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., Q 10) determines how strong the feedback from global warming may be on the atmospheric CO 2 concentration; thus, understanding the factors influencing the interannual variation in Q 10 is important for accurately estimating local soil carbon cycle. In situ SOC mineralization rate was measured using an automated CO 2 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.