The longevity of constructed log pile fauna habitats in restored bauxite mines in relation to recurrent wildfire in the jarrah forest of Western Australia



Coarse woody debris (CWD) is often returned to rehabilitated areas after mining to provide specific habitat features for fauna that might otherwise take many decades to develop naturally. The CWD, typically constructed into log piles, is assumed to persist for comparable periods of time to fulfil their role. In the fire-prone jarrah forest in Western Australia, these structures will be subject to recurrent wildfire, but there is little information on their survival. In January 2006, a wildfire burnt through 310 ha of rehabilitation at Alcoa’s Willowdale bauxite mine, 140 km south east of Perth, enabling the first estimates of the longevity of log pile fauna habitats to be made. Reductions in numbers of logs were greatest for small (<30 cm diameter) logs (48%), intermediate for large (>30 cm diameter) logs (37%) and least for stumps (17%). Assuming an exponential decay pattern, half-lives of 1.1, 1.5 and 3.7 wildfires were calculated for small logs, large logs and stumps respectively, from which we estimate a useful ‘life’ of a typical log pile fauna habitat of 57–73 years. Increasing fire intensity was associated with greater reductions in the number of large logs, significantly greater surface charring and, at the highest intensity, significantly fewer crevices compared to unburnt log piles. Implications of these findings for the management of log piles in rehabilitation and CWD in the adjacent unmined forest, and of the role of prescribed fire, are discussed.