Variation Character Of Main Greenhouse Gas (ch4 And Co2) From Inner Mongolia Typical Temperate Steppe

Grassland ecosystem is an important terrestrial ecosystem type. Typical temperate steppe ecosystem with a variety of different environments, Leymus chinensis steppe ecosystems and desert steppe ecosystems are two major types in grassland ecosystems. In this study, Using a closed static-chamber technique and gas chromatography (GC), we performed field measurements in the Inner Mongolia steppe ecosystems to compare the diurnal and annual variation of greenhouse gas emission between Leymus chinensis plots and sandy plots, to understand the effect on GHG emission budget from the steppe ecosystem and desert grassland ecosystems. This study could provide effective experimental data for greenhouse gas emission from ecosystem. The results are as the follows:1. The value of CH₄ flux is negative in the sandy plots. The diurnal CH₄ emissions varied from -0.1315 to -0.02841 mg CH₄·m^-2·h^-1, the diurnal CH₄ flux mean was -0.0684 mg CH₄·m^-2·h^-1 on September 19th in 2008. The diurnal CH₄ emissions varied from -0.25782 to -0.02225 mg CH₄·m^-2·h^-1, the diurnal CH₄ flux mean was -0.1148 mg CH₄·m^-2·h^-1 on August 23th in 2009. The value of CO₂ flux is positive in the sandy plots. The diurnal CO₂ emissions varied from 89.31595 to 191.1538 mg CO₂·m^-2·h^-1, the diurnal CO₂ flux mean was 131.6391 mg CO₂·m^-2·h^-1 on September 19th in 2008. The diurnal CO₂ emissions varied from 205.0719 to 529.149 mg CO₂·m^-2·h^-1, the diurnal CO₂ flux mean was 347.7160 mg CO₂·m^-2·h^-1 on August 23th in 2009. On a diurnal flux basis, the average GHG emission over two time intervals of 9:00-10:00 AM and 16:00-17:00 PM can be representative for the diurnal period in plant growing season. The relationship between CH₄ emission and temperature in plant growing season showed the extreme value of CH₄ emission appeared in late afternoon and early morning of next day. The death of green plant had a higher impact on CO₂ emission, but the lower impact on CH₄ emission.2. The value of CH₄ flux is also negative in Leymus chinensis plots. The annual CH₄ emissions varied from -0.2200 to -0.0648 mg CH₄·m^-2·h^-1, the annual CH₄ flux mean was -0.1602 mg CH₄·m^-2·h^-1 from grassland CK plots. The annual CH₄ emissions varied from -0.1534 to -0.0890 mg CH₄·m^-2·h^-1, the annual CH₄ flux mean was -0.1336 mg CH₄·m^-2·h^-1 from bare land plots. Leymus chinensis steppe could be considered as an atmospheric CH₄ sink. The annual CO₂ emissions varied from 27.3008 to 325.2815 mg CO₂·m^-2·h^-1, the annual CO₂ flux mean was 216.4107 mg CO₂·m^-2·h^-1 from grassland CK plots. The annual CO₂ emissions varied from 30.4408 to 215.7496 mg CO₂·m^-2·h^-1, the annual CO₂ flux mean was 144.4512 mg CO₂·m^-2·h^-1 from bare land plots.The CH₄ and CO₂ emission in spring and summer were greater than in autumn and winter. The averages of month and annual CO₂ flux from grassland CK plots were higher than those from bare land plots. And part of the month CO₂ emission showed significant difference between the two plots. Therefore, plant growth had a great effect on CO₂ emission.3. The annual CH₄ emissions varied from -0.1020 to -0.0334 mg CH₄·m^-2·h^-1, the annual CH₄ flux mean was -0.0654 mg CH₄·m^-2·h^-1 from sandy plots. The annual CO₂ emissions varied from 24.3079 to 448.7114 mg CO₂·m^-2·h^-1, the annual CO₂ flux mean was 213.9506 mg CO₂·m^-2·h^-1 from sandy plots. When the GHG emission budget and character from the typical temperate steppe ecosystems were estimated, CH₄ emission budget and character from sand was small, but CO₂ emission budget and character from sand could not be ignored. In the typical temperate steppe ecosystems, both grasslands and sands may be considered as the atmospheric CH₄ sink.Analysis result showed that not only the plant biomass and growth, but also the soil physical and chemical properties and soil micro-organisms had important impact on the CH₄ and CO₂ emission, particularly the CH₄ emission. The further research should attach importance to environmental variables influencing CH₄ and CO₂ emission.