Abstract: A laboratory incubation experiment was conducted to investigate nitrous oxide (N₂O) emissions in the soil, which was sampled from a red soil of a Pinus massoniana forest in a typical hilly red soil region in subtropical central China, and to study impacts of the soil temperature and moisture on N₂O emissions. The experiment was designed with two environmental factors (temperature and moisture) and 4-5 levels of factors. The results showed that at temperatures of 15, 25 and 30℃ and at soil moistures of WFPS=40%－60% for 15 days the N₂O emissions all displayed a similar trend with a low rate at first, rapid increase during the middle period and no emission in the end. The cumulative N₂O fluxes of the treatments for a period of 15 days were up to 242.85 mg N ·kg^-1. Both the nitrification and denitrification processes were inhibited at 5℃, as a result, the average value of the cumulative N₂O fluxes was just 0.55 mg N ·kg^-1. At WFPS=20%-30%, the cumulative N₂O fluxes for 15 days were very low, ranging from 1.92 to 2.72 mg N ·kg^-1. The average cumulative N₂O fluxes increased with the increases of soil temperature and moisture, especially when WFPS was greater than 40%. A N₂O emission prediction model was established and the model parameters were determined by the nonlinear optimization estimation. The optimization results suggested that the Q₁₀ of N₂O emissions for soil nitrification and denitrification processes was 1.15 and 3.0, respectively; the optimal soil moisture for nitrification-induced N₂O emissions was at WFPS=56%; and the soil WFPS exponential response coefficient for N₂O emissions from soil denitrification was 8.8.

Key words: N₂O emissions, temperature, moisture, Pinus massoniana woodland soil, laboratory incubation