放牧干扰梯度下川西亚高山植物群落的组合机理

doi:10.3773/j.issn.1005-264x.2010.11.006

摘要/Abstract

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。

关键词: 组合机理, 功能群组成, 放牧梯度, 谱系结构, 植物群落

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.

Key words: assembly rules, functional group composition, grazing gradient, phylogenetic structure, plant community

闫帮国, 文维全, 张健, 杨万勤, 刘洋, 黄旭, 李泽波. 放牧干扰梯度下川西亚高山植物群落的组合机理. 植物生态学报, 2010, 34(11): 1294-1302. DOI: 10.3773/j.issn.1005-264x.2010.11.006

YAN Bang-Guo, WEN Wei-Quan, ZHANG Jian, YANG Wan-Qin, LIU Yang, HUANG Xu, LI Ze-Bo. Plant community assembly rules across a subalpine grazing gradient in western Sichuan, China. Chinese Journal of Plant Ecology, 2010, 34(11): 1294-1302. DOI: 10.3773/j.issn.1005-264x.2010.11.006

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链接本文: https://www.plant-ecology.com/CN/10.3773/j.issn.1005-264x.2010.11.006

https://www.plant-ecology.com/CN/Y2010/V34/I11/1294

图/表 6

表1 研究样地概况

Table 1 Outline of research sites

样地编号 Site No.	植被类型 Vegetation type	坡度 Gradient (°)	坡向 Slope aspect	郁闭度 Canopy density (%)	优势木本植物 Dominance woody species
1	草甸 Meadow	28	西偏北21° West by North 21°	8	窄叶鲜卑花 Sibiraea angustata 金露梅 Potentilla fruticosa
2	矮灌丛 Short shrub	26	西偏北30° West by North 30°	50	杯腺柳 Salix cupularis 鹧鸪杜鹃 Rhododendron zheguense
3	灌丛 Shrub	30	西偏北35° West by North 35°	60	华西花楸 Sorbus wilsoniana 细枝绣线菊 Spiraea myrtilloides
4	高大灌丛 Tall shrub	30	西偏北42° West by North 42°	75	华西花楸 Sorbus wilsoniana 越桔叶忍冬 Lonicera myrtillus 柳叶忍冬 L. lanceolata
5	阔叶林 Deciduous forest	28	西偏北30° West by North 30°	70	红桦 Betula albo-sinensis 糙皮桦 B. utilis
6	针叶林 Coniferous forest	32	西偏北28° West by North 28°	85	岷江冷杉 Abies faxoniana 大理杜鹃 R. taliense

图1 放牧干扰梯度上植物功能群均匀度的变化趋势。A, 各样地功能群均匀度Jp。B, 各样地小样方(50 cm × 50 cm)功能群均匀度Jsub。

Fig. 1 Functional group evenness changing along a grazing gradient. A, Functional group evenness index of plots Jp. B, Functional group evenness indexes of subplots (50 cm × 50 cm) Jsub.

表2 各样方随机群落中净关联指数(NRI)、邻近类群指数(NTI)和功能群均匀度(Jp)小于实际群落相关值的次数(总模拟次数999)

Table 2 The times of cases in which net relatedness index (NRI), nearest taxon index (NTI) and functional group evenness (Jp ) in random communities are lower than the observational communities (999 simulated replications).

样地 Site		1			2			3			4			5			6
样方 Plot	1L	1M	1H	2L	2M	2H	3L	3M	3H	4L	4M	4H	5L	5M	5H	6L	6M	6H
物种丰富度 Species richness	80	75	76	78	79	72	68	68	63	52	51	48	50	54	51	45	40	40
Rc	945	957	913	991	990	989	905	683	818	390	297	455	516	228	418	324	240	248
Tc	983	993	958	998	985	992	961	755	913	487	311	421	527	289	436	471	392	393
Jc	55	27	4	71	38	33	25	19	888	763	778	812	959	950	994	877	995	990

图2 功能群均匀度与物种丰富度之间的关系。

Fig. 2 Relationship between functional group evenness and species richness.

图3 邻近类群指数(NTI)沿放牧梯度的变化。

Fig. 3 Variation of nearest taxon index (NTI) across the grazing gradient.

图4 各主要功能群物种多样性在放牧梯度上的变化趋势(平均值±标准误差)。 BF, 基生叶阔叶杂草; BG, 丛生禾草; DW, 落叶木本; EF, 茎叶型阔叶杂草; EW, 常绿木本; FE, 蕨类; RG, 根茎禾草; SF, 半基生叶阔叶杂草。

Fig. 4 The trends of species richness of each functional group on sites across the grazing gradient (mean ± SE). BF, basal forbs; BG, bunch grasses; DW, deciduous woody plants; EF, erect leafy forbs; EW, evergreen woody plants; FE, ferns; RG, rhizome grasses; SF, semi-basal forbs.

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