CAJ | 학술논문

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。
위료모의하옥미관층내각층협면적지수수직분포，광합유효복사（photosynthetically active radiation, PAR）시연구작물군체광합작용화장세적중요특정삼수，천명관층내PAR적수직분포규률여관층결구등삼수지간적상관관계，가위요감정량반연관층결구삼수제공모형기출。해문기우PAR재관층내적복사전수규률결합관층결구모의불동태양고도각적PAR투과솔수직분포모형，병용지면관층분석의측량치진행험증，결과표명모형대봉롱전옥미추웅기관층내PAR투과솔수직분포모의정도교고。통과불동태양고도각PAR투과솔적수직분포모형결합소광계수운용불동산법분별반연층협면적지수（leaf area index, LAI），병여불동고도층LAI실측치진행비교。결과현시：Bonhomme&Chartier산법반연불동고도층LAI정도교고，상층균방근오차（root mean square error，RMSE）위0.18,중층RMSE위0.55，하층RMSE위0.09。불동태양고도각반연결과존재차이，30°화45°고도각균능교호지반연하층LAI，RMSE분별위0.11여0.09；30°고도각반연중층LAI정도교고，RMSE위0.30；45°고도각반연상층LAI정도교고，RMSE위0.18。결과표명기우불동태양고도각구건적층LAI반연모형경괄우실현하옥미불동고도층LAI적요감고산。해연구가위모의롱행결구관층내LAI수직분포제공삼고。
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 attenuation through the canopy. In this paper, we proposed the method based on the regularity of vertical distribution of PAR by using Beer-Lambert law for inversion of the vertical distribution of LAI in maize canopy. The relationships between the vertical distribution of the leaf area index and solar zenith angle was analyzed, and the results were validated with the measured data. Results showed that the algorithm of Bonhomme&Chartier was proved to be effective for inversion of the vertical distribution of LAI. There were differences in inversion results with different solar zenith angles. In the upper canopy, the solar altitude angle varying from 30° to 45° solar altitude angle could improve LAI estimation accuracy with the RMSE of 0.18, and from 45 to 30 solar altitude angle with the RMSE of 0.30 in the middle canopy, 30° and 45° with the RMSE value of 0.11 and 0.09 in the under canopy. The result showed that it had a fairly good agreement between calculated and observed data, which proved the validity of the theoretical model.