氮添加对黄河三角洲滨海湿地土壤有机碳矿化的影响

Effect of Nitrogen Addition on Soil Organic Carbon Mineralization in Coastal Wetlands of the Yellow River Delta

在山东黄河三角洲国家级自然保护区大气氮沉降模拟实验区样地采集表层(0-10 cm)和下层(10-20cm)两层土壤样本,设置NH4NO3、NH4Cl、KNO3三种氮肥类型以及5 gN·m-2·yr-1、10 gN·m-2·yr-1、20 gN·m-2·yr-13种施氮浓度梯度,通过26 d室内恒温矿化培养试验,测定温室气体CO2释放速率和累计释放量,研究模拟氮沉降对滨海湿地土壤有机碳矿化影响。不同处理下土壤有机碳的累积矿化量随培养时间逐渐增加,培养初始阶段的增长速率较快,前10 d土壤累积矿化量约占整个培养期内总矿化量的50%左右,而后逐渐减慢。外源氮添加促进了滨海湿地土壤有机碳的累积矿化量,上下层土壤实验处理较对照分别增加7.60%~68.60%、6.75%~67.24%,铵态氮(NH4NO3、NH4Cl)均表现为中氮组(41.39%、68.60%)>高氮组(27.02%、53.69%)>低氮组(13.78%、7.60%),硝态氮(KNO3)表现为高氮组(66.12%)>低氮组(49.05%)>中氮组(32.10%)。较高或较低氮浓度下,硝态氮对有机碳矿化的促进作用强于铵态氮,但在中氮组中NH4Cl处理组有机碳平均矿化量最高,达1411.82μg/g soil。下层土壤中,NH4Cl实验组的促进作用在不同施氮量下均最高,有机碳平均矿化量分别为666.90μg/g soil、797.28μg/g soil、834.98μg/g soil。各处理土壤表层有机碳累积矿化量显著高于底层土壤(P<0.05),即表明上层土壤有机碳含量较高。

0-10 cm and 10-20 cm two layers of soil samples were collected from the atmospheric nitrogen deposition simulation experimentation area at the Yellow River Delta coastal wetland test station.Three nitrogen types of NH4NO3,NH4Cl,KNO3,5 gN·m-2·yr-1,10 gN·m-2·yr-1,20 gN·m-2·yr-1,three kinds of nitrogen concentration gradients were used,and the incubation of three nitrogen concentration gradients was made through 26-day mineralization indoor incubation.The CO2,CH4,N2O release rate and cumulative release amount of greenhouse gases were measured to study the effects of simulated nitrogen deposition on soil organic carbon mineralization in coastal wetlands.The cumulative mineralization of soil organic carbon in different treatments increased gradually with the culture time,and the growth rate was faster in the initial stage of culture.The cumulative mineralization of the first 10 d soils accounted for about 50% of the total mineralization in the whole culture period,and then gradually slowed down.The addition of exogenous nitrogen promoted the cumulative mineralization of soil organic carbon in coastal wetland,and the experimental treatment of upper and lower layers increased by 7.60%~68.60%,6.75%~67.24% respectively,and ammonium nitrogen(NH4NO3,NH4Cl)were all in the middle nitrogen group(41.39%,68.60%)>high nitrogen group(27.02%,53.69%)>low nitrogen group(13.78%,7.60%),and nitrate nitrogen(KNO3)showed high nitrogen group(66.12%)>low nitrogen group(49.05%)>medium nitrogen group(32.10%).At higher or lower nitrogen concentration,the nitrate nitrogen has a stronger effect on the mineralization of organic carbon than ammonium nitrogen,but the average mineralization of organic carbon in the NH4Cl experimental group is the highest in the middle nitrogen group,up to 1411.82μg/g soil.In the lower soil,the promotion effect of NH4Cl experiment group was the highest under different nitrogen application.The average mineralization of organic carbon was 666.90μg/g soil,797.28μg/g soil and 834.98μg/g soil,respectively.The cumulative mineralization of organic carbon in the soil surface was significantly higher than that in the bottom soil(P<0.05),that means the upper soil has higher organic carbon content.