草甸草原羊草茎叶功能性状对长期过度放牧的可塑性响应

doi:10.3724/SP.J.1258.2014.00040

摘要/Abstract

摘要：

植物对不同功能性状进行权衡, 通过表型可塑性达到对异质生境的适应是植物的一种生态对策。羊草(Leymus chinensis)是欧亚温带草原东缘的主要优势植物, 研究其对放牧的表型反应对揭示草原生态系统的放牧响应机制具有代表意义。该文以内蒙古呼伦贝尔草甸草原为例, 通过设置不同放牧压力与围封的长期试验, 研究了羊草茎叶功能性状对放牧的可塑性响应模式。结果表明: 1)与长期围封相比, 长期放牧导致羊草茎叶性状显著小型化, 其中, 株高和个体地上生物量分别降低76.82%和89.88%, 但3年短期围封对茎性状影响不显著, 说明羊草表型矮小化现象具有一定的保守性; 2)通过排序构建羊草性状可塑性变化谱, 发现茎质量、总质量、茎高、株高、叶面积等为对放牧响应的敏感性状, 而叶片数、茎粗、叶宽等较为稳定, 为惰性性状; 3)放牧干扰下, 羊草性状可塑性程度与其变异性之间符合y = y₀ + ae^bx拟合关系, 随着植物性状的响应强度增大, 其变异性增强; 4)偏最小二乘法分析发现茎长、株高、叶面积、叶长等性状的投影重要性指标大于1, 对地上生物量变化的解释率为68.6%, 是导致长期放牧下羊草个体生物量降低的主要因子。研究认为, 矮化型变是羊草的避牧适应对策, 在亚稳态下, 通过不同性状的权衡, 充分利用环境资源完成其生活史。

关键词: 功能性状, 羊草, 草甸草原, 过度放牧, 表型可塑性, 草原植物矮小化

Abstract:

Aims Adaptation of plants to their habitats through phenotypic plasticity in which they trade off various kinds of functional traits is an important ecological strategy. Whereas plant functional traits and its effects on grassland ecosystem functioning have received much attention, the importance of grazing effects on functional traits is poorly understood. This study, therefore, aimed to analyze the responding model of Leymus chinensis functional traits to long-term grazing in semi-arid grassland.
Methods The study was conducted in a field experiment involving treatments with various grazing and enclosure schemes in Nei Mongol. We compared the effects of long-term enclosure, short-term enclosure (SE), moderate grazing (MG), and heavy grazing on plant functional traits in L. chinensis. Partial Least Squares Regression was used to analyze the contributions of controlling factors on changes in biomass in response to grazing.
Important findings The size of L. chinensis became smaller in plots subject to long-term grazing compared with in the plots of enclosures. It had a significant conservative property of plant dwarf which can be found in the SE plot. Interestingly, the variability increased significantly with the increasing of plasticity index of different functional traits. Also, some functional traits, such as aboveground biomass, plant height, mean leaf length etc., were sensitive traits to grazing. However, other indicators, such as leaf numbers, stem diameter, mean leaf width etc., which were inert functional traits. Stem length, plant height and other traits were main factors which cased the decreasing of L. chinensis aboveground biomass. On the whole, phenotypic change is an important adaptive strategy of L. chinensis to long term grazing.

Key words: functional trait, Leymus chinensis, meadow steppe, overgrazing, phenotypic plasticity, plant dwarf of grassland

李西良,侯向阳,吴新宏,萨茹拉,纪磊,陈海军,刘志英,丁勇. 草甸草原羊草茎叶功能性状对长期过度放牧的可塑性响应. 植物生态学报, 2014, 38(5): 440-451. DOI: 10.3724/SP.J.1258.2014.00040

LI Xi-Liang,HOU Xiang-Yang,WU Xin-Hong,null null,JI Lei,CHEN Hai-Jun,LIU Zhi-Ying,DING Yong. Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe. Chinese Journal of Plant Ecology, 2014, 38(5): 440-451. DOI: 10.3724/SP.J.1258.2014.00040

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链接本文: https://www.plant-ecology.com/CN/10.3724/SP.J.1258.2014.00040

https://www.plant-ecology.com/CN/Y2014/V38/I5/440

图/表 10

图1 研究样地分布图。

Fig. 1 Distribution map of the research site.

图2 围封与放牧对羊草叶片表型性状的影响(平均值±标准误差)。LA, 单叶面积; LL, 平均叶长; LLW, 叶平均长宽比; LMA, 比叶质量; LN, 叶片数; LW, 平均叶宽; LWE, 单叶质量; TLA, 总叶面积; TLW, 总叶质量。样地同图1。不同小写字母表示差异显著(p < 0.05)。

Fig. 2 Effects of enclosure and grazing to leaf phenotypic trait of Leymus chinensis (mean ± SE). LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, mean leaf width; LWE, leaf mass; TLA, total leaf area; TLW, total leaf mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

图3 围封与放牧对羊草茎表型性状的影响(平均值±标准误差)。SD, 茎粗; SL, 茎长; SLD, 茎长/茎粗; SW, 茎质量。样地同图1。不同小写字母表示差异显著(p < 0.05)。

Fig. 3 Effects of enclosure and grazing to stem phenotypic trait of Leymus chinensis (mean ± SE). SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SW, stem mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

图4 围封与放牧对羊草全株功能性状的影响(平均值±标准误差)。AB, 总质量; PH, 株高; SLW, 茎质量/叶质量。样地同图1。不同小写字母表示差异显著(p < 0.05)。

Fig. 4 Effects of enclosure and grazing to functional traits of Leymus chinensis (mean ± SE). AB, aboveground biomass; PH, plant height; SLW, stem mass/leaf mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

图5 短期围封(SE)、中度放牧(MG)与重度放牧(HG)下羊草茎叶性状可塑性指数(PI)变化程度排序。AB, 总质量; LA, 单叶面积; LL, 平均叶长; LLW, 平均长宽比; LMA, 比叶质量; LN, 叶片数; LW, 平均叶宽; LWE, 单叶质量; PH, 株高; SD, 茎粗; SL, 茎长; SLD, 茎长/茎粗; SLW, 茎质量/叶质量; SW, 茎质量; TLA, 总叶面积; TLW, 叶质量。

Fig. 5 Sorting of Leymus chinensis leaf and stem trait plasticity index (PI) change in short-term enclosure (SE), moderate grazing (MG) and heavy degree grazing (HG). AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

图6 羊草不同茎叶功能性状变异性比较。AB, 总质量; LA, 单叶面积; LL, 平均叶长; LLW, 平均长宽比; LMA, 比叶质量; LN, 叶片数; LW, 平均叶宽; LWE, 单叶质量; PH, 株高; SD, 茎粗; SL, 茎长; SLD, 茎长/茎粗; SLW, 茎质量/叶质量; SW, 茎质量; TLA, 总叶面积; TLW, 叶质量。

Fig. 6 Comparisons of variation in leaf and stem functional traits in Leymus chinensis. AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

图7 羊草不同茎叶功能性状变异系数(CV)与可塑性指数(PI)的关系。

Fig. 7 Relationships between variation of coefficient (CV) and plasticity index (PI) of functional traits in Leymus chinensis.

表1 羊草茎叶表型性状之间的协同变化关系

Table 1 The coordinated variation of Leymus chinensis leaf and stem phenotypic traits

	PH	LN	LL	LW	LLW	TLA	LA	SL	SD	SLD
PH	1.00
LN	0.20	1.00
LL	0.94^**	0.12	1.00
LW	0.70^**	0.11	0.75^**	1.00
LLW	0.84^**	0.08	0.88^**	0.37^**	1.00
TLA	0.92^**	0.32^*	0.94^**	0.81^**	0.75^**	1.00
LA	0.91^**	0.08	0.97^**	0.84^**	0.77^**	0.96^**	1.00
SL	0.98^**	0.24	0.92^**	0.68^**	0.81^**	0.91^**	0.89^**	1.00
SD	0.64^**	0.01	0.66^**	0.76^**	0.37^**	0.70^**	0.73^**	0.63^**	1.00
SLD	0.95^**	0.28^*	0.87^**	0.57^**	0.83^**	0.85^**	0.82^**	0.96^**	0.44^**	1.00

图8 羊草个体地上生物量与茎叶性状之间的回归关系。AB, 总质量; LA, 单叶面积; LL, 平均叶长; LLW, 平均长宽比; LMA, 比叶质量; LN, 叶片数; LW, 平均叶宽; LWE, 单叶质量; PH, 株高; SD, 茎粗; SL, 茎长; SLD, 茎长/茎粗; SLW, 茎质量/叶质量; SW, 茎质量; TLA, 总叶面积; TLW, 叶质量。

Fig. 8 Regression fitting of Leymus chinensis individual aboveground biomass and functional traits. AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

图9 羊草个体地上生物量与生物量组分(A)、功能性状(B)的投影重要性指标(VIP)(平均值±标准误差)(柱状图)影响要素权重(饼图)。LA, 单叶面积; LL, 平均叶长; LLW, 平均长宽比; LMA, 比叶质量; LN, 叶片数; LW, 平均叶宽; LWE, 单叶质量; PH, 株高; SD, 茎粗; SL, 茎长; SLD, 茎长/茎粗; SLW, 茎质量/叶质量; SW, 茎质量; TLA, 总叶面积; TLW, 叶质量。

Fig. 9 The variable importance in projection values (VIP) (mean ± SE) (bar charts) and weights of influential factors (pie charts) of individual aboveground biomass by the biomass components (A) and functional traits (B). LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

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