Abstract: Carbon cycling in forest ecosystem can be influenced by atmospheric carbon dioxide (CO₂) elevation and nitrogen (N) deposition. A simulation experiment was conducted to investigate the effect of CO₂ elevation and N deposition on soil carbon cycling in midsubtropical forests. In this experiment, soil respiration was measured for one year using Li-Cor 8100 infrared gas analyzer. Compared with the control treatment, soil respiration rate was respectively increased by 24.4% and 27.9% in CO₂ elevation and N deposition treatments, while it was increased by 46.5% in the combined treatment of CO₂ elevation and N deposition. Correlation analysis showed that soil respiration was significantly positively correlated to soil temperature and negatively to soil moisture. The temperature sensitivity of soil respiration was also affected by CO₂ elevation and N deposition. The temperature sensitivity of soil respiration was slightly increased by CO₂ elevation, but decreased by N deposition. Our findings suggest that the release of soil organic carbon to the atmosphere through soil respiration is possibly increased in the context of CO₂ elevation and N deposition in midsubtropical forest ecosystems, and the sensitivity of the response of soil organic carbon decomposition to changes in environmental temperature is decreased.

Key words: wheat, tillage structure, canopy structure, organic fertilizer, path analysis.