Friday 1 September
The mystery of leaf size solved
And a feature story by lead author Ian Wright for The Conversation here.
For the first day of Spring, we’ve got a global team of researchers who have cracked the mystery of leaf size. Their research was published today as a cover story in Science.
Associate Professor Ian Wright from Macquarie University, with 16 colleagues from Australia, the UK, Canada, Argentina, the USA, Estonia, Spain, and China analysed leaves from over 7,600 species.
They teamed that data with a new theory that in much of the world the key limiting factor for leaf size is night temperature and the risk of frost damage to leaves. Until now, the textbooks said it’s a balance between water availability and overheating.
Eureka Prize winners at Macquarie University:
Caring for Country in Arnhem Land
A unique collaboration between scientists and Aboriginal people in remote south-eastern Arnhem Land is building knowledge about Country and how local people can better manage it.
Led by ecologist Dr Emilie Ens from Macquarie University and Ngandi Elder Cherry Wulumirr Daniels, they’ve discovered species new to science, found new populations of threatened species, preserved culturally-significant wetlands, and documented the community’s plants and animals in eight local languages.
The team was awarded the Department of Industry, Innovation and Science Eureka Prize for Innovation in Citizen Science on Wednesday night.
Reinventing the laser:
Rich Mildren and his team have made diamonds into a laser’s best friend.
High-power lasers have lots of potential applications, including medical imaging, manufacturing, shooting down drones or space junk, or powering deep space probes. But one of the issues in their development is that current laser technologies overheat at high power.
Rich’s team has developed a technique to make diamond lasers that, in theory, have extraordinary power range. Five years ago, their lasers were just a few watts in power. Now they’ve reached 400 watts, close to the limit for comparable conventional lasers.
Rich received the Defence Science and Technology Eureka Prize for Outstanding Science in Safeguarding Australia.
The mystery of leaf size solved
Scientist available for interview.
Release, backgrounder and high res images available at www.scienceinpublic.com.au/category/media-releases
A global team of researchers have cracked the mystery of leaf size. Their research was published today as a cover story in Science.
Why is a banana leaf a million times bigger than a common heather leaf? Why are leaves generally much larger in tropical jungles than in temperate forests and deserts? The textbooks say it’s a balance between water availability and overheating.
But it’s not that simple.
The research, led by Associate Professor Ian Wright from Macquarie University, reveals that in much of the world the key limiting factor for leaf size is night temperature and the risk of frost damage to leaves.
Ian, and 16 colleagues from Australia, the UK, Canada, Argentina, the USA, Estonia, Spain, and China analysed leaves from over 7,600 species, then teamed the data with new theory to create a series of equations that can predict the maximum viable leaf size anywhere in the world based on the risk of daytime overheating and night-time freezing.
The researchers will use these findings to create more accurate vegetation models. This will be used by governments to predict how vegetation will change locally and globally under climate change, and to plan for adaptation.
The iconic paintings of Henri Rousseau illustrate that when we think of steamy tropics we expect large leaves. But for scientists it’s been a century-old conundrum: why does leaf size vary with latitude – from very small near the poles to massive leaves in the tropics?
“The conventional explanation was that water availability and overheating were the two major limits to leaf size. But the data didn’t fit,” says Ian.
“For example the tropics are both wet and hot, and leaves in cooler parts of the world are unlikely to overheat.”
“Our team worked both ends of the problem – observation and theory,” he says.
“We used big data – measurements made on tens of thousands of leaves. By sampling across all continents, climate zones and plant types we were able to show that simple ‘rules’ seemingly operate across the world’s plant species, rules that were not apparent from previous, more limited analyses.
“Then, using our knowledge of plant function and biophysics we developed a fresh take on ‘leaf energy balance’ theory, and compared our predictions to observed leaf sizes.”
“The most surprising result was that over much of the world the maximum size of leaves is set not by the risk of overheating, but rather by the risk of damaging frost at night. Larger leaves have thicker, insulating “boundary layers” of still air that slows their ability to draw heat from their surroundings – heat that is needed to compensate for longwave energy lost to the night-time sky,” says co-author Colin Prentice from Imperial College London, who co-ordinated the mathematical modelling effort.
“International collaborations are making ecology into a predictive science at global scale,” says Emeritus Professor Mark Westoby.
“At Macquarie University we’re proud to have led this networking over the past 20 years.”
- Niall Byrne, email@example.com, +61-417-131-977
- MQ contact Emma Casey, +61-2-9850-1039, firstname.lastname@example.org
- Ian Wright, senior author, email@example.com
Big leaves, sometimes up to 1 metre2
- Musa textilis, the Phillipino banana tree
- Heliconia caribaea , found in places like Jamaica. Looks like a banana leaf.
- Magnolia macrophylla (bigleaf Magnolia) is well known from southern USA.
- Probably the biggest in Australia is candlenut, Aleurites moluccana, with leaves > 700 cm2.
Small leaves < 1 mm2
- The desert plant Eutaxia microphylla
- Common heather (Calluna vulgaris), common in Europe
- Common eutaxia (Eutaxia microphylla) – from Australia’s arid zone
- Camel thorn (Acacia erioloba) – from arid areas in southern Africa.
Leaf size varies by over a hundred thousand-fold among species worldwide. Although 19th Century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal gradient of leaf size has not been well quantified, nor the key climatic drivers convincingly identified. Here we characterize worldwide patterns in leaf size.
Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations.
By modelling the balance of leaf energy inputs and outputs we show that daytime and night-time leaf-to-air temperature differences are key to geographic gradients in leaf size.
This knowledge can enrich ‘next-generation’ vegetation models where leaf temperature and water use during photosynthesis play key roles.
Ian J. Wright1, Ning Dong1,2, Vincent Maire1,3, I. Colin Prentice1,4, Mark Westoby1, Sandra Díaz5, Rachael V. Gallagher1, Bonnie F. Jacobs6, Robert Kooyman1, Elizabeth A. Law7, Michelle R. Leishman1, Ülo Niinemets8, Peter B. Reich9,10, Lawren Sack11, Rafael Villar12, Han Wang1,13, Peter Wilf14.
1. Macquarie University. Sydney
2. University of Reading, UK.
3. Université du Québec à Trois-Rivières, Canada.
4. Imperial College London, UK.
5. Universidad Nacional de Córdoba, Argentina.
6. Southern Methodist University, Dallas, United States
7. University of Queensland, Australia
8. Estonian University of Life Sciences, Estonia.
9. University of Minnesota, United States.
10. Western Sydney University, Australia
11. University of California, Los Angeles, United States.
12. Universidad de Córdoba, Spain.
13. Northwest A & F University, Yangling, China.
14. Pennsylvania State University, United States.
Indigenous and Western science caring for Country in Arnhem Land
The the Ngukurr Wi Stadi bla Kantri (We Study the Country) Research Team awarded the Department of Industry, Innovation and Science Eureka Prize for Innovation in Citizen Science.
A unique collaboration between scientists and Aboriginal people in remote south-eastern Arnhem Land is building knowledge about country and how local people can better manage it.
In the last nine years the Ngukurr Wi Stadi bla Kantri (We Study the Country) Research Team has discovered species new to science, found new populations of threatened species, preserved culturally-significant wetlands, and documented the community’s plants and animals in eight local languages.
Led by ecologist Dr Emilie Ens from Macquarie University and Ngandi Elder Cherry Wulumirr Daniels, this citizen science research is also working with the Yugul Mangi Rangers to better manage the new threats facing their country—like feral animals, weeds, climate change and altered fire regimes.
The project is blending ecological methods with traditional knowledge and ways of seeing country. “Our ancestors were rangers. We were rangers for 40,000 years and are rangers today,” Cherry says. “It’s a responsibility for us to look after those things.”
“We are not doing it for ourselves. We are doing this for our country and for our people and for the sake of our culture, keeping our culture alive and strong.”
The project has brought people from the remote Aboriginal community of Ngukurr back to country, and through the Ngukurr School’s involvement with the research, produced the community’s first university students in over 30 years.
More than 300 community members have been directly involved in the research and the project has indirectly reached every person in the community of 1,000. It has also brought over one million dollars of scientific research funding into the community.
The research team is helping to maintain endangered traditional languages through the production of a 143-page community flora and fauna field guide with the Ngukurr Language Centre. The guide lists 275 species names in 10 languages—eight local Aboriginal languages and the species’ English common and scientific names. And this information is being added to the Atlas of Living Australia, the national public record of biodiversity.
“This project is not just about citizens collecting data, but about being integrally involved in all stages of biodiversity research to empower community decision-making about remote land management,” Emilie says.
The Ngukurr Wi Stadi bla Kantri (We Study the Country) Research Team is the 2017 winner of the Australian Museum Department of Industry, Innovation and Science Eureka Prize for Innovation in Citizen Science.
Macquarie University also received a $256,000 citizen science grant from the Australian Government in June 2017 to expand Emilie’s cross-cultural biodiversity research with the Ngukurr team. The project will further develop tools for cross-culture biodiversity assessment in collaboration with the Atlas of Living Australia and expand across 40,000 km2 of eastern Arnhem Land to work with local schools, Aboriginal communities and the neighbouring Numbirindi and Yirralka Rangers of the SE Arnhem Land and Laynhapuy Indigenous Protected Areas.
The Ngukurr Wi Stadi bla Kantri team is co-led by Emilie Ens, Macquarie University, with: Cherry Daniels, Ngandi Elder and South East Arnhem Land Indigenous Protected Area cultural advisor, Ngukurr community; and Julie Roy, Yugul Mangi Rangers coordinator, South East Arnhem Land Indigenous Protected Area.
Macquarie’s role in the project builds on the unique cross-cultural research of Dr Ens and brings in other University scientists Dr Rachael Gallagher, Dr Maina Mbui, Associate Professor Adam Stow and Dr Rachael Dudaniec who will contribute expertise on modelling species distributions, conservation planning and conservation genetics respectively.
More information and links to videos on the Macquarie University website here.
High-power diamond lasers invented at Macquarie University
High-power lasers have many potential applications: from medical imaging to manufacturing, shooting down drones or space junk, or powering deep space probes. But current laser technologies overheat at high power.
Rich Mildren and his team have developed a technique to make diamond lasers that, in theory, have extraordinary power range. Five years ago, their lasers were just a few watts in power. Now they’ve reached 400 watts, close to the limit for comparable conventional lasers.
Their calculations suggest that their diamond laser technology could handle over a thousand times the current power. They’ve also shown that they can use diamond to focus multiple laser beams into a single beam. And they can create almost any frequency of light.
Diamond is an outstanding optical material and exceptionally good at dissipating heat. But it’s not very good at generating a laser beam as its dense structure makes it difficult to introduce the impurity additives normally needed to amplify light. Until now.
Rich discovered that he could use light scattering (the Raman effect). When light shines on the diamond crystals, some of it is scattered at a single frequency. His team has developed a suite of techniques to enhance this effect in diamonds to create their high-power lasers.
The first applications of Rich’s work are on their way. UK company M Squared Lasers has licenced the technology to create lasers for quantum computing and biological imaging.
US and Australian defence researchers are major investors in the research, which has the potential to be used to tackle drones, boat swarms, and missiles.
And the sky isn’t the limit. Rich says, “diamond provides us with a new approach to making lasers that could impact many areas of science and technology – we are looking to see how diamond’s unique properties can tackle big challenges such as high-power lasers for gravitational wave sensing or for manipulating space debris and small space vehicles.
“What’s exciting about Rich and his team is that they’re doing the basic research, they’re generating patents (seven to date), and they’re working with industry,” says Barbara Messerle, the Executive Dean of Science and Engineering at Macquarie University.
“Rich builds on a forty-year history of laser research at Macquarie University, started by Jim Piper,” Barbara says.
“We are now the world leaders in the development of Raman lasers, using the scattering effects of light within crystals to transform conventional laser output—to reach new wavelengths, higher powers, or improved quality.
“We’ve developed the science over the last decade from fundamental research through to device research and commercialisation to the point that it is an attractive and versatile commercial technology.”
Rich Mildren is the winner of the 2017 Eureka Prize for the Australian Museum Defence Science and Technology Eureka Prize for Outstanding Science in Safeguarding Australia. The winner was announced on Wednesday 30 August at the Sydney Town Hall.
Rich is Associate Professor in the Department of Physics and Astronomy, a member of the Macquarie University Photonics Research Centre, and a past Australian Research Council Future Fellow.
More information and links to videos on the Macquarie University website here.