The ongoing recovery of Acacia chapmanii subsp. australis in Drummond Nature Reserve: A case study in adaptive management
Huston, R., Duffy, P. and Ladd, P.G. (2010) The ongoing recovery of Acacia chapmanii subsp. australis in Drummond Nature Reserve: A case study in adaptive management. In: 8th National Conference of the Australasian Network for Plant Conservation, 28 September - 1 October, Perth, Western Australia.
Prior to this research, the size class structure, levels of canopy deaths and an absence of juveniles indicated all known populations of Acacia chapmanii subsp australis R.S.Cowan & Maslin, a Declared Rare Flora, were in decline. Utilising an adaptive management approach when required to make conservation decisions on rare species substantially reduces risk whilst increasing our understanding of managed ecosystems (Wilhere 2002).
A.chapmanii is killed by fire and therefore relies on seed for survival, with the hard seededness requiring fire related germination cues to break dormancy. After a 2004 experimental burn when both burnt and control plots were fenced, seedling establishment from soil seed bank and planted seed only occurred in burnt plots. Monthly monitoring over the first 12 months showed 43% of planted seed and 50% of soilbank seed that initially germinated, survived to seedling stage.
Following this success, to monitor herbivore effect a normal DEC fuel reduction burn was conducted, with seedling emergence in the same order as after the 2004 fire. Seedling survival in open burnt plots was much lower than in fenced plots with skat counts indicating kangaroos as the culprits. Only an occasional seedling in unfenced burnt plots survived into its second year. However, when these unfenced and well grazed plots were enclosed in 2007 which eliminated herbivory impacts, there was a significant increase in A. chapmanii seedlings establishing 2 and 3 years following the fire. This increase was not seen in the initial fenced plots, possibly due to the dense ground cover of a range of species that had germinated or resprouted following the fire.
A number of other species also established within the burnt area, with indications that some species may become more dominant than they were prior to the fire. Of most concern is the extensive establishment of Eucalyptus wandoo seedlings. The established populations of A. chapmanii were mostly in open kwongan or low shrubland areas. Further research needs to be undertaken to understand how A. chapmanii will cope in future years under the canopy of an over-storey of E. wandoo, particularly as the fenced plot adjacent to the canopy of established E. wandoo had significantly fewer A. chapmanii seedlings establishing than in the other fenced burnt plots.
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|Murdoch Affiliation:||School of Environmental Science|
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