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”.

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!

One of the chambers, arriving by crane

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

The beautiful pink glow of LED lighting

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).

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

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

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.

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.

Science at the Shine Dome 2015

Rachael and Ian recently attended “Science at the Shine Dome 2015”, an anual event and 3-day talkfest at the Australian Academy of Sciences where new Fellows are inducted in to the Academy, various early- and mid-career research (EMCR) awards are made, prizewinners give talks about their research, and EMCRs participate in a range of workshops. Ian was awarded the 2015 Fenner Medal – an award recognising distinguised research in biology, commemorating the outstanding contributions to Australian science by the late Professor FJ Fenner (who, among other things, oversaw the use of Myxoma virus to control plague rabbit populations). Here’s Rachael and Ian looking their fancy best at the annual black-tie dinner: … and Ian attempting to describe global variation in leaf size to a general science audience:

“Science at the Shine Dome” Day two, Canberra on May 26, 2015. PHOTO: MARK GRAHAM

… and the 1950s sci-fi beauty of the Shine Dome at night:

New paper on ecological wood anatomy

The second paper from Kasia Ziemińska’s PhD thesis has just been published in PLoS ONE! Kasia was supervised by Mark Westoby and co-supervised Ian Wright.

Ziemińska K, Westoby M, Wright IJ (2015). Broad anatomical variation within a narrow wood density range — A study of twig wood across 69 Australian angiosperms. PLoS ONE 10:e0124892. [pdf]

SUMMARY

Objectives
Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation within a restricted range of wood density and explore its potential ecological implications.
Methods
Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38–0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity).
Results
Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 |r| 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 |r| 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 |r| 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component.
Conclusions
Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation.

Above: Illustration of wood tissues in twigs of Gomphandra australiana (Icacinaceae). Scale bar corresponds to 100 μm. (Image: K. Ziemińska).

Below: Figure 3 from this paper.

Emma samples the South African savanna!

Elephants blending quickly into the mopane woodland

Emma using the licor to measure Amax

Emma recently returned home to South Africa to complete a field trip in the Phalaborwa region of the Kruger National Park. She collected leaf and wood trait data which will be analysed in conjunction with growth data collected by Tony Swemmer of the South African Environmental Observation Network (SAEON). Emma is interested in growth-trait relations, and the data will contribute to the second chapter of her PhD.

Great help in the field: Mightman and Elijah

Constance sampling biomass in the field

Emma was helped by some fantastic SAEON field assistants, who provided vital tree identification skills and willing smiles.

A rare sighting of wild dog play fighting in the road

Female and male lion lounging in the shad

Besides the usual challenges of collecting leaf physiology data in the field, the Kruger Park offers the unique chance of bumping into an elephant, a rhino, or even lion, all while trying to measure maximum photosynthetic rate using the fairly unwieldy LI-6400. Thankfully nothing dangerous bothered them while working, but they did see some interesting animals driving to and from the sites.

A young male leopard keeping watch from the shade

A giraffe strolling through the savanna, well adapted to reach the tasty leaves at the top of the trees

The vegetation in the study sites ranged from dense mopane woodland to open acacia savanna. Due to a drought this rainy season the grassy layer has taken a beating, but thankfully trees were still photosynthesising.

A typical flat topped acacia savanna scene, except featuring Albizia harveyi and Dichrostachys cinerea

All in all it was a successful trip and should provide some very interesting data from an arid savanna.

New paper! Global soil and climate effects on leaf photosynthetic traits and rates

We’re excited to announce that the online-early version of this paper is now available from the GEB website. Lead author Vincent Maire was a post-doc in our group from 2012-14, and now holds a faculty position at U. Quebec.

Maire V, Wright IJ, Prentice IC, Batjes NH, Bhaskar R, van Bodegom PM, Cornwell WK, Ellsworth D, Niinemets Ü, Ordonez A, Reich PB, Santiago LS (2015, in press). Global soil and climate effects on leaf photosynthetic traits and rates. Global Ecology & Biogeography. DOI 10.1111/geb.12296. [link]

ABSTRACT

Aim The influence of soil properties on photosynthetic traits in higher plants is poorly quantified in comparison with that of climate. We address this situation by quantifying the unique and joint contributions to global leaf-trait variation from soils and climate.

Location Terrestrial ecosystems world-wide.

Methods Using a trait dataset comprising 1509 species from 288 sites, with climate and soil data derived from global datasets, we quantified the effects of 20 soil and 26 climate variables on light-saturated photosynthetic rate (Aarea), stomatal conductance (gs), leaf nitrogen and phosphorus (Narea and Parea) and specific leaf area (SLA) using mixed regression models and multivariate analyses.

Results Soil variables were stronger predictors of leaf traits than climatic variables, except for SLA. On average, Narea, Parea and Aarea increased and SLA decreased with increasing soil pH and with increasing site aridity. gs declined and Parea increased with soil available P (Pavail). Narea was unrelated to total soil N. Joint effects of soil and climate dominated over their unique effects on Narea and Parea, while unique effects of soils dominated for Aarea and gs. Path analysis indicated that variation in Aarea reflected the combined independent influences of Narea and gs, the former promoted by high pH and aridity and the latter by low Pavail.

Main conclusions Three environmental variables were key for explaining variation in leaf traits: soil pH and Pavail, and the climatic moisture index (the ratio of precipitation to potential evapotranspiration). Although the reliability of global soil datasets lags behind that of climate datasets, our results nonetheless provide compelling evidence that both can be jointly used in broad-scale analyses, and that effects uniquely attributable to soil properties are important determinants of leaf photosynthetic traits and rates. A significant future challenge is to better disentangle the covarying physiological, ecological and evolutionary mechanisms that underpin trait–environment relationships.

 

New paper! The role of leaf traits in fire versus decomposition

We’re excited that the first paper from Saskia’s PhD studies has now been accepted for publication!

Grootemaat S, Wright IJ, van Bodegom PM, Cornelissen JHC, Cornwell WK (2015, in press). Burn or rot: different roles of leaf traits in fire versus decomposition. Functional Ecology. DOI: 10.1111/1365-2435.12449.  [link]

Summary
In fire-prone ecosystems, two important alternative fates for leaves are burning in a wildfire (when alive or as litter) or they get consumed (as litter) by decomposers. The influence of leaf traits on litter decomposition rate is reasonably well understood. In contrast, less is known about the influence of leaf traits on leaf and litter flammability. The aim of this study was twofold: (a) to determine which morphological and chemical leaf traits drive flammability; and (b) to determine if different (combinations of) morphological and chemical leaf traits drive interspecific variation in decomposition and litter flammability and, in turn, help us understand the relationship between decomposability and flammability.
To explore the relationships between leaf traits and flammability of individual leaves, we used 32 evergreen perennial plant species from eastern Australia in standardised experimental burns on three types of leaf material (i.e. fresh, dried and senesced). Next, we compared these trait-flammability relationships to trait-decomposability relationships as obtained from a previous decomposition experiment (focusing on senesced leaves only).
Among the three parameters of leaf flammability that we measured, interspecific variation in time to ignition was mainly explained by specific leaf area and moisture content. Flame duration and smoulder duration were mostly explained by leaf dry mass and to a lesser degree by leaf chemistry, i.e. nitrogen, phosphorus and tannin concentrations.
The variation in the decomposition constant across species was unrelated to our measures of flammability. Moreover, different combinations of morphological and chemical leaf properties underpinned the interspecific variation in decomposability and flammability. In contrast to litter flammability, decomposability was driven by lignin and phosphorus concentrations.
The decoupling of flammability and decomposability leads to three possible scenarios for species’ influence on litter fates: (I) fast-decomposing species for which flammability is irrelevant because there will not be enough litter to support a fire; (II) species with slow-decomposing leaves and a high flammability; and (III) species with slow-decomposing leaves and a low flammability. We see potential for making use of the decoupled trait – decomposition – flammability relationships when modelling carbon and nutrient fluxes. Including information on leaf traits in models can improve the prediction of fire behaviour.