Category Archives: Uncategorized

Dr Lu Yaojie

Lu’s PhD thesis, “Optimal and Competitive Stomatal Behaviour”, has passed examination with flying colours. Congratulations to both Lu and his primary supervisor Dr Remko Duursma! Lu has published on optimal stomatal behaviour already and has a second outstanding contribution on competitive behaviour in preparation.

Advertisements

New EucFACE paper

The EucFACE experiment, running since Sept 2012, has fumigated a mature eucalyptus woodland in western Sydney. In a paper published today in Nature Climate Change, we show that despite a significant and sustained increase in leaf-level photosynthesis, there has been no detectable increase in above-ground productivity. On average, light-saturated rates of photosynthesis increased by 19%, whereas the 95% CI for the elevated CO2 effect on total above-ground production was (-25%, +9%). It seems likely that low soil P availability restricted the plants’ growth response. Read more about it:

ABC News: Carbon emissions are not soaked up by trees as well as initially thought, say scientists

New Scientist: Global greening may soak up less carbon dioxide than projected

20151211_102721

Journal Club Goes to AGU

Our journal club group has several members off to AGU next week. Here’s a list of their presentations:

Monday, 12 December 2016 08:00 – 12:20 Moscone South – Poster Hall 

Monday, 12 December 2016 16:45 – 17:00 Moscone West – 2006

Thursday, 15 December 2016 13:40 – 13:55 Moscone West – 2020

Friday, 16 December 2016 13:40 – 18:00 Moscone South – Poster Hall

PhD scholarship available

PhD Scholarship Available: Modelling Optimal Plant Behaviour, or Do Plants Hedge Their Bets?

We currently have a PhD scholarship available for a bright, mathematically oriented student to work on an ARC Discovery Project. The project aims to resolve one of the most long-standing questions about the functioning of plants: how much of the carbon that they take up in photosynthesis do they use immediately for growth, and how much do they keep in reserve as insurance for the future? The answer to this question is urgently needed to understand how plants respond to environmental change, and how vulnerable they are to stresses such as drought.

The student will benefit from the superlative research environment here at HIE and will also work with our outstanding collaborators, Roderick Dewar at ANU and Mat Williams at Edinburgh University (UK). The scholarship is open to international candidates. The project involves optimisation techniques such as calculus of variations so the student must have a good maths background. I strongly encourage women with this background to apply.

More information here or please email me: b.medlyn – at – westernsydney.edu.au

Closing date: 5 February 2017

Journal Club Spots Major Error in Nature Paper

In journal club last year we read Michaletz et al. (2014) “Convergence of terrestrial plant production across global climate gradients” Nature doi:10.1038/nature13470 along with the critique by Chu et al. (2015) in Global Change Biology.

The paper tests whether Net Primary Production (NPP) is more strongly related to climate or to stand biomass and age, using a dataset of NPP compiled from a number of sources. We found it a bit odd that about 90% of the 1200 entries in the dataset came from just one source – a Chinese PhD thesis from 1996. PhD student Jim Yang downloaded the thesis and translated the relevant bits and we realised that the “data” were not measured at all, but modelled as a function of stand biomass and age. Clearly such “data” cannot be used to test for relationships with biomass and age.

To their credit, Michaletz et al. responded rapidly when we emailed them about this issue (that can’t have been a nice email to receive!) They submitted a correction to Nature in early January and it has finally been published, along with a revised version of their dataset which contains just 138 entries.

The debate over the analysis by Michaletz et al. will no doubt continue (see Chu et al. 2015) but at least it can now do so with a considerably less flawed dataset. A win for journal club!

Heatwave Surprise

Our new paper in Nature Scientific Reports shows that patterns of stomatal behaviour around the world have surprising ramifications for global climate. Previously our ecosystem modelling group showed clear differences in stomatal behaviour among plant functional types, based on datasets contributed by collaborators around the globe (Lin et al. 2015 Nature Climate Change).  Now working with climate modellers, we find that these differences in leaf-level stomatal behaviour imply differences in ecosystem-scale water use – with major consequences for land surface temperatures and the number of heatwaves in future. Heatwaves in the northern hemisphere in the middle of this century may be up to 5 degrees C higher than previously estimated. There is media coverage at phys.org and the Sydney Morning Herald or you can read the full paper (open access) here:

Nature Scientific Reports “Impact of the representation of stomatal conductance on model projections of heatwave intensity” (Jatin Kala, Martin G. De Kauwe, Andy J. Pitman, Belinda E. Medlyn, Ying-Ping Wang, Ruth Lorenz & Sarah E. Perkins-Kirkpatrick)