| Karst ecosystem is a ecosystem controlled by karst environment, and epikarst ecosystem is the most active part of material exchange and energy flow in karst ecosystem, it is sensitive to the global carbon cycle in Quaternary, especially in late Holocene. At the same time, karst ecosystem is a frail ecosystem that is liable to be disturbed by the unreasoned or excess economic activities and result in the degeneration of ecosystem. So the research of epikarst ecosystem plays an important role not only in the study of global carbon cycle and "missing sink" but also in the protection of frail karst ecosystem. The research of CO2 dynamic in epikarst ecosystem is the main research content of its running mechanism, especially the soil C02 dynamic. Soil is the hard-core part of epikarst ecosystem, essentially, karstification in epikarst is the earth surface ecosystem process taking soil as a medium, the later is greatly influenced by soil CO2 dynamic in its running mechanism. High concentration soil C02. is not only the driving force of karstification in karst area, but also an important material of photosynthesis of vegetation, it relate to vegetation C02and air C02 by the physical pervasion through the interface between the soil and air, biochemistry process of biology etc.Based on the observation in two observational points situatingdifferent altitudinal belt in Mt. Jinfo (observational point 1 and 2 situate Bitan lake area and Ecologic stone forest area respectively), the distribution and dynamic of CO2 in epikarst ecosystem and main environmental factors are analyzed, which shows that there are apparent daily and seasonal change of CO2 concentration in summer, and the change has close relation with air temperature, soil temperature, precipitation and soil water content etc., at the same time, its discipline varies with different vegetation types, geology and geomorphology conditions and soil features etc..(1) The profile distribution and dai ly dynamic of CO.. in epikarst ecosystem in summer: there is similarity in two observational points, soil CO2 concentration increase in turn with the depth of soil in soil subsystem; in vegetation-air subsystem, CO2 concentration increase from the leaves layer to the ground. The daily dynamic has close relation with temperature of air and soil, soil C02 concentration will increase while vegetation CO2 concentration will decrease with the temperature increasing. Heavy rainfall and high soil water content will reduce soil CO2 concentration while small one and proper soil water content will get it up. As to the dynamic of CO. concentration in a day, soil layer and vegetation layer take on reverse change to some extent. The difference in different altitudinal belts shows in concentration level mainly, it is lower in evergreen and defoliation broadleaf woods in Ecologic stone forest area than it in the second shaw in Bitan lake area.(2) The profile distribution and seasonal dynamic of CO2 in epikarst ecosystem in summer: in the second shaw in Bitan lake area, the profile distribution of soil C02 in season is consistent with it in a day, C02 concentration gets up with soil depth deepening; soil C02 dynamic is coherent with temperature fluctuation; the influence of precipitation toC02 dynamic is more complex which is closely relative to rainfall. Heavy rainfall causes the reduction of soil CO2 concentration while small one increase it; both the concentration difference in different layer of soil profile and the concentration variability in the same layer are little. In general, vegetation CO2 concentration increase from woods layer and shrub layer to herbage in vegetation-air subsystem, but it is not obvious and vegetation CO2 dynamic has little relation with air temperature and precipitation. In evergreen and defoliation broadleaf woods in Ecologic stone forest area, it is more complex than observational area 1 in profile distribution and seasonal dynamic of soil CO., though inmost time it shows some consistence in C02 concentration and soil depth; its dynami...
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