Objective To better understand the characteristics of soil silicon morphology variation and its correlation with soil physi-chemical properties in Castanopsis fargesii stands at differentaltitudes in Guoyan Mountain for further illuminatingthe response mechanism of soil silicon morphology content to environmental changes in subtropical areas.

MethodsIn order to gather soil samples from various soil layers (0−20, 20−40, and 40−60 cm) at differentaltitudes in Guoyanshan Nature Reserve, standard plots were set up at 600, 700, 800, and 900 m, respectively. Different soil silicon forms were extracted and measured to examine the effects of environmental changes on soil silicon forms.

Results(1) Available silicon(258.26 mg·kg⁻¹), water-soluble silicon (155.69 mg·kg⁻¹), active silicon (388.97 mg·kg⁻¹) and amorphous silicon (1561.97 mg·kg⁻¹) in the high-altitidesoil weresignificantly higher than those in thelow altitudesoils with the data of 93.16, 78.38, 231.84, and 832.24 mg·kg⁻¹, respectively. The availablesilicon (227.53 mg·kg⁻¹) in deep soil layer (40−60 cm) was significantly higher than that in 0−20 cm (120.79 mg·kg⁻¹) and 20-40 cm (171.37 mg·kg⁻¹) soil layers. (2) The content of available silicon in soil was significantly positively correlated with the content of active silicon and water-soluble silicon. Active silicon was the most important direct contributing form to the increase of availablesilicon, andwater-soluble silicon was an important transitional form in the soil silicon transformation process.(3) Soil organic matter and soil pH had the most significant effects on the content of each soil silicon form, which explained the variations of14.1% and 9.2%, respectively. Soil organic matter was positively correlated with amorphous silicon and water-soluble silicon, and negatively correlated with soil active silicon and effective silicon, while soil pH was positively correlated with availablesilicon and active silicon, and negatively correlated with amorphous silicon.

Conclusion Variations on environment and soil physical and chemical properties caused by altitude can change the content of silicon in soil.This study offers a foundation for successful soil silicon use and soil silicon morphology control in natural Castanopsis fargesii forest, which is crucial scientific advice for the preservation of natural Castanopsis fargesii forest.