Mountain Journal has often reported on the impacts of climate change enhanced fire seasons on the mountains of Australia and, in particular, on plant species.
The iconic mountain species of the mainland, the Snow Gum (Eucalyptus pauciflora), has been hammered in recent decades by multiple fires, often with small gaps between fires.
MJ previously reported on work carried out by researchers from Melbourne University who found that ‘over 90% of the Victorian distribution of snow gums has been burned at least once since 2003. What is of greater concern though, is that each of the large fires of the last 15 years has overlapped to some extent, leaving thousands of hectares of snow gums burned by wildfire twice, and sometimes three times’.
They went on to say that higher incidences of bushfires, which are likely due to climate change, are devastating for the usually fire-tolerant snow gums of southern Australia.
Now an updated version of their work has been published in the Journal of Vegetation Science which delves into whether these more frequent and severe fires are leading to higher death rates of individual trees (individual snow gums have the ability to regrow after fire from ground level regrowth – called basal resprouts – but may also be killed). This work was carried out by Tom Fairman, Lauren Bennett, Craig Nitschke, and Shauna Tupper.
It confirms what had previously been expected: that in areas of snow gum woodland that had experienced high-severity wildfires between 2003 and 2013:
‘proportions of top-killed E. pauciflora stems were significantly higher, and densities of live basal resprouts significantly lower, at sites burned two or three times compared to once burned or unburned sites. Clump death increased to 50% of individuals at sites burned by three short-interval wildfires, which led to changes in live tree patchiness, as indicated by nearest-neighbour indices. Increased tree mortality was not offset by seedling recruitment, which was significantly lower at the twice- and thrice-burned sites relative to single-burn sites’.
That is, the more frequent and intense the fire, the greater the death rate of trees, lower numbers of new trees growing from seed (although they note that this varies from site to site) and a shift in the understorey from shrubs to grasses.
The article is called ‘Frequent wildfires erode tree persistence and alter stand structure and initial composition of a fire-tolerant sub-alpine forest’.
A summary of the research can be found here.
For all the MJ stories on fire and mountain environments, please check here.