Dynamics of multiple metallic elements during foliar litter decomposition in an alpine forest river

Compared with previously reported data, we found that plant litter decomposes faster in river ecosystem than on forest floor in a comparable period, but the dynamics of metallic elements during litter decomposition in river are likely to share common patterns with the corresponding ones in decomposing litter on forest floor. Litter decomposition in terrestrial lotic ecosystem is one of the most important pathways for metallic elements cycling, while little information is currently available about the dynamics of metallic elements in the decomposing litter of lotic ecosystems. The concentrations and release rates of potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and aluminium (Al) were investigated in the decomposing foliar litter of four dominant species in an alpine forest river. Over a 1-year period of decomposition, K, Ca, and Mg were released from virtually all types of litter, whereas Na, Fe, Mn, Zn, Cu, and Al were released from willow litter but accumulated in azalea, cypress, and larch litters during litter decomposition. Litter species, decomposition period, and river water characteristics (e.g., temperature, pH, flow velocity, and nutrient availability) were significantly related to the dynamics of these metallic elements in decomposing litter. Our results suggested that the similarity between the dynamics of metallic elements in the decomposing litter of lotic ecosystems reported here and previously for forest floors indicates a general pattern for the cycling of metallic element across different ecosystem types, and the net accumulation patterns for elements such as Zn, Cu, and Al during litter decomposition suggested that some litter species may act as efficient "cleaner" for metal purification in future ecological engineering.