Nitrogen Transformation as Influenced by Soil Microbial Nitrogen under Carbon Dioxide Enrichment Induced in Created Riparian Wetlands

Limited research has been conducted on how atmospheric carbon dioxide (CO₂) affects water and soil nitrogen (N) transformation in wetland ecosystems. A stable isotope technique is suitable for conducting a detailed investigation of mechanistic nutrient transformations. Nutrient ammonium sulfate (NH₄)₂SO₄ input in culture water under elevated CO₂ (700 μL L^?1) and ambient CO₂ (380 μL L^?1) was studied to analyze N transformations with N blanks for both water and soil. It was measured by ¹⁵N pool dilution using analytical equations in a riparian wetland during a 3-month period. Soil gross ammonium (NH₄ ⁺) mineralization and consumption rates increased significantly by 22% and 404%, Whereas those of water decreased greatly by??57% and??57% respectively in enriched CO₂. In contrast, gross nitrate (NO₃ ^?) consumption and nitrification rates of soil decreased by??11% and??14% and those of water increased by 29% and 27% respectively in enrichment CO₂. These may be due to the extremely high soil microbial biomass nitrogen (MBN), which increased by 94% in elevated soil. The results can show when CO₂ concentrations are going to rise in the future. Consequently soil microbial activity initiates the decreased N concentration in sediment and increased N concentration in overlying water in riparian wetland ecosystems.