Effects of alternate flooding–drought conditions on degenerated Phragmites australis salt marsh in Northeast China

The hydrological regime is the dominant factor associated with the degradation and restoration of inland salt marshes in Northeast China. This study investigates whether alternate flooding–drought conditions could be used to actively restore degraded inland salt marshes with the native plant Phragmites australis. Pot experiments were designed to examine changes in the growth and physiology of P. australis, as well as the saline–alkaline soil characteristics, in response to different hydrological regimes, alternate flooding–drought treatments, and single treatments of moisture, flooding, and drought. After 4 months of treatments, the P. australis population that grew in alternate flooding–drought conditions exhibited substantially more biomass accumulation and less Na⁺ absorption compared with the single treatments of moisture, flooding, and drought. Photosynthesis physiology served as regulating and adaptive responses to different water regimes, with increased values after the short‐term flooding, long‐term drought, and flooding–drought cycles. In addition, the saline–alkaline soil properties changed in response to the flooding–drought cycles. The flooding–drought cycles increased organic matter and total nitrogen contents, but decreased pH, electrical conductivity, and saline ion levels. Plant growth and saline–alkaline soil were improved by flooding–drought cycles (not drought–flooding cycles), which suggests that this may be an effective approach for restoration inland salt marshes.