Eleven years on from the 2009 Black Saturday fires, many landscapes are still recovering. The Central Highlands were an epicentre of old mountain ash and rainforest, but this has been steadily destroyed by decades of logging and the wild fire of 2009 burnt large sections of remaining old growth.

Prior to the 2009 fires, the O’Shannassy Catchment was a standout example of the remaining old growth of the Central Highlands. As a Designated Water Supply Catchment Area, legislated under the National Parks Act to protect water catchment and resource values, much of it is closed to the general public. Yet you could see the upper catchment from a number of vantage points, such as the road between the Lake Mountain turnoff and Camberville.

Much of it was burnt in 2009. A decade and a bit on, how is it faring?

The short answer is that while the forest is recovering, in the severely burnt portion of the catchment, 96% of the original rainforest ‘could no longer be classified as such’. And, overall, the severe fire in 2009 has led to the loss of around two thirds of the Cool Temperate Rainforest previously mapped in the O’Shannassy Catchment.

The following text comes from the research report Post-fire dynamics of Cool Temperate Rainforest in the O’Shannassy Catchment, which was produced by A Tolsma, R Hale, G Sutter and M Kohout.

The catchment contains a range of ‘botanically significant ‘representations of Wet Forest, Montane Wet Forest and, prior to the fire, around 1,500 ha of the Flora and Fauna Guarantee (FFG)-listed Cool Temperate Rainforest. The ecological value of these forests had led to them being protected as National Park.

Cool Temperate Rainforest is an Ecological Vegetation Class (EVC) listed under Victoria’s Flora and Fauna Guarantee Act 1988. In its most mature state (without emergent eucalypts) it is characterised by a more-or-less continuous rainforest tree canopy of variable height, mostly forming narrow linear strips along the margins of streams. In the Central Highlands, the overstorey is dominated by Myrtle Beech (Nothofagus cunninghamii), the mid-storey includes Southern Sassafras (Atherosperma moschatum) and Blackwood (Acacia melanoxylon), and the understorey is dominated by tree ferns and ground ferns. The understorey tends to become sparse as the rainforest ages and the canopy closes.

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Ten years post-fire, burnt plots remained compositionally different to unburnt plots, with burnt plots having higher cover of forbs, grasses and shrubs, but substantially lower tree cover. Only ferns appear to have recovered to the unburnt state. The primary rainforest species Myrtle Beech and Southern Sassafras were resprouting from the bases of top-killed parent trees, and eucalypt and wattle species were regenerating strongly from seed.

Encroachment of non-rainforest canopy species into rainforest was related to fire severity. Spatial analysis indicated that non-rainforest tree recruitment in the most severely burnt area of the catchment had been sufficiently high that 96% of primary rainforest mapped pre-fire could no longer be classified as such. Encroachment of eucalypts into plots burnt at moderate severity was more limited, and no recruits were noted in plots burnt at low severity or unburnt. This study suggests that some rainforest stands should persist in the O’Shannassy Catchment, but they will mostly be restricted to the most fire-protected parts of the landscape. Despite some documented resistance to fire, rainforest in the O’Shannassy Catchment could not cope with the highest severity fire. Conclusions and implications: Severe fire in 2009 has led to the loss of around two thirds of the Cool Temperate Rainforest previously mapped in the O’Shannassy Catchment.

Remaining rainforest stands here and elsewhere in Victoria are further threatened by predicted increases in the frequency and intensity of fire due to climate change, and the long-term future of this important vegetation type appears bleak.

While little can be done at a local scale to combat direct impacts of climate change, management should aim to protect or buffer remaining rainforest from indirect impacts and other threats.

1.Remaining rainforest needs to be protected as much as possible from fire. Management options are limited within the catchment itself, hence actions need to be undertaken at a much broader landscape scale, preferably using a cross-tenure approach.

2.Infrastructure activity, especially roadworks, near stands of rainforest should be undertaken in a manner that minimises spread of pathogens such as Myrtle Wilt.

3.Deer monitoring and control should continue in the catchment, as population numbers are expected to increase with time-since-fire.

In spite of this devastation, these fires do highlight the importance of old forests when fires do burn through them. Forest researcher David Lindenmayer says that while the catchment burnt at high severity in 2009, it was less intense than the rest of the landscape, where younger forest dominated. He also says that the rate of recovery is much faster than younger forest, more animals survive the initial fire front, more seeds will germinate and recolonisation is faster than in young/ regrowth forests.

Feature image: Bellel Creek, in the headwaters of the O’Shannassy catchment.

Source

Tolsma, A., Hale, R., Sutter, G. and Kohout, M. (2019). Post-fire dynamics of Cool Temperate Rainforest in the O’Shannassy Catchment. Arthur Rylah Institute for Environmental Research Technical Report Series No. 298. Department of Environment, Land, Water and Planning, Heidelberg, Victoria.

 

Click to access ARI-Technical-Report-298-Post-fire-dynamics-of-Cool-Temperate-Rainforest.pdf