Interactive comment on “ Soil moisture influenced 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.

Attached pictures. The location of PVC collar in our plots Table 1. SOC mineralization rate (μ mol m −2 s −1 ) in summer (July 11, 2008) and winter (November 18, 2008). Data are represented as mean ± S.D of five collars (page 20, line 491-494). SOC  For instance, "Annual cumulative SOC mineralization rate was estimated by different methods, including linear interpolation method, modeled method, and unit conversion method. The results clearly showed that there was no significant difference in the estimates of annual cumulative SOC mineralization rate between linear interpolation and modeled method, and the modeled method could well predict the SOC mineralization rate in most cases from 2008 to 2013 (Fig. 6), which was in line with the previous studies (Tang et al., 2005). However, unit conversion method seriously overestimated annual cumulative SOC mineralization rate (Table 4). This can be attributed to the following reasons: 1) the study site has a continental monsoon climate with 60% of rainfall occurring from July to September (rainy season), thus the study site is hot and rainy in the rainy season, but cool and dry in the non-rainy season; and 2) SOC mineralization rate in the rainy and non-rainy season is largely the same, but the duration of rainy season is only a quarter of a year. Thus, the SOC mineralization rate was much greater in rainy season than in non-rainy season, thus resulting in an overestimation of cumulative SOC mineralization rate in a given year (page 13 and 14, line 305-321).
In conclusion, linear interpolation method is a simple and controllable method for estimating annual cumulative SOC mineralization rate (Schindlbacher et al., 2014;Shi et al., 2014). Although the modeled method can well estimate annual cumulative SOC mineralization rate, it is limited in practice as it needs daily soil temperature and moisture.
R：Yes, we had revised the order for Table 1 and Table 2 in the 3.1 Interannual variation in Q 10 sections . For instance, "the annual cumulative SOC mineralization ranged from 226 g C m −2 y −1 (2012) to 298 g C m −2 y −1 (2009), with a mean of 253 g C m −2 y −1 and a CV of 13% (Table 2), and the annual Q 10 in our sites was 1.65 in 2008, 1.94 in 2009, 1.72 in 2010, 1.48 in 2011, 1.86 in 2012, and 1.55 in 2013, respectively, with a mean Q 10 of 1.72 and a CV of 10% (Table 3) " (page 9, line 205-209).
QII-8：P1459 L20: Again, please add the mean annual SOC mineralization rate using the unit of cCm-2yr-1 for readers' reference.
QII-11：P1461 L12: It seems the rainfall "distribution" was not examined in the current MS R: In the 3.2 Interannual variations in soil microclimate sections, interannual variation in rainfall distribution was examined. For instance, "Annual precipitation showed a significant annual variation ( Fig.1 and Table 2 QII-13： P1461 L21: Please remove "However".
R: Yes, "However" was deleted from our old manuscripts. the annual cumulative SOC mineralization ranged from 226 to 298 g C m −2 y −1 , with a 35 mean of (, with mean value of mean=253 g C m −2 y −1 ;and a CV =of 13%), annual 36 Q 10 ranged from 1.48 to 1.94, with a mean value of (mean=1.70; and a CV =of

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The temporal variation in the SOC mineralization rate was correlated with that of  (Table 1). 239 240