Abstract: The effects of soil temperature (0, 5, 15, 25, 35 ℃) and water content on soil respiration in three forest types in Changbai Mountain were evaluated in laboratory condition. The results indicated that the soil respiration rate was positively correlated to soil temperature from 0 to 35 ℃ and it increased with soil water content from 0.21 to 0.37 kg·kg^-1. The soil respiration rate decreased with soil water content when water content was over the range. The result suggested the interactive effects of temperature and water content on soil respiration. There were significant differences in soil respiration among the various forest types and the highest was in broad leaf Korean pine forest, then in erman's birch forest, and it was the lowest in dark coniferous forest. The optimal condition for soil respiration in broad leaved Korean pine forest was at 35 ℃ under 0.37 kg·kg^-1 water content, and it was at 25 ℃ under 0.21 kg·kg^-1 in dark coniferous forest and at 35 ℃ under 0.37 kg·kg^-1 water content in erman's birch forest. Because the forests of broad leaf Korean pine, dark coniferous and erman's birch are located at various altitudes, the soil temperatures had 4～5 ℃ variation in different forest types during the same period. The soil respiration rates measured in brown pine mountain soil were lower than those in dark brown forest and they were higher in mountain grass forest soil than those in brown pine mountain soil.

Key words: Soil temperature, Soil water content, Soil respiration rate, Forest ecosystems in Changbai Mountain