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叶片聚集度系数量化了在树冠随机的情况下叶片空间分布的聚集程度,对生态模型建模有重要作用.本研究利用MODIS BRDF模型参数产品(MCD43A1)以及土地覆盖类型数据(MCD12Q1),基于Ross-Li半经验模型模拟了热点和暗点的反射率,计算归一化的热点与暗点差值指数(NDHD),结合最小二乘法模拟的NDHD与聚集度系数的关系,反演了2014年8月500 m分辨率的大兴安岭地区植被叶片聚集度系数.并在大兴安岭地区采用冠层分析仪TRAC采样测量,对聚集度系数进行实地验证并对结果进行分析.结果表明:Ross-Li模型模拟的数据与样地实测数据具有显著的相关性(R~2=0.8879),说明利用MCD43A1数据反演聚集度系数算法的可行性;MODIS近红外波段对叶片聚集度系数变化的灵敏度比红色波段更高;随着太阳天顶角的增加,Ross-Li模型推导出的聚集度系数呈线性增长趋势(R~2=0.9699),说明叶片聚集度系数与天顶角变化有关.
The coefficient of leaf aggregation degree quantifies the degree of spatial distribution of leaves in the random crown tree and plays an important role in modeling ecological models.In this study, MODIS BRDF model parameters (MCD43A1) and land cover type data (MCD12Q1) -Li semi-empirical model to simulate the reflectivity of hot spots and dark spots, calculate the normalized hot spot and dark point difference index (NDHD), combined with the least squares method to simulate the NDHD and aggregation coefficient, the inversion of the 2014 August in Daxinganling area with the resolution of 500 m, and using the canopy analyzer TRAC sampling in the Greater Khingan Range to verify the degree of aggregation and analyze the results.The results show that the Ross-Li model (R ~ 2 = 0.8879), indicating the feasibility of using the MCD43A1 data inversion clustering coefficient algorithm; MODIS near-infrared band sensitivity of leaf aggregation degree coefficient is higher than the red band . As the solar zenith angle increases, the coefficient of aggregation derived by the Ross-Li model shows a linear increase trend (R ~ 2 = 0.9699), indicating that the leaf aggregation degree coefficient and zenith angle change Related.