Ecological Restoration of Degraded Supratidal Wetland Based on Microtopography Modification: a Case Study in the Yellow River Delta

In the past two decades, the supratidal wetland in the Yellow River Delta experienced severe saline-alkalization and vegetation degradation. Restoration with enclosure-freshwater release mode has prevailed since 2002. This method presented some positive effects, but need a massive freshwater supply. Furthermore, the subsequent formed single Phragmites australis vegetation weakened the bird habitation function. In this study, we developed another restoration mode based on microtopography modification. The core idea of the mode is to enhance micro-habitat heterogeneity thus improve the water resource temporal-spatial distribution and shape more niches. An ecological restoration program was designed and implemented since May, 2015. The monitoring data from July, 2015 to December 2017 showed that, with no extra artificially drained freshwater released, the soil salinity decreased by 15.4% to 30.8%. The area of bare land decreased while that vegetation and water surface increased, resulting in relative even land cover composition, habitat heterogeneity increased and thus the bird biodiversity improved. This mode is more ecological and water cost-effective and is suitable to restore the degraded saline-alkalized supratidal wetlands. However, long-term comprehensive monitoring is essential to evaluate the restoration effect. Many detailed parameters for topography modification need further optimized.