退化高寒草地植物多样性和功能群组成与地上生产力的关系

doi:10.17521/cjpe.2024.0143

摘要/Abstract

摘要：

近半个世纪以来, 气候变化和过度放牧等因素导致全球约50%的天然草地发生不同程度退化。草地退化显著改变了植物多样性和群落组成, 进而影响生态系统生产力。然而, 以往关于退化草地多样性与功能群组成对生产力的影响研究主要来自单点尺度, 仍缺乏大尺度的观测证据。为此, 该研究以青藏高原三江源退化高寒草地为研究对象, 基于不同类型草地(高寒草原、高寒草甸和高寒沼泽化草甸) 15个样点45条退化序列的标准化调查和采样, 解析了高寒草地退化过程中植物多样性与功能群组成的变化及其与地上生产力的关联。结果显示, 随退化程度的加剧, 3种类型草地的物种丰富度、Shannon-Weiner多样性指数、Simpson多样性指数和Pielou均匀度指数整体上均呈“先上升后下降”的变化趋势; 整体而言, 群落中莎草科和禾本科植物盖度沿退化梯度显著降低, 豆科植物盖度没有显著变化, 而杂类草盖度均显著增加。进一步分析发现, 退化过程中所有草地类型地上生产力的下降均主要与原生优势种盖度的降低有关, 而植物多样性对生产力的影响较弱。以上结果表明, 从植被的角度而言, 原生群落中优势种盖度的减少而不是多样性的丧失是退化高寒草地植被生产力下降的主要原因, 这一发现也为退化高寒草地恢复提供重要启示: 植被恢复过程中优先恢复原生优势物种是提升退化草地生产力的有效途径。

关键词: 植物多样性, 功能群组成, 植被生产力, 草地退化, 高寒草地

Abstract:

Aims During the past decades, about a half of the global grasslands have been degraded as the results of climate change and anthropogenic activities. Grassland degradation substantially alters plant diversity and community composition; however, it remains elusive how these changes link to ecosystem productivity across broad geographic scales.

Methods Using a standardized survey from 45 grassland degradation sequences at 15 sites across three grassland types (i.e., alpine steppe, alpine meadow and alpine swamp meadow) on the Qingzang Plateau, we aim to explore changes in plant diversity and functional groups upon grassland degradation and their linkages with aboveground net primary productivity (ANPP).

Important findings Across the three grassland types, species richness, Shannon-Weiner diversity index, Simpson diversity index and Pielou evenness index all exhibited a first increase and then decrease pattern as degradation intensified. The coverage of sedge and grass declined, but legume coverage showed no significant changes and forb coverage increased along the degradation gradient. Mixed-effects models showed that degradation-induced change in ANPP was mainly associated with changes in coverage of original dominant species but minimally influenced by plant diversity for all grassland types. These results indicate that the degradation-induced productivity reduction is caused by the decline in dominant species rather than losses of plant diversity. The findings mentioned above provide important clues for alpine grassland restoration: restoring dominant species would be an effective approach for boosting ecosystem productivity in degraded grasslands on the Qingzang Plateau.

Key words: plant diversity, functional groups, vegetation productivity, grassland degradation, alpine grassland

牛亚平, 高晓霞, 姚世庭, 杨元合, 彭云峰. 退化高寒草地植物多样性和功能群组成与地上生产力的关系. 植物生态学报, 2025, 49(1): 83-92. DOI: 10.17521/cjpe.2024.0143

NIU Ya-Ping, GAO Xiao-Xia, YAO Shi-Ting, YANG Yuan-He, PENG Yun-Feng. Linkages of plant diversity and functional groups to aboveground productivity upon alpine grassland degradation. Chinese Journal of Plant Ecology, 2025, 49(1): 83-92. DOI: 10.17521/cjpe.2024.0143

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链接本文: https://www.plant-ecology.com/CN/10.17521/cjpe.2024.0143

https://www.plant-ecology.com/CN/Y2025/V49/I1/83

图/表 5

图1 三江源高寒草地分布区采样点分布图。植被类型图来源于1:100万中国植被图(中国科学院中国植被图编辑委员会, 2007)。

Fig. 1 Location of sampling sites across the Three-River Source Region. The vegetation map is generated from Vegetation Atlas of China with a scale of 1:1 000 000 (The Editorial Committee of Vegetation Map of China, Chinese Academy of Sciences, 2007).

图2 不同草地类型植物物种丰富度(A)、Shannon-Weiner多样性指数(B)、Simpson多样性指数(C)和Pielou均匀度指数(D)与不同功能群盖度(E-H)沿退化梯度的变化(平均值±95%置信区间)。不同小写字母表示同一草地类型各项指标在不同退化程度之间的差异显著(p < 0.05); ns, p > 0.05。

Fig. 2 Changes in species richness (A), Shannon-Weiner diversity index (B), Simpson diversity index (C), Pielou evenness index (D) and coverage of different functional groups (E-H) along degradation gradients in various grassland types (mean ± 95%CI). Different lowercase letters represent significant differences among different degradation levels (p < 0.05); ns, p > 0.05. AM, alpine meadow; AS, alpine steppe; ASM, alpine swamp meadow; HD, heavy degradation; MD, moderate degradation; ND, non-degradation; SD, slight degradation.

表1 不同高寒草地类型土壤理化性质沿退化梯度的变化规律(平均值±标准差)

Table 1 Changes in soil properties along degradation gradients in various alpine grassland types (mean ± SD)

草地类型 Grassland type	退化程度 Degradation level	土壤pH Soil pH	土壤容重 Soil bulk density (g·cm^-3)	土壤含水率 Soil moisture (%)	铵态氮含量 NH₄⁺-N content (mg·kg^-1)	硝态氮含量 NO₃^--N content (mg·kg^-1)
高寒草原 AS	未退化 ND	8.51 ± 0.19^b	1.14 ± 0.17^b	12.34 ± 3.93^a	4.81 ± 1.43^a	4.71 ± 1.90^a
	轻度退化 SD	8.58 ± 0.20^a	1.19 ± 0.15^ab	12.44 ± 3.58^a	4.79 ± 2.02^a	4.18 ± 1.83^ab
	中度退化 MD	8.57 ± 0.17^a	1.24 ± 0.18^ab	11.86 ± 3.37^a	4.32 ± 1.67^a	3.71 ± 1.67^b
	重度退化 HD	8.60 ± 0.18^a	1.26 ± 0.19^a	12.31 ± 2.85^a	3.12 ± 1.47^b	3.54 ± 1.93^b
高寒草甸 AM	未退化 ND	6.71 ± 0.74^b	0.75 ± 0.18^b	48.29 ± 16.05^a	25.44 ± 14.91^a	4.63 ± 3.41^b
	轻度退化 SD	6.77 ± 0.78^b	0.81 ± 0.21^b	45.75 ± 18.23^a	17.03 ± 7.13^b	4.71 ± 3.53^b
	中度退化 MD	7.11 ± 0.78^a	0.93 ± 0.22^a	34.07 ± 11.24^b	13.00 ± 8.13^c	6.41 ± 3.71^a
	重度退化 HD	7.21 ± 0.83^a	0.98 ± 0.22^a	25.47 ± 8.74^c	5.37 ± 3.84^d	7.15 ± 3.74^a
高寒沼泽化草甸 ASM	未退化 ND	6.94 ± 0.72^c	0.44 ± 0.11^c	143.34 ± 28.84^a	23.50 ± 7.61^a	3.10 ± 1.56^b
	轻度退化 SD	7.06 ± 0.81^bc	0.59 ± 0.22^b	109.39 ± 37.27^b	22.77 ± 7.54^a	5.87 ± 5.14^ab
	中度退化 MD	7.17 ± 0.84^b	0.75 ± 0.30^a	83.29 ± 49.36^c	13.69 ± 4.33^b	8.71 ± 9.18^a
	重度退化 HD	7.37 ± 0.74^a	0.89 ± 0.24^a	47.22 ± 34.12^d	4.27 ± 1.32^c	10.18 ± 6.25^a

图3 不同草地类型植物多样性和不同功能群盖度与环境因子的关系。为了消除样点之间的空间异质性, 采用因变量和自变量的响应比(退化与未退化样点比值的自然对数)进行回归分析。*, p < 0.05; **, p < 0.01; ***, p < 0.001。

Fig. 3 Relationships of plant diversity and coverage of functional groups with environmental factors along degradation gradients in different grassland types. The response ratio, which was calculated as the natural logarithm of the ratio of degradation plots to non-degradation plots, was used in regression analysis to account for spatial heterogeneity among different sampling sites. AM, alpine meadow; AS, alpine steppe; ASM, alpine swamp meadow; MAP, mean annual precipitation; MAT, mean annual air temperature. *, p < 0.05; **, p < 0.01; ***, p < 0.001.

图4 不同草地类型地上生产力沿退化梯度的变化(A, 平均值±95%置信区间), 地上生产力与多样性和不同功能群盖度的关系(B)和基于随机森林分析的解释变量对植物多样性和功能群盖度影响的相对重要性(C)。A中不同小写字母表示地上生产力在不同退化程度之间的差异显著性(p < 0.05)。B中实心圈表示两个变量之间相关性显著, 空心圈表示相关不显著, 误差线表示95%置信区间。C中为了消除样点之间的空间异质性, 采用因变量和自变量的响应比(退化与未退化样点比值的自然对数)进行回归分析和随机森林分析。

Fig. 4 Changes in aboveground net primary productivity (ANPP) along degradation gradients in various grassland types (A, mean ± 95% CI), relationships of ANPP with plant diversity and coverage of functional groups (B), and moderators of ANPP based on relative influence of predictor variables in the random forest model (C). In A, different lowercase letters represent significant difference among different degradation levels (p < 0.05). In B, the solid circles indicate significant effects (p < 0.05), the hollow circles indicate non-significant effects (p > 0.05) and the error bars denote 95% confidence intervals. In C, the response ratio, which was calculated as the natural logarithm of the ratio of degradation plots to non-degradation plots, was used in univariate regression and random forest analyses to account for spatial heterogeneity among different sampling sites. AM, alpine meadow; AS, alpine steppe; ASM, alpine swamp meadow; HD, heavy degradation; MAP, mean annual precipitation; MAT, mean annual air temperature; MD, moderate degradation; ND, non-degradation; SD, slight degradation.

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