Spatial arrangement and physical characteristics of structural woody habitat in a lowland river in south‐eastern Australia

• 1. The importance of structural woody habitat (SWH) as instream fish habitat in eastern Australia has been well documented. In response, many native fish restoration programmes are returning SWH to rivers where it had previously been removed. However, there is little information to direct the placement of this SWH within a river landscape.
• 2. Low‐level, high‐resolution aerial photographs were used to investigate the spatial pattern of SWH in the Murray River between Lake Mulwala and Tocumwal. It was found that SWH occurred in aggregations that were closely associated with eroding banks on meanders.
• 3. The physical characteristics of the SWH in these aggregations varied (basal diameter range 0.44–2.45 m, length range 1–44 m); however, small‐ to medium‐sized trees (basal diameter range 0.7–1.4 m, length range 5–20 m) were most common.
• 4. The association between eroding banks and SWH suggests that bank erosion may be an important determinant in the formation of SWH aggregations.

Copyright © 2004 John Wiley & Sons, Ltd.     

沙质海岸前沿不同下垫面的沙粒度参数特征

在海岸前沿选取林地、草地、裸地3种不同的下垫面环境，研究风沙运动对其粒度的影响。结果表明，3个样地均以细沙为主，中沙、粗沙分列其后，但样地间沙粒含量差异很大；3个样地粒径均随海岸距离的增加而变粗，林地变化较为明显且粒径最粗，林地和草地下层的沙粒径都比表层的粗，裸地则无明显变化；与草地和裸地相比，林地内沙土平均粒径最粗，标准偏差最大，负偏程度最高，这与林地内粒径较粗有关；在草地和裸地中，平均粒径与各粒度参数均存在良好的相关性，表明草地和裸地沉积物为风力搬运堆积的产物，受风选作用明显。细沙与极粗沙和粗沙都呈现极显著的正相关关系，可以根据极粗沙和粗沙的含量来判别防护林的防护效应，即在海岸前沿，沙粒粒径越粗，防护效能越好。     

广东省地质灾害的空间分布及成因分析

对近年来广东省大量地质灾害进行了统计分析,从地形地貌、岩土类型、地质构造、地震、降雨以及人类工程活动与地质灾害的关系入手,系统地研究了广东省地质灾害的空分布规律,为广东省防灾减灾战略和经济建设规划提供了地质依据。     

Are River Styles ecologically meaningful? A test of the ecological significance of a geomorphic river characterization scheme

• 1. Classification is a useful tool for researchers and managers wishing to group functionally similar sites or to identify unique or threatened habitats. A process‐based river classification scheme that successfully integrates physical and biological aspects of lotic form and function would enhance conservation and restoration efforts by allowing more meaningful comparisons among sites, and improving functional understanding of lotic ecosystems.
• 2. The River Styles framework provides a geomorphological river characterization scheme in which assemblages of geomorphic units vary for differing River Styles, presenting differing arrays of aquatic habitat diversity for each style.
• 3. The ecological significance of the River Styles framework is tested by comparing the macroinvertebrate assemblages and habitat characteristics of pool and run geomorphic units for three different River Styles on the north coast of New South Wales, Australia.
• 4. Multivariate ordinations and analysis of similarity (ANOSIM) revealed that macroinvertebrate community structure differed between Bedrock‐Controlled Discontinuous Floodplain rivers and Gorge rivers, and between Bedrock‐Controlled Discontinuous Floodplain and Meandering Gravel Bed rivers, especially in pools. Differences between Gorge and Meandering Gravel Bed rivers were less apparent, largely due to variations within the Meandering Gravel Bed rivers group.
• 5. The variability in macroinvertebrate assemblage structure among geomorphic units was most strongly related to variability in substrate and hydraulic variables. Substrate composition differed significantly among all River Styles and geomorphic units, but other habitat variables showed few consistent differences among River Style groups.
• 6. These results suggest that the ecological similarity of macroinvertebrate communities within River Styles may presently be limited because some important large‐scale drivers of local habitat conditions are not included in River Styles designations. Integrating River Styles classification with other large‐scale variables reflecting stream size, temperature and hydrological regime may produce a process‐based physical classification capable of identifying river reaches with similar ecological structure and function.

Copyright © 2003 John Wiley & Sons, Ltd.     

河西沙区新月形沙丘形态参数观测

新月形沙丘广泛分布于世界各沙漠,是最基本的沙丘形态之一。国内外众多学者对沙丘形态参数间的关系研究表明沙丘高度和宽度间存在线性关系。通过对河西沙区巴丹吉林沙漠和腾格里沙漠边缘典型新月形沙丘形态的高精度测量,并结合前人对民勤地区新月形沙丘的观测数据,用最小二乘法拟合发现高度和宽度呈正比例关系。并与库姆塔格沙漠5个新月形沙丘的比例系数比较,发现不同自然环境条件下发育的新月形沙丘的比例系数不一致,该系数可以作为描述新月形沙丘的一个特征参数。     

崀山丹霞地貌区植物群系特性研究

采用线路与标淮地调查相结合的方法,研究了崀山丹霞地貌区森林植物群系特性。结果为:峎山有10个植被型、72个植物群系,其植被主要是中国、日本共同的属和众多的中国特有属树种为组成特征的森林植被,也有一定比例东亚—北美成分,在结构组成上表现出中亚热带常绿阔叶林的特点;丹霞单体出現特异的群系分布格局和"植被孤岛效应",不同发育期丹霞地貌上分布着不同演替系列上的森林植被类型;发現分布于丹霞赤壁下部的1个新的植被型(藤本植被型)和2个丹霞赤壁面上由崀山特有物种为建群种组成的持有植物群系(新宁毛莨群系,崀山唇柱苣苔群系)。     

加强专业基础课教学 提高地质地貌学教学效果

地质地貌学是资源与环境等专业的一门专业基础课,在课程体系中处于重要的地位,后续的土壤学等很多课程都离不开地质地貌学基本理论。为了让学生更好的掌握课程的知识内容,针对课程教学中存在轻视专业基础课等一些问题,从教学内容、教学方法、考试方法等方面进行改革,提出了解决教学问题的新方法和思路,运用首因效应形成良好的第一印象,运用印象管理策略延续良好的第一印象,提高教学质量和教学效果。     

Soil-geomorphic significance of land surface characteristics in an arid mountain range,Mojave Desert,USA

Mountains comprise an extensive and visually prominent portion of the landscape in the Mojave Desert, California. Landform surface properties influence the role these mountains have in geomorphic processes such as dust flux and surface hydrology across the region. The primary goal of this study was to describe and quantify land surface properties of arid-mountain landforms as a step toward unraveling the role these properties have in soil-geomorphic processes. As part of a larger soil-geomorphic study, four major landform types were identified within the southern Fry Mountains in the southwestern Mojave Desert on the basis of topography and landscape position: mountaintop, mountainflank, mountainflat (intra-range low-relief surface), and mountainbase. A suite of rock, vegetation, and morphometric land surface characteristic variables was measured at each of 65 locations across the study area, which included an associated piedmont and playa. Our findings show that despite the variation within types, landforms have distinct land surface properties that likely control soil-geomorphic processes. We hypothesize that surface expression influences a feedback process at this site where water transports sediment to low lying areas on the landscape and wind carries dust and soluble salts to the mountains where they are washed between rocks, incorporated into the soil, and retained as relatively long-term storage. Recent land-based video and satellite photographs of the dust cloud emanating from the Sierra Cucapá Mountains in response to the 7.2-magnitude earthquake near Mexicali, Mexico, support the hypothesis that these landforms are massive repositories of dust.     

Fluvial development and the sediment regime of the lower Calder,Ribble catchment,northwest England

In the lower reaches of the Calder (Lancashire) tributary of the Ribble catchment (northwest England), five river terraces set into the surrounding glacial terrain have been mapped and their underlying sediments radiocarbon dated. The earliest terrace (T1) reflects sandur-style deposition during deglaciation and it aggraded in a reach cut into glacial diamict and glaciolacustrine muds. Incision below T1 spanned the start of the Holocene, driven by a combination of reduced sediment supply under a stabilising landscape and lower base-levels. T2 had aggraded and was being abandoned by 4000 BC; its formation latterly involving a period of comparative stability in terms of channel migration, perhaps a function of extensive forest cover and sea levels reaching above present day levels. The last 3000 years were marked by substantial changes in the sedimentary regime, with increased and varying sediment supply driving cycles of cut-and-fill and greater lateral channel migration. These changes coincided with the first widespread and substantial reductions in forest cover and a progression towards an agricultural landscape. Between the aggradation of terraces T3 and T4 there was a substantial increase in sediment supply, which is broadly in keeping with the erosion history in the surrounding uplands. This sediment slug appears to have induced a switch from highly sinuous meandering to lower sinuosity channels characterised by lateral scroll-style migration. Late Holocene vegetation changes, particularly woodland removal, driven by anthropogenic land-pressure appear to have rendered the floodplain prone to channel migration and the landscape more susceptible to erosion.     

黄土高原小流域重力侵蚀数值模拟

为研究黄土高原小流域重力侵蚀机理,采用fish语言编写多层复杂地形建模的前处理程序,对多层复杂地形建模进行了二次开发。从力学稳定性角度,采用有限差分FLAC3D软件对黄土高原小流域概化模型进行重力侵蚀机理研究,分析了流域重力侵蚀的发育过程,并对小流域位移场和应力场进行了数值模拟。结果表明：建立的三维模型能真实地表现小流域地形、地貌,仿真效果良好。小流域重力侵蚀过程分为发育期、成熟期和稳定期3个阶段,沟头溯源区是小流域侵蚀最强烈的部位;凹形的边坡整体几何形态利于边坡稳定,减缓了重力侵蚀的发生程度。建模方法和数值模拟结果可应用到重力侵蚀研究中,为推动流域侵蚀产沙时空规律研究的深入发展和小流域水土流失综合治理以及生态环境建设提供科学依据。