内蒙古敖包吐萤石矿床的Sr、Nd、Pb同位素地球化学特征

敖包吐萤石矿床是内蒙古北部苏莫查干地区单一萤石矿集区中的一个代表性矿床,产于早二叠世大石寨组火山-沉积岩与早白垩世敖包吐花岗岩的接触带上。文章通过分析该矿床岩、矿石的微量元素和稀土元素,揭示出萤石的成矿作用可分为2个阶段,即交代作用和充填作用。交代作用过程中大石寨组的结晶灰岩可能为萤石的形成提供了部分Ca来源,萤石矿石的稀土元素配分模式与海水基本类似,具有Ce负异常;成矿作用后期主要表现为充填作用,形成颗粒粗大的萤石,表现为重稀土元素富集的特征,并随着萤石的沉淀析出,稀土元素总量逐渐下降,反映出成矿流体经历了较长期的演化过程。各地层单元、花岗岩体和萤石矿石的Sr、Nd、Pb同位素研究表明,萤石的放射性同位素组成具有壳、幔源混合的特点,成矿物质来源具有多源性。早白垩世敖包吐花岗岩可能是萤石中F的主要来源,而大石寨组的结晶灰岩则可能提供了Ca。另外,Pb、Nd同位素的极大不均一性,有可能是成矿流体在运移过程中对艾力格庙群放射性组分的选择性吸收的结果。萤石成矿作用与钾玄岩的时空关系暗示了萤石的成矿过程可能是中国东部岩石圈减薄和下地壳的置换地质事件的结果。在构造转型的过程中,燕山中期富碱的酸性花岗岩浆的活动分异出富含F的成矿流体,与幔源流体混合,沿区域重新活化的深大断裂和大石寨组的层间破碎带上升,交代其间的灰岩透镜体,从而形成敖包吐中型萤石矿床。     

Plant distribution at the mobile dune scale and its relevance to soil properties and topographic features

A survey was conducted in an 11-year recovery mobile dune (RMD11) and a 20-year recovery mobile dune (RMD20), in Horqin Sandy Land, Northern China, to determine plant distribution at the mobile dune scale and its relevance to soil properties and topographic features. The results showed that (1) vegetation cover and species number increased from dune top to bottom in the restoration process of mobile dune; (2) the average value of soil organic C, total N, pH, relative height of sampling site, very fine sand content and soil water contents (40−60 and 60−80 cm) of RMD11 were less than that of RMD20, respectively, and there were significant differences (P < 0.05) between the two dunes; (3) soil resources were redistributed by shrub restoration and relative height of sampling site on dune. The distribution of sand pioneer plant, Agriophyllum squarrosum, was positively related to the relative height of sampling site and soil water content, while that of other herbaceous plants was positively related to soil nutrients in the restoration process of mobile dune. These results suggest that at mobile dune scale, plant distributions are determined by a combination of soil properties and topographic feature. Much effort should be made to preserve the interdune lowland and to improve the level of soil nutrients on mobile dune.     

Oceanographic influences on seabirds and cetaceans of the eastern tropical Pacific: A review

This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific, the oceanic region centered on the eastern Pacific warm pool, but also including the equatorial cold tongue and equatorial current system, and summarizes what is known about oceanographic influences on seabirds and cetaceans there. The eastern tropical Pacific supports on the order of 50 species of seabirds and 30 species of cetaceans as regular residents; these include four endemic species, the world’s largest populations for several others, three endemic sub-species, and a multi-species community that is relatively unique to this ecosystem. Three of the meso-scale physical features of the region are particularly significant to seabirds and cetaceans: the Costa Rica Dome for blue whales and short-beaked common dolphins, the Equatorial Front for planktivorous seabirds, and the countercurrent thermocline ridge for flocking seabirds that associate with mixed-species schools of spotted and spinner dolphins and yellowfin tuna. A few qualitative studies of meso- to macro-scale distribution patterns have indicated that some seabirds and cetaceans have species-specific preferences for surface currents. More common are associations with distinct water masses; these relationships have been quantified for a number of species using several different analytical methods. The mechanisms underlying tropical species–habitat relationships are not well understood, in contrast to a number of higher-latitude systems. This may be due to the fact that physical variables have been used as proxies for prey abundance and distribution in species–habitat research in the eastern tropical Pacific.Though seasonal and interannual patterns tend to be complex, species–habitat relationships appear to remain relatively stable over time, and distribution patterns co-vary with patterns of preferred habitat for a number of species. The interactions between seasonal and interannual variation in oceanographic conditions with seasonal patterns in the biology of seabirds and cetaceans may account for some of the complexity in species–habitat relationship patterns.Little work has been done to investigate effects of El Niño-Southern Oscillation cycles on cetaceans, and results of the few studies focusing on oceanic seabirds are complex and not easy to interpret. Although much has been made of the detrimental effects of El Niño events on apex predators, more research is needed to understand the magnitude, and even direction, of these effects on seabirds and cetaceans in space and time.     

科尔沁沙地土地利用与耕作方式对土壤风蚀的影响

土壤风蚀造成的直接生态后果是土地资源的退化。在春播前两次沙尘暴事件中,对科尔沁沙地几种具有代表性的土地类型的土壤风蚀量及土壤特性进行了野外测定、分析,结果表明:(1)在同一沙尘暴天气下,由于土地利用和耕作方式的不同,土壤风蚀量存在着差异,新垦农地和翻耕农地的风蚀量显著高于未垦草地、免耕农地和麻黄地;免耕农地则与未垦草地的风蚀量相差不大,风蚀危害较轻;麻黄地几乎不受风蚀侵害。新垦农地、翻耕农地、免耕农地、未垦草地、麻黄地两次观测的土壤风蚀量平均值依次为24.59、15.60、2.26、1.46和0.22 g/h.cm2。(2)基于土壤特性计算的土壤退化指数结果表明,新垦农地和翻耕农地发生了较为严重的退化。     

科尔沁沙地巴克窑地区近150年的环境演变*

在沉积和花粉分析的基础上,对科尔沁沙地东南部巴克窑地区过去150年的植被和环境演变进行了重建。巴克窑等湖泡的诞生时间是在上个世纪前期,约1837年前后。这个时间也正是科尔沁沙地东南部地区首次大规模人口移入和垦荒年代。突然增加的人类活动导致了沙丘植被的迅速破坏,而植被减少和沙丘活化引起区域水文循环的重新调整,即原来通过植物蒸腾作用输出的水量明显减弱,致使地下潜水位上升,形成一系列湖泡。以后,沙地系统的演化主要是在人类活动、气候和系统内部反馈机制的共同作用下完成的。     

北京连续降雪过程分析

该文对2002年12月份北京出现的1841年以来历史上最长的连续6天的降雪天气进行了合成分析和诊断分析。北半球合成环流形势显示，连续降雪发生在东亚稳定的纬向环流形势下，其上游地区强大经向环流和阻塞高压使中纬度东亚和西太平洋纬向环流得以维持。东亚合成环流的垂直结构表明，连续降雪期间华北地区始终处于锋区中，并存在低空辐合、高空辐散的散度场垂直分布结构。卫星水汽云图显示出有水汽通道向河套倒槽云系输送水汽。华北地区的诊断分析表明，地面和边界层中山东地区分裂高压南侧向北回流的偏南气流是造成降雪的主要水汽通道。变形场的流场结构使水汽在北京附近辐合。垂直剖面展现了华北回流降雪天气近地面层的浅薄的冷空气垫，和暖湿空气回流在冷空气垫上的爬升，并在其上形成一个浅薄的饱和层。     

科尔沁沙地土地沙漠化的历史与现状

科尔沁沙地是我国自然条件相对较好的一个沙地，有着广阔的治理前景。回顾科尔沁沙地的历史变化，认为科尔沁沙地是一个全球气候变化大趋势下由人类生产活动过度而形成的沙漠化区域，在金代至清代之间由于人为活动强度减弱，曾经发生明显的沙漠化逆转。根据全国沙漠化普查所获得的资料，研究分析了科尔沁沙地土地沙漠化现状及其特点，结合土地沙漠化发生的历史过程，讨论了这一地区沙漠化的治理策略。     

固沙林庇护区内降尘特征的初步观测

采用野外定位实测法,连续两年对科尔沁沙地24龄人工固沙杨树(Populussimonii)林庇护区内4～6月份及强沙尘暴事件中的降尘特征进行了观测研究。结果表明:(1)林地庇护区内4、5月份的降尘量较多,分别为273和437kg/hm2,6月份的降尘量较少,为171kg/hm2。(2)林地中央的滞尘效应在风蚀季节和强沙尘暴天气过程中十分显著。(3)林地庇护区内的降尘中粒径<0.02mm颗粒含量占60.7%,降尘中的全C、全N和速效P含量分别高达1.676%、0.163%和210.66mg/kg,这对风沙土表层土壤的细化和养分的积累具有重要的生态学意义。     

Rights in places: An analytical extension of the right to the city

Following recent scholarship on place and place-making, we identify key challenges for contemporary empirical research using the “Right to the City” as an analytic. We seek to distinguish between the aspirational “right” articulated as a political and conceptual call to arms on one hand, and the “actually existing rights” that are carved out through both formal and informal mechanisms (including political protest) in the everyday city on the other. Actually existing rights are defined not through fiat or via momentary revolutionary acts, but through the durability of relationships between multiple actors, including residents, citizens, states, and corporate agents. We re-articulate urban rights as actually contingent and agonistic properties of the relationships that citizens have with places. This paper uses the historic conflict over community gardens in New York as an illustration of how thinking of rights regimes as multiple, overlapping, and placed helps better illuminate potential political interventions. Thinking of rights and places as plural, overlapping, and contingent is analytically productive because it highlights (rather than overwriting) conflicts between competing articulations of rights and privileges in cities.     

阿拉善右旗石窝子―三个井地区找矿潜力分析

内蒙古阿拉善右旗石窝子―三个井地区位于华北板块西北缘与塔里木板块东北缘的结合部位,北部紧邻西伯利亚板块(郝立波等, 2004)。三级成矿带属于朱拉扎嘎―甲生盘元古代、古生代金、铅、锌、硫、铁、铜、铂、镍成矿带（Ⅲ12）,四级成矿带属于朱拉扎嘎金成矿带（Ⅳ123）(内蒙古自治区地质矿产局, 1991)。区域上已发现的矿种主要有煤、盐湖、芒硝、铁、金、磷、石灰岩、石膏、膨润土、滑石、饰面花岗岩等,代表性矿床有叠布斯格、卡休他他铁矿,朱拉扎嘎金矿,脑木洪铜多金属矿等。