摘要
设计了一套田间观测试验 ,以测定光合有效辐射 (PAR ,PhotosyntheticallyActiveRadiation)在玉米冠层内三维空间上的分布规律。对实测资料的分析得出如下结论 :( 1)玉米冠层内平均PAR的垂直分布具有随着向下累计叶面积指数的增加而指数递减的趋势。在冠层中上部 ,PAR透光率较高 ,递减很明显 ,冠层下部则维持较低水平 ,变化不大。在相同的天气和时间条件下稀植或密植冠层内PAR透光率随累计LAI递减的趋势相近 ,但在不同时刻 (太阳入射角度不同 )、不同天气条件下 ,即使相同的冠层也具有不同的消光系数。 ( 2 )在常规种植密度的玉米冠层中上部 ,光斑面积大 ,光斑内PAR透光率高、变化小 ,但冠层下部的光斑很少或不明显 ,最大PAR透光率也可能会很低。 ( 3)稀植会明显增加冠层下部的光斑和平均PAR透光率。 ( 4 )阴天时冠层内部PAR强度显著减小。
An experiment to measure the 3D PAR (Photosynthetically Active Radiation) distribution in maize canopy was designed. The following results have been achieved through 3D PAR analysis from this experiment. (1) The averaged PAR at different depths in maize canopy was decreased with the increase of accumulated LAI by exponential law. The decrease trend of PAR transmittance of maize canopy was very similar for different density at same time and weather. But the extinction coefficient varied evidently with different weather and different sunshine angle even for the same canopy. (2) There were much more flecks of sunlight in upper canopy. The PAR transmittance in the flecks was high and varied very slightly. Within the lower canopy, the averaged PAR was very low and there were very few flecks of sunlight. The maximum PAR transmittance was also very low. (3) Lower maize planting density would increase flecks of sunlight and PAR transmittance evidently in canopy bottom. (4) PPFD (Photosynthetic Photon Flux Density) and maximum PAR transmittance in maize canopy was badly decreased in cloudy days. This study might provide some references for the simulation of 3D light distribution and experiment design of 3D light measurement in crop canopy.
出处
《作物学报》
CAS
CSCD
北大核心
2004年第6期568-576,共9页
Acta Agronomica Sinica
基金
国家重点基础研究发展规划项目 (G19990 1170 9)
国家 863计划项目( 2 0 0 1AA2 45 0 2 1)
国家自然科学基金项目( 3 9970 42 8)资助
