[Interannual Variations of Soil Respiration and Its Temperature Sensitivity in an Orchard in Jinci Region of Taiyuan City]

Jinci area of Taiyuan city is a former hometown of rice, and with the cutoff of the Jinci spring the land use in the area changed fundamentally from original paddy rice to corn or orchard use. So it is very important to investigate soil respiration after land use change and to analyze the relationship between soil respiration (R_s) and soil temperature (T_s) and soil water content (SWC), and to estimate soil carbon dioxide efflux in the region. For this purpose, we measured R_s for seven years (2006 to 2012) with an interval of 1 to 3 times per month from March to December in a field originally for rice but now Chinese jujube, and analyzed seasonal, annual variations of R_s and relationships between R_s and both T_s and SWC. The results showed that the seasonal variations of R_s against day number of the year could be significantly fitted with a three-parameter Gaussian equation while there was no significant correlation between T_s and SWC. Significant exponential relationship between R_s and T_s over the season was found, but not with SWC. Interannual average estimation of soil efflux between March and December from the soil was (5.32±3.31) μmol·(m²·s)^-1, and was equal to 1690.2 g·m^-2 from the same period ranging from 1294 to 2006 g·m^-2. No significant difference in annual efflux was found between the years. The sensitivity of R_s to T_s, Q₁₀ value, ranged from 1.54-2.20, 1.68-2.48 and 1.82-2.46, respectively, for the T_s measurement at 5, 10 and 15 cm depths. The R_s at 10℃, R₁₀, ranged from 2.37 to 2.81, 2.43 to 3.13 and 2.59 to 3.47μmol·(m²·s)^-1, respectively, for the T_s measurement at 5, 10 and 15 cm depths. Both the Q₁₀ and R₁₀ increased with increasing T_s measurement depth. In comparison with the fitted one-variable of temperature model, the two-variable model combining both the T_s and SWC together could be well used to predict R_s over the season. Our research results can bear important implications for the study of CO₂ efflux in the region and similar regions.