• 关键词：秦岭  油松林  坡位  土壤温室气体通量

• 基金项目：国家自然科学基金（No.41101182）；西北农林科技大学基本科研业务费（No.Z109021106）；西北农林科技大学博士科研启动基金项目（No.Z109021102）

• 扆凡
• 西北农林科技大学林学院, 杨凌 712100

• 庞军柱
• 1. 西北农林科技大学林学院, 杨凌 712100;2. 陕西秦岭森林生态系统国家野外科学观测研究站, 安康 711600;3. 西北农林科技大学林学院生态预测与全球变化实验室, 杨凌 712100

• 刘岳坤
• 西北农林科技大学林学院, 杨凌 712100

• 彭长辉
• 1. 西北农林科技大学林学院, 杨凌 712100;2. 西北农林科技大学林学院生态预测与全球变化实验室, 杨凌 712100

• 张硕新
• 1. 西北农林科技大学林学院, 杨凌 712100;2. 陕西秦岭森林生态系统国家野外科学观测研究站, 安康 711600

• 侯琳
• 1. 西北农林科技大学林学院, 杨凌 712100;2. 陕西秦岭森林生态系统国家野外科学观测研究站, 安康 711600

• 王效科
• 中国科学院生态环境研究中心, 北京 100085

• 张红星
• 中国科学院生态环境研究中心, 北京 100085

• 摘要：在秦岭南坡火地塘林区天然次生油松林内选取上、中、下3个坡位，采用静态箱-气相色谱法对土壤CO₂、CH₄、N₂O通量进行了1年的监测.结果表明，坡位间土壤质地和水分的差别是引起不同坡位CO₂与N₂O通量差异的主要原因：下坡位土质为壤土，水分适宜，CO₂平均排放量为（156.49±9.72） mg·m^-2·h^-1，CH₄平均吸收量为（77.43±14.27） μg·m^-2·h^-1，都处于3个坡位间最高水平；中坡位土质为粉砂壤土，土壤粒径小，透气性差，CO₂排放量和CH₄吸收量均为3个坡位间的最小值，N₂O平均排放量为（9.57±0.66） μg·m^-2·h^-1，为3个坡位间的最高值，且显著高于上坡位土壤N₂O通量（p<0.01）；上坡位土质为砂壤土，土壤孔隙度大且地表植被少，N₂O平均排放量为（5.59±0.74） μg·m^-2·h^-1，为3个坡位间的最小值.总体来说，油松林土壤是CO₂、N₂O的排放源，是CH₄的吸收汇.3个坡位CO₂年通量具有明显的季节规律，表现为倒"S"形变化，且与土壤温度显著正相关（p<0.01）.受冻融循环的影响，N₂O主要在非生长季大量排放；生长季末期，受降雨事件影响，油松林中坡位出现N₂O吸收峰值.生长季上、下坡位CH₄吸收峰值的出现同样伴随着降雨事件的发生，非生长季，中坡位因土壤水分过高而出现短暂的CH₄排放现象.不同坡位土壤温室气体的全球增温潜势（Global Warming Potential，GWP）从大到小依次是上坡位、下坡位和中坡位.

• Abstract：Soil-atmosphere exchanges of CO₂, CH₄ and N₂O along a slope (lower, middle and upper slope positions) of natural secondary Pinus tablaeformis forest in Huoditang Area on the southern slope of Qinling Mountains were monitored over a whole year. The fluxes of those greenhouse gases were measured using static chamber and gas chromatography techniques. The differences in the amounts and patterns of CO₂ and N₂O were attributed to the variations in soil texture and water filled pore space (WFPS) along the slope positions. Soil texture of the lower slope position was loam, so soil organisms could subsist in surface soil due to its suitable moisture conditions. The mean values of soil CO₂ fluxes and CH₄ fluxes at the lower slope position were (156.49±9.72) mg·m^-2·h^-1 and (77.43±14.27) μg·m^-2·h^-1, respectively. Those two fluxes values of the lower slope position were higher than those of the other two slope positions. Soil texture of the middle slope position was silt loam with the minimum soil particle diameter, which led to the mean values of soil CO₂ fluxes and CH₄ fluxes being lower than the other two slope positions. Among slope positions, the avergage N₂O emission rate was the highest in the middle slope position with the value of (9.57±0.66) μg·m^-2·h^-1. Soil N₂O fluxes of the middle slope was significantly higher than that of upper slope (p<0.01). In the upper slope position, soil texture was sandy loam, which led to the largest soil porosity and the lowest vegetation coverage among the three slope positions. The mean values of N₂O emission at the upper slope position was merely (5.59±0.74) μg·m^-2·h^-1 and was lower than the other two slope positions. In general, Pinus tablaeformis forest soil acted as sources for CO₂ and N₂O, but served as sink for CH₄. The CO₂ emissions demonstrated clear seasonal pattern and was significantly positively correlated with soil temperature (p<0.01). In comparison, N₂O emissions mainly occurred in non-growing season due to the effects of freezing and thawing. At the end of the growing season, there was a consumption peak of N₂O at the middle slope position, which may be due to rainfall event. During the growing season, the presence of CH₄ consumption peak occurred concurrently with rainfall events both in lower and upper slope positions. However, occasional periodic of CH₄ emissions at the middle slope position was also observed during non-growing season, which might due to the high soil moisture content. The values of global warming potential at different slope positions were the highest at the upper slope position, the lowest at the middle slope position, and intermediate at the lower slope position.

• Key words：Qinling Mountains  Pinus tablaeformis forest  slope positions  greenhouse gases fluxes

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