Study on Soil Improvement Effect of Different Stand Types in Jiaodong Hilly Area

Take the bare land as a control, 4 forest types including 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 were selected in this research. Ten 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 4 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. 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. The best comprehensive improvement effect of 4 forest types is the mixed forest of R. pseudoacacia, P. tomentosa and Q. acutissima, followed by shelter forest of P. thunbergii, mixed forest of P. tabuliformis and Q. mongolica, and cash forest of C. mollissima is relatively poor. In order to reduce soil erosion in the research area, improve water storage capacity of soil and increase nutrient accumulation, it is necessary to choose the mixed planting of multiple tree species.