Abstract: Static chamber/gas chromatogram method was adopted to measure the methane emission flux of Zhalong Phragmites australis wetlands with different water levels in a growth season from May to October, 2009, aimed to understand the methane emission pattern in natural freshwater P. australis wetland in frigid region. During the observation period, the average methane emission flux of test wetlands ranged from -21.18 to 46.15 mg·m^-2·h^-1, with a mean of 7.67mg·m^-2·h^-1. In deep water zone (average water level 100 cm) and shallow water zone (average water level 25 cm), the average methane emission flux was 5.81 and 9.52mg·m^-2·h^-1, with a peak in August and July, respectively, and the minimum in October. In summer (from June to July), the methane emission flux in deep water zone was significantly lower than that in shallow water zone; while in spring (May) and autumn (from August to October), a reversed trend was observed. The methane emission flux had a seasonal pattern of summer > autumn > spring, and a diurnal pattern of being the highest at 12:00 and 14:00 and the lowest at 0:00. Temperature and water level were the major factors affecting the methane emission flux in freshwater P. australis wetlands in frigid region.

Key words: methane, emission flux, Phragmites australis, Zhalong wetland