Abstract: Nutrient release from decomposing litter is a main source of soil nutrients. Consequently, litter nutrient dynamics are of great importance to maintain soil fertility and stand productivity in forests. However, most previous studies have focused on nutrient dynamics of litter decomposing on forest floor, but ignored nutrient dynamics of litter decomposing in the air. Moreover, little is known about the dynamics of litter medium nutrient elements such as calcium and magnesium in forests compared with the macronutrients such as nitrogen and phosphorus. In this study, we selected leaf litter of four common afforestation species (Pinus massoniana, Pinus elliottii, Liquidambar formosana, and Schima superba) in subtropical regions and used the litterbag method to investigate the effects of stand type (P. massoniana, P. elliottii, L. formosana, and S. superba plantations) and decomposition position (in the air and on the forest floor) on litter nitrogen, phosphorus, calcium, and magnesium dynamics. The results showed that, across the four plantations, leaf litter nitrogen exhibited an initial immobilization and subsequently a net release during 360-day decomposition. However, litter phosphorus remaining during decomposition initially increased and then decreased in P. massoniana and P. elliottii plantations, but showed a net decline in the L. formosana and S. superba plantations. In addition, litter calcium and magnesium showed a gradual net release during 360-day decomposition in the four plantations. Litter nitrogen, phosphorus, calcium, and magnesium remaining of L. formosana and S. superba was greater in the air than on the forest floor, whereas P. massoniana and P. elliottii litter nitrogen, phosphorus, calcium, and magnesium remaining did not exhibit a consistent changing pattern between in the air and on the forest floor during decomposition. These findings suggest that stand type and decomposition position are important determinants of litter nutrient release and highlight that the release patterns of litter macronutrients and medium nutrients differ during decomposition. These observations will be beneficial to understanding nutrient cycling and designing appropriate nutrient management practices in subtropical plantations.

Key words: litter decomposition, aerial decomposition, nutrient immobilization, nutrient return, subtropical forest