Regional differences in soil nutrient content along the forest edge in the northern slope of Tianshan Mountains

In this study, field investigation and laboratory analyse were carried out to gain a comprehensive insight into five kinds of soil nutrients (organic matter, available nitrogen, available phosphorus, available potassium and total salt) in three sections of the northern slope of Tianshan Mountains - the Zhaosu-Tekesi, Xinyuan-Bayinbuluke and Balikun-Yiwu sections. Multivariate statistical analysis method was used to study the characteristics of nutrient distribution in different soil profile layer (0~5 cm, 5~20 cm, 20~40 cm) in different sections of the northern slope of Tianshan Mountains. According to the standard of the Second National Soil Survey, variational characteristics of fertility and nutrient contents of different soil profiles in the sections were analyzed. Also variations in soil nutrient contents were clarified. Furthermore, quantitative comparison of nutrient contents among different sections was performed. The results showed that soil samples collected from the western sections (Zhaosu-Tekesi and Xinyuan-Bayinbuluke) had much higher nutrient contents than those from the eastern section (Balikun-Yiwu) of the northern slope of Tianshan Mountains. There were obvious differences in contents of organic matter, available nitrogen, available phosphorus and available potassium in the soil layers among different depths in the three sections. The average contents of organic matter, available nitrogen, available phosphorus and available potassium in the 0~5 cm soil layer were higher than those in the 5~20 cm and 20~40 cm soil layers. Also these variables were higher in the 5~20 cm soil profile layer than in the 20~40 cm soil profile layer. However, total soil salt content was not significantly different vertically across the soil profile. Based on the Second National Soil Survey standard, soils on the northern slope of Tianshan Mountains were relatively fertile. While changes in the amounts of soil nutrient contents in the 0~5 cm, 5~20 cm and 20~40 cm soil layers in Zhaosu-Tekesi and Xinyuan-Bayinbuluke sections followed a certain regular pattern, which in Balikun-Yiwu section was irregular. In most part of the western part of the northern slope (Zhaosu-Tekesi, Xinyuan-Bayinbuluke) is large summer pastures with various vegetations and hgiher vegetation coverage, where soils is fertile. It was recommend to protect the soils from overgrazing and random perturbations in order to avoid soil erosion. It was also critical to ban setting up of exploration platforms in larger slope areas. Also the low vegetation cover and gravel soil in the east part of the northern slope (Balikun-Yiwu) induced lower soil nutrient content comparing to the west part. It was therefore important to maintain original habitats and avoid anthropogenic disturbances that could induce habitat degradation.