柴达木盆地盐碱地土壤质量评价及障碍因子特征

Soil Quality Assessment and Obstacle Factor Characteristics of Saline-Alkali Soils in the Qaidam Basin

摘要: 本研究以青海省都兰县、乌兰县、德令哈市轻度、中度、重度、极重度4类盐碱地为对象，分层采集0~10、10~20、20~30 cm土壤样品，测定pH、有机碳、全氮、全磷、全钾及交换性钙、镁、钠、钾9项土壤化学指标；运用主成分分析构建土壤肥力综合评价模型，结合Norm值与相关性分析筛选土壤质量评价最小数据集(MDS)，引入障碍度模型定量诊断不同盐碱梯度、不同土层的土壤障碍因子。结果表明：① 土壤化学性质存在显著盐碱梯度与垂直剖面分异；轻度、重度、极重度盐碱地有机碳呈表层富集，中度盐碱有机碳集中于10~20 cm土层；轻度、中度盐碱地全氮、全磷呈表层富集，重度、极重度盐碱地全氮、全磷、全钾整体表现底聚特征；交换性盐基离子受阳离子交换、水分运移共同调控，重度盐碱地交换性盐基总量整体最高。② 土壤肥力综合得分随盐碱化加剧整体下降，轻度盐碱0~10 cm土层肥力最优，重度、极重度盐碱地各土层肥力得分均为负值；低盐碱土壤肥力表层富集规律显著，高盐碱梯度下肥力垂直分布格局反转。③ 基于主成分、Norm值与相关性筛选，确定由全磷、pH、交换性钠组成最小数据集，可解释80.49%土壤指标变异信息。④ 土壤障碍因子随盐碱程度、土层深度梯度更替：轻度盐碱地表层以交换性钠为核心障碍，中底层pH限制突出；中度、重度盐碱全域土层首要障碍为全磷，且重度盐碱全磷障碍度随土层加深持续升高；极重度盐碱0~20 cm土层以全磷为主要障碍，20~30 cm底层交换性钠成为首要限制因子。研究明确了柴达木盆地不同类型盐碱土肥力差异与分层障碍特征，可为区域盐碱地分层、分级差异化生态修复与培肥改良提供理论支撑。

Abstract: This study selected four grades of saline-alkali soils (light, moderate, heavy and extreme salinization) distributed in Dulan County, Wulan County and Delingha City of Qinghai Province as research subjects. Soil samples were collected from three vertical layers of 0~10 cm, 10~20 cm and 20~30 cm, and nine soil chemical indicators were measured, including pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), as well as exchangeable calcium (Ca²⁺), magnesium (Mg²⁺), sodium (Na⁺) and potassium (K⁺). Principal component analysis (PCA) was adopted to establish a comprehensive assessment model for soil fertility. Combined with Norm value calculation and Pearson correlation analysis, the minimum data set (MDS) for soil quality evaluation was screened. Furthermore, an obstacle degree model was employed to quantitatively identify the dominant Obstacle factors across varying salinization gradients and soil depths. The results revealed four key findings: ① Soil chemical properties exhibited pronounced horizontal differentiation along salinization gradients and vertical stratification within soil profiles. Soil organic carbon accumulated predominantly in topsoil under light, heavy and extreme salinization, while its maximum concentration occurred at the 10~20 cm layer in moderately saline-alkali soils. Total nitrogen and total phosphorus were enriched in surface layers of lightly and moderately saline-alkali soils, whereas TN, TP and TK generally accumulated in subsoil layers under heavy and extreme salinization. Co-regulated by cation exchange processes and water-salt transport, the total exchangeable base (TEB) content reached the highest level in heavily saline-alkali soils. ② The integrated soil fertility score declined progressively with increasing salinization intensity. The 0~10 cm topsoil of lightly saline-alkali plots possessed the highest fertility value, and all soil layers under heavy and extreme salinization yielded negative comprehensive fertility scores. Surface accumulation of fertility was distinct under low salinization stress, whereas the vertical distribution pattern of soil fertility reversed when salinization intensity reached high levels. ③ A MDS consisting of total phosphorus, soil pH and exchangeable sodium was extracted via PCA, Norm value ranking and correlation screening, which could account for 80.49% of the total variance contained in all measured soil indicators. ④ Soil Obstacle factors shifted systematically with salinization severity and soil depth. Exchangeable sodium constituted the dominant obstacle in the topsoil of lightly saline-alkali land, while pH served as the major constraint in middle and deep layers. Total phosphorus was the primary Obstacle factor throughout all soil layers of moderately and heavily saline-alkali soils, and its obstacle degree increased continuously with soil depth in heavily saline-alkali profiles. For extremely saline-alkali soils, total phosphorus remained the dominant constraint within the 0~20 cm layer, while exchangeable sodium replaced TP as the primary Obstacle factor in the 20~30 cm subsoil. This study quantitatively characterizes fertility disparities and stratified obstacle patterns of diverse saline-alkali soils in the Qaidam Basin. The outcomes can provide theoretical foundations for stratified and classified differentiated ecological restoration and fertility amelioration of regional saline-alkali land resources.