柏木人工林空间结构特征及其评价

【目的】从林木结构单元和林分整体维度对柏木林分空间结构进行评价,分析空间结构参数二元分布以探究空间结构参数间的生物学意义,为柏木人工林结构化森林经营和林分质量提升提供理论参考。【方法】基于京山市太子山林管局两种密度柏木人工林4个标准地的实测数据,计算分析角尺度W_i、大小比数U_i、混交度M_i和林层参数S_i,采用CRITIC赋权法确定林木空间结构参数权值,用乘除法对各参数进行多目标规划,确立林木空间结构等级;采用林分空间结构参数(FSSI)和林分空间结构距离(FSSD)评价林分结构稳定性;应用二元分布解释空间结构参数间的生物学意义。【结果】(1)标准地A和C林木为随机分布,标准地B和D林木主要为均匀分布;4个标准地林木状态中庸;林分树种以零度混交为主;林分成层性均很弱。(2)4个标准地林木所在林分的空间结构Ⅰ级占50%以上,Ⅴ级占比少于3%;FSSI均低于55,FSSD均大于82,整体林分空间结构不理想。(3)二元分布表明,标准地A、C和D林木W-U交叉频率和W-M交叉频率在随机分布(W=0.50)时最...

Spatial Structure Characteristics and Evaluation of Cupressus funebris Plantations

【Objective】The research purpose is to explore the biological significance of spatial structure parameters,so as to propose a theoretical reference for structured forest management and stand quality improvement of Cupressus funebris Plantations by evaluating the spatial structure of Cupressus funebris stands from the perspectives of plants’spatial structure and stands as a whole,and analyzing the bivariates distribution of spatial structure parameters.【Method】Uniform angle(W_i),neighborhood comparison(U_i)and mingling degree(M_i)and stand layer indexe(S_i)were computed and analyzed based on the surveyed data in Cupressus funebris Plantations in 2 different densities in Taizishan,Jingshan City.Criteria Importance through Inter-criteria Correlation(CRITIC)was adopted to assign each stand structure parameter a weight,and Multiplication Division Method was employed for making a multi-objective programming with the weighted parameters,and consequently the evaluation classes of stand spatial structure were put forward.Forest Spatial Structure Index(FSSI)and Forest Spatial Structure Distance(FSSD)were also used for assessing the whole stand structure.The bivariate distribution was analyzed to explore the biological significance of spatial structure parameters.【Result】(1)The plants of sample plot A and C were in random distribution,while the plants of sample plot B and sample plot D were mainly evenly distributed;the plants of the 4 sample plots were in moderate competition;the mingling indexes of 4 stands were close to zero;the stand layers were simple.(2)The forest spatial structure surrounding individual trees falling in Class I was more than 50%,but that in Class V less than about 3%;FSSI of the 4 sample plots were lower than 55,and FSSD of the all plots were shorter than 82,indicating the spatial structure of the 4 sampled Cupressus funebris stands was below perfection.(3)The bivariate distribution revealed that The W-U cross frequency and W-M cross frequency of sample plot A,C and D were the highest when trees were randomly distributed(W=0.50),while the W-U cross frequency and W-M cross frequency of trees in sample plot B were the highest when trees were evenly distributed(W=0.25);The U-M cross frequency of trees of the 4 sample plots reached the maximum when the mixing degree U=0.【Conclusion】The main causes of the unsatisfactory spatial structures are that the mean uniform angle deviates slightly from random distribution,the neighborhood comparison is close to moderate competition,and the mingling degree is extremely low.The random distribution of Cupressus funebris is conducive to improve the mixing degree of tree species and slow down the neighborhood comparison difference between various trees.Increasing the mixed degree of tree species is conducive to slowing down the competition among trees.