氮可利用性对东北不同类型湿地土壤有机碳矿化的影响

2010年6~10月,在中国东北连续多年冻土区,岛状多年冻土区和季节性冻土区采集典型湿地土壤,通过室内分析和模拟试验研究了不同冻土区湿地土壤有机碳矿化及其微生物活性对不同氮可利用性的响应特征。试验设置4个氮处理水平,分别为0 mg/g(N0),0.1 mg/g(N1),0.2 mg/g(N2),0.5 mg/g(N3)。结果表明,培养结束后3种土壤在N0处理下的有机碳累计矿化量分别为5 646 mg/kg,2 103 mg/kg和1 287 mg/kg,与初始土壤有机碳含量、全氮含量和微生物量碳(MBC)呈显著正相关。3种土壤在氮输入后的有机碳矿化速率和累积矿化量都明显低于N0处理,表明氮输入对有机碳矿化产生抑制作用。随着氮输入量的增大,氮输入对不同土壤有机碳矿化的抑制作用有所差异,表现为:不同氮输入对连续多年冻土区土壤累积矿化量影响无显著差异;岛状多年冻土区土壤在N1和N2处理下的有机碳累积矿化量明显高于N3处理;季节性冻土区土壤在N2和N3处理下的累积矿化量明显低于N1处理。培养结束后,3种土壤微生物量氮(MBN)含量随氮输入量增加而降低,MBC/MBN随氮输入量增加而增加;季节性冻土区草甸沼泽土培养结束后的MBN和MBC/MBN都与累积矿化量存在显著相关关系,表明季节性冻土区草甸沼泽土氮可利用性增加可能改变了微生物的组成或结构,进而对有机碳矿化产生影响。

Effects of Exogenous Nitrogen Availability on Carbon Mineralization of Different Wetland Soil Types in Northeast China

To examine carbon(C) mineralization and microbial activities of different soil types under different levels of exogenous nitrogen(N) availabilities,three types of soil were collected from continuous permafrost,island permafrost and seasonally frozen ground,and incubated under laboratory conditions from June to October in 2010.The experiment was designed with four N levels,the amounts of exogenous N were 0(N0),0.1 mg/g(N1),0.2 mg/g(N2),0.5 mg/g(N3).The results indicated that the cumulative C mineralization of three types of soil under N0 treatment was 5 646 mg/kg,2 103 mg/kg and 1 287 mg/kg,respectively,which existed positive correlation with initial amount of soil organic C,total N and microbial carbon(MBC) in the end of incubation.The C mineralization rates and amount of cumulative mineralization of three types of soil under N0 treatment were all higher than under N treatment,indicated that exogenous N suppressed soil C mineralization.As the amount of exogenous N increasing,the inhibition of N on cumulative mineralization of different soil types was various.There was no significant difference of cumulative C mineralization of permafrost soil among three N treatments;the cumulative mineralization of island permafrost between N1 and N2 treatment was similar,but was all higher than N3 treatment;the difference of cumulative mineralization of seasonally frozen ground between N2 and N3 treatment was not notable,but was all lower than N1 treatment.After incubation,the values of MBN decreased and MBC/MBN increased along with exogenous N increasing.The cumulate mineralization of seasonal frozen soil positively related with MBN,and negatively related with MBC/MBN,which indicated that nitrogen availability may affect the carbon mineralization by changing microbial structure and composition.