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濒危植物树枫杜鹃(Rhododendron changii)种群结构及伴生群落特征

杨阳1,马立辉2,王海洋1*   

  1. (1西南大学园艺园林学院, 重庆 400700;2重庆市林业科学研究院, 重庆 400000)
  • 出版日期:2019-05-10 发布日期:2019-05-10

Population structure and companion community characteristics of the endangered species, Rhododendron changii.

YANG Yang1, MA Li-hui2, WANG Hai-yang1*   

  1. (1College of Horticulture and Landscape Architecture, Southwestern University, Chongqing 400700, China; 2Chongqing Academy of Forestry Sciences, Chongqing 400000, China).
  • Online:2019-05-10 Published:2019-05-10

摘要: 分析了濒危植物树枫杜鹃种群结构及伴生群落物种组成、乔灌层物种多样性、垂直成层及个体径级结构等特征,并通过冗余分析(RDA)、典范对应分析(CCA)方法检验了树枫杜鹃种群及群落乔灌层物种组成与环境因子间的关系。结果表明:(1)树枫杜鹃种群径级结构呈单峰型,更新不连续,缺乏幼苗,幼株时期为又一死亡高峰期,种群呈衰退趋势;(2)4个伴生群落中共有木本植物56种,隶属于23科40属,优势科为壳斗科、蔷薇科、槭树科、杜鹃花科,林下多箭竹(Fargesia spathacea);伴生群落的乔灌层多样性指数均较低,草本层不发达;群落1与群落2为高度1~1.5 m的灌丛,群落3为高度3~4 m的常绿阔叶苔藓矮林,群落4为高度8~10 m的常绿落叶阔叶混交林;树枫杜鹃均位于群落下层,相比于乔木林群落,其在灌丛群落中生长较占优势;群落中耐阴种的小径级个体比例大,均呈增长趋势,林下竞争将持续增强;(3)前向选择及蒙特卡罗(Monte Carlo)检验表明,坡位对乔木层物种组成影响极显著,郁闭度与坡向对灌木层物种组成影响极显著(P<0.01);而枯落物厚度与空气相对湿度是影响树枫杜鹃幼苗的主要环境因子,林冠郁闭度、坡向则是影响幼株与成株的主要环境因子;同时,幼株与成株也分别受到林下物种密度与林下竹类覆盖度的影响(P<0.01)。因此,疏伐上层林木,人为干预林下幼树及箭竹的生长,并清理地表枯落物,对缓解树枫杜鹃濒危的现状及维持其种群的发展具有重要意义。

关键词: 森林, 碳储量, 碳密度, 山东省

Abstract: Rhododendron changii is a threatened plant species. Here, we investigated its population structure, species composition of companion communities, vertical stratification and plant diameter class, and species diversity in tree and shrub layers. Furthermore, the relationships between R. changii population and species composition of tree and shrub layers in community and environmental factors were examined using redundancy analysis (RDA) and canonical correspondence analysis (CCA). The results showed that: (1) The diameter class pattern of R. changii was unimodal, indicating that the population renewability was limited in a discrete way and lack of seedlings. In addition, the sapling period was another peak of death, implying the population was continuing to decline. (2) There were four companion communities around the population, containing a total of 56 woody species belonging to 23 families and 40 genera. The dominant families were Fagaceae, Rosaceae, Aceraceae, and Ericaceae, with a large number of Fargesia spathacea in the understory. The diversity index of tree and shrub layers was relatively low with an underdeveloped herbaceous layer. The companion communities 1 and 2 belonged to shrubs with an average height of 1-1.5 m, the community 3 was an evergreen broadleaf-mossy dwarf forest with an average height of 3-4 m, and the community 4 was an evergreen deciduous mixed forest with an average height of 8-10 m. R. changii grew in the lower layer in all companion communities, while dominated in shrub communities compared to arbor one. There was a large proportion of small-diametric individuals of shade-tolerant species in the community, indicating increasing competition in the understory. (3) The results of the forward selection and Monte Carlo analysis showed that slope position exerted a significant impact on species composition of tree layer, while the canopy closeness and slope exposure controlled that of the shrub layer (P<0.01). Litter thickness and air humidity were two primary environmental factors affecting R. changii seedlings, while canopy coverage and slope exposure influenced the saplings and adults of R. changii. Besides, saplings and adult plants were also affected by the species density and bamboo coverage (P<0.01). In conclusion, it is important to decrease canopy cover, interfere with the growth of the other saplings and F. spathacea in forests and clean up litter layer, to relieve the endangered situation and maintain population development of R. changii.

Key words: forest, carbon storage, carbon density, Shandong Province.