不同林分密度胡桃楸胸径、树高、材积与冠幅关系

Relationship Between Crown Width and DBH, Tree Height or Volume of Juglans mandshurica in Stands of Different Density

为了解胡桃楸在不同密度次生林中胸径、树高及单株材积对冠幅的影响程度,利用通径分析及相关分析的方法,对黑龙江省张广才岭林区3种密度等级(Ⅰ:≤500株/hm^(2),Ⅱ:>500~600株/hm^(2),Ⅲ:≥600株/hm^(2))下次生林中优势树种胡桃楸的胸径、树高、单株材积与冠幅之间的关系进行分析。结果表明:(1)随着林分密度的增大,冠幅的生长速度逐渐降低,在Ⅰ级密度的林分中胡桃楸冠幅涨幅最大,高于密度Ⅱ的40.27%。从分级效果来看,随着林分密度的增加,胡桃楸冠幅的分布更加集中,Ⅲ级密度下其冠幅主要分布在3.0~7.5 m,比例为80.60%。(2)各级密度下的林分中胡桃楸胸径、树高与冠幅的相关性均达到极显著正向水平(P<0.01),但随林分密度的增加,胡桃楸树高和单株材积对冠幅的正向作用出现先减弱后增强的现象,胸径对冠幅的影响先增大后减小,且对冠幅的变化产生的直接作用均大于间接作用。(3)由决策系数可知,在不同林分密度等级下,对胡桃楸冠幅的生长起决定性的因子不同,其中I级下,树高是其决策因子,Ⅱ和Ⅲ级下则为胸径。研究表明,在密度小于500株/hm^(2)的胡桃楸次生林中,胡桃楸树高为冠幅的主要影响因子(R^(2)=0.229),在高于该密度的林分中,以胸径预测其冠幅的生长效果最好(R^(2)=0.515和0.397),这为胡桃楸冠幅模型的建立奠定基础。

In order to understand the influence of Juglans mandshurica DBH,tree height and individual plant volume on crown width in secondary forests with different densities,path analysis and correlation analysis were used to study the relationship between DBH,tree height,volume of individual tree and crown width of the dominant species in the secondary forest of Juglans mandshurica under 3 density grades(Ⅰ:≤500 tree/hm^(2),Ⅱ:>500~600 tree/hm^(2),Ⅲ:≥600 tree/hm^(2))of Zhangguangcai forest district,Heilongjiang Province.The results showed that:(1)with the increase in stand density,the increase in crown width gradually slowed down.Among the stands of density grade Ⅰ,the crown width of Juglans mandshurica increased the fastest,which was higher than 40.27%of density Ⅱ.From the classification results,with the increase of stand density,the distribution of crown width of Juglans mandshurica was more concentrated.The crown width of stands with grade Ⅲ density was mainly distributed in the range of 3-7.5 m,accounting for 80.60%.(2)The correlation between DBH,tree height and crown width of Juglans mandshurica in different density stands reached extremely significant positive level(P<0.01).However,with the increase of stand density,the positive effects of height and individual volume of Juglans mandshurica on crown width first weakened and then increased,the influence of DBH on crown width first increased and then weakened,and the direct effect of DBH,height and individual volume which on crown width was greater than indirect effect.(3)According to the decision coefficient,under different stand density grades,the decisive factors for the growth of Juglans mandshurica crown width were different.Among them,the tree height was the decision factor under the density Ⅰ,and the DBH under the density Ⅱ and Ⅲ.The results showed that in the secondary forest of Juglans mandshurica with densities less than 500 trees/hm^(2),the tree height was the main influencing factor for crown width(R^(2)=0.229).In stands higher than this density,the DBH was the best to predict the growth of the crown width(R^(2)=0.515 and 0.397).This research lays the foundation for the establishment of crown width model of Juglans mandshurica.