Study on the Ecological Water Demand of Seepweed (Suaeda salsa) Communities in the New Wetland of the Yellow River Delta

River deltas, located in the interacting zones of terrestrial and marine environments, provide important ecological services and economic values, which are characterized by hydrologic regimes and salinity gradients. The Yellow River Delta (YRD), located in the northern China, is one of the most complete and youngest estuarine wetlands. However, the YRD are threatened in recent decades by irrational human interventions and regional climate change. Seepweed (Suaeda salsa) is an important pioneer species, playing a leading role in the succession process of estuary ecosystems. In this study, we firstly investigated the distribution of Seepweed by employing remote sensing images and a field survey. The Seepweed community was then categorized to be Concomitant Community of Seepweed (CCS) and Dominant Community of Seepweed (DCS), according to soil salinity based on the ecological threshold theory. Ecological water demand of Seepweed communities was accordingly found to consist of two parts in terms of its functions, that is, improving suitable habitats and maintaining physiological functions. The results indicate that: (i) the distribution areas of the CCS and the DCS are about 40.933 and 53.407 km(2); (ii) the ecological water demands of the CCS and the DCS range 1.064 x10(8) - 1.203 x 10(8) and 1.524 x 10(8) - 1.674 x 10(8) m(3), respectively; and (iii) the ecological water supplement of 2.026 x 108m(3) should be supplied for the Seepweed Communities, especially during the initial stage between April to June. This study could be used to provide a sound basis for estuarine wetland ecosystem protection in the YRD.