Impacts of mammalian herbivores on the Callitris glaucophylla - Eucalyptus albens woodland of Kosciuszko National Park
Abstract
Box Gum Grassy woodlands are classified as a threatened ecological community under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Decline in original extent of Box Gum Grassy woodlands is mostly due to fragmentation and modification for cropping and livestock grazing. The extensive disturbance, erosion, and degradation of the Callitris glaucophylla – Eucalyptus albens woodland of Kosciuszko National Park has been well documented up until 1991. Ian Pulsford and The New South Wales National Parks and Wildlife Service assembled a detailed history of the area, describing several waves of environmental disturbance over a period of around 150 years. After the arrival of white settlers in 1834, changes in fire regime, rabbit plagues, and ongoing sheep and cattle grazing resulted in intense degradation of the landscape. Unfortunately the woodland has not had an opportunity to recover, as a new wave of disturbance currently appears to be supressing the ecosystem; horses and deer. Using 33 year old exclosures and paired control plots, soil functionality, and vegetation structure and composition was examined. Soil functionality, understorey and midstorey vegetation were found to be significantly improved in the exclosures. The overstorey did not exhibit any significant improvement by exclusion of mammalian herbivores. However, Callitris glaucophylla are slow growing and likely need hundreds of years to change in structure. The native vegetation struggles to cope with the hard hooves and grazing behaviour of pest herbivores in such high population densities. Consequentially, the C. glaucophylla – E. albens woodland of Kosciuszko National Park currently appears to be in a stable degraded state.