Ratio [13C]/[12C] as an index for express estimation of hydrocarbon-oxidizing potential of microbiota in soil polluted with crude oil

The hydrocarbon-oxidizing potential of soil microbiota and hydrocarbon-oxidizing microorganisms introduced into soil was studied based on the quantitative and isotopic characteristics of carbon in products formed in microbial degradation of oil hydrocarbons. Comparison of CO₂ production rates in native soil and that polluted with crude oil showed the intensity of microbial mineralization of soil organic matter (SOM) in the presence of oil hydrocarbons to be higher as compared with non-polluted soil, that is, revealed a priming effect of oil. The amount of carbon of newly synthesized organic products (cell biomass and exometabolites) due to consumed petroleum was shown to significantly exceed that of SOM consumed for production of CO₂. The result of microbial processes in oil-polluted soil was found to be a potent release of carbon dioxide to the atmosphere.     

Roots and fungi accelerate carbon and nitrogen cycling in forests exposed to elevated CO2

A common finding in multiple CO(2) enrichment experiments in forests is the lack of soil carbon (C) accumulation owing to microbial priming of 'old' soil organic matter (SOM). However, soil C losses may also result from the accelerated turnover of 'young' microbial tissues that are rich in nitrogen (N) relative to bulk SOM. We measured root-induced changes in soil C dynamics in a pine forest exposed to elevated CO(2) and N enrichment by combining stable isotope analyses, molecular characterisations of SOM and microbial assays. We find strong evidence that the accelerated turnover of root-derived C under elevated CO(2) is sufficient in magnitude to offset increased belowground inputs. In addition, the C losses were associated with accelerated N cycling, suggesting that trees exposed to elevated CO(2) not only enhance N availability by stimulating microbial decomposition of SOM via priming but also increase the rate at which N cycles through microbial pools.     

Isolation of hydrocarbon-oxidizing psychrophilic bacteria from oil-polluted soils

Microorganisms growing on a mineral medium with crude oil and its light fractions as only carbon and energy sources have been isolated from samples of oil-polluted soils collected in the Usa District (Komi Republic, Russia). For the first time, hydrocarbon-oxidizing psychrophilic bacteria of the genus Cytophaga have been found that are clearly capable of consuming crude oil hydrocarbons. A method for cultivating microorganisms on porous plastic is proposed. The data from the literature on the response of soil microbiota to oil pollution indicate that the pollution can activate or suppress the growth of various physiological groups of microorganisms [1]. Different soil and climatic conditions and pollution levels can give rise to different microbial cenoses, which include different associations and predominant microbial species.     

Bioremediation of oil-polluted soils: Using the [13C]/[12C] ratio to characterize microbial products of oil hydrocarbon biodegradation

We compared data on the extent of bioremediation in soils polluted with oil. The data were obtained using conventional methods of hydrocarbon determination: extraction gas chromatography-mass spectrometry, extraction IR spectroscopy, and extraction gravimetry. Due to differences in the relative abundances of the stable carbon isotopes (¹³C/¹²C) in oil and in soil organic matter, these ratios could be used as natural isotopic labels of either substance. Extraction gravimetry in combination with characteristics of the carbon isotope composition of organic products in the soil before and after bioremediation was shown to be the most informative approach to an evaluation of soil bioremediation. At present, it is the only method enabling quantification of the total petroleum hydrocarbons in oil-polluted soil, as well as of the amounts of hydrocarbons remaining after bioremediation and those microbially transformed into organic products and biomass.     

Enhanced root exudation induces microbial feedbacks to N cycling in a pine forest under long-term CO2 fumigation

The degree to which rising atmospheric CO(2) will be offset by carbon (C) sequestration in forests depends in part on the capacity of trees and soil microbes to make physiological adjustments that can alleviate resource limitation. Here, we show for the first time that mature trees exposed to CO(2) enrichment increase the release of soluble C from roots to soil, and that such increases are coupled to the accelerated turnover of nitrogen (N) pools in the rhizosphere. Over the course of 3 years, we measured in situ rates of root exudation from 420 intact loblolly pine (Pinus taeda L.) roots. Trees fumigated with elevated CO(2) (200 p.p.m.v. over background) increased exudation rates (μg C cm(-1) root h(-1) ) by 55% during the primary growing season, leading to a 50% annual increase in dissolved organic inputs to fumigated forest soils. These increases in root-derived C were positively correlated with microbial release of extracellular enzymes involved in breakdown of organic N (R(2) = 0.66; P = 0.006) in the rhizosphere, indicating that exudation stimulated microbial activity and accelerated the rate of soil organic matter (SOM) turnover. In support of this conclusion, trees exposed to both elevated CO(2) and N fertilization did not increase exudation rates and had reduced enzyme activities in the rhizosphere. Collectively, our results provide field-based empirical support suggesting that sustained growth responses of forests to elevated CO(2) in low fertility soils are maintained by enhanced rates of microbial activity and N cycling fuelled by inputs of root-derived C. To the extent that increases in exudation also stimulate SOM decomposition, such changes may prevent soil C accumulation in forest ecosystems.     

Use of carbon isotope composition for characterization of microbial activity in arable soils

The effect of glucose on microbial mineralization of soil organic matter (SOM) was studied in arable soil specimens. The flows of carbon dioxide generated during this degradation were deduced from differences in the carbon isotope ratios of glucose (delta13C = -11.4 per mil) and SOM (delta13C = -27.01 per mil). The priming effect of glucose and respiratory quotient (RQ) were taken as indices of activation of SOM-consuming microbiota. The data on microbial mineralization of organic matter in soil, obtained in this study, show that addition of a readily consumable substance (glucose) to soil favors SOM degradation and increases the release of carbon dioxide from soil to atmosphere.     

土壤有机质概念和分组技术研究进展

土壤有机质一直是土壤学研究领域的重点,在过去的50年里,对土壤质量可持续性观念的增强和寻找快速判断人为因素对土壤质量影响方向指标的强烈愿望导致了土壤有机质的研究重点发生了急剧变化：对农业措施反映慢的土壤腐殖质类物质的研究正在退出土壤有机质研究领域,而侧重点逐渐转向了土壤中未受微生物作用或正在受微生物降解的有机残体;也出现了新的土壤有机质研究概念和对应测试手段：土壤有机质的比重分组、与有机质结合的土壤颗粒大小分组、土壤团聚体中的POM和iPOM以及土壤水溶性有机质和微生物体C等概念和测试手段被相继提了出来,土壤有机质的研究重点正在从土壤微生物的作用产物(腐殖质)向土壤微生物作用前的、具有部分生物活性的有机质(轻组有机质、砂粒组和粗粉砂粒组中的有机质、POM和iPOM)和完全具有生物活性的有机质(微生物体C和水溶性有机质)转移,这一过程与土壤有机质概念的拓展密不可分。     

Use of Carbon Isotope Composition for Characterization of Microbial Activity in Arable Soils

The effect of glucose on microbial mineralization of soil organic matter (SOM) was studied in arable soil specimens. The fluxes of carbon dioxide generated during this degradation were deduced from differences in the carbon isotope abundance ratios of glucose δ¹³C = –11.4 per mil) and SOM δ¹³C = –27.01 per mil). The priming effect of glucose and respiratory quotient (RQ) were taken as indices of activation of SOM-consuming microbiota. The data on microbial mineralization of organic matter in soil obtained in this study show that the addition of a readily consumable substance (glucose) to soil favors SOM degradation and increases the release of carbon dioxide from soil to atmosphere.     

典型矿冶区周边土壤微生物功能特征及影响因素

土壤微生物对重金属污染胁迫敏感,但在实际野外环境中,土壤微生物群落生态效应通常是污染胁迫和环境因素综合作用的结果。为探究重金属污染土壤中微生物群落生态效应发生变化的主控因素,本研究以湖南省某典型矿冶区周边不同土地利用类型土壤为研究对象,以土壤碳氮循环过程主要的微生物功能指标土壤微生物生物量碳(MBC)、基础呼吸(BR)、诱导呼吸(SIR)和硝化潜势(PNR)为生态效应终点,进行采样调查分析。结果表明: 土地利用类型对MBC、BR和SIR影响均不显著;研究区土壤微生物功能的主要影响因子包括CaCl₂提取态Pb(CaCl₂-Pb)含量与土壤有机质(SOM)含量。多元回归分析结果表明,在CaCl₂-Pb含量为0.004～13.14 mg·kg^-1及SOM含量为0.24%～4.34%的条件下,土壤CaCl₂-Pb和SOM含量可以共同解释土壤中BR、SIR和PNR总变异的39.8%～58.3%;中等含量下(SOM在1.70%～2.36%,CaCl₂-Pb在0.004～12.98 mg·kg^-1),土壤CaCl₂-Pb和SOM含量与BR、SIR和PNR的变化能够建立显著的暴露-效应关系,可以作为测定终点定量评价重金属污染对微生物群落功能的生态效应。     

The Microbial Efficiency‐Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

The decomposition and transformation of above‐ and below‐ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant‐derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency‐Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix.     

油气微生物勘探机理及应用

【目的】微生物油气勘探技术是基于油气藏的轻烃微渗漏原理衍生的地表勘探技术。油气藏中的轻烃部分(C1-C5)以微渗漏的方式通过上覆的沉积层,在近地表土壤中诱导专门利用轻烃的微生物繁殖与生长,油气区的微生物种类与浓度有别于下伏没有油气藏的地区。通过分析微生物的浓度异常特征,对油气富集区及油气藏进行研究和预测。【方法】在人工模拟条件下研究油气微生物数量和群落异常特征,在此基础上,以海相碳酸盐岩气田普光气田为研究对象,进一步开展微生物勘探研究,鉴定油气藏上方气态烃氧化过程的微生物驱动者,提取土壤中的微生物异常信息。【结果】人工模拟条件下发现Lacibacter cauensis、Methylococcaceae、Methylophilaceae与甲烷气体培养正相关(气指示菌),而未培养的硫氧化微生物等则与丁烷培养正相关(油指示菌)。【结论】进一步在普光气田原位研究中进行验证,发现地表油气微生物数量和群落异常与油气藏有较好的关联性;与油气化探指标对比后发现,油气藏上方微生物正异常和轻烃负异常具有较为明显的互补关系。本研究深化了对典型油气藏上方气态烃氧化微生物转化机制的认识,为油气微生物勘探技术提供理论与实践依据。     

Priming effect and microbial diversity in ecosystem functioning and response to global change: a modeling approach using the SYMPHONY model

Integration of the priming effect (PE) in ecosystem models is crucial to better predict the consequences of global change on ecosystem carbon (C) dynamics and its feedbacks on climate. Over the last decade, many attempts have been made to model PE in soil. However, PE has not yet been incorporated into any ecosystem models. Here, we build plant/soil models to explore how PE and microbial diversity influence soil/plant interactions and ecosystem C and nitrogen (N) dynamics in response to global change (elevated CO₂ and atmospheric N depositions). Our results show that plant persistence, soil organic matter (SOM) accumulation, and low N leaching in undisturbed ecosystems relies on a fine adjustment of microbial N mineralization to plant N uptake. This adjustment can be modeled in the SYMPHONY model by considering the destruction of SOM through PE, and the interactions between two microbial functional groups: SOM decomposers and SOM builders. After estimation of parameters, SYMPHONY provided realistic predictions on forage production, soil C storage and N leaching for a permanent grassland. Consistent with recent observations, SYMPHONY predicted a CO₂‐induced modification of soil microbial communities leading to an intensification of SOM mineralization and a decrease in the soil C stock. SYMPHONY also indicated that atmospheric N deposition may promote SOM accumulation via changes in the structure and metabolic activities of microbial communities. Collectively, these results suggest that the PE and functional role of microbial diversity may be incorporated in ecosystem models with a few additional parameters, improving accuracy of predictions.     

The effect of film-corrected light on oxygenase activity of microorganisms of the genus <Emphasis Type="Italic">Pseudomonas</Emphasis>

The influence of the light transformed by a light-correcting film on the growth dynamics and enzymatic activity of hydrocarbon-oxidizing microorganisms of the genus Pseudomonas (P. stutzeri and P. putida) was investigated under laboratory conditions in liquid medium with 2% oil. The numbers of investigated microorganisms increased by 2–2.5 orders of magnitude due to application of the light-correcting film as a cover material. The dehydrogenase and catalase activities increased by 2–2.5 times. The rate of accumulation of aldehydes (intermediate products of metabolism of oil hydrocarbons) increased by 2.5 times. According to the data of gas-liquid chromatography and elemental analysis, the processes of microbial oxidation of oil hydrocarbons proceeded much faster than in the control variants.     

Biochar stimulates the decomposition of simple organic matter and suppresses the decomposition of complex organic matter in a sandy loam soil

Incorporating crop residues and biochar has received increasing attention as tools to mitigate atmospheric carbon dioxide (CO₂) emissions and promote soil carbon (C) sequestration. However, direct comparisons between biochar, torrefied biomass, and straw on both labile and recalcitrant soil organic matter (SOM) remain poorly understood. In this study, we explored the impact of biochars produced at different temperatures and torrefied biomass on the simple C substrates (glucose, amino acids), plant residues (Lolium perenne L.), and native SOM breakdown in soil using a ¹⁴C labeling approach. Torrefied biomass and biochars produced from wheat straw at four contrasting pyrolysis temperatures (250, 350, 450, and 550 °C) were incorporated into a sandy loam soil and their impact on C turnover compared to an unamended soil or one amended with unprocessed straw. Biochar, torrefied biomass, and straw application induced a shift in the soil microbial community size, activity, and structure with the greatest effects in the straw‐amended soil. In addition, they also resulted in changes in microbial carbon use efficiency (CUE) leading to more substrate C being partitioned into catabolic processes. While overall the biochar, torrefied biomass, and straw addition increased soil respiration, it reduced the turnover rate of the simple C substrates, plant residues, and native SOM and had no appreciable effect on the turnover rate of the microbial biomass. The negative SOM priming was positively correlated with biochar production temperature. We therefore ascribe the increase in soil CO₂ efflux to biochar‐derived C rather than that originating from SOM. In conclusion, the SOM priming magnitude is strongly influenced by both the soil organic C quality and the biochar properties. In comparison with straw, biochar has the greatest potential to promote soil C storage. However, straw and torrefied biomass may have other cobenefits which may make them more suitable as a CO₂ abatement strategy.     

长白山原始阔叶红松林土壤有机质组分小尺度空间异质性

土壤有机质(SOM)对于维持生态系统生产力具有非常重要的意义,有机质的组成、空间分布和空间关联性是影响和控制诸多生态系统过程的重要因素。应用地统计学方法,对长白山原始阔叶红松林局部尺度内0—20 cm土壤有机质与活性有机质的空间异质性进行了研究,并通过交叉半方差分析探讨了二者之间的相关性。研究结果表明:(1)总体上来说,土壤有机碳(SOC)、全氮(TN)、颗粒态有机碳(POC)和颗粒态有机氮(PON)空间异质性较小;而土壤微生物量碳(MBC)、微生物量氮(MBN)和表层(0—10 cm)溶解性有机碳(DOC)的空间异质性较大;(2)SOC、TN、MBC、DOC、POC和PON随着深度的增加空间自相关性增加;而溶解性有机氮(DON)的空间自相关性随深度的增加变化不大;(3)SOC与TN在表层和下层(10—20 cm)均存在空间上的正相关关系;(4)SOC、TN在表层和下层分别与MBC、MBN、DOC、DON和POC呈空间上的正相关性,但是与PON之间的空间相关关系较差;(5)不同土层深度的土壤活性有机质之间的相关关系存在差异。在表层,除POC,PON外,其余土壤活性有机质组分在空间上两两相关;但是随着土壤深度的增加,活性有机质变量之间在空间上两两相关。研究结果表明土壤有机质组分在长白山原始阔叶红松林小尺度内存在不同空间异质性和空间关联性,这为人们更好的理解森林生态系统功能(如土壤养分循环)提供了重要的理论依据。     

Transplantation of organic surface horizons of boreal soils into warmer regions alters microbiology but not the temperature sensitivity of decomposition

Changes in soil carbon, the largest terrestrial carbon pool, are critical for the global carbon cycle, atmospheric CO₂ levels and climate. Climate warming is predicted to be most pronounced in the northern regions and therefore the large soil carbon pool residing in boreal forests will be subject to larger global warming impact than soil carbon pools in the temperate or the tropical forest. A major uncertainty in current estimates of the terrestrial carbon balance is related to decomposition of soil organic matter (SOM). We hypothesized that when soils are exposed to warmer climate the structure of the ground vegetation will change much more rapidly than the dominant tree species. This change will alter the quality and amount of litter input to the soil and induce changes in microbial communities, thus possibly altering the temperature sensitivity of SOM decomposition. We transferred organic surface soil sections from the northern borders of the boreal forest zone to corresponding forest sites in the southern borders of the boreal forest zone and studied the effects of warmer climate after an adaptation period of 2 years. The results showed that initially ground vegetation and soil microbial community structure and community functions were different in northern and southern forest sites and that 2 years of exposure to warmer climate was long enough to cause changes in these ecological indicators. The rate of SOM decomposition was approximately equally sensitive to temperature irrespective of changes in vegetation or microbial communities in the studied forest sites. However, as temperature sensitivity of the decomposition increases with decreasing temperature regime, the proportional increase in the decomposition rate in northern latitudes could lead to significant carbon losses from the soils.     

Legacy Effects of Oil Road Reclamation on Soil Biology and Plant Community Composition

Following the unprecedented oil drilling presently occurring in western North Dakota, thousands of kilometers of oil roads must be reclaimed to an acceptable post‐extraction condition. This study assessed the soil biological and plant communities of nine decommissioned oil roads reclaimed during three periods between 1983 and 2002 in the Little Missouri National Grasslands of western North Dakota. We hypothesized that time‐since‐reclamation would positively affect soil biological and plant communities and, consequently, success of reclamation at older sites. To assess this hypothesis, we measured soil enzyme activity, soil microbial community composition, plant community composition, and soil physical and chemical properties along a gradient extending from road‐center to adjacent native prairie for the nine roads. Time‐since‐reclamation did not affect soil and plant properties measured, indicating that older reclamations are not more similar to native prairie than reclamations occurring more recently. A strong gradient between samples from road‐center and native prairie was identified with univariate and ordination analyses, indicating that soil and plant communities of reclaimed oil roads do not resemble those of the surrounding prairie. Soil organic matter (SOM) was identified as the most significantly affected soil property, being 30% lower on reclaimed roads than prairie. The relationship between SOM, microbial community, and plant community suggests that incorporating additional SOM could hasten reclamation as a result of improving the physical environment for plants and providing a labile carbon and energy source for the soil microbial community which, in turn, will enhance the nutrient and physical conditions for plant growth.     

Influence of rhizodeposition under elevated CO2 on plant nutrition and soil organic matter

Atmospheric CO₂ concentrations can influence ecosystem carbon storage through net primary production (NPP), soil carbon storage, or both. In assessing the potential for carbon storage in terrestrial ecosystems under elevated CO₂, both NPP and processing of soil organic matter (SOM), as well as the multiple links between them, must be examined. Within this context, both the quantity and quality of carbon flux from roots to soil are important, since roots produce specialized compounds that enhance nutrient acquisition (affecting NPP), and since the flux of organic compounds from roots to soil fuels soil microbial activity (affecting processing of SOM).From the perspective of root physiology, a technique is described which uses genetically engineered bacteria to detect the distribution and amount of flux of particular compounds from single roots to non-sterile soils. Other experiments from several labs are noted which explore effects of elevated CO₂ on root acid phosphatase, phosphomonoesterase, and citrate production, all associated with phosphorus nutrition. From a soil perspective, effects of elevated CO₂ on the processing of SOM developed under a C4 grassland but planted with C3 California grassland species were examined under low (unamended) and high (amended with 20 g m^–2 NPK) nutrients; measurements of soil atmosphere 13C combined with soil respiration rates show that during vegetative growth in February, elevated CO₂ decreased respiration of carbon from C4 SOM in high nutrient soils but not in unamended soils.This emphasis on the impacts of carbon loss from roots on both NPP and SOM processing will be essential to understanding terrestrial ecosystem carbon storage under changing atmospheric CO₂ concentrations.Abbreviations SOM soil organic matter - NPP net primary productivity - NEP net ecosystem productivity - PNPP p-nitrophenyl phosphate     

胜利油田采油区土壤石油污染状况及其微生物群落结构

基于不同开采年代新油井(2011—)和老油井(1966—2003年)周边土壤的调查取样,研究了采油区土壤石油污染状况,利用PCR-DGGE和克隆测序技术,探讨了新、老油井周边土壤微生物的群落结构.结果表明:油井周边土壤均受到不同程度的石油污染,其石油烃含量大多高于土壤石油污染临界值(500 mg·kg^-1),且老油井周边土壤污染水平更高.污染土壤石油烃含量与土壤有机碳、全氮和速效钾含量呈显著正相关.老油井周边土壤微生物群落多样性指数随污染水平的增大而减小,新油井则呈相反的趋势.DGGE图谱优势条带测序结果表明,油井周边土壤均存在明显的优势菌,大多为石油烃相关菌和烃类降解菌,如微杆菌属、链霉菌属、迪茨氏菌属、黄杆菌属及α、γ变形菌等.
     

湿润亚热带峰丛洼地岩溶土壤系统中碳分布及其转移

以桂林丫吉村岩溶试验场为例,研究了湿润亚热带峰丛洼地表层岩溶带生物量碳库、凋落物碳库、土壤有机碳库（ＳＯＭ）及其活泼性、有机碳分解速率、土壤中ＣＯ２浓度和土壤呼吸ＣＯ２排放,表明岩溶系统中丰富的碳库提供了系统中ＣＯ２的来源,并用δ＾１３Ｃ证实春夏岩溶活跃季节中岩溶输出Ｃ约６０％来自土壤ＣＯ２。由此认为,驱动岩溶作用的ＣＯ２并非直接来自大气ＣＯ２,而是大气－植物－土壤－水碳素转移的结果,因而揭示了土