Spatiotemporal variations of forest canopy gaps are essential indicators for both forest dynamic monitoring by capturing their size and location variations and forest ecosystem management for tree seedling regeneration through altering the radiation regime within and under forest canopies. To differentiate the effects of forest canopy gaps on forest three-dimensional (3-D) structure and direct incoming solar radiation, we proposed two novel concepts named physical forest canopy gap (PCG) and physiological forest canopy gap (POCG). Using aerial laser scanning (ALS) data, this study developed ALS-based methods of extracting and characterizing spatiotemporal variations of the PCG and POCG in a natural homogeneous forested area. The ALS-based PCG and POCG results were validated using visual-based interpretation and field-measured data, respectively. The overall accuracy was all over 0.80 and Kappa coefficients all over 0.70 for PCG extraction. The coefficient of determination between the ALS-based POCG area and field-based one was 0.86 (n = 16, p < 0.01), and the root mean square error was 16.28 m². Spatiotemporal variations of forest canopy gaps included variations of their sizes and locations and the sunlit areas within them. This study provided a solid foundation for forest dynamic monitoring and forest ecosystem management.

森林冠层间隙的时空变化是森林动态监测的重要指标，通过捕捉它们的大小和位置变化，以及通过改变森林冠层内部和下方的辐射状况来进行树苗再生的森林生态系统管理。为了区分森林冠层间隙对森林三维 (3-D) 结构和直接入射太阳辐射的影响，我们提出了两个新概念，称为物理森林冠层间隙 (PCG) 和生理森林冠层间隙 (POCG)。本研究使用航空激光扫描 (ALS) 数据，开发了基于 ALS 的方法来提取和表征天然均质林区中 PCG 和 POCG 的时空变化。分别使用基于视觉的解释和现场测量数据验证了基于 ALS 的 PCG 和 POCG 结果。PCG 提取的总体准确度均超过 0.80，Kappa 系数均超过 0.70。基于ALS的POCG区域与基于现场的POCG区域的决定系数为0.86（n = 16，p < 0.01），均方根误差为16.28 m² . 森林冠层间隙的时空变化包括它们的大小和位置以及其中的阳光照射面积的变化。该研究为森林动态监测和森林生态系统管理提供了坚实的基础。