植物生态学报 ›› 2010, Vol. 34 ›› Issue (11): 1294-1302.doi: 10.3773/j.issn.1005-264x.2010.11.006

• 研究论文 • 上一篇    下一篇

放牧干扰梯度下川西亚高山植物群落的组合机理

闫帮国1, 文维全2, 张健1*, 杨万勤1, 刘洋1, 黄旭1, 李泽波1   

  1. 1四川农业大学林学院, 四川省长江上游林业生态工程重点实验室, 四川雅安, 625014;
    2川西林业局, 四川阿坝, 623102
  • 收稿日期:2009-11-16 修回日期:2010-09-20 出版日期:2010-11-01 发布日期:2010-10-31
  • 通讯作者: 闫帮国 E-mail:ecoyanbangguo@yahoo.com
  • 基金资助:

    国家“十一五”科技支撑计划项目(2006BAC01A11);国家自然科学基金(30771702 ;30471378);教育部新世纪优秀人才支持计划项目(NCET - 07 - 0592);四川农业大学“长江上游植被恢复与重建”创新团队计划项目

Plant community assembly rules across a subalpine grazing gradient in western Sichuan, China

YAN Bang-Guo1, WEN Wei-Quan2, ZHANG Jian1*, YANG Wan-Qin1, LIU Yang1, HUANG Xu1, LI Ze-Bo1   

  1. 1College of Forestry, Sichuan Agricultural University, the Upper Yangtze’ Key Laboratory of Forestry Ecological Engineering of Sichuan Province

    2Forestry Bureau of Western Sichuan
  • Received:2009-11-16 Revised:2010-09-20 Online:2010-11-01 Published:2010-10-31
  • Contact: YAN Bang-Guo E-mail:ecoyanbangguo@yahoo.com

摘要:

为了阐明放牧干扰对川西亚高山区域植物群落的组合过程以及群落结构的影响, 研究了放牧干扰梯度下的功能群均匀度和群落谱系结构的变化趋势。结果显示: 在干扰较轻的阔叶林与针叶林样地, 部分样方的功能群均匀度显著高于无效模型, 随着干扰梯度的增强, 功能群均匀度呈线性下降, 样方平均值从0.930降至0.840, 其高于无效模型的次数也逐渐降低,干扰程度较大的草甸中出现部分样方的功能群均匀度显著低于无效模型。随着干扰程度的增强, 群落的谱系结构指数也呈逐渐上升趋势, 净关联指数平均值由–0.634逐渐增加至2.360, 邻近类群指数由–0.158上升至2.179。草甸与低矮灌丛受干扰较为严重, 其大部分样方的谱系结构指数显著高于随机群落, 表明干扰群落的谱系结构呈聚集分布。功能群均匀度与谱系结构的变化趋势一致, 表明生境筛滤效应与种间竞争作用的平衡决定着群落的组合过程。干扰降低了竞争作用, 促进了少数耐干扰功能群的优势地位, 造成功能群均匀度下降, 同时通过生境筛滤作用, 使群落的谱系结构呈现出聚集分布; 而未干扰的群落中由于竞争作用的效应, 功能群均匀度较高, 谱系结构也更加分散。研究区域植物群落的功能群均匀度与物种丰富度呈负相关, 表明物种间特别是相似物种间的竞争限制了群落的物种多样性。研究结果说明, 生态位分化和物种间的相互竞争在物种共存与群落组合中具有重要作用。

Abstract:
Aims Community assembly rules are poorly understood, especially in subalpine areas. Plant communities are thought to be organized from a regional species pool through environmental filtering and competition. Environmental filtering will result in the formation of groups of species with similar traits, while competition will limit similarity of coexisting species. Environmental filtering and competition can also affect community phylogenetic structure when species niches are phylogenetically conservative. Our object was to uncover how these processes affected community assembly and their responses to grazing. Methods We sampled plant communities in six sites across a grazing gradient and calculated functional group evenness to test effects of environmental filtering and competition. For investigating community phylogenetic structure, we calculated nearest taxon index and net relatedness index using phylocom software. We examined community phylogenetic structures and functional group evenness under a grazing gradient using null model and phylogenetic indexes. Important findings We found strong nonrandom patterns in species richness distributions among functional groups in non-grazed plots, and functional group evenness significantly decreased with increased grazing pressure. There was a significant phylogenetic cluster in intensively grazing communities and this gradually became dispersion toward primary forest. As a filtering effect, grazing increased species richness of a few lineages and decreased others. This process resulted in community phylogenetic cluster or reductions in functional group evenness. Functional group evenness increasing and phylogenetic over-dispersion might stem from competition, which could limit similarity of coexisting species. Results indicated that both habitat filter and competition simultaneously shaped community structure. Findings suggest that grazing affected functional group evenness and phylogenetic structure through changing the balance between environmental filtering and competition in communities. The negative relationship between functional group evenness and species richness suggests that competition might suppress plant diversity in local communities. Results support that species functional divergence and their competition have important roles in community assembly.