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

【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 N₅treatment 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.