Journal of Geographical Sciences ›› 2011, Vol. 21 ›› Issue (4): 666-676.doi: 10.1007/s11442-011-0871-4

• Eco-environmental Studies • Previous Articles     Next Articles

Effect of solar radiation on net ecosystem CO2 exchange of alpine meadow on the Tibetan Plateau

FAN Yuzhi1,2, ZHANG Xianzhou1, WANG Jingsheng1, SHI Peili1   

  1. 1. Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China;
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2010-08-19 Revised:2010-12-21 Online:2011-08-15 Published:2011-08-05
  • Supported by:

    The Major Basic Research Development Program of China, No.2010CB833501; No.2010CB951704; Knowledge Innovation Program of Chinese Academy of Sciences, No.KSCXZ-YW-N-44; Knowledge Innovation Program of IGSNRR, CAS, No.Y0V00230ZZ

Abstract:

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.

Key words: Tibetan Plateau, alpine meadow, net ecosystem CO2 exchange, solar radiation