Effect of environmental factors on the flora of alluvial fans in southern Sinai

The purpose of this study was to elucidate the floristic and structural characteristics of simple alluvial fan vegetation of southern Sinai and to relate them to environmental variation. The main question addressed was: how does the floristic composition of fan habitats, species richness and life-form vary in relation to environmental change? Thirty-seven alluvial fans, randomly selected in two mainwadis(WadiFeiran andWadiDahab) were analysed quantitively. Two-way Indicator Species Analysis (TWINSPAN) classification and Canonical Correspondence Analysis (CCA) were applied in successive stages of the data analysis to describe vegetational variation in relation to physical gradients. Seven main clusters of fans were defined on the basis of environmental variation. These clusters are divided into three main groups of species richness. Species richness varied along a moisture gradient. The richest fans were the driest habitats, indicating that maximum species richness did not occur at high moisture availability. The moisture gradient is a complex gradient correlated with elevation, slope, climatic aridity, soil texture and the nature of the soil surface. Fine sand, silt plus clay and calcium carbonate showed significant differences between the internal groups and subgroups of the first and second level of the TWINSPAN classification.     

Chemical composition of upper crust in eastern China

In an area of 3.3×10⁶ km² within eastern China, 28 253 rock samples were collected systematically and combined into 2718 composite samples which were analyzed by 15 reliable methods using national preliminary certified reference materials (CRMs) for data quality monitoring. The average chemical compositions of the exposed crust, the sedimentary cover and the exposed basement as well as the upper crust for 76 chemical elements in eastern China are given. A key basic geology projcct supported by Ministry of Geology and Mineral Resources of China.     

吐哈盆地西南缘水西沟群古气候演变特征及其层序地层学意义

通过对水西沟群(J1-2sh)古植物、古孢粉化石组合特征等系统的研究，对八道湾组(J1b)、三工河组(J1s)、西山窑组(J1x)古气候类型进行了区分；并据此认为西山窑组(J1x)为一套气候地层层序，相应划分为四个体系域：即低水位、湖泊扩张，高水位及湖泊收缩体系域。再结合一些岩性岩相等特殊标志，对十红滩东部外围地层层序进行了划分，结果与十红滩矿区地层层序本质是一致的。     

金沙江下游白鹤滩水电站岩体结构的建造特征

拟建的白鹤滩水电站的坝基为峨眉山玄武岩。峨眉山玄武岩由火山熔岩类、火山碎屑熔岩类、火山碎屑岩类和沉积火山碎屑岩类所组成。火山熔岩又可划分为斜斑玄武岩、块状玄武岩和杏仁状玄武岩;火山碎屑岩包括集块岩、火山角砾岩以及凝灰岩;而沉积火山碎屑岩类则由沉火山角砾岩和沉凝灰岩所组成。不同类型岩石的结构构造、矿物成分和形成环境不同,导致它们的岩石力学性质和工程性能也不相同。块状玄武岩、斜斑玄武岩和沉积火山碎屑熔岩的抗压强度和抗风化能力都比较大,因而具有很好的工程地质稳定性;杏仁状玄武岩、火山碎屑熔岩的抗压强度稍低,但抗风化能力很好,因此也具有较好的工程地质稳定性;而火山碎屑岩包括火山角砾岩、凝灰岩的抗压强度和抗风化能力都很低,往往形成岩体中的软弱夹层,工程地质稳定性较差。     

A Modeling Study of the Effects of Anomalous Snow Cover over the Tibetan Plateau upon the South Asian Summer Monsoon

The effect of anomalous snow cover over the Tibetan Plateau upon the South Asian summer monsoon is investigated by numerical simulations using the NCAR regional climate model (RegCM2) into which gravity wave drag has been introduced. The simulations adopt relatively realistic snow mass forcings based on Scanning Multi-channel Microwave Radiometer (SNINIR) pentad snow depth data. The physical mechanism and spatial structure of the sensitivity of the South Asian early summer monsoon to snow cover anomaly over the Tibetan Plateau are revealed. The main results are summarized as follows. The heavier than normal snow cover over the Plateau can obviously reduce the shortwave radiation absorbed by surface through the albedo effect, which is compensated by weaker upward sensible heat flux associated with colder surface temperature, whereas the effects of snow melting and evaporation are relatively smaller.The anomalies of surface heat fluxes can last until June and become unobvious in July. The decrease of the Plateau surface temperature caused by heavier snow cover reaches its maximum value from late April to early May. The atmospheric cooling in the mid-upper troposphere over the Plateau and its surrounding areas is most obvious in May and can keep a fairly strong intensity in June. In contrast, there is warming to the south of the Plateau in the mid-lower troposphere from April to June with a maximum value in May.The heavier snow cover over the Plateau can reduce the intensity of the South Asian summer monsoon and rainfall to some extent, but this influence is only obvious in early summer and almost disappears in later stages.     

Variographic analysis of tropical forest cover from multi-scale remotely sensed imagery

Tropical forest mapping is one of the major environmental concerns at global and regional scales in which remote sensing techniques are firmly involved. This study examines the use of the variogram function to analyse forest cover fragmentation at different image scales. Two main aspects are considered here: (1) analysis of the spatial variability structure of the forest cover observed at three different scales using fine, medium and coarse spatial resolution images; and (2) the study of the relationship between rescaled images from the finest spatial resolution and those of the medium and coarse spatial resolutions. Both aspects are analysed using the variogram function as a basic tool to calculate and interpret the spatial variability of the forest cover. An example is presented for a Brazilian tropical forest zone using satellite images of different spatial resolutions acquired by Landsat TM (30 m), Resurs MSU (160 m) and ERS ATSR (1000 m). The results of this study contribute to establishing a suitable spatial resolution of remotely sensed data for tropical forest cover monitoring.     

Assessing land use/cover changes: a nationwide multidate spatial database for Mexico

A nationwide multidate GIS database was generated in order to carry out the quantification and spatial characterization of land use/cover changes (LUCC) in Mexico. Existing cartography on land use/cover at a 1:250,000 scale was revised to select compatible inputs regarding the scale, the classification scheme and the mapping method. Digital maps from three different dates (the late 1970s, 1993 and 2000) were revised, evaluated, corrected and integrated into a GIS database. In order to improve the reliability of the database, an attempt was made to assess the accuracy of the digitalisation procedure and to detect and correct unlikely changes due to thematic errors in the maps. Digital maps were overlaid in order to generate LUCC maps, transition matrices and to calculate rates of conversion. Based upon this database, rates of deforestation between 1976 and 2000 were evaluated as 0.25 and 0.76% per year for temperate and tropical forests, respectively.     

Fifty-thousand-year vegetation and climate history of Noel Kempff Mercado National Park, Bolivian Amazon

Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO₂ concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 ¹⁴C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 ¹⁴C yr B.P., coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2-3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.     

黄河流域坡高地系统最小生态需水研究

以保护和恢复流域坡高地生态系统为目的，对坡高地最小生态需水问题进行研究，提出了坡高地生态需水和生态缺水的计算方法。以黄河流域为实例，在GIS和遥感技术支持下对坡高地最小生态需水量和缺水量进行了计算，并从时空两个尺度揭示了黄河流域坡高地生态系统最小生态需水的变化规律，研究成果可为流域生态环境建设和水资源合理配置提供依据。