Purpose To study the structural characteristics of Pinus massoniana plantations distributed in the subtropical-warm temperate transition zone at the northern distribution edge, providing a basis for the sustainable management of forest.
Methods P. massoniana plantations in Jigongshan National Nature Reserve was used as the research object, and six probability distribution models were used to study diameter structure patterns. Five integrated spatial structure indices (SPV, Q, FSI, CDEV, CAPV) were constructed through combined analytic hierarchy process-entropy weight method analysis of six structural parameters, including complete mingling (Mc), neighborhood comparison (U), uniform angle (W), stand layer index (S), open comparison (OP) and competition index based on intersection angle and density (caCI), to explore the spatial structure characteristics of P. massoniana plantations under different stand densities.
Results 1) Gamma distribution showed the best fitting effect for the stand diameter structure under different stand densities. 2) According to the correlation between FSI and the average value of each spatial structure parameter, the importance of each stand spatial structure parameter was ranked as Mc>U>S>W>OP>caCI. 3) The evaluation results of five comprehensive indices of stand spatial structure showed that the spatial structure of low-density stand was relatively close to the ideal state, with the best spatial structure; the spatial structure of high-density stand was the worst, and there was some irrationality in their diameter structure and the degree of species mixing was poor.
Conclusion It is necessary to carry out tending and regeneration of P. massoniana plantations under high density to improve stand structure. The study can provide a certain reference for the structural optimization and adjustment and the formulation of sustainable management measures of coniferous forests in climate transition areas.
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