【作者】 汪洋；

【导师】 安黎哲； 陈书燕；

【作者基本信息】 兰州大学 ， 生物学·植物学， 2023， 硕士

【摘要】 高寒草甸作为青藏高原地区主要植被类型,近年来频遭气候变暖影响,由此导致高寒草甸灌木扩张现象明显,这对土壤生物群落多样性和组成产生了重大影响。土壤微生物和土壤线虫群落是土壤生物群落重要组成部分,对土壤生态系统稳定性有重要影响。研究已发现优势灌木扩张能显著改变土壤生物群落多样性和组成,但这些研究大多集中探讨单一优势灌木对土壤细菌、土壤真菌和土壤线虫群落的影响,而对不同优势灌木对土壤细菌、土壤真菌和土壤线虫群落的研究则较少,难以准确揭示不同优势灌木对土壤生物群落影响的差异性及其机制。本研究以青藏高原东南部高寒草甸地区优势灌木金露梅(Dasiphora Fruticosa)、山生柳(Salix oritrepha)和头花杜鹃(Rhododendron capitatum)下土壤中的细菌、真菌和线虫为研究对象。通过单因素方差分析,探究不同优势灌木对土壤理化性质的影响及差异,以及不同优势灌木对土壤细菌、土壤真菌和土壤线虫群落多样性和组成的影响及差异。通过斯皮尔曼相关分析探究土壤细菌、土壤真菌和土壤线虫群落与土壤理化性质间的相关性。通过非度量多维尺度分析和冗余分析探究不同优势灌木下土壤中的细菌、真菌和线虫群落与土壤理化性质之间的关系,研究表明:(1)土壤硝态氮含量在金露梅灌丛显著高于山生柳灌丛(P<0.01),高出58.25%。土壤总氮含量在头花杜鹃灌丛显著高于山生柳灌丛(P<0.05),高出20.49%。土壤铵态氮含量在山生柳灌丛显著高于金露梅灌丛(P<0.1),高出31.17%。其它土壤理化性质在不同优势灌木下土壤中无显著差异。(2)不同优势灌木下土壤中细菌群落的丰富度和香农多样性没有显著差异,生物量在头花杜鹃灌丛显著高于山生柳灌丛(P<0.001),高出202.29%。斯皮尔曼相关分析表明土壤细菌群落生物量与土壤总氮含量存在显著正相关关系。优势灌木对土壤细菌的群落组成影响显著,头花杜鹃相比金露梅显著提高了土壤中变形菌门相对多度;金露梅相比头花杜鹃显著提高了硝化螺旋菌门的相对多度。冗余分析结果表明影响土壤细菌群落组成最关键的土壤理化性质是铵态氮。斯皮尔曼相关分析表明变形菌门相对多度与土壤硝态氮含量显著负相关;硝化螺旋菌门相对多度与土壤铵态氮含量显著负相关,与土壤硝态氮含量显著正相关。(3)土壤真菌群落的丰富度在金露梅灌丛显著高于头花杜鹃灌丛(P<0.05),高出22.89%,香农多样性和生物量没有显著差异。斯皮尔曼相关分析表明土壤真菌群落丰富度与土壤总氮含量之间呈现显著负相关,而与土壤硝态氮含量之间则呈现显著正相关。不同优势灌木对土壤真菌群落组成有显著影响,金露梅相比于山生柳显著提高了土壤中被孢霉门和球囊菌门相对多度。冗余分析结果表明影响土壤真菌群落组成最关键的土壤理化性质是铵态氮。斯皮尔曼相关分析表明被孢霉门相对多度与土壤铵态氮含量呈现显著负相关,与土壤硝态氮含量呈现显著正相关;球囊菌门相对多度与土壤硝态氮含量呈现显著正相关。(4)不同优势灌木下土壤中线虫群落的丰富度和香农多样性没有显著差异,多度和生物量存在边缘显著差异(P<0.1)。山生柳相比于头花杜鹃边缘显著提升植食性土壤线虫丰富度(P<0.1),显著提升了植食性土壤线虫香农多样性(P<0.01),边缘显著提升了捕食-杂食性土壤线虫多度和生物量(P<0.1)。斯皮尔曼相关分析表明土壤线虫多度与土壤含水量和土壤总磷含量存在显著负相关;土壤线虫生物量与土壤总磷含量间存在显著负相关。不同优势灌木对土壤线虫群落组成有显著影响,山生柳相比于头花杜鹃显著提高了原矛线属多度。冗余分析结果表明影响土壤线虫群落组成最关键的土壤理化性质是土壤总氮和土壤含水量。斯皮尔曼相关分析表明原矛线属多度与土壤总氮含量间显著负相关。土壤线虫群落基础指数BI在不同优势灌木处理中存在边缘显著差异(P<0.1),表现为头花杜鹃要显著高于山生柳。综上所述,优势灌木对土壤细菌、土壤真菌和土壤线虫的多样性和群落组成有显著影响,且这种影响与土壤理化性质密切相关。优势灌木显著改变了土壤细菌生物量,且头花杜鹃灌丛下土壤细菌生物量较高,这可能和土壤细菌生物量与土壤总氮含量的显著正相关关系有关。优势灌木显著改变了土壤真菌群落丰富度,且金露梅灌丛下土壤真菌群落丰富度较高,这可能和土壤真菌群落丰富度与硝态氮含量的显著正相关关系有关。优势灌木对土壤线虫的多度和生物量存在显著影响,这可能和土壤含水量,土壤总磷含量有关。我们的研究结果对探索不同优势灌木影响土壤生物多样性和群落组成的机制具有重要意义,加深了我们对灌木扩张影响地下生物群落多样性机制的理解,同时也为青藏高原高寒草甸的土壤生物多样性保护和土壤生态功能的维持提供一定的理论支持。更多还原

【Abstract】 As main vegetation type of Qinghai-Tibet Plateau,alpine meadow had been frequently affected by climate warming in recent years,and then shrubs in alpine meadow had obvious expansion trends,which had significant impacts on diversity and community composition of soil biome.Soil microbes and nematodes are important parts of soil biome,they are essential in maintaining stability of soil ecosystems.Previous studies have found expansion of dominant shrubs can change structure and diversity of soil biome,but most of these studies have focused on effects of single dominant shrub on soil bacterial,soil fungal and soil nematode community,while fewer studies have examined the effects of different dominant shrubs on soil bacterial,soil fungal and soil nematode communities,so as to difficult to accurately reveal the difference and mechanism in impacts of different dominant shrubs on soil biological community.We chose bacteria,fungi,and nematode in soil of dominant shrubs,such as Dasiphora Fruticosa,Salix oritrepha,and Rhododendron capitatum in alpine meadow of southeast Qinghai-Tibet Plateau as our experimental objects.We used One-way ANOVA to explore different effects of dominant shrubs on edaphic properties,and on diversity,community composition of soil bacterial,fungal and nematode community.Rrelationships between soil bacteria,fungal,nematode community and edaphic properties were analyzed through Spearman correlation analysis.Different effects of dominant shrubs on community composition of soil bacteria,fungi and nematode and the key edaphic properties of dominant shrubs affecting soil bacterial,fungal and nematode communities were analyzed by nonmetric multidimensional scaling and redundancy analysis.Our study found that:(1)Dasiphora fruticose significantly promoted soil nitrate content by 58.25 %compared with Salix oritreph(P < 0.01).Rhododendron capitatum significantly promoted total nitrogen content by 20.49% compared with Salix oritreph(P < 0.05).Salix oritreph significantly promoted soil ammonium content by 31.17 % compared with Dasiphora fruticose(P < 0.1).Other edaphic properties had no significant difference in different dominant shrub soil.(2)The richness and Shannon diversity of soil bacterial community had no significant difference in different shrub soil,Rhododendron capitatum significantly promoted bacterial biomass by 202.29 % compared with Salix oritreph(P < 0.001).Results of Spearman correlation showed soil bacterial biomass was significantly positive correlated with soil total nitrogen content.Dominant shrubs had significant impacts on soil bacterial community composition.Rhododendron capitatum significantly promoted the relative abundance of Proteobacteria compared with Dasiphora fruticosa.Dasiphora fruticosa significantly promoted the relative abundance of Nitrospirae compared with Rhododendron capitatum.Results of RDA showed the most critical edaphic property of dominant shrubs affecting soil bacterial community composition was soil ammonium content.Results of Spearman correlation showed the relative abundance of Proteobacteria was significantly negative correlated with soil nitrate content;the relative abundance of Nitrospirae was significantly negative correlated with soil ammonium content,significantly positive correlated with soil nitrate content.(3)Dasiphora fruticosa significantly promoted soil fungal community richness by 22.89 % compared with Rhododendron capitatum(P < 0.05),Shannon diversity and biomass had not significant difference.Results of Spearman correlation showed soil fungal community richness was significantly negative correlated with total nitrogen content and significantly positive correlated with soil nitrate nitrogen content.Different dominant shrubs had significant impacts on soil fungal community composition.Dasiphora fruticosa significantly promoted the relative abundance of Mortierellomycota and Glomeromycota compared with Salix oritreph.Results of RDA showed the most critical edaphic property of dominant shrubs affecting soil fungal community composition was soil ammonium content.Results of Spearman correlation showed the relative abundance of Mortierellomycota was significantly negative correlated with soil ammonium content,significantly positive correlated with soil nitrate content;the relative abundance of Glomeromycota was significantly positive correlated with soil nitrate content.(4)The richness and Shannon diversity of soil nematode community had no significant difference in different dominant shrub soil,but abundance and biomass had marginally significant difference(P < 0.1).Salix oritreph marginally significant promoted plant feeder nematode richness(P < 0.1),significantly promoted Shannon diversity(P < 0.01),marginally significant promoted predator-omnivorous feeder nematode abundance and biomass(P < 0.1)compared with Rhododendron capitatum.Results of Spearman correlation showed soil nematode abundance was negatively correlated with soil water content and total phosphorus content;soil nematode biomass was negatively correlated with soil total phosphorus content.Dominant shrubs had significant impacts on nematode community composition,Salix oritreph significantly promoted abundance of Prodorylaimium compared with Rhododendron capitatum.Results of RDA showed most critical edaphic properties of dominant shrubs affecting nematode community composition were soil total nitrogen content and water content.Results of Spearman correlation showed abundance of Prodorylaimium was significantly negative correlated with soil tatal nitrogen content.Basal index(BI)of soil nematode community in soil of Rhododendron capitatum was marginally higher than Salix oritreph(P < 0.1).In conclusion,dominant shrubs had significant effects on diversity and community composition of soil bacteria,fungi and nematode,and these impacts were closely related to edaphic properties.Dominant shrubs had greater impacts on biomass of soil bacteria,bacterial biomass was higher in soil of Rhododendron capitatum,these impacts may be caused by positive relationship between soil total nitrogen content and bacterial biomass.Dominant shrubs had greater impacts on richness of soil fungal community,and fungal community richness was higher in soil of Dasiphora fruticose,these impacts may be caused by positive relationship between soil total nitrate content and fungal richness.Dominant shrubs had greater impacts on abundance and biomass of soil nematode,these impacts may be related to soil water content and phosphorus content.Our results are of great importance for mechanism exploration of effects of different dominant shrubs on soil biome diversity and community composition,this also can deepen our understanding of the mechanisms by which shrub expansion affect belowground biome diversity,and also provide theoretical support for soil biodiversity conservation and maintenance of soil ecological functions in alpine meadow of Qinghai-Tibet Plateau.更多还原