Otway rainforest's tall astelias have power to thrive if given a little light, scientists show

By Emma Nobel (ABC)

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Key points:

  • Researchers are helping a rare lily called the tall astelia to reach its full potential

  • A small number of plants have managed to dodge bushfire and survive in Victoria's Otway Ranges

  • With just a little bit of extra light, the lily can thrive under the rainforest canopy

In a rainforest of lush ferns and towering eucalypts, the tall astelia stands out.

Its large, almost yukka-like appearance would not look out of place at your nearest home hardware store.

But this rare lily is something few people know about, let alone see.

Just 10,000 of the plants are thought to still exist in isolated parts of Victorian forests, and deep in the Otway rainforest, one tiny population is clinging on.

When Linda Parker first started her PhD in ecology at the University of Melbourne, she knew next to nothing about the tall astelia.

"I didn't know much about the species. I'd seen it once and just thought it's a nice understorey herb but it doesn't do much," Ms Parker said.

How do you get people to care about a plant?

So little was known about the tall astelia before Ms Parker began her PhD that all the research about the plant could fit neatly into a cardboard box.

What little information was available suggested it was an unremarkable plant that rarely flowered, took years to grow, and was in decline in terms of population.

The tall astelia lacks the star power of an ancient tree and is not cute like a furry animal.

Jack Pascoe from the Conservation Ecology Centre in Cape Otway said it was a challenge saving a plant few people had heard of.

"It's very different getting people to care about plants compared to animals. We do a lot of work with koalas that people really are invested in quite emotionally," said Dr Pascoe, the centre's conservation and research manager.

"I think for places like the Otways and the Central Highlands where it occurs, this plant is quite representative — along with some of our ferns and Nothofagus [southern beeches] — of rainforest habitat.

"If you start to associate it with the landscapes people care about, that's probably the way in."

Black Saturday fires

In 2009, the Black Saturday fires ripped through the largest site of tall astelia in the Central Highlands, decimating the population of 4,000 plants until just 1,000 remained.

But out of the ashes, Ms Parker and her colleagues noticed something remarkable.

The remaining plants began to grow and flower with a ferocity they had never seen before.

"Where the canopy had been removed, so the fire had gone straight over the top and not really burned the understorey, we had mass flowering of the astelia because they've suddenly got a whole lot of light," Ms Parker said.

The rainforest had grown so well that the scientists thought the tall astelia was not getting enough light to flower and reproduce, which made it more susceptible to disease and decline.

"That's where we came up with the hypothesis that, hey, maybe there's something with light, maybe light is a really important mechanism in this species' reproductive ecology," said Associate Professor Craig Nitschke, from the University of Melbourne.

When the scientists tested the light theory, they found the tall astelia began to thrive with just a little help.

"We don't have to do much, remove one tree, maybe remove a tree fern," he said.

"That's all we need to do, it's a very limited amount going from 1 per cent light to 4 per cent light availability, that seems to be the magic number with this species, what our analysis suggests — 4 per cent light."

Plant gives back

The extra light made all the difference to the tall astelia, which began to give back to the rainforest in ways that had never been seen before.

"Previously, we thought the astelia was just like a large lily. It rarely flowered or reproduced — we just didn't know much about its ecology," Ms Parker said.

"But now we know that it does reproduce, it can reproduce every four years and we know that the edible berries are taken by a whole suite of birds and mammals."

The researchers observed eastern spinebills and pygmy possums eating the plant's berries, while swamp wallabies feasted on its nectar.

With a little help, this seemingly unremarkable plant was able to reach its potential.

In the past, the Otway Ranges site has dodged two fires: the Ash Wednesday bushfires of 1983 and the Black Friday bushfires of 1938–1939.

Armed with knowledge of the plant's light requirements, researchers have begun relocating some tall astelia across the rainforest to help mitigate the risk of another wildfire wiping out the Otways' single population of just over 100 plants.

"It's probably been luck in terms of being able to miss some of those major landscape-scale bushfires," Dr Pascoe said.

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