Soil moisture influence on the interannual variation in temperature sensitivity of soil organic carbon mineralization in the Loess Plateau

Abstract. Temperature sensitivity of soil organic carbon (SOC) mineralization (i.e., Q₁₀) determines how strong the feedback from global warming may be on the atmospheric CO₂ concentration; thus, understanding the factors influencing the interannual variation in Q₁₀ is important for accurately estimating local soil carbon cycle. In situ SOC mineralization rate was measured using an automated CO₂ flux system (Li-8100) in long-term bare fallow soil in the Loess Plateau (35°12' N, 107°40' E) in Changwu, Shaanxi, China from 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m⁻² yr⁻¹, with a mean of 253 g C m⁻² yr⁻¹ and a coefficient of variation (CV) of 13%, annual Q₁₀ ranged from 1.48 to 1.94, with a mean of 1.70 and a CV of 10%, and annual soil moisture content ranged from 38.6 to 50.7% soil water-filled pore space (WFPS), with a mean of 43.8% WFPS and a CV of 11%, which were mainly affected by the frequency and distribution of precipitation. Annual Q₁₀ showed a quadratic correlation with annual mean soil moisture content. In conclusion, understanding of the relationships between interannual variation in Q₁₀, soil moisture, and precipitation are important to accurately estimate the local carbon cycle, especially under the changing climate.