Spatial distribution characteristics and influencing factors of soil nitrogen in damaged wetland in double-returned area of Poyang Lake
[Objective]Soil nitrogen is an important indicator of wetland nutrient levels.Investigation on the spatial distribution characteristics and influencing factors of soil nitrogen in damaged wetlands in the double-returned areas of Poyang Lake could provide scientific basis for ecological restoration and reconstruction of damaged wetland vegetation in Poyang Lake.[Method]In the Maying Lake wetland located in Duobao Town,Duchang County,Jiangxi province,which is considered a typical double-returned area of returning farmland to lake area in Poyang Lake,four types of damaged wetland soils including marsh soil,meadow soil,meadow swamp soil and secondary meadow swamp soil were selected,and the total nitrogen(TN)and nitrate nitrogen(NO3--N)and ammoniacal nitrogen(NH4+-N)were investigated.The clustering tree algorithm were used to quantifying the relative contribution of environmental factors to nitrogen,Pearson correlation was used to analyze the relationship between soil nitrogen and environmental factors in the wetland,and structural equation model was used to analyze the impact of environmental factors on nitrogen.[Result]The highest content of NH4+-N was observed in the middle layer soil for swamp soil,and the highest contents of soil TN,NO3--N,and NH4+-N were observed in the middle layer soil and deep soil for secondary meadow swamp soil,respectively.The highest levels of nitrogen of the other soil types were observed in the surface layer,which were TN(0.35±0.03)g/kg,NH4+-N(4.02±0.38)mg/kg and NO3--N(4.84±0.53)mg/kg,respectively.Soil depth and available phosphorus(AP)had an important impact on nitrogen distribution and accumulation.Soil pH indirectly affected nitrogen by affecting soil organic carbon(SOC),AP,and available potassium(AK).Cation exchange volume(CEC)indirectly affected nitrogen by affecting SOC.[Conclusion]Compared with the natural wetlands of Poyang Lake,the soil nitrogen contents of the four types of damaged wetlands in the research area were at extremely low levels,and the highest level of nitrogen were concentrated in the soil surface.Among them,meadow soil had the highest TN content and it was the most vulnerable to leaching,followed by meadow marsh soil and secondary meadow swamp soil.Swamp soil had the least TN and it was easily washed by running water.The accumulation and distribution of nitrogen were affected by soil depth,AP,pH,CEC,etc.
wetland soil nitrogeninfluencing factorsthe structural equation modelthe double-returned areasdamaged wetland in Poyang Lake
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