Effects of Vegetation Succession on Soil Fertility Within Farming-Plantation Ecotone in Ziwuling Mountains of the Loess Plateau in China

To further understand the relationship between vegetation succession and soil fertility within farming-plantation ecotone in Ziwuling Mountains of the Loess Plateau, nine kinds of widely distributed communities at different succession stages were selected, and the effects of vegetation succession on soil fertility were studied through the methods of comparing two hierarchical clustering (similarity index: ) and other multivariate analysis. The results showed that: (i) the similarity in clustering pattern of nine communities which classified by plant species and soil nutrients respectively showed a trend of overall plant-soil 0–10 cm>overall plant-soil 10–20 cm>overall plant-soil 20–40 cm, and for the top soil, it showed a trend of grass-soil 0–10 cm>shrub-soil 0–10 cm>tree-soil 0–10 cm; (ii) soil fertility increased during the succession process from abandoned land to forest community, and the soil fertility of forest community showed an increased order of coniferous forest →mixed forest →broadleaf forest; (iii) during the process of vegetation succession, the variation of topsoil fertility was higher than that of the subsurface soil (coefficient of variation: CV0–10 cm > CV10–20 cm > CV20–40 cm), and when the succession developed into the stages of shrub and forest communities, the top soil fertility had been improved significantly; and (iv) for the subsurface soil of the communities at the advanced succession stages, the soil fertility also increased to some extent. Our results suggested that the method of comparing two hierarchical clustering reflected the similarity level of different cluster patterns, therefore, it was helpful to study the relationship between vegetation succession and soil fertility. There was a corresponding relationship between the change process of soil fertility from the top soil to subsurface soil and the process of vegetation succession from the early stages to the advanced stage. The differentiations of soil fertility in vertical space and horizontal space were both caused by vegetation succession, which was significant for both the shrub and forest communities. The improved level of forest soil fertility was related to forest vegetation types and the improved fertility level of broad-leaved forest-soil community was higher than that of the coniferous forest soil. In the practice on soil fertility ecological restoration of the loess plateau, it is important to carry out reasonably artificial forestation so as to enhance the restoration and improvement of soil fertility.