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). fig1a

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.

 

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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.

 

 

 

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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.

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Rachael awarded an ARC DECRA!!

Hearty congratulations to Rachael Gallagher who has been awarded a prestigious 3-year Discovery Early Career Researcher Award by the Australian Research Council. The title of Rachael’s proposal is  “Life on the edge: how species interactions shape range boundaries”.

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The new plant growth chambers have arrived!

Exciting times! In late 2015 we secured funding to replace a number of aging controlled-environment growth chambers with state-of-the-art Conviron chambers, replete with light, temperature, humidity and [CO2] control. The new chambers arrived today. Over the next few weeks these will be installed and this very important area of the Plant Growth Facility will be refurbished. This follows on from other major works carried out over the last year, including replacing glasshouse lighting systems with high-efficiency (and very bright) LED lights, and replacing aging glasshouse side-walls and roofs. Now, to do some research!

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One of the chambers, arriving by crane

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Masood (Facility Manager), modelling one of the new Conviron chambers

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The beautiful pink glow of LED lighting

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Congratulations Saskia!

Hearty congratulations to Saskia Grootemaat who handed in her PhD thesis last week! Her thesis is titled “Plant traits and their effect on fire and decomposition”. Supervisors: Ian Wright, Hans Cornelissen (Vrije U.), Peter van Bodegom (U. Leiden).

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L-R: Ian Wright, Saskia Grootemaat, Michelle Leishman (Head of Department).

Saskia James graduation

James Lawson, Anthony Manea (PIREL lab) and Saskia Grootemaat in their graduation day finery.

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Welcome René!

René Heim is a new PhD candidate jointly enrolled at Macquarie University and U. Hamburg. His research combines spectral vegetation sensing, data mining, phytopathology and plant functional ecology. René will initially focus on the invasive rust Puccinia psidii (Myrtle Rust), a threat to the native plant family Myrtaceae and to many Australian ecosystems, and to the economy. René has his own blogsite here.

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Rachael wins a NSW Young Tall Poppy Award!

Huge congratulations to Rachael Gallagher for being awarded a NSW Young Tall Poppy Award. See MQ news piece here. The Tall Poppy awards , run by the Australian Institute of Policy and Science (AIPS), recognise and celebrate intellectual and scientific excellence among Australia’s early career researchers, and also talent and passion for communication. As such, Rachael will spend a year sharing her knowledge with school students, teachers and the broader community through workshops, seminars and public lectures.

2015-10-21-18.50.49 NSW Tall Poppy photo 2015 (with Rachael G)

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