Effects of photosynthesis on soil respiration of Quercus variabilis plantation in southern Taihang Mountain of northern China

  Objective  This study aims to explore the effects of photosynthesis on soil respiration and build a new soil respiration model, which can improve the interpretation of soil respiration changes in the study area, and provide a theoretical basis for accurately estimating the intensity of soil respiration and the carbon budget in southern foot of the Taihang Mountains, northern China.

  Method  Taking the Quercus variabilis on the southern foot of Taihang Mountain as research object using field control experiments, which compared the treatment of cut roots and non-cut roots and the contribution rate of photosynthetic products to soil respiration. Through the model fitting of soil respiration, soil temperature, humidity and photosynthesis data, we explored whether adding photosynthetic factors can optimize the traditional soil respiration model.

  Result  On the hourly scale, soil temperature was the main factor affecting the soil respiration of the cork oak forests, and the relationship between them was significant (R² = 0.74, P < 0.01). On the day scale, the curves of soil respiration and temperature were not consistent. The soil temperature in each month showed a continuous increase from 10:00−18:00, but the soil respiration rate did not show the same law. The daily change of soil respiration showed a single peak or a double peak curve, and the highest point generally appeared between 14:00−16:00. The temperature sensitivity (Q₁₀ values) dissimilated under different conditions with the root cutting treatment component (1.90) > control group score (1.77). Results showed that forest photosynthesis can account for up to 36.5% of soil respiration, and there was a significant linear correlation between photosynthesis and soil respiration (R² = 0.39, P < 0.01). Regression model with adding photosynthesis variable significantly improved the fitting R².

  Conclusion  Soil respiration is a complex process affected by multiple factors. It is not comprehensive to analyze and estimate soil respiration based on the function of a single factor. Soil temperature can only explain 74% variations of soil respiration, whereas soil temperature and photosynthesis in the model jointly determine the variation of soil respiration above 80%, and the model fit degree can reach up to 0.81.