The Response Of Soil Carbon, Nitrogen And Phosphorus Ecological Stoichiometry To The Invasion Of Spartina Alterniflora In Yanghekou Wetland

Taking the tidal flat wetland in the Yanghe estuarine wetland as case study,this study explored the distribution status and expansion rate of invasive species Spartina alterniflora.Then we analyzed the distribution characteristics and relevance of TOC,TN and TP with different time series of invasion,and discussed the impacts of ecological stoichiometric ratio of carbon,nitrogen,phosphorus.The main conclusions are as follows:(1)The area for Spartina alterniflora growth in Yanghe estuarine wetland increased from 1.7 hm2 in 2009 to 78.4hm2 in 2016,which shows the high ability of Spartina alterniflora to reproduce and spread.The expansion ratio of the area of Spartina alterniflora is different in different regions,of which the expansion ratio of the area of Spartina alterniflora in Yanghe estuarine wetland is the largest.It is because the ecological factors in Yanghe estuarine wetland are more suitable for growth and spread of Spartina alterniflora than other areas.(2)The soil TOC content(0-60cm)in different sample areas can be ranked as: SAF-8>SAF-5>SAF-1>MF,indicating that the soil TOC content in the Spartina alterniflora patches increased over time..The vertically change trends of soil TOC content were basically identical in sample area SAF-8,SAF-5 and MF wetland.Soil TOC content increased with extended their invasion,which is the accumulation effect in the time scale in Spartina alterniflora patches.Spartina alterniflora of C4 plants has a certain role in promoting to the accumulation of soil TOC,and the contribution to the deep soil TOC is smaller.(3)With different time series of invasion,the soil TN content in different sample areas can be ranked as: SAF-8>SAF-5>SAF-1>MF.Despite Soil TN content(0-60cm)horizontal distribution difference is obvious of SAF-1,SAF-5,SAF-8 and MF wetlands,but the content of the vertical variation characteristics are similar.As a whole,soil TN content increased with extended their invasion,and the variation characteristics were consistent with soil TOC content,namely the accumulation in the time scale effect.(4)The Soil TP content(0 ~ 60 cm)in sample area SAF-1,SAF-5,SAF-8 can be addressed as: SAF-1 < SAF-5 < SAF-8,indicating that the soil TP content increased over time.Nitrogen and phosphorus as the main restrictive elements of plant growth,its content in the soil with coupling,i.e.,the change of soil TP content characteristics consistent with TN content in the soil,characterized by increased with extended their invasion.(5)Soil C/N of Spartina alterniflora invasion increased over time.In contrast,the C/P,N/P diminished over time.Soil C content was high and the decomposition rate was low,which were the important reasons of high C/N in Spartina alterniflora.With the increase of invasion time,C/P showed a decreasing trend,which was related to the growth rate of TP and the growth rate of TOC at the time of invasion time.Spartina alterniflora growth need to consume large amounts of N elements,consumption and P elements are relatively small,which caused N/P present decreasing trends.