Abstract: To address the issue of lacking data in the non-growing season, we conducted anexperiment in a coastal wetland of the Yellow River Delta from October 29, 2016 to February 9, 2017, by continuously monitoring soil CO₂ concentration and temperature at different soil depths (15, 30, and 45 cm). In order to understand the dynamics of CO₂ efflux and to assess its relationship with soil CO₂ concentration, we measured CO₂ efflux in March 3-5 and March 16-18, 2017. The results showed that soil CO₂ concentration significantly increased with the increases of soil depth. At the same depth, soil CO₂ concentration was significantly higher in autumn than in winter. There was strong diurnal variation in CO₂ efflux, which was consistent with the variation of surface soil temperature. The temperature sensitivity coefficients (Q₁₀) of soil respiration were 3.49-3.74. There was a significant positive correlation between CO₂ efflux and soil CO₂ concentration or soil temperature. Using the derived relationships, we estimated CO₂ efflux for the non-growing season, and found that the three models produced similar magnitudes and variations, i.e., 0.44 to 0.57, -0.18 to 0.01 and 0.09 to 0.13 μmol·m^-2·s^-1 for the maximum, the minimum and the mean values, respectively. Our results demonstrated the effects of soil carbon transformation in nongrowing season on carbon cycling of the Yellow River Delta wetland.

Key words: forest community, plant flora, geographic pattern, hotspot area, Taihang Mountains