Warning over vulnerability of soil carbon to warming

[muriel_volestrangler]

The huge stores of carbon locked in the world's soils are more vulnerable to rising temperatures than previously thought.

Researchers found that microbes in the soil were more likely to enhance the release of CO2 in a warming world.

Soils from colder regions and those with greater amounts of carbon were seen to emit more as temperatures went up.
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The research team found that soils from boreal regions and the Arctic were impacted the most, while arable or managed lands were the only ones where microbes reduced the effects of a temperature change on the amount of carbon dioxide released.

http://www.bbc.co.uk/news/science-environment-29050800

Much of the large amount of carbon stored in soils is released into the atmosphere as carbon dioxide through soil microbial respiration. It is thought that a warming induced stimulation of soil microbial respiration rates could increase soil carbon dioxide emissions and hence induce a positive climate feedback effect, but the response of soil microbial communities to changing temperatures remains uncertain. This paper investigates the role of microbial community level responses in controlling the temperature sensitivity of respiration in soils from the Arctic to the Amazon. The authors find that the microbial community level response enhances the longer-term temperature sensitivity of respiration more often than it reduces it. The strongest enhancing responses are observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions, suggesting that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.
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Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.

http://www.nature.com/nature/journal/v513/n7516/full/nature13604.html

[GliderGuider]

1. The message is clear

We need to get the entire land surface of the Earth under cultivation as soon as possible...