Do Australia's giant fire-dependent trees belong in the rainforest?

Oct 31, 2012

Australia's giant eucalyptus trees are the tallest flowering plants on earth, yet their unique relationship with fire makes them a huge puzzle for ecologists. Now the first global assessment of these giants, published in New Phytologist, seeks to end a century of debate over the species' classification, a debate which may determine their future.

Gigantic are as rare as they are awe inspiring. Of the 100,000 global tree species only 50, less than 0.005%, reach over 70 meters in height. While many of these giants live in Pacific North America, Borneo and similar habitats, 13 are eucalypts which live in Southern and Eastern Australia.

The tallest flowering plant to call Australia home is Eucalyptus regnans, with temperate eastern Victoria and Tasmania being home to the six tallest recorded species of the genus. One Tasmanian tree was measured at 99.6 m, while a tree in Victoria achieved the historic record of 114.3 m.

"The conifers of North America are often thought of as the largest trees on earth, yet the flowering eucalyptus trees of Australia reach comparable heights," Professor David Bowman, from the University of Tasmania's School of Plant Science. "This is surprising as Australia is the world's driest inhabited continent. Yet, this apparent paradox may explain the of in trees."

Wildfires are common in dry and arid environments such as Australia, but Eucalyptus regnans has evolved a unique dependency on fire for regeneration. While fire may kill the trees, their seeds are protected in aerial capsules, which are then released on to the scorched earth. The fire not only clears away potential seed predators and any which may block sunlight; it also releases nutrients in the soil which encourages seed growth.

"This unique relationship with fire helps us understand how these giants evolved," said Bowman. "Our research suggests gigantism in eucalypts evolved opportunistically within the last 20 million when the ideal environmental conditions for rapid tree growth were combined with the presence of wildfire."

However, fire dependency now threatens the trees' future as much as it has shaped their past. Due to this trait foresters classify the tree as unique type of Australian vegetation, rather than considering it a rainforest tree.

"This classification has serious scientific and conservation implications for the remaining forests of mature (old growth) giant eucalypts," said Bowman. "Giant trees have huge value for the timber industry, yet there are strong environmental reasons for their protection. Classification as rainforest trees would support arguments in favour of conservation."

Dr Bowman's team presents a comparative analysis which clarifies the relationship between the giant eucalypts and other rain forest species. Their findings suggest that while the species has evolutionary advantages which allow it to outcompete other species, they do coexist on the margins of rainforests and should be considered part of that ecosystem.

"Our work seeks to resolve a century old dispute about rain forest classification," concluded Professor Bowman. "Rather than seeing them in isolation we place these giants into their global context by recognizing them as of rainforest tree, albeit trees with a unique dependence on fire."

Explore further: More vets turn to prosthetics to help legless pets

More information: Y. P. D. Tng, G. J. Williamson, G. J. Jordan, D. M. J. S Bowman, "Giant eucalypts – globally unique fire-adapted rain forest trees?", New Phytologist, Wiley, DOI: 10.1111/j.1469-8137.2012.04359.x

add to favorites email to friend print save as pdf

Related Stories

Eucalyptus genetic secrets unlocked

Jul 26, 2011

The world’s most farmed tree has had its genome read, opening the way to new breeding, biofuel, and conservation opportunities.

Gum trees fire up history revision

Feb 16, 2011

(PhysOrg.com) -- Australian bushfires appeared 50 million years earlier than previously thought and probably contributed to transforming the landscape from rainforest into the country’s dry eucalypt forests ...

Trees influence epiphyte and invertebrate communities

Jan 05, 2012

Studies in temperate regions have demonstrated that genetic differences between individual trees affect the ecological communities and ecosystem processes associated with them. Now scientists at Manchester ...

Scientists to sequence Eucalyptus genome

Jul 05, 2007

An ambitious international effort has been launched today to decode the genome of Eucalyptus, one of the world’s most valuable fibre and paper-producing trees.

Can you rescue a rainforest? The answer may be yes

Mar 27, 2008

Half a century after most of Costa Rica's rainforests were cut down, researchers from the Boyce Thompson Institute took on a project that many thought was impossible - restoring a tropical rainforest ecosystem.

Recommended for you

Orchid named after UC Riverside researcher

10 hours ago

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

12 hours ago

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

12 hours ago

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...