Relationship between Wetland Plant Communities and Environmental Factors in the Tumen River Basin in Northeast China

Understanding what controls wetland vegetation community composition is vital to conservation and biodiversity management. This study investigates the factors that affect wetland plant communities and distribution in the Tumen River Basin, Northeast China, an internationally important wetland for biodiversity conservation. We recorded floristic composition of herbaceous plants, soil properties, and microclimatic variables in 177, 1 × 1 m2 quadrats at 45 sites, located upstream (26), midstream (12), and downstream (7) of the Basin. We used TWINSPAN to define vegetation communities and canonical correspondence analysis (CCA) to examine the relationships between environmental and biological factors within the wetland plant communities. We recorded 100 plant species from 93 genera and 40 families in the upstream, 100 plant species from 57 genera and 31 families in the midstream, and 85 plant species from 76 genera and 38 families in the downstream. Higher species richness was recorded upstream of the River Basin. The plant communities and distribution were influenced by elevation, soil properties (total potassium, pH, and available phosphorus), and microclimate variables (surface temperature, precipitation, average temperature, sunshine hours, and relative humidity). More than any other factor, according to our results, elevation strongly influenced the structure of wetland plant communities. These findings support prevailing models describing the distribution of wetland plants along environmental gradients. The determination of the relationship between soil and plants is a useful way to better understand the ecosystem condition and can help manage the wetland ecosystem.