Abstract: Light utilization efficiency (LUE) is an important variable describing photosynthesis production efficiency of vegetation.LUE is also both a critical parameter and conceptual base of productivity efficiency model (PEM) applied to remote sensing data.LUE modeling is an integral source affecting PEM uncertainty.To understand seasonal variation of LUE and its mechanism,the biomass and meteorological factors were observed from July to September of 2006 at Inner Mongolia grassland ecosystem research station.The LUE of Leymus chinensis and Stipa grandis,two main species in temperate grassland,was estimated by observed radiance and biomass data.Results show that LUE of two species vary significantly from this observation period.LUE of S.grandis increases as precipitation increases,while L.chinensis shows no response to precipitation.LUE of both species reach maximum at optimum temperature of 16℃.The effects of water on LUE are more complex,since neither precipitation nor relative humidity alone can explain the relationship between LUE and water.Additional simultaneous observations of soil water content are necessary.LUE will add and improve applications of productivity efficiency models applied to remote sensing data.

Key words: Typical temperate grassland, Leymus chinensis, Stipa grandis, Light utilization efficiency, Seasonal dynamics

摘要： 光能利用率(Light utilization efficiency,LUE或ε)是表征植物光合生产效率的一个重要指标,也是基于遥感的生产效率模型(Production efficiency model,PEM)的概念基础和核心参数。LUE的模拟是影响PEM不确定性的主要原因之一,为了探索LUE的季节波动规律及其控制因素,在内蒙古草原生态定位站对温带典型草原羊草(Leymus chinensis)群落和大针茅(Stipa grandis)群落进行了地面观测。结果表明:在生长盛期,内蒙古温带典型草原的LUE在时间上波动性非常明显,在LUE的各个相关因子中,降水量是决定因子,温度在低于或高于最适温度时,均会影响植被光能利用效率,羊草和大针茅群落最适温度为16℃,高于20℃时,也会限制羊草和大针茅光合作用。水分对植被光能利用率的影响需要进一步进行土壤含水量同步测定研究。本研究结果对于模型参数本地化和参数敏感性分析提供了非常有益的借鉴,为提高基于光能利用率的遥感模型的精度提供了具有重要参考价值的解决途径。

关键词: 温带典型草原, 羊草, 大针茅, 光能利用率, 季节动态