Eco-geochemical process of characteristic forest fruit resources and its significance of quality improvement in Chengde City

The distribution of characteristic forest and fruit resources in Yanshan Mountain in the south of Chengde is obviously regional, with Xinglong-Xifengkou fault as the boundary, "Jingdong Chestnut" concentrated in gneiss area in the south, and "Xinglong Hawthorn" concentrated in dolomite area in the north, so it is of great significance to determine the main controlling factors for improving the quality of forest and fruit resources. From the perspective of geological formation and eco-geochemistry, this paper analyzes the element content and correlation of gneiss and dolomite formation, studies the characteristics of element migration and biological enrichment, and discusses the main factors affecting crop quality. The results show that:the gneiss formation is mainly composed of plagioclase, quartz and mica minerals, and the contents of Al₂O₃, Fe₂O₃, K₂O, TiO₂, P₂O₅, Mn, Cu, Zn, Ni and Co are obviously high.Correspondingly the dolomite formation is mainly composed of dolomite minerals with high contents of MgO and CaO. The mass transfer coefficient (τ) between bedrock and soil shows that Se, B, V, S, Mn and Mo are relatively enriched in gneiss formation, while Na₂O, P and Ni elements are relatively enriched in dolomite formation. The enrichment coefficient of chestnut is Cu > Zn > Mo > Ni > Mn > Ge > Fe, and that of hawthorn is Cu > Zn > Ni > Mn > Ge > Fe > Mo. Based on the ecological geological model of quality control of Chinese chestnut and hawthorn, the most suitable area for screening hawthorn and Chinese chestnut is 497.2 km² and 499.01 km² respectively. The research results can provide reference for the optimization of local agricultural industrial structure.