泰山4种优势造林树种细根分解对细菌群落结构的影响

为了理解细菌群落结构和多样性对森林生态系统细根凋落物分解的影响, 该研究以泰山4种主要优势造林树种刺槐(Robinia pseudoacacia)、麻栎(Quercus acutissima)、油松(Pinus tabulaeformis)和赤松(Pinus densiflora)为研究对象, 采用凋落物分解袋法及Illumina Miseq测序平台对细菌16S rDNA V4-V5区扩增产物进行双端测序, 分析了4种树种细根分解对细菌群落结构及多样性的影响。结果表明: (1) 4种植物细根分解速率差异显著, 阔叶树种分解速率显著高于针叶树种, 表现为刺槐>麻栎>油松>赤松。(2) 4个树种细菌序列操作分类单元(OTU)、观测到的物种数、Ace指数和系统发育多样性之间差异显著, 且阔叶树种刺槐和麻栎显著低于针叶树种赤松和油松。4种细根分解的细菌群落结构存在极显著差异。细根初始碳(C)含量、木质素:氮(N)和C:N对细菌群落结构的影响较大。(3)细菌群落相对丰度在5%以上的优势类群是变形菌门、放线菌门、拟杆菌门、酸杆菌门, 且变形菌门、酸杆菌门在4个树种之间差异显著, 特别是阔叶树种变形菌门显著高于针叶树种。在纲水平上, α-变形菌纲、β-变形菌纲、γ-变形菌纲、不明放线菌纲、鞘脂杆菌纲为主要的优势纲, 其中α-变形菌纲、不明放线菌纲在4个树种之间差异显著。(4) Pearson相关性分析表明, 细菌优势门和纲相对丰度受到凋落物初始化学性质的影响, 特别是变形菌门和α-变形菌纲; 变形菌门和α-变形菌纲相对丰度与细根分解速率显著正相关。冗余分析结果也显示, 细根初始N、磷(P)含量和木质素含量对细菌群落结构的影响较大。研究结果有助于理解细菌群落结构和多样性对森林生态系统细根凋落物分解的影响。     

Effects of fine root decomposition on bacterial community structure of four dominated tree species in Mount Taishan,China

为了理解细菌群落结构和多样性对森林生态系统细根凋落物分解的影响, 该研究以泰山4种主要优势造林树种刺槐(Robinia pseudoacacia)、麻栎(Quercus acutissima)、油松(Pinus tabulaeformis)和赤松(Pinus densiflora)为研究对象, 采用凋落物分解袋法及Illumina Miseq测序平台对细菌16S rDNA V4-V5区扩增产物进行双端测序, 分析了4种树种细根分解对细菌群落结构及多样性的影响。结果表明: (1) 4种植物细根分解速率差异显著, 阔叶树种分解速率显著高于针叶树种, 表现为刺槐>麻栎>油松>赤松。(2) 4个树种细菌序列操作分类单元(OTU)、观测到的物种数、Ace指数和系统发育多样性之间差异显著, 且阔叶树种刺槐和麻栎显著低于针叶树种赤松和油松。4种细根分解的细菌群落结构存在极显著差异。细根初始碳(C)含量、木质素:氮(N)和C:N对细菌群落结构的影响较大。(3)细菌群落相对丰度在5%以上的优势类群是变形菌门、放线菌门、拟杆菌门、酸杆菌门, 且变形菌门、酸杆菌门在4个树种之间差异显著, 特别是阔叶树种变形菌门显著高于针叶树种。在纲水平上, α-变形菌纲、β-变形菌纲、γ-变形菌纲、不明放线菌纲、鞘脂杆菌纲为主要的优势纲, 其中α-变形菌纲、不明放线菌纲在4个树种之间差异显著。(4) Pearson相关性分析表明, 细菌优势门和纲相对丰度受到凋落物初始化学性质的影响, 特别是变形菌门和α-变形菌纲; 变形菌门和α-变形菌纲相对丰度与细根分解速率显著正相关。冗余分析结果也显示, 细根初始N、磷(P)含量和木质素含量对细菌群落结构的影响较大。研究结果有助于理解细菌群落结构和多样性对森林生态系统细根凋落物分解的影响。     

土壤微生物群落对麻栎-刺槐混交林凋落物分解的影响

以麻栎-刺槐混交林和麻栎纯林为研究对象,采用野外定点采样、室内分析与高通量测序的方法,对凋落物分解过程中土壤微生物菌群多样性特征及其对凋落物分解速率的影响进行了研究。结果表明:(1)麻栎-刺槐混交林凋落物的分解速率高于麻栎纯林。两种林分凋落物有机碳(TOC)、全氮(TN)发生释放,全磷(TP)发生积累-释放的过程。(2)两种林分土壤细菌优势类群为放线菌门(Acidobacteria)、变形菌门(Proteobacteria)、酸杆菌门(Actinobacteria)和疣微菌门(Verrucomicrobia),土壤真菌优势类群为担子菌门(Basidiomycota)、子囊菌门(Ascomycota)和被孢霉门(Moritierellomycota)。(3)凋落物分解过程中,麻栎-刺槐混交林土壤微生物菌群丰富度指数和菌群多样性指数变化范围小于麻栎纯林。(4)凋落物分解速率与土壤细菌菌群丰富度指数和菌群多样性指数呈显著正相关,与土壤真菌菌群丰富度指数呈显著正相关。土壤微生物群落对麻栎-刺槐混交林和麻栎纯林凋落物分解速率具有重要影响,研究结果为深入开展混交林土壤微生物多样性对凋落物分解的影响研究提供理论依据。     

细菌对五大连池火山森林凋落物早期分解的影响

为了解火山森林生态系统中微生物在凋落物分解和营养循环中的作用，以五大连池火山熔岩台地森林优势树种落叶松、白桦、山杨为研究对象，采用凋落物袋野外原位分解和高通量测序方法，分析细菌群落结构及多样性对凋落物分解的响应。结果表明：经过18个月的分解，3种植物叶片凋落物质量残留率为63.9%～68.1%,白桦叶片凋落物分解最快，分解前后的N含量、C∶N、N∶P存在显著差异。3种植物叶片凋落物的细菌物种数和多样性指数具有显著差异。变形菌门、放线菌门、拟杆菌门为优势菌门，根瘤菌属、鞘氨醇单胞菌属、假单胞菌属为优势菌属，且在3种凋落物间存在显著差异。分解18个月后，凋落物中优势细菌类群与火山熔岩台地土壤趋向一致，火山森林生态系统中凋落物细菌多样性和群落结构受到凋落物中P含量、C∶N和N∶P的影响。     

沙坡头地区凋落物分解及其对土壤微生物群落的影响

以腾格里沙漠东南缘沙坡头人工固沙植被区典型植物种凋落物(小画眉草、藓类、油蒿叶片)为对象,运用凋落物分解袋法和高通量测序技术,分析了3种植物凋落物分解特征及其对土壤微生物群落的影响。结果表明: 分解时间和凋落物类型均显著影响分解速率,藓类分解最慢,13个月后质量损失比仅为15.4%,油蒿叶片和小画眉草的平均分解速率分别是藓类的4.9和3.4倍。经过11个月的分解,细菌群落的优势菌门为放线菌门和变形菌门,真菌群落的优势菌门是子囊菌门;藓类分解过程中,拟杆菌门和绿弯菌门的相对丰度显著增加,担子菌门的相对丰度显著降低。凋落物分解后,细菌和真菌群落物种多样性和丰富度显著增加,细菌群落组成在凋落物间变化不显著,真菌群落变化显著。凋落物的分解速率与细菌和真菌群落多样性及丰富度均呈负线性变化。植物多糖、全磷和土壤pH、微生物生物量氮、铵态氮含量是影响微生物群落结构的主要因子。凋落物分解改变了土壤微生物群落物种组成和种间相似性,显著增加了土壤中微生物群落的多样性和丰富度,促进了土壤生境的恢复。     

黄土丘陵区刺槐人工林林龄增加土壤微环境变化对凋落物分解的影响

凋落物所处的土壤微环境是影响其分解的关键因素之一,然而在黄土高原广泛栽植的刺槐人工林中,土壤微环境随林龄增加如何改变、其对凋落物分解过程的影响趋势尚不清楚。为明确上述问题,以油松凋落物(典型的难分解凋落物)和白三叶凋落物(易分解)为对象,分别在林龄为10、20、33 a和43 a的刺槐林地土壤表面进行为期592 d的模拟分解试验,检测凋落物分解特征以及地表土壤理化生物学性质随林龄增加的变化趋势,并分析凋落物分解速率与土壤微环境指标间的关系。结果表明:(1)随林龄增加,油松凋落物的分解速率呈先小幅降低后提高的趋势,白三叶凋落物的分解速率持续提高(P<0.05);(2)总体而言,随林龄增加林地表层土壤温度呈先降后增趋势,土壤湿度、有效磷含量和pH持续降低,而速效氮含量持续提高(P<0.05);(3)林龄增加显著改变了林地土壤微生物群落结构,特别是在各分解时间点时均导致真菌属的明显演替现象。土壤中9种凋落物分解酶的总酶活性和木质纤维素酶活性均在分解第108天时随林龄增加呈先降后增趋势,而在分解第389天和第592天时持续提高(P<0.05)。(4)油松凋落物分解速率仅与土壤总酶活性、真菌群落结构和铵态氮含量呈显著正相关,白三叶凋落物分解速率则与总酶和木质纤维素酶活性、细菌和真菌群落结构、温度和铵态氮含量显著正相关,而与土壤湿度和pH显著负相关(P<0.05)。综上所述,刺槐林龄增加引起的土壤理、化和生物微环境变化总体倾向于加速凋落物的分解过程。     

模拟增温对湿地植物凋落物分解及细菌群落的影响

植物凋落物分解是湿地生态系统物质循环的重要组成部分,随着全球气候变化的逐渐加剧,气候变暖对湿地植物凋落物分解的影响已引起人们的广泛关注。本研究通过凋落物袋法对比研究了山东省南四湖湿地中芦苇和香蒲两种典型湿地植物的凋落物分解过程,利用开顶式生长室(Open-top Chamber, OTC)模拟了大气增温(2.0±0.5)℃—(4.0±0.5)℃对凋落物分解特征和细菌群落的影响。结果显示,增温显著加速了两种植物凋落物的分解速率,而木质素/氮(Lignin/N)、纤维素/氮(Cellulose/N)是影响凋落物分解速率的重要因子,与分解速率呈显著负相关。增温显著增加了细菌群落的丰度和多样性,碳是厚壁菌门(Firmicutes)等细菌丰度变化的驱动因子,而木质素、木质素/氮是拟杆菌门(Bacteroidota)等细菌丰度变化的驱动因子。细菌群落共现网络显示,在增温条件下,凋落物分解的细菌群落网络主要由共生关系组成。气候变暖提高了细菌之间的相互关系和互惠程度,加快了植物凋落物的分解进程,进而影响了湿地生态系统的碳收支平衡。     

贺兰山不同林分凋落物微生物群落特征与影响因素

贺兰山是我国重要生态屏障,贺兰山生态森林生态系统保护受到极大关注,森林凋落物及土壤微生物对全球气候变化研究具有重要意义。目前,贺兰山不同林分的凋落物分解过程中微生物群落结构特征差异、不同凋落物化学组成对微生物群落结构的影响尚不清楚。以贺兰山具有代表性的3种林分（油松林、青海云杉林以及油松-山杨混交林）凋落物为研究对象,开展凋落物化学组成、微生物群落组成及多样性特征研究,揭示不同林分凋落物的优势微生物群落特征和影响因子。结果表明,3种林分凋落物的细菌和真菌在多个多样性指数之间差异性均不显著,但是在多样性指数中真菌PD whole tree指数显著大于细菌,真菌Shannon指数与Ghao1指数却显著小于细菌。在门水平上不同林分凋落物的微生物优势菌类无显著差异,但在属水平上差异显著,而且细菌差异小于真菌,在各个分类水平上,凋落物细菌和真菌群落组成均表现为油松-山杨混交林＜青海云杉林＜青海云杉林,凋落物微生物多样性在青海云杉林中最为丰富。细菌不同节点间连接线负相关数量略大于正相关,真菌则相反。油松林凋落物与其它林分凋落物相比,微生物群落之间联系更加紧密。油松林凋落物OC含量最大、青海云杉林凋落物的TK含量最大、油松-山杨混交林的TN含量最大,且在3种林分中显著差异。相关性分析表明OC、TN、TP、TK是影响凋落物细菌和真菌群落组成及多样性的主要因素,冗余分析表明不同林分凋落物的微生物多样性指数受养分影响,凋落物OC、TN、TP、TK是影响微生物群落组成和多样性的重要因素,其中OC与微生物群落多样性相关性最显著,是影响凋落物细菌和真菌群落组成和多样性最主要的因子。     

四川盆地亚热带常绿阔叶林不同物候期凋落物分解与土壤动物群落结构的关系

为了解植物生长不同物候时期凋落物分解过程中土壤动物群落结构动态及其与凋落物分解的关系,以四川盆地亚热带常绿阔叶林典型人工林树种马尾松和柳杉,次生林树种香樟和麻栎凋落物为研究对象,采用凋落物分解袋试验研究,凋落物分解过程中土壤动物的群落特征。4种凋落物分解袋共获得土壤动物8047只,其中,柳杉(2341只)>香樟(2105只)>马尾松(2046只)>麻栎(1555只)。其中,秋末落叶期、萌动期和展叶期,马尾松凋落物袋中主要以捕食性土壤动物为优势类群,而后以菌食性土壤动物为主;香樟凋落物袋中除秋末落叶期和叶衰期以菌食性土壤动物为主要优势类群外,其他各时期均以捕食性土壤动物为主要优势类群;柳杉凋落物分解各时期均以菌食性土壤动物为主要优势类群;麻栎凋落物分解在前3个时期以菌食性为主,而后以植食性土壤动物为主要优势类群。相关分析表明,在秋末落叶期和萌动期土壤动物的个体密度主要和氮、磷含量及其格局密切相关,叶衰期主要和难分解组分木质素显著相关。除在秋末落叶期土壤动物对凋落物分解的贡献率与土壤动物的个体密度显著相关外,其余主要物候关键时期均与土壤动物的类群密度及其食性显著相关。     

黄土丘陵区不同森林类型叶片-凋落物-土壤生态化学计量特征

采用野外调查与室内分析相结合的方法,测定了黄土丘陵区主要人工林(刺槐、小叶杨和油松)和天然次生林(辽东栎、麻栎和白桦)中乔叶、凋落物以及土壤的碳(C)、氮(N)和磷(P)含量,探讨不同森林类型叶片-凋落物-土壤生态化学计量特征差异,旨在进一步了解研究区森林生态系统的养分供求现状。结果表明:1)人工林叶片和凋落物的C含量大于天然次生林,N、P含量均小于天然次生林,叶片和凋落物C∶N和C∶P值均表现为人工林大于天然次生林;2)人工林中土壤的C、N、P含量及化学计量比的显著性差异主要集中在土壤表层(0—10 cm),而天然次生林则集中在10—50 cm的土层,随着土层深度增加,二者的C、N、P含量逐渐减小;3)人工林N含量在叶片与凋落物间为显著正相关,天然次生林N含量在凋落物与土壤间为极显著正相关、C∶P值在叶片与土壤间则为显著负相关,其余各指标无显著相关性。揭示了除刺槐和辽东栎的生长受P限制外,其余各树种均受N限制,人工林凋落物的分解速率较快,且人工林土壤P有效性高于天然次生林,这些研究结果可为我国黄土丘陵区的植被恢复与重建工作提供理论依据。     

Decomposition dynamics in mixed-species leaf litter

Literature on plant leaf litter decomposition is substantial, but only in recent years have potential interactions among leaves of different species during decomposition been examined. We review emerging research on patterns of mass loss, changes in nutrient concentration, and decomposer abundance and activity when leaves of different species are decaying in mixtures. Approximately 30 papers have been published that directly examine decomposition in leaf mixtures as well as in all component species decaying alone. From these litter‐mix experiments, it is clear that decomposition patterns are not always predictable from single‐species dynamics. (Characteristics of decomposition in litter‐mixes that deviate from responses predicted from decomposition of single‐species litters alone are designated "non‐additive"; "additive" responses in mixes are predictable from component species decaying alone.) Non‐additive patterns of mass loss were observed in 67% of tested mixtures; mass loss is often (though not always) increased when litters of different species are mixed. Observed mass loss in some mixtures is as much as 65% more extensive than expected from decomposition of single‐species litter, but more often mass loss in mixtures exceeds expected decay by 20% or less. Nutrient transfer among leaves of different species is striking, with 76% of the mixtures showing non‐additive dynamics of nutrient concentrations. Non‐additive patterns in the abundance and activity of decomposers were observed in 55% and 65% of leaf mixes, respectively. We discuss some methodological details that likely contribute to conflicting results among mixed‐litter studies to date. Enough information is available to begin formulating mechanistic hypotheses to explain patterns in litter‐mix experiments. Emerging patterns in the mixed‐litter decomposition literature have implications for relationships between biodiversity and ecosystem function (in this case, the function being decomposition), and for potential mechanisms through which invasive plant species could alter carbon and nutrient dynamics in ecosystems.     

根系在凋落物层生长对凋落叶分解及酶活性的影响

根系向凋落物层生长是森林生态系统存在的普遍现象,研究根系存在对凋落物分解的影响对理解森林生态系统的养分物质循环具有重要意义.在福建三明市楠木和格氏栲林进行1年的凋落叶分解试验,设置有根处理和无根处理(对照),研究根系生长对凋落叶分解速率、养分释放和酶活性的影响.结果表明:在分解360 d后,有根处理楠木和格氏栲凋落叶干...     

Living in the litter: the influence of tree leaf litter on wetland communities

Empirical research in streams has demonstrated that terrestrial subsidies of tree leaf litter influence multiple community factors including composition, diversity and growth of individuals. However, little research has examined the importance of tree litter species on wetlands, which are ubiquitous across the landscape and serve as important habitats for a unique and diverse community of organisms. Using outdoor mesocosms, we assessed the impact of 12 litter monocultures and three litter mixtures (from both broadleaf and conifer trees) on pond communities containing gray tree frog tadpoles Hyla versicolor, periphyton, phytoplankton and zooplankton. We found that leaf litter species had substantial and differential impacts on all trophic groups in the community including effects on algal abundance, zooplankton density and amphibian growth. In many instances, patterns of responses were specific to individual litter species yet some responses, including both pH values and periphyton biomass, were generalizable to broad taxonomic groups. In addition, while most responses of litter mixtures were additive, we found evidence for antagonistic effects of litter mixing among responses of periphyton and amphibian body mass. Our results highlight the potential impact of human and naturally driven changes in forest composition on wetland communities through associated changes in leaf litter.     

Interacting effects of leaf litter species and macrofauna on decomposition in different litter environments

The leaf litter environment (single species versus mixed species), and interactions between litter diversity and macrofauna are thought to be important in influencing decomposition rates. However, the role of soil macrofauna in the breakdown of different species of leaf litter is poorly understood. In this study we examine the multiple biotic controls of decomposition – litter quality, soil macrofauna and litter environment and their interactions. The influence of soil macrofauna and litter environment on the decomposition of six deciduous tree species (Fraxinus excelsior L., Acer pseudoplatanus L., Acer campestre L., Corylus avellana L., Quercus robur L., Fagus sylvatica L.) was investigated in a temperate forest, Wytham Woods, Southern England. We used litterbags that selectively excluded macrofauna to assess the relative importance of macrofauna versus microbial, micro and mesofauna decomposition, and placed single species bags in either conspecific single species or mixed species litter environments. The study was designed to separate plant species composition effects on litter decomposition rates, allowing us to evaluate whether mixed species litter environments affect decomposition rates compared to single species litter environments, and if so whether the effects vary among litter species, over time, and with regard to the presence of soil macrofauna. All species had faster rates of decomposition when macrofauna were present, with 22–41% of the total mass loss attributed to macrofauna. Macrofauna were most important for easily decomposable species as soon as the leaves were placed on the ground, but were most important for recalcitrant species after nine months in the field. The mass loss rates did not differ between mixed and single species litter environments, indicating that observed differences between single species and mixed species litterbags in previous field studies are due to the direct contact of neighbouring species inside the litterbag rather than the litter environment in which they are placed.     

Cellulase activity on decomposing leaf litter in microcosms

In this paper, we describe cellulase and cellobiose dehydrogenase (CBDH) dynamics in relation to incubation time, mass loss and chemical composition of decomposing deciduous leaf litter. Cellulose disappearance from litter coincided with periods of maximum cellulase activity. CBDH activity peaked later in decomposition after cellulase activity had declined. Enzyme activity patterns differed among litter types when expressed on the basis of decomposition time or cumulative mass loss. The patterns converged when expressed on the basis of chemical composition as indexed by the fraction of cellulose in the lignocellulose complex. We present a three-stage model of decomposition based on temporal changes in cellulase activities and coincident changes in litter chemical composition.     

科尔沁沙地植物成熟叶片性状与叶凋落物分解的关系

采用室内培养的方法,对科尔沁沙质草地20个主要植物种(10个单子叶植物种和10个双子叶植物种)叶凋落物的CO2释放量和释放速率进行比较,同时测定了20种植物成熟叶片的热值、镁浓度、磷浓度、氮浓度、钾浓度、碳浓度、碳氮比、氮磷比、比叶面积、干物质含量以及叶面积等11项叶片性状,分析20种植物叶凋落物的CO2释放量和释放速率与11项叶片性状的相关关系.结果表明, 20种植物的叶片性状在物种间变异范围很大,大多数指标的最大值和最小值的差异在3倍以上,而个别指标如叶镁浓度差异更大,接近9倍之多.由于本项研究中的20种植物均来自于同一样地,因此认为20种植物的自身性状和遗传特性决定了其叶片性状的变异.20种植物叶凋落物培养28d的CO2释放量平均值为(4121±1713)μg kg-1,释放量最大的是尖头叶藜(8767±177)μg kg-1干土,释放量最小的是马唐(1669±47)μg kg-1,二者相差5倍以上.但20种植物叶凋落物CO2释放速率表现相同的变化趋势,培养初期凋落物分解迅速,后期分解相对缓慢.比较分析发现,双子叶植物和单子叶植物叶凋落物CO2释放量、CO2释放速率,以及成熟叶片的叶氮浓度、叶碳浓度、叶C/N和叶干物质含量之间差异显著.相关分析揭示,20种植物成熟叶片叶氮浓度、叶碳浓度、叶C/N和叶干物质含量与叶凋落物分解过程中的CO2释放量和释放速率之间呈显著的相关关系,说明可以利用成熟叶片的N浓度、C浓度、C/N以及干物质含量间接的预测叶凋落物的分解速率.     

Effects of flooding on leaf litter decomposition in microcosms

Summary The effects of hydroperiod on decomposition rates of senescent Acer rubrum leaves were tested in microcosms in a controlled laboratory environment. Microcosm treatments included continuously flooded, continuously unflooded, and fluctuating hydroperiods. All flooding treatments promoted decomposition but variations in hydroperiod had no significant effects. A leaching experiment indicated the higher decay rates under flooded conditions were primarily due to high leaching losses from soaking. Unlike nutrient dynamics in the field, where net accumulation occurs, nitrogen and phosphorus in the litter in the microcosms exhibited net losses. The major external inputs which provide a source of nitrogen and phosphorus for immobilization in the field were lacking in the microcosms. Calcium, magnesium, and potassium exhibited net losses except for calcium in the unflooded microcosms. The microcosm results demonstrated the importance of external inputs to litter nutrient relations.     

Decomposition of deciduous leaf litter in a woodland stream

Microorganisms associated with decomposing deciduous leaf litter in a woodland stream were examined by scanning electron microscopy. The use of a critical point drying method allowed the preservation of a wide variety of microorganisms as well as the decomposing litter with a minimum of distortion. The micrographs provide evidence that the aquatic hyphomycetes are the major fungal flora present during decomposition. Two distinct groups of these fungi were found during the seasonal cycle with one group occurring only in the summer while the other occurred throughout the rest of the year. The presence of all developmental stages of these organisms in the environment is considered further evidence of their active role in the decomposition of litter.     

Decomposition of deciduous leaf litter in a woodland stream

Microorganisms associated with decomposing deciduous leaf litter in a woodland stream were examined by scanning electron microscopy. The use of a critical point drying method allowed the preservation of a wide variety of microorganisms as well as the decomposing litter with a minimum of distortion. The micrographs provide evidence that the aquatic hyphomycetes are the major fungal flora present during decomposition. Two distinct groups of these fungi were found during the seasonal cycle with one group occurring only in the summer while the other occurred throughout the rest of the year. The presence of all developmental stages of these organisms in the environment is considered further evidence of their active role in the decomposition of litter.