Abstract: Aims Leaf traits are closely related to plant light use efficiency and photosynthesis. They can indicate plant adaptation strategies to the environment. Spartina alterniflora is a major alien invasive plant of coastal wetlands, and it seriously threatens the coastal wetland ecosystem in China. Tidal gradient is one of the main limiting factors for the growth and distribution of S. alterniflora in coastal wetlands. However, there has been very little research directly examining the pattern and adaptation mechanism of leaf traits of S. alterniflora along a tidal gradient. Methods In this study, a tidal gradient control platform was established in Zhangjiang Estuary, Fujian province. We studied the response pattern and driving factors of leaf functional traits (length, width, length/width ratio, area, dry mass, and specific leaf area) of S. alterniflora to a tidal gradient (relative elevation). Important findings The results showed that: (1) The leaf length, leaf width, leaf area, and leaf dry mass of S. alterniflora decreased with the increase in elevation, whereas the leaf length/width ratio increased with the increase in elevation. (2) The specific leaf area of S. alterniflora and elevation showed a hump-shaped relationship. (3) The effects of inundation frequency, soil porewater salinity, and soil water content on leaf traits were different. The leaf length, leaf width, leaf area, and leaf dry mass of S. alterniflora increased with the increase in inundation frequency and soil water content, but decreased with the increase in soil porewater salinity; the leaf length/width of S. alterniflora decreased with the increase in inundation frequency and soil water content, but increased with the increase in soil porewater salinity; the specific leaf area of S. alterniflora increased first and then decreased in inundation frequency, and increased with the increase in soil water content. In summary, the patterns and main driving factors of leaf traits of S. alterniflora differed along a tidal gradient, and this finding may be due to the various effects of leaf traits on plant physiological processes. Thus, S. alterniflora can adapt to a tidal gradient by adjusting leaf traits and the trade-offs among these traits, which provides a new perspective for understanding and predicting its ecological adaptation to sea level rise in coastal wetlands.

Key words: coastal wetlands, biological invasion, leaf functional traits, tidal elevation