不同良种与初植密度杉木林分密度指标动态特征

Dynamic Characteristics of Stand Density Measure of Chinese Fir(Cunninghamia lanceolata) Plantations with Different Improved Varieties and Initial Planting Densities

[目的]探讨不同良种和初植密度杉木林分密度指标的动态特征,筛选适宜于杉木林分的密度指标,为杉木人工林密度管理提供依据。[方法]利用8年生杉木良种和密度互作试验林逐年定位观测数据,分析树冠竞争因子(CCF)、林分密度指数(SDI)、优势高—营养面积比(Z)这3个林分密度指标在不同良种和不同初植密度下的动态变化规律,并进行密度指标对初植密度和林龄的线性回归分析。[结果]在相同良种水平、不同初植密度下,3种林分密度指标随林龄增长的动态变化规律一致,均为随林龄增加而增大,低初植密度下,密度指标随林龄增长拟合直线斜率较小,随初植密度增大,拟合直线斜率增大,反映初植密度越大的林分对林木间竞争激烈程度的影响更强;同一林龄下,均随密度增大而增大,不同密度间差异达极显著水平;在相同初植密度、不同良种水平下,3种密度指标的良种效应差异均不显著,且不存在良种和初植密度的交互作用。[结论]3种林分密度指标在一定程度上可以反映密度信息,在5000~6667株·hm^(-2)的密度范围内,CCF和SDI在不同密度间差异均未达显著水平,此密度范围内难以体现不同密度之间的差别,而Z在研究设置的整个密度范围内不同密度间差异均达显著水平,能明显表示出不同密度之间的差别,适用的密度范围更广,且不含参数,计算简单,可以很好地用于杉木人工林分生长模拟和密度管理。

[Objective] To study the dynamic characteristics of stand density measures of Cunninghamia lanceolata plantation at different improved varieties and initial planting densities in order to select the appropriate density index and provide a basis for density management of Cunninghamia lanceolata plantation. [Method] Based on 8-year positioning observation data of interactive test forest, the dynamic characteristics of three stand density measures, including crown competition factor(CCF), stand density index(SDI), ratio of dominant height to nutrient area(Z), with different improved varieties and initial planting densities and the linear regression analysis between the three stand density measures and initial planting density and stand age were analyzed. [Result] The law of dynamic changes of the three stand density measures were consistent with age with same improved variety and different initial planting densities, which increased with age. Under lower initial planting density, the slope of the fitting line of stand density measures was small, and became larger with the increase of initial planting density. The results showed that the higher the initial planting density, the stronger the competition intensity. Under same stand age, all the density measures increased with the initial planting density. There were quite significant differences among planting densities. Under the same initial planting density and different improved varieties, the improved varieties had no significant effect on the three stand density measures, and there was no interaction between the improved varieties and initial planting densities. [Conclusion] The three stand density measures can reflect density information to some extent. In the density ranging from 5 000 to 6 667 trees·hm-2, the difference is not significant among initial planting densities in CCF and SDI, and it is difficult to reflect the difference between densities in this range. But the difference among densities reaches a significant level in Z in the whole density range. The Z can show the difference at different densities clearly,and has a larger applicable density, with no parameter and easy calculation. Therefore, it can be well applied to growth modeling and density management in Chinese fir plantation.