Variations of Microbial Communities and the Contents and Isotopic Compositions of Total Organic Carbon and Total Nitrogen in Soil Samples during Their Preservation

Semi-sealed preservation of soil samples at different moisture of 4% and 23%,respectively, was simulated to observe the variations of soil microbial communities and determine the contents and isotopic compositions of the total organic carbon and total nitrogen on the 7th and 30th day, respectively.The results show that during preservation,the quantity of microbial communities tended to increase first and then decrease,with a wider variation range at higher moisture (23%).At the moisture content of 23%,th...     

青藏高原多年冻土区土壤需氧可培养细菌多样性及群落功能研究

以青藏高原腹地不同植被类型多年冻土区土壤细菌为研究对象, 分析了可培养菌群数量、 多样性和生理代谢功能的变化及其与环境因子间的关系. 结果显示: 从沼泽草甸到高寒荒漠, 土壤水分、 总碳、 总氮含量逐渐降低, pH值升高, 可培养细菌数量在2.97×10⁶~2.88×10⁷ CFU·g^-1, 与含水量、 总碳、 总氮显著正相关; Actinobacteria(51.4%)和γ-Proteobacteria(31.7%)为优势菌群, α-protebacteria仅在沼泽草甸中有分布, β-protebacteria、 Bacterioidetes丰度与含水量、 总碳、 总氮间显著正相关; 自沼泽到荒漠, 菌群代谢活性和Shannon功能多样性指数降低, pH与Shannon指数显著负相关, 继氨基酸类碳源之后, 多聚物逐渐成为被细菌群落主要利用的碳源种类. 研究表明, 伴随冻土退化地上植被逆向演替的过程, 青藏高原多年冻土地下土壤微生物群落丰度、 遗传和代谢功能多样性均发生了不同程度的响应.     

塔里木盆地西缘土壤碳氮垂直分布规律研究

棕漠土和灌淤土在塔里木盆地西缘洪积平原上广泛分布,文章选取这两种类型的土壤作为研究对象,测试分析了在不同的土壤层位有机碳和全氮的含量,探讨了有机碳和全氮含量、以及它们与粒级组之间的相关关系。研究结果表明:洪积平原两种土壤剖面在0～100cm层位上有机碳和全氮含量随着土壤层位深度的增加而降低,而在40～60cm层位上两种土壤的有机碳和全氮含量差值达到最大值,并且整个剖面上有机碳和全氮含量变化呈正相关的关系。     

森林土壤微生物与植物碳源的磷脂脂肪酸及其单体同位素研究

森林生态系统的土壤微生物群落组成和活性,是影响生物地球化学循环、有机质代谢和土壤质量的关键因素.磷脂脂肪酸(PLFA)是一类可有效表征活体微生物群落结构的生物标志物,而其单体稳定碳同位素(δ13C)水平对土壤微生物植物碳代谢具有独特的指示作用.本次研究以土壤PLFA为对象,分析了我国位处纬度梯度带上(24°N～47°N...     

Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic

A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (～2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss‐dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water‐saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. δ¹⁵N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in δ¹³C values appear to reflect mainly changes in plant assemblages. Positive shifts in both δ¹⁵N and δ¹³C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed ¹⁵N‐enrichment. Copyright © 2012 John Wiley & Sons, Ltd.     

祁连山青海云杉(Picea crassifolia)林土壤有机碳与化学性质的相互关系

通过对祁连山大野口流域的青海云杉林大样地进行土壤剖面取样, 分析了样地土壤有机碳与pH值、养分和阳离子交换量等基本化学性质的变化规律及其相互关系. 结果表明: 随土层深度不断增加, 土壤有机碳含量逐渐减小, 在20～30 cm以下趋于稳定(P > 0.05); 土壤pH值不断增大, 仅在0～10 cm与10～20 cm差异显著(P<0.05); 土壤全氮、速效氮、全磷和阳离子交换量不断减小, 全氮含量在30～40 cm以下趋于稳定(P > 0.05), 速效氮含量变化剧烈(P<0.05), 全磷含量差异性不显著(P > 0.05), 阳离子交换量与有机碳含量变化规律相同; 土壤速效磷、全钾和速效钾含量没有明显的变化规律, 速效磷和全钾含量差异性不显著(P > 0.05), 速效钾含量仅在0～10 cm与10～20 cm差异显著(P<0.05). 土壤有机碳与全氮、速效氮、全磷、速效磷、速效钾和阳离子交换量之间呈极显著和显著正相关, 与土壤pH值和全钾含量之间呈极显著和显著负相关. 土壤有机碳与其他基本化学性质的回归方程具有较高精度(R²=0.793), 影响土壤有机碳含量的主要化学因子依次为土壤阳离子交换量、速效钾和全磷含量.     

青藏高原东缘高寒草甸退化过程中植物群落物种多样性、生产力与土壤特性的关系

为了阐明高寒草甸退化过程中植物群落物种多样性、生产力与土壤特性的关系, 在青藏高原东缘的玛曲县沿着高寒草甸退化梯度选取了轻度退化草甸、中度退化草甸、重度退化草甸和沙化草甸, 测定了高寒草甸退化过程中植物群落物种多样性、生产力与土壤理化性状. 结果表明: 从轻度退化到中度、重度和沙化草甸, 植被地下生物量分别降低了36%、48%和91%, 总生物量分别降低了34%、47%和91%, 土壤有机碳分别下降了18%、81%和97%, 全N分别下降了25%、82%和95%, 全P含量分别下降了14%、33%和41%. 随着高寒草甸的退化, 植被群落的生物多样性和地上生物量呈先稳定后降低的趋势, 土壤砂粒含量、pH值和全K含量呈增加趋势, 黏粉粒呈降低趋势, 速效N、速效P和速效K呈先增加后降低的趋势. 相关分析表明, 群落物种多样性和生产力与土壤有机碳、全N、全P、速效N、速效P、速效K、黏粒含量、粉粒含量、水分含量均呈显著正相关(P<0.01), 而与土壤砂粒、全K和pH值均呈显著负相关(P<0.05). 因此, 高寒草甸退化过程中, 土壤质地、养分和水分等的复杂变化及其相互关系共同决定着高寒草甸群落物种多样性和生产力的变化. 同时, 植被生产力和土壤碳、氮的降低产生明显的正反馈效应, 导致在重度退化阶段和沙化阶段, 植被生产力和土壤碳氮的急剧下降.     

不同土地管理和利用方式喀斯特坡地养分和碳库管理指数的差异

文章选择环江喀斯特农业生态试验站坡地,设计封育、种植玉米、种植牧草、火烧、刈割和刈割除根6种处理方式,测定了不同处理下坡地土壤养分含量、有机碳、易氧化碳含量和碳库管理指数。结果表明,不同处理下土壤养分含量、有机碳含量和碳库管理指数均存在明显差异。土壤全氮、全磷、碱解氮、速效钾、有机碳和易氧化碳含量随土壤人为干扰的增大而减小,种植玉米、种植牧草和刈割除根处理由于人为干扰较大,上述指标显著低于封育和火烧处理。土壤全钾和速效磷含量均以种植玉米处理最高,而刈割处理最低。土壤缓效钾含量以封育最高,种植玉米和种植牧草处理次之,而刈割处理最低。与封育相比,各处理土壤碳库管理指数均显著降低,其中种植玉米和火烧处理最低,并显著低于其他各处理。此外,土壤全氮、全磷、全钾、碱解氮和有机碳含量随坡位的升高而降低。在喀斯特生态脆弱地区,自然封育有利于土壤养分和碳库管理指数的保持和提高。随着土壤人为干扰的增大,土壤养分含量和碳库管理指数下降。     

中国东部农耕区土壤微生物碳的分布及影响因素

对中国东部不同纬度带的6个地区的土壤微生物碳进行了研究。结果表明土壤微生物碳的分布受地理位置的影响较为明显:由北向南,东北地区的土壤微生物碳要高于其他地区。作为土壤有机质变化的灵敏度指标———微生物熵(微生物碳/总有机碳),在同一耕作方式下,其在不同地区的变化受土壤利用方式的影响较为明显:在连作系统下,菜地>粮地;而在轮作系统下,粮食-蔬菜轮作>蔬菜-蔬菜轮作。利用相关性分析寻求影响微生物碳分布的环境因素,结果表明,微生物碳(Micro-C)与土壤有机碳(TOC)、全氮(TN)、土壤含水率呈极显著正相关,而有机碳和全氮的分布主要受地理位置的影响。对不同土壤类型的微生物碳和微生物熵进行相关性分析,结果显示pH、年均温、含水率、TOC和TN是主要影响因素,关键影响因素因土壤类型不同而各异。     

我国不同区域农田养分平衡对土壤肥力时空演变的影响

区域农田养分盈亏是驱动农田土壤肥力时空变化的主要因素。对我国6个农业生态试验站（海伦、沈阳、 栾城、长武、常熟、鹰潭）站区农田土壤肥力在近年来时空演变的研究表明,除了海伦站黑土和常熟站水稻土的有机质和全氮平均含量下降外,其他站区均呈现增加趋势,主要原因是黑土和乌栅土有机质和全氮含量较高,目前农田有机C和N投入水平无法维持其平衡;6个站区土壤速效磷有增有减,而土壤速效钾除了栾城和鹰潭站区域外均呈降低趋势。从站区农田养分的年平衡与土壤养分的年变化量关系看,农田氮、磷、钾的盈亏量决定了土壤养分的变化方向。土壤有机碳和全氮的初始含量过高（分别超过15.1 g/kg和1.60 g/kg）时,也会导致其年际间的变化方向从增加变为降低。农田氮素盈亏量与土壤全氮变化量之间相关不显著,主要是由于化肥投入和作物籽粒输出的农田氮平衡不能完全代表土壤氮素的真实盈亏情况;而农田磷素和钾素的盈亏量与土壤速效磷和速效钾的年变化量的显著相关。     

青藏公路沿线土壤微生物数量变化及其影响因素研究

以青藏公路沿线土壤为研究对象, 研究了土壤可培养微生物数量的变化特征及影响因子. 结果表明: 青藏公路沿线土壤可培养微生物数量为0.77×10⁶~2.44×10⁷CFU·g^-1dw; 沿青藏公路从南(申格里贡山)到北(西大滩), 土壤可培养细菌与真菌数量表现为先迅速减少, 然后渐趋平缓; 可培养放线菌数量先减少后增加; 土壤总氮、 有机碳和含水量逐渐降低, 而pH值逐渐升高. C/N比率与真菌/细菌比率变化趋势相似, 均为先增加后减少. 土壤可培养微生物数量与理化因子的相关性分析结果表明: 青藏公路沿线土壤微生物数量主要受纬度和土壤理化性质的影响, 表现为微生物数量与纬度和pH值显著负相关, 而与总氮、 有机碳和含水量极显著正相关.     

Kankan diamonds (Guinea) III: δ13C and nitrogen characteristics of deep diamonds

Diamonds from the Kankan area in Guinea formed over a large depth profile beginning within the cratonic mantle lithosphere and extending through the asthenosphere and transition zone into the lower mantle. The carbon isotopic composition, the concentration of nitrogen impurities and the nitrogen aggregation level of diamonds representing this entire depth range have been determined. Peridotitic and eclogitic diamonds of lithospheric origin from Kankan have carbon isotopic compositions ('¹³C: peridotitic -5.4 to -2.2‰; eclogitic -19.7 to -0.7‰) and nitrogen characteristics (N: peridotitic 17-648 atomic ppm; eclogitic 0-1,313 atomic ppm; aggregation from IaA to IaB) which are generally typical for diamonds of these two suites worldwide. Geothermobarometry of peridotitic and eclogitic inclusion parageneses (worldwide sources) indicates that both suites formed under very similar conditions within the cratonic lithosphere, which is not consistent with a derivation of diamonds with light carbon isotopic composition from subducted organic matter within subducting oceanic slabs. Diamonds containing majorite garnet inclusions fall to the isotopically heavy side ('¹³C: -3.1‰ to +0.9‰) of the worldwide diamond population. Nitrogen contents are low (0-126 atomic ppm) and one of the two nitrogen-bearing diamonds shows such a low level of nitrogen aggregation (30% B-centre) that it cannot have been exposed to ambient temperatures of the transition zone (̿,400 °C) for more than 0.2 Ma. This suggests rapid upward transport and formation of some Kankan diamonds pene-contemporaneous to Cretaceous kimberlite activity. Similar to these diamonds from the asthenosphere and the transition zone, lower mantle diamonds show a small shift towards isotopic heavy compositions (-6.6 to -0.5‰, mode at -3.5‰). As already observed for other mines, the nitrogen contents of lower mantle diamonds were below detection (using FTIRS). The mutual shift of sublithospheric diamonds towards isotopic heavier compositions suggests a common carbon source, which may have inherited an isotopic heavy composition from a component consisting of subducted carbonates.     

大兴安岭多年冻土区不同林型土壤微生物群落特征

高纬度多年冻土区是全球变化的敏感区域,揭示不同林型土壤微生物群落的演变规律,对于理解气候变化对寒区生态系统的影响机制具有重要意义。以大兴安岭多年冻土区3种典型林型（落叶松林、樟子松林和白桦林）为研究对象,运用磷脂脂肪酸法（PLFA）系统研究土壤微生物群落结构间差异及与土壤因子的关系。结果表明：不同林型土壤中共检测到38种PLFA生物标记,含量较高的PLFA为16∶0、18∶0、19∶0和18∶2ω6c;各类群微生物中,细菌PLFA含量最高,占总磷脂脂肪酸的83.78%~90.55%,其次为真菌,放线菌最低;白桦林土壤总磷脂脂肪酸、革兰氏阴性菌、革兰氏阳性菌、真菌和放线菌的含量最高分别为22.03、5.13、4.90、1.88和0.77 nmol·g^-1,而樟子松林最低分别为14.25、2.75、2.75、1.34和0.51 nmol·g^-1。Shannon-Wiener多样性指数主要表现为白桦林 > 落叶松林 > 樟子松林。冗余分析结果为：土壤含水量、全氮、总有机碳与总磷脂脂肪酸、细菌、革兰氏阳性菌和革兰氏阴性菌呈显著正相关（P<0.05）;铵态氮、硝态氮、全磷与真菌和放线菌呈显著正相关（P<0.05）。大兴安岭多年冻土区不同林型间土壤微生物群落特征存在显著差异,土壤含水量、全氮和总有机碳是影响多年冻土微生物群落结构的主要因素。     

微生物降解有机物的碳氢同位素分馏研究进展

微生物降解使有机化合物的稳定碳、氢同位素发生不同程度分馏的研究在有机污染物来源和微生物环境修复等领域取得了长足进展,并对原油和天然气微生物降解研究有借鉴意义。微生物作用下的同位素分馏为动力同位素分馏,导致重同位素在残余物中富集。影响微生物降解有机物同位素分馏的主要因素有微生物的降解代谢途径、辅酶作用、降解类型与程度、同位素质量差异和有机物碳数等。不同的微生物代谢途径代表不同的生物化学反应,造成了同位素分馏的显著差异;辅酶对反应的催化作用使微生物作用造成的同位素分馏更加复杂。低碳数正构烷烃遭受微生物降解程度越高,碳、氢同位素的分馏也越大,同位素变重与降解程度之间有明显的相关性。但对于复杂化合物,由于降解的多级反应,同位素分馏与降解程度间的相关性并不明显。在同样降解程度下,氢同位素分馏大于碳同位素分馏,低碳数正构烷烃的同位素分馏大于高碳数正构烷烃的同位素分馏。     

Distribution characteristics and factors influencing microbial communities in the core soils of a seawater intrusion area in Longkou City,China

Microbes live throughout the soil profile. Microbial communities in subsurface horizons are impacted by a saltwater–freshwater transition zone formed by seawater intrusion (SWI) in coastal regions. The main purpose of this study is to explore the changes in microbial communities within the soil profile because of SWI. The study characterizes the depth-dependent distributions of bacterial and archaeal communities through high-throughput sequencing of 16S rRNA gene amplicons by collecting surface soil and deep core samples at nine soil depths in Longkou City, China. The results showed that although microbial communities were considerably impacted by SWI in both horizontal and vertical domains, the extent of these effects was variable. The soil depth strongly influenced the microbial communities, and the microbial diversity and community structure were significantly different (p < 0.05) at various depths. Compared with SWI, soil depth was a greater influencing factor for microbial diversity and community structure. Furthermore, soil microbial community structure was closely related to the environmental conditions, among which the most significant environmental factors were soil depth, pH, organic carbon, and total nitrogen.

     

Sulphur Enrichment in Organic Matter of Eastern Mediterranean Sapropels: A Study of Sulphur Isotope Partitioning

Sulphur isotope compositions and S/C ratios of organic matter were analysed in detail by combustion-isotope ratio monitoring mass spectrometry (C-irmMS) in eastern Mediterranean sediments containing three sapropels of different ages and with different organic carbon contents (sapropel S1 in core UM26, formed from 5–9 ka ago with a maximum organic carbon content of 2.3 wt%; sapropel 967 from ODP Site 160-967C, with an age of 1.8 Ma and a maximum organic carbon content of 7.4 wt%; and sapropel 969 from ODP Site 160-969E, with an age of 2.9 Ma and a maximum organic carbon content of 23.5 wt%). Sulphur isotopic compositions (34S) of the organic matter ranged from -29.5 to +15.8 and the atomic S/C ratio was 0.005 to 0.038. The organic sulphur in the sediments is a mixture of sulphur derived from (1) incorporation of 34S-depleted inorganic reduced sulphur produced by dissimilatory microbial sulphate reduction; and (2) biosynthetic sulphur with an isotopic signature close to seawater sulphate. The calculated biosynthetic fraction of organic sulphur in non-sapropelic sediments ranges from 68–87%. The biosynthetic fraction of the organic sulphur of the sapropels (60–22%) decreases with increasing organic carbon content of the sapropels. We propose that uptake of reduced sulphur into organic matter predominantly took place within sapropels where pyrite formation was iron-limited and thus an excess of dissolved sulphide was present for certain periods of time. Simultaneously, sulphide escaped into the bottom water and into sediments below the sapropels where pyrite formation occurred.     

CN ratios in Pacific deep-sea sediments: Effect of inorganic ammonium and organic nitrogen compounds sorbed by clays

Analyses of organic carbon, total nitrogen, and inorganically bound ammonium (exchangeable and fixed ammonium) in two oxic deep-sea sediment cores from the Central Pacific Ocean revealed insufficiently high inorganic ammonium contents of these sediments to explain the low C/N ratios, although representing 20–45% of the total nitrogen.Both, organic carbon/total nitrogen ratios (ranging from 3.9?1.3) and organic carbon/organic nitrogen ratios (5.6?1.9) decrease with increasing sediment depth, the latter indicating a real enrichment of organic nitrogen compounds during diagenesis relative to total organic matter.Organic matter/alumina relationships indicate that this unusual preservation of organic nitrogen compounds is probably caused by sorption to clay minerals protecting them against bacterial attack.     

马衔山多年冻土与季节冻土区土壤微生物量及酶活性的季节动态

为了研究马衔山多年冻土区和非多年冻土区土壤微生物碳氮、土壤酶活性的差异,选取多年冻土区、季节冻土区和交界区为对象,分析了0~30 cm土层微生物碳氮和转化酶、脲酶、中性磷酸酶、淀粉酶、过氧化氢酶、多酚氧化酶酶活性不同季节的变化特征。结果表明：全氮、总有机碳、微生物量碳氮与多数土壤酶之间呈显著相关关系。在不同区域,土壤微生物碳氮均在0~10 cm含量最高,10~20 cm次之,20~30 cm最低。土壤微生物碳氮在生长季表现为含量逐渐增加,但是多年冻土区与季节冻土区差异不大。土壤酶活性在深度方面表现与微生物碳氮含量变化一致。土壤酶并无的季节变化规律。在多年冻土区,转化酶、多酚氧化酶和磷酸酶活性明显高于非多年冻土区。本研究表明,尽管多年冻土区的植被和土壤总有机碳明显高于非多年冻土区,其土壤微生物碳氮含量相当,且一些土壤酶活性也相当。说明非多年冻土区土壤的生物地球化学相对强度较大。因此,多年冻土退化后可能会导致生态系统的退化。     

艾比湖地区冻融作用对土壤微生物数量和群落结构的影响

通过对艾比湖地区冻融阶段7个典型样地野外采样和室内分析,研究了冻融作用条件下土壤微生物数量与土壤性质的关系、土壤微生物数量变化特征和土壤微生物群落结构的变化特征. 结果表明：不同冻融阶段,不同种类微生物数量受到不同土壤理化因子的制约. 1月,细菌数量与土壤有机质含量呈显著正相关(P<0.05),真菌数量与土壤含水量和土壤有机质含量呈极显著正相关(P<0.01),与土壤全氮和土壤孔隙度呈显著正相关(P<0.05);3月,只有真菌数量与土壤含水量呈极显著正相关(P<0.01);4月,放线菌数量与土壤有机碳和全氮含量呈显著正相关(P<0.05),然而与土壤pH值呈显著负相关(P<0.05). 总体来讲,冻结期土壤微生物数量较低,冻融后期(4月)达到峰值,其中,7 a 撂荒地的微生物数量最高,3 a撂荒地最低. 在研究区寒冷季节,微生物类群中放线菌占主导地位(81.9%);融化阶段,则是细菌占主要地位(52.1%~53.9%).     

Stable carbon and nitrogen isotopic compositions of high molecular weight dissolved organic matter from four U.S. estuaries

High molecular weight dissolved organic matter (HMW-DOM) represents an important component of dissolved organic carbon (DOC) in seawater and fresh-waters. In this paper, we report measurements of stable carbon (δ¹³C) isotopic compositions in total lipid, total hydrolyzable amino acid (THAA), total carbohydrate (TCHO) and acid-insoluble “uncharacterized” organic fractions separated from fourteen HMW-DOM samples collected from four U.S. estuaries. In addition, C/N ratio, δ¹³C and stable nitrogen (δ¹⁵N) isotopic compositions were also measured for the bulk HMW-DOM samples. Our results indicate that TCHO and THAA are the dominant organic compound classes, contributing 33-46% and 13-20% of the organic carbon in HMW-DOM while total lipid accounts for only <2% of the organic carbon in the samples. In all samples, a significant fraction (35-49%) of HMW-DOM was included in the acid-insoluble fraction. Distinct differences in isotopic compositions exist among bulk samples, the compound classes and the acid-insoluble fractions. Values of δ¹³C and δ¹⁵N measured for bulk HMW-DOM varied from −22.1 to −30.1‰ and 2.8 to 8.9‰, respectively and varied among the four estuaries studied as well. Among the compound classes, TCHO was more enriched in ¹³C (δ¹³C = −18.5 to −22.8‰) compared with THAA (δ¹³C = −20.0 to −29.6‰) and total lipid (δ¹³C = −25.7 to −30.7‰). The acid-insoluble organic fractions, in general, had depleted ¹³C values (δ¹³C = −23.0 to −34.4‰). Our results indicate that the observed differences in both δ¹³C and δ¹⁵N were mainly due to the differences in sources of organic matter and nitrogen inputs to these estuaries in addition to the microbial processes responsible for isotopic fractionation among the compound classes. Both terrestrial sources and local sewage inputs contribute significantly to the HMW-DOM pool in the estuaries studied and thus had a strong influence on its isotopic signatures.