黄河口湿地柽柳灌丛土壤盐渍化特征

为探究黄河三角洲湿地柽柳灌丛下土壤的盐渍化特征,在黄河三角洲国家级自然保护区(37°35''-12''N,118°33''-119°20''E)黄河入海口附近,根据长势基本一致的原则分别在碱蓬群落、柽柳群落和芦苇群落各选3株柽柳,采集柽柳灌丛下土壤样品,分析土壤盐分和盐碱化参数的空间分布以及距基茎不同距离处研究对象(土壤总盐(TS)、电导率(EC)、pH、交换性钠百分率(ESP))和环境因子(Na⁺、K⁺、Ca²⁺、Mg²⁺、Cl^-、HCO₃^-、SO^2-₄)之间的关系。结果表明：(1)研究区土壤为弱碱化盐土,离子含量由高到低依次为Cl^->Na⁺>SO^2-₄ >Ca²⁺>Mg²⁺>HCO^-₃>K⁺。除pH在土壤表层数值最低外,表层土壤TS、EC、ESP和盐分离子大于深层土壤,显示表聚性。(2)土壤盐分和盐碱化参数空间分布总体为：在柽柳基茎周围形成"盐谷"、"碱谷"效应, Na⁺、Mg²⁺、Cl^-表现为"盐谷",K⁺ 、SO^2-₄ 、Ca²⁺ 表现为"盐岛"。(3)在整个土壤剖面中,与TS、EC相关性最强的阴阳离子为Mg²⁺、Cl^-,从灌丛中心到灌丛间裸地Ca²⁺、SO^2-₄与TS、EC的相关性逐渐减弱,Mg²⁺、Cl^-与TS、EC的相关性逐渐增强。Ca²⁺和SO^2-₄与pH表现为较强的负相关性;与ESP相关性最强的阴离子为HCO^-₃,与之相关性最强的阳离子为Na⁺和K⁺,并且Na⁺和K⁺与ESP的相关性表现出从灌丛中心向外逐渐增强。(4)土壤盐渍化主要受控于Na⁺,从灌丛下到灌丛间裸地Cl^-对盐渍化程度的影响逐渐增加,SO^2-₄的影响逐渐降低。

Soil salinization characteristics under the crown of Tamarix chinensis in the wetland of the Yellow River Estuary

Halophytes play a critical role in the revolution of estuarine wetlands. Tamarix chinensis is a typical halophyte with salt resistance and barren tolerance. To explore the influence of Tamarix chinensis on salinization, A survey plot was set at the estuary of the Yellow River in the National Nature Reserve (37°35''- 38°12''N, 118°33''- 119°20''E), which covered 3 vegetation communities:Suaeda salsa (L.) Pall community, Tamarix chinensis community and Phragmites communis community. In each community, 3 sample Tamarix chinensis shrubs with similar age, height and crown width were chosen, 16 soil profiles were evenly arranged in the four directions of East, West, North and south, under each sample Tamarix chinensis crown. 5 soil profiles in each direction were 0.5, 1.0, 1.5, 2 and 2.5 m away from Tamarix chinensis basal stem respectively. In addition, one more soil profile was set next to basal stem lying at the center of the shrub. At each soil profile, soil samples are collected in layers according to the depth of 0-5, 5-10, 10-20, 20-30 and 30-50 cm. Total salinity (TS), electrical conductivity (EC), hydrogen ion concentration (pH), exchangeable sodium percentage (ESP), Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, HCO^-₃ and SO^2-₄ were tested and analyzed in laboratory. One-way ANOVA and multiple comparison (LSD) were applied to analyze soil salt content and salinization parameters between different layers. Kriging interpolation method was applied to analyze the salt distribution characteristics of soil profile. The results show that:(1) the soil in the study area was weakly alkaline saline soil, and the order of ion content from high to low was Cl^- > Na⁺> SO^2-₄ > Ca²⁺> Mg²⁺ > HCO^-₃ > K⁺. TS, EC, ESP and salt ions in the surface layer were greater than those in the deep layers, with the exception pH, which was the lowest in the surface layer, indicating surface aggregation. (2) The spatial distribution of soil salinity and salinization parameters is as follows:the of "Salt Valley" and "Alkali Valley" effects formed around the Tamarix basal stem, Na⁺, Mg²⁺, Cl ^- formed "Salt Valley", and K⁺, SO^2-₄, Ca²⁺ formed "Salt Island". (3) Taking all the soil profiles as a whole, the anion and cation with the strongest correlation with TS and EC were Cl^- and Mg²⁺, respectively. The correlation between Ca²⁺, SO^2-₄ and TS and EC from shrub center to outside edge of the shrub was gradually weakened, and the correlation between Mg²⁺, Cl^- and TS and EC enhanced gradually. Ca²⁺ and SO^2-₄ showed strongly negative correlation with pH. Of all the anions, HCO₃-expressed very significant correlation with ESP. Similarly, Na⁺ and K⁺ were the two anions expressing very significant correlation were Na⁺ and K⁺. Furthermore, the correlation between Na⁺ and K⁺ and ESP increased gradually from shrub center to outside. (4) Soil salinization was mainly controlled by Na⁺, the influence of Cl^- on the degree of salinization gradually increased and the influence of SO^2-₄ gradually decreased from shrub center to outside.