基于π值法则的油松人工林稳定性与空间结构关联性研究

Research on relationship between stability and spatial structure of Chinese pine plantation based on rule of π value

【目的】研究林分空间结构与稳定性的关系是开展结构化森林经营的前提,旨在探索空间结构对林分稳定性的影响特征,为结构化森林经营提供支持与理论依据。【方法】以黄龙山油松人工林为研究对象,通过设置典型样地,采用最优林分的π值法则,选取10项稳定性指标进行稳定性评价,利用典型相关分析、逐步线性回归分析等方法研究空间结构(包括混交度M、角尺度W和Hegyi竞争指数CI)与林分稳定性ω的关联机制。【结果】1)林分稳定性ω平均值为0.18,变异系数为36%,总体评价结果偏差;混交度M平均值为0.26,变异系数为79%,研究区油松林分物种入侵差异大。2)典型相关分析显示,空间结构指数(包括混交度M、角尺度W和Hegyi竞争指数CI)与稳定性评价指标体系在整体上存在很强的线性相关,典型相关系数可达0.95。3)Pearson相关性分析中,W、M和CI均与ω强烈相关,相关系数分别为-0.5、0.61和-0.73。W与林分健康状态呈极显著负相关,相关系数为-0.63;M与树种多样性呈极显著正相关,与林分长势呈极显著负相关,相关系数分别为0.86、-0.66;CI与林分健康、林分密度呈极显著负相关,相关系数分别为-0.60、-0.57。4)逐步回归分析显示,混交度和林木竞争是影响稳定性的主要因素;由标准化系数可看出,林木竞争(-0.58)对稳定性的影响比混交度(0.39)大。【结论】空间结构与林分稳定性在整体上显著相关;林分混交程度显著提高林分稳定性,但是会削弱优势林木长势;团状分布格局加大了林木竞争,不利于林分稳定性。在结构调控中应适当提高林分混交程度,对竞争强度进行调整时可以连带调整林分的团状分布格局,从而提高林分稳定性水平。

【Objective】Understanding the relationship between spatial structure and stability of stands is the premise of structure-based forest management. This research was carried out to clarify the influencing characteristics between spatial structure and stand stability. Hopefully, this research will provide theoretical basis for structure-based forest management.【Method】Typical sample plots were set up in Chinese pine plantation in Huang long mountain. Ten stability indices were analyzed using π value of the best stand state to evaluate the stand stability. Then canonical correlation analysis and stepwise regression analysis were used to illustrate the relationship between spatial structure(which includes uniform angle index W, mingling degree M and Hegyi competition index CI) and stabilityω.【Result】1) The stand stability was low with an average ω value of 0.18 and coefficient of variation was 36%. The average M was 0.26 and coefficient of variation was 79%, which indicates the species in plantation varies greatly. 2) The spatial structure and stability indices were significantly correlated with a canonical correlation coefficient of 0.95. 3) As shown in Pearson correlation analysis W, M and CI was significantly related to ω with coefficients of-0.50, 0.61 and-0.73 respectively. W had significant relation with tree health with a correlation coefficient of-0.63. Meanwhile M was significantly correlated to tree species diversity and stand growth status;the correlation coefficients were 0.86 and-0.66 respectively. A significant correlation between CI, and tree health and stand density was also found with correlation coefficients of-0.60 and-0.57. 4) As shown in stepwise regression analysis M and CI were the main factors affecting stability. The standardization coefficient of CI was larger than that of M, indicating that stand competition has greater influence on stand stability than mingling degree.【Conclusion】Overall, the spatial structure and stand stability are significantly correlated. Higher mingling degree significantly improves the stability of the stand, but weakens the growth of dominant trees. Cluster distribution pattern increases the competition of trees, which is not conducive to the stability of the stand. The degree of forest mixing should be properly improved in the structural regulation. Besides, the cluster distribution pattern of the stand should be avoided when adjust the competition intensity, in order to improve the stability level of the stand.