Ecophysiology is where plant physiology meets ecology: using an understanding of the underlying organismal physiology to address ecological questions such as where different plant species grow and how successful they are. Ecophysiologists are also interested in how plants affect the carbon, water and nutrient cycles, and how plants respond to global change, such as changes in temperature, atmospheric CO2, and water availability.
Ecophysiologists use a range of approaches, in the glasshouse, in the field, and on computers. Glasshouse experiments investigate whole-plant physiological responses to environmental factors. Field studies include both observational studies of plant performance, using a wide range of techniques such as leaf gas exchange, sapflow, eddy covariance, and stable isotopes; and manipulative experiments, such as CO2 and drought manipulations. Computer-based modelling studies are also a key tool for ecophysiologists, allowing us to extrapolate from small-scale experiments to terrestrial ecosystems.
Key outcomes of ecophysiological research include identifying the mechanisms by which plants respond to their environment; quantifying plant growth, carbon storage and water fluxes; and predicting plant ecosystem responses to global change.
Australia is a world leader in plant ecophysiology, with a sizeable community of internationally-recognised scientists and a number of important facilities supporting their research. These facilities include
– The Hawkesbury Forest field site at University of Western Sydney, which includes a large-scale Free-Air CO2 Enrichment (FACE) experiment on native eucalypts, whole-tree chambers for CO2 and T manipulations, rain-out shelters, and experimental plantings
– The Northern Australian Tropical Transect
– Ozflux network of eddy covariance sites
Australian vegetation differs in many respects from other vegetation around the world, enabling useful comparative studies of vegetation function. Australia has geologically old soils, which result in lower nutrients and water holding capacity of the soil. Additionally, Australian vegetation experiences high variability in rainfall, due to the El Nino Southern Oscillation index. It may be argued that this lack of nutrient and water resources means that plants have shifted to longer life spans, with lower plasticity. Further, most of Australia is under a regular fire regime for extended periods. Most vegetation types are routinely burnt, and as a result are generally fire adapted, with the exception of rainforest chenopod shrubs. Features of Australian vegetation also include sclerophyllous leaves and deep roots.
(by Belinda Medlyn & Melanie Zeppel)