Objective To optimize the structural composition and enhance the growth of Platycladus orientalis plantations, this study systematically analyzed the factors influencing canopy spatial complementarity in Platycladus orientalis plantations using handheld mobile laser scanning (HMLS) and evaluated their impacts on individual tree growth.
Method First, the applicability of HMLS in studying canopy spatial complementarity was evaluated by comparing HMLS-derived measurements with field observations. Neighborhood tree trait variation, neighborhood density, soil properties, and topographic factors were then considered as explanatory variables, and the correlation between these variables and canopy spatial complementarity were explored using linear regression model and full-subset model. Finally, structural equation modeling (SEM) was employed to analyze the role of canopy spatial complementarity in the process of variables influencing the growth of target trees.
Result (1) The diameter at breast height (DBH), tree height (TH) and crown width (CW) extracted by HMLS were significantly correlated with field-measured values (P < 0.001), demonstrating the accuracy of HMLS-derived parameters was suitable for canopy spatial complementarity studies. (2) Variations in crown shape (P < 0.001), crown size (P < 0.01), and tree height (P < 0.001) significantly contributed to canopy spatial complementarity. Stand density (P < 0.001), slope aspect (P < 0.05) and slope gradient (P < 0.05) were also observed as positive contributors. However, soil total phosphorus (P < 0.05), total potassium (P = 0.01), available phosphorus (P < 0.05), available potassium (P < 0.05), and soil bulk density (P < 0.05) negatively affected canopy spatial complementarity. The full-subset model indicated that neighborhood tree trait variation and soil factors were the primary drivers of canopy spatial complementary variation, explaining 40.8% and 31.6% of variance, respectively. (3) Canopy spatial complementarity was found to significantly promote the DBH growth of target trees (P < 0.01). SEM results revealed that neighborhood tree trait variation, neighborhood density, soil properties and topographic factors indirectly influenced target tree growth through their effects on canopy spatial complementarity.
Conclusion This study highlights the critical role of canopy spatial complementarity in promoting the growth of Platycladus orientalis. It is recommended to prioritize planting Platycladus orientalis on shaded slopes with nutrient-rich soils. For existing Platycladus orientalis plantations, regular pruning to optimize crown structures and increasing vertical difference among neighboring trees can effectively enhance DBH growth.
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