摘要
为了模拟夏玉米冠层内各层叶面积指数垂直分布,光合有效辐射(photosynthetically active radiation,PAR)是研究作物群体光合作用和长势的重要特征参数,阐明冠层内PAR的垂直分布规律与冠层结构等参数之间的相关关系,可为遥感定量反演冠层结构参数提供模型基础。该文基于PAR在冠层内的辐射传输规律结合冠层结构模拟不同太阳高度角的PAR透过率垂直分布模型,并用地面冠层分析仪测量值进行验证,结果表明模型对封垄前玉米抽雄期冠层内PAR透过率垂直分布模拟精度较高。通过不同太阳高度角PAR透过率的垂直分布模型结合消光系数运用不同算法分别反演层叶面积指数(leaf area index,LAI),并与不同高度层LAI实测值进行比较。结果显示:Bonhomme&Chartier算法反演不同高度层LAI精度较高,上层均方根误差(root mean square error,RMSE)为0.18,中层RMSE为0.55,下层RMSE为0.09。不同太阳高度角反演结果存在差异,30°和45°高度角均能较好地反演下层LAI,RMSE分别为0.11与0.09;30°高度角反演中层LAI精度较高,RMSE为0.30;45°高度角反演上层LAI精度较高,RMSE为0.18。结果表明基于不同太阳高度角构建的层LAI反演模型更适于实现夏玉米不同高度层LAI的遥感估算。该研究可为模拟垄行结构冠层内LAI垂直分布提供参考。
Photosynthetically active radiation(PAR) is an important parameter in agricultural applications.Some researchers showed that many parameters,such as leaf area index(LAI),leaf angle distribution(LAD) and the heterogeneity of vegetation,were concerned with the distribution of PAR.Many models were used to simulate the distribution of PAR effectors,such as the structure of canopy and sun zenith angle.This paper simulated the vertical distribution of PAR in the canopy and analyzed the relationships between PAR and some parameters,such as solar zenith angle,LAD,LAI,maize canopy structure,special for the heterogeneous canopies such as that crop with width and narrow ridges.It took account the effects of structural features of different type canopies.In this study,the distributions of solar radiation at different heights in maize canopy were simulated based on the radiation transfer model.The row structure model was used to simulate the vertical distribution of PAR in canopies.It accounted for direct radiation including radiation paths going through one or more rows.Leaf angle distribution was generated by using this model to measure leaf angle distributions in canopies.Intensive investigation was made on the effect of these canopy architecture on the penetration of total visible radiation into the canopy at various solar zenith angle.The simulation result of PAR in maize canopy was validated with the measured data,and it appeared good accuracy.By simulation with box model,the regularity of vertical distribution of PAR in the canopy showed that:1) the transmittance of solar incidence was affected by the effective light path;2) the attenuation of light in the canopy was diminishing exponentially along the light path.It could be reflected by the vertical distribution of light extinction coefficient(K);3) the solar altitude angle varying from 60° to 45° or 30° solar altitude angle with the RMSE value of 0.07 or 0.08,it could improve PAR estimation accuracy.The vertical distribution of leaf area was affected by the light
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2015年第S1期221-229,共9页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(41271412)
中国科学院百人计划项目"植被定量遥感参数反演与真实性检验"(黄文江)
安徽省高校省级自然科学研究项目(KJ2012Z108)
关键词
遥感
农作物
辐射
夏玉米
光合有效辐射透过率
垂直分布
层叶面积指数
remote sensing
crops
radiation
maize
photosynthetically active radiation(PAR)
vertical distribution
layer leaf area index(LAI)
