三江平原典型小叶章湿地土壤中硝态氮水平运移的模拟研究

选择三江平原小叶章湿地不同水分带上草甸沼泽土和腐殖质沼泽土2种土壤类型作为研究对象，以KNO3为示踪剂，模拟研究硝态氮在湿地土壤中的水平运移过程。结果表明，2种土壤各土层硝态氮水平运移浓度和速率均与运移距离呈极显著负相关（P〈0．01），并随运移距离增加呈一阶指数衰减曲线变化，各土层硝态氮水平运移速率主要受浓度梯度、水势梯度及土壤基质势的控制；土壤各土层中硝态氮水平运移速率与土壤含水量呈显著正相关（P〈0．05），并随土壤含水量增加呈指数增长曲线变化；土壤各土层中硝态氮水平运移浓度与土壤水分扩散率呈极显著正相关（P〈0．01），0—20cm土层硝态氮水平运移浓度随水分扩散率升高呈Boltzmann曲线变化，其他土层则呈指数增长曲线变化；草甸沼泽土比腐殖质沼泽土相应土层更利于硝态氮的水平运移，这主要与土层颗粒组成和孔隙度等物理性质的显著差异有关，而湿地水文条件可能对2种土壤物理性质的塑造有着重要影响。

Simulation of Horizontal Movement of Nitrate Nitrogen in Typical Calamagrostis angustifolia Wetland Soils of Sanjiang Plain

Two typical soils(meadow marsh soil and humus marsh soil),located in zones different in moisture regime in Calamagrostis angustifolia wetland of the Sanjiang Plain were selected for study of horizontal movement of nitrate nitrogen(NO~-_3-N) with KNO_3 as tracer.Results show that NO~-_3-N concentration and the movement rate were significantly and negatively related to the distance of NO~-_3-N horizontal movement in the two typical soils(P<0.01),showing a first-order exponential decay curve.NO~-_3-N horizontal movement was mainly controlled by concentration gradient,soil water potential gradient and soil matric potential;But the rate of the movement was significantly and positively related to soil moisture content(P<0.05),showing an exponential growth curve,and so was the concentration of NO~-_3-N in horizontal movement with the diffusion rate of soil water(P<0.01),showing a Boltzmann curve in the 0-20 cm soil layers and exponential growth curves in other soil layers.In conclusion,meadow marsh soil is more propitious to horizontal movement of NO~-_3-N than humus marsh soil,which is attributed to the significant differences in physical properties(grain composition and porosity,etc.) between the two typical soils,and hydraulic conditions might be important factors leading to formation of the two soils different in physical properties.