高立地指数下杉木生长量及材种结构的立地及密度效应

Effects of Site Quality and Stand Density on Growth and Timber Assortment Structure of Chinese fir under High Site Index

[目的]探讨立地质量和林分密度对杉木人工林生长量及材种结构的影响,为杉木大径材培育提供理论依据。[方法]以林龄28~36年生的杉木人工林为研究对象,按上、中、下不同坡位以及不同坡向设置63块标准样地,调查林分生长量及林分基本情况,通过相关性分析和回归拟合分析进行数据处理和分析。[结果]当林分密度相近时,立地指数越高,培育相同年限所获得的单株材积、蓄积量和大径材出材率越高;同一立地条件下,在一定的密度范围内林分树高、胸径、单株材积和大径材出材率随密度增加而减小,蓄积量随密度增加而增大;立地指数相同时,密度对胸径生长分化的影响大于树高,立地指数不同时林分密度对树高和胸径生长分化的影响程度也不同。[结论]在立地指数达22及以上的立地条件下培育杉木大径材,可通过3次间伐进行密度控制,林分最终保留密度宜为650~1000株·hm^(−2)。

[Objective]The effects of site quality and stand density on the growth and timber assortment structure of Chinese fir plantations were investigated to provide theoretical basis for the cultivation of largediameter timber of Chinese fir.[Method]According to the upper,middle and lower slope positions and different slope directions,a total of 63 plots of Chinese fir plantations with the age range from 28 to 36 years were set up.Based on the data of growth and basic parameters measured forest growth,correlation analysis and regression analysis were performed in the study.[Result]When the stand density was similar,the higher the site index was,the higher the individual volume,stock volume and large-diameter timber yield rate of the same cultivation years were.Under the same site conditions,the stand mean height,DBH,tree volume and ratio of large diameter timber yield decreased with the increase of stand density,whereas the stand volume increased with the increase of density within a certain density range.Stand density had a greater effect on differentiation of DBH than that of tree height when the site index was the same.However,the effect of stand density on differentiation of tree height and DBH varied when the site index was different.[Conclusion]When cultivating large-diameter timber of Chinese fir under site conditions with a site index of 22 or above,the density can be controlled by three thinnings,and the final retention density of the stand should be 650-1000 trees per hectare.