Study On Methane Emission From Alpine Peat Wetland,Zoige Plateau

Methane(CH4) is the second important greenhouse gas after carbon dioxide, which have 28 times global warming potential(GWP) of CO2 on the scale of one hundred years. More attention should be paid to the acknowledgement of its source and sink. Alpine peat wetlands are important sources of atmosphere methane. Most of available in situ measurements were exclusively done in growing seasons because of very weathers in non-growing seasons. Due to this situation, CH4 emission from seasonal-freezing alpine peat wetlands in non-growing season so far has not been well known. This study aimed at investigation of the CH4 emission characteristics and its importance in the non-growing season by carrying out 9-mouth field measurements(from almost entire winter through early summer) in a Zoige alpine wetlands with seasonal-freezing peat. The field site was located at the northeast edge of the Qinghai-Tibetan Plateau. Methane fluxes were manually measured weekly or half-weekly at 9:00~11:00 in the morning at 6 random locations, with typical bulge(BA), hollow(HA) and transition(TA) areas for each, using static opaque chambers to collect gas samples and a gas chromatograph for immediate sample analysis.The CH4 fluxes during the whole observation period, mean methane emissions rate, among 6 spatial redundancies, ranged from 0.1 to 1.0 mg C m-2 h-1 showing significant emission in the non-growing season. The temperature sensitivity(Q10, which is the folds of changes in CH4 fluxes due to a temperature change of 10oC) during the non-growing period(18.1~29.8) was much higher than that during the growing season(1.4~2.2), implicating that the methane emission in non-growing seasons could be much more sensitive to climate warming. By simply extrapolating our measured fluxes, combined with results of other observations in growing season, the annual CH4 emission from the investigated alpine wetland was estimated at about 30 kg C ha-1 yr-1, of which at least 50% was released in the non-growing season. The CH4 fluxes during the observation period showed significant seasonal variation, which may be attributed jointly to temperature variation, freezing-thawing alternation, water table(or soil moisture) dynamics and seasonality of plant growth. The CH4 fluxes were also significantly different among the micro-landforms, with statistically the lowest, highest and moderate values at the BA, TA and HA, respectively(p < 0.01). The BA, TA and HA approximately accounted for 22%, 43% and 35% of the bulk CH4 emission from the whole wetland. Such spatial variability may be attributed to the spatial variations in environment factors such as water table(or soil moisture), plant distribution and soil organic matter content.However, the above results and conclusions derived from our field measurements during a relatively short period still need further confirmation with long-term field observations lasting for years or even longer.