Abstract: Litter respiration is a major component of soil respiration which would be affected by increasing nitrogen deposition via altering the quantity and quality of litter. In order to determine the influence of nitrogen deposition and litter removal on soil respiration, a threeyear field experiment under simulated nitrogen deposition with and without litter removal was conducted in a natural Pinus tabuliformis forest in Taiyue Mountain, Shanxi Province, China. Nitrogen levels were implemented as: CK (0 kg N·hm^-2·a^-1), LN (50 kg N·hm^-2·a^-1), MN (100 kg N·hm^-2·a^-1) and HN (150 kg N·hm^-2·a^-1). The relationships between soil respiration and soil temperature, moisture, microbial biomass after each nitrogen application were analyzed. Results showed that simulated nitrogen deposition promoted soil respiration in the control and litter removal subplots, and litter respiration at the early stage, but the promotion was weakened over time. The litter removal treatments decreased the average rates of soil respiration by 29.0%, and nitrogen deposition decreased the fluctuation of soil respiration after litter removal. A significant exponential correlation was found between soil respiration and soil temperature at 5 cm depth (P<0.05), which explained 37.3%-62.2% of the seasonal variation of soil respiration, and the litter removal treatments decreased the R² of all nitrogen levels. Four twovariable linear/nonlinear models with soil temperature and soil moisture appeared to have a good precision when used to predict the soil respiration, with R² ranging from 0.676 to 0.856, and nitrogen deposition decreased the R² of the litter removal treatments, but it did not significantly affect the R² of the control treatments. Simulated nitrogen deposition increased soil microbial biomass C and N, and the soil respiration exhibited a linear relationship with microbial biomass C and N. It was suggested that nitrogen deposition and litter were two important factors affecting soil CO₂ efflux in P. tabuliformis forests.

Key words: carbon sink industry, carbon sink potential, theoretical basis., de-farming region, economic growth point