模拟水位变化对杭州湾芦苇湿地夏季温室气体日通量的影响

水位是影响湿地温室气体排放的重要因子。采用静态箱-气相色谱法研究了模拟条件下不同水位(0、5、10 cm和20 cm)对芦苇湿地温室气体(CO_2、CH_4、N_2O)夏季昼夜通量变化的影响。结果表明,1)4种不同水位CO_2通量日变化均表现为昼低夜高,且白天为汇,夜间为源,整体均表现为CO_2的汇;不同水位CH_4通量日变化则均表现为昼高夜低,且整体上均表现为CH_4的源;N_2O通量总体上水淹后均表现为昼高夜低而0cm水位表现为昼低夜高;2)随着水位的增加CH_4和CO_2平均通量呈现先增加后降低的趋势,且10cm水位下CH_4和CO_2平均通量最高,N_2O通量则在5cm水位最高;3)通过相关性和主成分分析表明,气温、水温是土壤CH_4、N_2O通量日变化的主导因子,而土壤温度是CO_2日变化通量的主导因子,同时,土壤p H、Eh及水体p H、Eh是CO_2通量日变化的重要因子之一。

Effects of simulated water levels on diurnal variation in the emission of three greenhouse gases in reed wetlands in summer

Water level affects greenhouse gas fluxes in wetlands. A static chamber-gas chromatographic technique was used to study the release of three greenhouse gases, CO₂, CH₄, and N₂O at simulated water levels (0, 5, 10, and 20 cm) of reed wetlands in the Hangzhou Bay area. The results indicated that, 1) the CO₂ flux was higher at night and lower during the day-acting as sink during daytime and source at night-with a net flux as sink of CO₂ irrespective of water level. CH₄ was lower at night and higher during the day with a net flux as source of CO₂. N₂O flux was lower at night but higher during the day, except at 0 cm; 2) the CH₄ flux and the CO₂ flux increased, followed by a decrease, with increasing water level. The water levels for the highest average fluxes were 10 cm for CH₄ and 5 cm for CO₂; and 3) correlation and principal component analysis showed that water temperature was the dominant factor for the daily variation in soil CH₄ and N₂O flux, and soil temperature was the dominant factor for the daily variation in CO₂ flux. Meanwhile, soil pH, soil Eh, water pH, and water Eh were all important factors for the variation in CO₂ flux.