Ecostoichiometric Characteristics Of Soil And Its Environmental Response In The Lakeshore Of Yilong Lake

The lakeside zone is an ecological transition zone between terrestrial ecosystems and aquatic ecosystems,which is of great significance for the exchange of materials and energy between aquatic and terrestrial ecosystems.In recent years,due to climate change and the increasing number of unreasonable human activities,the ecosystem of the lakeside zone has been destroyed,resulting in the continuous shrinkage of the lakeside zone area and the continuous decline of the function of maintaining ecological balance.In this paper,taking the lakeside zone of Yilong Lake as the research object,tow methods including indoor analysis and model fitting are used to analyze soil carbon（C）,nitrogen（N）,phosphorus（P）and p H in different seasons（dry season,rainy season,dry season and rainy season transition period）and different depths（0-10 cm,10-20 cm,20-30 cm）,researching the temporal and spatial distribution law and correlation between soil C,N,,P and their ecological stoichiometry ratio（C/N/P）in the lakeside zone,discussing the influencing factors of soil carbon,nitrogen and phosphorus temporal distribution in the lakeside zone and their relationship with lake water quality,and analyzing the response mechanism of C,N,P to lakeside ecosystem environment.The paper provides a theoretical basis for the ecological restoration and lake governance of Yilong Lake in the future.The main research conclusions of this paper are as follows:（1）In terms of time,TOC,TN and TP in the lakeside zone of Yilong Lake show the order of rainy season（August）>the drought-rain transition period（April）>dry season（November）.In terms of space,the order of TOC,TN and TP are roughly water zone>subsidence zone>land zone,and the vertical direction shows the trend of soil decline from surface layer to deep layer.The spatial distribution of soil C/N content in the rainy season（August）is consistent with that in the drought-rain transition period（April）and dry season（November）,showing the order of land zone>water-fluctuation zone>water zone.The spatial patterns of C/P and N/P in rainy season（August）and drought-rain transition period（April）are water zone>fluctuation zone>land zone.In the vertical direction,C/N and C/P are in the order of deep>shallow>surface layer.The vertical distribution of C/P in November is shallow>deep>surface.The average values of TP（0.5 mg/g）and N/P（10.3）are lower than those of soil TP（0.8 mg/g）and N/P（61）in China.Other TOC（61.1 mg/g）,TN（2.7 mg/g）,C/N（35.54）and C/P（135.7）are higher than the average TOC（24.6 mg/g）,TN（1.9 mg/g）,C/N（11.9）and C/P（5.2）in China.（2）The results of variogram analysis of TOC,TN and TP in the soil surface layer（0-10 cm）in the lakeside zone in the dry season show that besides TP for spherical model and C/P for exponential model,the models of other indexes are Gaussian models.In November,besides TN and C/N as a spherical models,the models of the rest of the indicators are Gaussian models.From the results of the rainy season fitting model,except for C/N and C/P as Gaussian models,the models of the remaining indicators are spherical models.The analysis results of the semi-variance function show that except for TP（49.1%）showing median correlation in November,all other indicators show strong spatial correlation.Soil TOC and TP in April,soil TN and TP in August,and TOC in November have the smallest nugget value of 1×10^-4.（3）The correlation analysis results between April and November of dry season are similar,and TOC shows a very significant positive correlation with TN and TP,with correlation values of 0.61,0.75,0.66,and 0.58,respectively.TN and N/P show a very significant positive correlation,with correlation values of 0.86 and 0.70,respectively,and a very significant negative correlation with C/N,with correlation values of-0.75and-0.71,respectively.TP and C/P are significantly negative correlation.The correlation between nutrient content and elemental stoichiometry ratio in soil are weak during the rainy season（August）,and TN shows a significant positive correlation with N/P（0.48）and a very significant negative correlation with C/N（-0.61）.（4）The temporal and spatial distribution of soil carbon,nitrogen and phosphorus and their eco-stoichiometry ratio in the coastal zone of Yilong Lake are affected by seasonal changes,soil depth,temperature and humidity.In summer,vegetation grows vigorously,which promotes the reproduction of soil microorganisms,resulting in organic matter content increase;in autumn,plant growth and root secretion decrease,and the content of organic carbon and nitrogen continues to decline.In addition,the root system of plants is mainly distributed in the shallow layer of the soil,and with the deepening of the soil profile,the root system gradually decreases,and the source of organic carbon naturally decreases,so the organic carbon content decreases with depth.Finally,the distribution pattern is rainy season（August）>the drought-rain transition period（April）>dry season（November）,and the surface>shallow>deep layers.In this study,soil N and P are essential nutrients for plant growth in the lakeside zone and important factors restricting the healthy development of ecosystems,while plant residues are important input methods for soil carbon pool,so that C,N and P form a close relationship.（5）There are great differences in the correlation between soil TOC,TN,TP,C/N,C/P,N/P,and water quality TP,TN,NO₃^--N,NH₄⁺-N,COD,DOC,p H in dry and rainy season.Soil TOC and TP are negatively correlated with water quality DOC and TP in the dry season.There are positive correlations between soil TOC and water quality COD,soil TN and water quality TN,soil TP and water quality TP in the rainy season.The increase in rainfall during the rainy season adds the runoff into the lake,so that C and N elements in the topsoil enter the lake with the runoff.In addition,artificial water adjustment and agricultural fertilization have increased C and N elements in lake water,and intensified lacustrine eutrophication.