Jet lagged trees hold clues to storing carbon

Similar biological processes that give international travellers the dreaded jetlag have been found to also affect plants and entire ecosystems.

A recent international study led by the University of Western Sydney's Hawkesbury Institute for the Environment, has found the internal biological clock that gets altered in humans when travelling across time zones, leading to jetlag, may also operate at the ecosystem level to regulate plant photosynthesis.

"If you could move a whole forest from Sydney to Barcelona all of the trees – in fact the whole ecosystem – would likely have the plant equivalent of jetlag," says Dr Víctor Resco de Dios, from the Hawkesbury Institute for the Environment and lead author on the study published in Global Change Biology.

Plant photosynthesis responds strongly and quickly to changes in the environment. The most obvious change happens after the sun sets each evening when no photosynthesis occurs because there is no light.

Dr Resco de Dios says it has been known for some time that plants transplanted into special 'growth chambers' where the light, temperature and other environmental factors are kept constant – an artificial perpetual day – will continue to have higher photosynthesis during the hours they would have normally been exposed to sunlight.

"All environmental conditions in the chambers are constant, yet the plants continue to function as if there is still night and day. They do eventually adjust to the new conditions but initially their biological clocks persist with the old routine – just as we humans do when we travel between time zones," he says.

Dr Resco de Dios and his international collaborators in Spain, the US and the UK, tested whether this internal clock, or circadian rhythm, found within plants can also affect a whole ecosystem.

Enclosing a whole forest within a growth chamber isn't possible. So, Dr Resco de Dios and his team cleverly revealed the effect using observational data collected from forests around the world.

Sensors mounted on towers in forests dotted across the globe, including one recently installed at the University of Western Sydney, constantly measure the activity of the local ecosystem.  Carbon dioxide levels, local weather conditions and other key variables are monitored to provide a snapshot of ecosystem activity.

The team applied a series of filters to the collected international data to decouple ecosystem level data of carbon assimilation – the amount of carbon locked away by plants - from the variation in the environment.

"We found that the daily variation in ecosystem carbon exchange after removing environmental effects was consistent with fluctuations driven by the biological clock and other endogenous processes, that is, other processes within the plants," says Dr Resco de Dios.

"One of the most remarkable aspects of this finding is that the effect of a genetic process, such as this internal biological clock, could also be seen at the ecosystem level."

Dr Resco de Dios says while there's limited value in knowing plants could experience jet lag – "few forests are moved across international time zones" – a greater understanding of the biological clock, and other internal regulators of plant activity, could potentially improve even further our, already quite accurate, carbon exchange models.

"The research results provide a much better understanding of ecosystem function and its capacity to store carbon which is essential in an era of climate change and carbon accounting," he says.

The research is fully documented in the recently published article:

Endogenous circadian regulation of carbon dioxide exchange in terrestrial ecosystems in the online journal Global Change Biology.


29 March 2012

Contact: Paul Grocott, Senior Media Officer