Changes in the soil microbial community structure with latitude in eastern China, based on phospholipid fatty acid analysis

Phospholipid fatty acid (PLFA) profiles were measured in soils from 14 sites in eastern China representing typical geographic zones of varying latitude from north (47.4°N) to south (21.4°N). Amounts of soil microbial biomass, measured as total amounts of PLFAs, showed no regular trend with latitude, but were positively correlated with soil organic carbon content, the concentration of humic acid and amorphous iron oxide. Soil microbial community structure showed some biogeographical distribution trends and was separated into three groups in a cluster analysis and principal coordinate analysis of log transformed PLFA concentrations (mol%). Soils in the first group came from northern China with medium mean annual temperature (1.2–15.7 °C) and rainfall (550–1021 mm). Soils in the second group originated from southern China with a relatively higher mean annual temperature (15.7–21.2 °C) and rainfall (1021–1690 mm). Soils clustered in the third group originated from the most southerly region. The northern soils contained relatively more bacteria and Gram-negative PLFAs, while the southern soils had more fungi and pressure indexed PLFAs. These differences in soil microbial community structure were largely explained by soil pH, while other site and soil characteristics were less important.     

PLFA方法研究连作对加工番茄根际土壤微生物群落结构的影响

通过在石河子大学农学院试验站开展加工番茄连作定点微区试验,采用氯仿熏蒸和磷脂脂肪酸(PLFA)法相结合,研究了不同连作处理(种植1 a、连作3 a、5 a和7 a)对新疆加工番茄花果期和成熟期根际土壤微生物群落结构及土壤微生物量的影响。结果表明,连作导致土壤微生物量碳(SMBC)、微生物量氮(SMBN)和微生物熵(q MB)下降,SMBC/SMBN升高,而微生物量磷(SMBP)随连作年限和生育期的变化而不同。连作显著增加了真菌PLFAs含量,降低了细菌PLFAs含量、土壤PLFAs总量及细菌/真菌PLFAs的比值,而放线菌PLFAs含量变化无规律。连作7 a时,成熟期的细菌PLFAs含量、土壤PLFAs总量较对照分别减少62.9%、50.3%(P0.05),而真菌PLFAs含量较对照升高60.2%(P0.05)。从多样性指数分析看,Shannon-Wiener指数、Simpson指数、Brillouin指数和Pielou指数均随连作年限的延长呈先升后降的变化,其中连作3 a时各项指数最大,连作7 a时最小,表明在本试验年限范围内,连作使得微生物群落多样性与均匀程度皆出现了一定程度的降低。相关性分析表明,土壤微生物各类群PLFAs量、微生物量及土壤肥力之间存在相关性,说明土壤微生物量与土壤肥沃程度相关,可作为评价土壤肥力的生物学指标。可见,加工番茄连作改变了土壤微生物群落结构,降低了土壤微生物量,最终在根际土壤微生态系统和环境因子等因素的综合作用下产生连作障碍。     

Decoupling plant-growth from land-use legacies in soil microbial communities

Differences in soil microbial communities between ex-arable and undisturbed soils are often assumed to reflect long-term legacies of agricultural practices. Ex-arable soils, however, are commonly dominated by different plant species than undisturbed soils making it difficult to separate the importance of land-use and plant-growth legacies. In a system where non-native plants dominate ex-arable soils, we decoupled land-use (ex-arable, undisturbed) and plant-growth (native, non-native) effects on soil microbial communities using a factorial sampling design. Soils were removed from 14 sites that formed a 52-year chronosequence of agricultural abandonment. Microbial abundance and composition were measured using whole-soil phospholipid fatty acid analyses and microbial activity was measured in a subset of samples using sole-carbon-source utilization analyses. We found that both non-native-cultivated and ex-arable soils were independently associated with lower microbial abundance and diversity than native and undisturbed soils. We also found a correlation between microbial abundance and age-since-agricultural abandonment in ex-arable/non-native-cultivated soils suggesting that non-native plant effects accumulate over time. Microbial activity was consistent with microbial abundance; microbial communities in non-native-cultivated, ex-arable soils were slow to respire most carbon sources. Our data suggests that agricultural practices create soil conditions that favor non-native plant growth and non-native plants maintain these conditions. Potential mechanisms explaining how non-natives create soils with small microbial communities and how small microbial communities may benefit non-natives are discussed.     

保护性耕作对黑土微生物群落的影响

耕作方式通过影响土壤微生物群落而影响土壤生态系统过程。本研究以传统耕作玉米连作处理为对照,通过测定土壤微生物量碳及磷脂脂肪酸含量,分析了保护性耕作(包括免耕玉米连作和免耕大豆-玉米轮作)对黑土微生物群落的影响。结果表明,保护性耕作可显著增加土壤表层(0～5cm)全碳、全氮、水溶性有机碳、碱解氮和微生物量碳(P0.05),为微生物代谢提供了丰富的资源。同时,保护性耕作显著提高了土壤表层(0～5cm)总脂肪酸量、真菌和细菌生物量(P0.05),提高了土壤的真菌/细菌值,有利于农田土壤生态系统的稳定性。研究结果对于探讨保护性耕作的内在机制具有重要意义。     

土壤微生物群落结构对凋落物组成变化的响应

凋落物分解是陆地生态系统养分循环的关键过程,明确凋落物多样性如何影响土壤微生物群落构成和多度,继而潜在地改变凋落物分解的微生物学机制有助于认识生物多样性和森林生态系统功能的关系。通过小盆模拟试验,应用磷脂脂肪酸谱图的方法研究了我国南方红壤丘陵区典型物种马尾松和湿地松的凋落物分别与白栎和青冈的凋落物混合,与单一针叶凋落物分解时相比,针阔混合凋落物分解过程中土壤微生物群落结构的变化,结果显示:(1)针阔混合凋落物分解时土壤微生物群落磷脂脂肪酸(Phospholipidfatty acids,PLFA)总量低于单一针叶处理,细菌和放线菌的相对多度高于单一针叶处理,真菌则相反,群落真菌/细菌低于单一针叶处理,土壤微生物生物量的差异主要来自于真菌;(2)主成分分析表明:针阔混合凋落物分解与单一针叶凋落物分解的土壤微生物群落结构差异显著,两个时期(分解9个月和18个月)主成分一分别可以解释65.74%和89.63%的变异,第一主成分主要包括18∶2ω6,9、18∶1ω9c、17∶0和10Me18∶0等磷脂脂肪酸;(3)土壤微生物群落结构受凋落物初始C/N和木质素/N调控,土壤微生物群落细菌的相对多度与凋落物初始C/N和木质素/N显著负相关,真菌则与凋落物初始C/N和木质素/N显著正相关,群落真菌/细菌与凋落物初始C/N和木质素/N显著正相关。针阔凋落物混合分解通过改变凋落物C/N和木质素/N,提供了对分解者更为有利的微环境。     

Defoliation and fertiliser influences on the soil microbial community associated with two contrasting Lolium perenne cultivars

The influence of repeated defoliation on soil microbial community (SMC) structure and root turnover was assessed in two contrasting Lolium perenne cultivars (AberDove and S23) grown in fertilised (+F) and non-fertilised (NF) soil. BiOLOG sole carbon source utilisation profiles (SCSUPs) indicated consistently greater potential carbon utilisation in defoliated (+D) compared to non-defoliated (ND) soils regardless of cultivar and fertiliser, and was accounted for in a variety of substrate groups (sugars, carboxylic, amino and phenolic acids). Potential carbon utilisation was also stimulated in +F compared to NF soils, primarily through increased potential utilisation of carboxylic acids. PLFA indicators for the bacterial biomass did not significantly differ between cultivar, soil fertilisation, or defoliation. Defoliated swards grown in fertilised soil (+F+D) had a higher fungal:bacterial ratio and a greater bacterial stress index (cy19:0/18:1w7c), compared to that of +F ND, NF ND and NF+D, and regardless of cultivar. Overall SMC structure (canonical variate (CV) analysis of PLFAs) discriminated based on cultivar, defoliation and soil fertilisation. Primary discrimination of the SMCs could be related to differences in root density and total plant biomass, and in the case of NF soils, secondary community shifts, evident with defoliation, related to root disappearance over the growing season. Despite the strong common effects of defoliation, and to a lesser extent soil fertilisation, cultivar specific drivers of the soil microbial community were maintained, resulting in consistent, but subtle, discrimination of the SMC associated with the contrasting L. perenne cultivars.     

Does microbial habitat or community structure drive the functional stability of microbes to stresses following re-vegetation of a severely degraded soil?

Re-vegetation of eroded soil restores organic carbon concentrations and improves the physical stability of the soil, which may then extend the range of microhabitats and influence soil microbial activity and functional stability through its effects on soil bacterial community structure. The objectives of this study were (i) to evaluate the restorative effect of re-vegetation on soil physical stability, microbial activity and bacterial community structure; (ii) to examine the effects of soil physical microhabitats on bacterial community structure and diversity and on soil microbial functional stability. Soil samples were collected from an 18-year-old eroded bare soil restored with either Cinnamomum camphora (“Eroded Cc”) or Lespedeza bicolour (“Eroded Lb”). An uneroded soil planted with Pinus massoniana (“Uneroded Pm”) and an eroded bare soil served as references. The effect of microhabitats was assessed by physical destruction with a wet shaking treatment. Soil bacterial community structure and diversity were measured using a terminal restriction fragment length polymorphism (T-RFLP) approach, while soil microbiological stability (resistance and resilience) was determined by measuring short-term (28 days) decomposition rate of added barley (Hordeum vulgare) powder following copper and heat perturbations. The results demonstrated that re-vegetation treatment affected the recovery of physical and biological stability, microbial decomposition and the bacterial community structure. Although the restored soils overshot the Uneroded Pm sample in physical stability, they had lower microbial decomposition and less resilience to copper and heat perturbations than the Uneroded Pm samples. Soil physical destruction by shaking had the same effect on soil physical stability, but different effects on soil microbial functional stability. There were significant effects of vegetation treatment and perturbation type, and interactive effects among vegetation treatment, shaking and perturbation type on bacterial community structure. The destruction of aggregate structure increased resilience of the Eroded Lb sample and also altered its bacterial community structure. Both copper and heat perturbations resulted in significantly different community structure from the unperturbed controls, with a larger effect of copper than heat perturbation. Bacterial diversity (Shannon index) increased following the perturbations, with a more profound effect in the Uneroded Pm sample than in the restored soils. The interactive effects of vegetation treatment and shaking on microbial community and stability suggest that soil aggregation may contribute to the generation of bacterial community structure and mediation of biological stability via the protection afforded by soil organic carbon. Differential effects of re-vegetation treatment suggest that the long-term effects are mediated through changes in the quality and quantity of C inputs to soil.     

不同林龄马尾松人工林土壤微生物群落结构和功能多样性演变

土壤微生物在森林生态系统中起着至关重要的作用,研究人工林演变中土壤微生物群落结构特征,对评价人工林土壤质量动态变化和维持土壤微生态平衡具有重要意义。以亚热带地区马尾松人工林为研究对象,采用磷脂脂肪酸(Phospholipid fatty acid,PLFA)和BIOLOG技术研究不同林龄(13 a,25 a,38 a和58 a)对土壤微生物群落结构和代谢功能多样性的影响。结果表明:不同林龄土壤微生物类群均以细菌为主,其次为真菌和放线菌,最后为原生动物;土壤微生物总PLFAs量、真菌数量和真菌/细菌均表现为13 a最高,38 a最低;土壤细菌、革兰氏阳性细菌(G+)、革兰氏阴性细菌(G–)和放线菌数量均25a最高。层次聚类和主成分分析(PCA)结果表明,林龄对土壤微生物群落结构产生显著影响,13 a和25 a林龄分别与38 a和58 a林龄的土壤微生物群落结构差异较大。冗余分析表明,有机碳、全氮和pH是土壤微生物群落结构的主要影响因素。不同林龄土壤平均颜色变化率(AWCD)和微生物功能多样性指数(香农指数、辛普森指数和McIntosh指数)总体表现为25 a>13 a>58 ...     

Long-term plant growth legacies overwhelm short-term plant growth effects on soil microbial community structure

Plant-soil feedbacks are gaining attention for their ability to determine plant community development. Plant-soil feedback models and research assume that plant-soil interactions occur within days to weeks, yet, little is known about how quickly and to what extent plants change soil community composition. We grew a dominant native plant (Pseudoroegneria spicata) and a dominant non-native plant (Centaurea diffusa) separately in both native- and non-native-cultivated field soils to test if these species could overcome soil legacies and create new soil communities in the short-term. Soil community composition before and after plant growth was assessed in bulk and rhizosphere soils using phospholipid fatty acid analyses. Nematode abundance and mycorrhizal colonization were also measured following plant growth. Field-collected, native-cultivated soils showed greater bacterial, Gram (−), fungal, and arbuscular mycorrhizal PLFA abundance and greater PLFA diversity than field-collected, non-native-cultivated soils. Both plant species grew larger in native- than non-native-cultivated soils, but neither plant affected microbial composition in the bulk or rhizosphere soils after two months. Plants also failed to change nematode abundance or mycorrhizal colonization. Plants, therefore, appear able to create microbial legacies that affect subsequent plant growth, but contrary to common assumptions, the species in this study are likely to require years to create these legacies. Our results are consistent with other studies that demonstrate long-term legacies in soil microbial communities and suggest that the development of plant-soil feedbacks should be viewed in this longer-term context.     

氮沉降对亚热带常绿阔叶天然林不同季节土壤微生物群落结构的影响

以亚热带地区细柄阿丁枫(Altingia gracilipes)天然林为研究对象,开展2年(2010—2011年)的原位模拟大气氮沉降试验,设置3个氮水平(以氮(N)含量计算):对照(CK, 0 kg·hm~(-2)·a~(-1))、低氮(LN, 50 kg·hm~(-2)·a~(-1))、高氮(HN,100 kg·hm~(-2)·a~(-1))。采用磷脂脂肪酸(PLFA)技术探讨常绿阔叶天然林土壤微生物群落结构对氮沉降的响应。结果表明,天然林土壤微生物以细菌为优势类群,占微生物总PLFA含量的78.3%。夏季土壤微生物群落结构与其他季节发生显著差异;LN仅显著改变夏季土壤微生物群落结构;HN导致春季和冬季土壤微生物群落结构发生显著分异,且在不同季节对土壤微生物变化类群的影响不同。此外,氮沉降未使真菌与细菌比(F∶B)和革兰氏阳性菌与革兰氏阴性菌比(G+∶G-)发生显著改变,而使不同结构的环丙烷脂肪酸或异构脂肪酸等特殊脂肪酸比值发生改变,这表明短期氮沉降虽然改变了土壤微生物的群落结构,但并未影响微生物对环境变化的响应力,微生物可能通过改变特殊脂肪酸含量应对短期氮沉降,不同季节的应对策略有一定差异。因此,在探讨氮沉降对亚热带地区森林生态系统土壤微生物群落结构的影响时有必要考虑季节因素。     

Phospholipid fatty acid profiles as indicators for the microbial community structure in soils along a climatic transect in the Judean Desert

 Analyses of phospholipid fatty acids (PLFAs) were used to assess variations in soil microbial biodiversity, community structure and biomass, and consequently, the soil microbial successions in time along the climate gradient of the Judean Desert. Principal component analysis of the PLFA data revealed that the degree of time- and space-related variations in PLFA composition and microbial community structure was high among the desert habitats. Significant shifts of specific groups of fatty acids caused by climatic variations were observed. The biomass represented by the total amounts of PLFAs indicated that the greater the average amount of precipitation, the higher the biomass. The results indicate that at least three different microorganism strategies were probably followed: (1) in soils with a high biomass during the rainy period, a significant biomass decrease occurred during the dry period, mainly due to an extraordinary decrease of Gram-negative bacteria as indicated by the decrease of typical monounsaturated fatty acids and hydroxy-substituted phospholipid fatty acids in semi-arid climates; (2) in soils with low biomass content during the rainy period, a significant increase of biomass during the dry period occurred, due mainly to the increase of eukaryotes, Gram-positive, and Gram-negative bacteria characterized by polyunsaturated, branched chain and some of the monounsaturated fatty acids, respectively; and (3) relatively low and constant biomass during the entire observation period in the more arid zones of the Judean Desert. Received: 12 January 1998     

长期氮肥施用对农田黑土NLFA与PLFA特性的影响

以不施肥与休闲处理为对照,通过对土壤微生物磷脂脂肪酸（PLFA）、中性磷脂脂肪酸（NLFA）、NLFA/PLFA比值及各菌群特定PLFA比值的测定,研究不同氮肥处理条件下东北黑土微生物群落变化规律.PLFA测定结果表明,氮磷配施能促进土壤微生物生长;氮磷钾配施未表现出促进土壤微生物生长的作用;单施氮肥处理因有效磷等养分过度消耗而抑制真菌生长.不同菌群之间PLFA比值表明,真菌较细菌更能适应养分贫瘠条件,而氮肥与磷肥的施入则能促进细菌生物量增加.不同氮肥处理NLFA含量及个别NLFA/PLFA比值存在较大差异,可用来说明土壤微生物生理状态和土壤养分水平.     

Structure and function of the soil microbial community in microhabitats of a heavy metal polluted soil

 Particle-size fractionation of a heavy metal polluted soil was performed to study the influence of environmental pollution on microbial community structure, microbial biomass, microbial residues and enzyme activities in microhabitats of a Calcaric Phaeocem. In 1987, the soil was experimentally contaminated with four heavy metal loads: (1) uncontaminated controls; (2) light (300 ppm Zn, 100 ppm Cu, 50 ppm Ni, 50 ppm V and 3 ppm Cd); (3) medium; and (4) heavy pollution (two- and threefold the light load, respectively). After 10 years of exposure, the highest concentrations of microbial ninhydrin-reactive nitrogen were found in the clay (2–0.1 μm) and silt fractions (63–2 μm), and the lowest were found in the coarse sand fraction (2,000–250 μm). The phospholipid fatty acid analyses (PLFA) and denaturing gradient gel electrophoresis (DGGE) separation of 16S rRNA gene fragments revealed that the microbial biomass within the clay fraction was predominantly due to soil bacteria. In contrast, a high percentage of fungal-derived PLFA 18 : 2ω6 was found in the coarse sand fraction. Bacterial residues such as muramic acid accumulated in the finer fractions in relation to fungal residues. The fractions also differed with respect to substrate utilization: Urease was located mainly in the <2 μm fraction, alkaline phosphatase and arylsulfatase in the 2–63 μm fraction, and xylanase activity was equally distributed in all fractions. Heavy metal pollution significantly decreased the concentration of ninhydrin-reactive nitrogen of soil microorganisms in the silt and clay fraction and thus in the bulk soil. Soil enzyme activity was reduced significantly in all fractions subjected to heavy metal pollution in the order arylsulfatase >phosphatase >urease >xylanase. Heavy metal pollution did not markedly change the similarity pattern of the DGGE profiles and amino sugar concentrations. Therefore, microbial biomass and enzyme activities seem to be more sensitive than 16S rRNA gene fragments and microbial amino-sugar-N to heavy metal treatment. Received: 21 January 2000