| With more and more widespread attention payed to global change, changes in atmospheric concentrations of greenhouse gases has increasingly become a global change research focus as an important driving factor in related fields. Various research reports on greenhouse gas sources or sinks problems are common. Because CO2 content in the atmosphere is far greater than other greenhouse gases, its greenhouse effect is also the top of greenhouse gases. Thus source or sinks of CO2 are of concern, and with going deep into this problem, there is an urgent need for a technology which can observe CO2 release and absorption directly and quantitatively, further capturing budget of the global atmospheric CO2 balance, to predict and control the effects of changes in greenhouse gases to global change. This article uses the eddy covariance technique for a long, continuous, real-time observation of typical alpine wetland ecosystem CO2 exchange at Qinghai Lake small park lake. Using 2012 observational data, we have analyzed net ecosystem CO2 exchange characteristics and the mechanisms of influencing factors affecting the ecosystem CO2 exchange.The results showed that:1. Qinghai Lake small park lake alpine wetland ecosystem is a big CO2 gas sink: GPP(Gross primary productivity) is-2675.01 gCO2·m-2, Re (Ecosystem respiration)of all over the year is 1402.49gCO2·m-2, Re is 52% of GPP, GEP(Ecosystem net primary productivity) is-1272.52 g CO2·m-2, GPP is close to that of other alpine ecosystems, but Re is smaller than that of these ecosystems, which contribute to the high CO2 absorption ability.2. There is CO2 absorption ability at the whole year. All over the daytime, the change of NEE is "U", at 14:00, the value of CO2 absorption become maximum,the phenomenon of " noon break" is observed, and the NEE chang of night is slightly.3. Qinghai Lake small park lake alpine wetland ecosystem surface-atmosphere CO2 exchange process has obvious difference between seasons, summer is most active, spring and autumn is follow, winter is weakest. Two CO2 releasing period is existed, as April and October-November, CO2 sinks in other months, especially in July and August, diurnal NEE varies from-19.268 to 2.454 g·m-2·d-1.4. The diurnal variation of ecosystem respiration is very gentle, as irregular "∽" shape, night respiration decreased, reaching the lowest value at about 8:00, at daytime, it gradually increased, rising to the greatest value at 20:00.5. Ecosystem respiration range of 0.41-12.69μmolCO2·m-2·d-1, small change in winter, from spring to autumn, it rise frist and decline after, mid-July to early August is the breathing peak of the year.6. Overall the trends of seasonal NEE variation is controlled by temperature. At different period, temperature combined with other factors impact on the diurnal variation of NEE.7. Ecosystem respiration is controlled by Ta and Ts, as main influence factor in turn from different season. Due to the freezing and thawing, the soil moisture increased dramatically, inhibiting alpine wetland ecosystem respiration, resulting in the two CO2 emission peaks reduced.8. Comparing of different Tibetan-Plateau grassland ecosystems, we believe that the high CO2 absorption capacity is result of the mutual action of the high soil moisture and freezing-thawing. |
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