土壤细菌群落特征对高寒草甸退化的响应

doi:10.17520/biods.2020137

摘要/Abstract

摘要：

为明确高寒草甸土壤细菌物种组成及功能结构对草地环境恶化的响应规律, 本文采用高通量基因测序技术对高寒草甸未退化、轻度退化、中度退化、重度退化和极重度退化草地土壤细菌的组成、格局和功能进行了研究。结果表明: 高寒草甸土壤优势细菌为酸杆菌门、放线菌门、浮霉菌门、变形菌门和疣微菌门, 在土壤细菌中占比分别为16%‒18%、9%‒12%、12%‒14%、23%‒29%和11%‒12%。退化草地中土壤细菌物种组成明显改变, 变形菌门细菌丰度降低, 酸杆菌门和浮霉菌门丰度增加, 不同草地科水平细菌丰度差异因土层而异。草地退化对细菌Chao1指数无影响, 轻度退化提高了细菌Simpson指数, 重度退化草地土壤细菌Shannon-Wiener指数最高。Faprotax细菌功能分组以化能异养、硝化作用、亚硝酸盐氧化及硫代谢作用为主, 草地退化改变了微生物介导的碳循环、氮循环、硫循环、铁循环和锰循环。重度及极重度退化提高了细菌氨氧化功能作用, 降低了硫化物、亚硝酸盐氧化及尿素水解作用; 草地退化过程中细菌化能异养、芳香族化合物降解及反硝化作用功能等均呈先降低后升高的变化趋势, 中度退化阶段是微生物群落生态功能结构转变的拐点。高寒草甸退化改变了土壤细菌的群落及功能结构, 土壤含水量、pH、总有机碳、全氮、全钾和有效氮磷比是土壤细菌群落及功能结构变化的主要驱动因子。

关键词: 退化高寒草甸, 土壤细菌, 物种组成, 群落特征, 生态功能结构

Abstract:

Aim: This study aims to clarify the response of soil bacterial species composition, pattern, and functional structure to a range of grassland degradation in alpine meadows.
Methods: Degraded alpine meadows at five stages (including non-degraded, light-degraded, moderate-degraded, severe-degraded, and extreme-degraded) were selected in 2017 by the classification standard in the Three-River-Source. Four different plots at each degraded stages were set as replications, and the area of each plot is about 80 m². Soil microbial characteristics were analyzed by high-throughput gene detection, and the soil physical and chemical properties were analyzed by conventional methods.
Results: Acidobacteria, Actinobacteria, Planctomycetes, Proteobacteria and Verrucomicrobia were the dominant bacteria in alpine meadow soil, accounting for 16%‒18%、9%‒12%、12%‒14%、23%‒29% and 11%‒12%of the total soil bacteria abundance, respectively. The soil bacterial species compositions changed substantially with increasing grassland degradation: Proteobacteria abundance decreased, while Acidobacteria and Planctomycetes abundance increased significantly with increasing degradation. Furthermore, the number of taxa (at the family level) differed across the diverse soil layers in degraded alpine meadows. Grassland degradation had no effect on bacterial diversity, as measured by the Chao1 index, but alpine medow that were lightly degraded increased bacterial diversity, as measured by the Simpson index. Soil bacterial diversity, as measured by the Shannon-Wiener index, was greatest in severe-degraded grasslands. The Faprotax functions were mainly composed by the processes of Chemoheterotrophy, nitrification, nitrite oxidation, and sulfur metabolism. Grassland degradation altered the carbon, nitrogen, sulfur, iron and manganese cycles, which were mediated by microorganisms. Severe and extreme degradation increased the bacterial ammonia-oxidizing function, and decreased the functions of sulfide, nitrite oxidation, and ureolysis. Across the gradient of grassland degradation, the bacteriological Chemoheterotrophy, aromatic compounds degradation, and the denitrification functions all initially decreased before subsequently increasing; moderate stages of degradation stage represented turning points of the bacterial community in terms of ecological functional structure changes.
Conclusion: Alpine meadow degradation altered the soil bacterial community and functional structures. The main driving factors for differences in soil bacterial community and functional structures were soil moisture content, pH, total organic carbon, total nitrogen, total potassium, and the ratio of available nitrogen and phosphorus.

Key words: grassland degradation, soil bacteria, species composition, diversity, community characteristics, ecological functional structures

李世雄, 王彦龙, 王玉琴, 尹亚丽. 土壤细菌群落特征对高寒草甸退化的响应[J]. 生物多样性, 2021, 29(1): 53-64.

Shixiong Li, Yanlong Wang, Yuqin Wang, Yali Yin. Response of soil bacterial community characteristics to alpine meadow degradation[J]. Biodiv Sci, 2021, 29(1): 53-64.

图/表 8

表1 不同退化程度高寒草甸土壤细菌α-多样性

Table 1 Soil bacterial α-diversity in different degraded alpine meadows

土层深度 Soil depth	退化程度 Degradation degree	多样性指数 Diversity index
土层深度 Soil depth	退化程度 Degradation degree	Chao1	Shannon-Wiener index	Simpson index
0?10 cm	未退化 Non-degradation	8,828.18 ± 363.61^a	10.31 ± 0.15^c	0.997 ± 0.001^bc
	轻度退化 Light-degradation	9,015.26 ± 2,567.38^a	10.54 ± 0.13^ab	0.998 ± 0.000^a
	中度退化 Moderate-degradation	9,904.47 ± 490.73^a	10.32 ± 0.05^bc	0.997 ± 0.000^abc
	重度退化 Severe-degradation	11,054.59 ± 1,330.52^a	10.63 ± 0.07^a	0.997 ± 0.000^ab
	极重度退化 Extreme-degradation	9,517.00 ± 1,023.90^a	10.52 ± 0.18^abc	0.996 ± 0.001^c
10?20 cm	未退化 Non-degradation	7,686.14 ± 636.88^a	9.95 ± 0.19^cd	0.996 ± 0.000^c
	轻度退化 Light-degradation	8,022.41 ± 1,254.05^a	10.19 ± 0.15^bc	0.997 ± 0.000^b
	中度退化 Moderate-degradation	7,251.09 ± 706.01^a	9.91 ± 0.05^d	0.996 ± 0.000^c
	重度退化 Severe-degradation	8,891.85 ± 1,224.30^a	10.48 ± 0.11^a	0.998 ± 0.000^a
	极重度退化 Extreme-degradation	8,756.00 ± 1,594.71^a	10.29 ± 0.22^ab	0.997 ± 0.000^b

图1 不同退化程度高寒草甸土壤细菌门水平的相对丰度。图中1和2分别代表0?10 cm和10?20 cm土层。

Fig. 1 Soil bacterial relative abundance at the phylum level in different degraded alpine meadows. Numbers 1 and 2 in the figure represent 0?10 cm and 10?20 cm soil layer, respectively.

图2 不同退化程度高寒草甸0-10 cm土壤科水平细菌丰度差异。* P < 0.05。

Fig. 2 The soil bacterial abundance in family level at soil depth of 0?10 cm in different degraded alpine meadows. *P < 0.05.

图3 不同退化程度高寒草甸10?20 cm土壤科水平细菌丰度差异。* P < 0.05。

Fig. 3 The soil bacterial abundance in family level at soil depth of 10?20 cm in different degraded alpine meadows. *P < 0.05.

图4 不同退化程度高寒草甸土壤细菌生态功能多样性。图中1和2分别代表0?10 cm和10?20 cm土层。*P < 0.05。

Fig. 4 Ecological functiona diversity of soil bacterial community in different degraded alpine meadows. Numbers 1 and 2 in the figure represent 0?10 cm and 10?20 cm soil layer, respectively. *P < 0.05.

图5 不同退化程度高寒草甸土壤细菌群落结构

Fig. 5 Soil bacterial community structures in different degraded alpine meadows

表2 植被特征、土壤性质与土壤细菌群落结构的Mantel test分析

Table 2 Mantel test analysis of plant community characters, soil properties and soil bacterial community composition in an alpine meadow

指标 Item	细菌群落结构 Bacterial community composition		Faprotax生态功能结构 Faprotax ecological functional structure
指标 Item	r	P	r	P
植物Shannon-Wiener指数 Shannon-Wiener index	-0.01	0.52	0.07	0.23
物种丰富度 Species richness	0.12	0.12	0.02	0.39
植被盖度 Coverage	0.02	0.38	0.08	0.23
地上生物量 Above-ground biomass	0.04	0.32	0.12	0.14
地下生物量 Below-ground biomass	-0.04	0.62	?0.08	0.09
土壤含水量 SWC	0.17	0.02	0.18	0.02
土壤酸碱度 pH	0.19	0.02	0.18	0.04
总有机碳 TOC	0.17	0.03	0.21	0.02
全氮 TN	0.17	0.03	0.17	0.03
铵态氮 NH₄⁺-N	0.05	0.22	0.23	0.008
硝态氮 NO₃^--N	0.11	0.09	0.14	0.06
全磷 TP	0.10	0.11	0.15	0.09
速效磷 AP	0.09	0.17	0.10	0.20
全钾 TK	0.22	0.006	0.21	0.02
速效钾 AK	0.07	0.19	﹣0.04	0.61
土壤有效氮磷比AN/AP	0.15	0.048	0.20	0.03
土壤碳氮比 C/N	0.18	0.05	0.09	0.22

图6 高寒草甸土壤和植被环境因子与土壤细菌群落的冗余分析。圆圈表示环境因子, 圆中的数字表示解释率, 中心椭圆的数字表示两个环境因子的共同解释率。

Fig. 6 Redundancy analysis of soil and vegetation environmental factors to soil bacterial community in an alpine meadow. The circles show the variation explained by each factor alone. The number in the ellipse represents interactions of the two factors.

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