Abstract: During the soil thawing period in spring, large amount of N2O was emitted from the forest soils in North China, being a major source of atmospheric greenhouse gases. However, the contribution of the emitted N2O and its responses t o climatic change are unclear. In this paper, sampling plots of Larix gmelinii  f orest (including sapling, ground vegetation, and soil A and B horizons) with sim ilar stand conditions in Tahe (52°31′ N), Songling (50°43′ N), Sunwu (49°13′ N), and Dailing (47°05′ N) were displaced to the south boundary of L. gmelinii natural distribution area to simulate that the plots were under climate warming, and their N2O fluxes were measured during the soil thawing period in spring 2 007. For the four plots, the N2O fluxes all peaked at the mid- or late stage of soil thawing. The N2O flux of the plots from Dailing, Suwu, Songling, and T ahe during soil thawing period was averagely 665±93, 543±56, 443±53, and 335±37 μg ·m-2·h-1, respectively, and significantly positively correlated to the soil temperature at 5 cm depth and the soil microbial biomass carbon at 0 〖KG-*2〗-〖KG-*7〗1 0 cm depth. No significant relationship was observed between the N2O flux and soil moisture content. The soil N2O emission during soil thawing period differ ed significantly among the plots. Both the mean N2O flux and the cumulative N 2O emission decreased with increasing latitude, mainly due to the differences in soil microbial activities and soil physical properties.

Key words: depression between karst hills, land use pattern., soil microbe, environment