Abstract:

Forest ecosystems, being a possibility of an important source in emission of N2O, were rarely studied, especially in subtropical soil N2O emissions from a variety of forest types. This study site was located at Dashanchong Forest Park, being about 50 km away from Changsha City, Hunan Province and one of typical subtropical region of South China, which is the main distribution area of broad-leaved evergreen forests. Using the enclosed chamber technique, soil N2O emissions from a variety of forest types were measured once a month for a year. And environmental factors were also made simultaneous observations, including temperature and soil moisture. The samples were plotted at one kind of pure forest (CL) which species was Cunninghamia lanceolata and three types of mixed forest: PM (composed by Pinus massoniana mainly), CA (composed by Choerospondias axillaria mainly), and CG (composed by Cyclobalanopsis glauca mainly), respectively. In general, it was the sink of N2O for the CA plot, and the source of N2O for the rest three kinds of forest types. Surface fluxes of N2O in the growing season was -27.21 μg/(m2?h) for the CA plot, 34.61 μg/(m2?h) for the PM plot, 30.48 μg/(m2?h) for the CL plot, and 5.82 μg/(m2?h) for the CG plot, respectively. In the growing season, soil N2O flux from PM, CL, CG and CA were not changed significantly with different slope positions. Soil N2O fluxes were closed correlation with soil properties varied with different forest types. And the statistic analysis also showed the soil moisture content was the major factor affecting soil N2O emissions in the study area, and temperature indirectly affected soil N2O emissions by influencing soil moisture content.