Abstract:

The pure forest (PF) of Pinus massoniana and three different coniferous and broad-leaved mixed forests such as Pinus massoniana-Quercus acutissima mixed forest (PQM), Pinus massoniana and Liquidambar formosana mixed forest (PLM) and Pinus massoniana-Platycarya strobilacea mixed forest (PPM) were selected from the Dabie Mountains of northern subtropical region as the research objects. We analyzed the changes of understory plant diversity of the different forest types under different slope aspects such as Southeast and Northwest slopes. This study can provide the theoretical evidences for the production, management as well as the biodiversity conservation of P. massoniana forest ecosystem under different environmental gradients of this region. The results showed that: (1) There were 49 species, 49 genera, and 35 families in total under the four P. massoniana forest types. Among them, 31 species, 31 genera, and 23 families were included in the forests of southeast slope and 36 species, 36 genera, and 26 families were in the northwest slope. The number of species in the shrub layer on the northwest slope was higher than that on the southeast slope. While the number of species in herb layer was higher on the southeast slope than the northwest slope. (2) There were significant differences in the number of understory species among the four P. massoniana forest types. Among them, the PLM had the most abundant understory species (26 species, 26 genera, and 23 families), while the PF had the least (17 species, 17 genera, and 16 families). The number of species in PQM and PLM were significantly higher than that in the PPM and PF. (3) There were significant differences in species composition and dominant species in shrub layer and herb layer of four P. massoniana types on different slopes. Carex Ligata and Lophatherum gracile were the most important and frequently occurring species in the understory herb layer of four forest types on the southeastern slope. Eupatorium japonicum, Dryopteris fuscipes and Carex ligata were the most important and frequently occurring species in the understory herb layer of four forest types on the northwest slope. Carex sinensis was the common dominant species in the herb layer on both slopes. In the shrub layer, plant species with high frequency and high importance values varied widely among the four forest types on different slopes. (4) Slope aspect had significant effect on Shannon diversity index, Margalef richness index and Simpson index of dominance in understory shrub and herb layers of four P. massoniana forest types, but had no significant effects on Pielou evenness index. Moreover, among the four P. massoniana forest stands, PQM had the highest Shannon diversity index, Margalef richness index and Simpson dominance index in understory shrub layer on different slopes. In conclusion, compared with the PF, the three kinds of mixed forest types had richer understory plant species and higher diversity, especially the PQM.

Key words: north subtropical region, slope aspect, Pinus massoniana, pure forest, coniferous and broad-leaved mixed forest, plant diversity

摘要：

以北亚热带大别山地区马尾松（Pinus massoniana）纯林（PF）及3种不同马尾松针阔混交林型（马尾松-麻栎(Quercus acutissima) 混交林 (PQM)、马尾松-枫香 (Liquidambar formosana) 混交林 (PLM) 和马尾松-化香 (Platycarya strobilacea) 混交林 (PPM)）为研究对象,分析不同坡向（东南坡 (SE) 和西北坡 (NW)）下马尾松4种林型林下植物多样性的变化规律,旨在为该区不同环境梯度下马尾松林生态系统的生产经营与生物多样性保护提供理论参考。结果表明,（1）马尾松4种林型林下出现植物种类共35科49属49种,其中东南坡为23科31属31种,西北坡为26科36属36种;灌木层的物种数表现为：西北坡>东南坡,而草本层的物种数表现为：东南坡>西北坡。（2）马尾松4种林型林下物种数目存在显著差异（P<0.05）,其中马尾松-枫香混交林（PLM）林下物种最丰富（23科26属26种）,而马尾松纯林（PF）林下物种数最少（16科17属17种）;马尾松-麻栎混交林（PQM）和马尾松-枫香混交林林下物种数显著高于马尾松-化香混交林（PPM）和纯林。（3）不同坡向下马尾松4种林型林下灌木层和草本层物种组成和优势种均存在显著差异。东南坡马尾松4种林型林下草本层中,重要值排名靠前且出现频率较高的物种为香港薹草（Carex ligata）和淡竹叶（Lophatherum gracile）,西北坡优势种重要值排名靠前且出现频率较高的物种为泽兰（Eupatorium japonicum）、黑足鳞毛蕨（Dryopteris fuscipes）和香港薹草,两个坡向的草本层共同优势种为香港薹草。在灌木层中,4种林型不同坡向林下植物种类重要值排名靠前且出现频率较高的物种差异较大。（4）坡向对马尾松4种林型林下灌木层和草本层Shannon-Wiener多样性指数、Margalef丰富度指数和Simpson优势度指数影响显著,而对Pielou均匀度指数无显著影响。4种林型中,马尾松-麻栎混交林（PQM）在不同坡向林下灌木层Shannon-Wiener多样性指数、Margalef丰富度指数和Simpson优势度指数均高于其他3种林型。相较马尾松纯林而言,3种马尾松针阔混交林林下植物种类更丰富,多样性程度高,尤其以马尾松-麻栎混交林为最优。

关键词: 北亚热带区, 坡向, 马尾松, 纯林, 针阔混交林, 植物多样性