基于交角和密集度的竞争指数构建及评价

Establishment and Evaluation of Tree Competition Index Based on Intersection and Crowding

【目的】以蒙古栎次生林和云冷杉过伐林为研究对象,构建新的基于交角和密集度的竞争指数,为更好表达蒙古栎次生林和云冷杉过伐林林木间的竞争状况提供依据。【方法】在吉林省汪清林业局塔子沟和金沟岭林场分别选择具有代表性的3块1 hm^(2)蒙古栎次生林和3块1 hm^(2)云冷杉过伐林样地,基于2013和2018年2期调查数据,构建基于交角和密集度的竞争指数(caCI),采用优势度分析法确定优势树种,并建立优势树种的单木断面积生长量模型评价竞争指数caCI与Hegyi、aCI和uaCI的优劣。【结果】竞争指数caCI与Hegyi、aCI和uaCI呈显著正相关关系。断面积生长量线性回归模型和混合效应模型表明,林木断面积生长量与初始断面积呈正相关关系,与竞争指数呈负相关关系,暗示影响生长量的主要因素是林木初始大小,而林木竞争也会影响林木生长。优势树种嵌套于样地的2水平线性混合效应模型的拟合精度优于回归模型,反映出不同树种的生长趋势差异显著,而样地影响较小。模型中带竞争指数的拟合效果较不带竞争指数的拟合效果有所提升,与Hegyi、aCI和uaCI相比,caCI在云冷杉过伐林中表现最佳,在蒙古栎次生林中效果次之,说明竞争指数caCI适合空间结构更复杂的林分。【结论】基于交角和密集度的竞争指数caCI能够有效反映蒙古栎次生林和云冷杉过伐林林木间的竞争状况,尤其是林木结构更为复杂的天然混交林。

【Objective】In order to provide a basis for better calculating the competition status of secondary forest of Mongolian oak and over-logged spruce and fir forest,a new competition index was constructed by adding the crowding to the competition index based on intersection angle.【Method】Three representative plots of Mongolian oak secondary forest and three plots of over-logged spruce and fir forests with an area of 1 hm^(2) were selected in Tazigou and Jingouling forest farm of Wangqing Forestry Bureau,Jilin,China.The stands were investigated in 2013 and 2018,respectively.The competition index caCI based on intersection and crowding was constructed,dominant tree species were determined by dominance analysis,and the individual tree basal area growth model of dominant tree species was established to evaluate the competition index caCI,Hegyi,aCI and uaCI.【Result】The results showed that caCI had a significant positive correlation with Hegyi,aCI and uaCI.The regression model and linear mixed-effects model of basal area growth showed that the basal area growth was positively correlated with the initial basal area,and negatively correlated with the competition index,suggesting that the major factor affecting the increment was the initial size of trees and that the competition among trees also had an effect on tree growth.The fitting accuracy of the linear mixed effect model was better than that of the regression model,which indicated that the growth dynamic of different tree species was significantly different,but the influence of the sample plot was slight.The fitting effect of the model with competition index was better than that of the model without competition index.Compared with Hegyi,aCI and uaCI,caCI showed the best performance in over-logged spruce-fir forests,followed by secondary forest of Mongolian oak,which indicated that caCI was suitable for forest with more complex spatial structure.【Conclusion】The competition index caCI could effectively reflect the competition of secondary forest of Mongolian oak and over-logged spruce-fir forest,especially in the natural mixed forest with more complex forest structure.