Quantitative reconstruction of the paleosalinity at Qinghai Lake in the past 900 years

Based on the function relationship between the shell length of Limnocythere inopinata and the salinity of its living water in Tibetan Plateau lakes, the paleosalinty of Qinghai Lake in the past 900 years was reconstructed through the measurement of the adult body length of Limnocythere inopinata. Meanwhile, the paleosalinity sequence of Qinghai Lake during the same period was rebuilt by the St/Ca ratio of the shell of Eucypris inflata combined with the St/Ca ratio of living ostracod valves from the species of genus Eucypris inflata and the host water. The paleosalinity results obtained by two different methods were compared and assessed in this paper. To check the result, it was also contrasted with other historical climatic sequences of this area including tree ring and ice core. It was shown that the paleosalinity sequence rebuilt by adult ostracod body length had high reliability, and the paleosalinity reconstruction method by trace elements of ostracod shells was not suitable for Qinghai Lake. From the reconstructed paleosalinty sequence of Qinghai Lake, it can be found that low salinity during 1160-1290 AD showed the humid climate condition on the Mediaeval Warm Period in this area, while the high salinity during 1410-1540 AD, 1610-1670 AD and 1770-1850 AD which was corresponding to the three cold pulses of the Little Ice Age with a dry climate condition. And the high salinity in the latest several decades was consistent with recent warm and dry trends of the climate in this area. The good consistency of the reconstructed palaeosalinity sequence and the precipitation sequence in this area rebuilt by tree ring proves the reconstruction of past lake salinity is reliable.     

A carbon- and oxygen-isotope record of recent environ- mental change from Qinghai Lake, NE Tibetan Plateau

An understanding of natural climatic variability is essential for evaluating anthropogenic impacts on recent and future climate[1—3]. Due to the lack of lengthy instrumental records, such an understanding must be gained from natural archives of climate change. Palaeolimnological indicators of past lake levels may provide a sensitive record of changes in effective precipitation in closed basins. This approach is particularly relevant on the Tibetan Plateau, where instrumental records are very…     

青海湖北岸植物群落的数量分类

依据对青海湖北岸植物群落的踏查和对鸟岛、大通山,以及海晏湾3个地区的野外取样调查,比较讨论了重要值的各类计算公式.认为,在草地植物群落中用重要值=(相对盖度+相对频度)/2×100比较科学,并用组平均法(GAM)对该地区植物群落进行了分类,划分为24个群落,分别属于沙生植被、沼泽草甸、草甸、温性草原、高寒草甸、高寒灌丛及高山流石滩稀疏植被等7个植被型.     

Boron isotopic fractionation during incorporation of boron into Mg（OH）2

Experiments of boron incorporated into Mg（OH）2 from magnesium-free synthetic seawater were carried out at various pH values, in order to investigate the adsorption species and the variation of isotopic fractionation of boron on Mg（OH）2. The results showed that the incorporation of boron into Mg（OH）2 was very rapid and reached the equilibrium after 4 h. The [B]s and the partition coefficient Kd between Mg（OH）2 and final solution decreased with the increasing pH. The maximum values of [B]s and Kd were much higher than that of boron adsorbed on metal oxide or clay minerals, indicating that the incorporation capability of boron into Mg（OH）2 was very strong. When the adsorption reached the equilibrium, the δ 11Bfsw was lower than δ 11Bisw. The boron isotopic fractionation αs-fsw was between 1.0186 and 1.0220 with an average of 1.0203. All these indicated that 11B incorporated into Mg（OH）2 preferentially due to B（OH）3 incorporation into Mg（OH）2 preferentially. The deposition reaction of B（OH）3 with Mg（OH）2 was the direct reason for B（OH）3 incorporation into Mg（OH）2. During the boron incorporation into Mg（OH）2, the isotopic fractionation characteristic of boron was decided by the simultaneous existence of adsorption of boron on Mg（OH）2 and the deposition reaction of H3BO3 with Mg（OH）2. Different from the fact that only B（OH）4-species incorporated into bio-carbonate, B（OH）3 and B（OH）4 incorporated into Mg（OH）2 simultaneously, and B（OH）3 incorporated into it preferentially. The lower pH is, the more incorporated fraction of B（OH）3 will be. Mg（OH）2 exists widely in madrepore, which influences the quantitative correspondence of the boron isotopic composition δ 11Bcarb of corals on the pH of the seawater badly, and brings serious uncertainty to the δ 11Bcarb as the indicator of the ancient seawater pH.     

青海湖沉积物中微量元素纵向分布反映的古环境意义

通过对青海湖QH1岩心沉积物中微量元素Li,V,Cs,Co,REE(La,Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Er,Yb)及wCs/wRb的高分辨率分析,结果表明:微量元素在沉积物中的质量分数变化与沉积环境密切相关,在温暖湿润的气候环境下,沉积物中w∑REE,wLi,wV,wCs,wC.较高、wCs/wRb较大;而在冷干的气候环境条件下,元素质量分数相对较低.∑REE(稀土总量)与wCs/wRb之间呈良好的正相关性,∑REE可以作为反映青海湖环境的一个有效指标.近8500年来湖区气候环境变化特征表现为冷干与暖湿的交替,气候的突变在沉积物上表现为元素质量分数的突变.     

青海湖面积动态监测系统的设计与实现

文中以遥感影像为依托,根据历史及现有的遥感影像数据生成各时期青海湖范围水涯线,结合其他矢量数据以及统计数据,设计并实现了“青海湖面积动态监测系统”.系统能够将青海湖面积变化以多种方式客观、科学的展现出来,为青海湖流域生态环境保护和综合治理提供了数据参考.     

青海湖湿地生态系统服务价值分析

依据生态系统价值分析理论和方法，本文定量分析了青海湖流域湿地生态系统的直接和间接经济价值．结果表明青海湖流域的主要服务功能价值约362．71亿人民币；其中涵养水源的价值最大，为289．66亿人民币；其次为自然和生物多样性保护、科学考察及旅游和水产品价值．由于气候变化和人为影响，青海湖流域的生态服务价值在不断减少，只有采取整体的保护措施，才能实现当地社会和经济的可持续发展。     

青海湖风景名胜区旅游可持续开发研究

目的探析青海湖风景名胜区的旅游可持续开发对策。方法运用实证分析法与行为调查法进行探讨。结果通过对青海湖风景名胜区旅游可持续的空间内容研究,即对旅游区资源类型与景观结构、自然环境结构现状与旅游环境容量以及客源目标市场与地域吸引范围进行分析,并在此基础上提出旅游可持续发展的对策。结论提出构建生态旅游系统示范区、大力调整旅游产品结构、以形象标志景区带动旅游景点的整合营销等6点有关青海湖风景名胜区旅游可持续发展对策,为类似干旱区大型湖泊旅游资源的可持续开发提供借鉴。     

青海湖流域近10年湿地动态遥感监测

分别利用2000年、2005年和2010年3期丰水期(7-10月)的TM影像数据,同时结合气象台站观测数据和地面调查资料,依据青海湖流域湿地分类体系,采用湿地类型转移矩阵等方法,分析近10a青海湖流域湿地的动态变化情况.结果显示,青海湖流域湿地约占流域总面积的23.99％,10 a来湿地总体比较稳定,总面积变化不大,而湿地类型之间的变化较明显,主要是永久性咸水湖、永久性河流、内陆盐沼、洪泛区平原和沼泽化草甸之间的变化.     

青海湖流域近50年气温、降水变化特征研究

本文对青海湖流域1961-2010年近50年来的气温和降水变化特征进行了研究,结果表明,青海湖流域气温呈明显的增加趋势,线性增温率最大达到0.40℃/10a;存在较为明显的4次增温期,特别是最近一次增温期,持续时间长,最大增幅达0.1℃/a.降水量虽然没有明显的增加趋势,但存在三次明显的增多期,最大降水量出现在1988-1989年间.在季节变化上,气温均出现了不同程度的增加趋势,尤其以冬季和秋季增温趋势最明显;降水的季节增幅不明显,降水主要集中夏季,夏季多年平均降水量为239.30mm,占全年降水量的65%左右.近50年气温、降水变化特征表明青海湖流域目前正处于增温增湿阶段.     

High－resolution precipitation variations in the Northeast Tibetan Plateau over the last 800 years documented by sediment cores of Qinghai Lake

Short cores of about 80-cm retrieved from three main basins of th e deepwater areas in Qinghai Lake,the largest inland enclosed lake in China, were studied. Sta-ble isotopes of authigenlc carbonates, grain-size, carbonate and organic matter content at 5-year resolution are used to reconstruct the climatic history over the last 800 years in the Northeastern Tibetan Plateau. Chronology was established according to 210^pb dating and 137^Cs methods and the core corrdation. It is found that cores from different deep basins of the lake can be well correlated. The sedimentary rate is highest in the western basin of the lake and lowest in the east.In the southern basin of the lake where the short core Qing-6is located, the recent average sedimentation rate is 0.1004cm/yr. Variations in effective precipitation recorded by the oxygen isotopes and grain size data durine the last 800 years are consistent with the glacial accumulation record form the Dunde and Guliya ice cores. A dry climate lasted for 300 years from 1200 AD to 1500 AD, followed by a wet period from 1500 to 1560 AD. The two dry periods, 1560 to 1650 AD and 1780 to 1850 AD, were the results of southwest monsoon weakening. The effective precipitation generally increased since 1650 AD due to the strengthening of the Asian South-west Monsoon, resulting in a wet period until the 1950s. Ex-cept the early stage, the Little Ice Age on the Plateau is characterized b y increased effective moisture. Organic mat-ter content, with nearly 200-year cycles, shows similar trend with the atmospheric delta earbon-14 before the 1850s, indi-eating that the bioproductivity responds to solar activity.     

Decoupling of surface and subsurface sutures in the Dabie orogen and a continent-collisional lithospheric-wedging model：Sr-Nd-Pb isotopic evidences of Mesozoic igneous rocks in eastern China

Based on the distribution of UHPM rocks on the surface in Sulu terrane, the surface suture between the NCB and SCB should be located along the Wulian fault (see Fig. 1, S1). However, based on the aeromagnetic data of eastern China, Li[1] first indicated that the subsurface suture between the NCB and SCB in the region east of the Tan-Lu fault should be located to the east of Nanjing City (see Fig. 1, S2), which south displaced about 400 km from the surface suture. This is contradicto…     

青藏高原西部燕山晚期花岗岩地球化学特征及其大地构造意义

对青藏高原西部燕山晚期花岗岩进行了地质、地球化学综合研究。结果表明 ,燕山晚期早白垩世花岗岩为 I型 ,形成于火山弧环境 ,岩石组合为石英二长闪长岩 -花岗闪长岩 -二长花岗岩 ,岩石系列为高钾钙碱性系列 ,A/ CNK<1,稀土元素含量中等 ,并且属轻稀土富集型 ,铕亏损不明显 ,L IL E有选择地得到富集 ,HFSE相对亏损 ;晚白垩世花岗岩为 S型 ,形成于同碰撞环境 ,岩石组合为二云母二长花岗岩 -二云母花岗岩 ,岩石系列为高钾钙碱性系列 ,但 A/CNK>1.1,稀土元素含量较低 ,铕亏损明显 ,微量元素中以 Rb和 F含量高为显著特征。为研究喀喇昆仑山构造演化提供了限定条件     

青海湖水位下降的生态环境效应

本文主要分析了青海湖水位下降所导致的湖区生态环境变化,指出青海湖流域的生态环境保护与综合治理任重道远.     

青海湖防沙治沙区沙棘光合特性与光响应特征研究

为研究青海湖固沙区人工沙棘的光合特性,以青海湖典型的固沙植物沙棘为研究对象,对其光合、蒸腾特性及主要影响因素进行了测定．结果表明,沙棘的光合具有明显的日变化规律,呈双峰型,光合作用速率P。在12：00左右出现峰值,为21．28μmol／（m^2·s）（文中均以CO2固定量为准）,日平均值为13．23μmol／（m^2·s）,具有“光午休”现象．蒸腾速率Tr与气孔导度Gs日变化动态也呈双峰型,光合作用有效辐射（Rpa）、空气温度丁日及水汽压强差（Pvd）变化规律基本一致,空气湿度（Hr）变化规律则相反;沙棘的Pn,Tr与Rpa,Ta,Gs及pvd呈显著相关,其中,Tr和Pvd影响最为显著;沙棘叶片的水分利用效率（Ewu）的光响应曲线表明,光合有效辐射达到400μmol／（m^2·s）时,Ewu最大．对青海湖防沙治沙与生态恢复有重要的参考价值．     

青海湖环湖区蝗虫与地貌类型关系的研究

蝗虫对青海湖环湖区的草地有相当严重的危害．摸清蝗虫发生与其生态条件之间的关系,是进行蝗虫有效防治的前提．不同类型的地貌通过其对水热条件的重新分配对蝗虫的发生有不同的影响．作者根据野外实地调查资料,就环湖区蝗虫发生与湖滨阶地、构造台地及山坡地等该区主要地貌类型与蝗虫密度的关系进行了初步研究．