胸高断面积

莽山乔木的最大胸径、胸高断面积之和与海拔呈明显的负相关性，而立木密度的变化规律不明显。

On Mt. Mang , maximum DBH and basal area showed significantly negative correlations with altitude while stem density did not change significantly with altitude .

随着海拔的上升，整个乔木层以及不同生活型的最大树高均呈显著下降趋势，而乔木树种的最大胸径、胸高断面积之和以及立木密度都呈现出先增大后减小的趋势；

Maximum height of tree layer and of different life forms decreased significantly with increasing altitude ; however , maximum DBH , basal area and stem density were highest at mid-altitudes .

电子角规是电子经纬仪与PDA的有机结合，电子经纬仪测角精确，配合相应的PDA应用程序，可以准确地实现角规的量测胸高断面积功能。

Electronic angle gauge is organic combination of electronic theodolite and personal digital assistant . It can accurately survey forest basal area by reason of precise angle-surveying of electronic theodolite and corresponding PDA program .

1～26a的平均相对生长率为0.243；速生期（3～11a）内胸高断面积平均生长量为0.001474m2。

The average growth intensity of basal area was 0.243 . During the rapid growth period ( 3 to 11 years ) the average increment of basal area per year was 0.001 474 m 2 .

混交林的胸高断面积与激光雷达变量则没有明显关系。

There was no obvious relationship between basal area of mixed forest and laser variables .

植被群落优势种为刺槐，其胸高断面积和重要值方面均表现出明显的优势度。

The statistics of breast-height basal area and the important value showed that Robinia pseudoacacia was obviously dominant species .

针叶林内，最高幼苗密度、多样性和丰富度均出现在中等胸高断面积的情况下。

However , seedling density , seedling diversity and seedling richness were peaked at the intermediate basal area in three conifer forests and decreased with the increase of basal area .

结果表明，群落均匀度指数、空隙度和开度、林分胸高断面积和林分密度在大尺度上表现出显著的空间结构。

The results showed that Pielou evenness index , gap-fraction , openness , stand basal area , and stand density were influenced by spatial structure of the community at a broad scale .

通过主成分分析，对太白红杉林特征起决定作用的因子依次是：胸径＞树高＞年龄＞胸高断面积＞物种丰富度；

The main factors which decided the characteristics of Larix Chinensis forests were analyzed , the order is DBH ﹥ tree height ﹥ age ﹥ Area at breast height ﹥ species abundance .

以林分平均胸高直径的100倍为直径作圆形样地，得出林分每公顷胸高断面积等于圆形样地圆内的林木株数加上圆界上林木株数的一半。

The one-hundred-time forest stand average breast diameter as the diameter to make circle-shaped sample results that section area of breast height per hectare equals to that the number of the forest timbers inside the circle plus an half of the number of the timbers on the circle boundary .