Meteorological elements and CO_(2) fluxes over alpine meadow ecosystem were observed continuously from 2004 to 2005 in Damxung Alpine Meadow Flux Station,China Flux Network.Based on the eddy covariance CO_(2) fluxes a...Meteorological elements and CO_(2) fluxes over alpine meadow ecosystem were observed continuously from 2004 to 2005 in Damxung Alpine Meadow Flux Station,China Flux Network.Based on the eddy covariance CO_(2) fluxes and meteorological data obtained,the relationships among the CO_(2) fluxes,the cloud amount,and the meteorological factors in alpine meadow ecosystem were explored and analyzed.Some conclusions can be drawn from the discussion with previous researches as following:(1)the cloud amount can affect the net ecosystem CO_(2) exchange(NEE)of alpine meadow on Tibetan Plateau;(2)the soil temperature sensitive to the cloud amount,is a major environmental controlling factor for NEE,and closely relates to the maximum of NEE.In the moming period with large cloud amount,the NEE reaches its maximum when the clearness index ranges from 0.5 to 0.7;yet in the afternoon it comes to the maximum with the index from 0.2 to 0.35.The span of soil temperature covers from 12 to 15℃as the NEE at its highest;(3)the scatterplots between NEE and photosynthetic available radiation(PAR)was a significant inverse triangle in the clear day,two different kinds of concave curves in the cloudy day,and strongly convergent rectangular hyperbola in the overcast day.These differences were controlled by the changes of light radiation and soil temperature.展开更多
On the Tibetan Plateau, the alpine meadow is the most widespread vegetation type. The alpine meadow has a low biological productivity and low vegetation coverage in the growing season. The daytime NEE between the atmo...On the Tibetan Plateau, the alpine meadow is the most widespread vegetation type. The alpine meadow has a low biological productivity and low vegetation coverage in the growing season. The daytime NEE between the atmosphere and the alpine meadow ecosystem was influenced by solar radiation. To analyze the characteristics of change in NEE and to calculate the parameters related to photosynthesis and respiration in different solar radiation environments, the NEE measurements were taken in Damxung from July to August in 2003, 2004, 2005 and 2006 using the eddy covariance technique. Solar radiation was grouped into three levels according to the net radiation, which was more than 155 W m-2 d-1 on clear days, 144±5 W m-2 d-1 on partly cloudy days and less than 134 W m-2 d-1 on cloudy days. The diurnal relationships between NEE and PAR varied with differences in solar radiation, which was a rectangular hyperbola form on clear days, two different concave curves on partly cloudy days and an irregular triangle form on cloudy days. The mean CO2 absorption rate showed a decreasing trend with increasing solar radiation. The daytime absorption maximum occurred around 10：00 on clear days with an average of slightly less –0.2 mg m-2 d-1, around 11：00 on partly cloudy days with an average of about –0.2 mg m-2 d-1, and around 12：00 on cloudy days with an average of about –0.25 mg m-2 d-1. As solar radiation increased, the Amax and the Q10 decreased. However, the R10 increased and the maximum of the α occurred on partly cloudy days. The optimum net solar radiation was about 134–155 W m-2 d-1, which induced a PAR of about 1800-2000 μmol m-2 s-1 and soil temperature at a depth of 5 cm of about 14℃. Therefore, on the Tibetan Plateau, the alpine meadow ecosystem will have a higher carbon absorption potential while solar radiation decreases in the future.展开更多
基金Under the auspices of the Major Basic Research Development Program of China(Grant no.2005CB422005)the Knowledge Innovation Program of Chinese Academy of Sciences(Grant no.KSCXZ-YW-N-44)
文摘Meteorological elements and CO_(2) fluxes over alpine meadow ecosystem were observed continuously from 2004 to 2005 in Damxung Alpine Meadow Flux Station,China Flux Network.Based on the eddy covariance CO_(2) fluxes and meteorological data obtained,the relationships among the CO_(2) fluxes,the cloud amount,and the meteorological factors in alpine meadow ecosystem were explored and analyzed.Some conclusions can be drawn from the discussion with previous researches as following:(1)the cloud amount can affect the net ecosystem CO_(2) exchange(NEE)of alpine meadow on Tibetan Plateau;(2)the soil temperature sensitive to the cloud amount,is a major environmental controlling factor for NEE,and closely relates to the maximum of NEE.In the moming period with large cloud amount,the NEE reaches its maximum when the clearness index ranges from 0.5 to 0.7;yet in the afternoon it comes to the maximum with the index from 0.2 to 0.35.The span of soil temperature covers from 12 to 15℃as the NEE at its highest;(3)the scatterplots between NEE and photosynthetic available radiation(PAR)was a significant inverse triangle in the clear day,two different kinds of concave curves in the cloudy day,and strongly convergent rectangular hyperbola in the overcast day.These differences were controlled by the changes of light radiation and soil temperature.
基金The Major Basic Research Development Program of China, No.2010CB833501 No.2010CB951704+1 种基金Knowledge Innovation Program of Chinese Academy of Sciences, No.KSCXZ-YW-N-44Knowledge Inno-vation Program of IGSNRR, CAS, No.Y0V00230ZZ
文摘On the Tibetan Plateau, the alpine meadow is the most widespread vegetation type. The alpine meadow has a low biological productivity and low vegetation coverage in the growing season. The daytime NEE between the atmosphere and the alpine meadow ecosystem was influenced by solar radiation. To analyze the characteristics of change in NEE and to calculate the parameters related to photosynthesis and respiration in different solar radiation environments, the NEE measurements were taken in Damxung from July to August in 2003, 2004, 2005 and 2006 using the eddy covariance technique. Solar radiation was grouped into three levels according to the net radiation, which was more than 155 W m-2 d-1 on clear days, 144±5 W m-2 d-1 on partly cloudy days and less than 134 W m-2 d-1 on cloudy days. The diurnal relationships between NEE and PAR varied with differences in solar radiation, which was a rectangular hyperbola form on clear days, two different concave curves on partly cloudy days and an irregular triangle form on cloudy days. The mean CO2 absorption rate showed a decreasing trend with increasing solar radiation. The daytime absorption maximum occurred around 10：00 on clear days with an average of slightly less –0.2 mg m-2 d-1, around 11：00 on partly cloudy days with an average of about –0.2 mg m-2 d-1, and around 12：00 on cloudy days with an average of about –0.25 mg m-2 d-1. As solar radiation increased, the Amax and the Q10 decreased. However, the R10 increased and the maximum of the α occurred on partly cloudy days. The optimum net solar radiation was about 134–155 W m-2 d-1, which induced a PAR of about 1800-2000 μmol m-2 s-1 and soil temperature at a depth of 5 cm of about 14℃. Therefore, on the Tibetan Plateau, the alpine meadow ecosystem will have a higher carbon absorption potential while solar radiation decreases in the future.
