Old-fields forever young

A study focused on understanding the barriers to the return of native species to abandoned farmland in the central wheatbelt is of interest to farmers and environmentalists alike. Funded by a three-year Australian Research Council Discovery grant, Dr Rachel Standish, Dr Viki Cramer and Prof Richard Hobbs from Murdoch University's School of Environmental Science, are researching vegetation succession on wheatbelt oldfi elds, and specifi cally what prevents the return of native plants.

In the face of rural adjustment and land degradation, land abandonment may increasingly occur in Australia, as it has in other parts of the world, particularly Europe. The question of what happens to that abandoned land is important when considering the long-term future of agricultural areas.

'In the northern hemisphere, native species return to old-fi elds unassisted but this does not occur on most wheatbelt oldfi elds,' Dr Standish said. The team compared three wheatbelt old-fi elds with their adjacent native woodland remnants and have discovered several potential barriers.

'If we understand the barriers to succession on wheatbelt old-fi elds, then we can apply the appropriate restoration treatment. For example, if seed dispersal to old-fi elds is limited, then direct seeding should promote restoration. The solution is unlikely to be that simple however. A major barrier to native plant establishment appears to be competition against introduced species. We predict that fertilizer residues promote these introduced species to the exclusion of the native species - it may seem counter-intuitive but the native species are highly adapted to nutrient-poor soils', Dr Standish said.

Dr Standish is currently looking more closely at the effect of phosphate on the competitive effect of an introduced species against native species in a glasshouse at Murdoch University.

'The wheatbelt is predominantly a production landscape with remnants of species-rich native vegetation scattered throughout. Ultimately, old-fi elds offer the potential to buffer or link up these remnants, and generally increase the representation of native species in the landscape.'