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探讨生态空间脆弱性时空分异特征,有助于客观识别区域生态环境的敏感程度和自我恢复能力,并为国土空间规划提供依据。基于VSD模型构建三峡库区生态空间脆弱性分析框架,从空间暴露度、空间敏感性和空间适应力分析2005—2018年三峡库区生态空间脆弱性的时空分异特征及规律。结果表明：(1)三峡库区生态空间脆弱性的3个维度均具有显著的空间分布特征和时间演变规律。生态空间暴露度呈现以重庆的主城区(平均为0.355)和渝东北的万州区(0.416)为双核心向四周逐渐减弱的分布特征;由2005年的0.235 6持续增至2018年的0.269 1。生态空间敏感性呈现“东北高西南低”的分布特征,渝东北的巫溪县敏感性最强为0.691,渝西南的北碚区最低为0.296;由2005年的0.360 7持续增至2018年的0.437 4。生态空间适应力呈现“两端高,中间低”的分布特征,以重庆主城区(平均为0.634)和湖北夷陵区(0.613)为双核心向四周增强;由2005年的0.518 4减至2010年0.457 4后增至2018年的0.571。(2)三峡库区生态空间极度脆弱区主要分布在库区西南地区的重庆市主城区域(平均... 相似文献
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[目的] 以县域为单位对1980-2020年福建省耕地非农化时空演变特征进行系统研究,揭示福建省耕地非农化的空间分布、迁移规律和集聚特征,以期为福建省耕地资源保护与可持续利用提供依据。[方法] 基于福建省1980,1990,2000,2010,2020年5期土地利用数据,运用重心模型、空间自相关等方法分析福建省耕地非农化时空演变特征。[结果] ①福建省耕地资源主要呈带状分布于东南沿海,且耕地面积随时间推移逐年减少。②福建省耕地非农化空间分布地域差异性显著,耕地非农化程度不断加剧,由东南沿海地区逐步向全省范围扩散。耕地非农化高等级区域主要分布在东南沿海地区和西北地区,以耕地转为建设用地、林地和草地为主要类型。③福建省耕地非农化重心偏离于几何中心,其分布具有非均衡性。耕地非农化重心主要位于该省几何中心东南方向,沿先西南后东南再西北的路径转移。福建省东南部地区的耕地非农化程度仍高于西北部地区,耕地非农化空间格局的总体趋势由东南部地区向西北部地区迁移。④福建省耕地非农化呈空间正相关性,空间集聚程度加深。"高-高"集聚和"低-低"集聚的空间变化对福建省耕地非农化空间自相关关系的格局演变起主导作用,"高-高"集聚由东南部地区向西北部地区转移,"低-低"集聚数量减少。[结论] 福建省耕地非农化程度不断加深,空间聚集度加强及耕地非农化重心逐渐向西北地区移动。为确保粮食安全,兼顾经济发展,应采取合理措施保护耕地,实现耕地资源的可持续发展。 相似文献
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“三生空间”视角下万州区景观生态安全评价及其耦合特征分析 总被引：1，自引：0，他引：1
《水土保持研究》2020,(6)
为了探究典型生态脆弱区的景观生态安全格局变化规律,以万州区为例,从三生空间视角出发,综合运用景观生态学、地统计学和耦合协调模型,系统分析了万州区2009—2018年景观生态安全时空变化特征和耦合协调特征。结果表明:(1) 2009—2018年,万州区以林地生态空间为主,城镇生活空间迅速扩张,农业生产空间缩减较多,土地利用程度提高;(2)万州区景观生态安全整体处于较高水平,呈现中部高、东北—西南低的空间分布特征,安全区集中分布在城镇中心,呈明显的"L"型分布,不安全区主要沿长江流域分布;(3)万州区景观生态安全存在较强的空间正相关关系,"高—高"聚集区主要分布于城镇中心,"低—低"聚集区集中分布于甘宁镇、响水镇和龙沙镇;最佳拟合模型为高斯模型和线性模型;(4)万州区"三生空间"景观生态安全的耦合协调度水平不高,整体上呈现"中部高,四周低"的空间分布特征,河流地区的景观生态安全在"生活—生态"空间上还未实现同步发展,城镇中心的景观生态安全在"生产—生态"空间上也处于失衡发展阶段。因此,优化布局各类土地利用类型,控制城镇生活用地的有序扩张,提高生态用地的稳定性和抗干扰性,促进三生空间生态安全的协调发展,对于万州区未来的生态建设和可持续发展具有重要意义。 相似文献
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耕地景观生态安全评价方法及其应用 总被引：12，自引：4，他引：8
耕地作为重要战略资源,其生态安全关系到区域稳定及社会可持续发展。该研究以秦皇岛东北部低山丘陵及东部沿海耕地景观为研究对象,以景观生态学及生态安全理论为依据,构建耕地景观生态安全评价模型,利用1990年、2000年和2010年3期TM(ETM+)遥感影像,对研究区耕地景观生态安全进行综合评价,并对生态安全格局、重心演变及其驱动力进行分析。结果表明:研究区耕地景观生态安全不断降低,耕地景观生态安全指数从1993年的0.63下降为2000年的0.50,低山丘陵区的耕地破碎化更为严重,其生态安全低于沿海区域;研究区域耕地景观生态安全格局变化明显,1993-2000年,Ⅰ级区基本无变化,ⅡⅢ级区相互转化,2000-2010年,Ⅰ级区和Ⅱ级区均出现了扩展,大部分由Ⅲ级区转化而来;近20 a来,耕地景观生态安全重心逐渐向秦皇岛市相邻区域靠近,沿海地区耕地景观生态安全明显增强。降雨量及径流量的减少、人口及经济增长以及土地利用政策是耕地景观生态安全格局变化主要驱动因素。 相似文献
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基于DPSIR-EES-TOPSIS模型的重庆市土地生态安全评价及其时空分异 总被引：3，自引：0，他引：3
土地生态安全是生态环境保护以及区域生态文明建设的基础。以长江经济带的重要节点重庆市为研究对象,基于DPSIR—EES模型构建区域土地生态安全评价体系,在运用TOPSIS法揭示了重庆市土地生态安全整体变化状况的基础上,通过ESDA—GIS法开展了区域土地生态安全时空分异研究。结果表明:(1) 2009—2016年,重庆市土地生态安全呈现波动上升的趋势,土地生态安全由"敏感级"向"良好级"转变;土地生态安全各子系统整体趋于好转;(2) 2009—2016年,主城区土地生态安全有所退化,而渝西片区、渝东北片区、渝东南片区得以改善;总的来说,土地生态安全"敏感级"和"危险级"集中于主城区和渝西片区,而"临界级"和"良好级"主要分布在渝东北及渝东南片区;(3)重庆市土地生态安全存在较强的空间正相关和聚集性,其"高—高"和"低—低"值区呈现增加趋势,"高—高"和"低—低"值区的分布与自然生态状况、人类活动密切相关。研究结果能为区域的土地生态系统保护与社会经济可持续发展提供参考依据。 相似文献
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从不同空间尺度分析特定时期土地整治项目的分布特征,可为制定下一阶段土地整治规划及优化空间布局提供决策参考。基于2011—2015年土地整治项目数据,以县域为评价单元,采用变异系数法、重心模型法和空间自相关模型法,探讨了四川省土地整治项目在不同空间尺度的分布特征,分析了重心转移和空间格局演变特征。研究表明:(1)从时间维度看,四川省土地整治项目总量呈下降趋势,项目绝对规模差异、相对规模差异逐步减小,呈现均衡化趋势。(2)不同空间尺度下土地整治项目具有不同特征。区域层面上,土地整治项目集中分布在盆地丘陵农用地整治区;市域层面上,项目主要集中在成都市和宜宾市,而甘孜藏族自治州、凉山彝族自治州和攀枝花市分布较少。(3)重心移动轨迹中所有重心点均落在盆地丘陵农用地整治区内,空间分布具有一定的地域均衡性。(4)土地整治项目在县域尺度分布存在较为显著的集聚性。高-高集聚区主要集中在盆地丘陵农用地整治区的东北部,低-低集聚区主要分布在川西北高山高原生态整治区。由于受项目区社会经济、人口、地形条件和政策的影响,四川省土地整治项目时空格局均衡性有待进一步提高。该研究明确了四川省土地整治规划重心在盆地丘陵农用地整治区,今后土地整治发展方向在于适时适度地开展川西南山地河谷农用地整治区、川西北高山高原生态整治区土地整治,有利于优化四川省土地空间开发利用格局。 相似文献
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基于景观结构的黄河沿岸土地利用生态风险时空变化分析——以河南省为例 总被引：2，自引：2，他引：0
[目的] 探究黄河流域沿岸城市土地利用生态风险时空变化特征,为土地景观资源保护、生态系统优化与生态环境保护、管控措施制定等提供理论依据。[方法] 以河南省黄河沿岸7个城市为研究区,在GIS与Fragstats软件技术支持下,基于2005,2010,2015以及2018年4期土地利用数据,将研究区划分为1 737个6 km×6 km的生态评价单元,根据景观扰动指数与景观脆弱指数构建生态风险评价模型,借助土地转移矩阵与空间自相关分析方法,对研究区内土地利用变化、生态风险时空变化特征及空间关联格局进行评价。[结果] ①2005—2018年,研究区域内建设用地面积增加,且增长趋势较快;其他几类用地面积均有不同程度的减少;耕地是建设用地增加的主要来源,林地、草地和水域主要转化为耕地。②在研究时段内,研究区域土地利用生态风险在空间上呈现出显著的正相关性,存在空间集聚特征,且“高—高”、“低—低”是生态风险主要的空间聚集模式。③2005—2018年,生态风险最小值和最大值大致呈N形变化;4个时期内高风险区分布区域大致相同,呈条状和块状分布,条状高风险区大多分布在黄河沿岸,块状高风险区大多分布在农村居民点零散分布的平原区;低和较低风险区大多分布在研究区域四周以及西南大部分区域。[结论] 研究时段内,低风险区和中等风险区面积在逐年增加,较低风险区面积先减少后增加,高风险区和较高风险区面积在逐年减少。各风险区主要向相邻风险区转化,仅有少量地区出现跨区转移,说明研究区土地利用生态风险变化相对稳定,生态风险急剧变化的区域较小。 相似文献
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《水土保持研究》2020,(4)
快速城镇化易引发各种生态问题,构建生态安全格局正是对生态过程的积极调控。为构建科学合理的生态安全格局,以内蒙古呼和浩特市为研究区,从自然环境、资源条件、人类干扰等角度构建区域用地扩展阻力评价指标体系,对城市区域空间管制进行了分区;通过最小累积阻力面(MCR)模型建立了区域生态安全格局,识别潜在生态廊道与生态战略点,构建区域生态网络框架,对生态空间进行规划。结果表明:(1)研究区生态安全格局类型区"圈层式"分布明显,较高安全水平以上的类型区占研究区总面积的22.47%,生态安全水平总体偏低。(2)共提取15条潜在生态廊道,识别7条一级生态廊道,9个生态战略点,进而优化"点—线—面"的生态安全格局。(3)生成"一环、两带、两轴、多中心"的生态网络框架,对于提升区域生境质量、提高生态服务价值及优化城市人居环境具有重要意义。结果发现研究区重点开发的乡镇有赛罕区、金河镇、小黑河镇,要引导城市重心向南部、东南部迁移,发展城市新区建设,引导人口、产业合理集聚。其结果可为生态环境治理提供理论参考。 相似文献
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以水资源生态足迹格局模型为基础,通过基尼系数及其分解和重心迁移分析来衡量水资源配置的均衡程度和均衡性的动态演变过程。结果表明:（1）水资源生态压力保持“北高南低”格局,水资源经济效率高效区域主要集中于长江经济带、环渤海经济区、东南沿海地区和京津冀区域周边;（2）水资源生态压力总体基尼系数长期逼近于0.4的均衡性警戒线,地区间水资源生态压力差异较大。水资源经济效率总体基尼系数整体较低,我国水资源生态足迹与承载力不甚匹配,与GDP则较为匹配;（3）2006—2015年水资源生态压力的重心位于中国地理重心东北部,且有往东迁移的趋势,水资源经济效率的重心位于中国地理重心东南部,且有向西南部迁移的趋势。 相似文献
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基于空间自相关的1975—2015年玛纳斯河流域耕地时空特征变化分析 总被引：1，自引：1，他引：1
为揭示耕地空间分布特征与变化趋势，本研究以玛纳斯河流域为例，基于7期（1975年、1990年、1995年、2000年、2005年、2010年和2015年）土地利用数据提取流域耕地信息，采用空间自相关、重心模型、标准差椭圆、地学信息图谱等方法，分析1975-2015年流域耕地空间格局演变特征。结果表明：耕地空间分布存在显著全局正相关，局部空间异质性较强，耕地在时间序列上呈现先减弱后增强再减弱的集聚态势，最终形成以沙湾县商户地乡与石河子市北泉镇为左、右核心的"高-高"集聚分布。耕地空间变化总体呈现西北方向的明显偏移，耕地重心迁移速度经历"缓慢（1975-1995年）-加速（1995-2005年）-减速（2005-2015年）"过程。1995年后标准差椭圆空间分布格局在西北方向愈加明显，椭圆面积大幅增长，耕地涨幅不断增强，并有继续向流域北部荒漠区扩张的趋势。LISA频率图谱中稳定不变与低频区域占比合计达84.58%，耕地空间格局相对稳定。1975-2015年耕地聚集状态主要变化特征表现为"低-低"集聚和"低-高"集聚向"高-高"集聚的转变，流域耕地呈现高密度扩增式发展。通过构建LISA频率图谱，结合重心模型与标准差椭圆较为全面地、动态地掌握了区域耕地空间演变趋势，为耕地资源的科学管理与有效保护提供理论基础与决策依据。 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.
Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater 总被引：3，自引：0，他引：3
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
18.
Aleš Lebeda Ivana Doležalová Eva Křístková Barbora Mieslerová 《Genetic Resources and Crop Evolution》2001,48(2):153-164
Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions. 相似文献
19.
Three slow-growing legume trees used for desert reforestation and urban gardening in the Sonoran Desert of Northwestern Mexico
and the Southwestern USA were evaluated whether their growth can be promoted by inoculation with plant growth-promoting bacteria
(Azospirillum brasilense and Bacillus pumilus), unidentified arbuscular mycorrhizal (AM) fungi (mainly Glomus sp.), and supplementation with common compost under regular screenhouse cultivation common to these trees in nurseries. Mesquite
amargo (Prosopis articulata) and yellow palo verde (Parkinsonia microphylla) had different positive responses to several of the parameters tested while blue palo verde (Parkinsonia florida) did not respond. Survival of all tree species was over 80% and survival of mesquite was almost 100% after 10 months of cultivation.
Inoculation with growth-promoting microorganisms induced significant effects on the leaf gas exchange of these trees, measured
as transpiration and diffusive resistance, when these trees were cultivated without water restrictions. 相似文献
20.
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