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The benefits of fire. How heat and smoke can help save critically endangered ecosystems

[by Trease Clarke]

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PhD candidate from Charles Sturt University Josh Hodges, Senior Lecturer in Vegetation Ecology from Charles Sturt University Dr Jodi Price and Professor Adrienne Nicotra from the Australian National University, in the field setting up the plots where seeds were sown before burning. Image: supplied

Researchers from Charles Sturt University in conjunction with Parks Australia have found that fire, in a ‘controlled’ sense, can save a critically endangered ecosystem.

The project, ‘Post-fire seedling recruitment in grasslands and grassy woodlands of south-eastern Australia’, investigated whether fire can promote germination of many wildflowers and grasses in grasslands and grassy woodlands.

Researchers sought to determine if fire plays a role in increasing regeneration in critically endangered grasslands and grassy woodlands by promoting germination of wildflowers and grasses through fire-related germination cues such as smoke and heat.

Planned burns were conducted across four different sites in the ACT and Victoria in 2019 with collaboration from additional partners including ACT Parks, NSW Rural Fire Service, Country Fire Authority, Taungurung Land and Water Council, and Trust for Nature.

The researchers conducted laboratory experiments at the National Seed Bank investigating the effect of fire-related smoke and heat on germination. Out of the 55 plant species, 44 were found to have increased germination in response to fire.

PhD candidate in the Charles Sturt School of Agricultural, Environmental and Veterinary Sciences  Mr Joshua Hodges said fire had been used by First Nations people to maintain the diversity of food and medicine plants in grasslands and grassy woodlands for over 65,000 years. 

“Fire reduces biomass creating gaps for germination and reducing competition for resources, and it also provides smoke and heat cues essential for maximising germination,” Mr Hodges said.

“For more than 25 years, previous work in grasslands and grassy woodlands found that fire (and other disturbances) maintains the diversity of many forbs and grasses which would otherwise be lost from grasslands in the absence of disturbance.

“It has led to the conclusion that other disturbances such as mowing or cattle grazing that reduce biomass can be substituted for fire. However, our research suggests that fire is essential for promoting germination via smoke and heat cues.”

Mr Hodges said this suggests that simply removing biomass is not enough to promote regeneration of new individuals and maintain population viability in the long-term.

“It is essential that we provide the correct physiochemical conditions to ensure new individuals are regenerated to maintain these critically endangered ecosystems,” he said.

 

Senior Lecturer in Vegetation Ecology in the Charles Sturt School of Agricultural, Environmental and Veterinary Sciences, Dr Jodi Price reflected on the importance of this research as we enter planned burning season.

“Our research has highlighted the importance of smoke-promoted germination for many wildflowers including culturally important plants for Traditional Owners,” Dr Price said.

“For example, the yam daisy improved germination from 30 per cent when untreated to 93 per cent when subject to heat and smoke.”

“Smoke-cued germination is common in other fire-prone ecosystems but is reported for the first time as relatively common for grassy ecosystems. Practically, this means fire, and the re-introduction of fire in areas where traditional practices have been removed, is really important for maximising biodiversity in these grasslands.”

Mr Hodges found that fire-related germination cues increase germination of many common wildflowers and grasses. 

 

“Managers need to be conducting low intensity burns, sometimes referred to as 'cool burning', to conserve and restore critically endangered grasslands and grassy woodlands. Fire can also be used to increase the success of seed sowing in restoration.”

 

Parks Australia, through the National Seed Bank at the Australian National Botanic Gardens, collaborated closely with Charles Sturt University on this important research.

 

National Seed Bank Manager Dr Lydia Guja said the research would help increase seed germination for native species from grasslands and grassy woodlands.

“Some of the grasslands studied were in the heart of Canberra not far from the National Seed Bank. These grassy ecosystems are home to threatened plant species such as the small purple pea (Swainsona recta) and the button wrinklewort (Rutidosis leptorhynchoides) as well as many ecologically important species, and species that are popular horticulturally,” Dr Guja said.

“Species such as Kangaroo grass (Themeda triandra), native flax (Linum marginale) and yellow buttons (Chrysocephalum apiculatum), used in restoration projects and available from native plant nurseries for people to grow at home, will benefit from this research which has uncovered fire responses that increase how many seedlings can be generated from a batch of seeds.”

Coming into planned fire season, Mr Hodges noted that fire agencies have identified a high risk of grassfires resulting from a lot of grass growth due to increased rainfall.

“Some large grassfires have already occurred in Victoria and South Australia, so it is vital to reduce the risk of further grassfires,” he said.

“My research suggests there may be ecological benefits of planned burns for critically endangered native grasslands by promoting recruitment of native wildflowers and grasses.”

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