杨桦次生林林分空间结构参数多元分布研究

Multivariate distribution of spatial structure parameters of Populus davidiana-Betula platyphylla secondary forest

【目的】运用林分空间结构参数多元分布,系统描述和分析金沟岭林场两种起源(造林失败地天然更新和火灾迹地天然更新)的杨桦次生林林分空间结构特征,为森林经营管理和林分结构优化调整提供有力手段,以期促进林分演替。【方法】每木调查和空间定位6块样地(面积均为30 m×30 m)的林木。利用RStudio forestSAS包计算各样地的空间结构参数,包括角尺度、大小比数、混交度和密集度,统计各起源的频率分布,运用Origin 2018建立结构参数的多元分布图。【结果】杨桦次生林的零元分布表明,两种林分整体呈聚集分布、混交较好的中庸生长状态,而起源Ⅱ较起源Ⅰ密集;一元分布表明,林分内大多数林木呈混交良好、密集或很密集、各大小比数等级占比相近的随机分布。分树种来看,起源Ⅰ中,山杨生长发育良好,绝大多数处于优势及亚优势生长状态;白桦、水曲柳和枫桦整体上均大致处于中庸生长状态。起源Ⅱ中,山杨和白桦优势木多,劣势木少,总体生长发育良好。二至四元分布表明,结构参数的各种组合下,林木大多表现为混交良好或随机分布状态。【结论】相较于传统的利用结构参数零元分布和一元分布描述林分空间结构,运用多元分布描述杨桦次生林林分结构特征是对其经营管理和结构优化的有效方法,蕴含的信息更为丰富和清晰。同时,也是具有可操作性的采伐木遴选方法。

[Objective]This paper aims to systematically describe and analyze the spatial structure characteristics of Populus davidiana-Betula platyphylla secondary forest of two origins(natural regeneration of failed afforestation area and fire slash)in Jingouling Forest Farm,Jilin Province of northeastern China using multivariate distribution of stand spatial structure parameters,so as to provide powerful means for forest management and optimization of stand structure and promote forest succession.[Method]Six sample plots(30 m×30 m)of trees were surveyed and located.RStudio forestSAS package was used to calculate the spatial structure parameters,including uniform angle index,neighborhood comparison,mingling degree and crowding degree of each sample plot,and calculate the frequency distribution of each origin,using Origin 2018 to establish multivariate distribution map of structural parameters.[Result]The average values of Populus davidiana-Betula platyphylla secondary forest showed that the two kinds of forests were in the middle growth state of aggregation distribution and good mixture,while originⅡwas denser than originⅠ.The univariate distribution showed that most of the trees in the forests were randomly distributed,well mixed,denser or very denser,and each neighborhood comparison occupied nearly.In origin I,Populus davidiana grew well,most of them were in the dominant and sub-dominant growth state,while Betula platyphylla,Fraxinus mandshurica and Betula costata were generally in the middle growth state.In origin II,Populus davidiana and Betula platyphylla had more dominant trees and less inferior ones,and they grew well in general.Among the univariate distribution,trivariate distribution and quadrivariate distribution,it showed that under various combinations of structural parameters,most of the trees were well mixed or randomly distributed.[Conclusion]Compared with the traditional use of structural parameters of average values and univariate distribution,the use of multiple distribution to describe the structural characteristics of Populus davidiana-Betula platyphylla secondary forest is an effective method to optimize its management and structure,which contains more abundant and clear information.At the same time,it is also an operable method for selection of cutting woods.