The Dynamic Features of Cadmium and Chromium in Foliar Litter of Abies faxoniana during Decomposition in the Alpine Forest of Western Sichuan

In order to investigate the releases of heavy metals from plant litter in alpine forest, a litterbag experiment was conducted in a fir primeval forest of western Sichuan from November 2012 to October 2014. The concentrations and decomposition rates of cadmium and chromium in foliar litter of Abies faxoniana, which is the constructive species in this area, were observed to find out about the snow formation stages, snow cover stages and snow melt stages and the growing seasons in the two years. The results showed that the initial concentrations of cadmium and chromium in foliar litter of Abies faxoniana were 59.7±5.7 μg/kg and 3.81±0.26 mg/kg, respectively, whereas the concentrations increased 3.0 times and 87.0%, respectively, after the two years of decomposition. The concentrations of both cadmium and chromium in foliar litter of Abies faxoniana increased to reasonable extents during the snow formation stages and growing seasons, implying that a certain amount of cadmium and chromium were inputted to soil surface through atmospheric wet deposition. Moreover, the concentrations of cadmium and chromium significantly declined during the snow cover and snow melt stages, suggesting that the heterogeneities of hydrothermal conditions that were induced by the formation and melt of snow cover in various stages promoted the releases of cadmium and chromium in foliar litter in alpine forest of western Sichuan.