Primary Research On Light Utility Efficiency Of Temperate Typical Grassland In Inner Mongolia

Light utility efficiency(LUE) means the efficiency of vegetation absorbing and converting solar engery and synthesizing biomass. LUE was firstly applied in tropical forest ecosystems research by Monteith in 1972. LUE is not only a ecology concept, but also is a critical parameter in the productivity models based on remote sensing which are applied in moitoring of net primary productivity and assessment of carbon cycle. But some problems should be considered in LUE research. 1. The difinition is not consistent, which is caused by different research aims and methods; 2.There is poor comparability among present results for different methods; 3.More researchs focus on crops, while the few on natural vegetation; 4. scaling up on LUE, such as how to apply apparent photosynthetic quantum yield(α) based on leaf scale to landscape or biosphere scale. Aiming to answer those problems, in Inner Mogolia steppe ecology research station, the LUE on two typicalest temperate grassland community —Stipa grandis P. Smirn and Leymus chinensis(Trin.) Tzvel. was studied through observing photosynthetic assimilation, respiration and accumulated biomass and leaf area index(LAI). And a was fited through Michaelis-Menten function. Consequently, Biomass research may be a better method when determining average LUE of a period, while the LUE estimated by leaf photosynthetic assimilation velocity and LAI is only instantaneous value on the observing day. Since Inner Mongolia steppe is more sensitive to variability of climate, the instantaneous LUE may not well describe the lighe utility efficiency in whole growth period with more uncertainties. Maximum a of Leymus chinensis(Trin.) Tzvel. community and Stipa grandis P. Smirn community respectively is 0.050048 umolCO₂ umol^-1 photon and 0.029782 umolCO₂ umol^-1 photon, and Maximum a of Leymus chinensis(Trin.) Tzvel. species and Stipa grandis P. Smirn species respectively is 0.043097 umolCO₂umol^-1photon and 0.018056 umolCO₂umol^-1 photon.The average LUE of Leymus chinensis(Trin.) Tzvel. community and Stipa grandis P. Smirn community respectively is 0.074277%, and 487732% in observing period.