The palaeolimnology of Lake Fidler, a meromictic lake in south-west Tasmania and the significance of recent human impact     

Dominic Hodgson  Peter Tyler  Wim Vyverman 《Journal of Paleolimnology》1997,18(4):313-333

Three meromictic lakes in the World Heritage Area of south-west Tasmania possess unusual microbiological communities. Their meromixis is maintained by periodic incursions of brackish water from the nearby Gordon River which, in its lower reaches, is a salt-wedge estuary. In 1977 the construction of a dam in the middle reaches of the river restricted penetration of the salt-wedge and meromixis rapidly declined in all three lakes. A palaeolimnological study was carried out on one of the lakes, Lake Fidler, firstly to determine the history of meromixis and its associated microbiological communities, and secondly to assess whether the recent and rapid decline of meromixis is inconsistent with natural rates of development of the Gordon River meromictic lakes. One part of this study included the analysis of the stratigraphy of fossil diatoms from a 17-metre sediment core dating back 8000 yrs. Detrended Correspondence Analysis and Analog Matching were used to compare diatom species assemblages in core samples with diatom samples from a reference dataset consisting of a selection of lake and river sites in the lower Gordon River valley. Five distinct stratigraphic zones were identified in the core. These zones indicated specific stages in the development of the Gordon River lakes from river backwaters to ectogenically-maintained meromictic lakes which will, finally, become terrestrialised by encroaching rainforest. The onset of a stratified water column was identified by the emergence of a dominant freshwater algal flora which suggested that the lake had developed a mixolimnion and become meromictic ca. 2070 ± 50 ¹⁴C yrs ago. In the context of this long history of meromixis, the rapid demise in meromictic stability following construction of the dam is judged to be inconsistent with natural rates of development. The palaeolimnological studies, of which this paper is one part, prompt recommendations for a management strategy to prevent the further decay of these meromictic lakes in the World Heritage Area.  相似文献   

黄河流域水循环演变若干问题的研究   总被引：29，自引：0，他引：29       下载免费PDF全文

刘昌明 《水科学进展》2004,15(5):608-614

从若干方面的研究结果揭示了黄河流域水循环发生的巨大变化.水循环是水资源科学评价与合理开发利用的基本依据.水循环主要要素的变化取决于气候条件的变化与人类活动的影响.对前者宜采用适应性对策,在研究气候变化的基础上,分析水循环变动的规律并预测其趋势,制定相应的适应性措施;对于后者则应加强水资源开发利用的科学管理,以维持流域天然水资源的可更新(可再生)性.  相似文献   

科尔沁沙地土地沙漠化的历史与现状   总被引：9，自引：6，他引：9  

任鸿昌  吕永龙  杨萍  陈惠中  史雅静 《中国沙漠》2004,24(5):544-547

科尔沁沙地是我国自然条件相对较好的一个沙地，有着广阔的治理前景。回顾科尔沁沙地的历史变化，认为科尔沁沙地是一个全球气候变化大趋势下由人类生产活动过度而形成的沙漠化区域，在金代至清代之间由于人为活动强度减弱，曾经发生明显的沙漠化逆转。根据全国沙漠化普查所获得的资料，研究分析了科尔沁沙地土地沙漠化现状及其特点，结合土地沙漠化发生的历史过程，讨论了这一地区沙漠化的治理策略。  相似文献   

Assessing natural and cultural influence on soil in remnant tropical woodlands     

C Y Jim  Michael W H Chan 《Area》2004,36(1):6-18

Rural Hong Kong contains culturally protected enclaves of remnant woodlands that provide sanctuary for vegetation, wildlife and soil. This study focuses on the influence of natural and cultural factors on soil properties in woodlands with different human activities. At each of the nine selected sites, two pits were dug to collect soil samples for analysis of 24 physical and chemical properties. Analyses of variance between soil attributes and site factors suggest the prominence of woodland size, and important contribution of topography, aspect and parent material. Soil indicators of human impacts and the tenacity of woodland soil towards anthropogenic disturbance were demonstrated.  相似文献   

发展中国家食物安全研究的新进展     

肖平 《世界地理研究》2004,13(2):9-14

本文回顾了七十年代以来食物安全概念的演变历史，特别是介绍了森(Sen)的食物权利理论在这个历史过程中的作用，评价了当前的主要研究热点，展望了将来的几个研究趋势。指出食物安全的概念不能也不应该以单一的观点、方法和尺度来定义，食物安全的研究必须要更紧密地与更广泛的人文安全和环境变化的内容联系在一起，才能更深入地进行下去。  相似文献   

Controlling factors of gullying in the Maracujá Catchment,southeastern Brazil     

L. de A. P. Bacellar  A. L. Coelho Netto  W. A. Lacerda 《地球表面变化过程与地形》2005,30(11):1369-1385

Hundreds of gullies (‘voçorocas’) of huge dimensions (up to 400–500 m long, 150 m wide and 50 m deep) are very common in the small Maracujá Catchment in southeastern Brazil. These erosional features, which occur with an uneven intensity throughout the area, started due to bad soil management practices at the beginning of European settlement, at the end of the 17th century, and nowadays are still evolving, but at a slower rate. As surface soils are usually very resistant to erosion, the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning. An analysis of well known erosion controlling factors was performed, aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution. Data shows that geology and, mainly, geomorphology are the main controlling factors, since gullies tend to be concentrated in basement rock areas with lower relief (domain 2) of Maracujá Catchment, mainly at the fringes of broad and flat interfluves. At the detailed scale (1:10 000), gullies are more common in amphitheatre‐like headwater hollows that frequently represent upper Quaternary gullies (paleogullies), which demonstrate the recurrence of channel erosion. So, gullies occur in areas of thicker saprolites (domain 2), in places with a natural concentration of surface and underground water (hollows). Saprolites of the preserved, non‐eroded hollows are usually pressurized (confined aquifer) due to a thick seal of Quaternary clay layer, in a similar configuration to the ones found in hollows of mass movement (mudflow) sites in southeastern Brazil. Therefore, the erosion of the resistant soils by human activities, such as road cuts and trenches (‘valos’), or their mobilization by mudflow movements, seem to be likely mechanisms of gullying initiation. Afterwards, gullies evolve by a combination of surface and underground processes, such as wash and tunnel erosion and falls and slumps of gully walls. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Changes in the spatial scale of Beijing UHI and urban development   总被引：2，自引：1，他引：2  

YU Shuqiu  BIAN Lingen  LIN Xuechun 《中国科学D辑(英文版)》2005,48(Z2)

The seasonal and interannual variations of Beijing urban heat island (UHI) are investigated in this paper using the temperature data from 1960 to 2000 at 20 meteorological stations in the Beijing region, and then the relationship between the intensity and spatial scale of UHI and Beijing urbanization indices is analyzed and discussed. Main conclusions are the followings. First, Beijing UHI shows obvious seasonal variations, and it is strongest in winter, next in spring and autumn, and least in summer. The seasonal variation of the UHI mainly occurs in the urban area. The UHI intensity at the center of Beijing is more than 0.8℃ in winter, and only 0.5℃ in summer. Second, the intensity of Beijing HUI exhibits a clear interannual warming trend with its mean growth rate (MGR) being 0.3088℃/10 a. The MGR of HUI is largest in winter, next in spring and autumn, and least in summer, and the urban temperature increase makes a major contribution to the growth of HUI intensity. Third, since the Reform and Opening, the urbanization indices have grown several ten times or even one hundred times, the intensity of HUI has increased dramatically, and its spatial scale also expanded distinctively along with the expansion of urban architectural complexes. Fourth, the interannual variation of urbanization indices is very similar with that of HUI intensity, and their linear correlation coefficients are significant at a more than 0.001 confidence level.  相似文献   

生态城市的内涵及建设策略   总被引：7，自引：4，他引：7  

程伟 《云南地理环境研究》2005,17(4):43-45

生态城市是通过倡导生态理念，采用生态技术，建立生态化产业体系，从而达到社会、经济、环境的可持续发展，实现自然生态平衡、人文生态和谐的城乡统一体。从可持续发展的角度出发，利用生态学和社会学的观点，论述生态城市的内涵，提出科学的城市规划、合理的城市评价指标体系、完善的城市管理制度是实现生态城市的前提，强调只有自然生态、人文生态两手抓才能真正实现经济、社会、环境全面发展。  相似文献   

人口生态生产:人地作用机制下"三江并流"世界遗产保护的新视角     

熊理然  骆华松 《云南地理环境研究》2005,17(6):69-73

基于不同人口需要而进行的人类活动对“三江并流”区的地理环境产生了巨大影响,形成了独具特色的人地作用机制。这一作用机制一方面对“三江并流”世界遗产的保护构成了威胁,但另一方面,通过人口生态生产,实现人口数量、质量、结构和分布的生态化,改进人类活动,也可优化“三江并流”区的地理环境,保护“三江并流”世界遗产,实现该地区的可持续发展。  相似文献   

黄土区人类活动影响下的 产汇流模拟研究   总被引：4，自引：0，他引：4  

池宸星  郝振纯  王玲  胡健伟 《地理科学进展》2005,24(3):101-108

日益频繁的人类活动改变了流域下垫面条件,对流域产汇流产生很大的影响。本文以黄河中游典型支流岔巴沟为研究区域,提出利用基于DEM的分布式水文模拟技术,探讨流域人类活动过程中的产汇流模拟,避免了经验公式的概化和由此引起的局限。模拟的结果证实了该方法的可行性。采用网格滞蓄的方法可以在子网格上体现人类活动引起的下垫面的变化及其对产汇流的影响,反映各个时期的产汇流条件,对降雨做出合理响应。  相似文献