Water-salt interactions factors and vegetation effects in the groundwater ecosystem in Yellow River Delta

To understand the function of the groundwater ecosystem in Yellow River Delta, some key aspects in the evaluation of terrestrial vegetation-groundwater interactions are examined using an integrated approach combining statistical, geostatistical, isotope, and 3S (GPS, GIS, RS) techniques. The examination focuses on the role of water-salt interactions and vegetation effects in the groundwater ecosystem. The results show that the shallow groundwater zone (1.0-3.0 m) in the study area is the main water source, indicating the crucial role of groundwater in the ecosystem. Both chloride ion concentration c(Cl^-) and the total dissolved solids content (c(TDS))) in phreatic water present the characteristic of directional variability in space, or increasing along the direction of groundwater flow. The spatial distributions of c(Cl^-) and c(TDS) are highly consistent with each other (R=0.999), showing that the quality of shallow groundwater is dominated by Cl^-. The logistic relationship between Normalized Difference Vegetation Index (I_NDVI) and c(Cl^-) in phreatic water reveals that the later is a curial control factor of groundwater in relation to the vegetation cover on land surface. It is therefore suggested that special attentions should be paid on the close relationship between vegetation and c(Cl^-) in phreatic water in development of the Yellow River Delta High-efficiency Ecological Economic Zone, and the effective artificial regulation measures should be adopted to protect the ecosystem.