Diffusion Mechanism Of Invasive Species Spartina Alterniflora

Spartina alterniflora,an alien species,has invaded and severely harmed the intertidal coast with different effects on the ecology,landscape and economy in China.Therefore,it is urgent to study the invasion mechanism of S.alterniflora to effectively control it.The Yellow River Delta(YRD)is one of the most affected areas by S.alterniflora in North China.In this study,a transplanting experiment of S.alterniflora was carried out in the intertidal zone of YRD.In June 2019,the seedlings(seed germinated seedlings)and clonal ramets(rhizome germinated seedlings)of S.alterniflora were transplanted to different locations with elevations ranging from 65.5cm to 114.7 cm.To detect the effect of different elevation on the growth and expansion of S.alterniflora seedlings in the intertidal zone and the elevation threshold for S.alterniflora survival,regular investigations of the growth status of S.alterniflora,tide and soil properties at the transplanting sites were conducted.The results showed that:(1)With the increase of elevation,there were significant differences in the duration and depth of tidal flooding in the intertidal zone of YRD;(2)In YRD,the main factors affecting the growth and reproduction of S.alterniflora were the average flooding time,average flooding depth and soil PH resulting from the combined action of elevation and tide;(3)In general,the growth status of seedlings and clonal ramets of S.alterniflora became worse with the increasing elevation,the seedlings could survive in the Suaeda salsa dominant area,and clonal ramets could survive in areas dominated by Phragmites australis and Tamarix ramosissima at higher elevation;(4)Along the direction from sea to land,S.alterniflora could rapidly expand to the Suaeda salsa dominant area in a short time,and after a long term,S.alterniflora might invade to Phragmites australis or even Tamarix ramosima dominant zones.Therefore,the control of S.alterniflora in northern China is urgent.Firstly,the sexual reproduction of S.alterniflora seeds should be effectively controlled to limit or prevent its long-distance expansion by the seeds.Secondly,the control pace of S.alterniflora should be accelerated.Otherwise,after long-term adaptation,S.alterniflora is likely to expand further to the land,leading to direct competition with the native vegetation Phragmites australis and Tamarix ramosissima,and strengthening its threat to intertidal ecosystems.