Abstract:

The seasonal variation and the influence factors of emission fluxes of greenhouse gas (CO₂, N₂O and CH₄) from the soil ofLarix gmelinii-Betula ovalifolia-Carex schmidtii swamp, Larix gmelinii-Betula ovalifolia-Vaccinium uliginosum-moss swamp and Larix gmelinii-Ledum palustre var. anjustum-Sphagnum magellanicum swamp were studied during the growing season by static opaque chamber-GC technique in Xiaoxing′an Mountains of China. The results showed that: 1）The patterns of seasonal variation of emission fluxes of CO₂ from the soil of the three forested swamp communities all were a single-peak curve, high in summer(651.4～823.6 mg·m^-2h^-1), lower in spring and autumn(233.3～310.0 mg·m^-2h^-1); That of Emission fluxes of N₂O from the three communities respectively were 0.010～0.049, 0.012～0.020 and 0.010～0.080 mg·m^-2h^-1, and their seasonal changes were in a order of summer ＞spring＞autumn, spring＞summer＞autumn, and autumn＞spring＞summer respectively; Emission fluxes of CH₄ from the three communities were -0.083～0.037,-0.122～0.078 and-0.05～0.026 mg·m^-2h^-1, that was the soil emitted CH₄in spring and autumn, absorbing CH₄ in summer; emitted CH₄ in spring, absorbed CH₄ in summer and autumn, and emitted CH₄ in spring and summer, absorbed CH₄ in autumn respectively in the three communities. 2）In the three communities, temperature of the soil (＜30 cm ) was the main affecting factors of CO₂emission; Higher temperature of the soil (＜30 cm ) and lower water table were the main affecting factors of N₂O emission; Water table was the main affecting factors of CH₄ emission; The soil with lower water table emitted CH₄, while the soil with higher water table absorbed CH₄. 3）During the growing season, the soils of the three forested swamps all were the sources of CO₂(20.8～25.2 t·hm^-2), higher in summer, and lower in spring and autumn; The soils all were the sources of N₂O (0.192～1.128 kg·hm^-2). The soil ofLarix gmelinii-Betula ovalifolia-Carex schmidtii swamp emitted more N₂O than the other two. The soils of Larix gmelinii-Betula ovalifolia-Carex schmidtii swamp and Larix gmelinii-Betula ovalifolia-Vaccinium uliginosum-moss swamps both were strong sinks of CH₄ (1.152～1.200 kg·hm^-2), but the soils of Larix gmelinii-Ledum palustre var. anjustum-Sphagnum magellanicum swamp were a weak sources of CH₄ (0.168 kg·hm^-2). 4） The emission of greenhouse gases from the soil of Larix gmelinii-Betula ovalifolia-Carex schmidtii swamp was higher (CO₂:25.4 t·hm^-2) than others (CO₂： 20.8～21.2 t·hm^-2). The greenhouse gas all were composed of CO₂ mainly (99.63%～99.93%), few N₂O and CH₄ (0.19%～0.92% and 0.02%～0.10%).

Key words: forested swamps, greenhouse gas emission, seasonal variation, Xiaoxing&rsquo, an Mountains