福建省崩岗发生的地质和地貌条件分析

以福建省崩岗最发育的地区安溪县官桥镇—龙门镇、长汀县河田镇、永春县达埔镇—蓬壶镇和诏安县官陂镇为对象,从岩性、构造、地质发展史3个方面阐明崩岗侵蚀的地质和地貌背景。结果表明,大规模崩岗发育区的地质、地貌背景是燕山晚期大面积侵入性质均匀的岩石(花岗岩体),位于从古生代至今长期活动的区域性主干断裂带上,发育的地貌处于壮年期的晚期向老年期的发展阶段。海拔高度与崩岗地区的相对侵蚀基准面高度两个指标共同影响着崩岗的发育,相对高差在20～100m以内崩岗最发育。     

Background concentrations and loadings of nitrogen in Danish surface waters

Quantitative knowledge of background nitrogen (N) concentrations and loadings is essential for as it determines the minimally disturbed conditions for N in surface waters as a near reference condition. To determine background N concentrations, a total of 39 smaller Danish streams draining relatively undisturbed catchments in different regions were selected and screened for N concentrations and discharge during a 1-year period (2004–2005). Only 19 of the streams fulfilled the threshold set for least disturbed conditions (LDC) in their catchments (proportion of agricultural land <10%). Within the five sampled dominant landscape types in Denmark, the concentrations of ammonium N and total organic N in the LDC streams were found to be nearly constant: 0.05 ± 0.01 mg N L^?1 and 0.53 ± 0.07 mg N L^?1, respectively. In contrast, the concentration of nitrate N differed significantly (P < 0.05) between the five landscape types, with variations between 0.06 and 0.83 mg N L^?1. An analysis of all the 39 streams sampled demonstrated significantly different relationships between the proportion of land use and the flow-weighted annual concentration of nitrate N for two dominant soil types with a Y-axis intercept equal to 0.12 mg N L^?1 for streams draining coarse textural soils and 0.76 mg N L^?1 for streams draining finer textural soils. A significant (P < 0.05) downward trend (18–41%) emerged for flow-weighted annual total N concentrations in four of the five streams that were sampled during the period 1990–2011. A 5 × 5 km grid map of Denmark showing nitrate N and total N background concentrations was produced and used for estimating background N losses to Danish surface waters. Based on the grid map, the average annual background loss of total N was calculated to be 13,000 tonnes N or 19% of the total N loading to Danish coastal waters during the period 2004–2005.     

均衡纵剖面形态的实验研究

均质地层和定流量条件下均衡纵剖面的形成过程与最速滑降问题类似.从最小耗能原理出发,用大量的室内实验成果验证了理想的均衡纵剖面应最接近于一条摆线,从而证实了理论推求的结论,并为均衡纵剖面理论的实践应用打下了坚实的基础.     

Linking form and function: towards an eco‐hydromorphic approach to sustainable river restoration

• 1. River restoration is now widely undertaken and may be considered an increasingly important aspect of river management. Recent developments in European legislation (Habitats Directive and the Water Framework Directive) should give further impetus to river restoration across EU member states, as this legislation places greater emphasis on the processes that support river ecology.
• 2. Traditional river restoration approaches have been reach‐focused and opportunistic, capitalizing on flood defence works and the cooperation of sympathetic landowners.
• 3. Furthermore, many schemes have been species‐ or habitat‐driven and, thus, have sought to recreate channel forms believed to be favoured by particular species or associated with particular habitats. Such approaches have not always given due attention to the underlying geomorphological processes that create channel form and, consequently, the schemes have not been self‐sustaining, requiring continued management input.
• 4. Consistent with the ethos of the Water Framework Directive, an eco‐hydromorphic approach to river restoration is proposed here. This approach views spatial and temporal heterogeneity as fundamental characteristics of fluvial systems and advocates recreating a framework within which natural processes, such as sediment transport and nutrient dynamics, can occur.
• 5. Mesoscale habitat approaches are considered as one possible way to plan and achieve this framework, providing the potential to link the wide range of spatial and temporal scales that characterize river systems.
• 6. It is argued that river restoration will only be sustainable if it is undertaken within a process‐driven and strategic framework with inputs from a wide range of specialists. Such an approach needs to be reviewed constantly in light of appraisal and monitoring of previous river restoration schemes.

Copyright © 2003 John Wiley & Sons, Ltd.     

大理河流域地貌多重分形特征空间分异研究

利用流域数字高程DEM,采用流域地貌多重分形模型及其实现方法,对大理河流域中的11条子流域地貌多重分形参数进行了计算,分析了其空间分异特点。结果表明:大理河流域地貌多重分形参数奇异指数的最小值αmin、地貌表面积分布最小概率子集的分形维数f(αmin)和最大概率子集的分形维数f(αmax)的平均值从上游至下游呈明显递减趋势,奇异指数最大值αmax和奇异指数变化范围Δα平均值从上游到下游呈递增趋势,说明最大坡度地貌单元出现在上游,最小坡度地貌单元出现在下游,大理河流域地貌形态变化自上游向下游趋于复杂。大理河流域左岸αmin和f(αmin)均值大于右岸,表明最大坡度地貌单元所占比例左岸较大;左岸Δf平均值大于右岸,表明右岸中最小坡度的地貌单元所占比例大于最大坡度地貌单元所占比例;Δα均值右岸大于左岸,表明大理河右岸地貌复杂程度相对较大;总体来说,大理河流域地貌右岸的差异性、不均匀性和复杂度均大于左岸。该研究对于探讨黄土地貌多重分形参数的地貌学意义具有重要参考价值。     

Habitat use by a freshwater dolphin in the low‐water season

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