Propagule types and environmental stresses matter in saltmarsh plant restoration

Restoration of degraded saltmarshes has attracted global attention, which makes disentangling the factors that determine target species success critically important. The pioneer plant Scirpus mariqueter in the Yangtze River estuary saltmarshes is rapidly declining due to plant invasion. It needs to be protected and restored, but the effects of environmental factors and propagule types on its restoration success are unclear. We examined the environmental niche of three propagule types (seedlings, corm shoots and plantlets) of Scirpus mariqueter under water level, salinity and nitrogen treatments in a greenhouse experiment. We found that water level was the most critical environmental factor limiting plant performance, followed by salinity. Nitrogen addition inhibited propagule growth in intermediate water level and salinity treatments. There were significant three-way interactions between water level, salinity, and nitrogen addition: Scirpus mariqueter performed best in treatments of low salinity + low to intermediate water levels + high nitrogen. Corm shoots outperformed plantlets and seedlings. Our results suggest that planting corm shoots under intermediate salinity and high water level conditions will enhance the restoration success of Scirpus mariqueter in the saltmarshes of the Yangtze River Estuary.