基于聚类分析的土壤盐渍剖面特征及其空间分布研究

通过对黄河三角洲地区典型地块土壤盐渍剖面的聚类分析,研究并总结该地区不同盐分剖面类型土壤含盐量在水平方向以及垂直方向的分布特征和规律,运用该规律对各盐渍剖面类型的空间分布进行了探讨。结果表明:研究区土壤盐分剖面可以明显分为表聚型、底聚型和平均型3类,按照垂直分布特征可将0～180cm土体划分为0～20cm、20～80cm、80～120cm和120～180cm四个层次;研究区土壤含盐量在垂直方向和水平方向上变异较强,总体上盐分分布具有一定的表聚性,且各土层含盐量的规律性可以作为判断土壤盐分剖面类型的依据;受结构性因素和随机性因素的共同影响,各土层含盐量均表现为中等的空间自相关性和相同的空间自相关变化尺度。Kriging插值与空间分析结果表明,微地形和气候条件是影响表层土壤盐分空间分布的主要因素,地下水性质主导深层土壤盐分的空间分布;表聚型盐分剖面是研究区最主要的剖面类型,其次分别为底聚型和均匀型;不同盐分剖面类型的空间分布反映了植被类型和土地利用方式的差异,人为农业措施是形成底聚型与平均型盐分剖面的最直接因素。该研究结果为黄河三角洲地区盐渍土地的分区、改良、管理以及合理利用提供了理论基础和实践依据。

PROFILE CHARACTERISTICS AND SPATIAL DISTRIBUTION OF SOIL SALINITY BASED ON HIERARCHICAL CLUSTER ANALYSIS

Characteristics and regularity of spatial, horizontal and vertical, distribution of soil salinity in different salinity profile types were studied and summarized through application of hierarchical cluster analysis of typical soil salinity profiles in the Yellow River Delta, and these regularities were then used to explore spatial distribution of different salinity profile types. Results show that soil salinity profiles could be obviously classified into normal, inverted and even, and a soil profile of 180 cm in depth could be divided into four layers, 0 - 20 cm, 20 - 80 cm, 80 - 120 cm and 120 - 180 cm in terms of the vertical distribution characteristics. Soil salinity exhibited strong variation in spatial distribution, both horizontal and vertical, salt accumulation at the surface soil layer was generally significant, and the regularity of soil salinity at different layers could serve as a reference for the classification of salinity profile types. Owing to compound impact of structural and stochastic factors, soil salinity at these layers all exhibited moderate spatial variation and identical spatial autocorrelation scale. The results of Kriging interpolation and spatial analysis indicated that the spatial distribution of soil salinity in surface layer was chiefly dominated by micro-topography and climate conditions, while the spatial distribution of soil salinity at deeper layers was mainly controlled by groundwater properties. The study area was predominated with inverted salinity profile types and, followed by normal and even ones, respectively. The distribution patterns of salinity profile types reflected variation of vegetation types and land use patterns to some extent, and human agricultural activity was the crucial reason for the formation of normal and even salinity profile types. The research results can serve as a theoretical and practical basis for zoning, amelioration, management and rational utilization of saline soils in the Yellow River Delta.