Spatial heterogeneity and driving factors of temperature sensitivity of soil respiration (Q10) at national scale

Abstract

Temperature sensitivity of soil respiration (Q10) plays an important role in terrestrial soil carbon-climate feedback. However, Q10 exhibits significant spatial heterogeneity on a large scale, and the factors influencing its spatial variability are not yet fully understood. In this research, we collected Q10 values from 236 field studies in China to explore the spatial heterogeneity and controlling factors of Q10 values at national scale. The relative importance of different climate factors such as annual average temperature (MAT), annual average temperature (MAP) and evapotranspiration (ET), soil geochemical factors including pH, soil organic carbon, soil total nitrogen, C/N, metal oxides, vegetation types and geological backgrounds in predicting Q10 values were explored using a random forest model. The study found that the range of Q10 values in China is 1.17–5.51, with a median of 2.3 and a mean of 2.47. The main influencing factors of the spatial variation of temperature sensitivity of soil respiration Q10 at the national scale are the supply and quality of soil respiration substrates. The more soil organic carbon content, the bigger the Q10. The more difficult it is to decompose (the more complex the molecular structure presented by correlations between Q10 and C/N, and the more mineral-bounded organic carbon presented by correlations between Q10 and FeO), the stronger the temperature sensitivity of soil respiration. In comparison, the influence of climate factors on Q10 is less important and complex, Q10 increases nonlinearly with the increase of ET and decreases with the increase of temperature. The Q10 value is higher when the precipitation is moderate (800-1200 mm), and decreases when there is excessive or insufficient rainfall. In summary, the interaction between soil geochemical factors and climate controls the storage and turnover of soil organic carbon, and soil geochemistry plays the most important role. The results of this study are helpful for accurately assessing the global soil organic carbon storage and spatiotemporal changes, and are of great significance for studying the feedback mechanism of organic carbon under the background of global carbon cycle and global warming.