Threat of frequent fire and drought for the rare wattle 'Acacia williamsiana' J. T. Hunter: an experimental burn highlights implications for fire management

Abstract

Climate change projections are predicting large increases in drought in Australia along with more frequent fires associated with the drier and warmer conditions (Cary 2002; Australian Greenhouse Office 2003, Pittock 2005). Plants in fire and drought-prone vegetation communities may respond to these disturbances by means of recovery mechanisms or survival strategies to persist in these environments after fire (Keith 1996; Bradstock & Kenny 2003) or drought (Davidson & Reid 1989; Morgan 2004). Resprouting from bud reserves under the bark, from lignotubers, basal stems or rhizomes are recovery responses of many Australian plant genera in communities subject to frequent fire (Keith 1996) and drought. However, despite an ability to recover from single fires, high-frequency fire can cause some species to decline or become locally extinct if resprouters do not have time to recover reproductive capacity. Repeated disturbances can deplete a plant's reserves and soil seed stores and the regenerative capacity of vegetation may be affected by a combination of fire and drought (Keith 1996; Lawler et al. 1998; Marod et al. 2004; van Nieuwstadt & Sheil 2005), especially if inter-fire periods are short and droughts frequent. Croft et al. (2007) proposed a model that predicts the decline of several rare and threatened plants, including the rare wattle, 'Acacia williamsiana' J. T. Hunter, subject to the combined impact of fire and drought. They concluded from observations of wattle survival after a wildfire followed by drought that fire history should be adjusted to include severe drought in formulating fire management guidelines for sclerophyll vegetation. Here we examined the survival of plants from the same population of 'A. williamsiana' subject to a second experimental fire 5 years after a wildfire and intervening drought. The results indicate that caution is required with fire management in communities with this rare plant.