Large herbivores can have a major influence on the structure and composition of vegetation communities. While some level of herbivory is required to maintain diverse vegetation communities, high levels can lead to declines in vegetation condition, and subsequent declines in faunal diversity.
With reduction in predation by dingoes and man, and increased water availability, eastern grey kangaroo (Macropus giganteus) numbers have increased in recent years, leading to changes in vegetation condition. Currently little is known about what impact these changes are having on faunal diversity, and what level of herbivory is optimal for biodiversity conservation.
An investigation into the impact of kangaroo grazing on fauna is being undertaken at 27 grassy woodlands and grasslands, spanning areas with high through to low levels of grazing. Three fauna groups, spiders, birds and reptiles, were chosen as response variables. As part of this reserach, optimal methods for accurately quantifying kangaroo grazing pressure, and the development of a native pasture growth model are also being undertaken. Inital results indicate a strong influence of kangaroo grazing on the presence of the Common Dwarf Skink (Menetia greyii), with individuals only present in sites with greater than 250kg.DM/ha. Results from this study will offer insights into optimal management of kangaroo grazing for fauna conservation within grassy woodland ecosystems.
Change in the abundance of skinks at three scales, with changes in the understorey structure in grassy woodland and grassland communities in south-eastern Australia.
The abundance of ground dwelling skinks is being investigated at 27 grassy woodland and grassland sites using concrete tiles as artificial substrates. Sites have been stratified based on three types of grass cover, with low grass (<250kg/ha), moderate (<450 kg/ha) and high grass (>450 kg/ha). Initial results show that skink abundance is higher at sites with high and moderate grass compared to those with low grass. Furthermore, the scale of resource use is important, with reptiles showing preference for tiles based on vegetation attributes immediately (within 1m) surround tiles. Tiles place in area with high bare ground and low grass (<150kg/ha) are not used by reptiles, indicating that importance of fine scale grazing management for reptile conservation.
The affect of fragmentation, urbanisation and grazing on declining woodland birds.
Bird surveys have been completed at all 120 study plots, with eight 10min point counts undertaken at each plot, with 2 in each season. Survey data is currently being entered, with analysis to be undertaken in early 2011. Bird occurrence data will be compared to a number of habitat (grass cover, tree density, etc) and landscape (fragmentation, land use) scale variables collect at plots to determine strong predictors to bird occurrence.
Grass growth model for grassy woodland environment in the Australian Capital Territory.
Currently, grass models for native pastures are undeveloped, with no growth models developed for grassy woodlands. An understanding of the grass production in these systems is critical for grazing management, if thresholds for biodiversity conservation are to be established. To provide insights into native grass productivity within grassy woodlands, grass growth is being measured using herbivore exclusion cages at three study sites. Two of these sites are located in the ACT (Mulligans Flat and Goorooyarroo Nature Reserves), the other site is in Victoria (Nardoo, a Bush Heritage property). Measurements obtained for the growth of native grass will be use to calibrate an existing grass growth model, such as GROWEST. Results from this research will also provide insights into the growth rates of different native grass species with a diverse grass composition present within study plots. This research will provide the first insight into native grass production in grassy woodland systems.
Funding and support sources:
Bush Heritage Australia http://www.bushheritage.org.au/