山药连作对土壤微生物群落及土壤酶活性的影响

以山药连作（0 a,1 a,2 a）和轮作（山药—小麦）土壤为研究对象,探讨耕作模式对山药种植地耕层土壤（0—30 cm）微生物数量和酶活性的影响。结果表明:土壤耕层的有机质、全氮、有效磷和速效钾含量随山药连作年限的延长而逐渐降低,而山药—小麦轮作模式则有助于恢复地力。山药连作、轮作的土壤均以细菌所占比例最大,放线菌次之,真菌最少;与对照（0 a）相比,细菌、放线菌数量均随着山药连作年限增加呈递减趋势;但放线菌的降幅明显大于细菌,表现出对连作年限更强的敏感性;真菌数量随连作年限呈先升后降的趋势。山药连作可以明显降低土壤脲酶、碱性磷酸酶和蔗糖酶的活性,轮作模式则可以激发该三种酶的活性,其中轮作较连作2 a的处理可以明显提高脲酶和蔗糖酶活性,差异分别达显著水平（p < 0.05）和极显著水平（p < 0.01）。说明山药连作会破坏土壤耕层微生物种群结构,并抑制土壤酶活性,轮作可以在一定程度上改善土壤微生物群落结构及酶活性质量。     

轮作与连作对烟田土壤微生物区系及多样性的影响

为探讨轮作与连作对烟田根际土壤微生物群落的影响,采用实验室微生物培养联合微生物高通量测序技术,分析了玉米-烤烟轮作和烟叶连作对烟株根际土壤微生物数量、群落结构及其多样性的影响。研究结果表明,轮作烟田根际土壤中可培养细菌和放线菌数量均高于连作烟田根际土壤,但真菌数量低于连作烟田。土壤高通量测序结果表明,轮作烟田根际土壤真菌和细菌群落多样性均高于连作烟田;在烟株的生长过程中,轮作和连作烟田在旺长期和成熟期微生物群落相似度降低。相较于黑胫病/根腐病/根结线虫发病率较高(36. 67%)的连作烟田来说,轮作烟田发病率较低(0%),进一步分析真菌和细菌群落结构发现,轮作烟田根际土壤中拮抗菌如Sphingomonas (鞘脂单胞菌属)、Pseudomonas (假单胞菌属)、Aspergillus (曲霉属)等相对丰度均高于连作烟田,而连作烟田根腐病病菌Pythium (腐霉属)丰度较高。     

西藏中部农田土壤复退过程中的生物学特征

在西藏中部春播条件下,就不同培肥方式对土壤剖面微生物区系及其主要生理类群变化的影响,以及土壤微生物与土壤有机质、土壤养分的相互关系进行了研究。结果表明,细菌、放线菌、纤维素分解菌的土体差异较大,并主要集中于耕层;真菌、固氮菌的土体差异则极小。2～30,31～60cm土层土壤细菌在微生物区系构成中均占绝对优势,化肥对调控土壤细菌数量具有重要作用。不同培肥方式对2～30,31～60cm土层土壤真菌、固氮菌以及2～30cm土层土壤放线菌的繁殖普遍具有不同程度的抑制作用;2～30,31～60cm土层固氮菌与纤维素分解菌均呈负相关。土壤微生物与土壤有机质的相互促进作用较为明显,对提高土壤有效氮、有效磷亦具重要作用。     

放牧对荒漠草原土壤微生物的影响及其季节动态研究

研究了内蒙古荒漠草原不同放牧强度下土壤中微生物数量和养分含量的变化及其季节动态变化。结果表明,草原土壤中各类群微生物数量关系是细菌>自生固氮菌>放线菌>真菌,垂直分布为0~10 cm>10~20 cm土层;土壤微生物和养分含量随季节变化有着明显的变化,但各类群变化规律并不完全相同;与围栏相比,土壤中微生物总数量、细菌、真菌、放线菌和养分含量在轻牧区增加,重牧区降低。自生固氮菌数量在放牧区均增加。     

封育年限对伊犁绢蒿荒漠土壤微生物及酶活性的影响

[目的]揭示封育条件下土壤微生物及其土壤酶活性的适应机制,为退化草地恢复提供科学依据。[方法]采用蛇形布点法,采集封育0,3及11a伊犁绢蒿荒漠0—5,5—10,10—20cm土壤样品;采用常规方法对土壤有机质、过氧化氢酶活性、脲酶活性及土壤微生物数量进行测定。[结果]随封育年限增加,0—5cm土层有机质含量呈增加趋势,且封育11a较对照显著提高14.2%。土壤微生物组成中细菌数量最多,占绝对优势,放线菌次之,真菌最少。0—5cm土层细菌、真菌数量随封育年限增加呈降低趋势,放线菌数量呈增加趋势,至封育11a细菌、真菌较对照依次显著降低(47.3%,25.5%),而放线菌则显著增加(15.5%);5—20cm土层细菌数量变化不显著,而放线菌及真菌数量多呈增加趋势。封育对伊犁绢蒿荒漠0—20cm土层过氧化氢酶活性影响不显著,而0—10cm土层脲酶活性随封育年限增加呈增加趋势,10—20cm土层则呈降低趋势。[结论]长期封育有利于土壤有机质的积累,促进表层土壤放线菌数量及脲酶活性的增加。     

烤烟连作对耕层土壤酶活性及微生物区系的影响

以烤烟品种"龙江911"为材料,在大田试验条件下分别测定了连作1年和5年的烤烟耕层土壤酶活性及微生物区系变化。结果表明:烤烟连作1年的耕层土壤酸性磷酸酶与脲酶活性高于正茬(大豆-小麦-烤烟),而烤烟连作5年的土壤酸性磷酸酶与脲酶活性低于连作1年。在0~10 cm土层内,烤烟连作1年和连作5年的土壤过氧化氢酶活性均比正茬低,且连作5年土壤比连作1年土壤降低了35.47%。10~20 cm土层内,烤烟连作1年和5年的土壤蔗糖酶活性分别比正茬降低了30.27%和52.14%。烤烟连作减少了土壤细菌和放线菌数量,增加了真菌数量,细菌主要以土壤氨化细菌、好气性自生固氮菌和好气性纤维素分解菌降低为主。因此,烤烟连作破坏了微生物种群的平衡及降低土壤酶活性可能是引起烤烟连作障碍的主要原因之一。     

长期不同种植模式对东北黑土微生物群落结构与土壤理化性质的影响

利用长期定位试验资料,评价了东北黑土增施有机肥条件下玉米连作(CMC)、玉米-大豆轮作(MSR)和大豆连作(CSC)等种植模式对土壤微生物数量与结构、土壤理化性质的影响及其相互关系。结果表明:0~40 cm土层内,土壤微生物总量呈CMCMSRCSC趋势,且差异显著(P0.05);细菌数量占微生物总量的比重呈CMCMSRCSC的趋势,而真菌和放线菌所占比重均呈CSCMSRCMC的相反趋势;CMS处理下的土壤容重最低,但土壤有机碳、全氮、有效氮、有效磷含量均显著高于其他处理;相关分析发现细菌和放线菌数量与土壤容重显著负相关,但与土壤有机碳、全氮、有效氮显著正相关,而真菌数量占微生物总量的比例则与土壤容重显著正相关,与土壤有机碳、全氮、有效氮显著负相关。综上所述,长期玉米连作结合有机肥施用,有利于改善土壤理化性状,增加土壤微生物数量,但以细菌增加为主,微生物多样性呈下降的趋势。     

高寒草地不同退化程度下土壤微生物及土壤酶活性变化特征

为探讨不同退化程度对高寒草地土壤微生物及土壤酶活性的影响,以青藏高原东北缘祁连山3种不同退化程度(轻度退化、中度退化、重度退化)高寒草地为研究对象,测定和分析土壤3大类微生物(细菌、真菌、放线菌)和氮素生理群(氨化细菌、好气性固氮菌、嫌气固氮菌、硝化细菌、反硝化细菌)数量、微生物量(碳、氮)及土壤酶活性(蔗糖酶、脲酶、磷酸酶、过氧化氢酶)变化特征。结果表明:(1)相同土层不同退化程度,土壤3大类微生物数量、氮素生理群、微生物量以及土壤酶活性随退化程度的加重总体呈减小的趋势,重度退化程度下各指标含量最小,中等退化程度可增加10—20cm土壤放线菌、氨化细菌及反硝化细菌数量和20—30cm土壤细菌、真菌、放线菌、好气性固氮菌、反硝化细菌数量;(2)不同土层相同退化程度,土壤3大类微生物数量、氮素生理群、微生物量以及土壤酶活性随土层深度的加深均逐渐减小。研究结果对评价草地退化程度提供了新思路,同时为高寒草地的恢复和重建提供了重要的理论依据。     

连续5年施菜籽饼肥和稻草覆盖对茶园土壤生态系统的影响

在长沙县百里茶廊连续进行5年的定位试验,研究施菜籽饼肥结合稻草覆盖对丘陵茶园土壤生态系统的影响。结果表明,施菜籽饼肥加稻草覆盖处理(TI)茶园土壤pH、有机质含量、全氮含量、有效磷含量均显著高于纯施化肥处理(T3),0～40cm土层土壤容重显著低于T3处理,0～60cm土层土壤水分含量、0～20cm土层蚯蚓数量和生物量、氨基化细菌、好气性自生固氮菌、嫌气性自生固氮菌、放线菌、真菌和细菌等微生物数量均显著高于T3处理。施菜籽饼肥结合稻草覆盖可显著改善丘陵茶园土壤生态功能,菜籽饼化肥配施结合稻草覆盖(T2)也一定程度改善了土壤生态系统,长期不施肥使茶园土壤养分贮存量全面下降。     

长期轮作与施肥对土壤主要微生物类群的影响

根据长期田间试验,对施肥、作物、种植方式等对土壤细菌、真菌与放线菌含量的影响进行分析.结果显示施肥,特别是施有机肥明显提高土壤微生物数量,玉米、苜蓿与冬小麦连作不同施肥土壤细菌数量相对休闲地变幅在-197.04×105～+187.07×105个/g土,真菌在-6.08×103～+36.57×103个/g土,放线菌在-47.21×104～+301.4×104个/g土.轮作系统不同施肥处理真菌与放线菌数量高于休闲地.在施氮磷化肥条件下不同作物轮作,苜蓿与糜子对细菌有相对抑制作用,对真菌与放线菌有促进作用,红豆草抑制放线菌促进细菌,豌豆对三类微生物均有抑制作用.     

Physical Properties of the Soils of Sibay City of the Republic of Bashkortostan

Eurasian Soil Science - The results of the study of the properties of urban soils of the city of Sibay located in the mining region of the Republic of Bashkortostan are presented. A specific...     

食用仙人掌萎蔫气象条件分析

塑料大棚内种植的食用仙人掌在土壤墒情较好时也有萎蔫现象发生，通过试验观测和对仙人掌生理习性的分析，发现阴雨过后天气突然放晴温度急剧上升易使仙人掌发生萎蔫现象，并提出了田间管理的应对措施。     

Heterogeneity of Organic Matter of Aggregates of Protocalcic Chernozems

Eurasian Soil Science - Layers were step-by-step removed from macroaggregates (2–1 mm in diameter) of Protocalcic Chernozems via successive abrasion in a revolving rotator during 5, 10, 15,...     

青海省耕地资源开发利用分析及对策研究

分析论述了青海省耕地资源开发利用的现状、特点和问题。在此基础上,提出了对青海省耕地资源进行研究的框架体系和思路,同时基于GIS/RS技术设计了相关的技术路线。最后依据所做设计对青海省耕地资源开发利用做了初步分析,并进行了相关的对策研究分析。     

Characterization of physical and chemical properties of Varzea soils of Goias State of Brazil

Abstract

Brazil has approximately 30 million hectares of lowland areas, known locally as “Varzea,”; distributed throughout the country. Soils in these areas have the potential to support agricultural production, but very little is known about their fertility. The current experiment was undertaken to characterize the chemical and physical properties of representative “Varzea”; soils collected at 0–20, 20–40, 40–60, and 60–80 cm depth intervals from 23 sites in Goias State of Brazil. Organic matter contents averaged 42 g/kg in the surface 20 cm of soil and should make a significant contribution to overall nutrient availability. Soil pH increased slightly with depth from a mean value of 5.2 in the surface 20 cm of soil to a mean value of 5.4 in the 60–80 cm depth interval. Several soils had exchangeable Al values ≥ 1.0 cmol Al/kg, but soil Al saturation was generally less than the 60% level frequently associated with Al toxicity. However, cereal and legume production could benefit from lime addition in many of these soils. Although base saturation was fairly low in some soils, exchangeable Ca and Mg levels were, in general, adequate throughout the profile. Extractable P levels were adequate in most surface soil samples. Extractable K levels in these soils were generally low, and the application of K fertilizers should be beneficial, especially in conjunction with lime addition. The high clay content “Varzea”; soils of the Brazilian lowlands have some drainage problems but generally exhibit favorable chemical properties for crop production when compared to soils of the well‐drained Cerrados.     

Estimation of potential nitrogen-fixing activity of agrophytocenoses soils of the subtropical zone of Russia

An estimation of potential nitrogen-fixing activity of various soil types under agrophytocenoses of tea, filbert, peach, and pawpaw which grow in the area of Greater Sochi is given. High indicators of nitrogen fixation activity in the soil in the course of vegetation were characteristic of agrocenoses of pawpaw, peach, and filbert. The lowest level of nitrogen fixation was noted in the soil of a tea plantation. A negative correlation dependence of potential nitrogen-fixing activity on the acidity of the soil solution was established. A study of the seasonal dynamics of the activity of nitrogen fixation of soils of agrocenoses of the subtropical zone of Russia made it possible to distinguish a less active winter and more active spring-summer-autumn periods.     

Kinetics of Popping of Popcorn

The rate of popping of popcorn was measured in oil and in air. Kinetic data for lifetimes of individual kernels from a large population were obtained in oil at six constant temperatures (180–250°C) and also in an air‐popper at 202°C. The data are characterized by an induction period, which is, significantly, followed by a first‐order decrease in the number of unpopped kernels versus time. The activation energy for the first order process is 166.7 kJ/mol between 180 and 210°C, and 53.8 kJ/mol between 210 and 250°C. These data are consistent with a model that assumes 1) that the rate of heat transfer into a kernel follows Newton's law of cooling; 2) that in a sample of kernels there exists a distribution of critical pressures; 3) that for an individual kernel, the probability of popping is directly proportional to the difference between the internal aqueous vapor pressure and the kernel's critical pressure; and 4) that the measured rate constant at any temperature is an average overall of the kernels in the sample with critical pressures equal to or less than the internal aqueous vapor pressure. Minimum popping temperatures predicted by the model are 181 ± 2°C (oil) and 187 ± 2°C (air), in good agreement with previously reported direct measurements.     

物联网安全及解决措施

物联网是一个集信息通信、数据交换、传感器技术与软件工程于一体的综合性产业,探讨和分析了物联网的结构体系与发展中遇到的安全问题。     

荔枝种子结构的扫描电镜观察

荔枝种子从果实中剥离出来后, 即使在室内条件下, 也极易失水干缩, 潮湿环境中又易发霉而腐烂。扫描电镜观察表明: 种皮上布满纹孔, 水分散失面积很大; 种脐部为疏松的海绵组织, 且营养丰富。据此, 生产上应对种子彻底清洗, 并保存于适当湿度的环境中, 以提高其发芽率。     

Towards bioremediation of toxic unresolved complex mixtures of hydrocarbons: identification of bacteria capable of rapid degradation of alkyltetralins

Background, aim and scope  Unresolved complex mixtures (UCMs) of aromatic hydrocarbons are widespread, but often overlooked, environmental contaminants. Since UCMs are generally rather resistant to bacterial degradation, bioremediation of UCM-contaminated sites by bacteria is a challenging goal. Branched chain alkyltetralins are amongst the individual classes of components of aromatic UCMs which have been identified in hydrocarbon-contaminated sediments and a number of synthetic alkyltetralins have proved toxic in laboratory studies. Thus, alkyltetralins should perhaps be amongst the targets for UCM bioremediation strategies. The slow degradation of several alkyltetralins by a microbial consortium has been reported previously; however, the bacteria involved remain unidentified and no single strain capable of alkyltetralin biodegradation has been isolated. The present project therefore aimed to enrich and identify bacterial consortia and single strains of bacteria from a naturally hydrocarbon-contaminated site (Whitley Bay, UK), which were capable of the degradation of two synthetic alkyltetralins (6-cyclohexyltetralin (CHT) and 1-(3’-methylbutyl)-7-cyclohexyltetralin (MBCHT)). Materials and methods  Bacteria were enriched from sediment collected from Whitley Bay, UK by culturing with CHT and MBCHT for a period of 4 months. Biodegradation experiments were then established and degradation of model compounds monitored by gas chromatography–mass spectrometry. Internal standards allowed the generation of quantitative data. 16S rRNA gene clone libraries were constructed from individual enrichments to allow assessment of microbial community structure. Selective media containing MBCHT were used to isolate single bacterial strains. These strains were then tested in liquid culture for their ability to degrade MBCHT. Results  The consortia obtained through enrichment culture were able to degrade 87% of CHT and 76% of MBCHT after only 46 days compared with abiotic controls. The 16S ribosomal RNA gene clone libraries of these bacteria were dominated by sequences of Rhodococcus spp. Using selective media, a strain of Rhodococcus was then isolated that was also able to biodegrade 63% of MBCHT in only 21 days. Discussion  The present report describes the isolation of a single bacterial strain able to degrade the resistant MBCHT. Although significant losses of MBCHT were observed, putative metabolites were not detectable. Rhodococcus sp. have been reported previously to be able to biodegrade a range of hydrocarbon compounds. Recommendations and perspectives  Due to their environmental persistence and toxicity, aromatic UCMs require bioremediation. The culturing and identification of such bacteria capable of rapid degradation of alkyltetralins may be an important step toward the development of bioremediation strategies for sites contaminated with toxic UCMs.