林分密度及混交度对长白山天然风景林树木形态的影响

Effects of Stand Density and Mingling Intensity on Tree Morphology in Natural Scenic Forest in Changbai Mountain

【目的】以期探明天然风景林不同林分密度、不同混交度条件下树木形态的变化规律,及林分密度、混交度及其交互作用对不同大小树木个体形态特征的影响机理。【方法】采用综合指数法建立4个树木形态指数,通过分析65块样地的林分空间结构信息与样地内1 891株林木个体各形态指数的关系,研究林分密度和混交度对长白山天然风景林树冠、树干形态及干冠协调程度的影响。【结果】林分密度对各树木形态指数均产生极显著影响(P<0.01),并与林木空间占有指数、干冠协调指数、树冠扩展指数呈负相关关系,与干形通直指数呈正相关关系,林木空间占有指数、干冠协调指数在各径级树木个体上受密度的影响均达到显著水平(P<0.000 5),树冠扩展指数、干形通直指数受林分密度的影响分别只在中径级(P<0.000 5)和小径级(P=0.017)树木个体中达到显著水平;混交度与林木空间占有指数、干冠协调指数、干形通直指数呈负相关关系,与树形扩展指数呈正相关关系,其中对干冠协调指数的影响达到显著水平(P<0.000 5),并且在小径级树木和大径级树木个体上作用分别达到极显著(P<0.000 5)和显著(P=0.038)水平;密度和混交度的交互作用对干冠协调指数产生极显著影响(P<0.000 5),林分密度对干冠协调指数的影响程度随混交度的增大而呈现先增后减的趋势,混交度对干冠协调指数的影响程度随林分密度的增大而呈现先减后增的趋势。【结论】林分密度和混交度通过改变风景林树木的邻体竞争关系,进而显著影响风景林树木个体的树冠、树干形态及其协调关系,其中林分密度是主导因素,在研究范围内高于1 200株·hm^(-2)的林分密度会抑制各径级树木体积的增大和干冠形态比例协调程度的提升,混交度在林分密度高于1 600株·hm^(-2)或小于800株·hm^(-2)时显著影响大径级和小径级树木个体干冠形态的协调性,低密度中度混交的林分最有利于树木个体干冠形态的协调发展。

【Objective】 This research aims at investigating the variation patterns of tree morphology with different stand densities and mingling intensities in natural scenic forest, and clarifying the effects of stand density, mingling intensity and their interaction on tree morphology of different diameter classes.【Method】65 plots were set up in typical areas of Changbai Mountain, the forest spatial structures and tree morphological indicators were investigated. By using synthetic index method, four morphology indices were established, and the effects of stand density, mingling intensity and their interaction on these indices were analyzed with variance analysis method. 【Result】 Stand density had very significant effects（P<0.01） on all tree morphology indices. The increase of stand density had adverse effects on tree spatial occupancy index（U1）, stem and crown coordination index（U2） and crown expansion index（U3）, while had a beneficial effect on stem straight index（U4）. The effects of stand density on U1 and U2 were very significant（P<0.000 5） in all three diameter classes, while the effect on U3 were very significant（P<0.000 5） only in middle diameter class, and the effect on U4 were significant（P=0.017） only in small diameter class. Mingling intensity was negatively correlated with U1, U2 and U4, while positively correlated with U3. The effect of mingling intensity on U2 were very significant（P<0.000 5）, and this effect showed extremely significant difference（P<0.000 5） and significant difference（P=0.038） in small diameter class and large diameter class, respectively. The interaction had a very significant influence（P<0.000 5） on U3, and the influence of stand density on U2 showed a trend of increasing first and then decreasing with the increase of mingling intensity, while the influence of mingling intensity on U2 was on the contrary.【Conclusion】 In scenic forest, stand density and mingling intensity significantly affected crown, stem and their coordination by changing the competition relationship of neighboring trees, and the stand density played a major role. Within the scope of the study, the stand density of more than 1 200 individual·hm-2 had a significant suppression on the increase of tree volume and tree morphology coordination of all three diameter classes, while mingling intensity showed a significant influence on the tree morphology coordination in large diameter and small diameter trees when the density was more than 1 600 individual·hm-2 or less than 800 individual·hm-2, and the forest with low density and moderate mingling intensity were most beneficial to the coordinated development of trunk and crown morphology.