Abstract: Based on field surveys, literature reviews, and satellite remote sensing, we investigated the spatiotemporal variations and mechanisms of Spartina alterniflora invasion in the Jiaozhou Bay coastal wetland of Qingdao. The results showed that S. alterniflora invasion in the Jiaozhou Bay exhibited distinct spatiotemporal characteristics. Specifically, the estuary of the Yanghe River had the largest invasion area (338.75 hm²) and the fastest expansion rate. In contrast, the invasion areas at the confluence estuary of the Moshui River and the Baisha River and the eastern tidal flat area of the Jiaozhou Bay National Ocean Park were relatively smaller, but the growth trend was noticeable. The invasion of Spartina alterniflora in the Jiaozhou Bay coastal wetland could be attributed to four main factors: (1) the intrinsic biological traits of Spartina alterniflora; (2) the unique environmental conditions of the Jiaozhou Bay; (3) S. alterniflora mainly invaded through three expansion modes: external isolation expansion, edge expansion, and tidal creek-led expansion. It occupied the Yanghe Estuary area, the confluence estuary area of the Moshui River and Baisha River, and the eastern tidal flat area of Jiaozhou Bay National Marine Park respectively, showing different expansion rates and spatial characteristics; and (4) the impact of human activities (such as the construction of sewage outlets and rubber dams, and aquaculture) on S. alterniflora invasion in the Jiaozhou Bay coastal wetland (the northern bank of the Yanghe estuary, the eastern river channel from the Baisha River estuary, and the eastern tidal flat area of the Jiaozhou Bay National Ocean Park). By elucidating the spatiotemporal variations of S. alterniflora invasion, this study revealed the invasion mechanisms in the Jiaozhou Bay coastal wetland, providing a scientific basis for the development of rational wetland protection and S. alterniflora control strategies to prevent the secondary invasion. These findings offer enlightening implications for policy-making and practical applications in related fields.

Key words: Spartina alterniflora, Jiaozhou Bay coastal wetland, remote sensing monitoring, spatiotemporal dynamics, invasion mechanism