Effects Of Fire Disturbance On Greenhouse Gas Emissions From Marsh, Shrub Swamp, Broadleaved Forested Swamp In Xiaoxing'an Mountains

Wetlands are important sources and sinks of greenhouse gases, the forestry of fire disturbance were 1% per year on average in the global, especially fire disturbance of forestry are more frequent in mid-high latitude, fire was an important disturbance factor for forest wetlands. In the present study, the four kinds of forest wetlands (Carex schmidtii wetland, Betula ovalifolia-Carex schmidtii shrubs wetlands, Alnus sibirica wetlands, Betula platyphylla wetlands) were studied to reveal the emission variation of CH4, CO2 and N2O under fire disturbance of forest wetlands in the growing season by using a static opaque chamber and gas chromatography method. The results as follow:The air, soil temperature and water level were significant affected by fire disturbance in varieties forest wetlands of growing season. Compared with control sites the temperature were increased for the air and all layers soil of Alnus sibirica burned sites and Betula platyphylla heavily burned sites, the air and 0-10 cm layers soil of hassock and shrubs burned sites, the air and surface soil of Betula platyphylla lightly burned sites. Fire disturbance made the water level drop, and water level was lower in heavily Betula platyphylla burned sites than lightly.The CH4 emission and the seasonal change pattern were affected by fire disturbance. Besides Betula platyphylla heavily burned sites, the seasonal change patterns of CH4 fluxes were the same in all varieties site, the site all absorbed CH4 in spring and emitted CH4 in summer and autumn, and emission fluxes was more in autumn than in summer. The CH4 fluxes changed from weak emitted to absorbed by influence of heavy fire disturbance in Betula platyphylla wetlands, and the seasonal change pattern also changed to weak absorb in spring and summer and weak emit in autumn. The fire disturbance can change CO2 emission fluxes in seasonal change pattern of soil, the CO2 emission fluxes took on summer> spring= autumn at unburned site, but it took on summer> autumn> spring at burned sites. The seasonal change pattern of N2O emission did not significantly same in unburned and burned site for all type of wetlands, the fluxes was low and largely change.The correlation between the effect of fire disturbance of the CH4 emitted in Betula platyphylla wetlands of growing season and environment factors was found to be weak. Only the temperature of individual layer significant correlated with the CO2 emission fluxes of control hassock wetland site, Alnus sibirica wetlands, Betula platyphylla lightly burned site (P<0.05). The Primary influence Factors of CO2 emission were soil temperature and water table of underground, the correlation become close between CO2 emission fluxes and soil temperature by the influence of fire disturbance. The correlation between the effect of fire disturbance of the N2O emitted and environment factors was found to be weak. Only the temperature of individual layer significant correlated with N2O emission fluxes of shrubs wetland burned site and Betula platyphylla control wetlands site(P<0.05). The water table of wetlands did not significant correlated with the emission of CH4 and N2O, but significant negative correlated with CO2 emission.The CH4 emission of fire disturbance were affect by intensity of fire. Fire disturbance made source of CH4 emission turn into poor sink of CH4 at heavily burned site, after fire burned the CH4 emission increased at the other type of wetlands and Betula platyphylla lightly burned site. The emission fluxes of N2O and soil CO2 decreased with fire disturbance in all type of wetlands in growing season, and the effect of heavy fire disturbance was stronger than light burned at Betula platyphylla lightly burned site.After fire disturbance the Global Warming Potential (GWP) of shrubs wetlands increased by 33.9%, greenhouse gases of Global Warming Potential (GWP) decreased by 12.7%～38.1% at other type wetlands, and the dimin effect of light fire disturbance was weaker than heavy burned at Betula platyphylla wetlands. Accordingly, planning fire should be taken in forest wetlands management from the greenhouse gases controlling point of view.