大渡河流域生态环境建设问题

大渡河流域的环境脆弱性体现在地质地貌不稳定，土质差，土壤干旱现象严重，可归结为地质地貌的基底性脆弱和界面性脆弱以及气候的波动性脆弱。由于自然与人为因素的共同作用，这一地区生态环境已逐步恶化。从实地考察情况看，该地区生态治理工作虽然取得了一些突破，但也有不少问题乃至深层障碍尚未解决。在强调西部生态建设的新形势下，传统的土地利用方式和格局面临转型；因此，搞好综合区划，重新认识资源环境优势，逐步发展环境资源产业，引导传统农业和关联产业转型，是完成退耕还林还草任务，实现生态建设目标的基本对策和根本出发点。     

Soil sodium and potassium adsorption ratio along a Mediterranean–arid transect

Changes in the relationship between soil soluble ions and rainfall were studied on hillslopes at seven research sites that represent four climatic regions: Mediterranean, semi-arid, mildly arid and arid. At each site, soil samples were taken in several seasons and the ratio between the Na⁺ plus K⁺ content and the Ca²⁺ plus Mg²⁺ content (sodium and potassium adsorption RATIO=SPAR) was determined. In general, SPAR increased with increasing aridity except for the most arid site in which the soil contains a gypsic layer. The relationship between SPAR and rainfall was non-linear. An abiotic threshold, characterized by a sharp change in the SPAR, was found around the 200 mm isohyet: sites that receive less than 200 mm annual rainfall showed significantly higher SPAR than those that receive more than 200 mm, where SPAR was very low.     

A spectral index for land degradation mapping using ASTER data: Application to a semi-arid Mediterranean catchment

Flagrant soil erosion in Morocco is an alarming sign of soil degradation. Due to the considerable costs of detailed ground surveys of this phenomenon, remote sensing is an appropriate alternative for analyzing and evaluating the risks of the expansion of soil degradation. In this paper, we characterize the state of land degradation in a small Mediterranean watershed using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and ground-based spectroradiometric measurements. The two visible, the near-infrared and six shortwave infrared bands of the above sensor were calibrated using ground measurements of the spectral reflectance. Field measurements were carried out in the Saboun experimental basin located in the marl soil region of the Moroccan western Rif. The study leads to the development and evaluation of a new spectral approach to express land degradation. This index called Land degradation index (LDI) is based on the concept of the soil line derived from spectroradiometric ground measurements. In this study, we compare LDI and the spectral angle mapping (SAM) approaches to assess and map land degradation. Results show that LDI provides more accurate results for mapping land degradation (Kappa = 0.79) when compared to the SAM method (Kappa = 0.61). Validation and evaluation of the results are based on the thematic maps derived from the ground data (organic matter, clay, silt and sand) by kriging, DEM, slope gradient and photointerpretation.     

短期电力负荷的组合预测方法

电力负荷的影响因素很多,用单一预测模型进行预测时,因自身的局限,使其预测精度和稳定性不高。组合预测可以综合考虑各单一预测模型的结果,提高预测精度和稳定性。在电力预测中常用的指数平滑法、趋势分析法、Box-Jenkins时间序列法以及灰色预测法的单一预测基础上,建立组合预测模型,采用最小二乘法确定组合预测模型权重,并对某水电电力公司的上网负荷进行预测。实例表明,组合预测法能在短期电力预测中改善预测精度,提高预测的稳定性。     

利用电测深资料研究疏勒河流域中下游盆地的第四系

依据地层电性差异,研究河西走廊疏勒河流域中下游平原区的诸第四纪盆地中的第四系,提出了准第四系厚度的概念.用电测深资料推断了诸盆地的准第四系厚度、岩性结构、隐伏构造等,为该地区地下水勘查提供了基础性资料.     

遥感技术在750kV送电线路工程选线中的应用

应用美国Landsat ETM与法国SPOT2融合图像，对官厅一兰州东750kV送电线路工程进行了遥感工程地质调查。通过遥感信息的提取，对线路走廊带的地形地貌、岩土类型、地质构造、不良地质与特殊地质等进行了遥感解析，对区域工程地质复杂程度进行了分区与评价，对拟选线路方案进行了评价与比选，从工程地质的角度分析了拟选线路的优劣，提出了相应的路线调整建议，为最终线路的确定和设计提供了准确可靠的基础资料。     

The anomalous reactions of the geomagnetic horizontal field transfer functions before Tangshan earthquake

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青藏公路南段岛状冻土区内冻土环境变化

将９０年代的勘探，钻孔测温和地面综合调查等实测资料与７０年代对比，发现青藏公路南段状多年冻土区内的冻土退化和生态环境变化相当明显，表现为岛状多年冻土南界北移１２ｋｍ，多年冻土岛总面积减少７％，沼泽化湿地面积缩小约三分之一，沼泽化草罗向草原化草甸逐步转化，湖塘和洼地中的水生植物群落向湿。中生植物群落演替。草场退化亚，少数地段土地沙化，形成活动性砂丘，目前区内的生态环境正向劣势方面发展。     

Human impact in a tourist karstic cave (Aracena, Spain)

 Human intrusion on the Cave of Marvels (southwestern Spain) has produced a series of effects on the water (fall in the level of the pools due to pumping from nearby wells), the air (increased temperature and CO₂ concentration as well as decreased relative humidity) and the rock. In addition, plant colonization, favored by the lighting system, has irreversibly altered numerous speleothems. The processes of degradation are especially intense in the sectors with less air volume and limited ventilation. The analysis of the cave deposits by scanning electron microscopy and thin section analysis revealed that floral pollution constitutes one of the most aggressive agents against the calcite and aragonite precipitates, being responsible for biochemical and biophysical degradation of the first order. Received: 18 December 1995 · Accepted 10 September 1996     

The effects of loess erosion on soil nutrients, plant diversity and plant quality in Negev desert wadis

Severe erosion, initiated by climatic changes during the Late Pleistocene-Early Holocene period and resultant declines in dust deposition, causes the formation of waterfalls during the winter floods in many wadi systems in the central Negev desert of Israel. In some areas, erosion of the original loess substrate has been complete, so that the underlying rock has been exposed. We examined the effects of this erosion in four wadis in the central Negev desert on soil nutrients, plant community structure and plant quality. We predicted that erosion has caused reductions in soil nutrients. Reductions in soil nutrients should result in reductions in plant cover. Furthermore, reduced soil nutrient availability should cause reductions in the nutrient status and quality of the plants growing there. In addition to the loss of biodiversity that may result, this erosion may result in economic hardship for the Bedouin peoples whose herds depend on these resources. In this study, there were significant negative effects of erosion on soil organic carbon, nitrate nitrogen and water-holding capacity, but not on soil phosphorus, conductivity or pH. Furthermore, there was a negative effect of soil erosion on an overall measure of soil quality derived from a principal components analysis in three of the four wadis we studied. Erosion resulted in an increase in plant species richness and significantly altered plant community structure in eroded areas of wadis. Increased plant species richness in eroded sites is consistent with the intermediate disturbance hypothesis of plant community structure. Plants growing in eroded areas did not differ in two quality indices (nitrogen content and digestibility), although plants typical of eroded areas had significantly lower levels of common digestion inhibitors (total polyphenols) and toxins (alkaloids) than plants from undisturbed sites. These last-mentioned results are contrary to our prediction and are consistent with the notion that plants growing in disturbed (e.g. eroded) sites maximize growth at the expense of investments in defense.