Multiple Sources Forcing Driving Changes in Spatial Patterns of Coastal Wetland Vegetation

Abstract

Vegetation evolution is an important indicator of regional ecosystems and sea–land interactions. In this study, we investigated the evolution of coastal wetland vegetation, focusing on the core area of Yancheng City National Rare Bird Nature Reserve. Using high-precision classification based on phenological characteristics, we delineated the evolutionary process of three predominant wetland vegetation types: Spartina alterniflora, Suaeda salsa, and Phragmites australis. Spatial and temporal patterns were analyzed using the generalized additive model to identify drivers of evolution. From 1990 to 2022, a three-stage shift in vegetation distribution from land to sea was observed. Notably, S. salsa’s distribution area consistently shrank since 2000, whereas P. australis continued to grow. Throughout the entire period, S. alterniflora consistently maintained growth and tended toward stability. The vegetation distinctly showcased zonal patterns along the coastal gradient, revealing a clear inclination to migrate toward the seaside. Specifically, S. alterniflora displayed a centroid migration rate of 195.28 m/year, shifting northward, whereas P. australis and S. salsa migrated eastward (toward the seaside) at rates of 111.84 and 70.88 m/year, respectively. Environmental factors, such as downward irradiance, sea surface salinity, and significant wave height, significantly influenced vegetation patterns. Human activities, particularly aquaculture pond construction, emerged as the primary anthropogenic factor causing the reduction in P. australis distribution. Additionally, the competition for ecological niches among vegetation emerged as a pivotal factor contributing to the alterations in the landscape pattern within the study area.