Clearing and grazing impacts on vegetation patch structures and fauna counts in eucalypt woodland, Central Queensland

Abstract

There is national and international concern that tree clearing and cattle grazing reduce habitat for native fauna. In this paper we quantify how the degree of clearing and the level of grazing change the patch structure and composition of vegetation in eucalypt woodlands, and how these habitat changes affect counts for 10 species including birds, reptiles and small mammals. These species were selected because they were abundant, hence providing the data needed for ordinations and regressions. We studied 37 sites occurring in two regions of central Queensland: Blackwater/Emerald and Alpha/Jericho. On each site, indices for the degree of tree clearing and the level of livestock grazing were assessed, the cover and size of tree groves, shrub thickets, log hummocks, termite mounds and perennial grass clumps were measured, and abundances of 10 common vertebrate species were estimated. As expected, the cover and size of tree groves declined and the cover of grass clumps increased as the degree of clearing increased. Native grass composition changed to introduced Buffel Grass as the level of grazing increased. Clearing affected fauna counts more than grazing did. The Grey Butcherbird Cracticus torquatus, Yellow-throated Miner Manorina flavigula, Striated Pardalote Pardalotus striatus and Pale-headed Rosella Platycercus eximius had significantly lower counts on cleared sites, but the Red-backed Fairy-wren Malurus melanocephalus had higher counts. The introduced House Mouse Mus musculus also had higher counts on cleared sites, but Carnaby's Skink Cryptoblephrus carnabyi had lower counts. Counts of the Weebill Smicrornis brevirostris, Bynoe's Gecko Heteronotia binoei and the Delicate Mouse Pseudomys delicatulus did not significantly change with clearing. Counts for the Pale-headed Rosella increased as the level of grazing increased, but counts for the other fauna species did not significantly change with our grazing index. Except for Bynoe's Gecko, fauna counts significantly changed with various vegetation patch attributes, particularly those strongly affected by clearing. From these results, we know which of the 10 fauna species are likely to decline or increase with clearing and grazing, and this knowledge can be used by land managers.