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By Mary O'Callaghan 20 July 2016 4 min read

Blue gum plantation (Eucalyptus globulus). Image: Michael Battaglia, CSIRO

There’s a ‘tree change’ happening across Australia. But it’s not about lifestyle; it’s about carbon dioxide (CO2).

As the concentration of CO2 in the atmosphere continues to climb, there could be an upside for Australia’s 2 million hectares of timber plantations—at least, for those trees that can use additional CO2 to their advantage. Along with water, nutrients and light, CO2 is one of the building blocks of plant growth.

Knowing which trees stand to benefit is the trick. Given the long time periods over which trees grow, compared to many agricultural crops, finding out how they respond to changes in the environment has always been a long-term exercise of planting, measuring and comparing. Finding out how they respond to different levels of CO2 is no different.

Now, Australian research promises a suite of genetics-based tools that will allow plantation managers to test young plants for their genetic ability to thrive in a high CO2 world.

Current methods are slow and expensive

“International research on a range of tree species has shown responses in growth rate varying from almost zero to some quite large increases, but averaging around 20 per cent”, says CSIRO senior scientist Dr Libby Pinkard. “So there is potential for big gains in the forestry industry here. But not all plants will respond the same. We’re trying to pick the winners across a range of environmental conditions.

“Direct measurement of forests hasn’t told us a lot about how trees in Australia might respond to the higher levels of CO2 because it’s hugely expensive to measure,” she adds. “Overseas CO2 trials in forests have cost $50 million to $100 million per species, and they still take a long time, over 20 years, by which time the climate has changed even more. We needed another way.”

The research is a collaboration of CSIRO, ANU and Western Sydney University, and is funded by the Science and Industry Endowment Fund.

A faster, cheaper way

The recent sequencing of the eucalyptus genome, one of the first in trees, paved the way for the faster, cheaper genetics approach.

“We can now look at the genes that determine how a eucalypt will respond to higher levels of CO2,” says Dr Pinkard.

River red gum
River red gum (Eucalyptus camaldulensis). Image: Shannon Dillon, CSIRO

The team is looking at three species of eucalyptus commonly grown in plantations around the world —Eucalyptus camaldulensis (river red gum), Eucalyptus grandis (flooded gum, or rose gum) and Eucalyptus globulus (Tasmanian blue gum).

“If we can identify the molecular markers that make them highly responsive to CO2, we can use this information to rapidly and cheaply screen species for that trait. All other traits being equal, the screening process will allow tree breeders to select trees for field tests much earlier. This could cut down the time it takes for plantation managers to see benefits from tree breeding programs from 20 or more years to maybe five to 10 years.“

The approach is a world first: “No-one is doing this anywhere for CO2 responsiveness in trees. These methods are pretty exciting in that they have potential to really change the approach to genetics in the forest industry, and to improve the resilience and productivity of plantation forests.”

Both nature and nurture affect the outcome

Blue gums behind a windmill and water tank
Blue gums (Eucalyptus globulus). Image: Michael Battaglia, CSIRO

In the lab, the researchers extract DNA from the leaves of trees, and run tests to see if they can identify which parts of the genome change as the CO2 levels change. Using more than 400 genotypes per species, it’s very detailed work, requiring measurements of plant physiology traits, growth rate, photosynthetic rate, and biomass production, and linking these traits to genetic changes.

“We also have to run the tests across different environments to make sure the responses we measure are robust across different growing conditions,” explains Dr Pinkard. “International studies show that under high CO2 levels, trees growing with limited water or on poor soil, for example, are less likely to be able respond positively to high CO2.”

Local conditions such as water availability, site nutrition and the prior management of the site can exert a heavy influence on the outcome, and working out the net effect for tree species is complicated, she adds.

“We also have to look at large trees to see if they respond the same as small trees.“

Seeking guidance from the forestry industry

The goal of the research is to deliver a suite of tools, including a DNA screening test for tree breeders and decision-support tools for forest growers, to help pick the ‘winners’ among each of the three eucalypt species.  The methods could ultimately be applied to a range of other species too.

Today, in Canberra, plantation managers and tree breeders are meeting with researchers at a symposium/workshop entitled ‘Forest industry preparedness for climate change: opportunities from genetics and genomics’. The event is part of an ongoing discussion between scientists and the forest industry on industry adaptation to climate change.

As well as sharing their results to date, the researchers are looking for guidance from the forest industry: “We want to understand their priorities for managing climate changes,” says Dr Pinkard. “For example, are they more concerned about drought or heatwaves, and how might CO2 be advantageous? We also want to know how they’d like the new tools to be transferred to them.”

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