Snow gums are the quintessential alpine tree of the mainland, generally growing at heights between 1,300 and 1,800 metres asl. Forests and woodlands of Eucalyptus pauciflora can look quite uniform from a distance, but up close they have such character. I find them almost lyrical in how they grow, and love the gradation in form from lower to higher elevations. There are six sub-species that are known, with E. pauciflora subsp. Pauciflora being the most widespread. Unlike many Australian ecosystems, while snow gums are fire adapted (they can survive or regenerate well after fire) the open woodlands that they tend to exist in do not require burning to reach optimal ecological balance. Nor do they do not require burning to encourage the growth of new seedlings.
In the absence of fire, trees can be long lived. One tree near the summit of Mt Stirling in Victoria is estimated as being 500 years old. And with the absence of fire, the canopy will often become reasonably dense, reducing the understorey and creating a park like forest floor. Trees will seed and fill in gaps in the canopy as storm or fire creates new opportunities.
Snow gums can reproduce via seed where the conditions encourage it (eg after a fire or where natural gaps are created in the forest canopy) and via vegetative reproduction in times of environmental stress, such as prolonged drought.
But wildfire has been devastating large swathes of snow gum habitat, with significant fires in the Victorian High Country in 1998, 2002/3, 2006/7 and 2013. Much of Kosciuszko National Park was burnt in 2003. South Eastern Australia suffered from a drought that lasted more than a decade and this greatly increased the severity of the fires that have occurred since the turn of the 21st century. The result of the fires is that often the parent tree has been killed back to ground level, with subsequent re-shooting of leaves from lignotuber buds under the bark. In this way, individual trees can exist through various ‘lives’, often surviving multiple fires.
But, as anyone who has travelled through the Alps over the past decade will know, the number of dead trees keeps growing as fire follows fire. With climate science clearly telling us that we face more severe fire seasons, we can only expect this trend to continue.
There is no evidence that cattle grazing would ‘reduce blazing’ (fire risk) in the sub alpine woodlands, although the cattlemen will continue to push their line. As fire becomes even more common and our fire fighting and emergency services are ever more pushed in responding to fires, there is the possibility that eventually the decision might be taken to focus our resources on asset management – protecting human resources like buildings – rather than managing fires at the landscape level. There will be on going debate about the role of fuel reduction fires, and logging interests will continue to argue that gaining access to currently protected forests can also be a tool to reduce fire intensity.
But what about the land? How will the alpine and sub alpine areas respond to ever more frequent fires?
We currently have a state government in Victoria which is deeply ideological and anti environment. They have shown that they are quite willing to ignore science if they don’t like what science is telling them. Thankfully there is also some good research about what increased fire risk might mean for natural systems in the mountains.
When it comes to snow gums, some recent research has been carried out to look at the impacts of fires on Lake Mountain and the Buffalo Plateau. The report How snow gum forests and sub-alpine peatlands recover after fire was written by Fiona Coates, Philip Cullen, Heidi Zimmer, James Shannon. They used the long unburnt Baw Baw Plateau as an example of what these systems could be like in the absence of fire events.
The fires at Lake Mountain were especially destructive, with almost all the trees that had originated after the 1939 fires being burnt in the 2009 Black Saturday event. At Lake Mountain, tree stems which had originated after the 1939 fires were all killed in the severe fires of 2009, as were very large stems which had survived the 1939 fires. According to the report, these ‘were rarely recorded elsewhere in the study area’, illustrating the widespread loss of old growth snow gum from these mountains under high fire frequencies. Tree mortality was 15%, which may be higher than expected after fire.
The researchers note that the fires that have been occurring on a regular basis since 2003 have already ‘caused considerable changes to the structure of snow gum forests’.
Anyone with an interest in the future of our sub alpine landscapes would do well to check their research.
Some of the key messages are:
- That even areas that have been subjected to hot and very destructive wildfire, such as on the Lake Mountain plateau, can be expected to recover – provided we can keep fires out of these systems. However, this will take time. For instance they suggest it will take the forests at Lake Mountain at least 70 years to return to pre-fire structure. No specific management needs to be undertaken to aid this process beyond excluding fires
- The researchers repeatedly note that there are serious doubts about the value of fuel reduction burning in these forests. They note that low intensity fires negatively impact on tree resprouting ability
- Repeated fires change the character of snow gum forests, creating a multi stemmed forest of shorter trees. That is, forests get denser, with more of a ‘Mallee’ aspect to how the trees grow. They call this ‘potentially irreversible degradation of stand structure’, which has already happened to the extent that old growth snow gum forests are now rare. They note that the traditional open forest structure of snow gum forests will not be able to develop if there are repeated fires, as the result over time will be that forests will become dominated by lots of small stemmed trees rather than a ‘traditional’, open snow gum forest
- Repeated fires can also inhibit the ability of trees to store carbon above the ground
- They say that ‘fire exclusion is imperative to preserve landscape quality and representation of long unburnt snow gums’
- They recommend that current ‘fire and cattle exclusion policies’ at places like Mt Buffalo and Lake Mountain be continued. They note that cattle grazing can drive the creation of multi stemmed trees, in the same way that fire tends to, again driving the forest towards a multi stemmed and immature form. Exclusion of cattle is also very important for recovery of burnt areas of peat land
- Older, more open snow gum forests are better at collecting water and ensuring regular run off, retaining soil moisture and snow accumulation.
So, the take home message is that we need less fire in snow gum forests and that grazing will be a hindrance, not an asset as fire damaged forests recover.
[Note: This article was written when the Coalition were in power at the state level. Since then, the ALP has banned cattle grazing from the Victorian mountains.]