Global warming increases carbon emissions from soil

New research shows that global warming results in more carbon dioxide release from soil across the world. This happens because of the response of microbes present in the soil to warming temperature, say researchers from the University of Exeter who conducted the study.

For the study, samples of soil were collected from areas with different temperatures—from the Arctic to the Amazon rainforest. These samples were incubated and cooled in order to measure the soil respiration. 

The results, published in Nature this week, showed that as a response to an increase in temperature, the microbial communities within the soil released greater levels of carbon dioxide. However, the response was not uniform as soil type varies across different geographical regions and, therefore, reacts differently to changes in temperature. The soil found in boreal and Arctic ecosystems and soil with high carbon-to-nitrogen ratios showed the greatest level of carbon dioxide release in response to temperature change while the managed agricultural soils showed lower release of carbon dioxide.

“The study investigates whether the response of the soil microbial community to changes in temperature increases or decreases the potential for carbon to be lost from soils as the world gets warmer. We found that microbial community responses more often increase, than decrease, the effect of changes in temperature on rates of carbon dioxide release from soils," said Iain Hartley, senior lecturer in physical geography at University of Exeter, who was a part of the study team.
 
“The results of this study can help develop more accurate soil carbon and climate models. The temperature sensitivity of soil microbial respiration is an important determinant for soil C losses with climate change, and major uncertainty in global climate models,” said Kristiina Karhu from the department of forest sciences at University of Helsinki and lead author of the paper. 

“We have no control over how the microbes in natural ecosystems are reacting to climate warming. In the northern Arctic and boreal soils, cold temperatures have limited decomposition and large stocks of decomposable organic matter have accumulated. With increasing temperatures, decomposition of this soil organic matter increases, and there is a risk that large amounts of CO2 can be released into atmosphere, unless increasing plant growth can compensate for the loss of carbon underground. In managed forests and agricultural soils good management can at least partly mitigate soil carbon losses,” added Karhu.

Research: Temperature sensitivity of soil respiration rates enhanced by microbial community response

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