Phytoplanktonic desmids community in Donghu Lake, Wuhan,China

1 INTRODUCTION Donghu Lake (30o33′N, 114o23′E) is a shallow medium sized freshwater lake in Wuhan City, Hubei Province, China and about 5 kilometers away from the Changjiang (Yangtze) River. Before the 1960s, the water surface area was about 27.8 km2. The lake water was clear and the pH ranged from 6 to 7. The shallow area of the lake abounded with macrophytes. The phytoplanktonic and peripheral desmids were very abundant also in this lake. In the late 1960s, Donghu Lake with tota…     

On Phase Shifts In Periodic Well Fluctuations

Summary. For the case of a well completely penetrating a confined aquifer of infinite extent, an analysis is made of the flow processes in the well-aquifer system due to periodic pressure variations like earth tides and barometric tides. It is shown that the earth tides lead to well fluctuations with a negative phase difference (phase lag), while the barometric tides cause well fluctuations with a positive phase difference (phase advance).
In both cases the amplitudes and phases of the well fluctuations depend on frequency and are therefore different for the individual components of the tidal spectra. These frequency characteristics need to be studied more carefully than is the case now. A schematic model of a device is described that could not only be used for this purpose, but also for the determination of the specific storage S _s and the conductivity k. the method would be closely related to the well-known slug or bail tests.     

Experimental Evidence of Critical Sensitivity in Catastrophe

The paper presents an experimental study on critical sensitivity in rocks. Critical sensitivity means that the response of a system to external controlling variable may become significantly sensitive as the system approaches its catastrophic rupture point. It is found that the sensitivities measured by responses on three scales (sample scale, locally macroscopic scales and mesoscopic scale) display increase prior to catastrophic transition point. These experimental results do support the concept that critical sensitivity might be a common precursory feature of catastrophe. Furthermore, our previous theoretical model is extended to explore the fluctuations in critical sensitivity in the rock tests.     

Radial growth of Tamarix ramosissima responds to changes in the water regime in an extremely arid region of northwestern China

The response of radial growth of tamarisk (Tamarix ramosissima) growing on the shore of West-Juyan Lake, on the Heihe River in northwestern China, to changes in the lake’s water regime was studied using tree-ring chronologies, principal components (PC) analysis, and classical correlation analysis. The first PC accounted for 53.3% of the total variance and reflected a common growth response at different sites. Correlation analysis indicated that fluctuations in the lake’s water level during the growing season (May–August) was primarily responsible for variations in the radial growth of tamarisk and explained more of the variance at low-lying sites than at higher sites. The second PC accounted for 30.7% of the total variance and revealed distinct differences in growth response between low-lying sites and those on higher ground. Total annual precipitation played an important role in radial growth of tamarisk at the higher sites. The spatial pattern in the tree-ring chronologies for different sites was performed in the temporal pattern of the tree-ring chronology at the same site. Other factors such as microtopography, soil salinity, sand activity, and browsing by herbivores also affected the radial growth of tamarisk. The diversity in responses to the maximum water table depth for tamarisk in the study area appears to have been caused by local variations in precipitation, which can compensate to some degree for the inability of a plant’s roots to reach the water table.     

乡村聚落群结构分形性特征研究——以浙江省平湖县为例

利用概率累积曲线与频率曲线分析浙江省平湖县乡村聚落群的聚落组成特点 ,初步认为本区聚落群由发展聚落、现存聚落、残遗聚落所组成。应用Hausdorff维数 ,以乡为单位 ,测算并分析了平湖县乡村聚落群的等级体系结构与组成特征 ;在乡级聚落群体系中 ,残遗聚落与发展聚落不属于无标度区 ;在县级聚落群体系中 ,残遗聚落不属于无标度 ,大多数发展聚落属于无标度区。定性分析了乡村聚落群结构分形性形成演化过程 ,表明聚落分形为多重分形 ,聚落群体系的分形性是系统自组织有序性的系统体现     

气候与地表覆被变化对梭磨河流域水文影响的分析

分析了1960～1990年长江上游梭磨河流域气候和地表覆被变化及其对流域水文的影响。30年来，流域降水有所增加，有林地面积1957～1974年大幅下降，以后有所回升。有林地每公顷蓄积量由1957年的423m^3下降到1998年的177m^3，40年来林地质量不断下降，流域水文发生了明显的变化；年均流量自1972年以来不断上升，洪水频率、洪峰流量和土壤侵蚀模糊明显增加。     

西藏纳木错末次盛冰期以来的古植被、古气候和湖面变化

西藏纳木错湖相沉积的U系、14C年龄和孢粉分析结果表明,纳木错沿岸的拔湖约1.5～8.3m和8.3～15.6m的T1和T2分别形成于末次盛冰期以来约(11.81±0.10)～(4.22±0.09)kaB.P.期间和(28.2±2.8)kaB.P.左右。该套湖相层的孢粉组合、地层和湖岸堤的分布表明,在末次盛冰期期间,纳木错湖面主要波动于拔湖12～20m之间,但湖面最低可达拔湖约8m。区域植被主要为以蒿和莎草科为主、含松和桦的草原。在约11.8～4.2kaB.P.期间,湖面波动于拔湖2～9m之间,区域气候整体较为暖湿。其中全新世大暖期出现在约8.4～4.2kaB.P.期间,气候温暖湿润,区域出现针叶林或针阔叶混交林,气温可能比现今高约5℃,降水量可能比现今多100～200mm,湖面扩张并升高,最高可达拔湖约10m。     

长江三峡永久船闸高边坡预应力锚索监测

简要介绍了三峡工程永久船闸二期高边坡350 t级预应力锚索监测工程情况。监测结果表明,测力计张拉实测荷载与千斤顶加荷相差率为2.51 %,锁定损失率为2.46 %,锁定后损失率为11.81 %,总损失率为14.45 %。其荷载变化特征可总体归纳为下降稳定性、周期变化性和折线突降性三种类型,群锚效应观测无明显反应。在测力计的标定和安装过程中显示,基座钢垫板的尺寸、刚度及表面加工平整度对测力计的受力状态影响较大。     

地球自转十年尺度波动与核幔耦合的可能机制

简要介绍了地球自转变化的一般规律可能的地球物理激发因素，十年尺度波动与核幔边界耦合之间的联系，以及几种可能的核幔耦合机制。强调了地震波探测手段对于获限地球内部信息的重要性，同时指出将空间大地测量，重力测量和地磁怀地球物理学方面的理论与模型研究相结合，对于最终分析和确认地球自转变化中的各种信息及其激当因素是十分重要的。     

Lake Sequence Stratigraphy of the Shahejie Formation in the Zhanhua Hollow, Shandong Province

Two sequences can be identified in the sedimentary strata of the lower Tertiary ShahejieFormation in the Zhanhua hollow. The lowstand, lake-transgressive and highstand systemstracts were formed under the control of ancient structure, palaeotopography, palaeoclimate, sed-iment supply, marine-transgression, and so on. In the paper the authors present a composite se-quence stratigraphical section of the Shahejie Formation in this area, and expound the bounda-ries of parasequences, parasequences set and systems tracts and evolutions of lake sequencestratigraphy and sedimentology and discuss various factors controlling the lake level fluctuation.The differences between lake and marine sequence stratigraphy are also indicated in the paper.The lake sequence stratigraphical study should be based on a synthetic analysis of structural evo-lution, palaeomagnetism, palaeoclimatic changes, geological Well logs, seismic and logging data,palaeontological data, global sea level changes, and so on. The sequence stratigraphical evolutionis closely related to the formation, development and elimination of the whole basin and thesedimentary process.