Forest wildfire impact is widely believed to increase with time since disturbance, presenting a dilemma for the persistence of fire‐sensitive species. However, in south‐western Australia, disturbance has been shown to increase wildfire likelihood for some decades before it again declines. It has been proposed that this trend occurs through ‘ecological controls’ on wildfire such as the self‐thinning of fire‐stimulated understorey growth. Here, we analyse six proposed ecological controls using a surveyed chronosequence of a Eucalyptus jacksonii forest community. We quantify plant growth (growth and self‐pruning) and succession (changing plant traits, self‐thinning), along with consequent changes in surface and suspended litter. We then use a biophysical, mechanistic model to predict the dynamics of flame height and canopy scorch/consumption, along with suppression difficulty during wildfire conditions. To identify the importance of each potential ecological control, we separately manipulate them to grow hypothetical forests from 1 to 100 years; each with one of the controls removed. We then model flame height in each to compare with the original forest that had all controls present. Fire initially promoted dense understorey regeneration, but ecological controls transferred this biomass from fuel (likely to ignite) to overstorey shelter (unlikely to ignite, creating a less flammable microclimate). The effect of these changes was to alter modelled fire behaviour, such that flame dimensions in mature forest were half those in regrowth, canopy damage greatly reduced, and fire suppression opportunities maximised. The primary controls were self‐thinning and self‐pruning. Forest growth and succession explains observed trends in flammability dynamics in south‐western Australian forests, and the persistence of fire‐sensitive species over time. Approaches that cooperate with, rather than disrupt, these processes therefore provide a pathway to mitigate current climatic effects on fire. Read the free Plain Language Summary for this article on the Journal blog.

Cook, C. N., G. Wardell-Johnson, R. W. Carter, and M. Hockings. 2014. How accurate is the local ecological knowledge of protected area practitioners? Ecology and Society 19(2): 32.http://dx.doi.org/10.5751/ES-06341-190232

The environment of the northern jarrah (Eucalyptus marginata) forest (NJF) of Mediterranean-climate, south-western Australia is characterised by deeply weathered soil profiles and low fertility, reflecting long geological stasis. This fire-prone environment is characterised by primary forests of low productivity but high biomass. Since European settlement (1829), the NJF has been structurally transformed by deforestation and resource extraction, including logging and mining (principally for bauxite). Rainfall has declined by 15–20% since 1970, with projections for further decline. A new hydrological regime foreshadows regolith drying, with a changed climate leading to more unplanned, intense fires. Declining productivity, coupled with rehabilitation more suited to a wetter climate, places stress on tree growth and compromises biodiversity. Thus, ecological disruption likely follows from interactions between climate change and historical exploitation. The complex challenges posed by these interactions require multifaceted and novel solutions. We argue that under drying conditions, maintenance of productivity while conserving biodiversity can best be achieved by changing the focus of rehabilitation to the understorey. This would coincide with protecting and restoring surrounding unmined forest with emphasis on the overstorey. Presently, state-of-the-science rehabilitation seeks to restore jarrah forest, following bauxite mining. This goal is unlikely to be achievable across extensive areas under climate change projections. Rather, a focus on restoring understorey following mining would provide a more positive water balance in the wider forest matrix. This approach recognises loss of forest values through mining, but anticipates conservation of biodiversity and important elements of forest structure by minimising ecologically unacceptable disturbance to surrounding forest.