Less increase in apparent than intrinsic Q10 of soil carbon release

Background/Question/Methods

Soil is the largest terrestrial carbon (C) pool and the decomposition of soil organic carbon (SOC) is critical for global C cycle and the feedback to climate change. Increasing evidences have demonstrated that labile and more recalcitrant SOC pools may have different Q₁₀s, but how Q₁₀ varies among different sub-pools is under debate. Here we compared three previous methods used for estimating Q₁₀ and developed a new method to determine the temperature sensitivity of soil C release using a data set from a laboratory incubation experiment. In the new method, a three-pool (fast, slow, and passive) model with transfer among pools was used to simulate the cumulative respired C at both incubation temperatures (25 ⁰C and 35⁰C) and estimate the intrinsic and apparent Q₁₀s.

Results/Conclusions

Generally, recalcitrant C had greater Q₁₀ than labile carbon for all the methods. The results from the new method showed that passive pool had the greatest intrinsic Q₁₀, followed by slow pool, and fast pool had the lowest intrinsic Q₁₀. This is according with Arrhenius law. However, because of transfers among soil C pools, fast C pool did not exhaust during early days, and even contributed about 40% to total respiration at the end of incubation. Therefore, increase in apparent Q₁₀ was much less than that in intrinsic Q₁₀. Overall, in the context of high contribution of fast C pool resulted from continuous labile C input and transfer in natural conditions, increase in apparent Q₁₀ of soil C release seems to be little, which suggests that the positive feedback of soil C release to climate change may not be as serious as expected.