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1.
以历史文献、地方志、历史地图为基础,利用核密度分析、莫兰指数等方法对呼和浩特地区1572-2020年的聚落演变过程进行了分析。结果发现:1)聚落数量变化呈波动增长过程。明末清初聚落散落分布,清中叶确定基础集聚格局,民国时期奠定现代聚落格局。2)聚落空间集聚自南部长城沿线半湿润区不断向大青山北部半干旱区移动,发展过程中由插花式布局向条带状扩展布局转变,在武川县北部和黄河沿岸形成高密度集聚。3)水热条件和地貌状况是聚落发展的基础条件,人口数量变化是聚落兴起的前提条件,历史政策和社会经济繁荣是驱动农牧交错区聚落发展的主要因素,聚落格局演变实质上反映农牧交错带北移和地区农业化发展的过程。以上内容对重新认识北方农牧交错带地区聚落的形成过程及原因具有一定参考意义。  相似文献   

2.
关中地区仰韶-龙山聚落遗址分布演变的特点,龙山时期有无出现大规模人口迁出的现象,它们与当时的环境背景有无关系,还需要更多的资料来证明。文中以漆水河流域为例,利用文物普查资料,结合统计学,ARCGIS空间分析方法,研究上述问题。结果表明:从宏观上来说,漆水河流域龙山时期聚落较仰韶时期衰落,但比东部地区情况要好;遗址的迁徙变化更为频繁;漆水河流域遗址整体高程增高和呈远离河流的趋势,与这一时期频发的洪水有一定的关系。从微观上来说,漆水河流域各个支流和河段在遗址数量与规模组合、高程与距河流远近组合与整体演化并不一致。按数量与规模组合的不同可以将各支流和河段分为三组,从三组河流的变化趋势来看,确实存在一种东西向遗址演变模式的不同,但这种不同是否体现这一时期关中地区人口迁出这一现象还不能做最后的结论。按高程与距河流远近组合的不同可以将各支流和河段分为两组,似乎是洪水事件对不同地形地貌区影响不同的结果。最后,西部诸河数量与规模组合的与众不同似乎也可以在关中地区洪水事件发生时间的不同中得到解释。  相似文献   

3.
通过对陕北唐代以来聚落型遗址的数量、分布等信息的提取,结合历史时期气候冷暖波动情况,对近1300年来的聚落遗址数量和空间发生变化的控制因素进行了探讨。近1300年来研究区域内聚落遗址数量在不断减少,分布范围在空间上呈现出向毛乌素沙地东南缘靠近的趋势。通过重建大批古聚落遗址在时间和空间上的分布变化情况,我们可以发现其控制性因素可能并非为沙漠化或气候变化,统治者所采取的相关政策可能更为重要。在研究时段内,唐朝对生存于该区域的党项族采取羁縻府州制度进行管理,宋夏对峙时期党项族重视发展农业,宋政府也注意在当地的农业开拓;元明清时期为聚落址减少时期,统治者对研究区多采取封禁管理。管理政策更多成为近1300多年来聚落遗址数量变化的控制因素。  相似文献   

4.
民宿作为旅游发展新业态,其空间利用方式受到广泛关注。文中基于Airbnb民宿数据,综合采取GIS空间分析方法,分析山东省民宿空间分布特征,并基于地理探测器探讨民宿空间集聚的影响因素。结果显示:1)山东省民宿呈集聚不均衡分布态势。2)民宿空间集聚程度与集聚态势异质性显著,胶东民宿形成“三核集聚、沿海带状布局”的空间密度格局,内陆民宿形成“单核集聚、多核心组团”的空间密度格局。3)社会经济因素是影响山东省民宿分布的首要因素和主导因素,其次是旅游发展因素,最后是区位交通因素与自然环境因素。其中,A级景区密度、酒店密度、人均可支配收入、人口密度是影响山东省民宿分布的主要因素。研究发现为优化民宿空间格局、促进民宿产业高质量发展提供参考。  相似文献   

5.
通过对历史文献中的聚落信息进行搜集整理,建立了河湟谷地聚落地名数据库,重建了明代1373~1596年的聚落格局时空演变过程,将其分为建制扩张期(1373~1411年)和防御扩增期(1480~1596年)。从空间分布上看,河流冲、洪积平原是聚落分布最密集的区域,且湟水流域聚落多于黄河流域。而空间演变过程则表现出冲、洪积平原密度增大并向高海拔地区扩展的特点。聚落的建立和分布受多重因素的影响,区域的自然地理条件、明代建制、军事防御、屯田和驿道的分布均产生重要作用,并在不同社会背景下产生了不同的聚落类型。  相似文献   

6.
文化遗址的空间分布是历史时期人类活动与自然环境关系的重要指示器,对文化遗址空间分布的研究,不仅可以更好的对其进行管理和保护,更能为人类与自然环境和谐共处提供借鉴。文中以新疆地区4533处文化遗址作为研究对象,结合新疆地区的自然环境特征,在地理信息技术的支持下,探讨了新疆文化遗址的时空分布特征与自然环境和人类社会的关系。结果表明:1)新疆历史文化遗址呈集聚分布模式,主要集中在阿尔泰地区、丝路北线、丝路中线和丝路南线等四个地区。2)不同时期的文化遗址重心经历了北疆→南疆→北疆的演变,整体来看文化遗址重心向东北方向迁移。3)不同时期文化遗址的出现频率呈波浪形,文化遗址时空格局的演化不仅与新疆历史时期自然环境的变化有较强的耦合关系(秦汉、隋唐),中原王朝的经营同样可以影响文化遗址的时空变化(明清)。4)文化遗址的平均海拔呈不断降低的趋势,遗址点的平均海拔由夏商时期的1648.32m下降到明清时期的871.92m,文化遗址比重最高的地区集中在801-1800m海拔范围内。  相似文献   

7.
黄土丘陵沟壑区具有复杂的地形地貌和丰富的地方空间基因,散落其间的聚落在适应地貌、气候等自然环境的漫长过程中呈现出独特的人地关系。以米脂县东沟聚落为对象,从微观主体视角揭示了沟壑区聚落空间的组织机制,据此建立聚落形态衍生模型,模拟预测当地聚落空间形态的发展趋势。研究发现:1)居民个体选址择优与聚落邻域互动牵引是影响黄土丘陵沟壑区聚落空间组织的主要动因与机制。一方面东沟居民在聚落选址过程中对自然环境、农业生产、服务设施等因素具有较强的择优偏好;另一方面东沟聚落形态的演化还伴随着邻里聚合与分化、邻里吸引与互斥两种衍生逻辑。2)根据对2020年至2040年东沟聚落形态发展路径的预测,东沟中的聚落用地规模增长到30%之前,聚落仍将在沟口和中前段挖掘开发潜力;聚落用地规模增长幅度在30%~50%的过程中,新增聚落主要在沟谷中后段的沟谷交叉处呈团块状集聚;聚落用地规模增长幅度达到50%~60%时,聚落将在沟谷末梢和支毛沟内少量蔓延。  相似文献   

8.
通过GIS软件作出延安市各地貌类型区城镇聚落图和人口密度分布图,划分出聚落分布等级和人口空间分布等级。并以3个指标,即相对高差、主要坡度和沟谷密度作为地貌地势评判因子,经相关性分析发现,人口密度与地势的相关性比与城镇分布的相关性更为明显。进而拟定本地区人口的粮食消费和经济发展压力指标,计算出延安各地貌类型区人口压力状况,并划分为5个等级,其中河谷阶地人口压力最大,而黄土梁涧人口压力最小。  相似文献   

9.
青藏高原东北缘河谷地带自然环境垂直地带性显著,以本区史前聚落为研究对象,应用聚落中心地理论、资源域的理论,借助GIS方法分析史前聚落的空间分布模式.提出高原河谷地带聚落分布具有沟口-沟尾中心地聚落模式,聚落沿河流和支流沟谷展布,在沟口-沟尾形成规模较大的聚落中心,又形成多个次级聚落围绕聚落中心为核心,形成相对完整、独立的聚落中心系统;沟口-沟尾中心聚落系统形成与垂直地带性不同环境资源获取类型和强度不同有关,这种分布模式为聚落中心地理论在高原上的应用提供了一种新思路.  相似文献   

10.
牧区聚落时空特征及其形成机制——以正蓝旗为例   总被引:1,自引:0,他引:1  
牧区聚落作为人地关系相互作用的重要载体与空间分布类型之一,研究其时空特征能很好的表征牧区乃至人类聚落发展的演变规律。基于GIS和Excel统计分析方法,探讨典型草原牧区正蓝旗在2000—2017年聚落的时空分布特征,进一步分析聚落形成与发展的主要影响因素。结果表明:(1)2000—2017年,正蓝旗聚落分布时空特征呈现急速增长的态势,聚落分布整体较为聚集,呈"南密北疏"的空间差异;研究区聚落斑块规模相差悬殊,小型聚落占主体。(2)区域上,聚落分布格局呈现出明显的区域差异性。在海拔1 196-1 428 m和坡度5°-15°的范围内分布的聚落较多,随着海拔和坡度的变化,聚落斑块数和规模趋于正态分布态势;随着道路和河流的变化,聚落斑块数和规模布局大致呈逐级递减的趋势。(3)水文、交通及地形地貌等地理要素对正蓝旗聚落区位的选择起到很大的限制作用,这三个因素也是决定聚落空间分布的主导因素。总体上,分析该牧区聚落的发展变化与形成机制,可对整个牧区聚落空间布局调整、优化提供重要的借鉴价值。  相似文献   

11.
Fifteen species of dermestid beetles were recorded at ‘Evolution Canyon’ (EC), Lower Nahal Oren, Mt. Carmel, Israel. They represent ~35% of known Israeli dermestid species. The following three species were recorded for the first time in Israel:Trogoderma svriaca Dalla Torre, 1911;Ctesias svriaca Ganglbauer, 1904; andAnthrenus (s.str.) jordaniens Pic, 1934. Adults of 13 species were collected on the more solar radiated, warmer and climatically more fluctuating south-facing slope (SFS); ten species were collected on the opposite, north-facing slope (NFS), which was cooler and climatically more stable. The abundance of adult dermestid beetles was 1.9 times higher on the SFS than on the NFS (86 and 47, respectively). Species richness and abundance distribution at EC (three collecting stations on each slope and one at the valley bottom) were significantly negatively correlated with the plant cover that consisted of trees and bushes (Spearmanr s ,P=0.007 and 0.039, respectively) and perennials (Spearmanr s ,P=0.039 and 0.077, respectively), indicating that non-woody plants were preferred by adult dermestid beetles.  相似文献   

12.
Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.  相似文献   

13.
The genera ofMicrogaster Latreille 1804 andHygroplitis Thomson 1895 from China are presented systematically in this paper. Thirty-two species ofMicrogaster and three species ofHygroplitis are known in China. Diagnosis, character variation, distribution and host of each species among the two genera are presented, including its host and distribution. Keys to the species ofMicrogaster andHygroplitis are given. http://www.phytoparasitica.org posting Dec. 19, 2006.  相似文献   

14.
Plant Viruses Transmitted by Whiteflies   总被引:18,自引:0,他引:18  
One-hundred and fourteen virus species are transmitted by whiteflies (family Aleyrodidae). Bemisia tabaci transmits 111 of these species while Trialeurodes vaporariorum and T. abutilonia transmit three species each. B. tabaci and T. vaporariorum are present in the European–Mediterranean region, though the former is restricted in its distribution. Of the whitefly-transmitted virus species, 90% belong to the Begomovirus genus, 6% to the Crinivirus genus and the remaining 4% are in the Closterovirus, Ipomovirus or Carlavirus genera. Other named, whitefly-transmitted viruses that have not yet been ranked as species are also documented. The names, abbreviations and synonyms of the whitefly-transmitted viruses are presented in tabulated form together with details of their whitefly vectors, natural hosts and distribution. Entries are also annotated with references. Whitefly-transmitted viruses affecting plants in the European–Mediterranean region have been highlighted in the text.  相似文献   

15.
Broad bean mottle virus (BBMV) was transmitted from infected to healthy faba-bean plants by the curculionid weevilsApion radiolus Kirby,Hypera variabilis Herbst,Pachytychius strumarius Gyll,Smicronyx cyaneus Gyll, andSitona lineatus L. The latter appeared to be an efficient vector: acquisition and inoculation occurred at the first bite, the rate of transmission was c. 41%, and virus retention lasted for at least seven days.S. lineatus transmitted the virus from faba bean to lentil and pea, but not to the three genotypes of chickpea tested. This is the first report on the generaHypera, Pachytychius, andSmicronyx as virus vectors, and onA. radiolus, H. variabilis, P. strumarius, andS. cyaneus as vectors of BBMV.Out of 351 samples of food legumes with symptoms suggestive of virus infection, 16, 11, 19, and 17% of the samples of chickpea, lentil, pea, and common bean, respectively, were found infected when tested for BBMV in DAS-ELISA. This is the first report on the natural occurrence of BBMV in chickpea, lentil, pea, and common bean. The virus should be regarded as a food-legume virus rather than a faba-bean virus solely, and is considered an actual threat to food legume improvement programmes.  相似文献   

16.
A collection of 38 PVY isolates from seed potato batches, originating from several Western European countries, was characterized by using current biological, serological and molecular tools differentiating PVY strains and groups. The correlation between the three kinds of tests was good but not absolute. No single serological or PCR method was able to discriminate among the five isolate groups found. Twenty-nine isolates belonged to the PVYN strain and six to the PVYO strain. No PVYC was found. Two other isolates reacted serologically like PVYO, but were unable to elicit a hypersensitive response from the Nytbr gene and probably represent the PVYZ group. At the molecular level, these two isolates showed a combination of both PVYO and PVYN and could be recombinants of these strains. Another isolate reacted serologically like PVYO, but induced vein necrosis in tobacco, like PVYN-Wilga. Some PVYN isolates caused tuber ring necrosis in glasshouse conditions. These might belong to the PVYNTN group. The PVYNTN, PVYN-Wilga and PVYZ groups probably represent pathotypes within strains PVYN and PVYO, respectively. The present study also confirms previous reports showing a high genetic variation at the 5 end within the PVYN strain.  相似文献   

17.
The phenology of the autumn leafroller,Syndemis musculana, a local pest of apple, was studied in order to forecast larval emergence. From 1983–1986, peak flight as determined with sexpheromone traps was always between 13–18 May. The duration of embryonic development was determined at various constant temperatures and used to estimate the periods of egg hatch in these four years. Each year, most eggs should have hatched in the second decade of June.Differences in attack rates between apple cultivars seem to be explained largely by the variation in picking time. Larvae are only half grown at the beginning of harvest (cv. James Grieve), and have gone into hibernation when the latest variety (cv. Golden Delicious) is picked. Moreover, the varieties Cox's Orange Pippin and Belle de Boskoop, picked about half time, are liable to receive additional damage by caterpillars brought with the picked fruits into storage.Various hymenopterous parasites were reared from caterpillars. As the only leafroller in the orchard which hibernates as mature larva,S. musculana may promote winter survival of some parasitoids, like the eulophidColpyclypeus florus.Samenvatting De fenologie van de herfstbladroller (Syndemis musculana Hübner), een incidentele plaag op appel, werd nader bepaald met het doel het uitkomen van de eieren te kunnen voorspellen. In 1983–1986 viel de piekvlucht, bepaald met behulp van feromoonvallen, steeds tussen 13 en 18 mei.De ontwikkelingsduur van de eieren bij verschillende constante temperaturen werd gebruikt om de periode van uitkomen te schatten. De meeste eieren zullen ieder jaar in de eerste helft van juni uitkomen.Geconstateerde verschillen in schade tussen appelrassen blijken goeddeels terug te voeren op verschillen in pluktijdstip. De rupsen van de herfstbladroller zijn pas half-was als de eerste appels eind augustus geplukt worden, terwijl tegen het einde van de oogst begin oktober de meeste al in winterslaap zijn. Met name tussentijdse rassen, als Cox's Orange Pippin and Schone van Boskoop, lopen extra schade op doordat grotere rupsen met de geplukte vruchten in de kist terecht komen.Uit de rupsen werden negen, al van andere boomgaardbladrollers bekende, sluipwespen gekweekt, Omdat deze bladrollersoort, als enige in de boomgaard, als volgroeide rups overwintert, lijkt zij bij uitstek geschikt als winterwaard.This study was carried out at the Experimental Orchard De Schuilenburg, Schuilenburg 3, 4041 BK Kesteren, the Netherlands, to which address correspondence should be addressed.  相似文献   

18.
In the summer of 2004 an epidemic of sclerotinia blight of peanut, a disease caused by Sclerotinia minor, occurred in Texas in fields where the disease was never previously detected. The disease was observed on many plants within one of the fields (>3000 disease foci), although most foci were <1 m. It is hypothesized that these observations were inconsistent with the recent introduction of a monocyclic pathogen, even if disease developed under conducive environmental conditions. The pattern of disease is most suggestive of the presence of foliar (ascospore) infections, although air temperature was above the known limits for apothecia development if the pathogen had arrived in the field in 2004 peanut seed. To further examine this epidemic, 232 isolates were collected, across a variety of spatial scales spanning this field and other Texas peanut fields, and evaluated for aggressiveness, fungicide sensitivity and genotypic diversity. There was wide variation among isolates for the phenotypic characteristics measured, but there was no evidence that a genotypically unique, highly aggressive, and fungicide resistant isolate had been introduced or evolved. The predominant genotype, TX1, which contained 154 isolates, was found in every county and field population.  相似文献   

19.
Four species so far classified in Pseudocercosporella or Ramulispora (hyphomycetes) are associated with eyespot disease symptoms of cereals. Two of these have been linked to teleomorphs that were described in Tapesia. Sequence data derived from the Internal Transcribed Spacer region (ITS1, 5.8S and ITS2) of the rDNA operon showed, however, that the eyespot fungi associated with Tapesia are not congeneric with Ramulispora sorghi, the type of Ramulispora. The genus name Tapesia is now rejected in favour of the conserved name Mollisia, which appears to comprise heterogeneous fungi. Tapesia yallundae is not closely related to the type of Mollisia, M. cinerea, but clusters separately, being more closely allied to species with Cadophora anamorphs. A new holomorph genus, Oculimacula, is therefore proposed for teleomorphs of the eyespot fungi, while the anamorphs are accommodated in Helgardia gen. nov.  相似文献   

20.
In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.  相似文献   

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