Natural regeneration of native vegetation on abandoned agricultural land in the Fitzgerald Biosphere

Much of the natural landscape in the south-west of Western Australia has been severely modified as a result of past and current agricultural activity. One of the most conspicuous changes has been the large scale clearing of native vegetation, The evidence of the negative impacts of this vegetation removal on the natural environment is now extensive, particularly in the south-west region of the State. In order to prevent further degradation of the landscape of the south-west and subsequent loss of endemic species, strategic revegetation within the agricultural landscape is required. Native vegetation corridors can be established, linking areas of remnant vegetation and enhancing ecosystem function and habitat value. Natural regeneration of old-fields is one method that can assist in the cost-effective development of vegetated corridors. Natural regeneration of old-fields is the process by which agricultural land is abandoned and left to revegetate. It is a form of secondary succession, which involves the replacement of pre-existing vegetation following a disturbance that disrupts that vegetation. This work has illustrated the ability of native plant communities to recolonise previously disturbed or degraded areas and redevelop self-sustaining ecosystems. It has also shown that regeneration rates vary considerably as a result of different barriers to re-establishment, such as soil condition, availability of viable seed and climatic conditions. The aim of this research was to examine the progression of old-field recovery in the Fitzgerald Biosphere Region in the context of time since abandonment and to identify potential constraints. The assessment of the progression of old-field recovery involved contrasting the floristic characteristics of paddock areas with that of adjacent remnant vegetation. In addition, a profile of the soil characteristics and proximity to adjacent remnant vegetation was developed, in order to ascertain potential influences on the progression of old-field recovery. The results of this study indicated that time since abandonment was the most important constraint on old-field recovery. Proximity to remnant vegetation was also established as having some influence over diversity. Strong correlations existed between the state of a number of soil properties and vegetation composition, particularly compaction, organic matter and nutrient content, however further study is required in order to establish whether or not recovery is being influenced by them. From these results, it is recommended that old-field recovery does present a viable revegetation technique in the Fitzgerald Biosphere, however the potential constraints identified by this research have to be considered during its implementation. It is anticipated that this study will provide private landowners and landcare organisations with relevant information regarding the capacity of native vegetation to recover on old-fields and consequently, whether it will provide a viable future revegetation option. At the very least, it is anticipated that this research will facilitate more extensive future study into old-field recovery of the unique and biodiverse vegetation of the Fitzgerald Biosphere