Objective To study the release dynamics of potassium, calcium, and magnesium during litter decomposition under simulated nitrogen deposition, so as to better understand the nutrient cycling process of forest ecosystem under continuously increasing nitrogen depositions.

Method NH₄NO₃ was used to establish the low level (L), medium level (M), high (H) level and the control (CK) treatments of nitrogen deposition in a natural evergreen broadleaved forest in the Rainy Area of Western China. Nylon mesh bag method was employed to simulate litter decomposition under nitrogen deposition. Experiment continued for one year and the concentration, remaining percentages and release patterns of potassium, calcium, and magnesium during litter decomposition were studied.

Result After one year of decomposition, the simulated nitrogen deposition significantly inhibited the decrease of potassium in the process of litter decomposition, which significantly promoted the decrease of calcium concentration and had no significant effects on magnesium concentration. However, the simulated nitrogen deposition did not change the release pattern of potassium, calcium, and magnesium during litter decomposition. The potassium exhibited a net release pattern in all the four treatments, the calcium exhibited release-enrichment alternate pattern and the magnesium exhibited an enrichment-release pattern. The remaining percentages of potassium in L, M and H treatments increased by 3.91%, 10.27% and 13.91% respectively compared with the CK, showing that the nitrogen deposition significantly inhibited the release of potassium. The remaining percentage of calcium in L, M and H treatments decreased by 6.39%, 6.51% and 15.93% respectively compared with CK, i.e. nitrogen deposition significantly promoted the release of calcium. There was no significant difference in the remaining percentages of magnesium between the control and the nitrogen treatments i.e. simulated nitrogen deposition had no significant effect on the dynamics of magnesium during litter decomposition.

Conclusion Simulated nitrogen deposition will not change the release pattern of potassium, calcium, and magnesium, but has different effects on the release rate of potassium, calcium, and magnesium during litter decomposition.