通过室内模拟试验(2013年7月23日~8月15日),研究不同含水量(20%,35%,60%)条件对东北黑土区土壤氮素转化及土壤酶活性的影响,初步探讨了其作用机制。结果表明:随着培养时间的增加,不同含水量的铵态氮含量呈波动性变化,最后呈下降趋势;硝态氮含量随着时间的增加一直呈下降趋势,35%及60%含水量的黑土铵态氮和硝态氮含量在相同培养时间高于20%含水量的黑土。各含水量处理组氨化速率、矿化速率、硝化速率随着培养时间的增加均逐渐下降,说明土壤中可被转化的有机氮含量逐渐降低,60%含水量的黑土净矿化速率和净硝化速率变化幅度最大,分别从1.518 g kg-1d-1、1.376 g kg-1d-1下降到0.009 g kg-1d-1,0.007 g kg-1d-1;除了35%含水量处理组在24 h内的氨化速率高于其他两组含水量氨化速率外,整个培养期间的氮素转化速率均表现为60%含水量>35%含水量>20%含水量。对土壤酶活性的研究表明:在培养初期(前2 d),20%含水量土壤脲酶活性逐渐增加,35%和60%含水量土壤脲酶活性先增加后下降,随后脲酶活性趋于稳定,直到第13 d开始略有下降,总体来看,2 d后不同含水量对脲酶活性的影响变化不显著;而转化酶活性呈波动性变化,整个培养周期,35%含水量的转化酶活性始终高于60%含水量处理组,而20%含水量的转化酶活性在其他两组含水量的转化酶活性上下波动。研究表明含水量对黑土氮素转化影响显著,硝化、矿化、反硝化作用及土壤中微生物活性的变化是氮素转化及酶活性变化的主要原因。
In order to investigate the transformation among the precipitation,groundwater,and surface water in the Sanjiang Plain,Northeast China,precipitation and groundwater samples which were collected at the meteorological station of the Sanjiang Mire Wetland Experimental Station,Chinese Academy of Sciences and the surface water which collected from the Wolulan River were used to identify the transformation of three types of water.The isotope composition of different kinds of water sources were analyzed via stable isotope(deuterium and oxygen-18) investigation of natural water.The results show a clear seasonal difference in the stable isotopes in precipitation.During the cold half-year,the mean stable isotope in precipitation in the Sanjiang Plain reaches its minimum with the minimum temperature.The δ18O and δD values are high in the rainy season.In the Wolulan River,the evaporation is the highest in August and September.The volume of evaporation and the replenishment to the river is mostly same.The groundwater is recharged more by the direct infiltration of precipitation than by the river flow.The results of this study indicate that the water bodies in the Sanjiang Plain have close hydrologic relationships,and that the transformation among each water system frequently occurs.
