Superstars of STEM: The researcher who asks the burning questions

Tien Huynh’s work challenges the orthodoxy of fuel-reduction native bush burning. Dion Pretorius reports.

Tien Huynh in her lab, surrounded by orchid seedlings.
Tien Huynh in her lab, surrounded by orchid seedlings.

Hazard reduction burning is an important pre-emptive defence against disastrous and deadly bushfires. Reduction burns reduce fuel loads and the risk of ignition in hot, dry climates.

However, Australian research is shedding light on the hidden cost to endemic plants when controlled burning is done without first determining the best season in which to do it.

A badly timed burn can mean the obliteration of ground-level vegetation, such as ferns, shrubs and flowering plants. Autumn is often favoured for prescribed burns because ignition is easy, and there are relatively still conditions, but little research has gone into determining whether this is best for Australia’s native flora.

Tien Huynh from the Royal Melbourne Institute of Technology (RMIT) in Victoria has been studying the effect of hazard reduction burns on three Australian flowering orchids: Pterostylis revoluta, Glossodia major and Thelymitra pauciflora.

The state of Victoria contains 28% of Australia’s terrestrial orchid species, 13% of which are nationally threatened.

“Most threatened orchids have populations of less than 100 plants, and their conservation is one of main challenges faced by managers of public lands,” Huynh says.

Broken into two studies, her research aims to identify the changes in the growth, flowering and germination of the plants in response to controlled burning.

In the first, her team conducted surveys of an autumn flowering orchid (Pterostylis revoluta) periodically before and after burning.

The researchers worked to determine the effect of the burn itself, and the impact of smoke and reduced water quality. They also sampled the health of the related orchid mycorrhizal fungi, a crucial component in the plant’s germination.

Burns were conducted mid-season in spring and summer 2011, and autumn and winter 2012, and the orchids in each test area were examined periodically up until 2014.

It was found that burning in spring-to-summer was less damaging to the orchid, which contrasts to the current preferred burning season of autumn-to-winter.

In the second study, these results were confirmed with the spring flowering orchids, Glossodia major and Thelymitra pauciflora). This produced data suggesting that the least damaging season for a prescribed burn was late spring, soon after seed dispersal, when the orchids are dormant underground.

Burning during autumn and winter drastically reduced the number and sizes of the two flowering orchids and the fungi on which they depend, thus threatening their survival. In some cases orchid numbers decreased by 100% in the following year.

Both of Huynh’s experiments also showed that fire and smoke water were not beneficial to the plant populations.

As a result of this study, land management authority Parks Victoria now conducts burns at the site in late spring whenever possible. This active conservation effort will be an important step to ensure that endemic orchid species have the best chance to survive in their environment.

Dr Tien Huynh is among 30 Superstars of STEM featured in this weekly series prepared by Science & Technology Australia (STA). To learn more about the program, visit the STA website.

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