雅鲁藏布大峡谷羚牛牙齿珐琅质碳、氧同位素组成及其环境意义     

李玉梅  刘东生  洪冰  储国强  洪业汤  朱咏煊  彭建华  董丽敏  韩家懋 《地理科学》2009,29(6):917-922

以雅鲁藏布大峡谷的羚牛为主要研究对象,讨论其牙齿珐琅质羟基磷灰石结构碳酸盐的碳、氧同位素组成与生活环境之间的关系。羚牛牙齿的碳同位素组成分布范围相当宽,且随着栖息地海拔高度的增加而变重,反映了食谱中C₄植物从无到有、由少到多的变化趋势。C₄植物含量最高可能达到70％。这一变化与当地自然带的划分相吻合。羚牛牙齿珐琅质结构碳酸盐的δ¹⁸O值分布范围较窄,与海拔高度之间没有明显的相关性。氧同位素分馏可能与水源和物种均有关。  相似文献   

芜申运河开通对固城湖水量影响分析          下载免费PDF全文

龚来存  周毅  于飞龙  李香华  陈文权  刘淼 《水文》2017,37(4):62-67

芜申运河是重要的省际干线航道,规划对其整治达到三级航道标准后通航,而芜申运河通航需要固城湖上的通航河道开闸。固城湖为重要的饮用水源地,开闸通航对固城湖水量影响较大。通过建立模型计算得出,每天开闸10次固城湖水量损失约为1.71×10~8m~3/年,每天开闸20次水量损失约为2.87×10~8m~3/年;而固城湖的常态水位为9.5m,相应库容为1.28×10~8m~3,通航对固城湖水量的年损失量占到了固城湖常态水量的1.34~2.24倍左右。如果开闸20次,固城湖需要外调补水以保证水量满足用水需求。经计算,在90%、75%、50%的降水保证率下,需要外调补水保证量达0.64×10~8、0.61×10~8、0.12×10~8m~3/年,占固城湖常态库容的50%~9%。  相似文献   

Banatia aninensis n. gen., n. sp., a new complex larger benthic foraminifer from the upper Barremian of Romania     

《Cretaceous Research》2017

A new larger benthic foraminifera is described as Banatia aninensis n. gen., n. sp. (Family Pfenderinidae Smout & Sugden) from upper Barremian Urgonian-type shallow-water carbonates of the Reşita – Moldova Nouă Zone, southwestern part of Romania. The low to medium trochospiral test of Banatia n. gen. is characterized by marginally undivided chambers and a wide axial part. The latter is made up of pillars continuous between successive chambers and a labyrinthic endoskeleton (plates and pillars) with a fine canal system between. Banatia n. gen. is compared with Pfenderina Henson, Pseudopfenderina Hottinger, and Accordiella Farinacci. The new taxon occurs in algal-foraminiferal wackestones interpreted as deposits of an internal lagoonal realm. So far unrecorded in the literature, the taxon might be paleogeographically restricted (endemic).  相似文献   

Relations between rainfall–runoff‐induced erosion and aeolian deposition at archaeological sites in a semi‐arid dam‐controlled river corridor          下载免费PDF全文

Brian D. Collins  David R. Bedford  Skye C. Corbett  Collin Cronkite‐Ratcliff  Helen C. Fairley 《地球表面变化过程与地形》2016,41(7):899-917

Process dynamics in fluvial‐based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam‐building affect fluvial processes, the complexity in local response can be further increased by flood‐ and sediment‐limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi‐temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446‐km‐long semi‐arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam‐controlled fluvial sand bar deposition, aeolian sand transport, and rainfall‐induced erosion. Empirical rainfall‐erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration‐excess overland flow and gullying govern large‐scale (centimeter‐ to decimeter‐scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic‐driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four‐minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short‐term, storm‐driven rainfall intensity rather than cumulative rainfall, and that erosion can occur outside of wet seasons and even wet years. These results can apply to other similar semi‐arid landscapes where process complexity may not be fully understood. Published 2015. This article is a U.S. Government work and is in the public domain in the USA  相似文献   

世界遗产、旅游目的地和农业遗产景观:以加拿大新斯科舍省大草地为例（英文）     

E.Wanda GEORGE 《资源与生态学报(英文版)》2013,4(3):275-284

加拿大新斯科舍省的大草地是传统土地利用的杰出例子,反映了人类与独特环境相互作用,也因此被联合国教科文组织列入世界遗产名录。大草地不但是加拿大最肥沃的农业景观,还是一个标志性历史遗址,承载着1755年的驱逐阿卡迭人的历史悲剧,吸引了无数游客慕名而来。而今面临着农业的转变和旅游业的衰败双重威胁,人们对大草地于2012年成为世界遗产及其所带来的旅游发展充满期待。本文将大草地作为全球重要农业文化遗产,根据以前的研究,对其成为世界遗产地之后该地区未来经济繁荣和可持续发展的情况进行了探讨。  相似文献   

苏北骆马湖浮游植物群落结构及其水质生物评价   总被引：3，自引：0，他引：3  

彭凯  李太民  刘利  邹伟  吴天浩  龚志军 《湖泊科学》2018,30(1):183-191

为了解骆马湖浮游植物的群落结构及其水质健康状态,于2014年对骆马湖浮游植物进行逐月野外调查研究.共鉴定出浮游植物7门71种属,其中蓝藻门和硅藻门最多,其次为绿藻门.全湖细胞丰度在1.52×10~6~7.89×10~6 cells/L之间,全湖生物量在0.048~12.44 mg/L之间.非多维度量尺度分析结果显示,骆马湖全湖浮游植物生物量从冬春季喜低温的硅藻门为主演替到夏秋季喜高温的蓝藻门为主,表明骆马湖浮游植物有着明显的季节演替规律.与20世纪相比,骆马湖浮游植物优势种属有着很大的变化,富营养化指示属隐藻、纤维藻、针杆藻、鱼腥藻、伪鱼腥藻等明显增多,表明自20世纪以来,骆马湖富营养化程度正在加剧.与邻近的洪泽湖、南四湖、高邮湖、邵伯湖和宝应湖相比,骆马湖浮游植物细胞丰度高于宝应湖,但低于其他4个湖泊.基于浮游植物的水质评价结果,骆马湖目前处于从寡污带向β-中污带过渡的状态,富营养化程度轻于洪泽湖,与南四湖部分湖区富营养化程度相似.  相似文献   

中国大运河沿线城市扩张时空差异研究     

施利锋  黄贤金 《地理科学进展》2019,38(8):1206-1216

自20世纪80年代以来,中国大运河沿线城市建成区规模、空间扩张模式以及空间分布特征都发生了显著变化。虽然当前不缺乏大运河重要河段以及沿线典型城市的研究,但对于大运河沿线城市整体扩张的研究较为少见。论文结合统计数据与遥感数据分析了1984—2016年中国大运河沿线城市建成区扩张速度特征、空间特征以及区域差异。结果显示：① 中国大运河沿线城市建成区扩张速度特征可被归纳为4类,不同类别之间差异显著;② 基于遥感影像提取的运河沿线城市建成区面积通常为相同城市对应年份的统计年鉴中建成区面积的1~2倍;③ 运河沿线城市建成区空间分布整体趋于离散、破碎,江浙地区运河沿线城市的建成区空间分布最离散、破碎,且离散度增长最剧烈。  相似文献   

虚拟垂线流速时差法流量计算方法研究   总被引：1，自引：0，他引：1       下载免费PDF全文

韩继伟 《水文》2020,40(1):52-57

根据目前传统时差法流量计算存在的问题,提出并着重阐述了虚拟垂线流速时差法流量计流量计算方法。在京杭大运河徐州段运河水文站进行了计算验证。结果表明,虚拟垂线时差法与传统时差法和流速仪法趋势一致,虚拟垂线法优于传统时差法。可为工程技术人员提供参考,为国产化时差测流装置提供技术支撑。  相似文献   

大运河遗产河道游憩利用适宜性评价   总被引：4，自引：1，他引：3  

张飞  杨林生  何勋  石勇 《地理科学》2020,40(7):1114-1123

在充分考虑国家文化公园建设等新要求的前提下，采用层次分析法，构建包含4个准则层、10个因子层、22个指标层的评价指标体系，对大运河27段遗产河道的游憩利用适宜性进行评价。研究显示：① 从评价结果来看：大运河27段运河遗产河道的游憩利用适宜性排名情况比较客观，所构建的指标体系对于评价大运河遗产河道的游憩利用适宜性较为可信，对于评价大型线性文化遗产的游憩利用适宜性同样具有借鉴意义。② 从游憩利用适宜度来看：11段游憩利用适宜度较高的遗产河道全部位于京杭大运河和浙东运河沿线的通水、通航河段。4段游憩利用适宜度低的河道均处于大运河已断流区域。浙江、江苏、天津、北京、河北等5省市境内的遗产河道游憩利用适宜性要优于安徽、河南、山东等3省境内的河道。③ 从影响游憩利用适宜性的各准则层来看：游憩利用适宜度高的遗产河道，其生态环境本底质量普遍较高。游憩利用适宜度低的遗产河道，其经济社会条件和旅游发展基础2个指标层的表现也普遍偏低。依托大型线性文化遗产建设国家文化公园，要在对其不同区段游憩利用适宜性开展评价的基础上，构建科学合理的游憩利用模式。  相似文献   

A phenomenological study of the timing of solar activity minima of the last millennium through a physical modeling of the Sun–Planets Interaction     

《New Astronomy》2015

We numerically integrate the Sun’s orbital movement around the barycenter of the solar system under the persistent perturbation of the planets from the epoch J2000.0, backward for about one millennium, and forward for another millennium to 3000 AD. Under the Sun–Planets Interaction (SPI) framework and interpretation of Wolff and Patrone (2010), we calculated the corresponding variations of the most important storage of the specific potential energy (PE) within the Sun that could be released by the exchanges between two rotating, fluid-mass elements that conserve its angular momentum. This energy comes about as a result of the roto-translational dynamics of the cell around the solar system barycenter. We find that the maximum variations of this PE storage correspond remarkably well with the occurrences of well-documented Grand Minima (GM) solar events throughout the available proxy solar magnetic activity records for the past 1000 yr. It is also clear that the maximum changes in PE precede the GM events in that we can identify precursor warnings to the imminent weakening of solar activity for an extended period. The dynamical explanation of these PE minima is connected to the minima of the Sun’s position relative to the barycenter as well as the significant amount of time the Sun’s inertial motion revolving near and close to the barycenter. We presented our calculation of PE forward by another 1000 yr until 3000 AD. If the assumption of the solar activity minima corresponding to PE minima is correct, then we can identify quite a few significant future solar activity GM events with a clustering of PE minima pulses starting at around 2150 AD, 2310 AD, 2500 AD, 2700 AD and 2850 AD.  相似文献