长白山云冷杉针阔混交林林木空间利用率混合模型

Mixed model of forest space utilization in spruce-fir coniferous and broadleaved mixed forest of Changbai Mountains, northeastern China

【目的】建立林木空间利用率模型,为天然混交林中不同树种间生产力的比较提供依据,为单木成熟的判断提供参考。【方法】利用林木生长量与树冠大小比值定义林木空间利用率,以长白山地区云冷杉针阔混交林为研究对象,基于20块标准地的2 268株单木数据,建立林木空间利用率混合模型,拟合各树种的空间利用率。【结果】(1)备选指标中蓄积生长量和树冠投影面积之比与胸径相关系数最高,适宜作为计算指标。(2)通过逐步回归,最终选定林木胸径、胸径平方(代表胸高断面积)、树高、冠幅、样地蓄积、针阔比、坡向坡度、竞争指标作为林木空间利用率基础模型的自变量。(3)确定按树种分组,包含胸径平方及截距随机效应参数、指数函数异方差结构的混合模型,经检验,混合模型在建模数据及检验数据中的表现均略优于一般线性模型。(4)利用所构建的混合效应模型,对研究数据进行拟合预测,各树种空间利用率最高时期的胸径分别为云杉约40 cm,冷杉、落叶松、红松、中阔组约37 cm,慢阔组约32 cm。【结论】林木利用率模型得到的数量成熟是以单位营养空间的生产力为基础的,使不同树种间的比较更为合理,且计算结果符合一般林学规律,可以作为该地区云冷杉针阔混交林判定单木成熟及优化林分结构的参考依据。

[Objective] In this paper, the forest space utilization model was established to provide the basis for the comparison of productivity among different tree species in the natural mixed forest, and provide reference for the judgement of tree maturity. [Method] The combination of tree growth and canopy size was used to define the forest space utilization. Based on the 2 268 individuals of 20 standard sites, which located in spruce-fir and broadleaved mixed forests in Changbai Mountain area of northeastern China, a mixed-effects model of forest space utilization was established to fit the spatial utilization of different species. [Result](1) The correlation coefficient between DBH and the ratio of volume growth to the crown projection area was the highest, so it is suitable to be the calculation index.(2) Through the stepwise regression, the tree DBH, DBH square(represent area), tree height, crown width, plot accumulation,proportion of coniferous trees, slope gradient and competition index were selected as the independent variables of forest space utilization.(3) Mixed effects model was developed, including the DBH square and intercept random effect parameters by species groups and the exponential function heteroscedasticity structure. The results showed that the mixed effects model was better than the general linear model both in the modeling data and the test data.(4) Using the mixed effect model to predict the research area data, the DBH of the highest spatial utilization of each tree species was obtained: spruce(Picea koraiensis) was about40 cm;fir(Abies holophylla), Korean pine(Pinus koraiensis), larch(Larix olgensis), and medium-speed broadleaf trees were about 37 cm;slow broadleaf trees were about 32 cm. [Conclusion] The mature DBH obtained from the forest utilization model is based on the productivity of the unit nutrient space, so that the comparison between different tree species is more reasonable. The calculation results are in accordance with the general forest rule, so it can be used as a reference to judge the tree maturity, optimize the stand structure in the coniferous and broadleaved mixed forest in that area.