Accurately and rapidly segmenting tree crowns from a three-dimensional (3-D) perspective is of great significance to precision forest management, and better understand the carbon and water cycles between the soil-plant-atmosphere system. However, it remains challenging to group points into individual trees from a 3-D perspective in the forest stand with highly overlapped tree crowns and abundant understory. The objective of this paper was to extract the overstory and understory of individual

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... es from terrestrial laser scanning (TLS) data considering the vertical forest structure and overlapped tree crowns processing strategy suitable for various crown shapes and sizes. Our results showed that: (1) the proposed algorithm had better performance in the low overlapping rate coniferous (F1-score: 0.96) and broadleaf (F1-score: 0.91) forest stands, while the F1-score decreased down to 0.89 and 0.65 in the high overlapping rate for coniferous and broadleaf forest stand, respectively. (2) A multi-station TLS data produced better (F1-scores: 0.85-1) segmentation results than those obtained from single-station TLS data (F1-scores: 0.67-0.83) in coniferous forest stands. (3) The vertical forest structure profiles affected the final forest 3-D segmentation accuracy. Our work provides a solid foundation for precision forestry and natural resources management.