基于MODIS二向反射分布函数（BRDF）模型参数产品数据，利用4-scale模型建立查找表，以中国东北大兴安岭加格达奇地区为研究区，反演森林背景反射率，并分析不同森林类型二向反射与背景反射率特性及其季节变化。研究结果表明：（1）研究区针叶林和混交林二向反射特征较为相似，夏季阔叶林在红光波段的二向反射率值均低于针叶林和混交林，而在近红外波段则相反；不同森林类型二向反射率均存在明显的季节变化，其中阔叶林二向反射率季节变化最为明显；（2）研究区夏季森林背景反射率在红光波段较低，均在0.1以下，近红外波段背景反射率普遍高于0.3，且空间差异较大；（3）不同森林类型的背景反射率季节变化趋势大致相同，但变化幅度存在差异：阔叶林的背景反射率值季节差异最大，尤其在近红外波段。

In this study, forest background reflectivity was retrieved based on a four-scale model in Jiagedaqi District, northeastern China by using the bidirectional reflectance distribution function product from moderate resolution imaging spectroradiometer. The seasonal variation of forest canopy Bidirectional Reflectance Distribution Function (BRDF) and background reflectivity were then observed. The results showed that: (1) in the study area, the characteristics of bidirectional reflectivity of the mixed and coniferous forests are similar. In summer, the BRDF of the broadleaf forest was lower than that in the coniferous forest and the mixed forest in the red band, with the opposite trend in the near-infrared band. The BRDF of different forest types presents obvious seasonal variation, especially in the deciduous forest area. (2) The background reflectivity in the red band was low, ranging from 0 to 0.1 in the study area. The background reflectivity in near-infrared band was mostly more than 0.3 with high spatial variation. (3) The trends of the seasonal variation of background reflectance in different forest types were similar. However, the amplitudes of the seasonal variation in different forest types differed: the variation of background reflectance of the broadleaf forest was the largest, especially in the near-infrared band.