首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 593 毫秒
1.
复合菌剂防控香蕉枯萎病的效果及其微生物学机制   总被引：3，自引：0，他引：3  
由病原菌尖孢镰刀菌古巴专化型(Fusarium oxysporum f. sp. cubense(Foc))侵染引起的香蕉枯萎病对全世界香蕉产业带来了毁灭性的影响,且目前尚无广泛采用的防治方法。研究复合生防真菌制剂对香蕉枯萎病的防治效果,以期为大田香蕉枯萎病的防治提供依据。设置3组不同的菌剂处理,分别为对照组CK、复合菌剂NFP、复合菌剂NFPT,通过两季的盆栽试验,研究复合菌剂对香蕉枯萎病的防治效果及其对土壤微生物多样性的影响;利用IlluminaMiseq高通量测序平台对细菌16S rRNA基因和真菌ITS区域进行测序分析,采用实时荧光qPCR定量分析各处理病原菌的数量。结果表明:(1)复合菌剂处理(NFP和NFPT)对香蕉枯萎病有较好的防治效果,其防效分别为43%和48%。(2)施用复合菌剂增加了细菌和真菌群落丰富度和多样性。基于Bray-curtis距离矩阵的主坐标分析(PCoA)结果表明NFP和NFPT改变了细菌和真菌群落结构。NFP和NFPT处理增加了潜在有益微生物中与香蕉枯萎病病情指数呈显著负相关的大理石雕菌属Marmoricola、类诺卡氏菌属Nocardioides、野野村式菌属Nonomuraea、norank_c__Acidobacteria、DS-100属和norank_f__Blastocatellaceae__Subgroup_4属的相对丰度,显著减少了病原菌尖孢镰刀菌的数量,重塑了土壤微生物结构和功能,增强其抗病性。  相似文献   

2.
香蕉枯萎病由病原真菌尖孢镰刀菌4号生理小种引起,其根际微生物组是抵御病原菌入侵的关键屏障。根际原生动物群落在根际微生物群落调控以及植物健康方面有不可忽视的作用。利用Illumina MiSeq高通量测序技术分析连作蕉园中植株发病前后根际土壤原生动物群落特征变化以及其与病原菌的相互关系。结果表明：相较于可培养细菌与真菌,原生动物的数量对病原菌的种群数量变化的影响更大;根际原生动物的群落多样性与丰富度都随植株生长而降低,且在发病植株中更低;抽蕾前后的健康与发病植株中根际原生动物群落结构存在显著差异;总体而言,吞噬型原生动物的相对丰度显著高于其他功能类型的原生动物,且在健康与发病植株中差异显著;吞噬型原生动物中与病原菌具有显著相关性的多为丝足虫门;在抽蕾期的健康植株中,丝足虫门的高丰度属中Group-Te与Cercomonas属与病原菌呈显著负相关;在抽蕾期的患病植株中,相对丰度较高的植物致病型原生动物Pythium属与病原菌呈显著正相关。综上所述,根际土壤中原生动物对病原菌的影响较大,在植株生长过程中,原生动物的群落特征发生改变,且在发病与健康植株中存在差异。与病原菌具有显著负相关的吞噬型原生动物,尤其是丝足虫门的部分高丰度属,可能会在防控香蕉枯萎病上产生一定潜力。  相似文献   

3.
香蕉枯萎病是由尖孢镰刀菌古巴专化型[Fusarium oxysporum f.sp.cubense]侵染引起维管束坏死的一种毁灭性真菌病害,是世界范围内分布最广、毁灭性最强的植物病害之一。我们在古籍《广东新语》找到有关香蕉-甘蔗轮作的记载,经大田试验证明,连作蕉地轮作甘蔗2年后,后茬香蕉枯萎病发病率大幅下降至1.79%。在本研究中,我们试图探明连作蕉地轮作甘蔗,后茬香蕉的持续抑病效果及其机理。连作蕉地轮作甘蔗2年后,测定回种不同年限香蕉枯萎病发病率和土壤可培养微生物数量,并通过高通量测序技术分析土壤细菌微生物群落结构和组成的变化。结果表明：连作蕉地轮作甘蔗2年后,甘蔗地后茬香蕉枯萎病发病率仅为1.79%,后续3年发病率逐年递增,分别为21.93%、25.80%和28.81%,但均低于多年连作蕉地的平均发病率（49.15%）。土壤放线菌和尖孢镰刀菌总数随香蕉种植年限增加而显著增加。高通量测序结果表明,酸杆菌门（32.86%）、变形菌门（28.85%）和绿弯菌门（12.33%）3个菌门为香蕉-甘蔗轮作系统香蕉根围土细菌的优势菌门。酸杆菌目（Acidobacteriales）细菌相对丰度随回种香蕉逐年增加,并与香蕉枯萎病发病率呈显著正相关的关系;而假单胞菌目（Pseudomonadales）、浮霉菌目（Planctomycetales）、球杆菌目（Sphaerobacterales）、乳酸杆菌目（Lactobacillales）和土壤红杆菌目（Solirubrobacterales）细菌随香蕉回种年限的增加呈下降趋势,并与香蕉枯萎病发病率呈显著负相关的关系。连作蕉地轮作甘蔗2年后,4年内仍能保持较好的抑病效果。本模式具有轮作时间短、抑病效果好、持续时间长、经济效益高等特点。  相似文献   

4.
近年来,珠三角部分蕉农采用香蕉和甘蔗轮作防控香蕉枯萎病,并取得一定成效,我国古籍《广东新语》也有香蕉-甘蔗轮作的记载,但是关于该轮作模式的作用、效果及控病机理尚不明确。本文研究了连作香蕉地轮作不同年限甘蔗对香蕉枯萎病的控制作用,并从土壤微生态角度探讨其作用机理。试验设置4个处理：连作香蕉11年（CK）、香蕉连作地-甘蔗1年-香蕉1年（GZ1）、香蕉连作地-甘蔗2年-香蕉1年（GZ2）和香蕉连作地-甘蔗3年-香蕉1年（GZ3）。研究轮作甘蔗不同年限对后茬香蕉枯萎病发病率的影响,同时通过测定土壤可培养微生物数量,并利用高通量测序技术分析土壤微生物结构,揭示轮作甘蔗影响后茬香蕉枯萎病发生的土壤微生态机制。结果表明,连作蕉地香蕉枯萎病发病率为49.15%,而轮作甘蔗1年后茬香蕉枯萎病发病率降至17.86%,轮作2年和3年甘蔗后茬香蕉枯萎病发病率仅为1.79%。土壤可培养细菌总数随着轮作甘蔗年限的增加而显著增加,可培养放线菌总数和尖孢镰刀菌则呈逐渐减少的趋势,真菌总数无显著变化。土壤细菌多样性指数随轮作甘蔗年限的增加而降低。假单胞菌目（Pseudomonadales）、浮霉菌目（Planctomycetales）、酸微菌目（Acidimicrobiales）和土壤红杆菌目（Solirubrobacterales）的细菌丰度呈随甘蔗种植年限增加而逐年增加的趋势,并与香蕉枯萎病发病率呈显著负相关关系。酸杆菌目（Acidobacteriales）、红螺菌目（Rhodospirillales）和军团菌目（Legionellales）的细菌丰度则呈随甘蔗种植年限逐年降低趋势,并与香蕉枯萎病发病率呈显著正相关。连作香蕉地轮作甘蔗,能够显著降低后茬香蕉枯萎病的发病率,并且随着甘蔗轮作时间年限的增加,发病率逐年降低。轮作甘蔗通过改变土壤微生物群落结构而间接影响尖孢镰刀菌的生存环境,从而降低香蕉枯萎病发病率,轮作2年甘蔗,即可达到显著控病效果。此结果与《广东新语》中关于香蕉-甘蔗轮作年限的记载一致。  相似文献   

5.
硝/铵营养对香蕉枯萎病尖孢镰刀菌生长的影响   总被引：2，自引：2，他引：0  
通过室内平板培养,研究了不同硝/铵配比的氮源,以及不同的pH对香蕉枯萎病尖孢镰刀菌生长的影响。结果表明: 1）在所有不同硝/铵配比处理中,低pH（pH=4）均抑制尖孢镰刀菌的生长。在相同pH值条件下,100%铵态氮处理中尖孢镰刀菌的生长受到明显抑制,其菌落直径均小于4 cm; 2）在不同浓度铵处理后,尖孢镰刀菌的生长在铵态氮大于5 mmol/L时受到强烈的抑制; 3）通过模拟植物细胞壁被尖孢镰刀菌侵染并穿透的过程中发现,尖孢镰刀菌在100%铵态氮处理下不能穿透赛璐膜。本研究结果说明,铵态氮能够控制香蕉尖孢镰刀菌的生长,并抑制其侵染穿透寄主细胞壁。  相似文献   

6.
为了研究微生物菌剂对连作地块草莓（Fragaria×ananassa Duch.）生长和土壤性状的影响，设置3个处理：不施用微生物菌剂（CK）、施用单一微生物菌剂（T1）和施用复合微生物菌剂（T2），统计草莓存活率和产量，并测定土壤样品的理化性状和微生物群落结构变化。结果表明，微生物菌剂处理有助于草莓的生长和增产。与CK相比，T1、T2的草莓存活率分别提高17.99和25.19个百分点，草莓产量分别增加30.16%和41.79%。微生物菌剂处理有效改善了土壤养分。与CK相比，T2土壤有效磷和速效钾含量显著提高18.31%和55.27%。然而，微生物菌剂处理提高了土壤电导率并降低了土壤pH值，长期施用微生物菌剂存在土壤盐渍化和酸化的风险。微生物群落结构分析结果表明，草莓土壤中细菌和真菌的优势菌门分别为厚壁菌门和子囊菌门，优势菌属分别为芽孢杆菌属和曲霉属。微生物菌剂施用提高了土壤真菌群落的丰富度和多样性，但对土壤细菌群落影响较小。与CK相比，微生物菌剂处理增加了芽孢杆菌属、根霉属和假霉样真菌属的相对丰度，其中根霉属和假霉样真菌属相对丰度在T2达到显著水平；降低了鞘氨醇单胞菌属、曲霉属和青霉...  相似文献   

7.
对天津周边半干旱地区不同种植年限的菜田土壤微生物状况调查研究表明 ,该地区土壤微生物以细菌为主 ,夏季微生物总量大大高于冬季 ;随着种菜年限的增加 ,耕层和亚耕层微生物总量都有增加趋势 ,其中细菌和放线菌增加明显 ,真菌有下降趋势 ;真菌类群分析表明 ,少数纤维素分解菌 ,如青霉 (Penicillium)、木霉 (Trichoderma)等为优势菌 ,而糖和木质素分解菌仅占少数。用尖孢镰刀霉 (Fusariumuoxysporum)、大肠杆菌 (Escherichia coli)接种不同种菜年限土壤 ,检测土壤拮抗菌状况发现 ,拮抗菌仅在种植年限长的老菜田的放线菌中发现。表明北方半干旱地区菜田土壤细菌为优势菌 ,主要存在于土壤微孔隙中 ;而适于生活在土壤疏松大孔隙中的真菌数量极少。应注意土壤结构的改良 ,为丰富土壤微生物提供良好的生态环境  相似文献   

8.
碱性肥料对香蕉枯萎病发生及土壤微生物群落的影响   总被引：3，自引：1，他引：2  
【目的】针对我国香蕉主产区蕉园土壤酸化、 微生物环境恶化,香蕉枯萎病严重泛滥和肆虐,严重威胁产业等问题,通过施用碱性肥料改善蕉园土壤酸性及微生物环境,从而降低香蕉枯萎病发病率,促进香蕉健康生长。【方法】以重病区蕉园土壤为对象,采用盆栽试验,研究碱性肥料对土壤微生物及香蕉枯萎病发生情况的影响。试验设碱性肥料(AF)和常规肥料(CCF)2种肥料处理,每种肥料设低量(L1)、 中量(L2)和高量(L3)3个施肥量,同一施肥量处理的氮、 磷、 钾总用量相等。于2013年3月6日移栽香蕉苗到营养钵, 130 d后待各处理香蕉发病明显时采集土壤及植株样品进行各项指标测定。【结果】 1)施碱性肥料能显著降低香蕉枯萎病的发病率,常规肥料处理的香蕉发病率为78%,而碱性肥料处理的仅为33%。2)碱性肥料对土壤微生物群落有明显的影响,土壤中的真菌数量AF处理明显少于CCF处理,而细菌、 放线菌数量则显著高于CCF处理,因此AF处理土壤的香蕉尖孢镰刀菌明显减少。3)试验期间碱性肥料能显著提高土壤pH值,较常规肥料处理提高了0.75个pH单位,而土壤EC值比常规肥料处理低47.76 μS/cm。4)土壤pH值与土壤中古巴专化型尖孢镰刀菌(FOC)的数量及香蕉发病率呈显著负相关; 细菌数量与FOC数量、 香蕉枯萎病发病率、 病情指数之间呈显著的负相关; 土壤中FOC和真菌数量与香蕉发病率呈显著正相关。5)香蕉生物量随着碱性肥料和常规肥料用量的增大而增加,但碱性肥料的效果更加明显。【结论】应用碱性肥料不仅可以为香蕉提供氮、 磷、 钾养分,而且能改良蕉园土壤酸性从而改善土壤微生物群落结构及环境,有效防控香蕉枯萎病的发生。  相似文献   

9.
连作现象在香蕉生产上非常普遍,而长期连作会导致严重的连作障碍。本文针对香蕉连作障碍,选择连作香蕉13年的地块,采用常规方法结合变性梯度凝胶电泳(PCR-DGGE)技术,在田间条件下研究了轮作茄子配施生物有机肥对高发枯萎病连作蕉园土壤可培养微生物数量、土壤化学性状以及土壤细菌群落结构的影响。结果表明:与连作香蕉相比,轮作茄子处理可显著降低可培养尖孢镰刀菌数量,使其数量从种植初的10~4 cfu·g~(-1)(干土)下降到10~3 cfu·g~(-1)(干土),同时提高了土壤p H,增加了土壤有机质、速效钾、碱解氮含量。无论是轮作还是连作种植模式,与配施普通有机肥相比,配施生物有机肥对可培养尖孢镰刀菌、真菌和细菌数量影响均不显著;但在轮作模式下,施用生物有机肥处理的细菌数量与真菌数量比值(B/F,381.2)显著高于配施普通有机肥处理(270.3)。PCR-DGGE分析结果表明,轮作茄子配施生物有机肥显著改变了土壤细菌群落结构,增加了细菌丰度、稳定性和多样性,其中多样性指数(Shannon-Wiener指数,3.22)较连作香蕉配施普通有机肥处理(2.89)显著增加。以上结果表明,茄子与香蕉轮作有利于连作蕉园土壤的微生态环境,同时轮作配施生物有机肥效果更优。  相似文献   

10.
硒砂瓜连作对土壤真菌群落结构的影响   总被引：4，自引：1，他引：3  
硒砂瓜是宁夏地区重要的经济作物,其连作严重影响硒砂瓜产量和品质。目前硒砂瓜连作对土壤真菌群落结构的影响尚不清楚。本研究采用Illumina MiSeq高通量测序技术,探讨硒砂瓜连作对土壤真菌群落结构的影响。研究发现,硒砂瓜连作土壤中真菌群落多样性指数和丰富度指数随连作年限的增加先上升后下降。供试土壤样本中共检测到真菌8门、25纲、244属,其中子囊菌门（Ascomycota）、接合菌门（Zygomycota）是优势菌门,占90%以上。与对照相比,连作30年土壤中子囊菌门丰度下降32.51%,接合菌门丰度上升29.89%。供试土壤中真菌主要的优势属为被孢霉属（Mortierella）、绿僵菌属（Metarhiziun）、假霉样真菌属（Pseudallescheria）、镰刀菌属（Fusarium）和青霉属（Penicillium）。与对照相比,连作5年土壤中假霉样真菌属丰度增加45.81%,连作10年土壤中镰刀菌属丰度增加26.74%,连作15年土壤中绿僵菌属下降26.83%,连作20年土壤中青霉属增加29.68%,连作25年土壤中绿僵菌属减少18.30%,连作30年土壤中被孢霉属丰度上升29.89%。土壤理化性质与硒砂瓜连作年限间无显著相关性,而与土壤真菌群落结构存在显著的相关性。土壤全磷、碱解氮、有效磷含量是影响土壤真菌群落最主要的因素。研究结果表明,导致硒砂瓜连作障碍的主要原因不是土壤理化性质变化,而是土壤真菌群落结构的改变。研究结果可为硒砂瓜土传病害的生物防治提供参考依据。  相似文献   

11.
低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响   总被引：2，自引：2，他引：0  
【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。  相似文献   

12.
Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.  相似文献   

13.
正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,  相似文献   

14.
“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.  相似文献   

15.
Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.  相似文献   

16.
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.  相似文献   

17.
Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.  相似文献   

18.
Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L?1 nitric acid (HNO3) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L?1 ammonium acetate (NH4OAc) and 1.0 mol L?1 HNO3 extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.  相似文献   

19.
Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.  相似文献   

20.
To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号