Responses of the contents and stoichiometry of soil carbon, nitrogen, and phosphorus to elevated atmospheric CO₂ concentration and warming in paddy field.

To study the effects of elevated atmospheric CO₂ concentration and warming on the contents and stoichio-metry of soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) in paddy field is of great significance for understanding the functions of paddy ecosystem under climate change. Based on the T-FACE platform, we conducted an experiment with four treatments: ambient conditions (CK); elevated atmospheric CO₂ concentration up to 600 μmol·mol^-1; warming of canopy air by 2 ℃ over ambient; elevated atmospheric CO₂ concentration up to 600 μmol·mol^-1 combined with warming of canopy air by 2 ℃ over ambient. The contents of SOC, TN, TP, soil organic carbon composition, soil bulk density (BD), soil water content (SWC) and particle size composition were measured. Using variance analysis and Pearson correlation analysis, we explored the influencing mechanisms of climate change and soil physicochemical properties on the contents and stoichiometry of SOC, TN, and TP. The results showed that elevated atmospheric CO₂ concentration increased the accumulation of SOC, TN, and TP. Warming caused the loss of SOC accumulation, promoted TN accumulation, with limited effect on TP accumulation. The effects of combined elevated atmospheric CO₂ concentration and warming on SOC, TN, and TP were in line with the effects of single warming treatment, indicating that warming had greater impacts on SOC, TN and TP than elevated atmospheric CO₂ concentration. Elevated atmospheric CO₂ concentration and warming overall decreased soil C/N, C/P and C/N/P values in the 0-100 cm layer, indicating that climate change was not conducive to the stability and burial potential of SOC. The contents and stoichiometry of SOC, TN, and TP were positively correlated with organic carbon components and soil water content, negatively correlated with bulk density, and not correlated with particle size composition. The relationships between soil stoichiometry characteristics (<i>e.g.</i>, SOC, TN, and C/P) in the 0-30 cm layer and elevated atmospheric CO₂ concentration were relatively close, while that between soil stoichiometry characteristics (<i>e.g.</i>, SOC, TP, C/N, and C/P) in the 30-100 cm layer and warming were relatively close, indicating that the response mechanisms of soil stoichiometry to climate change differed for topsoil and subsoil in paddy field.