Abstract: Photosynthesis regulates soil respiration by providing substrate for soil respiration, which has received more and more attention. Therefore, photosynthesis becomes an important parameter in constructing soil respiration model. In this study, we assessed the role of photosynthesis in regulating soil CO₂ flux in a Keerqin sandy grassland. The results showed that soil temperature was the most significant factor influencing soil respiration. The temperature sensitivity (Q₁₀ values) dissimilated under different photosynthetic conditions, with nighttime (3.03) > daytime (2.12), daily mean (2.41) > 8:00-10:00 a.m. (2.32). Results from partial correlation analysis showed that photosynthesis was an important factor affecting soil respiration (r=0.72, P<0.01). There was a significantly linear positive correlation between photosynthesis and soil respiration (R²=0.49,P<0.01), with a slope of 0.24. Regression model with adding photosynthesis variable significantly improved the fitting R² from 0.73-0.75 to 0.81-0.85 and the power+exponential function, linear+exponential function, and exponential+exponential function all had a good fitting degree in model selection.

Key words: desert steppe, Artemisia scoparia, plasticity index, heterogeneous habitat, population dynamics