Associations of Inundation Duration with Soil Properties and Riparian Vegetation in Representative Riparian Sections of the Middle Yangtze River

Seasonal hydrological fluctuations strongly influence riparian habitats in the middle Yangtze River, yet the relationships of inundation duration with soil properties and riparian vegetation remain insufficiently understood in representative riparian sections. Here, field surveys and laboratory analyses were conducted to examine (1) inundation–soil associations and (2) soil–vegetation relationships. Soil moisture (W), pH, particle-size composition, soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and vegetation parameters were compared among inundation-duration zones. Partial redundancy analysis (pRDA) was used to evaluate the relationships between environmental factors and vegetation parameters after controlling for elevation and shoreline distance. Vegetation occurrence, coverage, and diversity decreased with increasing inundation duration, and no vascular plants were recorded in the severe-inundation zone. After accounting for topographic factors, TN and gravel were the main soil variables associated with vegetation variation. Overall, inundation duration was closely associated with soil variation, whereas vegetation variation was mainly associated with selected soil environmental factors. These findings provide site-based evidence for riparian ecological restoration in representative riparian sections of the middle Yangtze River.