EFFECTS OF WATER TABLE AND NITROGEN ADDITION ON CO₂ EMISSION FROM WETLAND SOIL

Key words: 
• CO₂ emission /
• water table /
• nitrogen addition /
• wetland soil

Abstract: Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes. Water table and nutritious availability are significant impact factors to influence responses of CO₂ emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen status have been incubated to measure rates of CO₂ emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3 nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO₂ emissions were found at a static low water table (Ⅰ) and a fluctuant water table (Ⅳ), averaging 306.7mg/(m²·h) and 307.89mg/(m²·h), respectively, which were 51%-57% higher than that at static high water table (Ⅱ and Ⅲ). After nitrogen addition, however, highest CO₂ emission was found at Ⅱ and lowest emission at Ⅲ. The results suggested that nutritious availability of wetland soil might be important to influence the effect of water table on the CO₂ emission from the wetland soil. Nitrogen addition led to enhancing CO₂ emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious treatments, low CO₂ emissions at high water tables and high CO₂ emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table changes and nutritious imports would effect the CO₂ emission from wetland.