The Spatio-temporal Distribution Patterns Of Spartina Alterniflora In Luoyuan Bay Of Fujian

Since Chinese introduction of Spartina alterniflora in 1980,it has greatly and rapidly expanded in coastal areas of China,and it has a certain influence on the local ecosystem where it invaded.The study on temporal and spatial distribution of S.Alterniflora and its expansion characteristics can provide the basic data and theoretical basis for the prevention and control measures of S.Alterniflora.The largest expansion scale of S.Alterniflora can be found in Jiangsu,Shanghai,Fujian and Zhejiang.Luoyuan Bay of Fujian is the first introduction region of S.Alterniflora and it is the one of the largest invasion region in Fujian.This thesis presents the study results about S.Alterniflora's invasion in Luoyuan Bay.The thesis Explored the temporal and spatial distribution of S.Alterniflora in the whole Luoyuan Bay and its expanding process in every subregion,analyzed its expansion characteristics and impacts based on the remote sening images.Furthermore,the thesis chose some landscape indices to describe the pattern of S.Alterniflora landscape.The thermal effect contribution,thermal pixels proportion index and regional pixels proportion indices were designed to discuss the impact of S.Alterniflora on thermal environment.Finally,some proposals were putted forward to control the expanding of S.Alterniflora in study area.The main results in the thesis are listed as follows:(1)Aquaculture,reclamation,construction activities and tidal action are the main factors that change S.Alterniflora's invasion in study area.Through the study of the area change of S.Alterniflora in the whole Luoyuan Bay and its subregionals,and the impact factor of S.Alterniflora's invasion,it found that the main influence factors are different during different times and in different subregions.Subregion 1,2 and 5 were affected by human factors during the study period,and there was no growth of S.Alterniflora at present basically.Subregion3 is mainly affected by tidal action,from minimal patch,now it appears strip-shaped distribution in the high tide zone.subregion4 is the most suitable area for the growth of S.Alterniflora in Luoyuan Bay,the proportion of S.Alterniflora's area in this subregion to total S.Alterniflora's area in Luoyuan Bay was more than 85%,which was only 1.46%in 1990.It is the main growing area of S.Alterniflora at present.(2)The main expansion features of S.Alt.erniflora were striped expansion,grew in the population gap,expanding along the creek,expanding from Landward or seaward.S.Alterniflora first appeared with small patches in the tidal flat wetland,and its patch number increased continuously in the high tide zone,finally it banded together,as showing strip-shaped distribution.Subsequently,S.Alterniflora extended along the direction of perpendicular to the coastline with strip-shape,and gradually reached the middle tidal zone.When it extended to the middle tidal zone,it remained stably and no longer continued to expand quickly.It began to grow in the gaps within the population,and the coverage of S.Alterniflora gradually became homogeneous in this region.In addition,the tide in the tidal creeks could scour the salt water to the both sides of the tidal channels,which is conducive to the growth of S.Alterniflora in the range.Therefore,S.Alterniflora showed the characteristics of expanding along the tidal creeks.(3)The thermal effect of S.Alterniflora on the region was closely related to its expansion.S.Alterniflora had thermal effects on its growth region,with its continuous expansion,the occupied became larger,and the thermal effect contribution index increased too.In 1993,because of its small area(2.4885km2),it had little thermal effect on the whole study area,and its thermal contribution was only 3.21%.In 2010,the area of S.Alterniflora tended to be stable,reaching about 7.5km2,and its thermal contribution was up to 29.48%.