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1.
塔里木河下游土地覆盖动态变化分析   总被引:13,自引:1,他引:12  
利用80-90年代的TM影响数据,借助GIS分析了新疆塔里木河下游典型生态调查区内土地利用/土地覆盖现状及动态变化,并对塔河下游土地开发效果进行了对比分析。结果显示,耕地和城镇居住住用地的增加完全来源于对草地的开垦和对荒漠胡杨林的占用。同时,由于沙化、盐咸化等自然因素的影响和因对水资源的不合理利用所产生的土壤次生盐渍化的共同作用,控制着区内生态环境不断恶化的总体态势。  相似文献
2.
Unplanned urban expansion of the new urban cluster of Rosetta City, Egypt is reaching a critical stage. This unplanned expansion of slum areas threatens the land on which the high quality palm trees, by which Rosetta region is known, are cultivated. This research is concerned with studying the manner, rate, extent and impact of the expansion of the urban cluster of Rosetta City. A multi-temporal analysis of mainly the limits of the built up urban areas and their surrounding land cover is the main evaluation technique. By using Geographic Information Systems, it was possible to study the geographic base of the concerned area. An increase in area of the urban clusters of about 0.1 km2 occurred from 1917–1945, and a second increase of over 0.07 km2 occurred from 1945–1963. Just after the end of the Second World War, an abrupt increase took place in 1963–1993 that reached 1.7 km2. The majority of all the urban expansion was unplanned. By studying the topographic map of Rosetta city and the urban clusters on the western bank of the river Nile, it was found that most of the urban conglomeration of the city is located on relatively elevated land. The western part of the urban area is of an elevation varying around 5.0 m, and inclining with moderate slope towards the eastern edge of the city adjacent to the river Nile. The urban expansion on inclined land has caused severe problems with the sanitary drainage, as the city lacks any sanitary drainage systems. Sanitary drainage currently operates through precipitation trenches. Sanitary sewage gather beneath the ground forming continuos streams which reach the basements of many of the monuments present.  相似文献
3.
Due to human impact under climatic variations, western part of Northeast China has suffered substantial land degradation during past decades. This paper presents an integrated study of expansion process of salinized wasteland in Da’an County, a typical salt-affected area in Northeast China, by using Geographic Information Systems (GIS) and remote sensing. The study explores the temporal and spatial characteristics of salinized wasteland expansion from 1954 to 2004, and land use/cover changes during this period. During the past 50 years, the salinized wasteland in study area have increased by 135,995 ha, and in 2004 covers 32.31% of the total area, in the meantime grassland has decreased by 104,697 ha and in 2004 covers only 13.15% of the study area. Grasslands, croplands and swamplands were found the three main land use types converted into salinized wasteland. Land use/cover changes shows that between 1954 and 2004, 48.6% of grasslands, 42.5% of swamplands, and 14.1% of croplands were transformed into salinized wasteland, respectively. Lastly, the major factors influencing salinized wasteland expansion and land use/cover changes were also explored. In general, climatic factors supplied a potential environment for soil salinization. Human-related factors, such as policy, population, overgrazing, and intensified and unreasonable utilization of land and water resources are the main causes of salinized wasteland expansion.  相似文献
4.
A study of the area, including Rosetta city and the estuary of the river Nile (Rosetta branch), has been carried out for assessment of the impact of sea level rise (slr). A geographic information system (GIS) has been built including layers of land use, topography, archeological sites, land cover and population. Analysis of data has been carried out to assess vulnerability of various land use and land cover classes to the impact of sea level rise.Because the area under study has geomorphic relief profiles just over the sea level, inundation of total land could reach 26% of total study area due to only half a meter rise in sea level. This lost area includes 32% of urban clusters mainly used for human shelter and contains 52% of present monuments, 25% of valuable high quality dense palm trees cultivation, 75% of beaches and 19% of lands suitable, 25% of valuable high quality dense palm trees cultivation, 75% of beaches and 19% of lands suitable for agricultural reclamation (although suffering from salt water intrusion and soil salinization). This is expected to cause a significant impact on the present population, economic activities, total regional revenue, and also on tourism. At 1.1 m sea level rise, 72% to total study area could be inundated. This area contains all beaches, half of the palm cultivation, 43% of total urban clusters, which includes 81% of the monumental sites and historic buildings.Other environmental problems such as solid waste management, sanitary disposal network, deteriorating conditions of some monumental structures, in addition to the sea level rise act negatively on the environmental quality of the urban community. Future plans for urban expansion in the area must be studied carefully in order to preserve valuable palm lands and maintain and protect monuments and historic sites which help the promotion of tourism. An environmental management program is essential for upgrading tourism, promoting urban development and protecting coastal lands.  相似文献
5.
遥感在生态与环境监测中的主要应用领域   总被引:5,自引:2,他引:3  
遥感是一种以物理手段、数学方法和地学分析为基础的综合应用技术 ,具有宏观、综合、动态和快速的特点。在解决宏观尺度的环境问题时 ,卫星遥感可重复获取多种空间、不同时相和不同波谱分辨率的地球信息 ,是适宜于调查和研究这些主题的唯一的、最有效的工具。本文通过对遥感在环境与生态监测的主要应用领域进行概要阐述 ,旨在抛砖引玉 ,推动遥感在环境与生态监测中的广泛应用。  相似文献
6.
Agricultural activities, especially reclamation, are considered major threats to the wetland ecosystems in Sanjiang Plain, the largest concentrated area of the freshwater wetlands in China. In the past decades, the area of the cultivated land and its grain production have been increased at the cost of wetlands shrinkage. The large-scale land reclamation severely affected the ecosystems in this region. However, such effects at the regional scale are seldom evaluated quantitatively. We used three datasets of LANDSAT MSS and/or TM imagery to estimate the area changes and the transition of land use types from 1980 to 2000. We also valued changes in ecosystem services delivered by each land category using value coefficients published by Costanza et al. [Nature 387, 1997, 253–260]. Sensitivity analysis suggested that these estimates were relatively robust. Finally, the contribution of various ecosystem functions was ranked to the overall value of the ecosystem services in this study. According to our estimates, the total annual ecosystem service values in Sanjiang Plain have declined by about 40% between 1980 and 2000 ($156284–182572.18 million in total over 20 years). This substantial decline is largely attributed to the 53.4% loss of wetlands. For individual ecosystem functions, waste treatment, water supply and disturbance regulation account for more than 60% to the total ecological values. During those two decades, the contribution of disturbance regulation, cultural and recreation decreased, while the contribution of water regulation, nutrient cycling, food production, raw materials and climate regulation increased during the same period. We also put forward a few proposals concerning the future land use policy formulation and sustainable ecosystems. They are adjusting the ‘food first’ agricultural policy, establishing more nature reserves for wetlands, creating systems for the rational use of water, harnessing the degraded cultivated land and encouraging eco-tourism.  相似文献
7.
The Vegetation of Wet Meadows in Relation to Their Land-use   总被引:4,自引:0,他引:4  
Wetland biomonitoring approaches are needed to determine when changes in response to stressors are occurring and to predict the consequences of proposed land-use changes. These approaches require an understanding of shifts in biota that occur in response to land-use, data that are lacking for most kinds of wetlands. Changes in floristic composition corresponding to land-use differences at multiple scales (site to 2500 m radius) were characterized for 40 wet meadows associated with prairie glacial marshes in Minnesota (U.S.A.). In general, guild was more useful than species composition for indicating land-use impacts. Site impacts (stormwater, cultivation) and landscape disturbance (agriculture and urbanization, combined), coincide with a reduction in native graminoid and herbaceous perennial abundance (e.g., Carex lasiocarpa, Calamagrostis canadensis, Spartina pectinata). This vegetation is replaced with annuals (e.g, Bidens cernua, Polygonum pensylvanicum) in recently cultivated sites or introduced perennials (e.g., Phalaris arundinacea, Typha angustifolia) and floating aquatics (lemnids) in stormwater impacted wetlands. Ditches also reduce native perennial importance and increase perennials, but only when they are in highly impacted landscapes.  相似文献
8.
Benthic algal assemblages, water chemistry, and habitat were characterized at 25 stream sites in the Willamette Basin, Oregon, during low flow in 1994. Seventy-three algal samples yielded 420 taxa — mostly diatoms, blue-green algae, and green algae. Algal assemblages from depositional samples were strongly dominated by diatoms (76% mean relative abundance), whereas erosional samples were dominated by blue-green algae (68% mean relative abundance).Canonical correspondence analysis (CCA) of semiquantitative and qualitative (presence/absence) data sets identified four environmental variables (maximum specific conductance, % open canopy, pH, and drainage area) that were significant in describing patterns of algal taxa among sites. Based on CCA, four groups of sites were identified: streams in forested basins that supported oligotrophic taxa, such as Diatoma mesodon;small streams in agricultural and urban basins that contained a variety of eutrophic and nitrogen-heterotrophic algal taxa; larger rivers draining areas of mixed land use that supported planktonic, eutrophic, and nitrogen-heterotrophic algal taxa; and streams with severely degraded or absent riparian vegetation (> 75% open canopy) that were dominated by other planktonic, eutrophic, and nitrogen-heterotrophic algal taxa. Patterns in water chemistry were consistent with the algal autecological interpretations and clearly demonstrated relationships between land use, water quality, and algal distribution patterns.  相似文献
9.
In Maryland, U.S., an interim framework has recentlybeen developed for using biologically based thresholds, or `biocriteria', to assess the health of nontidal streams statewide at watershed scales. The evaluation of impairment is based on indices of biological integrity from the Maryland Biological Stream Survey (MBSS). We applied logistic regression to quantify how the biotic integrity of streams at a local scale is affected by cumulative effects resulting from catchment land uses, point sources, and nearby transmission line rights-of-way. Indicators for land use were developed from the remote sensing National Land Cover Data and applied at different scales. We determined that the risk of local impairment in nontidal streams rapidly increases with increased urban land use in the catchment area. The average likelihood of failing biocriteria doubled with every 10% points increment in urban land, thus an increase in urban land use from 0 to 20% quadruples the risk of impairment. For the basins evaluated in this study, catchments with more than 40–50% urban land use had greater than 80% probability of failing biocriteria, on average. Inclusion of rights-of-way and point sources in the model did not significantly improve the fit for this data set, most likely because of their low numbers. The overall results indicate that our predictive modeling approach can help pinpoint stream ecosystems experiencing or vulnerable to degradation.  相似文献
10.
This study was conducted to determine status of heavy metals in agricultural soils under different patterns of land use. A total of 38, 40 and 45 soil samples for bare vegetable field, greenhouse vegetable field, and grain crop field were respectively taken from surface layer (0–20 cm) from selected experimental areas away from suburbs of ten counties (or districts or cities) in four provinces or municipalities of Huabei plain in north China. Information of crop production history, including varieties, rotation systems and fertilizer use, at the corresponding sampling sites was surveyed. Soil total Cu, Zn, Cd, Pb, Cr, As and Hg were measured. The results showed that the contents of total Cu, Zn, Cd, Pb, Cr, As, and Hg in the soil samples, especially soil total Cu and Zn contents, were higher in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. Long-term use of excessive chemical fertilizers and organic manures in the bare vegetable field and the greenhouse vegetable field contributed to the accumulation of Cu, Zn, and other heavy metals in the soils. The contents of total Cu, Zn, and other heavy metals in soils increased with increasing vegetable production history of the research areas. In comparison with the grain crop field, the comprehensive pollution indices of the seven soil heavy metals and the single-factor pollution indices of soil Zn, Cu, Cd, Cr, and Hg based on the second criterion of Environmental Quality Standard for Soils were significantly higher in the bare vegetable field and the greenhouse vegetable field. Soils from the greenhouse vegetable field were slightly contaminated according to the comprehensive pollution index, and soils from the bare vegetable field and the grain crop field were at the warning heavy metal pollution level. The soils were contaminated with Cd according to the single-factor pollution index. The Cd pollution was relatively more serious in the bare vegetable field and the greenhouse vegetable field than that in the grain crop field. The soils selected with different land use patterns were not contaminated with Zn, Cu, Pb, Cr, As and Hg.  相似文献
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