[目的]研究玉米群体消光系数的动态变化,提高净第一性生产力或产量的准确评估.[方法]基于中国气象局锦州玉米农田生态系统野外观测站2006年玉米生长季(5～9月)的辐射观测数据和叶面积指数动态观测数据,分析玉米群体的消光系数动态变化.[结果]玉米群体生长季消光系数日变化较大,其最大值分别出现在07:00 ～09:00、15:00 ～ 17:00,最小值出现在12:00前后,但变化幅度在抽雄期变小;在较大的时间尺度上(＞5 d),消光系数(K)与叶面积指数(LAI)呈抛物线关系,决定系数(R2)为0.960 7.当仅考虑消光系数是太阳高度角或叶面积指数的函数时,方程在模拟玉米群体生长季不同时刻的消光系数K值时准确性较差,为此发展了新的消光系数动态模型K=λ(0.784 8-0.001 6θ)(0.1548 LAI2 -0.558 6LAI+0.654).[结论]新的消光系数动态模型综合考虑了太阳高度角和玉米生长季叶面积指数对消光系数的影响,模拟效果优于现有的单因子消光系数模型.%[Objective] The aim was to study the dynamic variation of extinction coefficient of corn population and improve the accuracy of assessment on net primary productivity ( NPP) and yield. [ Method] Based on the data of radiation and leaf area index (LAI) during growing season of com (from May to September) in 2006, observed in Jinzhou observation station of com farmland ecosystem, China Meteorological Bureau, the dynamic variation of extinction coefficient of com population was analyzed. [Result] There was great daily variation in the extinction coefficient of com population during growing season, and the maximum vales appeared from 07:00 to 09:00 and from 15 :00 to 17:00, while the minimum value could be found around 12:00, but the amplitude of variation decreased in tasseling stage. On a large time scale ( >5 d) , there was a parabolic relationship between extinction coefficient (K) and LAI, with determination coefficient R2 of 0.960 7. The simulation e-quation of extinction coefficient, based on sun elevation angle or leaf area index, had poor accuracy at various time during growing season, so a new dynamic model of extinction coefficient was established, namely K = λ(0. 784 8 -0. 001 6θ) (0. 154 8 LAI2 -0.558 6LAI +0.654). [ Conclusion] The effects of sun elevation angle and leaf area index of com on extinction coefficient during growing season were considered in the new dynamic model of extinction coefficient, and its simulation effect was superior to that of single-factor model of extinction coefficient.
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