Abstract:

As the basic unit of soil, the formation and stability of soil aggregates are closely related to soil organic carbon (SOC) content. Previous studies have mainly focused on the spatial variation characteristics and driving factors of a single soil aggregate or organic carbon. Few studies have investigated the spatial variation characteristics of all soil aggregate components and their associated organic carbon and analyzed the main driving factors. Therefore, in this study, the Huangshui River Basin in the northeastern part of the Tibetan Plateau was selected as the study area, and 84 arable land sample sites were established. Soil samples were collected from the 0‒20 cm and 20‒40 cm soil horizons to determine arable land soil organic carbon, soil aggregate fractions, and their related organic carbon. The half-variance function, kriging interpolation, and bias-variance function were used to integrate the soil physicochemical and geographic environmental factors. The spatial variation characteristics were analyzed using the half-variance function, Kriging interpolation, and partial least squares structural equation model, and the main controlling factors affecting the spatial distribution characteristics were identified and evaluated. The results of the study showed that 1) soil aggregates in the watershed showed moderate variability, whereas soil organic carbon showed high variability. 2) Geostatistical analyses showed that as the particle size of aggregates decreased (from macro-aggregates and micro-aggregates to powdery and sticky grains), the abutment values of soil aggregate fractions and the organic carbon within them decreased, and spatial autocorrelation weakened. 3) The kriging interpolation results indicated that the spatial distribution patterns of soil aggregate fractions and organic carbon were similar, generally decreasing from the northwest to the southeast region. 4) Combined with Spearman’s correlation analysis and partial least squares structural equation model, we found that soil and topographic factors are the most important direct and indirect driving factors for the spatial variability of soil aggregate fractions and organic carbon in cultivated land in the Huangshui Basin. Among them, soil texture was the most important control factor affecting the spatial variability of soil aggregates and their organic carbon, and topographic factors had the most important indirect effect on the organic carbon of aggregates through soil factors, which weakened with the increasing soil depth. Therefore, the study of Huangshui River Basin cultivated land in the soil agglomerates and their organic carbon interaction mechanism on the basis of the analysis of their spatial heterogeneity and its driving factors, alpine agriculture, and animal husbandry areas to prevent soil degradation, optimize the land management and maintenance of arable land productivity, regional ecological and environmental effects of the assessment and management to provide a certain theoretical basis.

Key words: Huangshui River, soil aggregates, organic carbon, spatial variability, influencing factor

摘要：

土壤团聚体作为土壤的基本单元，其形成和稳定与土壤有机碳密切相关。以青藏高原东北部的湟水河流域为研究区域，布设84个耕地样点，采集0－20 cm和20－40 cm土层的土样进行耕地土壤有机碳、土壤团聚体组分及其内相关有机碳的测定，综合土壤理化因素及地理环境因子的半方差函数、克里金插值和偏最小二乘结构方程模型分析其空间变化特征，识别影响其空间分布特征的主控因子并进行评价。 结果表明：1）该流域内土壤团聚体表现出中等程度的变异性，土壤有机碳表现出较高的变异性；2）地统计学分析表明，随团聚体粒径变小（由大团聚体、微团聚体变为粉黏粒），土壤团聚体组分及其内有机碳的基台值相应变小，空间自相关性相应变弱；3）克里金插值结果表明，土壤团聚体组分及其内有机碳的空间分布格局大致相似，总体从西北往东南部递减；4）结合Spearman’s相关性分析和偏最小二乘结构方程模型，发现土壤和地形因素是湟水流域耕地土壤团聚体组分及其有机碳空间变异最重要的直接和间接驱动因素。其中，土壤质地是影响土壤团聚体及其有机碳空间变异的最重要控制因素，地形因子通过土壤因子对团聚体有机碳具有最主要的间接效应，这种影响随着土壤深度的增加而减弱。在研究湟水河流域耕地土壤团聚体及其有机碳相互作用机制的基础上，分析它们的空间异质性及其驱动因素，可为高寒农牧区防止土壤退化、维持耕地生产力以及对区域生态环境效应评估与管理提供一定的理论依据。

关键词: 湟水河, 土壤团聚体, 有机碳, 空间变异, 影响因素