Background Soil properties to a large degree showed the spatial self-correlation variation characteristics. Topography is usually an important source of soil variation. Quantitative analysis of spatial heterogeneity of soil and its correlation with topography is helpful for revealing the potential mechanism of soil variation.

Methods Referring to soil sampling scheme of CTFS, we collected 199 soil samples from a 4 hm² secondary Picea forest of Guandi Mountain and completed the soil properties determination. The horizontal and vertical space distribution characteristics of PH, organic matter, available nitrogen, phosphorus and potassium were analyzed using the classical statistical methods, spatial heterogeneity of soil properties at 0-10 cm layer and their distribution patterns were acquired through geo-statistics and ArcGIS interpolation, and the effects of terrain factors on spatial heterogeneity of soil properties were quantitatively assessed by RDA sorting and variance decomposition.

Results The coefficient of variation for the soil pH, organic matter, available nitrogen, available phosphorus and available potassium was 8.78%、48.38%、41.15%、58.36%、46.60%, respectively. The five factors showed the spatial self-correlation variation at 4.9-58.8 m scale range, and a moderate degree of self-correlation was evaluated for pH and available nitrogen but a strong degree of self-correlation was evaluated for organic matter, available phosphorus and available potassium. Organic matter, available nitrogen and available potassium showed analogical spatial plaque distribution pattern, that is, the contents of organic matter and available potassium were also high in the plaque where there was available nitrogen in high content, while the soil pH and available phosphorus showed an opposite distribution pattern. Among the terrain factors, elevation had the strongest effects on the soil pH, available nitrogen and phosphorus, soil pH and available phosphorus had positive correlation with elevation, and the elevation explained 40.43% and 28.81% of the spatial variability of soil pH and available phosphorus, respectively, but available nitrogen had negative correlation with elevation and the elevation explained 19.48% of the spatial variability of available nitrogen independently. Convexity had the strongest negative effects on available potassium and organic matter, and it explained 9.37% and 6.88% of the spatial variability of available potassium and organic matter.

Conclusions Soil properties showed structural heterogeneity in space and topography factors had important effects on the variation of soil factors. The experimental results can provide the basis for understanding the distribution and coexistence of tree species in North China.