Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China   总被引：7，自引：0，他引：7  

Pingjiu Zhang  Lianqing Li  Genxing Pan  Jingchen Ren 《Environmental Geology》2006,51(4):609-619

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.  相似文献   

New Generation of Probabilistic Seismic Hazard Assessment for the Area Cologne/Aachen Considering the Uncertainties of the Input Data     

G. Grünthal  R. Wahlström 《Natural Hazards》2006,38(1-2):159-176

A new earthquake catalogue for central, northern and northwestern Europe with unified M_w magnitudes, in part derived from chi-square maximum likelihood regressions, forms the basis for seismic hazard calculations for the Lower Rhine Embayment. Uncertainties in the various input parameters are introduced, a detailed seismic zonation is performed and a recently developed technique for maximum expected magnitude estimation is adopted and quantified. Applying the logic tree algorithm, resulting hazard values with error estimates are obtained as fractile curves (median, 16% and 84% fractiles and mean) plotted for pga (peak ground acceleration; median values for Cologne 0.7 and 1.2 m/s² for probabilities of exceedence of 10% and 2%, respectively, in 50 years), 0.4 s (0.8 and 1.5 m/s²) and 1.0 s (0.3 and 0.5 m/s²) pseudoacclerations, and intensity (I₀ = 6.5 and 7.2). For the ground motion parameters, rock foundation is assumed. For the area near Cologne and Aachen, maps show the median and 84% fractile hazard for 2% probability of exceedence in 50 years based on pga (maximum median value about 1.5 m/s²), and 0.4 s (>2 m/s²) and 1.0 s (about 0.8 m/s²) pseudoaccelerations, all for rock. The pga 84% fractile map also has a maximum value above 2 m/s² and shows similarities with the median map for 0.4 s. In all maps, the maximum values fall within the area 6.2–6.3° E and 50.8–50.9° N, i.e., east of Aachen.  相似文献   

Karst groundwater protection in the Kupa River catchment area and sustainable development   总被引：1，自引：0，他引：1  

B. Biondić  R. Biondić  S. Kapelj 《Environmental Geology》2006,49(6):828-839

One of the most significant water resources in the Republic of Croatia is the catchment area of the Kupa River, located in the region bordering the Republic of Slovenia. About 88% of the total amount of water in this catchment originates in Croatia and just 12% from Slovenia; therefore, the largest part of the catchment area (about 1000 km²) is on the Croatian side of the border. It is a typical karst area of the Dinarides with aquifers characterized by a relatively rapid water exchange, high groundwater flow velocities and aquifers open to human impact from the surface. Consequently, the aquifers are highly vulnerable and at risk. Due to the availability of large quantities of high-quality spring water (about 6 m³/s), the entire area has a strategic importance within the context of any future development strategy pertaining to the western part of Croatia. The catchment area on the Croatian side was investigated using a wide range of research methods that included a classical hydrogeological approach, the detailed hydrologic calculation of water balance to the hydrogeochemical analyses and modelling. The objective was to determine protection zones and protection measures for the whole area. The difficulties are increased due to the fact that the karst catchment area is crossed by major traffic corridors, oil pipelines and a railway and that many settlements and a highly developed wood industry are present. The combination of protecting water resources with adequate prevention measures and necessary remedial activities that should satisfy the very strict requirements necessary for the protection of the karst aquifers while still allowing for present and future human activities is difficult – but not impossible – to achieve. One good example is the present highway with a closed dewatering system and waste water treatment before the water passes into the karst underground system.  相似文献   

Regional disparity in the changes of agricultura land use intensity in China during 1980-2002     

LIU Chengwu LI Xiubin 《地理学报(英文版)》2006,16(3):286-292

Based on the cost-benefit data （1980-2002） of farm products and China Agriculture Yearbooks, this paper studies the regional disparity in the changes of the agricultural land use in China during the period 1980-2002 from three aspects such as the degree of intensity, the sown area and the abandoned farmland. The results show that： （1） The degree of intensity of land use in the westena region during 1980-2000 has a strong uptrend, but in the eastern and central regions the degree of intensity descends obviously and has shown a continuous downtrend since 1997. （2） The total sown area shrinks notably in the eastern region, while it enlarges constantly in the western region. （3） The sown area in the eastern, central and western regions has gone through a similar cyclic process： down （1980-1985）-up （1985-1991）-down （1991-1994）-up （1994-1999）-down （1999-2002）. However, there are obvious differences in amplitude variation and tendency among them. The sown area has shrunk in the eastern region and expanded in the central and western regions especially before 1999. （4） The most cases of abandoned farmland are reported in the central region, the second in the eastern region and the least in the western region. The abandonment phenomena chiefly occurred during 1992-1995 in the eastern region, and during 1998-2002 in the central region.  相似文献   

紫色丘陵区不同侵蚀沉积地段土壤结构特征     

况福虹  何毓蓉朱波 张保华 《山地学报》2006,24(B10):71-76

以中国科学院盐亭紫色土农业生态试验站小流域为例，研究不同土壤侵蚀沉积地段（斜坡和沟谷不同部位）的土壤结构特征，以了解侵蚀沉积对土壤结构的影响。结果表明，在植被覆盖较好的坡体顶部，土壤侵蚀较弱，团聚度达到30．1％，MWD变化为3．4mm，土壤结构良好；沟谷底部由于沉积而有较多细土物质并具有适宜的水分条件，有利于土壤团聚体的形成，结构状况亦较好，团聚度达到50．3％，结构保持率为35．4％；而坡腰侵蚀较严重，团聚度仅为13．6％，结构保持率为14．1％，土壤结构状况较差。  相似文献   

Factors influencing the presence or absence of tributary-junction fans in the Iberian Range, Spain     

Amelia Gmez-Villar  Javier lvarez-Martínez  Jos M. García-Ruiz 《Geomorphology》2006,81(3-4):252-264

This paper analyses the factors which influence the presence or absence of tributary-junction fans in the Iberian Range, northern Spain. Two valleys were selected, both characterised by wide variations in lithology, altitude, land use and plant cover. Two groups of factors were studied: those related to the internal characteristics of the drainage basins, which particularly control sediment generation; and those related to the characteristics of the depositional area which control accommodation space and main river power. Among the internal factors, the development of alluvial fans was related to: (i) the capacity of the basin to yield large volumes of sediment, (ii) the occurrence of intense human pressure until recent times, a good indicator of sediment yield, and (iii) the capacity of the basin to quickly increase discharge during rainstorms (discharge density and torrentiality). It is suggested that the areas that were intensively cultivated in the past, and have therefore been affected by intense erosion, have played a decisive role on the development of alluvial fans. This would imply that many of these alluvial fans have a relatively recent origin, perhaps related to the beginning of a widespread deforestation. The basins without alluvial fans are characterised by relatively steep hillslope gradients (that is, slopes that never were subjected to historical cultivation), low drainage densities and dense forest and shrub cover, mostly coinciding with high altitude basins composed of quartzite and shale bedrocks. Regarding the external factors, the shape, size and longitudinal gradient of the main river to which the fans are tributary are the most relevant conditioning factors determining the development of alluvial fans.  相似文献   

Gold mining in Ghana's forest reserves: a report on the current debate     

Gavin Hilson  Frank Nyame 《Area》2006,38(2):175-185

This paper examines the debate surrounding a recent decision made by the Ghanaian government to permit gold exploration – and potentially, mining – in 'protected' forest reserves. In 2001, four mining companies were awarded mineral exploration concessions in forested regions of the country, and have since put forward applications to mine for gold. Notwithstanding the sharp divide in opinion on the issue, the continued uncertainty surrounding the implications of the proposed activities makes further research on the ground imperative in the short term. Work aiming to elicit indigenous perspectives on the projects, as well as research that facilitates dialogue between and/or among stakeholder parties, should be prioritized.  相似文献   

Pre-collapse identification of sinkholes in unconsolidated media at Dead Sea area by 'nanoseismic monitoring' (graphical jackknife location of weak sources by few, low-SNR records)   总被引：1，自引：0，他引：1  

Gilles Hillel Wust-Bloch  Manfred Joswig 《Geophysical Journal International》2006,167(3):1220-1232

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采矿引起的边坡倾倒滑移变形机理与变形安全性分析研究—以抚顺西露天矿边坡为例   总被引：1，自引：0，他引：1  

申力  纪玉石  刘大勇  祖国林  刘晶辉 《中国地质灾害与防治学报》2006,17(3):63-68

在矿山开发、水电建设过程中倾倒变形问题日渐突出。倾倒变形边坡一般具有反倾边坡结构,变形的过程和机理比较复杂、涉及的变形岩体范围较大、危害严重。论文以抚顺西露天矿边坡为例,通过岩体位移监测资料的跟踪分析、底面摩擦模拟试验,以岩体力学、松散介质力学原理为理论基础,探讨了采矿影响下边坡倾倒滑移体的变形机理,分析认为采矿引起的倾倒滑移变形问题是在特定的地质构造和采矿工程条件下产生的,并提出了岩体变形安全性分析方法。通过工程实例,验证了方法的实用性,并针对实际问题提出了变形整治对策。  相似文献   

初至折射波静校正技术在复杂探区地震数据处理中的应用   总被引：1，自引：0，他引：1  

车建英  张伟 《中国煤田地质》2006,18(1):54-56

山区及黄土塬地区近地表结构复杂，地形起伏大、低降速带横向变化剧烈，地震资料处理中的静校正难度加大。长波长静校正容易引起构造形态畸变，短波长静校正影响地震剖面信噪比。针对此类问题，从长波长静校正问题及短波长地表非一致性问题分析入手，提出部分炮检距叠加识别长波长静校正技术及分段统计逼近地表非一致性校正技术。该技术在复杂地表区与其它相关技术综合应用，可有效解决长、短波长静校正问题。  相似文献