Abstract: By the methods of static chamber and gas chromatography, this paper studied the effects of fire disturbance on the seasonal dynamics and source/sink functions of CH₄, CO₂ and N₂O emissions from Betula platyphylla-forested wetland as well as their relations with environmental factors in Xiaoxing’an Mountains of China. In growth season, slight fire disturbance on the wetland induced an increase of air temperature and ground surface temperature by 1.8-3.9 ℃ and a decrease of water table by 6.3 cm; while heavy fire disturbance led to an increase of air temperature and 0-40 cm soil temperature by 1.4-3.8 ℃ and a decrease of water table by 33.9 cm. Under slight or no fire disturbance, the CH₄ was absorbed by the wetland soil in spring but emitted in summer and autumn; under heavy fire disturbance, the CH₄ was absorbed in spring and summer but emitted in autumn. The CO₂ flux had a seasonal variation of summer > spring = autumn under no fire disturbance, but of summer > autumn > spring under fire disturbance; and the N₂O flux varied in the order of spring > summer > autumn under no fire disturbance, but of autumn > spring > summer under slight fire disturbance, and of summer > spring = autumn under heavy fire disturbance. At unburned site, the CO₂ flux was significantly positively correlated with air temperature and ground surface temperature; at slightly burned site, the CO₂ flux had significant positive correlations with air temperature, 5-10 cm soil temperature, and water table; at heavily burned sites, there was a significant positive correlation between CO₂ flux and 5-40 cm soil temperature. Fire disturbance made the CH₄ emission increased by 1695% at lightly burned site or turned into weak CH₄ sink at heavily burned site, and made the CO₂ and N₂O emissions and the global warming potential (GWP) at burned sites decreased by 21.2%-34.7%, 65.6%-95.8%, and 22.9%-36.6% respectively,compared with those at unburned site. Therefore, fire disturbance could decrease the greenhouse gases emission from Betula platyphylla-forested wetland, and planned firing could be properly implemented in wetland management.

Key words: Xiaoxing’an Mountains, Betula platyphylla swamp, greanhouse gas emission, fire disturbance