共查询到20条相似文献，搜索用时 171 毫秒
1.
施肥对稻田温室气体排放及土壤养分的影响 总被引：8，自引：4，他引：8
【目的】农业活动引起的温室气体排放对全球变暖的影响日益得到关注,本试验研究不同施肥处理对稻田温室气体排放、 产量和土壤养分的影响,以期为农田可持续利用和温室气体减排提供依据。【方法】在长江中下游地区稻麦轮作区进行田间试验,设置不施氮肥(CK)、 当地习惯施肥(FP)、 推荐N肥(OPT)、 有机无机配施(OPT+M)、 秸秆还田(OPT+S)5个处理,采用静态箱/气相色谱(GC)法测定了稻季CH4、 N2O和CO2的排放情况,调查了不同施肥措施对稻田温室气体增温潜势以及产量,测定了土壤养分,并综合产量和增温潜势对温室气体排放强度进行分析,提出该区域稻田减排增产的合理施肥措施。【结果】 1) 不同处理CH4季节排放总量为OPT+SOPT+M FP OPT CK,排放量为99.02~143.69 kg/hm2; N2O季节排放量为FPOPT+MOPT OPT+S CK,排放量范围为0.95~3.57 kg/hm2; CO2排放顺序与CH4季节排放趋势一致,排放量为7231.64~13715.24 kg/hm2。2)根据稻季CH4和N2O季节排放量以及在100年尺度上的CO2当量计算,不同处理温室气体全球增温潜势大小顺序为OPT+SOPT+M FP OPT CK。在CK、 FP、 OPT、 OPT+M和OPT+S的全球增温潜势中,N2O占的比重分别为10.31%、 26.39%、 21.51%、 22.91% 和11.58%,CH4所占比重分别为89.69%、 73.61%、 78.49%、 77.09%和88.42%。稻田N2O的排放量很少,排放以甲烷为主,因此不同施肥措施所排放的N2O对综合温室效应的贡献远低于CH4。相对于当地习惯施肥处理,OPT、 OPT+M和OPT+S 3种优化施肥措施均在减少化肥施用量的情况下增加了水稻产量,增产率分别为3.6%、 14.3%和 8.5%,其中以有OPT+M处理增产效果最明显。3)不同施肥处理下,CO2排放强度为FP(0.56)OPT+S(0.52) OPT(0.50)OPT+M(0.49),OPT和OPT+M显著低于当地习惯施肥处理,OPT+M CO2排放强度最低。4)有机碳、 全氮、 速效磷和速效钾含量均在OPT+S处理中最高。【结论】不同施肥措施影响稻季温室气体排放,施用有机肥和氮肥均增加了CO2、 CH4、 N2O的排放,秸秆还田增加了CO2和CH4排放,减少了N2O排放。稻田减排应以减少CH4排放为主,推荐氮肥量配施有机肥为碳强度评价体系下最优处理。秸秆还田对土壤养分的改善趋势明显,虽然增加了CO2排放,但考虑到其可避免因焚烧造成大量CO2的排放,总体上依然减少了CO2的排放,但对秸秆还田的适宜量需要进一步研究。 相似文献
2.
华北平原高产农区冬小麦农田土壤温室气体排放及其综合温室效应 总被引：28，自引：5，他引：28
研究不同农业管理措施下小麦农田N2O、CO2、CH4等温室气体的综合增温潜势,有助于科学评价农业管理措施在减少温室气体排放和减缓全球变暖方面的作用,为制定温室气体减排措施提供依据。本研究采用静态明箱气相色谱法对华北平原高产农区4种农业管理措施下冬小麦农田土壤温室气体(CO2、CH4和N2O)季节排放通量进行了监测,估算了不同农业管理措施下小麦季的综合温室效应。结果表明,华北太行山前平原冬小麦农田土壤是CO2、N2O的排放源,CH4的吸收汇。不同农业管理措施对不同温室气体的排放源和吸收汇强度的影响不同,增施氮肥、充分灌溉促进了土壤CO2、N2O的生成,强化了土壤CO2和N2O排放源的特征;但却抑制了土壤对CH4的氧化,弱化了土壤作为大气CH4吸收汇的特征。2009—2010年和2010—2011年冬小麦生长季T1(传统模式)、T2(高产高效模式)、T3(再高产模式)和T4(再高产高效和土壤生产力提高模式)处理土壤排放的温室气体碳当量分别依次为8 880 kg(CO2).hm 2、8 372 kg(CO2).hm 2、9 600 kg(CO2).hm 2、9 318kg(CO2).hm 2和13 395 kg(CO2).hm 2、12 904 kg(CO2).hm 2、13 933 kg(CO2).hm 2、13 189 kg(CO2).hm 2。各处理间温室气体排放差异主要是由于施肥和灌溉措施的不同引起的,秸秆还田与否是造成年度间温室气体排放存在差异的主要原因。T2处理综合增温潜势相对较低,产量和产投比相对较高,为本区域冬小麦优化管理模式。 相似文献
3.
中国农业温室气体排放量测算及影响因素研究 总被引：3，自引：0，他引：3
农业生产过程所产生的温室气体在全球生产活动温室气体排放总量中占有很大比例,因此对农业温室气体的排放量进行测算并分析其影响因素,对实现农业节能减排有重要意义。本文基于1993―2011年中国农业生产的相关统计数据,借鉴前人关于农业生产中各种温室气体排放源排放系数的研究成果,测算了中国农业生产过程中的CH4、N2O和CO2排放量,并分析了影响因素。结果表明,CH4排放量基本平稳波动不大,N2O排放量从1993年的93.21万t波动增加到2011年的120.51万t,农业生产资料CO2排放量由15 626.98万t增加到31 258.10万t。种植业CO2排放主要分为土壤排放和生产资料排放,土壤CO2排放与大气温度、土壤温度、地表温度和土壤水分有关,生产资料CO2排放主要是由化肥和农药造成的;种植业CH4、N2O排放原因较为复杂,还有待进一步研究;动物肠道发酵CH4、N2O排放的影响因素主要取决于动物种类、饲料特性、饲养方式和粪便管理方式等。 相似文献
4.
试验设对照、尿素、尿素＋草甘膦和尿素＋丁草胺4个处理,尿素氮用量为200mg·kg-1干土,除草剂用量为10mg有效成分·kg-1干土。在实验室恒温培养条件下,研究除草剂对菜田土壤温室气体排放的影响。结果表明,菜田土壤中施用氮肥显著增加了温室气体N2O、CO2和CH4的排放。尿素氮肥中添加草甘膦显著抑制N2O、CO2的排放,分别比尿素处理降低48.4%和20.2%;添加丁草胺显著抑制N2O排放,比尿素处理降低23.2%,对CO2排放略有减少但不显著;草甘膦和丁草胺对CH4排放都无明显影响。这说明除草剂对土壤温室气体的排放具有显著影响,但不同除草剂品种的效应也存在明显差异。因此,在农田温室气体排放估算时应考虑除草剂的施用对温室气体减排所产生的效果。 相似文献
5.
6.
麦秆还田方式对旱地土壤综合温室效应的影响 总被引：6，自引：1，他引：5
采用静态箱–气相色谱法,研究了秸秆还田方式对华北平原旱地玉米生长季土壤温室气体(CO2、CH4和N2O)排放的影响。结果表明:小麦秸秆不同还田方式下,土壤CO2、CH4和N2O的排放动态无显著差异,但排放量因温室气体种类而异。秸秆直接还田处理的CO2、N2O排放量分别显著高于无秸秆还田、秸秆原位焚烧、生物质炭还田处理的29.7%、17.5%、31.7%和78.1%、76.3%、114.0%;而CH4排放量在各试验处理间无显著差异。从各处理的综合温室效应(GWP)来看,生物质炭还田处理的GWP比秸秆直接还田处理显著降低28.7%,而与无秸秆还田和秸秆原位焚烧处理无显著差异。考虑到作物产量变化,进一步分析表明,生物质炭还田处理温室气体强度(GHGI)比无秸秆还田和秸秆原位焚烧处理分别降低4.9%和14.9%,差异不显著,比秸秆直接还田处理显著降低36.0%。因此,在华北平原秸秆炭化生物质炭还田具有显著的综合减排作用,是一种土壤农田低碳生产的秸秆利用途径。 相似文献
7.
为给我国旱地低碳农业可持续发展提供科学依据,2018 — 2020年在陇东黄土高原雨养区冬小麦田设置夏闲期种植绿肥和不同施氮量田间试验,通过测定土壤N2O和CH4排放通量,计算N2O和CH4累积排放量等指标,分析不同处理对土壤N2O和CH4排放通量和累积排放量的影响。结果表明,在2个轮作周期内,不同处理的N2O排放峰主要出现在冬小麦播种施肥后,峰值范围平均11.24～31.85 μg N2O-N/(m2·h)。土壤CH4排放无明显峰谷变化趋势,而围绕着零值上下波动,变化范围-46.8～24.5 μg CH4-C/(m2·h)。与休闲-冬小麦处理相比,麦黑豆-冬小麦轮作处理在绿肥填闲期和冬小麦生长期土壤N2O累积排放分别显著增加了26.8%～44.2%和6.2%～52.3%,土壤CH4累积吸收分别显著减少了7.9%～76.3%和4.0%～28.4%。可见,豆科绿肥填闲种植可增加土壤N2O排放,减少土壤CH4的吸收。 相似文献
8.
不同土地利用方式土壤温室气体排放对碳氮添加的响应 总被引：7，自引：0，他引：7
揭示不同土地利用方式下土壤N2O产生机制及其CO2和CH4的排放,有助于土壤温室气体减排措施的制定。本研究以长沙金井河流域酸性红壤上菜地、稻田、茶园和林地土壤为研究对象,控制温度和土壤含水量,采用静态培养-气相色谱法,研究4种利用方式土壤N2O、CO2和CH4的排放对不同碳氮和硝化抑制剂添加的响应。结果表明,由于土壤pH较低,酸性红壤外加氮源后仅有较小的N2O排放。葡萄糖能够促进尿素添加后N2O的排放及土壤反硝化作用N2O的排放。异养硝化作用可能是酸性红壤N2O产生的主要途径。硝化抑制剂双氰胺（DCD）对酸性红壤N2O减排无明显效果。碳氮添加后土壤N2O的总排放量表现为茶园 > 菜地 > 稻田 > 林地。外源有机碳能够显著促进4种利用方式土壤CO2的排放,表现为茶园、稻田 > 菜地、林地。但除稻田土壤CH4排放增加外,菜地、茶园和林地土壤CH4排放对外源有机碳无明显响应。 相似文献
9.
不同施肥方式对农田土壤CO2和N2O排放的影响 总被引：2，自引：0，他引：2
采用静态箱/气相色谱法研究不同施肥方式以及环境因子对农田土壤CO2和N2O排放通量的影响,结果表明,不同施肥方式对农田土壤CO2排放的季节模式无明显影响,但是影响了N2O排放的季节模式。不同施肥方式对土壤CO2排放通量影响不明显,主要影响土壤N2O排放,整个小麦、玉米生长季,分两次施肥的F2与分四次施肥的F1相比,土壤N2O排放量增加,化肥配合有机肥施用(MF)的土壤N2O通量大于单纯的化肥处理,秸秆还田降低了土壤N2O的排放。相关分析结果表明,土壤CO2排放与大气温度、地表温度、土壤温度和土壤水分均呈显著正相关关系(P<0.01)。由于肥料施用的影响,土壤N2O排放和土壤温度、水分的相关分析并不显著。土壤N2O排放受土壤硝态氮和铵态氮变化的影响。 相似文献
10.
硝化抑制剂与尿素配施对旱地土壤温室气体排放及硝化微生物的影响 总被引：1，自引：0，他引：1
为明确施肥措施对旱地土壤温室气体排放的综合效应及微生物机理,采集典型麦田土壤进行室内微宇宙培养,研究了双氰胺(DCD)和烯丙基硫脲(ATU)分别与尿素配施对旱地土壤氮素转化及N_2O、CO_2和CH_4排放的影响,同时监测了不同类型微生物群落的动态变化。结果表明氨氧化细菌(AOB)主导了施氮麦田土壤硝化过程及N_2O排放。单施尿素促进AOB迅速繁殖,使N_2O排放总量提高235%,同时促进了细菌生长,CO_2排放量增加18.5%。DCD与尿素配施极大程度抑制了AOB的生长,显著降低了N_2O排放(59.4%),但促进了细菌的生长并提高了CO_2的排放总量(50.6%)。而ATU与尿素配施同时抑制了真菌、细菌和AOB的生长,对反硝化细菌的影响则相反,使CO_2和N2O排放分别下降28.4%和35.2%。与不施肥相比,氮肥及与两种硝化抑制剂配施均显著降低了CH4的排放量。3种温室气体的综合温室效应在处理间差异显著:Urea+DCDUreaCKUrea+ATU。CO_2排放对综合温室效应的贡献最大,CO_2和N_2O的贡献之和大于98.4%。该研究为深刻理解农田土壤中的微生物行为及生态学效应,合理使用硝化抑制剂以及减缓温室气体排放提供科学依据。 相似文献
11.
【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.
Kyle Devey Michael Mucalo Gordon Rajendram Joseph Lane 《Communications in Soil Science and Plant Analysis》2015,46(4):72-80
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.
《中国生态农业学报》2014,(8)
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.
M.A. Callaham Jr. J.M. BlairT.C. Todd D.J. KitchenM.R. Whiles 《Soil biology & biochemistry》2003,35(8):1079-1093
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
15.
Grete Skrede Berit Karoline Martinsen Anne-Berit Wold Stein-Erik Birkeland Kjersti Aaby 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2013,63(3):193-208
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
16.
《Communications in Soil Science and Plant Analysis》2012,43(7):865-877
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
17.
Y. Bashan J. J. Bustillos L. A. Leyva J.-P. Hernandez M. Bacilio 《Biology and Fertility of Soils》2006,42(4):279-285
Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several
photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene.
This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments
for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference
in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless
of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots.
Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production
or the positive response of the plants towards A. brasilense Cd inoculation. 相似文献
18.
Dhritiman Ghosh Velusamy Srinivasan Olli H. Tuovinen Aaron Peacock Mark Radosevich 《Soil biology & biochemistry》2009,41(6):1331-1334
We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg−1 buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg−1 in conditioned and control soil, respectively. The results demonstrate that BioSep® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation. 相似文献
19.
Pilar García Juan-Vicente Monte Carlos Casanova Consuelo Soler 《Genetic Resources and Crop Evolution》2002,49(1):103-109
Arbitrary oligonucleotides were used as primers to amplifygenomic DNA of 48 wild Spanish populations of Agropyroncristatum, Elymus hispanicus,E. caninus,E. repens,Thinopyrum curvifolium, Th.junceum and Th.intermedium. Genetic diversity was analysedusing nineteen primers. The number of amplified products ranged from8 to 18 per primer and a total of 240 markers were scored. Differentlevels of intraspecific genetic diversity were found, the allogamousspecies E. repens andTh. intermedium being themost variable. Jaccard's similarity coefficients for internalmeasure within and between populations were used to produce a clusterdiagram. The results demonstrate differences in the degree ofsimilarity between taxonomic units. Interpopulational variability andinterspecific genomic relationships of these species arediscussed. 相似文献
20.
The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants. 相似文献