Welcome Yuki, Xin’e Li, and Raquel

We offer a warm welcome to Yuki Tsujii, Xin’e Li, and Raquel Miatto!

Dr Yuki Tsujii has just started a two-year postdoc position in our lab, funded by the Japan Society for Promotion of Science. He will investigate the phosphorus-strategies of Australian plants by focusing on leaf P fractions.

Assoc. Prof Xin’e Li is a Visiting Scholar from Yangzhou University in China. She is a specialist on Tibetan and Mongolian grasslands and hopes to learn more about Australian ecosystems.

Dr Raquel Miatto is a postdoctoral researcher from University of São Paulo, Brazil, who is visiting the lab during April, while working with her data on primary productivity and functional diversity of the Brazilian Caatinga vegetation. Her research is funded by São Paulo Research Foundation.

 

Welcome to Fabio Berzaghi !

Welcome to Fabio Berzaghi visiting from the Laboratoire des Science du Climat et de l’Environment in France. He will be with us for the next several months. We plan to learn more about plant-animal interactions and how to model these processes. For more information, you can visit his website here: http://www.berzaghi.com/?i=1

Congratulations Rene!

Congratulations to Rene Heim, Joint-PhD student with Macquarie University and University of Hamburg, whose PhD thesis has passed with flying colours! (earning the top possible grade). Rene’s supervisors were Drs Ian Wright, Jens Oldeland (Hamburg), and Angus Carnegie (NSW Department of Primary Industries).

Rene has also been very swift and effective in converting his PhD work into publications at well-regarded journals. Double congratulations, Rene!

• Heim RH-J, Wright IJ, Allen AP, Geedicke I, Oldeland J (in press). Developing a spectral disease index for myrtle rust (Austropuccinia psidii). Plant Pathology, doi: 10.1111/ppa.12996.
• Heim RH-J, Wright IJ, Scarth P, Carnegie AJ, Taylor D, Oldeland J (2019). Multispectral, aerial disease detection for myrtle rust (Austropuccinia psidii) on a lemon myrtle plantation. Drones 3:25. doi:10.3390/drones3010025.
• Heim RH-J, Wright IJ, Chang HC, Carnegie AJ, Pegg GS, Lancaster EK, Falster DS, Oldeland J (2018). Detecting myrtle rust (Austropuccinia psidii) on lemon myrtle trees using spectral signatures and machine learning. Plant Pathology 67:1114-1121.

Field Project Underway!

Our field-based study of ecophysiological traits has officially begun! Andrea Westerband has been leading a crew of research assistants (Claire Laws and Matthew Alfonzetti) and undergraduate student volunteers (Tara Boreham, Emily Zahra, Loren Pollitt, and others) across various sites in New South Wales, Australia.

The objectives are to determine whether and how soil properties, such as nutrient availability, explain variation in leaf photosynthetic traits. This work is an extension of “least cost theory” (Wright et al 2003 Am Nat; Prentice et al 2014 Ecol Lett).

In addition to estimating leaf traits such as mass per area and nutrient availability, we are using the LICOR6800 to measure photosynthetic gas exchange! It’s an exciting time for us, as we plan to expand our study sites to other states across the country. More soon!

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Visit from Prof Hendrik Poorter

We recently welcomed Professor Hendrik Poorter, from the Research Centre Jülich in Germany, who visited Macquarie University for nearly four weeks. While here, we had the opportunity to discuss current and potential research projects relating to plant functional traits and trait plasticity. We look forward to future discussions!

Left to Right: Irene, Andrea, Hendrik; Irene, Hendrik, Dong Ning

 

Two PhD positions advertised

Two 3-year PhD scholarships are available for bright and energetic candidates to join our group. These scholarship are open to Australian or international applicants.

One scholarship (ref. 2018446 here) is for a project that fits within the framework of “plant functional ecology” (see our Welcome and Projects pages to see what that means to us), with the topic to be arrived at through discussion. Depending on the successful candidate’s research strengths the project could involve field-based ecological or physiological studies, glasshouse-based experiments, analyses of trait-environment relationships, theory development – or (ideally) some combination of these approaches. The focus should be on understanding the ecological strategies of species in non-agricultural and non-horticultural settings, and on elucidating broad trends across species, not within single species.

The second scholarship (ref. 2018445 here) is associated with the project, Optimal photosynthetic traits on ecological time-scales. This position will include a substantial fieldwork component, measuring ecophysiological traits in natural vegetation at sites in eastern Australia. Possible topics include (1) The role of soil nutrition in shaping photosynthetic trait variation; and (2) The interplay between plant hydraulic and photosynthetic strategies. Within that framework, the PhD candidate would be expected over time to develop their own research directions. Previous experience in measuring plant physiological properties would be highly regarded.

Essential criteria for both positions include (1) Demonstrated ability to conduct high quality, independent research as part of a completed Masters-level research degree with substantial thesis component. (2) Clear record of academic excellence as an undergraduate. (3) Excellent verbal and written communication skills. (4) Must be able to commence at Macquarie University before 15^th December 2018. Experience in writing up previous research for journal publication will be highly regarded.  From people meeting all of these criteria (more details at Rating Scholarship Applicants website) we can invite some number to discuss detailed research possibilities with a view to applying for the scholarships via the Online Application System. Initial inquiries should be directed to Professor Ian Wright (ian.wright@mq.edu.au).

Two postdoc positions advertised

We have just advertised two three-year postdoc positions. Both positions are aimed towards candidates with a strong publication record, and with 3 or more years relevant experience, post-PhD (“Level B”, in Australian terminology). For someone truly exceptional there is possibility to appoint as a “Senior Research Fellow” (Level C). One position is for an experienced field ecologist or physiologist with expertise in photosynthesis. The other is for someone with a flare for data analysis. Below are the links to the position descriptions on our university website. The closing date for applications is 12^th April.

Postdoctoral Research Fellow in Data Analysis and Modelling (plant functional ecology) – level B/C

Postdoctoral Research Fellow in Plant Functional Ecology (field ecophysiologist) – Level B/C

Two big papers from late 2017

We published two papers in late 2017 that reflected our twin interests of developing first-principles theory for plant function and investigating plant form and function at global scale, and the power of putting these two approaches together:

• Wang H, Prentice IC, Cornwell WK, Keenan TF, Davis TW, Wright IJ, Evans BJ, Peng C (2017). A universal model for carbon dioxide uptake by plants. Nature Plants 3:734-741.
  • This analysis continued the work on “least-cost” theory for photosynthesis (Wright et al 2003 Am Nat; Prentice et al 2014 Ecol Lett), successfully confirming at global scale the optimality-based theory for environmental control of CO2 drawdown during photosynthesis (ci:ca). Next we twinned this approach with photosynthetic coordination theory (Maire et al 2012, and others), allowing us to articulate least-cost theory with a LUE-based model for GPP. This allows us to make first-principles predictions for GPP as a function site climate and elevation, with no need for separate functions for each Plant Functional Type. We envisage this approach as sitting at the core of a ‘next-generation’ vegetation model, to be developed over several years.

In least-cost theory (Wright et al. 2003; Prentice et al. 2014) the optimal ratio of N and water use for photosynthesis is set by the ratio of their unit costs for acquisition and use. A_sat is the light-saturated rate of photosynthesis. Left: purple dots represent situations where transpiration is relatively expensive or, equally, where carboxylation is relatively cheap, corresponding (as predicted, middle panel) to cold sites (a,c) and to dry sites (b, d). Right: Predicted versus observed C_i:C_a (Wang et al. 2017). The dataset (Cornwell et al. in review) is for 3653 species with long-term C_i:C_a estimated from leaf stable carbon isotope ratios.

• Wright IJ, Dong N, Maire V, Prentice IC, Westoby M, Díaz S, Gallagher RV, Jacobs BF, Kooyman R, Law EA, Leishman MR, Niinemets Ü, Reich PB, Sack L, Villar R, Wang H & Wilf P (2017). Global climatic drivers of leaf size. Science 357:917-921.
  • In this project we revisited a century-old question (is there a latitudinal gradient in leaf size?) and a 50-year old question (what are key climatic controls over leaf size variation?). Compiling data for several thousand species around the world, we quantified the latitudinal gradient (larger leaves near the equator) and also interactive effects of site moisture and temperature (and irradiance) as drivers of leaf size variation. Next we demonstrated a new and simple approach to leaf energy balance theory that focuses on maximum leaf size rather than mean trends, giving the ability to make quantitative predictions for maximum feasible leaf sizes as a function of site climate, with broad support at global scale. A key finding was that, overall, the risk of radiative frost damage may be just as influential in limiting leaf sizes as the role of day-time overheating (the traditional” explanation). Leaf size variation has strong consequences for leaf temperature and water use, both key variables in the photosynthetic models that underpin global vegetation models. Is there a role for optimality-based theory for leaf size variation in the next generation of global models?

Predicted geographic trends in maximum leaf size. Each grid cell is color-coded according to the smaller of the two predictions for maximum leaf size (day-time, night-time; see Fig. S13 in Wright et al 2017). Areas coded the deepest shade of blue are those where there may be no effective thermal constraint on maximum leaf size: because sufficient water is generally available for effective transpirational cooling, and warm night-time air temperatures prevent leaves from suffering radiative frost damage.

New paper: leaf economics across the Triassic-Jurassic boundary!

The ratio of leaf dry mass to leaf area (LMA) is a key trait for understanding the leaf economic strategies of plant species, but how can we estimate LMA for species long since gone extinct? Given very nicely preserved fossil leaves, one method is to directly measure the leaf area, and then divide it by an estimated value for leaf dry mass. Back in 2007 we (led by Dana Royer) showed that this estimated value can be calculated, using biomechanical principles, from the width of the petiole – the structure that physically supports the leaf blade.

In a new paper (led by postdoc Wuu Kuang Soh) we have revisited this question of estimating LMA from fossils, this time showing that LMA can be directly estimated from measurements of leaf cuticle thickness. Cuticles fossilize beautifully, for example leaf stomata may be exquisitely preserved. In this work we first showed that cuticle thickness (CT) is a good predictor of LMA across a variety of broad-leaved gymnosperm species (many growing in the Royal Botanic Gardens here in Sydney).

Next, Jenny McElwain (Dublin) sent out a set of fossil leaves from a well-studied sequence in Greenland that includes fossil beds either side of the Triassic-Jurassic boundary (a mass extinction event that occurred approx. 200 million years ago). We developed a method for carefully cutting cross-sections of these fossils, then predicted the LMA of each leaf using the predictive equation derived for living species.

 

Cross-section of a fossil Ginkgoites leaf from the Late Triassic period

Because Jenny and collaborators had already quantified the relative abundance of the various fossil species, we were able to estimate community-weighted mean LMA values, and so ask whether there were clear shifts in plant ecological strategies across the T-J boundary. In short, it looks like the extreme climatic conditions of the T-J boundary selectively knocked out low-LMA species, species that presumably had faster metabolic rates. The Early Jurassic plant communities were not only made up of completely different species to those from the Late Triassic, they also had more stress-tolerant, “conservative” leaf economic strategies.

 

Royer DL, Sack L, Wilf P, Lusk CH, Jordan GJ, Niinemets U, Wright IJ, Westoby M, Cariglino B, Coley PD, Cutter AD, Johnson KR, Labandeira CC, Moles AT, Palmer MB & Valladares F (2007). Fossil leaf economics quantified: calibration, Eocene case study, and implications. Paleobiology 33:574-589.

Soh WK, Wright IJ, Bacon KL, Lenz TI, Steinthorsdottir M, Parnell AC, McElwain JC (2017). Palaeo leaf economics reveal a shift in ecosystem function associated with the end-Triassic mass extinction event. Nature Plants 3:17104.

 

 

 

Congratulations Tim!

Congratulations to Tim Maher for being awarded his Masters (Research), and for achieving a top-band also. Time’s thesis was titled “Withstanding heat waves: Proteomic analysis of adaptive thermotolerance in Eucalyptus grandis seedlings”. His supervisor team consisted of Rachael Gallagher, Mehdi Mirzaei and Ian Wright.