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Introduced perennial grasses are capable of altering the habitat of native species, causing reductions in population size and vigour, and potentially affecting life-history processes such as survival, pollination and seedling recruitment. We examined the utility of herbicide treatment on two exotic grasses, Pennisetum clandestinum (Kikuyu) and Stenotaphrum secundatum (Buffalo grass) to restore the habitat of Calystegia affinis, a critically endangered species endemic to Lord Howe and Norfolk Islands. Using two herbicides, Asset (designed to affect only grasses) and Glyphosate (a general herbicide), we compared effectiveness in reducing grass cover on a population of Calystegia affinis. We protected Calystegia plants from the herbicides by ensuring their leaves were covered by plastic bags during herbicide application. Both herbicides were similarly effective in reducing grass cover after four weeks and had no noticeable adverse affect on Calystegia (suggesting the plastic bag protection was effective). After 26 weeks, Glyphosate was more effective in maintaining a reduced grass cover. Plots treated with either herbicide had a greater relative increase in abundance of Calystegia stems compared to untreated controls. The Glyphosate treatment resulted in the greatest relative increase in stem abundance, but this was not significantly greater than in the Asset treatment. We consider that spraying with Glyphosate treatment, with follow-up monitoring and spot-spraying, will assist the recovery of the Calystegia affinis population. Ultimately, the maintenance of a weed-free zone at the forest edge will provide suitable habitat for additional recruitment of this and other native species.
Kinchega National Park reserves significant stands of Eucalyptus largiflorens open woodland on the Darling River floodplain, low open Maireana pyramidata shrubland and Casuarina pauper/Alectryon oleifolius open woodland on dune systems. We identify four key issues for the conservation of flora in Kinchega National Park, western NSW. These are:
1) There is an urgent need to initiate regeneration in a number of long-lived perennial trees and shrubs. Failure to do so will lead to local population declines and extinction in a number of species. Reduction in grazing impacts of rabbits and goats is needed. Some degree of rabbit control has been achieved over the last few years through a combination of the effects of the rabbit calicivirus disease (RCD) and an extensive rabbit control program for the reserve.
2) The need to initiate a water plan of management for the reserve to overcome the problem of changes in water flows, flood periodicity and flood magnitude that have occurred in response to water regulation activities on the Darling River.
3) Management of several threatened species and ecological communities on the reserve, in particular the nationally vulnerable species Acacia carneorum and Solanum karsense. Kinchega NP is the only conservation reserve containing populations of these species and these populations are significant for both species.
4) Management of weeds, in particular those with bird-dispersed fruits as these species have the potential to become severe problems on the park.
Other issues that are likely to be significant in the future are salinity impacts and the interaction between grazing pressure, regeneration and climate change.