Effects of nitrogen deposition on early decomposition of three tundra litter types in Changbai Mountains

Rhododendron aureum litter, Deyeuxia angustifolia litter, and their mixture were selected as three tundra litter types from the Changbai Mountains. The effects of different nitrogen deposition on early-stage litter decomposition were studied in an artificial climate chamber. Results showed that: (1) D.angustifolia litter was of high quality and decomposed easily, R. aureum litter was of low quality and decomposed poorly, while the mixed litter showed moderate decomposition, with synergistic promotion of non-additive effects in the decomposition process; (2) Increased nitrogen deposition promoted decomposition of Rhododendron aureum and Deyeuxia angustifolia litter significantly, but the decomposition effect of mixed litter was not obvious; (3) At the early stage of decomposition, the three types of litter were all in the releasing state of total carbon and total phosphorus, and the lignin presented an enriched state; the total nitrogen and cellulose of R. aureum were in an enriched state, and the total nitrogen and cellulose of D. angustifolia and mixed litter were in a released state; (4) Medium nitrogen treatment significantly inhibited the release of total phosphorus from R. aureum litter, while high nitrogen treatment significantly promoted the release of total phosphorus from D. angustifolia and mixed litter. These results show that nitrogen deposition can increase the decomposition of litter.