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采用室内土柱培养的方法,研究不同湿润程度(55%和80%WFPS)条件下外源碳(葡萄糖,6.4 g C m·2)和两种形态氮(NH4Cl和KNO3,4.5 g N m-2)的添加对温带成熟阔叶红松混交林和次生白桦林土壤氧化亚氮(N2O)排放量的影响.研究结果表明:除了高湿润程度单施NH4Cl的白桦林土壤外,湿润程度增加以及外源碳和氮添加均能显著促进两种林分土壤N2O排放量,并存在两两交互作用.葡萄糖添加使阔叶红松混交林和白桦林土壤在整个培养期内N2O累积排放量分别增加0.53~2.67和4.70~29.32 mg N2O-N m-2,尤其是高湿润程度和白桦林土壤更为明显;同时伴有葡萄糖添加后两种林分土壤矿质氮含量显著减少,特别是高湿润条件下白桦林土壤水浸提NO3-含量降低幅度更大.这说明了白桦林土壤N2O释放量对外源碳添加的激发效应更敏感,并随土壤湿度增加而加剧.低湿润条件下,培养初期外源氮添加显著抑制葡萄糖对土壤N2O排放量的促进作用,之后随着氮形态和林分类型而发生变化;高湿润条件下,外源氮添加显著增强葡萄糖对土壤N2O排放量的促进作用,且硝态氮强于铵态氮(P<0.05).葡萄糖添加能增加两种林分土壤微生物碳含量和微生物碳/氮比(P<0.05),显示可能改变土壤微生物群落结构.两种形态氮的添加均能增加两种林分土壤水和K2SO4浸提的溶解性有机氮(DON)含量,尤其是阔叶红松混交林土壤(P<0.05),但两种形态氮之间无差异.多元线性逐步回归分析显示,实验条件下白桦林土壤N2O累积排放量受到WFPS、水浸提NH4+-N和水浸提DON含量及微生物碳/氮比的影响,共同解释其61%的变化,其中水浸提DON含量贡献率最大;阔叶红松混交林土壤N2O累积排放量受到WFPS、水浸提NH4+-N和微生物碳含量的影响,共同解释其50%的变化,其中水浸提NH4+-N含量贡献率最大.上述结果显示,加湿对森林土壤N2O排放量的增加与土壤活性氮含量、湿润程度和微生物量有关.
Indoor soil column culture was used to study the effects of exogenous carbon (glucose, 6.4 g C m · 2) and two forms of nitrogen (NH4Cl and KNO3, 4.5 g N m-2) under different wetting degrees (55% and 80% 2) on N2O emission in mature broad-leaved-Korean pine mixed forest and secondary birch forest were studied.The results showed that except for the high wettability, the degree of wetting increased with the addition of NH4Cl to the birch soil, Both N sources and N sources increased soil N2O emissions significantly, and there was a two-to-one interaction between them.The cumulative N2O emissions of broadleaved-Korean pine mixed forest and birch forest increased by 0.53-2.67 And 4.70 ~ 29.32 mg N2O-N m-2, especially the degree of high wettability and birch soil more obvious; with the addition of glucose, the soil mineral nitrogen content of the two stands significantly decreased, especially under high wet conditions birch The soil NO3- content in soil water decreased more significantly, which indicated that the N2O emission in the soil of birch was more sensitive to the exogenous carbon addition and aggravated with the increase of soil moisture.Under the conditions of low humidity, Significantly inhibited glucose pairs Soil N2O emission, and then changed with the nitrogen forms and the types of forest types. Under the conditions of high humidity, the addition of exogenous nitrogen significantly enhanced the promoting effect of glucose on soil N2O emissions, and the nitrate nitrogen was stronger than ammonium Nitrogen (P <0.05) .In addition, glucose addition could increase soil microbial biomass carbon and soil microbial C / N ratio (P <0.05), suggesting that soil microbial community structure may be changed.The addition of two forms of nitrogen increased both The contents of soluble organic nitrogen (DON) extracted from soil water and K2SO4, especially in the mixed Korean pine broad-leaved mixed forest soil (P <0.05), but there was no difference between the two forms of nitrogen.Multiple linear stepwise regression analysis showed that the experimental conditions The cumulative emissions of N2O from the lower birch soils was affected by WFPS, NH4 + -N extracted by water leaching, DON content and microbial C / N ratio, and 61% of them were changed. The content of DON contributed by water extraction was the largest. The emission of N2O in the soil of mixed Korean pine and broad-leaved mixed forests was affected by WFPS, NH4 + -N and microbial carbon content, and explained 50% of the changes. The contribution of NH4 + -N content in water- N2O emissions from forest soils Active nitrogen content plus soil, and the wetness of the relevant microbial biomass.