Spatial Distribution Characteristics of Soil Nutrients and the Correlation with Topographic Factors in Pinus massoniana Plantation

In the pilot area of sustainable management of Pinus massoniana plantation in Pingba District, Guizhou Province, soil samples were collected in a standard grid of 10 m×10 m to analyze the spatial variability of 7 soil nutrient indicators (organic matter, total nitrogen, available nitrogen, total potassium, available potassium, total phosphorus, available phosphorus) and also discussed the correlation between soil nutrients and topographic factors. The results showed that seven soil nutrient indexes exhibited medium spatial variability, and the variation coefficients from large to small were total potassium > total phosphorus > organic matter > available potassium > available phosphorus > available nitrogen > total nitrogen. Organic matter, total potassium, total phosphorus and available nitrogen showed a relatively strong spatial autocorrelation, while total nitrogen, available potassium and available phosphorus showed a moderate degree of spatial autocorrelation. The spatial distribution of available phosphorus and total phosphorus had a relatively good continuity, followed by total nitrogen, total potassium and available potassium, organic matter and available nitrogen had a poor spatial continuity with higher degree of fragmentation. The elevation, slope, aspect, topographic relief and curvature were the main factors affecting the spatial distribution of soil nutrients.