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Scientia Silvae Sinicae ›› 2025, Vol. 61 ›› Issue (2): 93-100.doi: 10.11707/j.1001-7488.LYKX20240250

• Research papers • Previous Articles     Next Articles

Tree Crown Width Model, Stand Density Model and Their Relationships for Natural Larch

Weisheng Zeng*(),Xueyun Yang,Ying Pu   

  1. Academy of Inventory and Planning, National Forestry and Grassland Administration Beijing 100714
  • Received:2024-05-06 Online:2025-02-25 Published:2025-03-03
  • Contact: Weisheng Zeng E-mail:zengweisheng0928@126.com

Abstract:

Objective: This study aims to develop models for tree crown width(CW) and stand density(SD), as well as a combined model integrating both. By exploring the correlation between CW model and SD model, this research provides a scientific basis for further studies on stand density management and guidance for forest management practices. Method: Using the measurement data of 600 representative sample trees of larch collected throughout the whole country of China, and the data of 1273 permanent plots in natural larch forests from the 9th national forest inventory, the CW model and the SD model of larch were established by using nonlinear regression and logarithmic regression estimation methods. Based on the analysis of the relationship between CW model and SD model, a multivariate nonlinear regression method with dummy variables was used to establish the simultaneous models, and the maximum stand density line was determined. Result: The results showed that CW was positively correlated with diameter at breast height (DBH); the determination coefficient R2 of CW model for larch was higher than 0.76, the standard error of estimate (SEE) was 1.03 m, and the mean prediction error (MPE) was 2.16%. The ratio of CW-DBH decreased with the increase of DBH, from 0.53 at 2 cm to 0.23 at 20 cm and then slowly to 0.17 at 50 cm. The SD was negatively correlated with mean DBH; the R2 of SD model for larch forests reached to 0.88, the SEE was 147 stems per hectare, and the MPE was 2.58%. There was a 2-fold negative correlation between the two power parameters of SD model and CW model, and the slope parameter from the simultaneous models is ?1.384, which can be regarded as the average value of the slopes of self-thinning lines of natural larch forests in China. Conclusion: It is a feasible new approach to use multivariate regression method for estimating the slope parameter of the stand density index (SDI) based on the correlation between SD model and CW model. This is of practical significance to study the SDI of other tree species and to guide the stand density management and forest scientific management.

Key words: tree crown width, stand density, maximum density line, multivariate regression, larch

CLC Number: