Abstract: In order to provide basic data for seasonal dynamics and total amount estimation of N₂O emission from mountain marshes, this study was performed to understand the diurnal variation of N₂O emission fluxes from Carex schmidtii marsh and Betula ovalifolia-Carex schmidtii shrub swamp in Xiaoxing'an Mountains. An experiment was conducted to observe the diurnal variation of N₂O fluxes in marsh and shrub swamp in Xiaoxing'an Mountains using the static opaque chamber and gas chromatography techniques on August 4-5 of 2007, September 24-25 of 2007, and June 4-5 of 2008. The results showed that the diurnal variation of N₂O emission flux in two kinds of marshes showed a diurnal high-night low pattern on August 4-5 of 2007, the daily emission regularity is not significant on September 24-25 of 2007 and June 4-5 of 2008. The highest N₂O fluxes in marsh were appeared at 9：00 on August 4-5 of 2007 and June 4-5 of 2008, and appeared at 3：00 on September 24-25 of 2007. The lowest N₂O fluxes in marsh were appeared at 21：00 on June 4-5 of 2008 and September 24-25 of 2007, and appeared at 18：00 on August 4-5 of 2007. The highest N₂O fluxes in shrub swamp were appeared at 15：00 on August 4-5 of 2007 and appeared at 6：00 on September 24-25 of 2007, and appeared at 9：00 on June 4-5 of 2008. The lowest N₂O fluxes in shrub swamp were appeared at 21：00 on August 4-5 of 2007, and appeared at18：00 on September 24-25 of 2007 and appeared at 3：00 on June 4-5 of 2008. Two kinds of marshes were the absorption sinks of N₂O on June 4-5 of 2008, and were the weak emission sources on August4 -5 and September 24 to 25, 2007. The diurnal variation N₂O fluxes of shrub swamp were higher than those of marsh. The daily N₂O emission flux of two kinds of marshes were negatively correlated with temperature on September 24-25 of 2007 and June 4-5 of 2008, and were Positive correlation with temperature on August 4-5 of 2007. Among them, the daily N₂O emission fluxes of marsh were negatively correlated with 10 cm soil temperature, while that of shrub swamp were negatively correlated with 15 cm soil temperature. The diurnal N₂O emission fluxes of marsh were positively correlated with surface temperature, while that of shrub swamp were positively correlated with 40 cm soil temperature. The marsh and shrub swamp in Xiaoxing'an Mountains were weak sources or sinks of N₂O emission, the temperature, water level and vegetation types were the main influencing factors of N₂O daily emission fluxes.

Key words: N₂O fluxes, diurnal variation, Carex schmidtii marshes, Betula ovalifolia-Carex schmidtii shrub swamp, temperature, Xiaoxing'an Mountains