模拟氮沉降对尕海湿地土壤化学计量特征的影响

Effect of simulated nitrogen sedimentation on soil chemometric characteristics of the Gahai wetland

【目的】在全球氮沉降增加背景下,通过模拟研究氮沉降对湿地土壤化学计量特征的影响,有助于探明湿地生态系统土壤元素循环过程及平衡反馈机制。【方法】以青藏高原东部尕海湿地为研究对象,利用均匀喷洒法于2019年5月开展模拟氮沉降下野外控制试验,设置4种氮沉降处理,分别为空白对照CK(0 g/m^(2))、N5(5 g/m^(2))、N10(10 g/m^(2))和N15(15 g/m^(2))。分析不同处理下土壤有机碳(SOC)、全氮(TN)、全磷(TP)含量以及C∶N、C∶P、N∶P的变化。【结果】不同施氮量处理下土壤SOC、TN、TP含量主要表现为N10处理最高,N15处理最低。在土壤垂直剖面上,土壤SOC、TN含量随着土层的加深逐渐减小,土壤TP含量则先增大后减小。土壤SOC和TN含量随氮沉降质量浓度的增大呈先升高后降低的趋势,而TP含量呈先降低后升高的趋势。土壤化学计量比值(C∶N、C∶P、N∶P)均在0~10 cm土层最高,且显著高于其他土层(P<0.05)。在0~40 cm土层,N10处理下土壤C∶N最高,显著高于N5(21.18%)和N15(6.84%)处理;N5处理下土壤C∶P和N∶P最高,显著高于N5(14.85%、33.38%)和N10(32.27%、42.64%)处理。【结论】氮沉降增加显著影响湿地土壤碳、氮、磷含量及其计量比,P可能是本地区限制植物生长的一个主要因素,N处于相对平衡的状态。

【Objective】In the context of increasing global nitrogen deposition,a simulation study of the effect of nitrogen deposition on the soil chemometric properties will help to identify the soil element cycling process and the balance feedback mechanism of the wetland ecosystem.【Method】The Gahai wetland in the east of the Qinghai Tibet Plateau was considered as the experimental site.Four different nitrogen(N)treatments were organized including blank control CK(0 g/m^(2)),N5(5 g/m^(2)),N10(10 g/m^(2))and N15(15 g/m^(2))【.Result】The contents of soil organic carbon(SOC),total nitrogen(TN)and total phosphorus(TP)among the different N application treatments were the highest in the N10 treatment,while the lowest values were observed in the N15 treatment.Along the vertical soil profile,soil SOC and TN contents gradually decreased with the depth of the soil layer,while the soil TP first increased and then decreased.The SOC and TN contents first increased and then decreased with increasing N deposition concentration,while the TP content first decreased and then increased.The soil stoichiometric ratio was the highest in the 0~10 cm layer,and was significantly higher than that in other soil layers(P<0.05).In 0~40 cm layer,soil C∶N ratio was the highest in N10 treatment,and was significantly higher than that in N5(21.18%)and N15(6.84%)treatments.In addition,soil C∶P and N∶P ratios were highest in N5 treatment and were significantly higher than those in N5(14.85%and 33.38%)and N10(32.27%and 42.64%).【Conclusion】The increase in nitrogen deposition significantly affected the carbon,nitrogen and phosphorus contents and ratios in the wetland soils.Overall,the results indicate that phosphorus is a major limiting factor for plant growth in the study area and that N is in a relatively balanced state.