Studies On CO₂ And CH₄ Fluxes From Zhalong Wetlands

Fluxes of CO₂ and CH₄ from Zhalong wetland were measured by static chamber/gas chromatogram method from 2008 to 2009 in order to study spatiotemporal patterns and influencing factors in Zhalong wetland. The results showed that(1) Average CO₂ and CH₄ fluxes across water-air interface from Zhalong waters were 45.91 mg.m^-2.h^-1 and 4.78 mg.m^-2.h^-1, respectively. Zhalong waters released 4.5×104 ton CO₂ and 5.3×103 ton CH₄ annual, as sources of CO₂ and CH₄.(2) There were spatiotemporal differences on CO₂ flux from Zhalong lakes. CO₂ flux of 2008 was lower than that of 2009. CO₂ flux in summer was lower than in spring and autumn. CO₂ flux at night was lower than that at day from Long Lake in spring (April and May), on the contrary, CO₂ flux at night was higher than that at day in summer and autumn (from June to September). In spite of significant differences of CO₂ flux between various waters were not observed, spatiotemporal differences of CO₂ flux were observed in some months. Temperature, biomass of aquatic plant and organic carbon were major forcing factors.(3) There were spatiotemporal differences on CH₄ flux from Zhalong lakes. CH₄ flux of 2008 was lower than that of 2009. The CH₄ release peak was observed in summer in 2008, and the highest CH₄ emission was measured in spring melting period in 2009. Diural pattern of CH₄ flux from Long Lake was not found, and CH₄ released in whole day with several emission peak. The order of CH₄ emission was Keqin Lake4 flux from deep and shallow reed wetland were 5.74 mg.m^-2.h^-1 and 8.84 mg.m^-2.h^-1, respectively. Zhalong reed wetland released 3.88×105 ton CH₄, ie 2.91×105 ton C.(5) Seasonal and durial differences of CH₄ flux were observed in Zhalong reed wetland. The CH₄ emission peak occurred in summer from reed wetland, the highest CH₄ flux 10.30±6.91 mg.m^-2.h^-1 from deep reed wetland (average water level was 99.5 cm) was observed in October, and the highest CH₄ flux 19.97±11.38 mg.m^-2.h^-1 from shallow reed wetland (average water level was 25 cm) was observed in July. CH₄ fluxes in spring and autumn were lower than in summer. CH₄ emisson peak was observed in noon (12:00 and 14:00) and the lowest flux was observed in midnight (0:00) and early morning (4:00). Temperature, water level and biomass of reed were major influence factors.(6) Artificial recharge may stimulate CH₄ emission from reed wetland. Campared the controlled group, CH₄ flux of higher water level (RH) reed wetland increased 3.66 mg·m-1·h-1 due to increasing water level;CH₄ flux of lower water level (RA) reed wetland increased 15.39 mg·m-1·h-1 due to flooded. Water level change was the major reason of increasing methane emission from reed wetland. Carbon sink function and carbon sequestoration potential and the responces of CH4 flux to artificial recharge in Zhalong wetland were studied in this experiment. The data may be applicated to evaluate carbon source/sink function in boreal fresh wetland, and provided scientific evidence to study methane emission characteristic from wetland during ecological restoration.