Exploring the Role of Canopy Triangular Units in Analysing Canopy Effects on Saplings

On the distribution and growth of saplings, canopy structure has a considerable influence. However, traditional canopy metrics are inadequate in irregular stands due to their inability to consider the heterogeneous horizontal and vertical distributions of canopy structure. To surmount this inherent limitation and achieve an advanced comprehension of the three-dimensional attributes characterizing the canopy, we introduce the innovative framework of canopy triangular units. This conceptual framework encapsulates a comprehensive array of multifaceted information, encompassing intricate forest layer intricacies such as tree height differentials, intricate competitive attributes exemplified by disparities in diameter at breast height and crown width, alongside precise geospatial location information. In this study, we formulated geometrically organized triangular networks based on precise tree coordinates, subsequently delineating ten distinct triangular unit categories predicated upon diameter at breast height measurements: DT (3,0,0), DT (2,1,0), DT (2,0,1), DT (1,2,0), DT (1,1,1), DT (1,0,2), DT (0,3,0), DT (0,2,1), DT (0,1,2), and DT (0,0,3). The values enclosed within parentheses represent the quantities of large trees, medium trees, and small trees contained within each respective triangular unit type. Our analytical framework commenced with an in-depth evaluation of the differences in quantities and areas across these diverse triangular unit types. Subsequent to this, these identified triangular unit categories underwent systematic classification into three distinct groups, thereby enabling meticulous investigation into variations within the spatial dispersion of sapling populations. Furthermore, a comprehensive suite of seven triangular unit variables encapsulating the multifaceted three-dimensional attributes of the canopy was established. This enabled a comprehensive investigation into their nuanced relationships with the growth patterns of saplings. Analyzing the triangular unit types in the three sample plots, a clear pattern emerged: maximum occurrences of DT (0,1,2) units alongside minimal DT (3,0,0) occurrences. Moreover, saplings show a clear preference for triangular unit types with low abundance of large trees. The correlation analysis revealed a significant positive link between the individual basal area increment of saplings and relevant parameters - opening area, triangular perimeter, and triangular area. As a practical implication, during the replanting of saplings, the selective choice of triangular units with fewer large trees can be prioritized to support their growth and development. To optimize sapling growth, selective tree cutting may be deemed necessary to create new triangular units and expand the opening area. These findings emphasize the significance of accounting for the framework of canopy triangular units in the development of management strategies aimed at improving both sapling quantity and growth.