The Influence Of Gap And Temperature On The CO₂ And N₂O Emissions And Nitrogen Mineralization Of Temperate Forests

This paper studied on the mechanism about emission fluxes of CO2 and N2O under different hydrothermal conditions in the forest soil on the basis of site observations in the soil of Broadleaved Mixed forest in Changbai Mountain forest gap. Meanwhile, in order to improve the study result about the CO2 and N2O gas flux changes caused by hydrothermal condition changes, this study choose the original broadleaf, natural secondary forest and deforestation, cultivation of ginseng as the study area. Carbon dioxide (CO2) and nitrous oxide (N2O) emission in the 0-10 cm,10-20 cm and 20-30 cm soil and under different landuse, such as original broadleaf, natural secondary forest and deforestation, cultivation of ginseng, was studied in the laboratory simulation tempreture of the 5℃,15℃,25℃and 35℃. The main results are as follows:Site observation results show that the soil temperature and moisture,which are below-surface 5cm,are significant differences between the forest gap and the forests.CO2 and N2O fluxes changed significantly with the seasons during observation period.CO2 emission flux within the forest gap is smaller than that in the forests.The emission peak occurs in August. N2O emission flux within the forest gap is much greater than that in the forests.The emission peak occurs in September. The statistical analysis result shows that the underground 5cm soil temperature is the key factors affecting the CO2 flux. There is a negative correlation between soil moisture and CO2 flux.Temperature demonstrate more influential on the forest soil than the response gaps. N2O fluxes influenced by humidity significantly, and temperature was significantly positively with N2O fluxes.The temperature response in the gaps is greater than forests.Soil properties of experimental analysis is conducted and the result shows that soil properties between gaps and forests differ greatly. The correlation analysis results show that soil properties of dissolved organic carbon and nitrogen content, water-soluble organic carbon, microbial carbon and nitrogen are relevant to the CO2 and N2O emission fluxes.The in-house temperature control experiments show that soil CO2 emission in the original broad-leaved forest, natural secondary forest and ginseng cultivation displays a descending order in the three different land use types, while N2O emission flux in the original broad-leaved forest, ginseng cultivation and natural secondary forest displays a descending order. The largest volume of CO2 and N2O emissions is in the 0-10 cm soil depth. Statistical analysis result shows that temperature is the main factors affecting CO2 and N2O fluxes at different depths of soil in the three levels of land use types under the same level of WFPS. It can explain 68.8% of CO2 mutation rate, and 56.6% N2O mutation rate respectively. Soil properties of experimental analysis result shows that the temperature affects the CO2 and N2O emission by means of changing the different forms of carbon and nitrogen content in the soil properties.