漓江河岸带植物功能性状变异与关联

doi:10.17521/cjpe.2018.0119

摘要/Abstract

摘要：

研究植物功能性状随环境梯度的变异和关联格局, 对于认识不同环境梯度下群落构建和植物适应型具有重要意义。该研究以漓江河岸带不同河段植物群落为研究对象, 调查了研究区内36个样方的物种组成, 测量了样方内42种木本植物的叶面积(LA)、比叶面积(SLA)和木材密度(WD)的功能性状值, 并运用性状梯度分析法对3个功能性状进行群落内(α组分)和群落间(β组分)组分分解及相关性分析。结果表明: (1)群落平均LA表现为中游最小且和下游差异显著, 群落平均WD则表现为中上游显著高于下游, 群落平均SLA在两两河段间均差异显著。(2)不同河段的3个植物功能性状β组分差异显著且实际观测值均小于随机模拟的零模型分布, 但α组分在河岸带不同河段均差异不显著且3个功能性状的α组分分布范围均小于β组分, 说明在河岸带不同河段的群落构建过程中环境筛选的作用要大于群落内种间的相互作用。(3)性状SLA与LA在群落间和群落内呈现出实际观测和随机模拟的相关性均较低, 暗示了LA和SLA各自代表了植物在不同生态策略上的维度; 但SLA和WD实际观测值和随机模拟值呈现出较强的负相关关系, 暗示这2个性状对于环境筛选表现出较高的整体趋同适应性, 体现了植物功能性状对群落间环境变异的依赖性大于群落内种间相互作用的依赖性。

关键词: 漓江, 河岸带, 功能性状, 尺度变异, 性状梯度分析, 冗余分析, 相关性, 零模型

Abstract:

Aims Patterns of variation in plant functional traits and the correlation among them are important for understanding species coexistence and the maintenance of biodiversity. Our objectives in this study were to understand how variation and correlation of plant functional traits, at both the species and community levels, influence 1) plants adaptation to changing environments, and 2) the mechanisms of community assembly.
Methods We investigated species composition of riparian plant communities in 36 plots along the longitudinal gradient (represented by upstream, midstream, downstream) of the Lijiang River, Guilin, Southwest China. We measured three functional traits for 42 woody plant species: leaf area (LA), specific leaf area (SLA), and wood density (WD). For each plant community, we calculated 1) species abundance-weighted mean community trait values, and 2) species-level mean trait values. For each of these calculations, we used trait-gradient analysis to partition the three traits into alpha and beta components. We then conducted Pearson correlations to analyze the relationships among the three traits along the longitudinal gradient. Finally we tested the strength of environmental filtering using a null model that generates randomly assembled communities with species richness given by observed values.
Important findings The species abundance-weighted mean community value of LA was lowest in the midstream communities, which was significantly different from that in the downstream communities. The mean community value of WD for midstream and upstream communities was significantly higher than that for downstream communities. Mean community value of SLA was significantly different among the three reaches. The beta components of the three functional traits significantly differed among the three reaches and had observed values that are, on average, lower than simulated values. However, alpha components for all three traits were not significantly different among the three reaches and had consistently lower variation than beta components. This implies that the variation in the mean community trait value across plots was greater than trait variation between species within plots. The observed and simulated values of the alpha components for both LA and SLA were weakly correlated with each other within and among communities, which suggests that there are independent axes of differentiation among coexisting species. On the other hand, comparisons between observed and simulated values indicated that significantly negative correlations between SLA and WD were largely the result of strong environmental filters. Finally, these results imply that variation of plant functional traits is greater among communities than within communities.

Key words: Lijiang River, riparian zone, functional traits, scale variation, trait-gradient analysis, RDA ordination, correlation, null model

梁士楚, 刘润红, 荣春艳, 常斌, 姜勇. 漓江河岸带植物功能性状变异与关联. 植物生态学报, 2019, 43(1): 16-26. DOI: 10.17521/cjpe.2018.0119

LIANG Shi-Chu, LIU Run-Hong, RONG Chun-Yan, CHANG Bin, JIANG Yong. Variation and correlation of plant functional traits in the riparian zone of the Lijiang River, Guilin, Southwest China. Chinese Journal of Plant Ecology, 2019, 43(1): 16-26. DOI: 10.17521/cjpe.2018.0119

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2018.0119

https://www.plant-ecology.com/CN/Y2019/V43/I1/16

图/表 8

表1 漓江河岸带不同河段植物群落样方基本概况

Table 1 Basic information of the sampled plots in the riparian zone along the longitudinal gradient of the Lijiang River

河段 Reach	样方数 Plot number	海拔 Elevation (m)	温度 Temperature (℃)	降水量 Precipitation (mm)	干扰强度 Disturbance intensity	群落类型 Community type
上游 Upstream	3	154	24.7	1 941	轻度 Light	枫杨-石榕树群落 Pterocarya stenoptera-Ficus abelii communities
	3	148	23.0	1 941	轻度 Light	枫杨+朴树-萝芙木群落 Pterocarya stenoptera + Celtis sinensis-?Rauvolfia verticillata communities
	6	144	23.7	1 941	轻度 Light	枫杨+阴香-石榕树群落 Pterocarya stenoptera + Cinnamomum burmannii-Ficus abelii communities
中游 Midstream	4	138	26.0	1 900	重度 High	枫杨+乌桕-细叶水团花群落 Pterocarya stenoptera + Sapium sebiferum-Adina rubella communities
	5	134	25.0	1 900	重度 High	阴香群落 Cinnamomum burmannii communities
	3	104	24.0	1 900	重度 High	枫杨-萝芙木群落Pterocarya stenoptera-?Rauvolfia verticillata communities
下游 Downstream	8	111	30.1	1 900	中度 Middle	乌桕+朴树-牡荆群落Sapium sebiferum + Celtis sinensis-Vitex negundo var. cannabifolia communities
下游 Downstream	4	105	26.8	1 900	中度 Middle	乌桕-木槿群落 Sapium sebiferum + Hibiscus syriacus communities

图1 漓江河岸带植物阴香和牡荆物种平均比叶面积(lgSLAs)和群落平均比叶面积(lgSLAp)散点图。灰色圆点代表群落中的各个物种, 绿色实心圆点和橙色三角形分别表示阴香和牡荆, 在某pj处被矩形框起来的一列点表示群落j内所有共生物种。每个物种空心的图形点对应的横坐标代表该物种在样地中所处的平均位置(即该物种性状的β组分βi), 纵坐标是物种的平均性状值ti, 二者的差值即空心的图形点到y = x的距离(因为αi = ti - βi)就是物种功能性状的α组分αi, 代表群落中物种i平均比叶面积与共存物种平均比叶面积的差值, bi为物种i平均比叶面积(ti)对群落平均SLA (pj)的回归直线的斜率, 反映物种平均SLA沿群落平均性状梯度在种内的变化大小。

Fig. 1 The scatterplot between species mean specific leaf area (i.e. lgSLAs, cm2·g-1) vs. plot mean specific leaf area (i.e. lgSLAp, cm2·g-1) between Cinnamomum burmannii and Vitex negundo in the riparian zone of the Lijiang River. Each grey point represents a species in a specific plot; the green solid points and the orange solid triangles represent Cinnamomum burmannii and Vitex negundo respectively, and a column of grey points in a black rectangle represent all the species within community. For each species, the abscissa values of the large open point show the mean position of occupied plots (i.e., the beta component of the species trait value, βi), while the ordinate values of the solid symbols are their mean species trait value (ti). The difference between βi and ti, or the distance from the y = x line is αi (because αi = ti - βi ). Regression line shows abundance-weighted least squares regression of species trait values relative to plot mean trait values, with slope bi. bi is the slope of each species’ s regression line of species mean trait values (ti) relative to plot mean trait values (pj), it reflects the intraspecific variation of the species mean specific leaf area along a gradient defined by community-level mean trait values.

图2 漓江河岸带植物群落水平功能性状与环境因子的冗余分析(RDA)排序图。AN, 有效氮含量; DI, 干扰强度; Dis, 距离河岸距离; Ele, 海拔; LA, 叶面积; pH, 土壤pH值; Pre, 降水量; Rea, 河段; SLA, 比叶面积; SOM, 有机质含量; Tem, 温度; TN, 全氮含量; WD, 木材密度。plot 1-12, 上游; plot 12-24, 中游; plot 25-36, 下游。

Fig. 2 Redundancy analysis (RDA) ordination diagram showing the relationships between the three abundance weighted functional traits and 10 selected environmental factors of the riparian plant of the Lijiang River. AN, soil available nitrogen; DI, disturbance intensity; Dis, distance; Ele, elevation; LA, leaf area; pH, soil pH value; Pre, precipitation; Rea, reach; SLA, specific leaf area; SOM, soil organic matter content; Tem, temperature; TN, soil total nitrogen content; WD, wood density. plot 1-12, upstream; plot 12-24, midstream; plot 25-36, downstream.

表2 漓江河岸带群落水平功能性状与环境因子冗余分析(RDA)中的前2轴环境变量解释方差和显著性检验

Table 2 The explained variance of environmental factors and their significant analysis in the first two axes in redundancy analysis (RDA) ordination

环境因子 Environmental factor	RDA₁	RDA₂	R²	p
有机质 Soil organic matter (g·kg^-1)	0.40	0.91	0.34	0.002^**
全氮 Soil total nitrogen (g·kg^-1)	-0.45	0.88	0.19	0.032^*
有效氮 Soil available nitrogen (mg·kg^-1)	-0.74	-0.66	0.57	0.001^***
pH	-0.26	0.96	0.21	0.015^*
干扰强度Disturbance intensity	-0.16	0.98	0.63	0.001^***
距离河岸距离 Distance (m)	-0.85	0.51	0.29	0.004^**
降水量 Precipitation (mm)	-0.66	0.74	0.79	0.001^***
温度 Temperature (℃)	-0.97	0.22	0.50	0.001^***
海拔 Elevation (m)	0.92	-0.38	0.57	0.001^***
河段 Reach	-0.90	0.41	0.88	0.001^***

表3 漓江不同河段功能性状参数值(平均值±标准偏差)

Table 3 Statistics of the three plant functional traits across the three reaches of Lijiang River (mean ± SD)

河段 Reach	功能性状 Functional trait	性状参数 Functional trait parameter
河段 Reach	功能性状 Functional trait	物种性状值 t_i	β 组分 β_i	α 组分 α_i	群落性状值 p_j
上游 Upstream	叶面积 LA (cm²)	1.30 ± 0.35^a	1.36 ± 0.08^a	-0.06 ± 0.34^a	1.34 ± 0.14^ab
	比叶面积 SLA (cm²·g^-1)	2.40 ± 0.13^a	2.40 ± 0.02^a	-0.00 ± 0.13^a	2.39 ± 0.03^a
	木材密度 WD (g·cm^-3)	0.47 ± 0.10^a	0.44 ± 0.02^a	0.03 ± 0.10^a	0.44 ± 0.04^a
中游 Midstream	叶面积 LA (cm²)	1.16 ± 0.32^a	1.24 ± 0.08^b	-0.08 ± 0.27^a	1.26 ± 0.10^a
	比叶面积 SLA (cm²·g^-1)	2.47 ± 0.21^a	2.47 ± 0.06^b	0.01 ± 0.21^a	2.46 ± 0.07^b
	木材密度 WD (g·cm^-3)	0.42 ± 0.12^ab	0.47 ± 0.01^b	-0.04 ± 0.12^a	0.47 ± 0.02^a
下游 Downstream	叶面积 LA (cm²)	1.24 ± 0.32^a	1.45 ± 0.05^c	-0.20 ± 0.30^a	1.46 ± 0.07^b
	比叶面积 SLA (cm²·g^-1)	2.48 ± 0.13^a	2.53 ± 0.02^c	-0.06 ± 0.12^a	2.55 ± 0.03^c
	木材密度 WD (g·cm^-3)	0.36 ± 0.10^b	0.34 ± 0.01^c	0.02 ± 0.10^a	0.34 ± 0.02^b

图3 漓江河岸带植物叶面积(LA)、比叶面积(SLA)和木材密度(WD)在物种性状值(A)、β组分(B)、α组分(C)、样方平均性状值(D)水平上的相关性散点图以及Pearson相关系数(r)。黑色实心点和rm分别代表实际测量数据和实测相关系数, 黑色圆圈和rs分别代表零模型随机模拟999次数据和模拟相关系数。*, p < 0.05; **, p < 0.01。

Fig. 3 Scatterplots showing relationships between leaf area (LA), specific leaf area (SLA) and wood density (WD) for species trait values (A), beta components (B), alpha components (C), and plot mean trait values (D) of the riparian plant of the Lijiang River. The Pearson correlation coefficient (r) of these relationships are shown in each figure. Black solid dots and rm respectively represent observed values and observed correlation coefficient; black open circles and rs respectively represent random simulation values and simulation coefficient. *, p < 0.05; **, p < 0.01.

图4 漓江不同河段植物功能性状β组分的分布范围与零模型比较。圆圈代表零模型预测值; 空心正方形代表实际观测值; 实心正方形代表实际观测值与零模型存在显著差异(p < 0.05)。

Fig. 4 Difference on beta components ranges in the observed and simulated values of the three functional traits at the three reaches in Lijiang River. Circles and squares represent simulated and observed values respectively. Filled squares indicate that the observed values differ significantly from the simulated values.

图5 漓江河岸带植物种内、种间、群落间与河段间(A)及河段内和河段间(B)植物功能性状的方差分解。LA, 叶面积; SLA, 比叶面积; WD, 木材密度。

Fig. 5 Partitioning of the variance in plant functional traits explained by four scales (i.e. within-specie, among-species, communities and reaches) (A) and by two scales (i.e. within and among reaches) (B) of the riparian plant of the Lijiang River. LA, leaf area; SLA, specific leaf area; WD, wood density.

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