Study on soil improvement effect of different stand types in Jiaodong hilly area

In order to explore the effects of different forest types on soil physical properties and soil nutrients in the hilly area of Jiao dong Peninsula, and provide a basis for tree species selection and planting management for soil and water conservation construction in this area. Take the bare land as a control, four forest types were selected in this research, mixed forest of Robinia pseudoacacia, Populus tomentosa and Quercus acutissima; mixed forest of Pinus tabuliformis and Quercus mongolica; cash forest of Castanea mollissima; shelter forest of Pinus thunbergii. 10 soil physical indexes such as soil bulk density, porosity and water storage capacity, 8 nutrient indexes such as soil organic carbon, total nitrogen, total phosphorus and available nutrients were measured and analyzed. Comprehensive evaluation of soil improvement effects of different forest types by principal component analysis and fuzzy mathematics membership function method. The results show that: (1) The four forest types have improvement effects on soil physical and chemical characteristics, such as reducing bulk density, increasing water storage capacity of soil, and improving the nuteient content of soil. (2) The improvement effect of different forest types on 0～20cm soil layer was better than that of 20～40cm soil layer, and the soil improvement effect of broad-leaved mixed forest was better than that of pure forest. (3) The best comprehensive improvement effect of the four forest types is the mixed forest of Robinia pseudoacacia, Populus tomentosa and Quercus acutissima, followed by shelter forest of Pinus thunbergii, mixed forest of Pinus tabuliformis and Quercus mongolica, and cash forest of Castanea mollissima is relatively poor. In order to reduce water and soil loss in the research area, improve water storage capacity of soil and increase nutrient accumulation, it is necessary to choose the mixed planting method of multi-tree species to improve the improvement effect of soil.