Soil respiration and carbon loss relationship with temperature and land use conversion in freeze-thaw agricultural area

摘要

Soil respiration (R_s) was hypothesized to have a special response pattern to soil temperature and land use conversion in the freeze-thaw area. The R_s differences of eight types of land use conversions during agricultural development were observed and the impacts of R_s on soil organic carbon (SOC) loss were assessed. The land use conversions during last three decades were categorized into eight types, and the 141 SOC sampling sites were grouped by conversion type. The typical soil sampling sites were subsequently selected for monitoring of soil temperature and R_s of each land use conversion types. The R_s correlations with temperature at difference depths and different conversion types were identified with statistical analysis. The empirical mean error model and the biophysical theoretical model with Arrhenius equation about the R_s sensitivity to temperature were both analyzed and shared the similar patterns. The temperature dependence of soil respiration (Q_(10)) analysis further demonstrated that the averaged value of eight types of land use in this freeze-thaw agricultural area ranged from 1.15 to 1.73, which was lower than the other cold areas. The temperature dependence analysis demonstrated that the R_s in the top layer of natural land covers was more sensitive to temperature and experienced a large vertical difference. The natural land covers exhibited smaller R_s and the farmlands had the bigger value due to tillage practices. The positive relationships between SOC loss and R_s were identified, which demonstrated that R_s was the key chain for SOC loss during land use conversion. The spatial-vertical distributions of SOC concentration with the 1.5-km grid sampling showed that the more SOC loss in the farmland, which was coincided with the higher R_s in farmlands. The analysis of R_s dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area. The analysis of R_s dynamics provided an innovative explanation for SOC loss in the freeze-thaw agricultural area.