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This study aimed to explore the feasibility of applying close-range photogrammetry in the quantitative analysis of spatial structure of mixed forests. A smartphone imagery-based method was developed to analyze the spatial structure of a coniferous-broadleaved mixed plantation in Jiufeng Experimental Forest Farm. A multi-path and multi-angle image acquisition strategy was employed to construct a three-dimensional (3D) point cloud model of the stand below the canopy. The optimal circle algorithm was utilized to identify and estimate the positions and diameter at breast height (DBH) of individual trees. The measured data of DBH, tree height, and crown width, along with DBH estimates derived from the 3D model, were used as weighting factors, and weighted Voronoi diagrams were constructed based on measured DBH, estimated DBH, and an equally weighted combination of measured DBH, tree height, and crown width. The effects of different weighting factors on key spatial structure parameters—mingling degree (M), neighborhood comparison (U), and uniform angle index (W)—were systematically analyzed. The results showed a strong correlation (R2=0. 977 2) between estimated DBH and measured DBH. For the estimated DBH of entire stand, the root mean square error (RMSE) of 1. 427 5 cm, the relative RMSE of 8. 224 1%, the deviation of 0. 503 8 cm, and the relative deviation of 2. 902 4%, which indicate the estimated DBH of the entire stand was underestimated. In addition, the results revealed similarities in the stand spatial structure units derived from different weighting factors. Although significant differences existed among some key spatial structure parameters, these did not affect the overall consistency in characterizing the stand's spatial structure. All the approaches consistently indicated that the stand exhibited moderate competition intensity, a moderate mixing degree, and a random distribution pattern.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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