Windows of opportunity for salt marsh establishment: the importance for salt marsh restoration in the Yangtze Estuary

Abstract

Abstract Restoration has been promoted as an important strategy to reverse the decline of salt marsh ecosystems. Physical and biological processes limiting the colonization of bare tidal flats by pioneer salt marsh species are commonly recognized. Recently, the window of opportunity (WoO) concept has been proposed as a framework to provide an explanation for the initial establishment of biogeomorphic ecosystems on tidal flats under high physical stress. Understanding the thresholds for early seedling establishment and colonization is critical for the successful restoration and management of this threatened ecosystem. In this study, we investigated the WoOs for the establishment and colonization of a Scirpus mariqueter salt marsh at a large‐scale restoration site in the Yangtze Estuary. A set of field monitoring and measurements were conducted to identify the potential physical and biological thresholds that could provide a mechanistic insight on the establishment and colonization of this pioneer marsh. The results showed that the successful colonization and expansion of the S. mariqueter marsh on the tidal flat required passing both physical and biological thresholds to open WoOs for establishment and colonization. The concurrence of WoOs, that is, propagule availability in the early growing season at a suitable tidal flat elevation with a benign sedimentary regime together with the removal of competition from invasive species, is presumed to be essential for the success of S. mariqueter marsh establishment and colonization. In applying such ecological insights, the seed‐sowing field experiment proved that by surpassing these thresholds, an S. mariqueter salt marsh can be successfully restored in a cost‐effective manner. We suggest that these WoO‐related establishment and colonization thresholds as well the cost‐effectiveness of using these WoOs should be considered in future large‐scale restorations of salt marshes.

Keywords

• establishment
• restoration
• salt marsh
• Scirpus mariqueter
• windows of opportunity
• Yangtze Estuary