Impact of a large wildfire

Management guidelines for many fire-prone ecosystems highlight the importance of maintaining a variable mosaic of fire histories for biodiversity conservation. Managers are encouraged to aim for fire mosaics that include all successional states of vegetation, and also include variation in the underlying ‘invisible mosaic’ of past fire frequencies, severities, and fire-return intervals. But how should a fire mosaic be managed following the occurrence of a large, unplanned wildfire? Does the previous fire history of vegetation and habitats persist after major wildfires? It’s a topic has that has rarely been investigated.

In this study, Claire Foster and colleagues at ANU tested to what extent a large wildfire interacted with previous fire history to affect the structure of forest, woodland, and heath vegetation in Booderee National Park (NSW south coast) (Foster et al, 2017). A massive unplanned wildfire burned half the park in 2003. The researchers tracked the recovery of vegetation structure for nine years after the event and found that the strength and persistence of fire effects differed substantially between vegetation types. Vegetation structure was modified in forest, woodland, and heath vegetation, but among-site variability in vegetation structure was reduced only by severe fire in woodland vegetation. There were also persistent legacy effects of the previous fire regime on some attributes of vegetation structure including forest ground and understorey cover, and woodland midstorey and overstorey cover. This suggests that even after a large, severe wildfire, underlying fire histories can contribute substantially to variation in vegetation structure.

Consequently, it’s important that efforts to reinstate variation in vegetation fire age after large wildfires do not inadvertently reduce variation in vegetation structure generated by the underlying invisible mosaic.

Reference

Foster C, P Barton, C MacGregor, N Robinson & DB Lindenmayer (2017). Effects of a large wildfire on vegetation structure in a variable fire mosaic. Ecological Applications http://onlinelibrary.wiley.com/doi/10.1002/eap.1614/full

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