Abstract:

Objective: Taking larch plantations(Larix principis-rupprechtii) in the core area of Chongli Winter Olympics as objects, analysis of stand structure characteristics and the optimization model of stand spatial structure were carried out, so as to provide scientific basis for making structure regulation measures. Method: Three sample plots with the area of 0.09 hm²(30 × 30 m) were set up and forest stand structure characteristics were analyzed based on plots measurement data. Multi-objective programming of five spatial structure parameters, including uniform angle index(W), mingling(M), crowding(C), intersection competition index(UaCI) and storey index(S), was carried out using multiplication and division method based on objective of best spatial structure. With the objective of forest spatial structure optimization, the spatial structure optimization model for stand cutting was constructed, and the effects of the models before and after cutting were compared. Result: The basal area of Larch was over 70% in the two plots and Betula platyphylla was associated species. The diameter distribution ranged from 6 cm to 26 cm, and both of them were approximately normal distribution. Height distribution was unsymmetrical, and the peak appeared at height of 14 m. The mean values of ${\bar W}$, ${\bar M}$, ${\bar C}$, UaCI and ${\bar S}$ were 0.460, 0.106, 0.918, 0.297 and 0.363 respectively. The stand was in a state of uniform distribution of trees, low species mingling, high crown competition and poor vertical structure differentiation. The thinning cutting intensity was lower than 20% after simulated cutting, and the objective function value increased by 13.62%. Values of ${\bar M}$ and ${\bar S}$ increased by 21.17% and 15.23%, whilst ${\bar C}$ and $\overline{{\rm{UaCI}}}$ decreased by 10.22% and 5.19% respectively. Conclusion: The structure of larch plantation in the area is simple with relative single tree species. The degree of tree differentiation is weak and crown competition is obvious, indicating the whole plantation shows the characteristics of pure forest of the same age. Stand structure can be significantly improved after simulated cutting, showing improved degree of mingling and relieved pressure of light competition. The spatial structure optimization model developed in the paper can provide a feasible method reference for tending and thinning for larch plantation.

Key words: spatial structural optimization model, Larix principis-rupprechtii plantation, Winter Olympics core area, cutting