Differences of Soil Physicochemical Properties and Undergrowth Vegetation Diversity of 100-Year-Old Chinese Fir Plantations in Different Terrain

We selected the 100-year-old Chinese fir plantation in Wangtai Town, Nanping City, Fujian Province as the research objects. We analyze the differences of soil physicochemical properties and understory vegetation diversity at 0–20, 20–40 cm and 40–60 cm of 4 terrains(southwest slope, northwest slope, corrie, valley), and variance analysis was used to analyze the influence of terrain factors on 2 kinds of indicators, and correlation analysis was used to analyze the internal relationship between 2 kinds of indicators. The results showed that in the same soil layer, the non capillary porosity, total phosphorus, available phosphorus and available potassium are significantly affected by terrain, total porosity and organic matter have no significant effect, and the non capillary porosity, organic matter, total nitrogen and available potassium were the highest in the southwest slope land, the available phosphorus was the highest in the corrie land, and the other physical and chemical properties such as total phosphorus were the highest in the valley land, and the soil physical and chemical properties in the northwest slope land was relatively low. In addition to bulk density, total phosphorus and total potassium, soil moisture content and other physical and chemical properties most showed a downward trend with the deepening of soil layer. The change in diversity index of shrub layer was more obvious than that of herb layer. Both showed the highest in the northwest slope, followed by the southwest slope and carrier, and the lowest in valley. Soil moisture content, capillary porosity, total phosphorus and available potassium are closely related to the diversity of vegetation under shrub and grass layer, and there is significant or extremely significant correlation. So, the physicochemical properties of soil and the diversity of vegetation are greatly affected by terrain.