| Teaching | Research | Publications |

 

 

Ross McMurtrie has more than 25 years research experience (at UNSW and earlier at CSIRO Forest Research) in the field of process-based modelling of terrestrial ecosystem function. Research has focused on the roles played by plant eco-physiology, changing atmospheric and climatic conditions, and soil-nutrient cycling, in regulating the carbon balance of local and global terrestrial ecosystems over contrasting timescales. The McMurtrie lab at UNSW currently includes two Research Fellows, Drs Belinda Medlyn and Dr David Pepper, and post-graduate students David Dore and Sara Hely.

 

Our research falls into 4 topic areas:

Our research in each of these area combines development of detailed mechanistic simulation models and analyses of more mathematically tractable simplified models of ecosystem function. Our forest models, BIOMASS, G'DAY and MAESTRA, have been used to investigate impacts of climate and land-use change, to analyse sustainability, and to simulate carbon fluxes of grassland, savanna and forest ecosystems in Australia, Africa, India, New Zealand, Europe (France, Sweden, Scotland) and USA.

 

Much of our modelling work involves using relatively simple mathematical models to explain empirically observed plant and ecosystem phenomena. Our focus on simple models stems originally from the influence of Ross McMurtrie's PhD supervisor, (now) Lord Robert May, who championed the use of simple models to explain biological phenomena. This type of research is fundamental to many other scientific fields, including animal ecology, but is not widely practised in terrestrial plant ecology and plant physiology, where it is more common to construct relatively complex simulation models as research tools. In this respect we have made significant contributions to understanding of plant ecosystem function, by using simple mechanistic models to account for the following empirically observed plant and ecosystem phenomena:

 

Plant physiological phenomena (Publications 40, 42, 48):
Light acclimation: According to our models of carbon (C) substrate dynamics, leaves grown in high light tend towards a steady state with a higher protein content, and hence higher photosynthetic capacity, than leaves grown in low light (i.e. the model predicts photosynthetic light acclimation as a steady-state phenomenon).

 

Light-use efficiency (LUE): For well-watered plants, net primary productivity (NPP) is approximately proportional to absorbed radiation; our models provide a mechanistic explanation for the observed approximate constancy of plant LUE.

 

Carbon-use efficiency (CUE): In a constant environment, an approximately constant fraction of the CO₂ taken up during photosynthesis is subsequently lost in plant respiration (i.e. carbon-use efficiency (CUE) is approximately constant).

 

Leaf acclimation to CO₂: modelled LUE has a maximum associated with an optimal trade-off between leaf photosynthesis and leaf respiration. The point of optimal balance between photosynthesis and respiration is predicted at elevated CO₂ to shift to lower protein contents, thus providing an adaptive interpretation of the photosynthetic down-regulation often observed at elevated CO₂. Concurrent with the predicted decline in leaf protein content at elevated CO₂, the model predicts an increase in CUE, consistent with several short-term CO₂-enrichment experiments.

 

Acclimation of plant respiration (R) to temperature (T): our work accounts for the experimental observation that, whereas R is highly sensitive to T in the short-term, on longer timescales (several days) the respiration/photosynthesis ratio acclimates to temperature (42).

Ecosystem phenomena:
Sustainability (37, 39, 69, 71): Our models lead to an unambiguous, mathematical definition of ecological sustainability in relation to management practices. Sustainable forest productivity can be evaluated from a simple graphical representation of growth and silvicultural practices.

 

CO₂ -fertilisation effect (CFE) (27, 29, 35, 44, 45): We have analysed how the direct effect of high CO₂ on plant photosynthetic production is constrained by longer-term soil feedbacks, and have shown how the CFE can be evaluated on different timescales. We have explained why the CFE tends to be reduced under N-limitation, but amplified under water-limitation.