南京附近低山丘陵区林业用地土壤分类的数值评定

<正> 引 言 土壤分类单元间亲疏关系或从属关系的数值评定,即土壤的数值分类,是以土壤分类指标(主要是属性指标)、的数值化为基础,通过对各单个土体(pedon)调查资料和数据的获得、整理和运算,形成一种以数值为依据的土壤分类体制。土壤的数值分类系统可以独立应用,便于用电子计算机贮存信息、制图和鉴定待测土壤;但在目前的发展水平上更多地是用数值分类方法来论证或评定现有的直观土壤分类系统,把主观比土的结果置于数值运算的基础上进行检验。从本世纪六十年代起,国外就有一些土壤学者开展土壤数值分类的研究工作;1978年中国土壤学会举行全国土壤分类会议以来,这种数值方法在我国也逐渐有了可喜的发展。本文是同时运用以主分量分析为主、结合聚类和回归分析的几种多元分析方法,探讨南京附近低山丘陵区林业用地土壤分类和生产力评价问题。这项工作的目的,一方面是探索综合应用这些方法的可行性及其实际效果,另一方面是把现有的江苏南部低山丘陵区土壤分类方案,置于这些数值方法综合应用的基础上作一次检验,以进一步论证其合理性。 这里所说的现有分类方案,是指我们在1978年拟订的一个,具有7个土类24个土型,主要是根据母质类型和土壤属性,适当参照我国现行土壤分类规范而制定(表1),并且作过一些土壤生产力评价的尝试。这个以直观对比为基础的分类方案,是为林业利用目的而制订的,但并不背离现代土壤发生学的原则。下文通过主分量分析而形成的排序作进一步论证。

NUMERICAL APPRAISEMENT ON SOIL CLASSIFICATION FOR SILVICULTURE USE IN THE LOW MOUNTAIN AND HILL AREA AROUND NANJING

The present article deals with the numerical appraisement on soil classification for silviculture use and the assessment of forest productivity on those soils by means of taking the principal component analysis as a main program associated with clustering and regression to examine the rationality of the current taxonomy of soils in the low mountain and hill area around Nanjing, and to test simultaneously the effectiveness of the above-mentioned numerical method per se. It turned out that by using five soil attributes, i. e., the total depth of soil, the texture, the stone content, the pH value and the effervescent effect in subsoil, the principal component analysis applied to the data collected from 70 sites can mainly distinguish most types of soils which have been classified into the current taxonomic system according to their parent materials and soil properties. Clustering and regression carried out on the very basis further proved that the soil types based on the first two principal components were related to a certain extent to their productivity for forest.The result of principal component analysis showed that there are 3 ecological sequences of soil in the area according to their parent materials as well as soil reaction and the basisols were also confirmed statistically. The further clustering indicated that the shallow soils of yellow-brown loam and acidic stony ground scattered on to the coordinate plane of the first two components were of crossed distribution, so that it is reasonable to put them into one group as rankers; and the shallow soil of neutral stony ground ought to be allocated to the shallow type of limestone soils. The regression of tree growth to the principal components of soil illustrated that the productivity of a certain type of soil might extend across two grades, and the critical value for the assessment of soil productivity also varied with different ecological sequences of soil.