共查询到19条相似文献，搜索用时 156 毫秒
1.
松辽盆地是我国白垩系分布最广、厚度最大、发育最全的陆相沉积盆地。孢粉分析发现桫椤孢在松辽盆地白垩系中比较常见。但由于桫椤孢与桫椤科或者蚌壳蕨科具有亲缘关系。桫椤孢在地层中的发现不能明确表明桫椤科植物的存在。这种状况影响了我们对松辽盆地古环境和古气候的精确分析。白垩纪桫椤科矿化茎干化石在黑龙江省齐齐哈尔市克山县的发现为解决桫椤科植物在松辽盆地存在与否的难题提供了重要证据。该化石为桫椤科树蕨植物的茎干片段,包括髓、网状中柱、皮层。分体中柱的横截面呈U、W或S形,外围具有厚壁组织鞘,分体中柱末端朝向髓部或者皮层。髓和皮层由薄壁组织组成,其中分布有许多维管束和根。创伤组织在髓中常见。当前化石是我国第一个桫椤科茎干化石记录。它的发现表明白垩纪时期松辽盆地北部曾经分布着现今多生长于热带、亚热带的桫椤科树蕨祖先类群。结合与其伴生的一些登普斯基树蕨、本内苏铁茎干等化石证据,可能指示当时气候为热带或者亚热带。 相似文献
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基于GIS的长春市公园绿地可达性研究 总被引：1，自引：0，他引：1
《世界地质》2017,(4)
选取长春城市公园绿地作为研究对象,根据研究区遥感影像图,结合吉林统计年鉴,利用ArcGIS的网络分析模块(Network Analysis),得出长春市公园不同时间成本的可达性范围图。评价了长春城市公园的空间分布和服务情况,分析了长春及其各行政区城市公园绿地的可达性。结果显示,研究区只有10.6%的居民能够在15 min内到达公园,28%的居民能够在30 min内到达公园。长春城市公园数量不足并且空间上分布不均匀。南关区和朝阳区公园的可达性最好,绿园区和宽城区次之,二道区公园可达性最差。 相似文献
3.
桫椤树有"活化石"之称,是国家的一类保护植物。现今,在四川自贡市荣县一带居然还保留了大量数亿年前就存在的古老植物——桫椤树,1986年,省政府批准建立"四川省荣县金花桫椤自然保护区"。为什么在世界其他地区的这种古老植物也都已经消失,而这里的桫椤树还存在?这一道自然之谜将通过自贡一带的化石研究成果,对四川盆地的地质历史,气候历史变迁等、层层抽丝剥茧,逐步揭开。使自贡地区的荣县梭椤谷旅游景区增加一点科技知识,为科普教育添砖加瓦。 相似文献
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四川南充嘉陵江曲流地质公园于2006年12月批准为省级地质公园,是四川省以曲流类型为代表的第一个地质公园.笔者曾参加公园内地质遗迹调查评价工作,通过野外调查,查明了公园内地质遗迹景观的类型、数量、分布、形态、组合特征、规模等,初步剖析了曲流景观、凌云山桌状方山、象形石景的成因,探讨了嘉陵江曲流景观的形成演化. 相似文献
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正1分散型世界地质公园的概念及分布情况1.1分散型世界地质公园概念分散型世界地质公园是笔者根据中国世界地质公园中申报批准后地域分布状况而提出的一个特殊概念。目前中国的世界地质公园从地域分布来看有两类,一类是整个公园范围自成一体,只有一个公园边界。其次是由于诸多因素造成了公园组成部分被分散在互不相连的区域中,形成了多个独立的公园边界,有些甚至还地跨多个行政区域(跨省、跨市)。后者笔者定义为分散型世界地质公园。1.2中国世界地质公园地域分布状况(以批准时为据)中国世界地质公园地域分布状况按照批准时的状态分 相似文献
6.
四川射洪硅化木地质公园地质遗迹景观资源特征与评价 总被引：7，自引：1，他引：7
四川射洪硅化木地质公园区位条件优越,地质遗迹景观资源丰富;以硅化木出露广、分布集中、数量多、保存完好为其特征。配以人文景观资源,公园特色突出,景观品质高、个性鲜明、互补性强,配套性好,具有极高的科研、保护和旅游开发价值。 相似文献
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以典型喀斯特城市贵阳市为例,分析地貌特征对于公园绿地供给能力的影响,采用最小邻近成本分析法和空间自相关分析,对贵阳市公园绿地的供给特征以及不同类别公园可达性空间差异进行评价,探讨喀斯特城市公园可达性的提升策略。结果表明:研究区城市公园供给总量较高,但公园斑块面积二元结构明显,且坡度15°以上面积占比53%;公园可达性整体较好,91.89%的居民小区到公园的最小邻近成本低于500 m,但不同类别城市公园可达性存在一定差异。因此,喀斯特山地城市要提升公园服务水平,首先应补足公园服务的盲区,尤其是建成区残存孤峰、小峰丛公园服务能力不足造成的隐性盲区;其次,在老旧城区公园建设需避免盲目求大,应着重提高服务质量与效率,并且发挥自然山体优势建设独具特色的公园服务体系;应结合人口分布特征和不同类别的公园配置状况,合理进行喀斯特山体公园化利用,避免生态环境破坏与公园空置。 相似文献
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Abdalla Ahmed Ahmed Dr. 《GeoJournal》1982,6(1):5-14
This study attempts to relate vegetation distribution to land use history in Jebel Marra, the Democratic Republic of the Sudan. There are evidences that most,if not all, of the woody vegetation communities in Jebel Marra have been derived from some more complex types by continuous disturbance ssince antiquity. Here past and contemporary land use types are described and associated to woody plants distribution. Empirical stratified sampling methods of plant geographers and ecologists are applied to both natural and artificial systems. Frequencies, densities and diversities for all woody plant communities are estimated by standard ecological indices. It was found that throughout known history woody plant communities were subjected to different degrees of suppression. Thus, the present distribution of the woody plant communities reflects the different stages as well as modes of suppression. Drastic population movements and the resulting changes in land use types since antiquity, seem to be the chief explanation behind the variations in modes of suppression. 相似文献
12.
Subir Bera Sudha Gupta Mahasin Ali Khan Aniruddha De Radhanath Mukhopadhyay 《Journal of Earth System Science》2014,123(6):1433-1438
A part of the compressed tree fern axis with leaf and adventitious root scars in unusual arrangement from Plio–Pleistocene sediments of Arunachal Pradesh, India is described as Cyathea siwalika sp. nov. This record suggests that Cyathea was an important component of tropical evergreen forest in the area during the Plio–Pleistocene and this group subsequently declined in importance within the local vegetation. 相似文献
13.
根据南黄海盆地北部坳陷东北凹新的钻井和地震资料,本文详细研究了该凹陷新钻遇地层的地震反射特征及典型岩 性剖面,对该套地层内具有代表性的深度层位采集沉积碎屑样品,利用孢粉组合特征综合判定了该套地层的沉积年代,结 合相邻盆地侏罗纪地层发育情况,认为该套地层为中-晚侏罗世。从岩性及孢粉组合上该井主钻遇地层可划分为上下两个 组合,上组合以裸子植物花粉特别是克拉梭粉占绝对优势,下组合具有较高含量的桫椤孢和克拉梭粉,以此推断南黄海盆 地东北凹是以中-晚侏罗世为主的沉积凹陷。根据井震标定信息,结合凹陷内二维地震测网综合地震追踪对比结果,凹陷 内侏罗系呈现西北厚东南薄的格局,北部千里岩隆起带为盆地的重要物源区。 相似文献
14.
Along with the booming of dendrochronology in China, the woody species for the tree-ring study have expanded gradually from tree species to the shrub and dwarf shrub species in the last decades. The zonal woody species in the vast alpine mountains, arid desert areas and arid regions in China are mostly shrubs and semi-shrubs, which is very important to understand the process of regional evolution, environmental protection and ecological recovery. In this paper, the shrub species which have been studied on tree rings in cold and arid areas of China were collected and sorted, and the fundamental research advances were presented, which include the shrub tree ring identification, radial growth characteristics, and chronology construction by different parameters. The applications of shrub dendrochronology to the subjects in eco-response, paleoclimate reconstruction, hydrological process, ecological study of artificial forest and ecological restoration were also presented. The prospect of shrub dendrochronology in the future was also discussed. 相似文献
15.
A. O. Aweto Dr. 《GeoJournal》1985,10(4):409-415
The organic matter and nutrient contents of soils under four types of bush fallow in a part of the forest zone of SW Nigeria were analysed. The soils were formed from the same parent material of sandstone. The fallows studied were: 1) grass, 2) forb, 3) forb/woody and 4) woody fallows. The total nitrogen and organic matter contents and the cation exchange capacity values of soils under the forb/woody and woody fallow on the one hand were higher than those of the grass and forb fallow on the other. This is due to the greater age, biomass and greater capacity of the forb/woody and woody fallows to generate litter and to protect the soil against organic matter diminution through erosion and thermal decomposition. Of the four fallow types, the woody had the highest organic matter and nitrogen contents and cation exchange capacity. The fallows exert differential effects on soil mineral-nutrients. Compared to the woody fallow, there was a build-up of exchageable calcium in the topsoils of the grass and forb fallow. In contrast, there was a marked accumulation of exchageable sodium and potassium in the topsoils of the forb/woody and woody fallows. The woody and the grass or forb fallows appear to complement one another in restoring soil organic matter and nutrient content after cropping. It is suggested that the woody fallow should be alternated with grass or forb fallow in order to maintain the balance of soil nutrients over time. 相似文献
16.
B.F. Quin R.R. Brooks C.R. Boswell J.A.C. Painter 《Journal of Geochemical Exploration》1974,3(1):43-51
Biogeochemical prospecting for tungsten was carried out at a mineralised area near Barrytown, New Zealand. The tungsten content of the ash of the shallow-rooted tree ferns Cyathea medullaris and Dicksonia squarrosa correlated well with the concentrations of this element in the soil. Sampling of these species therefore provides a possible method of detecting general soil anomalies and moreover is considerably faster than soil sampling under local conditions.Trend surface analysis of the concentrations of tungsten in the trunks of all species of common large evergreen trees sampled on belt transects, could be used to delineate extensions of known tungsten mineralisation in bedrock, and was to some extent superior to soil geochemistry in this respect. 相似文献
17.
Recent flood events in Switzerland and Western Austria in 2005 were characterised by an increase in impacts and associated
losses due to the transport of woody material. As a consequence, protection measures and bridges suffered considerable damages.
Furthermore, cross-sectional obstructions due to woody material entrapment caused unexpected flood plain inundations resulting
in severe damage to elements at risk. Until now, the transport of woody material is neither sufficiently taken into account
nor systematically considered, leading to prediction inaccuracies during the procedure of hazard mapping. To close this gap,
we propose a modelling approach that (1) allows the estimation of woody material recruitment from wood-covered banks and flood
plains; (2) allows the evaluation of the disposition for woody material entrainment and transport to selected critical configurations
along the stream and that (3) enables the delineation of hazard process patterns at these critical configurations. Results
from a case study suggest the general applicability of the concept. This contribution to woody material transport analysis
refines flood hazard assessments due to the consideration of woody material transport scenarios. 相似文献
18.
广西平果县石漠化地区立地划分与生态恢复试验初报 总被引：14，自引：2，他引：12
以石漠化严重和扩展趋势明显的平果县果化镇布尧村龙何屯为例,在现有土地利用类型的基础上,综合坡度、土层厚度、裸岩率、植被盖度等因子,将该屯土地划分为8个立地类型。根据不同立地类型采取相应的生态恢复模式,设计构建不同的植物群落,生态环境治理与农村经济发展兼顾,构筑以木本农业为主的复合农林经营体系。通过两年多的综合治理,试验区农业产业结构调整、封山育林与人工诱导促进植被恢复以及生态苗圃基地建设等方面取得了初步成效。 相似文献
19.
Samples of vitrified and unvitrified Eocene woody plant tissues collected from the Fossil Forest site, Geodetic Hills, Axel
Heiberg Island, have been characterized by TMAH thermochemolysis. All samples are gymnosperm-derived, are of very low maturity
and all share the same post-depositional geologic history. Differences in the distributions of products observed from vitrified
and unvitrified samples suggest that vitrification of woody tissue is associated with modification of the lignin C3 side chain,
following loss of all or most of the carbohydrate present in the precursor woody tissues. The key driver of vitrification
appears to be physical compression of the tissue following biological removal of cellulosic materials. 相似文献