Modelling the effects ofSpartina alterniflorainvasion on the landscape succession of Yancheng coastal natural wetlands, China

Abstract

BackgroundThe Yancheng coastal natural wetlands (YCNR) are well-preserved silty tidal flat wetlands in China. Due to the severe invasion ofSpartina alterniflora, the native ecosystem has undergone great changes. The successful invasion ofS. alterniflorareduced the biodiversity of the YCNR, changed the structure and function of the local ecosystem, and eventually led to the degradation of the ecosystem and the loss of ecosystem function and service. Fully understanding the impact of an alien species invasion on YCNR succession is an important prerequisite for protecting and restoring the wetlands.MethodsIn this study, remote sensing, GIS technology, and a cellular-automaton Markov model were used to simulate the natural succession process of native ecosystems without being affected by alien species. By comparing the landscape of the YCNR with the model simulation results, we gained a better understanding of how alien species affect native landscape-scale ecosystems.ResultsDuring the natural succession of the coastal native wetland ecosystem in the YCNR, the pioneer speciesS. alternifloraoccupied the mudflats and expanded seaward. The whole area expanded and moved seaward with an average annual movement of 58.23 m. Phragmites australis seemed to dominate the competition withS. salsacommunities, and the area gradually expanded with an average annual movement of 39.89 m. The invasion ofS. alterniflorachanged the native ecosystem’s spatial succession process, causing theS. salsaecosystem to be stressed by ecosystems on the side of the sea (S. alterniflora) and that of land (P. australis). The area of the seaward-expandingP. australisecosystem has been declining. Under a reasonable protected area policy, human activities have enhanced the succession rate of the P. australis ecosystem and have had a small impact on the ecological spatial succession ofS. salsaandS. alterniflora.