Abstract: We examined the emission of CO₂ and N₂O from soils of five forest types (hardwood broad-leaved forest, Korean pine broad-leaved forest, secondary birch forest, Changbai pine forest and Mongolian oak forest) in the process of freeze-thaw by in situ continuous sampling. The results showed that soils from all the forest types were CO₂ and N₂O source during freeze-thaw season. The average flux of CO₂ and N₂O for secondary birch forest and Korean pine broad-leaved forest soils were significantly higher than that of other forest types. Except for the hardwood broad-leaved forest, there was a significant negative correlation between CO₂ flux and soil water content in the forest soils. The water sensitivity of soil CO₂ emissions varied greatly among different forest types. There was a significant positive correlation between soil N₂O flux and soil water content in all forest types except the hardwood broad-leaved forest. The soil CO₂ and N₂O emission fluxes in five forest types were related to the temperature of surface soils by quadratic function.

Key words: freeze-thaw, forest soil, CO₂, N₂O.