Fungi found in plants may not be the answer to mitigating climate change by storing additional carbon in soils as some previously thought, according to an international team of plant biologists.
The researchers found that increased carbon dioxide stimulates the growth of arbuscular mycorrhizal fungi (AMF) -- a type of fungus that is often found in the roots of most land plants -- which then leads to higher decomposition rates of organic materials, said Lei Cheng, post doctorate fellow in plant science, Penn State. This decomposition releases more carbon dioxide back into the air, which means that terrestrial ecosystems may have limited capacity to halt climate change by cleaning up excessive greenhouse gases, according to the researchers.
"Prior to our study, there have been few studies on whether elevated levels of carbon dioxide would stimulate organic carbon decomposition through AMF," said Cheng.
To study the effect of higher levels of carbon dioxide on AMF-mediated decomposition, the researchers conducted four experiments, two in greenhouses and two in fields to mimic the earth's expected North American atmospheric levels of carbon dioxide. They studied plots of a wild oat species, which is native to Eurasia and now common in North American grasslands, and wheat.
In the experiments, one plot was treated with AMF, the other did not have the fungus. Both plots were exposed to higher than currently existing carbon dioxide levels. After a ten-week gestation period, the sample of plants with AMF had 9 percent less carbon in the soil than the plot that was not treated with AMF, indicating that the carbon was released back into the atmosphere.
"Basically, we showed that elevated carbon dioxide increases carbon allocation to AMF to increase plant nitrogen uptake, and higher AMF facilitate organic residue decomposition which releases carbon dioxide into the air," said Cheng.
Elevated levels of carbon dioxide did significantly increas
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