北京地区油松人工林树冠竞争因子的测算与分析

使用广泛分布于北京地区,且具有典型代表性的116块油松(Pinus tabulaeformis)人工近熟林、成熟林样地数据(林龄为31～53 a),研究并确定了其树冠竞争因子。结果表明:近熟林阶段油松人工林生长渐趋稳定,成熟期有分化趋势;冠幅指标比胸径、树高指标对环境和竞争的响应更为敏感,是研究油松人工林生长的重要指标;建立了油松优势木胸径—冠幅线性模型和二次方模型,模型相关指数R2分别为0.662 0和0.660 8;确定线性模型为研究树冠竞争因子的模型,模型通过了t检验,残差呈正态分布;确定油松人工近、成熟林树冠竞争因子上限值为300,该值随树龄的增长趋于稳定;使用树冠竞争因子分析了116块林分的郁闭情况,结果显示15%的样地已经郁闭,郁闭时密度约为580株/hm2,剩余85%的林分需要进行不同程度的抚育。

Analysis and Calculation of Crown Competition Factor in Pinus tabulaefomis Plantations in Beijing

A study was performed to calculate the Crown Competition Factor(CCF) in typical near-mature and mature plantations of Pinus tabulaeformis widely distributed in Beijing by setting up 116 sample plots.Results showed that the growth of the near-mature plantations of P.tabulaeformis tended to be stable,while differentiation trends were observed in the mature plantations.Crown width is an important index for the research of P.tabulaeformis plantations because it is more sensitive to the changes of environment and competition status than DBH and tree height.A linear model and a quadratic model for DBH and crown width of dominant trees were built with correlation coefficients of 0.662 0 and 0.660 8,respectively.The linear model was finally used to calculate the CCF,and also passed the t-test.The residual errors showed normal distribution simultaneously.The upper limit of CCF was 300 for the near-mature and mature plantations,and it became stable with age.Canopy densities of the 116 sample plots were analyzed in terms of the CCF.The results indicate that nearly 15% of the plantations have already closed with a density of 580 individuals per hectare,and 85% of the plantations need different degrees of tending timely.