大气氮沉降正在显著影响着森林生态系统的土壤碳循环过程.目前关于大气氮沉降如何影响土壤不同粒级团聚体内活性有机碳含量还不是十分清楚,制约人们对森林土壤碳循环的认识和有关碳循环模型的发展.通过近2年的林地梯度氮添加(0、3、6、9 g N m-2 a-1)实验,研究了短期氮添加对人工油松林表层土壤团聚体中不同活性有机碳含量的影响.结果表明:短期氮添加对表层土壤(0-10 cm)水稳性团聚体分布无显著影响;随着氮添加水平增加,大、微团聚体有机碳含量,大、微团聚体中活性和高活性有机碳含量呈先升高后降低的变化规律,并在N6处理(6gNm-2a-1)下上述各指标达到最大;同一处理下土壤大、微团聚体活性有机碳含量都表现为高活性有机碳＞中活性有机碳＞低活性有机碳;相比CK处理,N6处理大团聚体低、中、高活性有机碳含量分别增加115.06％、178.73％和79.61％,微团聚体低、中、高活性有机碳含量增加32.84％、166.79％和62.05％.大、微团聚体中活性有机碳含量增幅最大,表明团聚体中活性有机碳对氮添加响应最为明显.研究发现,短期氮添加主要通过影响表层大、微团聚体中的中活性有机碳进而影响土壤表层有机碳含量.主成分分析表明,N添加改变了土壤理化性质,进而导致根系生物量增加并促进凋落物分解,是表层土壤团聚体活性有机碳变化的主要原因.%Increasing nitrogen (N) deposition is significantly affecting the carbon cycle in forest ecosystems.However,it is not clear how N deposition affects the content of labile organic carbon in soil aggregates,which restricts our understanding of the soil carbon cycle and the development of the carbon cycle model.This study was conducted in an artificial Pinus tabulaeformis forest and simulated N deposition for nearly 2 years.Three N treatments,namely,N3 (3 g N m-2 a-1),N6 (6 g N m-2 a-1),and N9 (9 g N m-2 a-1),and a control treatment with no N added were applied,and each was replicated six times.Three labile organic carbon in soil aggregates were measured.There was no significant effect of short-term N addition on surface soil aggregates,while soil organic carbon was dramatically affected by N addition.Soil organic carbon content in the 0-10 cm soil layer was higher in the three N addition treatments and was highest in the N6 treatment.Additionally,the change in organic carbon content in macro-and micro-aggregates generally followed the pattern of soil organic carbon,and moderately,highly labile organic carbon also followed.In soil aggregates,the amount of highly labile carbon was greatest,then moderately labile carbon,and the content of minimally labile carbon was lowest.Compared to three labile organic carbon of CK treatment,the amount of minimally,moderately,and highly labile organic carbon in the N6 treatment increased by 115.06％,178.73％,and 79.61％ in macro-aggregate,respectively.And the amount of three labile organic carbons in the micro-aggregate increased by 32.84％,166.79％,and 62.05％,respectively.Among the three labile organic carbon categories,the change of moderately active organic carbon in the macro-and micro-aggregates was highest,which indicated that the moderately active organic carbon in soil aggregates was the most sensitive to short-term N addition.The results showed that short-term N addition affected surface soil organic carbon content by changing the amount of moderately labile organic carbon in the surface soil macro-and micro-aggregates.The results of a principal components analysis showed that soil total N and pH were affected by short-term N addition and it also caused a change in soil texture and total P.The changes of soil physical and chemical properties may result in an increase in root biomass and litter decomposition which brought a significantly change on active organic carbon content in surface soil aggregates.
展开▼
