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Description

Eucalyptus saligna plantations with the understorey largely invaded by the introduced pasture Paspalum wettsteinii were included in the expansion of Bongil Bongil National Park (BBNP), NSW. In the 1950s, most of this area was cleared for cattle or dairy pasture, and in 1971 the remainder was cleared for eucalypt plantations. Until its dedication in 1999, this area was used for dairy farming and forestry. The eucalypts were planted for pulpwood and so were never thinned, meaning that the extant plantations are tall and densely stocked. Natural regeneration of native pioneer, secondary or mature forest species is scarce in most of the plantations which appear to be in an arrested state of plant succession. The Park’s Plan of Management states that these plantations will be restored using managed disturbance and that experiments will be implemented to determine appropriate techniques for initiating succession towards endemic communities. Plantation trees suggested intense competition for light and nutrients, providing a significant competitive barrier to the natural regeneration of understorey and alternate canopy species. The experiment consisted of 12 relatively uniform plantation blocks of 80 x 50 m of E. saligna. Three canopy reduction and two burning treatments were carried out (canopy: 0, 50 and 75 % and burning: burnt after logging and not burnt after logging). Based on the vital ecosystem attributes suggested by Aronson et al. (1993), the following variables were measured before (2003) and after treatments (2004): canopy density, understorey light, and tree and shrub composition and spatial structure. Logging and burning had a marked effect on the composition and structure of trees and shrubs in both experimental plantations. Changes were detected in eight of nine response variables (plantation tree and other woody species density, canopy density, photosynthetically active radiation, and structural indices of distance, mingling, diameter, height and uniform angle).