大兴安岭呼中地区3种林分的群落特征、物种多样性差异及其耦合关系

准确理解天然林林分群落特征及其与物种多样性耦合关系是提升天然林管理、达到多样性保护的关键。选择大兴安岭呼中地区典型落叶松林、杂木林、白桦落叶松林为研究对象,分别对乔木层、灌木层和草本层特征(高度、胸径、冠幅、盖度等)进行调查并计算丰富度指数、多样性指数和均匀度指数,旨在探究林分间差异及其耦合关系变化。结果表明:(1)乔木层的树高、枝下高表现出杂木林落叶松林白桦落叶松(P0.05);落叶松林的胸径比白桦落叶松林和杂木林的高出6%和11%;灌木层的高度、盖度、地径、冠幅和草本层多度、盖度、高度在森林类型间均未表现出显著差异。(2)3个森林类型的乔、灌、草丰富度指数R、Shannon-Wiener指数及Simpson指数均表现出杂木林最大,乔木层和草本层呈相同规律,即杂木林白桦落叶松林落叶松林,而灌木层表现出杂木林落叶松林白桦落叶松林;白桦落叶松林和杂木林的乔木层均匀度Pielou指数和Alatalo指数约为落叶松林的3倍左右,而在灌木层和草本层在森林类型间差异不显著(P0.05)。(3)典范对应分析(CCA)结果表明林分群落特征和生物多样性关系存在明显森林类型间差异。总体表现为灌木特征(冠幅、地径)、草本层特征(盖度、多度和高度)对多样性均有较大影响;白桦落叶松林和杂木林的胸径对多样性影响明显,而落叶松林的乔木高度(树高、枝下高)对多样性影响较大。杂木林随着灌木盖度、草本高度的增加,草本物种多样性降低、乔木多和灌木物种多样性增加;而落叶松林相同的多样性变化多伴随草本高度增加、多度和盖度变小。灌木层物种多样性增加多与乔木和草本物种多样性降低相伴随,在杂木林中同时伴随着乔木胸径和草本的盖度、多度增大、灌木冠幅变小,而白桦落叶松林则伴随灌木冠幅和草本多度盖度的减小。以上结果表明,林分群落特征与物种多样性存在耦合关系,上述解耦合结果为通过维持良好森林结构、多样性保护具有实践意义。

Differences in community characteristics, species diversity, and their coupling associations among three forest types in the Huzhong area, Daxinganling mountains

Exploring the differences and coupling relationships of species diversity and stand characteristics could provide data with which to improve biodiversity and ecological services of natural forests. In this study, three typical communities of larch forest, shaw (mixed forest with various tree species), and birch-larch forest were selected at Huzhong in the Daxinganling mountains for measuring stand characteristics (height, diameter at breast heightDBH], crown width, coverage, and others), richness index, diversity indexes, and evenness indexes of the arbor layer, shrub layer, and herb layer. Canonical correspondence analysis (CCA) was used to uncover their differing associations among forest types, together with a multiple analysis of variance to detect the inter-forest differences. The results showed that (1) the height and clear tree bole height of the arbor layer differed with shaw > larch forest > birch-larch forest (P < 0.05); DBH of the larch forest was 6% and 11% higher than that in the birch-larch forest and the shaw, respectively. There were no significant differences in the shrub layer in the parameters of height, canopy coverage, ground diameter, crown width, as well as in the herb layer for species abundance, herb coverage, and herb height. (2) The maximum species richness, Shannon-Wiener index, and Simpson index of the arbor layer, shrub layer, and herb layer all occurred in the shaw relative to the larch forest and the birch-larch forest. Moreover, the herb layer showed the same pattern as in the arbor layer, i.e., shaw > birch-larch forest > larch forest; however, the shrub layer exhibited a different order, with shaw > larch forest > birch-larch forest. The species evenness of the arbor layer in the birch-larch forest and shaw were approximately three times that of the larch forest; however, there was no significant difference in the shrub layer and the herb layer (P > 0.05). (3) CCA showed that the correspondence associations between community characteristics and species diversity differed among the three forest types. In general, for all three forests the characteristics of the shrub (ground diameter and crown width) and herb layer (coverage, abundance, and height) had a substantial influence on plant species diversity. Plant diversity was significantly affected by tree DBH in the birch-larch forest and the shaw; however, it was highly significantly affected by tree height in the larch forest. With the increase of shrub coverage and herb height, herb diversity decreased; whereas decreasing herb diversity usually corresponded with increasing diversity of the arbor and shrub layer in the shaw. In the larch forest, herb height increase, together with decreases in abundance and coverage usually corresponded with a decrease in herb diversity, and increases in arbor and shrub diversity. An increase in shrub diversity was usually accompanied by a decrease in arbor and herb diversity, but corresponded with increases in tree DBH, herb abundance, and coverage, and decreases in shrub crown width in the shaw; however, it was accompanied by decreases in shrub crown width, as well as herb abundance and coverage in the birch-larch forest. Our findings highlighted that community characteristics were closely coupled with species diversity, and the above-mentioned decoupling results will favor diversity conservation through maintaining good forest structure in the Daxinganling Mountain Region, Northeast China.