南京市土壤集合组成及其嵌套性分析

随着工业化和城市化的加速发展，土壤资源与土壤环境压力日益增加。近20a来，南京市城镇化发展迅速，而且城镇的发展正导致原来相对自然的大片土壤面积减少，深入研究南京市土壤组成以及嵌套性特征，有助于了解土壤类型的分布特征，正确估计城镇化的后果，在保护土壤资源以及土壤多样性方面具有一定的理论意义和现实意义。以南京市各乡镇等级单位的土壤集合为研究对象，对南京市的土壤组成及嵌套性进行了分析。结果显示，在南京市各乡镇等级单位中共有47个土种，其中优势土种6种，常见土种13种、稀有土种25种、濒危土种3种。土壤集合在组成上呈现出不完全嵌套格局，分布于土种数较少的乡镇等级单位中的土种多数也分布在土种数较多的乡镇等级单位中。土壤类型数（S）与面积（A）是幂函数关系，其最佳回归拟合方程为：S=0．7284A^0.5922。嵌套格局与南京市的土种面积、地形以及地理位置关系密切，面积大的乡镇等级单位有更多的土种主要原因是它们有更广阔的生境范围，具有更高的生境多样性（如水域、沼泽、地形地貌、丘陵等），随着面积的缩小，某些特定的生境类型随着逐渐丧失，与此相关的一些土种也随之消失，于是就产生了嵌套结构。

Composition and nested analysis of pedological assemblages in Nanjing

The impact of rapid industrialization and urbanization on soil resources and the environment has been increasing in the Yangtze delta area over the past 20 years. More and more natural soils have been occupied by urban uses in many cities like Nanjing and original soil distribution patterns have been changed greatly. Studying and analyzing soil composition and nestedness helps to understand the distribution of pedotaxa better, estimate the aftermath of urbanization more accurately, and indicate further theoretical and practical implications in protecting soil resources and pedodiversity. Soil composition and nestedness of 70 town level units in Nanjing were analyzed with a software tool called Nestedness Temperature Calculator (Version Nov 1998). Results show that in Nanjing there are 47 pedotaxa types grouped into four classes; superior, common, rare and endangered with 6, 13, 25 and 3 members respectively. Pedological assemblages show the existence of an incomplete nested pattern, in other words, most pedotaxa present in the less rich sites are also present in more rich sites. A power law fit is satisfactory for a pedotaxa(S)-area(A) relationship in Nanjing and is S=0.7284A 0.5922 . Thus, in Nanjing there exist taxa-area positive correlations. Area size, landform type, as well as geographical position are considered to be the main factors forming the nested pattern. The town level units with larger area have more pedotaxa types due to the wider habitat range and more habitat diversity (such as water or landform conditions). As the area reduces, some habitat types are gradually lost, and the related pedotaxa type decrease produces the observed nested pattern.