Carbon Stored in World's Soils May be More Vulnerable to Climate Change Than Previously Thought

Carbon is soils may be more vulnerable to climate change than first expected. Scientists have found that the response of soil microbial communities to changes in temperature actually increases the risk for more carbon dioxide to be released from the world's soils.

As our climate warms, rising temperatures have the potential to stimulate decomposition rates in soils. This, in turn, can cause these soils to release large quantities of carbon dioxide into the atmosphere, which would further exacerbate warming. Now, scientists have taken a closer look at the microbial communities in these soils to see how they might respond to warmer temperatures.

In order to examine how microbes react, the scientists collected soils from a thermal gradient from the Arctic to the Amazon rainforest. They then tested these soils to see how the microbial communities responded to temperature. In the end, they found that, contrary to expectations, microbial communities actually caused rates of carbon dioxide release from soils to increase with temperature.

"Because soils store more than twice as much carbon than the atmosphere, changes in rates of decomposition and carbon dioxide release from soil could be very important," said Kristiina Karhu, one of the researchers, in a news release. "Our findings suggest that warming will increase the activity of soil microbes to a greater extent than was previously expected, which could have implications for future rates of climate change."

That said, the response of microbes in the soils differed across different geographical regions and ecosystem types. Agricultural soils in particular were the only soils in which microbial community responses reduced the effects of a temperature change on rates of carbon dioxide release. The great stimulation, in contrast, was found in soils with the greatest carbon content and from boreal and arctic ecosystems.

"It is only relatively recently that we have recognized how important it is to understand soil microbial community responses to changes in temperature," said Iain Hartley, one of the researchers. "Big advances have been made in recent years, and there are now models that simulate key microbial processes. We have a good opportunity to really advance this subject, and improve predictions of rates of carbon dioxide release from soils under global warming, but there is still a huge amount that we need to understand better."

The findings are published in the journal Nature.