春季解冻期3种温带森林土壤氮素动态变化

Dynamics of Soil Nitrogen in Three Temperate Forests During Spring Thawing

为了研究春季土壤冻融过程对氮素周转的影响,以长白山地区3种森林土壤为研究对象,利用原位培养连续取样法,测定和分析了不同形态氮素(NH_4^+-N、NO_3^--N和微生物量氮(MN))在春季解冻期间的含量动态变化。结果表明:土壤解冻过程中,3种森林土壤微生物量氮时间变化动态不同,且土壤微生物量氮表现出明显的垂直空间异质性,0~10 cm层土壤微生物量氮显著高于10~20 cm层。解冻期3种林型土壤NH_4^+-N时间变化动态表现一致,最大土壤NH_4^+-N释放量出现于解冻中后期。解冻期3种林型0~10 cm土壤NO_3^--N变化动态基本一致,但10~20 cm层土壤NO_3^--N含量的变化动态表现各异。解冻期间,除长白松林外,红松阔叶林与次生白桦林的0~10 cm层土壤NH_4^+-N和NO_3^--N含量显著高于10~20 cm层土壤。土壤解冻中前期以NH_4^+-N生成为主,而解冻中后期,NO_3^--N生成量显著增加。

The in-situ culture continuous sampling method was used to determine and analyze different N forms（NH4^＋-N,NO3^--N and microbial biomass N（MN）） in three kinds of forest in Changbai Mountain area during spring thawing,and further to study the effect of soil freezing and thawing process on nitrogen（N） turnover.Soil MN showed the obviously temporal and vertical spatial variations in the three forests during soil thawing process.The content of soil MN at 0-10 cm soil layer was significantly higher than that at 10-20 cm soil layer.The content of NH4^＋-N showed consistent changes in three forest soils during the whole thawing,and it appeared the peak in the middle and late stage of thawing.The change of NO3^--N at 0-10 cm soil layer was similar but different at 10-20 cm soil layer in the three forests during spring thawing.During the spring thawing period,the contents of NH4^＋-N and NO3^--N at0-10 cm soil layer were significantly higher than that at 10-20 cm soil layer of Korean pine broad-leaved forest and secondary birch forest except for Larix olgensis forest.NH4^＋-N was the dominated form of N at the early stage of thawing while NO3^--N increased significantly at the late stage of thawing.