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增温对高寒草甸土壤微生物多样性及功能潜力的影响

吴菲, 高章伟, 张睿博, 时蓉喜, 刘梦洁, 胡健, 汪辉, 周青平

吴菲, 高章伟, 张睿博, 时蓉喜, 刘梦洁, 胡健, 汪辉, 周青平. 增温对高寒草甸土壤微生物多样性及功能潜力的影响[J]. 北京林业大学学报, 2025, 47(1): 29-38. DOI: 10.12171/j.1000-1522.20240064
引用本文: 吴菲, 高章伟, 张睿博, 时蓉喜, 刘梦洁, 胡健, 汪辉, 周青平. 增温对高寒草甸土壤微生物多样性及功能潜力的影响[J]. 北京林业大学学报, 2025, 47(1): 29-38. DOI: 10.12171/j.1000-1522.20240064
Wu Fei, Gao Zhangwei, Zhang Ruibo, Shi Rongxi, Liu Mengjie, Hu Jian, Wang Hui, Zhou Qingping. Effects of warming on soil microbial diversity and functional potential in alpine meadows[J]. Journal of Beijing Forestry University, 2025, 47(1): 29-38. DOI: 10.12171/j.1000-1522.20240064
Citation: Wu Fei, Gao Zhangwei, Zhang Ruibo, Shi Rongxi, Liu Mengjie, Hu Jian, Wang Hui, Zhou Qingping. Effects of warming on soil microbial diversity and functional potential in alpine meadows[J]. Journal of Beijing Forestry University, 2025, 47(1): 29-38. DOI: 10.12171/j.1000-1522.20240064

增温对高寒草甸土壤微生物多样性及功能潜力的影响

基金项目: 四川若尔盖高寒湿地生态系统国家野外科学观测研究站开放课题(ZAW01),国家自然科学基金项目(32171593),西南民族大学中央高校基本科研业务费专项(2023NYXXS087)。
详细信息
    作者简介:

    吴菲。主要研究方向:生态系统功能与全球变化。Email:feiwu_027@163.com 地址:610225 四川省成都市双流区航空港开发区大件路文星段168号

    责任作者:

    周青平,教授。主要研究方向:牧草育种栽培、草地培育改良和高原草地生态环境治理。Email:qpingzh@aliyun.com 地址:同上。

  • 中图分类号: S812.2

Effects of warming on soil microbial diversity and functional potential in alpine meadows

  • 摘要:
    目的 

    本文旨在探究青藏高原高寒草甸生态系统中不同土壤微生物类群的多样性及其功能潜力对气候变暖的响应特征及机理。

    方法 

    基于为期6年的野外增温控制试验,利用不同功率红外加热设置对照、增低温(+1.5 ℃)和增高温(+2.5 ℃) 3个温度处理。增温6年后于2020年8月采集土壤表层样品,利用微生物高通量测序,分析土壤细菌和真菌群落对增温的响应。

    结果 

    (1)增低温和增高温处理分别使土壤表层温度升高了1.4 ℃和2.4 ℃(P < 0.05),土壤湿度分别下降了11%和17%(P < 0.05)。相比对照,土壤硝态氮含量在增低温和增高温处理下分别降低了66%和72%(P < 0.05),而土壤有效磷含量仅在增高温处理下显著增加36%(P < 0.05)。(2)增温处理显著降低了土壤细菌α多样性及谱系多样性,并改变了细菌群落结构(P < 0.05);相比之下,土壤真菌以上指标均未表现出显著变化。(3)土壤细菌群落中,碳水化合物代谢及全局概览图等功能分类在增高温处理下明显增强,而土壤真菌共生营养型、病理营养型以及腐生营养型的功能丰度并未受显著影响。(4)土壤细菌功能潜力与土壤总氮含量和土壤有效磷含量呈显著正相关(P < 0.05),真菌功能潜力仅与谱系多样性呈显著正相关(P < 0.05),且与土壤理化性质无显著相关性。

    结论 

    增温显著降低了土壤细菌α多样性和谱系多样性,改变了细菌群落结构;增温通过调控土壤有效磷含量进而促进细菌群落在碳水化合物代谢等功能潜力的表达;相比之下,增温并未显著影响土壤真菌多样性、群落结构和功能潜力。研究结果表明土壤细菌群落与真菌群落对气候变暖响应的敏感性存在差异,可能对生态系统功能产生不同影响。

    Abstract:
    Objective 

    This study aimed to explore the response patterns of soil microbial diversity and their functional potentials to different warming levels in an alpine ecosystem on the Qinghai-Tibet Plateau of western China.

    Method 

    We conducted a field manipulation warming experiment using infrared heating methods to set three warming treatments, including control, low-level warming (+1.5 ℃) and high-level warming (+2.5 ℃). Through soil microbial high-throughput sequencing analysis, we investigated the general patterns and mechanisms underlying soil bacterial and fungi communities in response to field warming.

    Result 

    (1) Low-level warming and high-level warming significantly increased soil temperature in the topsoil by 1.4 and 2.4 ℃, and decreased soil moisture by 11% and 17%, respectively (P < 0.05). In contrast to the control, soil nitrate nitrogen content under low-level warming and high-level warming decreased by 66% and 72% (P < 0.05), respectively, while only high-level warming significantly stimulated soil available phosphorus content by 36% (P < 0.05). (2) Compared with control, warming significantly reduced soil bacterial α diversity and phylogenetic diversity, with notable differences in bacterial community structure (P < 0.05). But soil fungi community did not show any changes in these indicators. (3) In the soil bacterial community, functional categories such as carbohydrate metabolism and global overview map were significantly improved due to warming, while the abundance of three trophic types (i.e. symbiotroph, pathtroph and saprotroph) of soil fungi did not change under warming. (4) Soil bacterial functional potentials were mainly and positively correlated with soil total nitrogen and available phosphorus, while fungal functional potentials were positively associated with fungal Shannon diversity index.

    Conclusion 

    In conclusion, warming significantly reduces soil bacterial α diversity and phylogenetic diversity, alters its β diversity. Warming promotes the expression of functional potentials such as carbohydrate metabolism in the bacterial community by regulating soil available phosphorous. In contrast, warming does not influence soil fungal diversity, community structure, and functional potentials. Our findings highlight the differential temperature sensitivities of soil bacterial and fungal communities, which may affect ecosystem functions differently.

  • 土壤微生物是生态系统中数量最多、多样性最丰富的生物群落之一,它们在调节植物群落动态、生物地球化学循环和生态系统对环境变化的响应方面发挥着重要作用[1]。土壤微生物群落中,物种数量及其特征是调节生态系统功能及稳定性的重要因素。除物种丰富度外,土壤微生物群落多样性以及功能潜力同样对生态系统功能具有不可忽视的影响[2]。在全球生物多样性持续下降的背景下[3],微生物多样性如何影响生态系统功能已成为生态学的热门话题之一。尽管已有研究结果表明生态系统功能可能与微生物多样性呈正相关,但是这一结论并不具有普适性[47]。随着高通量技术的快速发展,土壤微生物的谱系多样性也受到越来越多的关注。谱系多样性在反映物种丰富度的同时,也将物种的进化历史纳入了考量[7]。此外,由于物种亲缘关系的远近直接关联其功能性状是否一致,谱系多样性已被证明在预测生态系统功能方面具有一定价值[8]。Goberna等[9]研究表明,在深层谱系中,部分资源利用高效率物种表现出功能保守性与排他性,从而降低谱系多样性。这些高效率物种(如变形菌门Proteobacteria)在土壤有机碳含量较高的环境中,展现出更快的有机质分解速率和更高的养分吸收效率,在谱系多样性较低的情况下也能显著提升生态系统功能[9]。相反,在浅层谱系中的部分微生物物种可能展现出更强的环境适应性,而更高的谱系多样性则代表了互补且多样的功能,从而可能促进生态系统功能[9]。由此可知,土壤微生物物种多样性以及谱系多样性与生态系统功能的复杂联系仍缺乏深入认识。

    根据IPCC[10] 2023年的报告,自工业革命以来,全球气温随着大气二氧化碳浓度增加稳步上升。土壤微生物与其环境紧密相连,极易受到非生物因素(如土壤温度[1113]、湿度[1316]、pH[17])和生物因素(如植物群落[1820]、根系生物量[2122]、土壤动物[23])的影响。阐明土壤细菌和真菌群落如何响应气候变暖,对于预测气候变化对陆地生态系统的影响至关重要。研究表明,气候变暖对土壤细菌和真菌群落的影响存在差异,尤其是特定的微生物类群对气候变暖的响应各不相同[23]。例如,长期增温并未显著影响细菌的α多样性,但显著改变了细菌群落结构[24],尤其是放线菌门(Actinobacteria)和α-变形菌门(α-Proteobacteria)等特定微生物类群的丰度发生了显著变化[25]。另有研究发现,增温增加了微生物代谢活动,如单位生物量的微生物呼吸增加,但对微生物群落的多样性或结构未产生显著影响[26]。此外,气候变暖对微生物群落的影响可能会受到其他环境因素的干扰(如土壤湿度[27]、土壤氮有效性[28]、土壤pH[27])。例如,气候变暖引起的土壤水分减少可能导致微生物种群数量减少,但物种丰富度、多样性和均匀性显著增加[29]。同时,变暖增加了土壤氮的可利用性,增强了氨氧化细菌的活性,从而显著改变土壤细菌群落的组成和功能潜力[30]。温度和水分的协同作用对土壤碳利用效率及微生物多样性和群落结构也有重要影响[31]。在湿润条件下,更高的微生物多样性群落会显著促进土壤碳利用效率;而在干燥条件下,因水分不足会限制微生物代谢活动及增加其生存成本,微生物多样性与土壤碳利用效率的正向相关性则会被削弱[31]。综上所述,气候变暖通过多种途径影响土壤微生物的多样性和群落结构,这些变化受多种因素调控,进而可能改变生态系统功能(如养分循环和土壤有机质分解)。在寒冷地区,这种影响更加明显,因为这些地区土壤中储存了大量的碳,且对气候变暖更为敏感[32]

    作为地球上的“第三极”,青藏高原约有一半面积被高寒草甸所覆盖[33]。由于生态环境脆弱,该地区的气候变暖趋势远高于全球平均水平。过去10年中,青藏高原的变暖速度是全球平均水平的2倍[34]。研究表明,青藏高原土壤微生物群落结构对增温的响应因海拔高度的不同而存在差异,这主要归因于不同海拔地区植被覆盖度、土壤温度和pH条件的变化[35]。随着气温升高,青藏高原地区土壤微生物物种多样性的增加减缓了深层土壤有机碳分解对变暖的响应[36]。然而,也有研究结果表明,土壤真菌群落并未因增温而发生显著改变[37]。尽管如此,以往研究主要聚焦于增温对土壤微生物物种多样性的影响,而关于谱系多样性如何响应气候变暖的研究还相对较少,且以往研究主要探讨增温和不增温处理对土壤微生物的影响,而不同增温幅度对土壤微生物的具体影响尚不清楚。因此,青藏高原高寒草甸土壤细菌与真菌的物种多样性和谱系多样性及其各自的功能潜力如何响应气候变暖,以及这些变化的调控机制,值得进一步探究。基于此,本文依托青藏高原高寒草甸长期野外增温控制试验,旨在回答以下两个科学问题:(1)土壤细菌与真菌多样性如何响应不同幅度的增温,其响应存在何种差异?(2)土壤细菌与真菌的功能潜力如何响应气候变暖,主要受哪些因素调控?

    本研究在四川若尔盖高寒湿地生态系统国家野外科学观测研究站(32°49′48″N,102°34′48″E,海拔3 490 m)开展。该研究站位于青藏高原东缘,属大陆季风型气候,降水量较为充沛,全年80%的降水量集中在5—9月,年平均降水量为749 mm,年平均气温为1.4 ℃。土壤类型以亚高山草甸土和沼泽土为主,土层厚度为0.3 ~ 0.8 m,表层土壤密度为 0.89 g/cm3。试验区属于高寒草甸生态系统,植被覆盖度(绝对盖度)为80% ~ 100%。主要优势物种有禾本科的垂穗披碱草(Elymus nutans)、甘青剪股颖(Agrostis hugoniana)和草地早熟禾(Poa pratensis)等,莎草科的四川嵩草(Kobresia setchwanensis)、华扁穗草(Blysmus sinocompressus)等,豆科的野豌豆(Vicia sepium)和甘肃棘豆(Oxytropis kansuensis)等,以及杂类草的鹅绒委陵菜(Potentilla anserina)、草玉梅(Anemone rivularis)和灰苞蒿(Artemisia roxburghiana)等。

    本试验采用随机区组设计,共设置对照(CK)、增低温(LW,+1.5 ℃)和增高温(HW,+2.5 ℃)3种处理。每个处理设5个重复,共15个小区,小区面积为2 m × 3 m,相邻小区间隔为3 m。于2014年6月开始实施增温处理,通过红外加热实现增温。将红外辐射器(MSR-2420,Kalglo Electronics Inc.,Bethlehem,Pennsylvania,USA)悬挂于增温样地(LW和HW)中央,辐射器尺寸为165 cm × 15 cm,悬挂高度为1.5 m。对照样地(CK)中央相同位置悬挂同尺寸的增温辐射器假体(无功率输出),以模拟红外辐射器可能产生的遮阴效应。LW和HW处理的红外辐射器输出功率分别设置为1 000 和2 000 W。

    土壤样品采集于2020年8月。在每个2 m × 3 m的样方内利用内径为5 cm的土钻,采用五点取样法,钻取5份深度为10 cm的土芯并去除杂质后混匀,过2 mm筛,装入密封袋中于冰上运至实验室。所采集的土壤样品分为两份保存,一份储存于4 ℃冰箱,用作土壤理化性质等指标测定;一份储存于−80 ℃超低温冰箱用作土壤微生物分析。储存于4 ℃冰箱的土壤样品一部分用于测定土壤铵态氮(NH+4-N)、硝态氮(NO3-N),剩余样品自然风干后测定土壤pH、总氮、土壤有机碳、土壤有效磷。利用全自动连续流动分析仪(AA3,SEAL Analytical GmbH,Germany)测定NH+4-NNO3-N含量。土壤pH用pH酸度计(Mettler-Toledo FE 20,Switzerland)测定,土壤悬浮液的土水比为1∶5。风干的土壤样品酸洗去除无机碳后采用元素分析仪(Elementar vario EL cube,Germany)测定总氮和土壤有机碳;根据碳酸氢钠浸提–钼锑抗比色法测量土壤有效磷含量。

    将储存于−80 ℃超低温冰箱的土壤样品,各取0.5 g,使用ALFA-SEQ Magnetic Soil DNA Kit (Findrop,China) 进行DNA提取,提取方法参照试剂盒说明书。DNA抽提后,使用The Thermo ScientificTM NanoDropTM OneC 超微量分光光度计 (Thermo Fisher Scientific,USA) 检测DNA的纯度和浓度。细菌16S rRNA基因的V3~V4区域扩增采用引物对515F(5′-GTGCCAGCMGCCGCGGTAA-3′)和806R(5′-GGACTACHVGGGTWTCTAAT-3′);真菌ITS rRNA基因扩增采用引物对ITS3-F(5′-GCATCGATGAAGAACGCAGC-3′) 和 ITS4-R(5′-TCCTCCGCTTATTGATATGC-3′)[38]。PCR反应在BioRad S1000 (Bio-Rad Laboratory,CA) 仪器上进行,每个样本设置3个重复,反应条件为:94 ℃预变性5 min;94 ℃变性30 s、52 ℃退火30 s、72 ℃延伸30 s,共30个循环;最后72 ℃延伸5 min。PCR产物通过1%琼脂糖凝胶电泳检测,确认主带长度符合要求的样品用于后续试验。最终,将符合要求的样品送至广东美格基因科技有限公司,利用Illumina NovaSeq 6000测序系统进行高通量测序。

    将测序所得原始双端序列通过fastp(V0.14.1)进行接头处理、质量裁剪和过滤。随后,采用usearch(V10.0.240)软件进行序列拼接和引物切除,并采用UPARSE[39]算法将序列聚类为相似性 ≥ 97 %的可操作性分类单元(operational taxonomic unit,OTU)。将所得OTU与SILVA(16S rRNA)数据库及Unite(ITS rRNA)数据库比对,获得分类物种注释信息。根据分类结果,筛选出仅含细菌和真菌门类的OTU,生成OTU丰度表。基于细菌与真菌的OTU表格及其代表性序列,分别利用Tax4fun2[40](细菌)和FUNGuild[41](真菌)进行功能预测。细菌功能注释通过比对KEGG数据库实现,并根据KEGG数据库的三级分类进行统计分析;真菌功能注释则通过FUNGuild工具,将OTU分配到相应的生态功能类群,并统计不同处理条件下各功能类群的丰度。

    本文相关数据均采用R 4.3.2进行统计分析。采用phyloseq包[42]计算细菌和真菌的Shannon多样性、物种丰富度及谱系多样性;利用单因素方差(one-way ANOVA)分析检验不同增温处理对环境因子、细菌与真菌物种Shannon多样性、物种丰富度以及谱系多样性的显著性影响,并采用最小显著差异法(least significant difference,LSD)进行多重比较,显著性基于0.05水平。使用vegan包[43]进行Mantel和PERMONOVA检验,基于Bray-Curtis距离的非度量多维尺度分析(non-metric multidimensional scaling,NMDS)检验增低温和增高温分别对细菌和真菌群落结构的影响;使用pheatmap包检验增温对细菌和真菌功能丰度的影响。最后通过Mantel相关性分析,探究土壤微生物功能潜力、微生物多样性与环境因子的相关性,以分析土壤微生物功能潜力和多样性的影响因素。

    增温显著改变了土壤的理化性质,包括温度、湿度和养分含量(图1)。单因素方差分析显示,增温显著提高了土壤温度(P < 0.05)。增低温和增高温处理使表层土壤(0 ~ 10 cm)温度分别增加了约1.4 和2.4 ℃。与对照相比,增温使土壤湿度显著下降了11%(LW)和17%(HW)(P < 0.05)。增温对土壤pH、总氮和铵态氮无显著影响(P > 0.05),但土壤硝态氮含量显著降低了66%(LW)和72%(HW)(P < 0.05)。增低温对土壤有机碳及有效磷含量无显著影响,但增高温使得土壤有机碳含量显著增加了14%(P < 0.05),土壤有效磷含量显著增加了36%(P < 0.05)。

    图  1  增温对土壤理化性质的影响
    CK.对照;LW.增低温(+1.5 ℃);HW.增高温(+2.5 ℃)。不同小写字母表示不同增温处理间差异显著 (P < 0.05)。下同。
    Figure  1.  Effects of warming on physical and chemical properties of soil

    增温显著改变了土壤细菌的多样性(P < 0.05);但对土壤真菌的多样性无显著影响,且增低温与增高温之间差异也不显著(图2)。与对照相比,增低温处理显著降低了土壤细菌的Shannon多样性指数和物种丰富度(P < 0.05),增高温处理则显著降低了细菌的物种丰富度和谱系多样性(P < 0.05)。增温显著改变了细菌β多样性(F = 1.40,P = 0.02,图3),但对真菌β多样性无显著影响(P > 0.05),不过对照与增高温处理之间真菌群落差异性较为明显。

    图  2  增温对土壤细菌与真菌Shannon多样性、丰富度以及谱系多样性的影响
    *表示增温处理间差异显著(P < 0.05)。
    Figure  2.  Effects of warming on Shannon diversity, richness and phylogenetic diversity of soil bacterial and fungi
    图  3  增温对土壤细菌与真菌β多样性的影响
    Figure  3.  Effects of warming on β diversity of soil bacterial and fungi

    增高温处理下,土壤细菌功能明显提升,主要集中在碳水化合物代谢以及全局概览图(global and overview maps)等功能分类中。其中,碳水化合物代谢中的淀粉和蔗糖代谢、磷酸戊糖途径、果糖和甘露糖代谢、糖酵解/糖异生、戊糖和葡萄糖醛酸脂的相互转化和全局概览图中的抗生素的生物合成、脂肪酸代谢和不同环境中的微生物代谢在增温处理下均得到明显促进(图4a)。而细胞过程功能分类中的群体感应以及生物膜形成等丰度在增温处理下表现出下降趋势。增温对辅因子和维生素代谢功能分类的影响并不一致。其中叶酸生物合成、硫辛酸代谢、泛酸和CoA生物合成等功能丰度呈现下降趋势;而视黄醇代谢、生物素代谢以及烟酸酯和烟酰胺代谢等功能丰度则表现出一定的增加趋势。

    图  4  增温对土壤细菌(a)和真菌(b)功能潜力的影响
    Figure  4.  Effects of warming on functional potentials of soil bacteria (a) and fungi (b)

    根据FUNGuild对ITS rRNA基因序列功能的注释结果显示,增温处理下所富集的土壤真菌功能变化不一,3种营养型的真菌功能丰度随增温处理表现出不一致的响应(图4b)。木质腐生真菌、叶子腐生真菌、植物寄生真菌、动物寄生真菌、外生菌根真菌、地衣共生真菌随增温处理其丰度明显上升;而丛枝菌根真菌、真菌寄生菌、内生真菌、动物病原菌、土壤腐生真菌以及地衣寄生菌随增温处理其功能丰度呈现一定的下降趋势。

    Mantel分析结果(图5)显示,细菌功能潜力仅与总氮呈显著相关性(P < 0.05)。环境因子对细菌α多样性和谱系多样性没有显著影响。细菌β多样性分别与土壤有效磷(r = −0.74,P < 0.05)、土壤温度(r = −0.73,P < 0.05)呈显著负相关,而与土壤湿度(r = 0.83,P < 0.01)呈显著正相关。真菌功能潜力仅与其谱系多样性呈显著相关性(P < 0.05)。环境因子对真菌α多样性和谱系多样性没有显著影响。真菌β多样性与土壤有效磷(r = −0.78,P < 0.05)和土壤温度(r = −0.71,P < 0.05)呈显著负相关,与土壤湿度(r = 0.73,P < 0.05)呈显著正相关。

    图  5  土壤细菌与真菌功能潜力与环境因子、微生物多样性的关系
    *、**、***分别表示在P < 0.05、P < 0.01、P < 0.001水平上显著相关。
    Figure  5.  Relationship between functional potential of soil bacteria and fungi, environmental factors, as well as microbial diversity

    本研究结果表明,增温显著降低了土壤湿度、土壤硝态氮含量,但增加了土壤有效磷及有机碳含量,在前人研究[4447]中也得到相似结果。也有部分研究发现,增温增强了土壤反硝化菌群的活性,从而增加了土壤硝态氮含量[4850],但本试验平台前人研究结果[50]表明,尤其是植物地下生物量在增温条件下显著增加,这可能会加速植物对土壤有效氮的吸收,导致土壤可利用性氮含量的降低[5152]。土壤有机碳增加主要来自于地下碳输入增加[53]。土壤有效磷含量的增加可能与植物通过羧酸盐释放策略进而增加对土壤无机磷的活化与同化有关[46,54]

    与前人研究结果一致,温度升高显著降低了土壤细菌α多样性,改变了细菌β多样性,但对真菌的分类和谱系多样性并无显著影响[55]。这表明细菌群落更容易受到外界环境的影响,且和真菌在生态系统中的生态特征和生活策略有所不同[29,56],即细菌对环境干扰的抵抗力与真菌存在较大差异[57]。由于二者在土壤生态系统中扮演不同的角色,它们对环境变化的响应方式也各不相同。真菌在土壤中主要承担分解复杂有机质的角色,其更不容易受短期环境变化的影响,进而表现出更强的抵抗力;而细菌则更倾向于分解和利用可溶性有机质[4]。此外,在细菌群落中,不同门类对温度的适应性并不一致[58],例如:厚壁菌门(Firmicutes)是少数能够耐高温的细菌门类之一。本研究中细菌多样性的降低可能归因于不同门类细菌对温度的适应性不同,即增温对适应低温的细菌丰度产生了负面作用,但温度升高可能促进了耐高温细菌的生长与活性。同时,本文细菌群落的β多样性与土壤有效磷含量呈现显著负相关,其原因可能是有效磷含量增加导致特定细菌群体增多,而其他细菌群体减少,从而使得对照与增温处理下细菌群落产生一定差异[59]。与细菌结果类似,真菌β多样性也与土壤湿度呈正相关,与土壤有效磷呈负相关。本文中尽管增温未显著改变土壤真菌多样性和群落结构,但6年增温导致增高温处理与对照处理的真菌群落结构产生明显差异,表明在未来更长时间尺度的气候变暖背景下,真菌群落结构及多样性也可能出现显著变化。

    细菌多样性变化往往反映其功能潜力的差异。增温主要促进了细菌在碳水化合物代谢方面的功能,如淀粉、蔗糖代谢等,这与前人研究结果[60]一致。温度升高可能加速土壤中细菌本身的代谢速率,推动碳水化合物的降解和利用,从而促进细菌代谢活动[61];同时,增温也可能提高土壤酶的活性,这些酶参与碳水化合物的分解,为细菌提供更多碳源[14,60],本文中SOC仅在增高温处理下显著增加。相较于微生物群落变化,土壤有机碳周转较慢,使得短期内检测到有机碳的变化存在很大挑战。未来可将土壤有机碳库按照不同碳的来源(植物源碳和微生物来源碳)、稳定性和功能差异进行分组,这有助于进一步从机理上解释增温引起的微生物多样性变化对土壤碳降解功能和土壤碳库的影响。与此同时,亟需测定与土壤碳循环过程相关的土壤酶活性或者温室气体通量等生态系统功能指标,从而更全面地量化土壤微生物在调控生态系统功能方面的作用。

    此外,增温也抑制了细胞过程中部分细菌生物膜的形成。土壤细菌的常见生存策略多为选择形成生物膜来适应进化上的选择压力,同时生物膜也是细菌发挥功能的核心[62]。根据本文中Mantel分析结果可知,细菌功能潜力与土壤总氮存在较强联系,且土壤总氮与有效磷含量呈显著正相关。可能的原因是,在酸性土壤中,土壤养分首要驱动了这些细菌的功能和组成[63]。此外,参与土壤有机磷矿化的光合细菌丰度和群落组成与SOC之间也存在密切联系[64]。而土壤中细菌生物膜通过改变土壤微环境,进而影响土壤中不同形态磷的转化和磷的有效性[6365]。其他研究亦表明,细菌分泌的胞外聚合物,即形成微生物生物膜的基质,可以影响细菌对磷的吸附和释放过程,从而调节土壤中的磷循环[6668]。这一调节过程可能导致土壤中有效磷含量增加,对植物的生长和发育产生积极影响[6870]

    本文中增温并未显著改变真菌的多样性和功能潜力,且真菌功能潜力仅与真菌谱系多样性存在密切联系。这从侧面佐证了土壤真菌群落对短期环境变化的响应更为缓慢,进而相较于细菌群落表现出对外界环境更强的抵抗力。此外,本文中的环境因子均未显著影响真菌的谱系多样性,仅土壤铵态氮含量与其存在弱相关,这与Schimel 等[71]的研究结果一致。作为关键的氮源之一,土壤铵态氮含量在塑造土壤真菌群落的结构和多样性方面扮演着至关重要的作用。根据Li等[72]的研究结果,铵态氮含量的变化不仅可以改变特定真菌群落的丰度,进而影响整个真菌群落的功能与稳定性,还可能改变真菌在有机质分解、营养物质循环以及维持植物根系健康等方面的功能,最终对整个生态系统功能产生重要影响。

    综上,本研究揭示了增温对青藏高原高寒草甸生态系统土壤细菌与真菌多样性及其功能潜力的影响,并初步探索了细菌与真菌多样性和功能潜力对增温响应的潜在机制。结果表明,增温显著降低了土壤细菌的α多样性以及谱系多样性,改变了其β多样性。增温通过调控土壤有效磷含量进而促进细菌群落在碳水化合物代谢等功能潜力的表达;与增低温相比,增高温处理对土壤细菌群落的影响更大。此外,增温未显著改变土壤真菌的多样性和功能潜力。研究结果表明了土壤细菌与真菌群落对气候变暖响应的敏感性存在差异,这对于理解未来气候变化背景下不同类群土壤微生物对生态系统功能的调控作用具有重要的指示意义。

  • 图  1   增温对土壤理化性质的影响

    CK.对照;LW.增低温(+1.5 ℃);HW.增高温(+2.5 ℃)。不同小写字母表示不同增温处理间差异显著 (P < 0.05)。下同。

    Figure  1.   Effects of warming on physical and chemical properties of soil

    图  2   增温对土壤细菌与真菌Shannon多样性、丰富度以及谱系多样性的影响

    *表示增温处理间差异显著(P < 0.05)。

    Figure  2.   Effects of warming on Shannon diversity, richness and phylogenetic diversity of soil bacterial and fungi

    图  3   增温对土壤细菌与真菌β多样性的影响

    Figure  3.   Effects of warming on β diversity of soil bacterial and fungi

    图  4   增温对土壤细菌(a)和真菌(b)功能潜力的影响

    Figure  4.   Effects of warming on functional potentials of soil bacteria (a) and fungi (b)

    图  5   土壤细菌与真菌功能潜力与环境因子、微生物多样性的关系

    *、**、***分别表示在P < 0.05、P < 0.01、P < 0.001水平上显著相关。

    Figure  5.   Relationship between functional potential of soil bacteria and fungi, environmental factors, as well as microbial diversity

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出版历程
  • 收稿日期:  2024-02-29
  • 修回日期:  2024-05-27
  • 录用日期:  2024-06-10
  • 网络出版日期:  2024-06-11
  • 刊出日期:  2025-01-24

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