Abstract: Seasonal dynamics of N2O flux and its controlling factors for four representative temperate forests in northeastern China were examined with a static closed chamber-gas chromatograph technique. These forests were Korean pine (Pinus koraiensis) plantation, Dahurian larch (Larix gmelinii) plantation, Mongolian oak (Quercus mongolica) forest and hardwood broadleaved forest (dominated by Fraxinus mandshurica, Juglans mandshurica, and Phellodendron amurense). The results showed that all ecosystems were overall atmospheric N2O source during the growing season. The N2O flux (μg·m-2·h-1) decreased in order of the hardwood broadleaved forest (210±49)>the pine plantation (176±46)>the larch plantation (98±59)>the oak forest (16±126). Overall, there was no consistent seasonal pattern in N2O flux for the four ecosystems. The N2O flux was significantly positively correlated to soil gravimetric water content (0〖KG-*2〗-〖KG-*7〗10 cm depth) consistently for all ecosystems, but significantly negatively correlated to NO3--N content for each ecosystem. However, the responses of N2O flux to soil temperature and NH4+-N differed among the ecosystems. The N2O fluxes for the coniferous plantations were positively correlated to NH4+-N, but not correlated to the soil temperature at 5 cm depth; while those for the broadleaved forests displayed an opposite trend. The soil water content was the dominator of soil N2O emission for the forests in 2007 perhaps resulting from relative drought in the year. Interactions of vegetation type, environmental factor, and nitrogen availability to soil N2O emission should be further studied in the future.

Key words: Dongting Lake wetland, ecosystem service value, Three Gorges Reservoir impoundment.