Larger Q10 of carbon decomposition in finer soil particles does not bring long‐lasting dependence of Q10 on soil texture

Abstract

SummarySoil particle‐size fractionation is a reliable approach for the separation of carbon (C) pools with different stabilities. Our previous study found that C decomposition in fine soil particles had greater temperature sensitivity (Q10) than in coarse particles in grassland and forest soils. However, it is not known whether this phenomenon occurs in cropland soil and whether it generally suggests a dependence of Q10 on soil texture. We carried out a 107‐day incubation of isolated soil particles from cropland soil, including paddy and upland, with contrasting fertilizer applications. The incubation was carried out over three short‐term cycles of sequentially changing temperatures between 5 and 30°C at 5°C intervals. The results indicated that C decomposition was faster in the sand (>50 μm) fraction than in the silt (2–50 μm) and clay (<2 μm) fractions. However, Q10 was generally larger in the clay fractions than in the other two fractions for all types of cropland soil, which is in accordance with our previous study. This suggested that the passive C pool is more sensitive to climate warming than the labile C pool. Considering the aforementioned Q10 pattern across soil particles, we hypothesized that fine‐textured soil should have a larger Q10 than coarse‐textured soil. However, we observed this outcome in the first and second temperature cycles only, but not in the third. In conclusion, a larger Q10 in finer soil particles is probably a widespread phenomenon, but it does not bring a long‐lasting dependence of Q10 on soil texture.Highlights Does cropland C flux in finer soil particles have larger Q10 as in grassland and forest? Larger Q10 in clay fractions than in sand particles is widespread. The passive C pool is more sensitive to climate warming than the labile C pool. Larger Q10 in finer soil particles does not bring long‐lasting dependence of Q10 on soil texture.