http://www.abc.net.au/science/articles/2012/08/31/3579643.htm
Soil fungi may not be as effective at storing carbon and mitigating the effects of climate change as some scientists had hoped. That’s the conclusion drawn by US researchers who have studied the effect of rising carbon dioxide levels on the fungi that form mutually beneficial relationships with the roots of most plant species.
Many experts have assumed that arbuscular mycorrhizal fungi will play a major part in storing carbon in the soil as CO2 levels rise. But the new study by Shuijin Hu and colleagues from North Carolina State University questions these assumptions. Their study is published this week in the journal Science . The researchers conducted four independent experiments in the lab and in the field. They found that enhancing the activity of these fungi by raising CO2 levels actually promoted the decomposition and release of organic carbon from the soil. The carbon effects seen in this study are also likely to be affected by fertiliser use, says Hu. “Carbon and nitrogen cycles interact, particularly in agro-ecosystems and forage lands where arbuscular mycorrhizal fungi dominate and human perturbations are routine. In these systems, nitrogen fertiliser inputs are high and some of them are emitted as greenhouse gases too.”
“Effective management of nitrogen fertilisers may create a win-win situation,” he says, “enhancing carbon sequestration, while reducing nitrogen-based greenhouse emissions.” To clearly understand the responses of terrestrial carbon cycling to climate change, interactions between carbon and nitrogen cycles must be taken into account, writes George A. Kowalchuk in a separate article in Science. The decomposition seen in the study “presumably results from the activation of soil-borne microbes by the increased flux of -derived substrates,” says Kowalchuk, a microbial ecologist from the Netherlands Institute of Ecology.
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