泥石流、冰碛和河湖沉积物的粒度特征及判别

根据福克公式,计算出几个典型地区泥石流,冰碛和河湖沉积物的粒度特征参数,用核心区域图解法和判别分析方法认识和分析参数的分布特征和联系,初步建立判别的图形模型和数学模型,用以反推和判别参数反映的沉积类型和沉积环境。     

基于地质灾害的陇南山区生态风险评价——以陇南市武都区为例

陇南山区地质构造活动强烈,频繁的地质灾害对生态环境和生态安全构成严重威胁。分别以陇南市武都区的主要地质灾害(滑坡、泥石流和地震)和景观类型为风险源和受体,以景观结构指数和易损性指数作为评价指标,构建生态风险评价模型,进行生态风险特征评估。结果表明:武都区生态风险特征的分布主要受地质灾害风险分布和景观格局的影响,人类活动、植被覆盖度和海拔梯度也是重要的影响因素。极高风险区和高风险区主要集中分布在东江镇以东的白龙江沿岸及整个白龙江南岸、安化、马街、汉王和两水镇北部等地;低风险区和较低风险区主要分布在武都区东部和南部以及西部和西北部区域。基于景观结构的多风险源生态风险评价对于区域生态风险管理具有重要的现实和指导意义。     

西藏陆地生态系统敏感性和脆弱性评估（英文）

青藏高原的生态平衡对中国乃至亚洲的生态安全具有极为重要的作用。本文提出和改进了针对高山高原陆地生态系统生态敏感性和脆弱性评估的指标和方法;评价了西藏自治区的冻融侵蚀、土地沙化、水土流失和土地盐渍化的敏感性;并从综合生态敏感性、生态压力和生态弹力三个方面评价了其生态脆弱性。结果显示,西藏陆地生态系统对冻融侵蚀、土地沙化和水土流失问题非常敏感。极度和高度敏感区分别占西藏自治区总面积的9.62%和83.69%。极度和高度脆弱区分别占0.09%和52.61%,主要分布在西藏西部的喜马拉雅和冈底斯山山区,念青唐古拉、唐古拉、可可西里和昆仑山区,及羌塘高原西北部和北部地区。这些结果有助于根据各区域存在的生态问题提出具有针对性的保护方案。     

铭记陈述彭先生博大精深的学术思想

陈述彭先生是我国现代遥感和地理信息系统的开拓者和引领者,是地图学研究和应用领域卓有建树的传承者和创新者。新中国成立以后,中国在地图学、地理信息系统和遥感领域取得系列重大成果,很好地服务于社会经济发展、资源和生态环境保护,在国际上颇具影响,这些都和先生博大精深和与时俱进的学术思想的指导和严密的科学组织密不可分,他为我国地球科学、空间科学和环境科学发展做出了杰出的贡献。     

地理答题的规范性和灵活性初探

地理答题的规范性和灵活性是指在地理测试过程中,学生要根据试题要求,按照一定的地理思维和解题规范,灵活而准确地分析题意、组织和表述答案。学生答题欠规范、缺乏灵活性的情况非常普遍,这一方面反映了学生对地理基础知识掌握和熟练程度不够,另一方面也反映出学生缺乏针对性的练习和指导。地理答题的规范性和灵活性训练和指导主要措施有地理教师的重点讲解和引导、学生的自我练习和训练、同学之间的互讲和互评。     

深化改革 开拓进取 以崭新姿态迎接林业新科技革命

<正> 1997年林科院通过认真学习和贯彻落实邓小平理论和党的十五大精神,广大职工的政治思想水平有了大的提高;通过科技体制改革的全面启动和健康发展,使科研和推广工作取得重大进展;通过科技开发和产业建设,促进了成果转化和自身发展能力的可喜进步;通过扩大开放和有效地国际交流与合作,提高了我国林业科技在国际上的地位;通过人事改革和人才培养,使科技人员的水平和干部素质有进一步提高;通过坚持“两手抓和两手都要硬”的方针,使     

可持续旅游、生态旅游及实施方案

阐述可持续旅游和生态旅游的定义、可持续旅游和生态旅游之间的关系以及实施可持续旅游和生态旅游战略的途径。论述评价可持续旅游和生态旅游的标准以及国际上生态旅游实施现状。分析实施生态旅游战略所面临的难题。提出中国实施可持续旅游和生态旅游战略的必要性、目标和方案。     

河北唐海湿地和鸟类自然保护区的管理现状及保护对策

介绍了唐海湿地和鸟类省级自然保护区的主要保护对象和管理现状,分析了保护区在保护和管理方面存在的问题和矛盾,从政策法规、加强执法、筹集资金和引进人才等方面提出了保护区的保护和可持续发展对策。     

地理信息呈现方式及其备考策略

正新课改后的地理试卷相比以前更加注重考查学生的地理学习能力和学科素养,即四个能力的考查——获取和解读地理信息、调动和运用地理知识和地理基本技能、描述和阐释地理事物和地理基本原理与规律、论证和探讨地理问题。在四个能力中,获取和解读地理信息能力是最简单、最基础的,但是从学生答题效果来看往往让人痛心疾首,很多简单的问题学生错误率却很高,     

滇池不同底泥条件下黑藻和金鱼藻的生长生理特征

为了探讨富营养化湖泊沉水植物恢复的可行性,通过实验,研究了滇池草海和外海3种不同的底泥对黑藻(Hydrilla verticillata)和金鱼藻(Ceratophyllum demersum)生长发育和生理活动的影响。结果表明,草海底泥和混合底泥(外海底泥和草海底泥等质量混合)培养的黑藻和金鱼藻,其株高、节间距、株数和生物量都显著高于外海底泥中黑藻和金鱼藻的相应指标(p0.05);外海底泥中生长的黑藻的根冠比显著高于其他两种底泥中生长的黑藻的根冠比(p0.05)。草海和混合底泥中培养的黑藻和金鱼藻的叶绿素a和过氧化物酶含量显著高于外海底泥中的黑藻和金鱼藻(p0.05);外海底泥中金鱼藻的丙二醛含量显著高于另外两种底泥中金鱼藻的丙二醛含量。有机质和营养盐含量较高的草海底泥和混合底泥更有利于黑藻和金鱼藻的生长,但与黑藻相比,金鱼藻具备更高的耐贫瘠底泥的能力。     

藏南沉错湖泊三角洲的沉积相及沉积环境

在西藏自治区沉错湖泊三角洲平原和湖内钻孔取芯 ,利用14 C和ESR测年方法建立了钻孔剖面的年代标尺。在岩芯描述、沉积物粒度分析和CaCO3含量分析基础上 ,对沉错湖泊三角洲的沉积环境和沉积相进行了解释分析。 36 7m长的岩芯大致记录了 5 5万年以来的沉积历史。全孔平均沉积速率约为 0 6 6 7mm/a。 16 92 0aBP以来三角洲的沉积速率较大 ,平均为 1 2 7mm/a。由于沉积物物质来源的多源性导致CaCO3在剖面上的无规律性变化。但是 ,沉积物粒度和沉积序列变化指示全套沉积由底部的冲积扇相向上过渡为水下扇亚相和三角洲沉积相。在大约 175 0 0aBP～ 14 0 0 0aBP时期 ,沉错存在高湖面阶段。沉积序列中记录了末次冰期最盛期 (LastGlacialMaximum )和新仙女木事件 (YoungerDryas)。沉积特征和沉积环境的变化主要受湖面涨缩变化所控制。而湖面升降变化的驱动因素主要为气候 ,尤其夏季风的强弱和冷事件     

Ostracod assemblages and their environmental significance from the lake core of the Nam Co on the Tibetan Plateau 8.4 kaBP

A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods (Crustacea: Ostracoda), which belong to 6 genera have been identified. According to the variations of the ostracod assemblages and the ostracods ecological features, which are sensitive to the changing environment, three main stages can be distinguished as follows: Stage I was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage II was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of climate, from wet-cold to dry-cold during this period, had constructed the basis of present environment in the Nam Co. Stage III was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simultaneous with the high prolificacy of ostracod, and transported from other places. The abundance of Candona juvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.     

8.4 ka以来纳木错湖芯介形类组合的环境变化意义

A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods (Crustacea: Ostracoda), which belong to 6 genera have been identified. According to the variations of the ostracod assem-blages and the ostracods ecological features, which are sensitive to the changing environ-ment, three main stages can be distinguished as follows: Stage I was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage II was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of cli-mate, from wet-cold to dry-cold during this period, had constructed the basis of present en-vironment in the Nam Co. Stage III was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simulta-neous with the high prolificacy of ostracod, and transported from other places. The abun-dance of Candona juvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.     

Temporal patterns in lacustrine stable isotopes as evidence for climate change during the late glacial in the Southern European Alps

We investigated oxygen and carbon isotopes of bulk carbonate and of benthic freshwater ostracods (Candona candida) in a sediment core of Lago Piccolo di Avigliana that was previously analyzed for pollen and loss-on-ignition, in order to reconstruct environmental changes during the late glacial and early Holocene. The depth–age relationship of the sediment core was established using 14 AMS ¹⁴C dates and the Laacher See Tephra. While stable isotopes of bulk carbonates may have been affected by detrital input and, therefore, only indirectly reflect climatic changes, isotopes measured on ostracod shells provide unambiguous evidence for major environmental changes. Oxygen isotope ratios of ostracod shells (δ¹⁸O_C) increased by ～6‰ at the onset of the Bølling (～14,650 cal BP) and were ～2‰ lower during the Younger Dryas (～12,850 to 11,650 cal BP), indicating a temporal pattern of climate changes similar to the North Atlantic region. However, in contrast to records in that region, δ¹⁸O_C gradually decreased during the early Holocene, suggesting that compared to the Younger Dryas more humid conditions occurred and that the lake received gradually increasing input of ¹⁸O-depleted groundwater or river water.     

The ostracod assemblages and their environmental significance in the Chen Co area, southern Tibet in recent 1400 years

The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The 210Pb and 137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples' cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.     

The ostracod assemblages and their environmental significance in the Chen Co area,southern Tibet in recent 1400 years

The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The²¹⁰Pb and¹³⁷Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples’ cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.     

柴达木盆地沙漠沉积中的新仙女木事件记录

对柴达木盆地晚更新世沙漠演化过程的研究,发现青藏高原沙漠沉积中清楚地记录了新仙女木事件,并呈干冷温的气候效应,进一步分析得出：新仙女木事件在我国不同自然气候带呈单一的干冷降 温效应,并作为多模式效应。     

SEDIMENTS FROM AROUND THE LOWER YOUNGER DRYAS BOUNDARY (SE ARIZONA,USA): IMPLICATIONS FROM LA‐ICP‐MS MULTI‐ELEMENT ANALYSIS

One of the prominent features in sediment sequences formed around the Allerød‐Younger Dryas transition (c. 12.9–12.8 ka bp ) in North America is a dark layer of organic‐rich material, i.e. the black mat. The black mat sequences in southeast Arizona contain a thin sandy basal layer corresponding to the lower Younger Dryas boundary. Trace element concentrations in the lower Younger Dryas boundary sediments, in the black mat, in the host sediments, and in charcoal from Western Europe and southeast Arizona were studied using LA‐ICP‐MS. The black mat samples and samples of the underlying host sediments display compositions similar to the average continental crust, while the sediments from the lower Younger Dryas boundary are enriched in rare earth elements, Ni, and Co whereas Ta, Nb, Zr, and Hf are depleted relative to the rare earth elements. Such a difference in compositions between the lower Younger Dryas boundary sediments and other sediments points to a short enigmatic event, which changed conditions of sedimentation just before the onset of the Younger Dryas cooling. The presence of products of biomass burning of still unknown origin is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary.     

Lake-Level Fluctuations and Small-Scale Vegetation Patterns During the Late Glacial in The Netherlands

Late glacial changes in the vegetation were studied in and around a former lake on the southeastern side of a coversand ridge near Milheeze (southern Netherlands). Analyses of microfossils and macroremains and AMS ¹⁴C dating were performed on four sediment cores along a transect from sand ridge to the lake centre. Small-scale vegetation patterns and lake-level fluctuations were reconstructed in detail based on the information provided by the transect. For the first time in The Netherlands, cores along a transect within one lake were used to reconstruct the amplitude of late glacial lake-level fluctuations. Near Milheeze, a small and shallow lake was formed during the Bølling. The large increase in the water level during the Bølling and early Allerød, and the transition to more eutrophic conditions at the start of the Allerød, were probably related to the disappearance of permafrost. During the Allerød, open birch and pine woodlands developed in the area. In the lake, organic deposits accumulated, and the lake size and depth fluctuated. At the start of the Younger Dryas, higher lake water levels were recorded and woodlands became more open as a result of both a drop in the temperature and an increase in the effective precipitation. During the late Younger Dryas the lake water level dropped as the climate became drier and temperatures slightly increased. Accumulation of organic deposits in the lake ceased at the end of the Younger Dryas, which was caused by a drop in the water level in combination with the hydroseral succession process within the lake itself. The climatic signal reflected in the late glacial flora and lake-level fluctuations agree well with other published data from The Netherlands.     

8.4 ka 以来纳木错湖芯介形类组合的环境变化意义

对青藏高原中南部纳木错长332cm的NMLC1孔湖芯研究发现,沉积物的介形类动物群计有6属15种。介形类属种生态特征和组合变化分析表明这些介形类对环境条件具有敏感性,其组合能够很好地反映过去环境变化的特征。结果表明,8．4ka以来具有三个不同的环境变化时期：早期在8400～6800aBP,湖泊由浅向深发展,环境具有相对冷湿的特征：中期在6800～2500aBP,湖泊深度逐渐加大,环境经历了暖湿-冷湿-冷干的变化．其中由冷湿向冷干的转化奠定了纳木错现今环境条件的基础：晚期在2500--9aBP,湖泊深度继续增加,这个时期的较早阶段,继续保持了前一时期的冷干特点,但湖水盐度可能开始增加．较晚阶段的冷干化加剧,陆面流水的活跃性大大降低。研究发现,纳木错NMLC1钻孔介形类黑色壳体的高峰值与介形类的最大生产量相一致,并且与沉积水动力条件增强相适应．指示了这些黑壳的产生与介形类的大量繁殖处于同一阶段．并且主要为异地搬运为主。钻孔中出现大量Candona幼虫壳体．其原因可能与沉积环境的水动力条件迅速改变有关。