Spatial differentiation of metallic micronutrients in soil–plant systems along an altitudinal gradient in the Fanjing Mountain, Southwestern plateau of China

Metallic micronutrients (Cu, Fe, etc.) play a crucial role in plant growth, but limited research has explored the distribution patterns and determinants of these elements within the soil–plant system along elevation gradients in highland alpine forest ecosystems. In this study, we focused on Fanjing Mountain, a highland forest ecosystem in Southwest China, to examine the distribution and partitioning of metal micronutrients (Cu, Fe, Zn, Mo, Ni) within the soil–plant system along an altitudinal gradient, and to identify factors influencing micronutrient dynamics in plants across varying elevations. The results showed that the average contents of Cu, Fe, Zn, Mo, and Ni in soil (plant) were 24.64 (11.96), 28784.38 (1185.17), 659.57 (60.23), 0.97 (0.77), and 25.42 (5.41) mg/kg, respectively. Micronutrient elements exhibited varied trends along the altitudinal gradient; notably, Zn content in both soil and plants increased with elevation. The enrichment capacity of plant branches and leaves for metal micronutrients also shifted with altitude, with Cu and Mo showing significantly higher enrichment levels compared to other elements. Metal micronutrient content of plants was influenced by environmental factors such as soil properties and location, where the effect of soil environmental factors on plant micronutrient content decreases with increasing altitude. These findings enhance our understanding of the biogeochemical cycling of metal micronutrients in highland alpine forest ecosystems and provide valuable insights for improving forest soil quality and vegetation conservation.