hectare of the three most abundant shrubs, Eremophila mitchellii, Cassia nemophila, and Dodonaea viscosa, on ungrazed plots from 3665 to 90 ; the total number of trees was reduced from 4017 to 119 per hectare. Grazing after burning reduced shrub density to 55 per hectare. The results indicate the significance of heavy intermittent grazing by sheep for controlling shrubs that regenerate following thinning of Eucalyptus populnae shrub woodlands.