## 5 Conclusions  
1. The main conclusions of this study are as follows. In the survey of floodplain plants in the riparian zone of the Lingshan River, a total of 104 species belonging to 12 families were recorded, in which Poaceae (16.67%) and Compositae (9.65%) showed significant dominance.
2. In the plant community delineation based on the complete linkage clustering, five plant communities were classified along the longitudinal scale of the river, four plant communities were in the near-water zone, and three plant communities were in the far-water zone. The Lingshan River riparian area is similarly spatially differentiated, with the dominant community in the longitudinal space being the _Cynodon dactylon_ (L.) Pers.--_Conyza canadensis_ (L.) Cronq. community. The dominant community in the near-water zone (0 m from water) in the lateral space is the _Artemisia argyi_ Levl. et Van.--_Alternanthera philoseroides_ (Mart.) Griseb. community, and also an endemic plant community--the _Marsilea quadrifolia_ L. community. The dominant community in the far-water zone (15 m from the water) is the _Artemisia argyi_ Levl. et Van.--_Alternanthera philoseroides_ (Mart.) Griseb. community.
3. Under conditions of natural water level variation, the plant diversity and community distribution in the riparian area of the Lingshan River are highly differentiated in each space. From a longitudinal spatial point of view, the diversity of species and the number of species are significantly differentiated, and the diversity index from the upstream to the downstream shows a significant decrease. When analyzed from the lateral point of view, the biomass of the near-water zone is generally higher than that of the far-water zone when compared with that of the zone at a distance of 15 m from the water. However, the diversity of species shows a reversed trend.
4. The environmental factors affecting the distribution of plants varied under different spatial influences, and this study showed that plant communities in the longitudinal space were mainly correlated with soil physical factors and had the highest degree of response to soil texture. Meanwhile, the plant communities in the lateral space had a high correlation with soil chemical factors, of which the dominant ones were soil organic matter and soil nitrate nitrogen content.  
K.X.: Conceptualization, methodology, investigation, writing--review and editing, formal analysis, writing--original draft, visualization, data curation; J.X.: writing--review and editing, funding acquisition, supervision, project administration, resources; L.S.: methodology, investigation, visualization; Y.W.: investigation, formal analysis, data curation; J.Z.: investigation and formal analysis; Q.W.: investigation and formal analysis; S.J.: investigation and formal analysis. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the Science & Technology Fundamental Resources Investigation Program (Grant No. 2022 FY100404); the National Key Research and Development Program of China [Grant No. 2018 YFD0900805]; the Key Program of Water Conservancy Science and Technology of Fujian Province [Grant Nos. MSK202403, MSK202404]; the National Natural Science Foundation of China (Grant NO. 52309047); and the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basins (China Institute of Water Resources and Hydropower Research, Grant NO. IWHR-SKL-KF202301).  
Not applicable.  
The data presented in this study are available upon request from the corresponding author. The data are not publicly available due to data that also forms part of an ongoing study.  
**Acknowledgments:** The authors would like to thank [PERSON], [PERSON], and [PERSON] for their help in field investigations and laboratory experiments. We sincerely thank these experts in the reviewing, editing, publishing, and dissemination of this work.  
**Conflicts of Interest:** The authors declare no conflict of interest.