AbstractThe potential of birds as bio-indicators of rehabilitation success in the monsoon tropics of northern Australia was investigated at Gove (Nhulunbuy) bauxite mine in north east Arnhem Land. Given the rehabilitation goal of “compatibility” with the surrounding land use, it was reasoned that rehabilitation was successful if the bird community of such areas became similar to the surrounding forest with increasing age. The bird community and avian food resources (arthropods, nectar and seeds) of rehabilitated areas representing five successional stages (2–25 years since seeding), and of the surrounding Eucalyptus tetrodonta dominated (‘control’) open forest were compared. For each of these six vegetation classes, six replicate sites were sampled every second month for two years between December 1998 and December 2000. Plant species composition and a range of vegetation attributes were also quantified at each site. The response of birds to the rehabilitation gradient was also compared with that of spiders and grasshoppers.
With increasing rehabilitation age, there was a steady and consistent increase in both bird species richness and abundance. Although species richness and abundance of the oldest rehabilitation areas were most similar to the surrounding open forest, the bird species composition of these areas differed. The response of common species to increasing rehabilitation age varied widely, some species increasing in abundance along the rehabilitation gradient, and others declining.
Although bird species composition of all vegetation classes showed slight seasonal variation, species richness and abundance was highly consistent between seasons and years. Rehabilitation areas quickly produced avian food resources in similar or larger quantities to those of the surrounding open forest. Invertebrates were available all year but were more common during the wet season, while nectar was more abundant in the dry season.
Indicator species analysis suggested that the carnivorous-insectivorous Blue-winged Kookaburra, Forest Kingfisher and Grey Butcherbird were suitable indicator species for future studies examining the rehabilitation progress. Generalised linear modeling identified canopy height and the openness of the vegetation at 2-3 m above the ground as the most important variables affecting the abundance of species associated with the ‘control’ forest Ordination based on the species composition of birds was highly correlated with vegetation structure, but weakly correlated to woody plant species composition or avian food resources. The response of birds to the rehabilitation gradient differed from that of spiders and grasshoppers, limiting the generality of conclusions that can be drawn using birds as an indicator group, and suggests the use of additional, non-avian bio-indicators in future monitoring.
Using birds as bio-indicators suggests that there has been considerable progress towards rehabilitation success at Gove mine. However, this study has not established how similar rehabilitated areas will become to the surrounding forest, or if they will be resilient in the likely event of fire. The establishment of specific objectives by all stakeholders against which rehabilitation success can be measured is required for long-term rehabilitation success at Gove mine. This thesis provides baseline information on which such objectives can be established and measured.
|Date of Award||Feb 2005|
|Supervisor||Richard Noske (Supervisor)|