Study On Charactors Of CO₂, CH₄, N₂O Fluxes And The Relationship Between That And Environment Factors In The Temperate Typical Grassland Ecosystem

In this paper, the fluxes of carbon dioxide, methane and nitrous oxide(CO2,CH4,N2O)were measured at the same time with static enclosed chamber/GC technique through theexperiment in four represent sample sites in the temperate semi-arid grassland ecosystem inInner Mongolia. The air temperature, soil temperature (0cm, 5cm, 10cm) and soil watercontent were measured parellel with the geses flux measurement. According to the results offield experiment, we analyzed the characteristics and the possible effects of differentenvironmental factors on diurnal variation and seasonal variation of CO2, CH4 and N2O indifferent grassland. The main conclusions are as follows:1. The fluxes of CO2 from soils in different grassland were mostly positive during the field measurements, which indicate that the grassland soil emits CO2 to atmosphere basically. The daily continues measurements showed that the flux of CO2 emission in daytime was higher than that of nighttime. The maximal emission flux occured at 11:30 a.m., and the minimal flux occured at 07:30 in the morning. The range of CO2 emission flux in the original grassland treatment and the reaped grassland treatment are respectively 134.82～ 542.74 mg·m-2·h-1,159.27～435.20 mg·m-2·h-1. The obvious seasonal patterns of CO2 emissions is observed in different grassland type, with a highest CO2 emissions in summer, and it would gradually reduce from autumn to winter. The average fluxes of CO2 in the four sample sites along the precipitation gradient are respectively 361.24, 248.24, 316.33, 223.66 mg·m-2·h-1. The diurnal variation and the seasonal variation were both significantly correlated with the air temperature and soil temperature(0cm,5cm,10cm). Whereas having a weak correlation with the soil moisture. In the four sample sites, the effect of soil moisture to CO2 flux in the Stipa krylovii grassland was more significant than the other three sample sites.2. The fluxes of CH4 in different grassland were mostly negative, this means that the grasslands sink CH4 from atmosphere. The diurnal variation of CH4 flux is complicated, the maximal sink was occurred at night. The minimal absorption flux in the original grassland treatment and the reaped grassland treatment was respectively happened at 9:00 and 16:30. There was no significant relationship between the diurnal variation of CH4 absorption and temperature; There was an obvious seasonal variation in different grassland, the CH4 fluxes were higher in summer and lower in winter. The average fluxes of CH4 in the four sample sites along the precipitation gradient are respectively 0.0555, 0.0503, 0.0568, 0.0657 mg·m-2·h-1. The CH4 fluxes were significantly correlated with the耿会立 温带典型草地生态系统 CO2,CH4,N2O 通量特征及其与环境因子的关系 air temperature and soil temperature. And they were also significantly correlated with soil water in Stipa baicalensis grassland, but in the other three grassland types, there was only weak correlation between CH4 fluxes and soil water.3. In different grassland, the N2O fluxes were almost positive, this is showed that the grassland emits N2O basically. The different types of grassland in Inner Mongolia are all sources for atmosphere air N2O. There was an obvious diurnal variation of N2O fluxes. The peak of the N2O emission appeared at 09:00 in the morning. The emission fluxes were higher in daytime than that in nighttime, The seasonal variation of N2O fluxes were greatly affected by the weather in the day when the air samples were collected. The average fluxes of N2O in the four sample sites along the precipitation gradient are respectively 0.0056, 0.0056, 0.0049, 0.0038 mg·m-2·h-1.The N2O fluxes were weak correlated with soil water content and temperature. The environment factors that affect N2O emission are complicated and we should analyze them synthetically.4. The result of ANOVA(analysis of variance)...