Abstract: As one of the main greenhouse gases, N₂O has a significant impact on the Earth and human beings. To explore the influence mechanisms of heterotrophic nitrification of organic N and N₂O emission process and improve global N₂O flux estimation model, Pearson correlation analysis and generalized additive model (GAM) were used to analyze the influencing factors of heterotrophic nitrification rates of organic N and N₂O emission rates in 135 sampling sites worldwide. The major influencing factors were included into BP neural network model to estimate the spatial distribution of heterotrophic nitrification rates of organic N and N₂O emission rates in global forest soils. The results showed that soil pH and C/N were the main factors affecting heterotrophic nitrification rate of organic N. Soil C/N, water-filled pore space (WFPS), and temperature are the main factors affecting N₂O emission rate during heterotrophic nitrification process. The average heterotrophic nitrification rate was 0.4241 (0.0014-0.689) μg N·g^-1·d^-1, and the average N₂O emission rate in the heterotrophic nitrification process was 0.2936 (0.21-1.103) μg N₂O·kg^-1·d^-1 in global forest soils. The heterotrophic nitrification rate and N₂O emission rate in the heterotrophic nitrification process were higher in forest soils around 50° N. In contrast, the two rates were lower in forest soils from 30° S to 30° N. Although heterotrophic nitrification rate was high, N₂O emission rate in the heterotrophic nitrification process was low in forest soils in Northeast Asia. N₂O emission flux from the heterotrophic nitrification of organic N was （1.4584±0.3791） Tg N·a^-1 in global forest soils, accounting for 26.04% of N₂O emission from natural soils and 8.58% of global N₂Oemission.

Key words: heterotrophic nitrification rate N₂O emission rate in heterotrophic nitrification process, BP neural network, environmental factor, spatial distribution.