Species composition and community change of vegetation on coastal beaches of Haizhou Bay in Jiangsu Province.
The distribution status, species composition and community change of vegetation on coastal beaches of Haizhou Bay in Jiangsu Province in recent years were investigated by means of field survey, and those were compared with related investigation results in the 1980s. The results show that due to serious human interference, original beach in Haizhou Bay severely shrank, sand vegetation is generally destructed and its distribution area is sharply decreasing. At present, the vegetation only distributes in three beaches of Haitouzhen, Dashawan and Sumawan, in which, both of numbers of species and community distributing in Haitouzhen beach are relative more. There are 39 species existing in all beaches and species number increases than that of before, and newly added 25 species are mostly inland farmland and mountain plants, while number of typical psammophyte decreases. Dominant families and genera are not obvious, in which number of family only containing one species accounts for about 70% of the total number of family. In existing species, there are 25 species with individual number below 20, which accounts for 64.1% of total number of species. Life form of composition species in beach vegetation does not obviously change, they all are the winter deciduous species, and geophyte and seed overwintering plant are absolutely predominant, while only life form spectrum has changed. There are seven communities of Tournefortia sibirica, Carex kobomugi, Calystegia soldanella, Imperata cylindrica, Vitex rotundifolia, Salsola tragus and Astragalus chinensis, in which, A. chinensis community is a newly added community. Community types are still mainly herbaceous community (6 communities) in which constructive species is mostly perennial herbaceous species, also is typical psammophyte, and some communities have changed from co-dominant species community to mono-dominant species community. There are larger changes in original distribution pattern and succession series of these communities, and community distribution area obviously decreases. Community number in every beach differs obviously, in which, there are 6 communities in Haitouzhen beach, only 1-2 communities in Dashawan and Sumawan beaches. There are no common community among three beaches, only C. soldanella community and V. rotundifolia community are common for two beaches, respectively. There are some changes in every diversity index of all communities at different stages and in different beaches; the richness index of all communities increases with different degrees; the coverage and Shannon-Wiener diversity index (SW index) of most communities increase and Simpson diversity index (SP index) decreases. In seven communities, richness index, SP index and SW index are the highest in V. rotundifolia community, SP index and SW index are the lowest in I. cylindrica and richness index is the lowest in S. tragus community. According to the investigation results, main factors led to beach disappearance and vegetation change in Haizhou Bay are analyzed and the corresponding conservation and improvement measures are put forward.