（1）样地调查以研究区选择坡型相似、林龄相近的油松、侧柏和刺槐人工林作

(1) In the sample site survey <br>, the Pinus tabulaeformis, Platycladus orientalis and Robinia pseudoacacia plantations with similar slope types and similar forest ages were selected as the target sample sites in the study area. The trees were planted on the excavation slope platform, the overall slope was about 30 degrees, and the average interval was 2.5 meters. Repeat sampling of the forest soil, estimate the macro-density of the composite soil according to the root volume ratio, and determine the soil physical and chemical properties.

(1) Survey<br>With the study area to select similar slope type, similar age oil pine, side cypress and hedgehog artificial forest as the target sample, the forest is planted on the excavation slope platform, the overall slope is about 30 degrees, the average spacing is 2.5 meters. Repeated sampling of forest soil, the macro density of composite soil is estimated according to the root volume ratio, and the physical and chemical properties of soil are determined.

(1) Sample plot investigation<br>In the study area, Pinus tabulaeformis, Platycladus orientalis and Robinia pseudoacacia plantations with similar slope types and similar forest ages were selected as the target plots. The trees were planted on the slope platform, with an overall slope of about 30 degrees and an average spacing of 2.5m. Based on the volume ratio of root system, the macro density of composite soil was estimated and the physical and chemical properties of soil were determined.<br>