Slope and soil nutrients can explain the distribution of Phragmites australis and Phragmites japonica in riparian wetlands

Selecting appropriate plant species is required for effective vegetational restoration. Phragmites australis and Phragmites japonica are large perennial grasses frequently used for restoration of wetland ecosystems. They have different distribution ranges along stream. We analysed plant density, stream slope, and physicochemical characteristics of soil at their habitats to distinguish environmental factors responsible for the distribution ranges. P. japonica was distributed at upper stream side with average slope of 8.4 m/km whereas P. australis inhabited at lower stream side with average slope of 1.7 m/km. Moisture content, organic matter, PO4‐P, NH4‐N, K+, and Ca2+ contents in soil were significantly higher at habitats of P. australis than those at habitats of P. japonica. Canonical correspondence analysis showed that NH4‐N, K+, and organic matter contents had the strongest influences on the density of these two species. The density of P. australis and P. japonica can be explained by the following multiple linear regression models with soil NH4‐N and K+ contents: DPJ = 97.471–0.052CNH4‐N − 0.185CK and DPA = 7.533 + 0.135CNH4‐N + 0.032CK (DPA = Density of P. australis, DPJ = Density of P. japonica, CNH4‐N = Content of NH4‐N, CK = Content of K+). These models can be used as references to select P. japonica or P. australis for restoring stream ecosystem.