A novel method of quantifying root exudation in the presence of soil microflora

A microcosm is described in which root exudation may be estimated in the presence of microorganisms. Ryegrass seedlings are grown in microcosms in which roots were spatially separated from a microbial inoculant by a Millipore membrane. Seedlings grown in the microcosms were labelled with [¹⁴C]-CO₂, and the fate of the label within the plant and rhizosphere was determined. Inoculation of the microcosms with Cladosporium resinae increased net fixation of the [¹⁴C] label compared to plants grown under sterile conditions. Inoculation also increased root exudation. The use of the microcosm was illustrated and its applications discussed.     

黄河三角洲滨海湿地微生物多样性及其驱动因子

微生物在湿地的生物地球化学循环和生态功能调节中发挥着重要作用,对全球气候变化具有重大影响,对维持全球生态系统的健康至关重要。以黄河三角洲滨海湿地为研究对象,通过采集代表性植被群落的土壤表层和部分植物根系,探究土壤微生物群落组成、根际微生物、环境因子及其内在的关联性和影响机制。研究结果表明不同植被覆盖地区微生物多样性存在差异,芦苇区和柽柳区微生物丰度高于泥滩区、碱蓬区和棉田,海漫滩微生物丰度高于河漫滩地和泥滩。土壤微生物菌群结构和多样性显著高于根际：土壤细菌的香农指数约为4-5.5,根际微生物的香农指数约为0-4。土壤细菌主要为厚壁菌门、变形菌门、拟杆菌门和放线菌门,占样品总数的90%以上;而根际细菌主要是蓝藻门、变形菌门和放线菌门,二者在属水平上的菌群结构差异更加明显。环境因子的含量与生境类型有关,SO₄^2-和NO₃^-的相关性最高,植被覆盖区土壤中Mn⁴⁺、Fe³⁺和水解氮的含量低于滩涂裸地。冗余分析（RDA）表明,pH值在小空间尺度上对湿地土壤中细菌群落的影响较小,环境因子在门和属水平的解释率分别为89.7%和86.8%,其中K（23.4%）、NO₂^-（11.8%）、Mn⁴⁺（9.8%）和Na（8.0%）是解释门水平微生物区系结构变化和组成的主要因子。研究为理解湿地微生物多样性与湿地生态系统功能之间的影响机制提供了一个生态学视角,有助于了解黄河三角洲滨海湿地土壤和植物根际的细菌分布特征,对黄河三角洲退化滨海湿地的生物修复具有重要的指导意义。     

Biodegradation of Trichloroacetic Acid in Norway Spruce/Soil System

Trichloroacetic acid (TCA) belongs to secondary atmospheric pollutants affecting the forest health. Distribution of [1,2-¹⁴C]TCA-residues and TCA biodegradation were investigated in 4-year-old nursery-grown trees of Norway spruce [Picea abies (L.) Karst.] in the whole plant/soil system. Radioactivity was monitored in needles, wood, roots and soil as well as in the air. During two weeks of exposure TCA was continuously degraded, especially in the soil. Estimates of radioactivity balance showed loss of radioactivity into the atmosphere in the form of ¹⁴CO₂; unincorporated [1,2-¹⁴C]TCA, chloroform, carbon monoxide and methane were not detected at all. TCA degradation to CO₂ was indicated also in the spruce needles. Moreover, it was found that soil litter contained [1,2-¹⁴C]TCA unavailable to microorganisms.     

Chemical oxygen demand,nitrogen and phosphorus removal by subsurface wetlands with Phragmites vegetation in different models

To improve the removal efficiency of subsurface wetlands vegetated mainly by Phragmites, pilot‐scale gravel‐based wetlands were used to treat sewage characterized by chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) pollution. For Phragmites vegetation, COD, TP and TN removal loads of wetland vegetation with Phragmites australis–Typha angustata–Scirpus validus as main species reached 0.517 g m^?2 d^?1, 0.277 g P m^?2 d^?1 and 0.023 g N m^?2 d^?1. The COD removal loads in pilot‐scale and medium‐scale (260 m² in area) wetlands with Phragmites‐monoculture vegetation were 0.62–0.64 g m^?2 d^?1, while that of P. australis–T. angustata–S. validus wetland reached 0.974 g m^?2 d^?1. Thus, the preferable poly‐culture model for Phragmites wetland vegetation was P. australis, T. angustata, S. validus and Zizania latifolia with stem density ratio of 8:1:5:1. After harvest, nitrogen and phosphorus standing stocks of wetland vegetations ranged only 2.2–9.93 g N m^?2 and 5.39–13.5 g P m^?2, respectively, as both the above ground biomass and the nitrogen and phosphorus contents of the wetland vegetation harvested in late autumn were low.     

人工湿地反应性填料开发及其脱氮除磷性能研究

【目的】人工湿地填料作为反硝化电子供体可以高效且稳定地脱氮除磷,但是填料的选用方式和作用机理尚不明确。【方法】本文以磁黄铁矿、菱铁矿和农业废弃物(木屑等)为人工湿地填料,研究了其对人工湿地反硝化脱氮除磷的效果。【结果】结果显示,质量比1:1的矿石组合和木屑以3:1的质量比作为混合填料,驯化8个周期后NO₃^--N和PO₄^3--P的平均去除率达到88.6%和88.9%。扫描电子显微镜(scanning electron microscopy,SEM)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)、X射线衍射仪(X-ray diffraction,XRD)和群落分析结果表明,微生物能有效利用矿石及其次生产物和木屑进行高效和持久的脱氮除磷,脱氮除磷功能菌硫杆菌(Thiobacillus)、罗姆布茨菌(Romboutsia)和溶杆菌(Lysobacter)得到了富集。【结论】本研究为人工湿地实际应用中新型填料的选择提供理论依据与指导意义。     

Pyrosequencing Reveals Bacterial Diversity in the Rhizosphere of Three Phragmites australis Ecotypes

Here we present the use of high-throughput DNA pyrosequencing to assess bacterial diversity in the rhizosphere of three Phragmites australis ecotypes from the Hexi Corridor, China. In total, 43404 sequences were obtained for the three ecotypes, representing 31 phyla and a small amount of unclassified bacteria. The predominant bacterial groups in the rhizosphere of P. australis were Proteobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Gemmatimonadetes and Planctomycetes. The bacterial community structure varied with the different degrees of wetland degradation, which were exhibited by the three P. australis ecotypes in the study area. At the phylum level, the Caldiserica, Chlamydiae, Deferribacteres, Lentisphaerae, and candidate division WS3 were only detected in the swamp reed (SR) sample. Then, δ-proteobacteria, Acidobacteria, Cyanobacteria and Fusobacteria decreased, the Actinobacteria increased with the degree of degradation from SR through salt meadow reed (SMR) to dune reed (DR). The functional bacterial genera also varied with wetland degradation. The sulfur and sulfate-reducing, nitrifying and nitrogen-fixing bacteria were more abundant in the rhizosphere of the SR sample. Methane-oxidizing bacteria were abundant in the SR and DR samples but less so in the SMR. In our study, pyrosequencing of different P. australis ecotypes provided insight into the structural variation of the rhizosphere bacterial community. This study gave a database for the use of bacteria in the protection and ecological restoration of wetland.     

龙凤湿地与珰奈湿地底泥细菌古菌多样性及其对环境因子的响应

【背景】城市湿地和天然湿地受到人为扰动影响的程度显著不同。【目的】研究2种不同类型湿地底泥微生物多样性及种类的差异。【方法】采集冬夏两季城市湿地(龙凤湿地)和天然湿地(珰奈湿地)的底泥样品,使用16S rRNA基因测序技术测定底泥中细菌和古菌群落结构,分析2种湿地底泥的细菌、古菌差异及环境因素与微生物的相关性。【结果】龙凤湿地底泥中的硫杆菌属(Thiobacillus)、芽孢杆菌属(Bacillus)和鞘氨醇单胞菌属(Sphingomonas)丰度显著高于珰奈湿地(P<0.05);Methanoregula在珰奈湿地底泥中的丰度高于龙凤湿地;冬季厌氧绳菌属(Anaerolinea)和甲烷八叠球菌属(Methanosarcina)在珰奈湿地底泥中的丰度显著高于龙凤湿地(P<0.05)。【结论】龙凤湿地与珰奈湿地的差异主要影响湿地底泥中参与元素循环的细菌和产甲烷古菌的丰度,人为干扰和低温会降低湿地中微生物的多样性,pH、盐分和碱性磷酸酶是显著影响微生物多样性的环境因素。     

潜流人工湿地中植物对氮磷净化影响效应的研究

采用潜流人工湿地系统,配制以NH⁺₄-N、NO^-₃-N和PO^3-₄-P为主要成分的模拟污水,通过间歇运行方式,考察了芦苇和小叶章的生长情况、生理生态学特性及其对污水中N、P净化效能的影响,并研究了植物对湿地系统pH变化、NO^-₃-N和NH⁺₄-N净化效率的影响。结果表明,当水力停留时间为7d时,小叶章和芦苇湿地对TN的去除率分别为65.1%和99.6%,去除负荷分别为1.66g · m^-3 · d^-1和2.53g · m^-3 · d^-1。小叶章和芦苇对去除TN的贡献率分别为14.7%、61.7%,对去除TP的贡献率分别为11.7%和12.9%;芦苇植株内N、P浓度分别为29.2mg/g和3.41mg/g。芦苇湿地的净化效能高于小叶章湿地。湿地系统中pH值先升高后降低的拐点可作为氨氧化反应结束的指示参数。     

Comparison of created and natural freshwater emergent wetlands in Connecticut (USA)

Five three- to four-year old created palustrine/emergent wetland sites were compared with five nearby natural wetlands of comparable size and type. Hydrologic, soil and vegetation data were compiled over a nearly two-year period (1988-90). Created sites, which were located along major highways, exhibited more open water, greater water depth, and greater fluctuation in water depth than natural wetlands. Typical wetland soils exhibiting mottling and organic accumulation were wanting in created sites as compared with natural sites. Typha latifolia (common cattail) was the characteristic emergent vegetation at created sites, whereas a more diverse mosaic of emergent wetland species was often associated with Typha at the natural sites. Species richness was slightly higher in created (22–45) vs. natural (20–39) wetlands, but the mean difference (33 vs. 30) was not significant. Nearly half (44%) of the 54 wetland taxa found at the various study sites were more frequently recorded at created than natural wetlands. The presence of mycorrhizae in roots of Typha angustifolia (narrow-leaved cattail) and Phragmites australis (common reed) was greater at created than natural wetlands, which may be related to differential nutrient availability. Wildlife use at all sites ranged from occasional to rare, with more sightings of different species in the natural (39) than created (29) wetlands. The presence of P. australis and introduced Lythrum salicaria (purple loosestrife) may pose a threat to future species richness at the created sites. One created site has permanent flow-through hydrology, and its vegetation and wildlife somewhat mimic a natural wetland; however, the presence of P. australis and its potential spread pose an uncertain future for this site. This study suggests the possibility of creating small palustrine/emergent wetlands having certain functions associated with natural wetlands, such as flood water storage, sediment accretion and wildlife habitat. It is premature to evaluate fully the outcome of these wetland creation efforts. A decade or more is needed, emphasizing the importance of long term monitoring and the need to establish demonstration areas.     

Trichloroethene and cis‐1,2‐dichloroethene concentration‐dependent toxicity model simulates anaerobic dechlorination at high concentrations. II: Continuous flow and attached growth reactors

A model that was used to describe toxicity from high concentrations of chlorinated aliphatic hydrocarbons (CAHs) on reductively dechlorinating cultures in batch reactors (Sabalowsky and Semprini (in press)) was extended here to simulate observations in continuous flow suspended and attached growth reactors. The reductively dechlorinating anaerobic Evanite subculture (EV‐cDCE) was fed trichloroethene (TCE) and excess electron donor to accumulate cis‐1,2‐dichloroethene (cDCE) in a continuous flow stirred tank reactor (CFSTR); and an attached growth recirculating packed column (RPC). A concentration‐dependent toxicity model used to simulate the results of batch reactors in part I (Sabalowsky and Semprini (in press) Biotechnol Bioeng) also simulated well the observations for the CFSTR and RPC growth modes. The toxicity model incorporates cDCE and TCE toxicity coefficients that directly increase the cell decay coefficient in proportion with cDCE and TCE concentrations. Simulated estimates of the cDCE and TCE toxicity coefficients indicate reductively dechlorinating cells are most sensitive to high concentrations of cDCE and TCE in batch‐fed growth, followed by CFSTR, with attached growth being least sensitive. The greater toxicity of TCE than cDCE, and ratio of the modeled toxicity coefficients, agrees with previously proposed models relating toxicity to partitioning in the cell wall (K_M/B), proportional to octanol‐water partitioning (K_OW) coefficients. Biotechnol. Bioeng. 2010;107: 540–549. © 2010 Wiley Periodicals, Inc.     

Illumina高通量测序揭示艾比湖湿地6种盐生植物根际土壤真菌群落组成及多样性

【目的】通过研究新疆艾比湖湿地不同盐生植物根际土壤真菌的多样性和群落结构,为艾比湖湿地退化恢复工作和真菌深入研究提供理论支持。【方法】利用高通量测序技术对真菌扩增子ITS1区进行测定,从而分析艾比湖湿地6种盐生植物根际土壤真菌群落多样性,并结合相关土壤理化因子分析环境与真菌群落多样性和丰富度的关联。【结果】艾比湖湿地6种盐生植物根际土壤真菌群落多样性及丰富度存在差异,碱蓬根际土壤真菌多样性最高,芦苇根际土壤真菌群落丰富度最高。真菌群落组成分析表明,土壤样品中真菌菌落主要隶属于子囊菌门(Ascomycota)和担子菌门(Basidiomycota),其中子囊菌门为主要优势菌门;链格孢霉属(Alternaria)是6种植物共有的优势菌属,但是其在不同植物之间的丰度存在差异,在戟叶鹅绒藤中的丰度最高,在准噶尔大戟中的丰度最低。pH与真菌多样性呈显著负相关,全磷(TP)与真菌群落丰富度呈显著正相关,pH、电导率(EC)和有机质(OM)对优势菌属的影响最大。【结论】艾比湖湿地6种盐生植物根际土壤真菌群落组成及多样性具有显著差异,碱蓬和芦苇根际土壤真菌的多样性和丰度高于其他植物,子囊菌门和链格孢霉...     

六种湿地植物根际氧化还原电位的日变化

在野外条件下,研究人工湿地植物根际氧化还原电位(ORP)随时间的变化及其与主要环境因子的关系。研究了美人蕉(Canna indica Linn.)、风车草(Cyperus flabelliformis Rottb.)、芦苇(Phragmites australis Trin.ex Steud.)、水鬼蕉(Hymenocallis littoralis(Jack.)Salisb.)、紫芋(Colocasia tonoimo Nakai.)和鸢尾(Iris tectorum Maxim.)6种植物在潜流人工湿地中的根际ORP及其日变化。6种湿地植物的根际ORP日变化曲线相似,均为双峰型,双峰值出现在11:00—14:00之间,最大值出现在14:00。各植物的根际ORP日变化基本在130—350 m V之间,以水鬼蕉的变幅最大,风车草和芦苇的变幅较小。不同植物的根际ORP有较大差异,风车草和紫芋的日平均值最大,显著高于鸢尾、美人蕉和水鬼蕉(P0.05);芦苇显著高于鸢尾和美人蕉(P0.05)。ORP与光照强度和气温呈正相关,尤与气温的正相关最为显著。ORP日平均值与植物生物量有显著的正相关性,尤与地下部分生物量相关性最显著。结果表明,人工湿地植物根际ORP因不同植物、一天中不同的时间有较大差异,后者与光照和气温等环境因子密切相关。     

Nutrient removal in constructed microcosm wetlands for treating polluted river water in northern China

River water pollution is increasingly widespread in northern China and can lead to problems with the drinking water for the residents if not properly treated. Constructed wetlands are a promising solution and have become increasingly popular in China. In this study the nutrient removal and plant uptake in constructed microcosm wetlands vegetated with Typha orientalis, Phragmites australis, Scirpus validus and Iris pseudacorus for treating simulated polluted river water in northern China were investigated. The performance of the treatment systems from April to November was assessed. The maximum TN, NH₄-N and TP removal efficiencies were 68%, 93% and 67%, respectively. And the maximum nutrient uptake by plants constituted 51.89% of the N removal and 34.17% of the P removal throughout the trial. S. validus and I. pseudacorus have a higher nutrient uptake capacity and are preferred species from a treatment perspective in constructed wetland in northern China.     

辽河口滨海湿地CH4排放特征及其影响因素

采用静态箱-气相色谱法,于2016年6—11月连续观测辽河口芦苇湿地、翅碱蓬湿地和裸滩湿地的CH_4排放速率,同时测定温度、氧化还原电位(Eh)、pH值和电导率(EC)等相关环境因子的动态变化。结果表明,3种类型湿地的CH_4排放具有明显的季节变化特征,均呈先上升后下降趋势。芦苇湿地、翅碱蓬湿地(涨潮前)和裸滩湿地(涨潮前)CH_4排放通量变化范围分别为0.447—10.40、0.045—0.509 mg m~(-2) h~(-1)和0.016—0.593 mg m~(-2) h~(-1),观测期内排放通量均值相应为(3.699±3.679)、(0.165±0.156) mg m~(-2) h~(-1)和(0.198±0.191) mg m~(-2) h~(-1),不同类型湿地之间差异显著(P0.01),芦苇湿地裸滩湿地(涨潮前)翅碱蓬湿地(涨潮前)。涨潮过程中,翅碱蓬湿地和裸滩湿地的排放速率分别变化在0.009—0.353 mg m~(-2) h~(-1)和0.018—0.335 mg m~(-2) h~(-1),观测期间其排放速率均值分别为(0.119±0.132) mg m~(-2) h~(-1)和(0.131±0.103) mg m~(-2) h~(-1),明显低于涨潮前(P0.01)。不同湿地类型间CH_4排放通量与电导率(EC)呈显著负相关(P0.01)。研究结果表明,潮汐和电导率均为影响辽河口不同类型湿地中CH_4排放的关键因子。     

A novel method for characterisation and quantification of plant root exudates

A microcosm unit is described which readily allows manipulation of experimental conditions to enable the subsequent impact on root exudation release to be monitored with time. Festuca ovina and Plantago lanceolata seedlings were grown in this microcosm unit over a 34 day experimental period under conditions of high (3.75 mol m^–3 N) or low (1.25 mol m^–3 N) nitrate-nitrogen treatment. At the end of the experimental period the seedlings in the microcosms were labelled with [¹⁴C]-CO₂ and the fate of the label within the plant and its release by the roots monitored. Total organic carbon (TOC) content of the collected exudate material was measured throughout the experimental period as well as during the ¹⁴C-chase period and comparison of plant C budgets using these two measurements is discussed. Nitrogen treatment as found to have a greater effect on exudate release by F. ovina than by P. lanceolata seedlings as indicated by both the total organic carbon and ¹⁴C results. The use and applications of the microcosm unit are discussed.     

蚯蚓对湿地植物光合特性及净化污水能力的影响

以香蒲、芦苇和美人蕉为研究对象,并以土壤+沙子+有机质混合物为供试基质模拟人工湿地处理污水,采用向基质中加入蚯蚓与未加入蚯蚓2种处理。研究加入蚯蚓后,香蒲、芦苇和美人蕉光合速率、蒸腾速率、SPAD值和水分蒸发、蒸腾量的变化及其对净化污水能力的影响。结果表明:与未加入蚯蚓相比,加入蚯蚓后,香蒲、芦苇和美人蕉的净光合速率、蒸腾速率、SPAD值和水分蒸发、蒸腾量均增加,其中芦苇的净光合速率、蒸腾速率和水分蒸发、蒸腾量增加达到显著水平(P <0.05),而香蒲的水分蒸发、蒸腾量增加也达到显著水平(P <0.05);加入蚯蚓后,香蒲、芦苇和美人蕉对COD_Mn、NH₄⁺-N、NO₃^--N、TN和TP的去除率均增加,且香蒲和芦苇对COD_Mn的去除率显著增加 (P <0.05)。加入蚯蚓后,香蒲、芦苇和美人蕉的SPAD值均增加,说明蚯蚓能提高湿地植物对氮的吸收,增加植株中的氮含量,促进湿地植物的光合速率和蒸腾速率从而提高对污水的净化能力。     

Constructed Wetlands as Green Tools for Management of Boron Mine Wastewater

Constructed wetlands are of increasing interest worldwide given that they represent an eco-technological solution to many environmental problems such as wastewater treatment. Turkey possesses approximately 70% of the world's total boron (B) reserves, and B contamination occurs in both natural and cultivated sites throughout Turkey, particularly in the north-west of the country. This study analyzes B removal and plant uptake of B in pilot plots of subsurface horizontal-flow constructed wetlands. Constructed wetlands were vegetated with Typha latifolia (referred to as CW₁) and Phragmites australis (referred to as CW₂) to treat wastewater from a borax reserve in Turkey-the largest of its type in the world and were assessed under field conditions. The B concentrations of water inflows to the systems were determined to be 10.2, 28.2, 84.6, 232.3, 716.4, and 2019.1 mg l^?1. The T. latifolia in the CW₁treatment group absorbed a total of 1300 mg kg^?1 B, whereas P. australis absorbed 839 mg kg^?1. As a result, CW₁had an average removal efficiency of 40.7%, while that of CW₂was 27.2%. Our results suggest that constructed wetlands are an effective, economic and eco-friendly solution to treating B mine wastewater and controlling the adverse environmental effects of B mining.     

江苏滨海湿地芦苇和互花米草光合特性对模拟增温的响应

滨海湿地生态系统具有较高的初级生产力,是地球生态系统主要的碳库之一。然而,气候变暖和外来物种入侵通过改变植物光合特征性能使这一碳库的稳定性存在诸多的不确定性。利用在江苏盐城芦苇湿地和互花米草湿地建设的两个增温观测站,采用便携式光合荧光测量系统研究了本土植物芦苇（Phragmites australis）和入侵物种互花米草（Spartina alterniflora）光合特性对模拟增温的响应特征和机制。光合作用日调查变化曲线显示,增温使芦苇的净光合速率（P_n）、气孔导度（G_s）、蒸腾速率（T_r）和水分利用效率（WUE）都发生了显著的下降,但互花米草的各同名参数却表现出相反的变化特征,表明增温使互花米草的生理机能增强,促进了光合作用;根据P_n和胞间CO₂浓度（C_i）的变化趋势推断互花米草和芦苇光合速率变化均为非气孔限制因素驱动。利用直角双曲线修正模型拟合的光响应曲线结果显示,芦苇增温组的光响应曲线位于对照组下方,互花米草增温组的光响应曲线位于对照组上方;增温降低了所研究植物的光补偿点（LCP）,表明增温可提高两种植物利用弱光的能力;增温增加了互花米草光补偿点（LCP）和光饱和点（LSP）间值域范围,从而揭示了增温可有效提高互花米草利用光合有效辐射的能力;增温降低了芦苇的暗呼吸速率（R_d）,芦苇受到增温的胁迫,在减缓新陈代谢的同时也减弱了光合作用,而互花米草表现出相反特征。由此推测增温条件下入侵植物互花米草同化大气CO₂的能力（即碳汇能力）优于本土植物芦苇,这也是互花米草成为入侵物种的主要原因之一。     

艾比湖湿地盐节木土壤固氮微生物群落结构和丰度的环境异质性特点

【背景】新疆艾比湖湿地国家自然保护区作为国内最典型的温带干旱区湿地荒漠生态系统,对于富集生物多样性、平衡生态环境等方面存在着非凡的意义。目前关于艾比湖湿地根际与非根际土壤固氮微生物群落结构和丰度的相关研究还未见报道。【目的】通过分析新疆艾比湖湿地盐节木根际和非根际土壤固氮菌nifH基因的群落结构和丰度的环境异质性特点,及探讨微生物群落对国内极端干旱区脆弱敏感的艾比湖湿地生态系统循环过程中的作用,为改善荒漠化的艾比湖湿地环境提供理论依据。【方法】采用构建克隆文库和q-PCR的方法,并利用冗余分析法(Redundant analysis,RDA)探究土壤理化性质与固氮微生物群落结构及丰度的相关性。【结果】艾比湖湿地盐节木非根际土壤中nifH的多样性高于根际土壤,盐节木根际土壤的nifH序列优势种属主要为固氮根瘤菌属(Azorhizobium)和脱硫弧菌属(Desulfovibrio);非根际土壤的nifH序列优势种属主要是固氮弧菌属(Azoarcus)、太阳杆菌属(Heliobacteriummodesticaldum)和脱硫弧菌属(Desulfovibrio)。盐节木根际土壤nifH数量为4.08×104copies/g,盐节木非根际土壤中nifH的数量为5.52×103copies/g,根际土壤nifH的丰度高于非根际土壤。相关性分析显示,根际土壤的优势类群和丰度与硝态氮(NO3--N)、速效氮、总钾、含水量等因子显著相关,非根际土壤的优势类群和丰度与硝态氮(NO3--N)、速效氮、总磷、总钾、总氮呈显著相关。【结论】在盐节木根际土壤中nifH的丰度高于非根际土壤,而多样性则低于非根际土壤,而且硝态氮(NO3--N)、速效氮、总磷可能会影响固氮微生物的群落结构和丰度,这些特点为湖泊湿地的退化恢复提供理论和数据基础。     

Chloroethene Biodegradation in Sediments at 4°C

Microbial reductive dechlorination of [1,2-¹⁴C]trichloroethene to [¹⁴C]cis-dichloroethene and [¹⁴C]vinyl chloride was observed at 4°C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-¹⁴C]cis-dichloroethene and [1,2-¹⁴C]vinyl chloride to ¹⁴CO₂ also was observed under these conditions.