Soil Physical and Chemical Properties of Pure Pinus massoniana and Its Mixed Forests in Different Ages in Southern Guangxi

According to different slope positions (upper, middle and lower) , we set each forest type with a plot with size of 20 m x 20 m. In each plot, we selected three points on the diagonal, excavated the soil profile by 0 - 20, 20 - 40, and 40 - 60 cm. According to Fig. 3, the soil porosity of the soil layer (0-20 cm) and the bottom layer (40 - 60 cm) of each forest was greater than that of the middle layer (20 - 40 cm). According to preliminary analysis, the mature forest of 59 year-old P. massoniana is rarely influenced by humans, and has a thick humus layer, and this forest has a large degree of canopy closure and less grass under the forest, which may be the main reason for its low soil pH. 3.2.2Organic matter content. [...]the differences in soil chemical properties between the P. massoniana pure forests and mixed forests need further study, so as to provide a scientific basis for accurately assessing the effects of P. massoniana mixed plantation on the soil fertility.