基于结构方程模型的杉木公益林林分空间结构评价  

Evaluation of Stand Spatial Structure of Cunninghamia lanceolata Public Welfare Forest by Using Structural Equation Model

作　　者：赵文菲 曹小玉[1,2] 谢政锠 庞一凡 孙亚萍 李际平 莫永俊[1] 袁达 Zhao Wenfei;Cao Xiaoyu;Xie Zhengchang;Pang Yifan;Sun Yaping;Li Jiping;Mo Yongjun;Yuan Da(College of Forestry,Central South University of Forestry&Technology,Changsha 410004;Key Laboratory of Managment and Testing of Forest Resources in Southern China,National Forestry and Grossland Administration,Changsha 410004)

机构地区：[1]中南林业科技大学林学院,长沙410004 [2]南方森林资源经营与监测国家林业与草原局重点实验室,长沙410004

出　　处：《林业科学》2022年第8期76-88,共13页Scientia Silvae Sinicae

基　　金：湖南省教育厅重点科学研究项目(19A518);“十二五”国家科技支撑计划专题(2012BAD22B0505);湖南省研究生科研创新项目(CX20220712)。

摘　　要：【目的】综合评价杉木公益林林分空间结构,确定不同龄组林分空间结构现状,为制定精准可行的林分空间结构优化和经营措施提供理论依据。【方法】以湖南省平江县芦头实验林场杉木公益林为研究对象,基于30块样地实测数据,采用4株木法确定林分空间结构单元,选取全混交度、角尺度和空间密度指数作为内生潜变量水平空间结构的观测变量,林层指数、开敞度和交角竞争指数作为内生潜变量垂直空间结构的观测变量,以林分空间结构为外生潜变量,构建林分空间结构评价结构方程模型,模型输出的路径系数通过归一化处理确定各指标权重,在此基础上对林分空间结构进行综合评价。【结果】1)林分空间结构评价结构方程模型的卡方自由度比值(χ^(2)/df)为1.708,介于1~3之间,比较拟合指数(CFI)、非正规化拟合指数(NNFI)和递增拟合指数(IFI)分别为0.944、0.924和0.946,均大于0.90,各拟合指数均符合适配参考值,模型整体适配度良好;2)内生潜变量水平空间结构、垂直空间结构的权重分别为0.5229、0.4771,对外生潜变量林分空间结构的影响大致相同,空间密度指数所占权重最高,是影响林分水平空间结构的关键因素,开敞度和交角竞争指数所占权重相等,是影响林分垂直空间结构的关键因素;3)杉木幼龄林、中龄林和近熟林的综合得分分别为0.3781、0.4526和0.3775,3个龄组的林分空间结构等级处于Ⅱ、Ⅲ等级。总体来看,研究区杉木公益林林分空间结构未达到理想状态,林分空间结构较差,树种混交程度低,接近零度混交至弱度混交状态,林分拥挤程度中等,林木透光条件一般,林层结构单一,但林木间竞争强度较弱,且空间分布格局较好,处于均匀至近似随机分布状态。【结论】林分水平空间结构和垂直空间结构均是影响林分空间结构的关键因素,空间密度指数是影响林分水平空间结构【Objective】The spatial structure of Cunninghamia lanceolata public welfare forest was comprehensively evaluated,and the current situation of spatial structure of different age groups was determined,in order to provide theoretical bases for formulating accurate and feasible stand spatial structure optimization and management measures.【Method】Taking the Cunninghamia lanceolata public welfare forest in Lutou experimental forest farm of Pingjiang county,Hunan Province as the research object,based on the measured data of 30 sample plots,the stand spatial structure unit was determined by four adjacent trees.Taking the total mingling degree,uniform angle index and spatial density index as the observed variables of the horizontal spatial structure of endogenous latent variables,taking the storey index,open degree and angle competition index as the observed variables of the vertical spatial structure of endogenous latent variables,and taking stand spatial structure as the exogenous latent variables,the stand spatial structure evaluation structural equation model was constructed.The path coefficient output from the structural equation model was normalized to determine the weight of each index.On these bases,the stand spatial structure was comprehensively evaluated.【Result】1)For the structural equation model of the evaluation of stand spatial structure,the normed Chi-square(χ^(2)/df)was 1.708,which was between 1-3.The values of comparative fit index(CFI),non-normed fit index(NNFI)and incremental fit index(IFI)were 0.944,0.924 and 0.946,respectively,which were all greater than 0.90.All the fitting indexes conformed to the appropriate reference value,and the overall fitness of the model was good.2)The weights of horizontal spatial structure and vertical spatial structure of endogenous latent variables were 0.5229 and 0.4771 respectively,and their effects on the stand spatial structure of exogenous latent variables were roughly the same.The spatial density index of the observed variables was the key factor affecti

关 键 词：杉木公益林 林分空间结构 结构方程模型 指标权重 

分 类 号：S757[农业科学—森林经理学]