火干扰对小兴安岭毛赤杨沼泽温室气体排放动态影响及其影响因素

Abstract

利用静态箱-气相色谱法,对小兴安岭轻度火烧毛赤杨沼泽CH₄、CO₂、N₂O生长季排放通量进行研究。结果表明:火烧使毛赤杨沼泽生长季CH₄排放通量提高485.2%,CO₂和N₂O排放通量分别下降45.5%、24.8%。火烧未改变CH₄季节性排放规律,但改变了CO₂、N₂O季节性变化规律。火烧样地CH₄排放通量与土壤15cm温度间存在显著正相关性关系而与水位相关性不显著,火烧样地CO₂排放与土壤0-30 cm温度呈显著或极显著正相关,与水位极显著负相关。对照样地CO₂排放通量与土壤0-15 cm温度呈显著或极显著正相关,与水位极显著负相关,火烧使毛赤杨沼泽CH₄排放源的强度增强,CO₂、N₂O的排放消弱,全球温室潜势下降约为43.34%。;Wetlands are important sources and sinks of greenhouse gases. Fire disturbance plays an important role in wetland ecosystems. it commonly is a important carbon sink of the land ecosystems, the Lesser xing'an Mountains of China's northeast is the frequent area of the fire disturbance as well as a major distribution area of China's wetlands. Fire-related disturbance in forests are more frequent in mid-to high latitudes than elsewhere. In the present study, <em>Alnus sibirica</em> wetland, were studied to reveal the emission variation of CH₄, CO₂, and N₂O under fire disturbance during the growing season. The study area is located in the Lesser Xing'an Mountains. We used a static opaque chamber and gas chromatography methods, and we monitored related environmental factors. The results were as follows: disturbance by fire increased air and soil temperature by 2.5-5.0℃, and lowered the water table by an average of 0.24-6.36 cm. Burning increased CH₄ emissions from <em>Alnus sibirica</em> wetlands by 485.2. Burning decreased the CO₂ and N₂O emissions by 45.5% and 24.8% respectively from <em>Alnus sibirica</em> wetland. Burning also changed the <em>Alnus sibirica</em> wetland CO₂ and N₂O flux patterns in the growing season, but no marked variations were detected in the <em>Alnus sibirica</em> wetland CH₄.<br> Burning changed the <em>Alnus sibirica</em> wetland green-house gas flux patterns in the growing season.The CH₄ emissions and the seasonal change pattern were affected by fire disturbance. Before and after the fire disturbance, CH₄ emission flux remained unchanged during the growing season. The CH₄ was absorbed weakly by the wetland soil(M₀,M₁) in spring and emitted in summer and autumn. The CH₄ emission flux in summer was less than that in autumn. the CO₂ and N₂O emission fluxes had changed. At the unburned site, the CO₂flux had a seasonal variation where summer flux > spring > autumn; under fire disturbance, the CO₂flux in summer > autumn> spring. The N₂O flux varied in the order of spring > autumn > summer under no fire disturbance, but under slight fire disturbance, the order was spring > summer >autumn. <br> The CH₄ flux from the reference marsh wetland plot (unburned) was significantly correlated (<em>P</em><0.05) with soil temperature at 15 cm-depth, but it was not correlated with water table depth in the burned plot. No significant correlations were found between CH₄ flux and soil temperature in any soil horizons, or with water table depth in the <em>Alnus sibirica</em> wetland. In the reference plots of <em>Alnus sibirica</em> wetland, the CO₂ flux had a significant positive correlation (p<0.05) with soil temperature at depths between 0-15 cm; at burned sites, the CO₂flux had a highly positive correlation with soil temperature in the 0-30 cm depth. Fire disturbance enhanced CH₄ emission intensity, and reduced the CO₂ and N₂O emissions. Under such circumstances, the global warming potential at burned sites would be decreased by 43.34%. Therefore, fire disturbance could decrease the emission of greenhouse gases from the <em>Alnus sibirica</em> of forested wetlands. Statistically significant negative correlation (<em>P</em><0.05) was found between CO₂ flux and water table depth within marsh, reference and burned plots of <em>Alnus sibirica</em> wetlands. Burning increased CH₄emission intensity, and reduced the CO₂ and N₂O emissions. The global warming potential at burned sites decreased by 43.34%. Therefore, fire disturbance could decrease the emission of greenhouse gases from the <em>Alnus sibirica</em> of forested wetlands.