河岸带土壤反硝化速率特征及其对外源氮、碳的响应

Denitrification characteristics of riparian soil and its response to exogenous nitrogen and carbon sources

选取湖北省滠水河支流夏家寺河河岸带土壤为研究对象,测定其理化性质并借助恒温厌氧淹水培养法测定外加不同质量浓度的氮源(0.0、0.5、1.0、2.0、5.0 mg·L^(-1))、碳源(0、20、50、100、200 mg·L^(-1))对不同离岸距离及不同土层深度的土壤反硝化速率的影响.结果表明:(1)无论夏季还是冬季,近岸区及表层土壤反硝化速率均最高.(2)影响夏季和冬季河岸带土壤反硝化速率的主要因子分别为硝酸盐(NO-3-N)质量分数和土壤有机碳(SOC)质量分数,NO_(3)^(-)-N、SOC质量分数均与反硝化速率呈正相关关系.(3)在同一培养期内,土壤反硝化速率随氮源质量浓度的增大而升高;0.5与5.0 mg·L^(-1)氮源处理组的土壤反硝化速率净增加幅度较小;土壤反硝化速率在培养12 h时达到最大值,随时间的延长呈一阶指数函数递减(R^(2)>0.91).(4)随着碳源质量浓度的增加,同期培养的土壤反硝化速率增大;20与200 mg·L^(-1)碳源处理组的土壤反硝化速率净增加幅度较小;土壤反硝化速率在培养24 h时达到峰值,随后减小并逐渐趋于平稳.这说明氮源、碳源是影响河岸带土壤反硝化过程的主要因子.

An anaerobic flooding culture experiment at a constant temperature was performed to explore the effect of nitrogen(0.0,0.5,1.0,2.0 and 5.0 mg·L^(-1))and carbon(0,20,50,100 and 200 mg·L^(-1))on the soil denitrification rate,whose soil samples were collected at different offshore distances and soil depths in the Xiajiasi River's riparian zone,a tributary of the Sheshui River in Hubei Province.The results showed that(1)In both summer and winter,the denitrification rate in the offshore area and topsoil soil were the highest.(2)Nitrate and soil organic carbon(SOC)contents were the primary factors affecting the denitrification rate of riparian soils in the summer and winter,respectively,which were positively correlated with the denitrification rate.(3)During the same culture period,the soil denitrification rates were increased with nitrogen(N)concentrations,and the net increase of denitrification rate was low at N concentrations of 0.5 and 5.0 mg·L^(-1).The denitrification rate reached the maximum after cultured for 12 h,and then decreased following a first-order exponential function over time(R2>0.91).(4)With the increase of C concentration,the soil denitrification rates were also increased during the same culture period,with net increases being marginal at C concentrations of 20 and 200 mg·L^(-1).Overall,the soil denitrification rate peaked after cultured for 24 h,followed a decrease and ended up with a plateau.Therefore,N and C sources were the major factors influencing the denitrification process of riparian soils.