APPROACH ON THE DYNAMIC CHANGE AND INFLUENCE FACTORS OF SPARTINA ALTERNIFLORA LOISEL SALTMARSH ALONG THE COAST OF THE JIANGSU PROVINCE

Spartina alterniflora Loisel salt marsh in the coastal area in Jiangsu is manmade salt marsh, which has been a focus of dispute in the recent years, but up to now, we almost know little about the distribution, area, spread speed and mechanism of Spartina alterniflora Loisel salt marsh . Through routine measure method to collect information is too hard and expensive to carry out. The paper studied dynamic changes of Spartina alterniflora Loisel salt marsh in the coast of the Jiangsu Province based on GIS and RS technology. 12 phases of TM, ETM+ and SPOT satellite imageries from 1988 to 2001 were collected, pretreatment to the satellite imageries including research area selection, atmospheric correction and image mosaic were made to the satellite images. Information such as distributian and area of Spartina alterniflora Loisel salt marsh extending from Shuangyang harbor to Liangduo Dam was extracted by using supervised classify method. By superimposing distributian map of Spartina alterniflora Loisel salt marsh of different periods, we studied the spreading process of Spartina alterniflora Loisel salt marsh along Jiangsu coast, and some conclusions were drawn from these analysis: (1) Spartina alterniflora Loisel salt marsh in Jiangsu coast has a striking fast spread speed, for a example, the area of Spartina alterniflora Loisel was 4.439km 2 in 1988, while it was 129.28km 2 in July, 2001, which was almost 30 times of 1988. After near 20 years spread, the high and middle inter tidal flat was almost all covered by Spartina alterniflora Loisel salt marsh form Sheyang Harbor to Liangduo Dam till 2001. (2) Influenced by the niche of Spartina alterniflora Loisel salt marsh, the expanding speed paralleling to the shoreline was larger than the speed vertical to the shoreline, the former was over two times than the latter. (3) According to the satellite imageries of research area, we found the expanding speed curve of Spartina alterniflora Loisel salt marsh seems like parabola curve, which has a low speed in the beginning, increasing fast in the rapid spreading period and descending in the mature period. Natural environment factors play a important role in the Spartina alterniflora Loisel salt marsh, sedimentation environment and climate of Jiangsu coast is similar to the east coast of USA., which is the origin producing area, so the salt marsh has a fast spread speed. Anthropogenic factors, such as reclamation project deeply affect Spartina alterniflora Loisel salt marsh too, 25.34km 2 Spartina alterniflora Loisel salt marsh were reclaimed and about 2.58 km 2 salt march were destroyed from March ,2000 to July 2001.