Dynamics of trace elements during litter decomposition in a temperate forest as a function of elevation and canopy coverage

Abstract

Litter plays a key role in maintaining the nutrient cycle of the forest ecosystem. The dynamics of litter trace elements (TEs) can influence litter decomposition and biogeochemical cycling across plant and soil systems. However, our understanding of the biogeochemical cycle of TEs during litter decomposition remains limited. We investigated litter production, the concentrations and fluxes of needle litter TEs over 1 year, and the accumulation and release patterns of TEs at different elevations and canopy coverage during litter decomposition over 3.9 years for the Qinghai spruce in the Qilian Mountains. The concentrations and fluxes of TEs in the needle litter decreased in the following order: Zn > Ni > Cr > Cu > Pb > Co > Cd > Ag. TEs concentrations increased with decomposition time at different elevations, and Co, Cr, Cu, Ni, Pb, and Cd accumulated the fastest at 2850 m. Zn and Ag accumulated the fastest at 3450 and 3050 m, respectively. The fastest accumulation trends were for Co, Cu, Ni, Pb, Zn, Ag, and Cd concentrations at low canopy coverage. Cr accumulated the fastest at middle canopy coverage. The concentrations of Co, Cu, Pb, Zn, Ag, and Cd followed the trend of enrichment–release–enrichment, while Ni and Cr concentrations followed the trends of release–enrichment and sustained enrichment, respectively. Our study is important for an improved understanding of the TE cycle during litter decomposition. It provides theoretical support for healthy soil management and element cycling in the forest of the Qilian Mountains.