Fluxes And Controls Of CO₂, CH₄ And N₂O Emissions In The Typical Marsh And Swamp In Xiaoxing'an Mountains

The study was to evaluate the CO₂, CH₄tand N₂O budget, to understand seasonal and diurnal variations of CO₂, CH₄ and N₂O, and to explore effects of temperature and moisture on CO₂, CH₄ and N₂O fluxes in the Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp of Xiaoxing'an Mountains, in growing season(from June to October, 2007 and from May to October, 2008), using a static chamber and gas chromatograph technique.The results showed that emissions of CO₂ in 2007 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp were 17841.78 and 20130.56 kg·hm^-2, 16331.78 and 18294.24 kg·hm^-2 in 2008 respectively. Emissions of CH₄ in 2007 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp were 69.26 and 3.36 kg·hm^-2, 1482.60 and 18.15 kg·hm^-2 in 2008 respectively. Emissions of N₂O in 2007 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp were 0.14 and 0.29 kg·hm^-2, 0.68 and -0.10 kg·hm^-2 in 2008 respectively.CO₂, CH₄ and N₂O(except Betula ovalifolia-Carex schmidtii shrub swamp in 2008) fluxes showed conspicuous seasonal variations. The highest emissions of CO₂ were in summer; and CH₄ were in summer and fall from Carex schmidtii marsh and in 2008 from Betula ovalifolia-Carex schmidtii shrub swamp, in fall in 2007 from Betula ovalifolia-Carex schmidtii shrub swamp; and N₂O were in summer in 2007 from Carex schmidtii marsh and in 2008 from Betula ovalifolia-Carex schmidtii shrub swamp, in summer and fall in 2008 from Carex schmidtii marsh and in 2007 from Betula ovalifolia-Carex schmidtii shrub swamp.The seasonal average of CO₂ fluxes were 487.89 and 549.62 mg·m^-2·h^-1 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in 2007, and 391.53 and 438.31 mg·m^-2·h^-1 in 2008 which didn't display conspicuous inter-annual variations.Diurnal CO₂ fluxes in August were dominant, the fluxes in June took second place and the fluxes in September were the least from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp, which showed high in the daytime and low in the nighttime. Diurnal CO₂ fluxes were in the range of 408.44-616.65 and 469.92-942.21 mg·m^-2·h^-1 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in August, were 182.98-635.05 and 206.25-763.40 mg·m^-2·h^-1 in June, and were 102.95-318.77 and 15.19-285.01 mg·m^-2·h^-1 in September. The seasonal average of CH₄ fluxes were 1.88 and 0.092 mg·m^-2·h^-1 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in 2007, and 34.18 and 0.43 mg·m^-2·h^-1 in 2008 which displayed conspicuous inter-annual variations. Diurnal CH₄ fluxes show significant change from Carex schmidtii marsh, the diurnal fluxes in June and September showed high in the daytime and low in the nighttime, and in August showed high in the nighttime and low in the daytime. Diurnal CH₄ fluxes did not show significant change from Betula ovalifolia-Carex schmidtii shrub swamp. Diurnal CH₄ fluxes were in the range of 0.68-1.89 and -0.07-0.21 mg·m^-2·h^-1 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in August, were 2.20-4.67 and 0.08-0.21 mg·m^-2·h^-1 in June, and were1.82-10.89 and -0.02-0.19 mg·m^-2·h^-1 in September.The seasonal average of N₂O fluxes were 0.0037 and 0.0082 mg·m^-2·h^-1 from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in 2007, and 0.016 and -0.0025 mg·m^-2·h^-1 in 2008. Inter-annual variations of N₂O fluxes from Betula ovalifolia-Carex schmidtii shrub swamp displayed conspicuous, but Carex schmidtii marsh didn't. The Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp were source of N₂O in Augus and September, but were feeble sink of N₂O in June.Diurnal N₂O fluxes showed high in the daytime and low in the nighttime in August, in June and September did not show significant change from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp, which were in the range of-0.008-0.03 and 0.002-0.017 mg·m^-2·h^-1 in August, were-0.014-0.002 and -0.015-0.005 mg·m^-2·h^-1 in June, and were-0.005-0.008 and -0.003-0.021 mg·m^-2·h^-1 in September.There was a significantly positive relationship between CH₄ and CO₂, and CO₂ was found a significantly positive with N₂O. There was a significantly positive or negative relationship between CH₄ and N₂O.From the Carex schmidtii marsh, diurnal variations of CO₂ fluxes were linearly correlated significantly with temperature (air temperature, temperature of inside the chamber, soil temperature of 0 and 30 cm ), and CH₄ fluxes were dualistic linearly correlated significantly with temperature (air temperature, temperature of inside the chamber) in September. Diurnal variations of CO₂ fluxes were linearly correlated significantly with temperature (air temperature, soil temperature of 15cm ) in June, and N₂O fluxes were negative correlated significantly with soil temperature of 10 cm. Diurnal variations of N₂O fluxes were positive correlated significantly with soil temperature of 0 cm in August. From the Betula ovalifolia-Carex schmidtii shrub swamp, diurnal variations of CO₂ fluxes were linearly correlated significantly with temperature (air temperature, temperature of inside the chamber), and N₂O fluxes were linearly correlated significantly with soil temperature of 40cm in August. In September, diurnal variations of CO₂ fluxes were linearly correlated significantly with temperature (air temperature, temperature of inside the chamber, soil temperature of 0 cm ) and were logarithmic correlated significantly with soil temperature of 10 and 15 cm, and N₂O fluxes were negative correlated significantly with soil temperature of 10 and 15 cm. In June, N₂O fluxes were negative correlated significantly with soil temperature of 15 cm. CH₄ fluxes were not correlated significantly with temperature.CO₂ emissions from marsh wetlands were controlled by various temperature. CO₂ fluxes were linearly positive correlated significantly with soil temperature of 0, 5, 10,15 cm, were logarithmic correlated significantly with soil temperature of 20 cm, and CH₄ fluxes were positive correlated significantly with soil temperature of 5, 10,15, 20, 30, 40 cm, and N₂O fluxes were negative correlated significantly with soil temperature of 10cm from the Carex schmidtii marsh; CO₂ fluxes were linearly positive correlated significantly with temperature (air temperature, soil temperature of 0, 5 cm), were logarithmic correlated significantly with soil temperature of 10, 15, 20 cm, and CH₄ fluxes were not correlated significantly with temperature, and N₂O fluxes were negative correlated significantly with the water level from the Betula ovalifolia-Carex schmidtii shrub swamp(n=32).