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In the Central High Plateau of Mexico, perennial nopal (Opuntia spp.) orchards are used by several native rodent species. The effect of orchard aging on habitat heterogeneity and rodent assemblages are not known. I surveyed rodent community abundance, species richness, diversity and composition, and habitat heterogeneity (hab-H) in 3 nopal orchards—6 months (O1), 2 years (O2), and 12 years (O3) old—and 1 natural nopalera (NN). Hab-H increased with orchard age, and a unique rodent assemblage was associated with each nopal orchard. Grassland rodents dominated O1 and O2. The shrubby habitat of O3 supported a complex suite of rodents that included grassland and shrubland species, and the NN supported a rodent assemblage that was dominated by shrubland species. In O3, aging of the orchard had led to a hab-H and establishment of a rodent assemblage resembling that of NN. Similar ecological relationships are expected in other nopal orchards of the region. In view of my data, regional conservation efforts should take advantage of the mosaic of differently-aged nopal orchards, because they offer suitable conditions for different species of native rodents, particularly given that some of these species occupy natural habitats that are currently highly fragmented. 相似文献
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在东南极普里兹湾拉斯曼丘陵地区变泥质岩和长英质片麻岩中，定向分布着透镜状、扁豆状和香肠状镁铁质、超镁铁质麻粒岩。这些岩石主量元素、微量元素和稀土元素地球化学特征显示其原岩化学成分具镁铁质堆晶岩特征，并可能代表岩墙的构造作用残留体。在米洛半岛发现石榴子石周围有斜方辉石和斜长石的反应边，斜方辉石和斜长石由下述反应形成：石榴子石＋石英→斜方辉石＋斜长石。这个反应为减压反应，应用地质温压计确定其温度和压力分别为７４７±４８°Ｃ和６．３±０．５ｋｂａｒ，本文首次应用石榴子石－斜方辉石－斜长石－石英组合确立本区早期中压麻粒岩相事件的存在。本文还对镁铁质麻粒岩的原岩成因及矿物中的减压结构所代表的构造意义进行了探讨 相似文献
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分析了采自南极布兰斯菲尔德海峡海槽中ＰＣ１０孔（７５３ｃｍ长）的３９个样品，共鉴定有孔虫１４属２１种。有孔虫埋藏可分为硅质壳、钙质壳和混合壳组合。硅质壳组合代表正常的深海沉积环境，反映了相对弱的海底水动力条件；钙质壳组合是浊流沉积的产物，反映了很强的海底水动力条件；混合壳组合则代表趋于正常的深海沉积环境，反映了由强渐弱的海底水动力条件。晚第四纪以来，本区经历了暖－冷－暖的气候变化过程。 相似文献
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Preliminary study on late Quaternary foraminiferal assemblage in the Bransfield Strait， West Antarctica and its significance of environment 
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下载免费PDF全文 陈超云ＰｒｅｌｉｍｉｎａｒｙｓｔｕｄｙｏｎｌａｔｅＱｕａｔｅｒｎａｒｙｆｏｒａｍｉｎｉｆｅｒａｌａｓｓｅｍｂｌａｇｅｉｎｔｈｅＢｒａｎｓｆｉｅｌｄＳｔｒａｉｔ，ＷｅｓｔＡｎｔａｒｃｔｉｃａａｎｄｉｔｓｓｉｇｎｉｆｉｃａｎｃｅｏｆｅｎｖｉｒｏｎｍｅｎｔ... 相似文献
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Palynological investigations of 16 sections from Spitsbergen, Svalbard, covering the uppermost Carboniferous, Permian and lowermost Triassic succession have been carried out. Because of general poor preservation and barrenness of the majority of the samples, it was not possible to establish a formal zonation for the Permian succession. The study resulted, however, in the recognition of three Permian palynological assemblages, restricted downwards by a Carboniferous assemblage and upwards by an earliest Triassic (Griesbachian) assemblage. The dating of these assemblages is based on palynological correlation with similar palynofloras elsewhere in the present Arctic region as well as dating by marine faunas, which in general give better stratigraphic resolution. The Permian assemblages recognised include (1) the Vittatina assemblage of late Gzhelian to early Asselian age recorded in the lower parts of the Tyrrellfjellet Member (Nordenskioldbreen Formation), (2) the Hamiapollenites tractiferinus assemblage of late Asselian to Artinskian age recorded in the upper parts of the Tyrrellfjellet Member and in the Gipshuken Formation and (3) the youngest Permian Kraeuselisporiles assemblage of late Artinskian to earliest Tatarian age recorded in the Kapp Starostin Formation. 相似文献
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María Gabriela Mángano Luis Alberto Buatois Xiantao Wu Junmin Sun Guocheng Zhang 《Journal of Paleolimnology》1994,11(1):41-65
The Middle to Upper Triassic Tanzhuang Formation represents part of the infill of the early Mesozoic Jiyuan-Yima Basin. The upper part of this stratigraphic unit records deposition within prevailing shallow lake conditions. Well-developed sequences crop out near Jiyuan, western Henan Province, central China. Six sedimentary facies clustered into two facies assemblages were recognized in the lacustrine section. Facies assemblage 1 consists of stacked coarsening-upward sequences composed, from base to top, of organic-rich shales (facies E, type I), laminated siltstones (facies A) and current-rippled laminated sandstones (facies B). Units of assemblage 1 record progradation of small mouth-bar deltas within a perennial open lacustrine system under temperate and humid conditions. Facies assemblage 2 lacks a clear vertical pattern and consists of interbedded fine-grained carbonates and siltstones (facies C); deformed and wave-reworked sandstones (facies D); organic-rich shales (facies E, type II) and clayey mudstones (facies F). The assemblage also represents a perennial, hydrologically-open, shallow lacustrine system, but characterized by strong seasonal climatic control. Water stratification probably occurred in several periods of the lake history. Pangaean megamonsoonal influence is envisaged to explain the strong seasonality imprint evidenced toward the upper part of the Tanzhuang lacustrine column.This is the fourth paper in a series of papers published in this issue on Climatic and Tectonic Rhythms in Lake Deposits. 相似文献
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西南极南设得兰群岛乔治王岛菲尔德斯半岛土壤化学分析表明土壤中存在着一定的化学风化作用。相对于母质,土壤中的SiO_2、Al_2O_3、Fe_2O_3、FeO、MgO,GaO和Na_2O淋失,K_2O、H_2O~+、H_2O~-、TiO_2和P_2O_5富集。土壤中SiO_2/Al_2O_3的平均值为4.71,属弱风化壳类型。硅铝比反映出成土作用时间越长,土壤的风化程度越高,化学风化作用大于南极大陆边缘和内部。Al_2O_3在南极的淋失率大于SiO_2,使较老土壤剖面由下向上硅铝比增大。土壤的化学性质很大程度上取决于母质。南极强烈的冻融扰动作用破坏了土壤分层。土壤中存在着较强的水合作用。 相似文献
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太白山北坡成土因素及不同土壤垂直带谱的比较 总被引：1，自引：2，他引：1
在系统地考察太白山北坡地质、地貌、气候和植被等成土因素的基础上,总结和回顾了用土壤发生分类和土壤系统分类两种分类体系划定的太白山北坡土壤垂直带谱。根据最新的土壤系统分类,太白山北坡的土壤垂直带谱是:暗瘠寒冻雏形土(3500～3767m)———暗沃寒冻雏形土(3300～3500m)———酸性湿润雏形土(2500～3300m)———简育湿润淋溶土(1400～2500m)———简育干润淋溶土(<1400m)。分析、比较表明:两种体系有密切联系,均以成土因素为依据,建立在土壤发生学理论之上;与土壤地理发生分类相比,土壤系统分类用可以度量的诊断层和诊断特性进行土壤分类,不仅能够反映出山地土壤成土因素的垂直变化趋势,而且避免了太白山北坡土壤类型鉴定上的许多歧义。 相似文献
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南极乔治王岛长城湾活有孔虫和死有孔虫的比较分析 总被引：1，自引：0，他引：1
本文对中国首次南极考察队在长城湾采集的海底底质样品作了有孔虫分析,初步查明有孔虫属种,并揭示了长城湾有孔虫组合和分布规律。 相似文献
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关中东部全新世黄土古土壤序列常量元素地球化学特性研究 总被引：4，自引：0，他引：4
对关中盆地东部全新世黄土-古土壤序列(YHC剖面)常量元素分析,发现:YHC剖面化学组成以SiO2、Al2O3和CaO为主,三者平均含量的总和达774.1 g·kg-1,元素含量SiO2 >Al2O3>CaO>Fe2O3>MgO>Na2O>K2OTiO2; 相对黄土L1,Ca、Na、Mg在S0中相对迁移,且Ca、Na淋溶强烈,K、Fe、Al在S0中相对轻微富集; 关中平原东部风化程度弱,处于较弱的脱Ca、Na初级风化阶段(并且可能在沉积源区就已经发生),伴有碳酸盐的淋溶。CIA等揭示的YHC剖面各层的风化顺序S0>Lt>L0>TS>L1UCC,与关中西部扶风和黄土高原中部庄浪相比,关中平原东部的风化程度居中。CIA对气候的响应灵敏,揭示出早全新世风化渐强气候变暖,中全新世风化最强气候暖湿,晚全新世以来风化程度骤然减弱气候恶化,对次一级的气候事件也有反映。 相似文献
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本文测定了三元系ＲＥＣｌ３（ＲＥ＝Ｌａ，Ｐｒ，Ｓｍ）－ＨＯＡｃ－Ｈ２Ｏ（３０℃）的平衡态的溶度数据并绘制了相应的溶度图．在三个体系中分别形成ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ三种物质．ＨＯＡｃ对ＬｓＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ盐析作用程度的不同，表明了轻稀土元素的“一分组效应”，同时依据ＨＯＡｃ对ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ有盐折作用这一结论，提出了一种制备ＬａＣｌ３·７Ｈ２Ｏ，ＰｒＣｌ３·６Ｈ２Ｏ，ＳｍＣｌ３·６Ｈ２Ｏ的新方法． 相似文献
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阿尔泰山古风化壳的地球化学特征 总被引：1，自引：1，他引：1
在阿尔泰山零星残留着一系列古风化壳，本文主要运用土体化学组成分析，研究各类元素在不同母岩风化剖面上的迁移聚集趋势，并结合可溶盐，碳酸钙含量测定以及粘土矿物的Ｘ射线衍射分析，判断风化壳形成过程中淋溶作用的强弱，最终确定其风化程度。 相似文献
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甘肃省宝积山晚三叠世植物群与古地理研究 总被引：1，自引：0，他引：1
阎同生 《地理与地理信息科学》2006,22(1):103-108
晚三叠世地层是我国西北的主要产煤产油地层,对甘肃省宝积山晚三叠世植物群及古地理进行研究,发现植物群31属56种。其中真蕨类植物7属16种,有节类植物4属10种,种子蕨类植物2属2种,苏铁类植物5属7种,银杏类植物6属13种,松柏类植物2属3种,裸子植物种子化石3属3种,分类位置不明化石2属2种,发现了多实拟丹尼蕨和蔡耶贝尔瑙蕨两种北方植物群的典型代表。植物生态类型主要为滨岸、高地和低地。依据纵向分布特点,可将宝积山植物群划分为多实拟丹尼蕨(Danaeopsis fecunda)—周氏似银杏(Ginkgoites chowi)和巨大枝脉蕨(Cladophlebiscf.gigantea)—蟹形新芦木(Neocalamites carcinoides)两个组合带。当时的古气候应为亚热带,通过对沉积物分析确定古环境出现过多次变化,将上三叠统划分为5个古地理演化阶段,可与邻区进行对比。 相似文献
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中国沿海三大城市群城市空间网络拓展分析——以综合交通信息网络为例 总被引：10，自引：7，他引：3
在以“空间流”为逻辑的区域空间组织下,借由城际交通与信息网络的全面发展改变着社会经济空间结构的深度与广度,由此产生的“时空压缩”效应大幅度增强城市信息联系,促使现代城市在“空间流”的作用下不断扩展城市网络空间。针对中国在城镇化发展过程中出现的沿海三大城市群：长三角、京津冀以及珠三角城市群,对其进行城市空间网络分析,结果表明：① 公路运输、普通列车、高速列车、信息网络在一定程度上把相互连接的城市转变成为城市空间对外拓展的网络节点,拉近节点城市与周边城市的时空距离,带动城市群区域信息“网络化”结构的形成;② 长三角城市群城市空间网络主要以上海（沪）、南京（宁）核心节点城市构成,北翼网络化程度较高于南翼线性联系程度,其区域联系密度以“沪-宁”“沪-杭”沿线向两侧递减;其城市群城市网络拓展流向主要是以上海→湖州、上海→宁波、上海→泰州、南京→扬州、南京→镇江、南京→无锡、南京→苏州、南京→上海、杭州→宁波等城市流向,呈现典型多中心结构;③ 京津冀城市群城市空间网络主要以北京、天津为核心向外辐射,形成了以廊坊、沧州、承德、张家口等次级城市网络连线。其城市群城市间网络的拓展流向主要是以北京→天津、北京→石家庄、北京→秦皇岛、北京→廊坊、天津→秦皇岛、天津→石家庄等城市流向,呈现典型的双核心结构,这些城市彼此之间呈现复杂网状联系特征,其中,北京-天津-石家庄围成度中心网络的核心圈层,度中心值较低的其他10个城市节点组成外围低密度圈层;④ 珠三角城市群城市空间网络主要以广州、深圳、珠海为核心向外辐射,形成了以佛山、惠州、江门等次级城市网络连线。其城市群城市网络拓展方向主要以广州→深圳、广州→肇庆、广州→东莞、深圳→广州、深圳→东莞、珠海→东莞等城市流向。其中,广东、深圳处于网络的绝对中心位置,广东-深圳-东莞-佛山围成度中心网络的核心圈层,度中心值较低的其他5个城市节点组成外围低密度圈层,多核心网络结构特征显著。 相似文献
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The Present foraminiferal distribution (live + dead) in Freemansundet between Barentsøya and Edgeøya, Svalbard, has been compared with assemblages in raised marine Holocene deposits in Guldalen on Edgeeya. Four distinct foraminiferal assemblages were identified in Freemansundet, the Elphidium excavatum-Cassidulina reniforme assemblage, the Elphidium hallandense assemblage, the Cibicides lobatulus assemblage and the Elphidium incertum-Haynesina orbiculare assemblage. Four assemblage zones (Zones A-D) have been established in the glaciomarine to marine sediment sequence in Guldalen. Only two of the recent fauna! types were represented here. The Elphidium excavatum-Cassidulina reniforme assemblage, which reflects a proximal glacier environment, was found in the lowermost Zone A (the Elphidium excavatum Zone) and in Zone C (the Elphidium excavatum-Cassidulina reniforme Zone) in the Guldalen stratigraphy; the Elphidium incertum-Haynesina orbiculare assemblage, which reflects ameliorated shallow water conditions, was found in the uppermost Zone D in Guldalen. The marine sequence in Guldalen represents a relatively short period of time during the Early Holocene (ca 9700 to 8300 BP). The succession of the foraminiferal assemblages suggests that the deglaciation was interrupted by a cold period with glacial stagnation just after 9600 bp (Zone B. the Astrononion gallowayi-Nonionellina labradorica Zone). 相似文献
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Siliceous microfossil assemblage succession was analyzed in a 100 m sediment core from Lake Baikal, Siberia. The core was recovered from the lake's central basin at a water depth of 365 m. Microfossil abundance varied greatly within the intervals sampled, ranging from samples devoid of siliceous microfossils to samples with up to 3.49 × 1011 microfossils g-1 sediment. Fluctuations in abundance appear to reflect trends in the marine 18O record, with peak microfossil levels generally representing climate optima. Microfossil taxa present in sampled intervals changed considerably with core depth. Within each sample a small number of endemic diatom species dominated the assemblage. Changes in dominant endemic taxa between sampled intervals ranged from extirpation of some taxa, to shifts in quantitative abundance. Differences in microfossil composition and the association of variations in abundance with climate fluctuations suggest rapid speciation in response to major climatic excursions. 相似文献
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利用浸渍法制备负载型V2O5/Na2SiO3催化剂,并通过XRD、IR、TG-DSC手段对催化剂进行了结构和热分析表征。在以Na2SiO3为载体的基础上,以V2O5为催化剂,通过改变V2O5的负载量,考查了不同负载量的V2O5催化剂对苯氧化为苯酚的催化性能的影响。实验结果表明,当V2O5的负载量为1%时,V2O5的催化性能最好,这是由于V2O5高度分散于Na2SiO3载体上,增大了活性组分V2O5的表面积,从而增加了其活性中心个数及活性组分与反应物的接触面积,增加了其催化活性。 相似文献