大兴安岭呼中地区白卡鲁山植物群落结构及其多样性研究

Structure and species diversity of boreal forests in Mt. Baikalu, Huzhong area, Daxing'an Mountains, Northeast China

通过沿海拔梯度系统调查 ,运用TWINSPAN分类方法 ,划分出大兴安岭地区白卡鲁山的主要植物群落类型并分析了其结构特征。利用物种丰富度和α多样性等指标 ,研究了乔木层、灌木层和草本层植物的多样性特征及其随海拔的变化趋势。结果显示 :(1)白卡鲁山乔木层在海拔 70 0 - 12 90m范围内 ,可分为 4种主要群落类型 :兴安落叶松疏林、兴安落叶松 白桦混交林、兴安落叶松 白桦 樟子松混交林、兴安落叶松纯林群落 ;(2 )同一植物群落的结构特征比较相似 ,除兴安落叶松疏林外 ,其他三种森林类型的平均胸径和平均树高随海拔升高有逐渐增大的趋势 ;(3)乔木层的直径和树高分布清晰地反映了群落的水平和垂直结构。直径分布均呈现倒“J”型 ,表明森林的自我更新状况良好 ;而树高分布主要以双峰分布和近似对称分布为主 ;(4 )乔木层的物种丰富度和α多样性在兴安落叶松纯林中最小 ,在兴安落叶松 白桦混交林和兴安落叶松 白桦 樟子松混交林群落次之 ,而在兴安落叶松疏林群落相对较高。各群落类型的灌木层和草本层植物多样性没有明显的差异。乔木层、灌木层和草本层的物种多样性随海拔梯度均没有表现出明显的变化趋势。

Data on the structure and diversity of boreal forest were investigated along 700-1440 m in Mt. Baikalu in Huzhong area, Daxing'an Mountains, Northeast China. A total of 7 species in tree layer, 12 in shrub layer and 115 in herb layer were recorded in 17 plots. Plant communities were clustered using TWINSPAN classification, and the structure characteristics of different communities, plant species richness and α diversity indicated by Shannon-Wiener index in tree layer, shrub layer and herb layer were analyzed. The results were summarized as follows: Four groups of community types characterized by different dominants in tree layer were distinguished: (1) Larix gmelini woodland; (2) mixed Larix gmelini-Betula platyphylla forest; (3) mixed Larix gmelini-Betula platyphylla-Pinus sylvestris var. mongolica forest; (4) pure Larix gmelini forest. These forest types showed no remarkable trend along altitudinal gradient, except that the distribution of Larix gmelini woodland was limited to high altitude. Structural characteristics such as mean tree height, mean tree diameter at breast height (DBH), total basal area, stand density and importance value of Larix gmelini were similar in the same community type. Mean tree height and DBH in the forest types increased with increasing altitude, when those in the Larix gmelini woodland were excluded. The frequency distribution of DBH and height explicitly indicated the horizontal and vertical structure of four forest types. DBH frequency distribution for all four forest types showed a typical reversed J shape, suggesting the forests in Mt. Baikalu were regenerating in a good stage, while majority of height frequency distributions presented a bimodal and approximately symmetric distribution. Species richness and α diversity in tree layer gradually increased from pure Larix gmelini forest to mixed Larix gmelini-Betula platyphylla-Pinus sylvestris var. mongolica and Larix gmelini-Betula platyphylla forest, to Larix gmelini woodland, but no significant trend of diversity occurred in shrub layer and herb layer for different communities. Whether in tree layer, shrub layer or herb layer, species richness and α diversity showed no remarkable trend along altitude, which may be related to the low altitude of this mountain.