Temperature sensitivity of soil respiration rates enhanced by microbial community response

Microbial community responses in soils from the Arctic to the Amazon often enhance the longer-term temperature sensitivity of respiration, particularly in soils with high carbon-to-nitrogen ratios and in soils from cold regions, suggesting that carbon stored in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted. 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. Soils store about four times as much carbon as plant biomass1, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide2. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature3. 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 change4. 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 decrease5,6,7 or increase8,9 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.