Analysis of Tamarix chinensis Forest Characteristics, Salt Ion Distribution, and Non-Structural Carbohydrate Levels in the Yellow River Delta: A Spatial Study Based on Proximity to the Shoreline

The distribution of vegetation in coastal wetlands is significantly influenced by soil properties. However, the mechanisms of how soil characteristics impact the physiological processes of <i>Tamarix chinensis</i> forests remain underexplored. This study examined changes in the soil physicochemical properties and structural attributes of natural <i>T. chinensis</i> forests in the Yellow River Delta with increasing distance from the shoreline. <i>T. chinensis</i> trees were classified into healthy, intermediate, and dying categories based on growth potential, and dynamic changes in salt ions and non-structural carbohydrates (NSCs) were investigated. Results indicated that increasing distance from the shoreline corresponded to decreased soil salinity and pH, and increased soil moisture. <i>T. chinensis</i> mortality rate decreased, while tree height and ground diameter increased with distance. Soil salt content was positively correlated with <i>T. chinensis</i> mortality, but negatively correlated with tree height and ground diameter. Trees with lower growth potential had higher Na⁺ but lower K⁺ and K⁺/Na⁺ ratio. Soil salt content was positively correlated with root and stem Na⁺, while soil moisture was positively correlated with leaf NSCs. These findings suggest that soil salt content and moisture significantly influence <i>T. chinensis</i> ion absorption and NSC accumulation, with sodium toxicity being a key factor in the spatial distribution of <i>T. chinensis</i> forests.