Different Types of Planted Forest Accumulate Specific Heavy Metals in Western Beijing

Abstract

Biological enrichment is a promising strategy for mitigating heavy metal pollution; however, the characteristics of different tree species, their elevation-related heavy metal content, and their capacity to accumulate these metals remain unclear. Moreover, the factors influencing heavy metal pools require further investigation. In this study, we measured the concentrations of copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) in ground surface litter (GSL) and soil from four forest types (Pinus tabuliformis, Populus davidiana, Larix principis-rupprechtii, Betula platyphylla). The results showed that variations in growth rates among the four tree species at different elevations influenced the size of the heavy metal pool, suggesting that both tree species and elevation (temperature) play key roles in determining the storage, enrichment, and variability of heavy metal concentrations in forests. Populus davidiana showed the most significant enrichment for Cu and Zn, while Betula platyphylla exhibited the highest enrichment for Mn and Zn. Broadleaf species exhibited a greater capacity for heavy metal accumulation than coniferous species in Western Beijing. Principal component analysis revealed that Pinus tabuliformis, Larix principis-rupprechtii, and Betula platyphylla clustered closely in principal component space. Based on the accumulation characteristics of these four heavy metals across different tree species and elevations, specific tree species can be selected for heavy metal enrichment in various elevations or habitats. This research provide assistance for the remediation of heavy metal environment pollution restoration based on natural countermeasures.

Keywords: Bioconcentration factor; Elevation; Forest soil; Ground surface litter; Heavy metal elements; Principle component analysis (PCA).