Background: On the coast of China, Spartina alterniflora ( S. alterniflora ) is an invasive plant that replaces native vegetation and has a serious negative impact on the local ecosystem. Monitoring the spatial distribution of and dynamic change in S. alterniflora can reveal its expansion mechanism and is critical for coastal ecosystem management. The purpose of this study was to map the distribution of S. alterniflora in Zhejiang Province from 1985 to 2015 using a time series of Landsat TM/OLI images and analyze its temporal and spatial expansion patterns.

Results: Based on the Landsat images of four periods (1985, 1995, 2005 and 2015), the distribution of S. alterniflora was mapped using a decision tree combined with expert knowledge, and then the temporal and spatial heterogeneity of the dynamic changes in S. alterniflora were analyzed. The classification accuracy was 90.3%. S. alterniflora has expanded rapidly in recent decades after being introduced into southern Zhejiang. Between 1985 and 2015, S. alterniflora increased its distribution by 10,000 hm 2 , replacing native vegetation and becoming the main salt marsh vegetation in tidal flats. Overall, S. alterniflora expanded from south to north and had the fastest expansion rate (463.64 hm 2 /year) between 1995 and 2005. S. alterniflora was widely distributed in the tidal flats of bays and estuaries and expanded outward as sediment accumulated.

Conclusions : This study reveals the dynamic change in S. alterniflora in Zhejiang and contributes to the control and management of this invasive plant.