滇西北三江并流区土地利用变化研究     

王金亮  蒋莲芳  李瑞林 《云南地理环境研究》2005,17(1):5-12,23

土地利用变化会改变地表覆盖,从而影响环境质量及陆地生态系统性质。开展区域土地利用/土地覆盖变化研究,可为区域土地资源优化利用和可持续发展提供科学依据。以第二次土壤普查资料和土地详查资料为依据,采用土地利用变化指数模型,定量分析三江并流区1983年到1999年土地利用变化特征,结果表明:(1)与土地利用结构分析法相比,土地利用变化指数模型更能反映土地变化趋势及在时空上变化特点;(2)研究区土地利用程度不断提高,其中林地园地、耕地与城郊用地增加较快;(3)1983～1996年间的变化大于1996～1999年间的变化;(4)州政府所在地(香格里拉县、泸水县、丽江县)的变化较其它地区大;(5)土地利用变化的主要原因是社会经济因素,包括人口增长、科技进步、经济增长、传统文化继承与发展、政策变化等。  相似文献   

Resident Attitudes to Farmland Protection Measures in the Northern Rivers Region,New South Wales     

Chris Gibson  Rae Dufty  Danielle Drozdzewski 《The Australian geographer》2005,36(3):369-383

In-migration to popular ‘sea change’ and ‘tree change’ regions has produced conflicts between rural land users. In the Northern Rivers region of New South Wales, new residential developments have been built on much of what was previously prime agricultural land, while farmers (in particular, those negatively affected by the deregulation of the dairy industry) have sought to secure retirement incomes by subdividing land for sale. Although developers, local councils and individual farmers sometimes see eye to eye on the mutual benefits of in-migration and population growth, land use has none the less become the subject of a hotly contested local political battle. Conflicts occur at the interface of growing urban developments and surrounding farmland, with new residents finding the sights, sounds and smells of rural production intrusive. More generally, there is considerable concern that the best farmland in the region may be lost to urbanisation and rural residential subdivision. This paper discusses the results of a survey that collected opinions from local residents about the pressures on the region's land uses by in-migration, the future role of farmland as both an economic and cultural landscape, and views on proposed measures to protect prime farmland in the region. Results highlighted a strong and consistent ‘pro-farmland’ and ‘pro-protection’ attitude throughout the region, and across social groups. Yet, variations emerged when respondents were asked about why they attribute value to agricultural landscapes. For some, ‘economic’ values dominated, while for others, value was attributed in ways that reflected an emerging ethos of ‘localism’ and village lifestyle. Although values differed, a clear message from this study is that the population of Australia's pre-eminent ‘sea change’ region strongly support measures to curb urban development and the more destructive consequences of a dynamic property market.  相似文献   

西藏"一江两河"地区生态环境地质问题与防治对策     

王作堂 《四川地质学报》2005,25(1):16-18,26

从生态环境地质的角度出发，指出西藏“一江两河”地区由于生态环境条件脆弱、生态系统的不稳定，在缺乏生态屏障保护下，对资源的大量开发利用、天然植被的大量掠取，诱发和加重了一系列重大生态环境地质问题；有针对性地提出了生态地质环境保护措施和防治对策，并提供了典型实例和经验。  相似文献   

Fractal sinuosity of stream channels   总被引：4，自引：0，他引：4  

R. Scott Snow 《Pure and Applied Geophysics》1989,131(1-2):99-109

Analysis of a diverse set of twelve stream channel planforms indicates that at scales relevant to river meandering, river traces are most reasonably treated as fractal curves. The atypically high degree of channel wandering apparent at such scales is a common characteristic of all single-channel streams, while identifiable meandering appears to be only one way in which this tendency is expressed. At smaller scales of view river paths have shapes of smooth curves appropriate to Euclidian geometry, and toward larger scales a distinct change in degree of wandering marks the transition to bends that are considered to be changes in general river course rather than parts of channel pattern. This analysis method provides a natural, objective calculation of river sinuosity as well as other parameters that more completely specify channel planform.  相似文献   

Downstream hydrologic and geomorphic effects of large dams on American rivers   总被引：12，自引：4，他引：12  

William L. Graf   《Geomorphology》2006,79(3-4):336

The hydrology and geomorphology of large rivers in America reflect the pervasive influence of an extensive water control infrastructure including more than 75,000 dams. One hundred thirty-seven of the very large dams, each storing 1.2 km³ (10⁶ acre feet) of water or more, alter the flows of every large river in the country. The hydrologic effects of these very large dams emerge from an analysis of the stream gage records of 72 river reaches organized into 36 pairs. One member of each pair is an unregulated reach above a dam, whereas the other is a regulated reach downstream from the same structure. Comparison of the regulated and unregulated reaches shows that very large dams, on average, reduce annual peak discharges 67% (in some individual cases up to 90%), decrease the ratio of annual maximum/mean flow 60%, decrease the range of daily discharges 64%, increase the number of reversals in discharge by 34%, and reduce the daily rates of ramping as much as 60%. Dams alter the timing of high and low flows and change the timing of the yearly maximum and minimum flows, in some cases by as much as half a year. Regional variation in rivers, dams, and responses are substantial: rivers in the Great Plains and Ozark/Ouachita regions have annual maximum/mean flow ratios that are 7 times greater than ratios for rivers in the Pacific Northwest. At the same time, the ratio of storage capacity/mean annual water yield for dams is greatest for Interior Western, Ozark/Ouachita and Great Plains rivers and least for Pacific Northwest streams. Thus, in many cases those rivers with the highest annual variability have the greatest potential impact from dams because structures can exert substantial control over downstream hydrology. The hydrologic changes by dams have fostered dramatic geomorphic differences between regulated and unregulated reaches. When compared to similar unregulated reaches, regulated reaches have 32% larger low flow channels, 50% smaller high flow channels, 79% less active flood plain area, and 3.6 times more inactive flood plain area. Dams also affect the area of active areas, the functional surfaces that are functionally connected to the present regime of the river. Regulated reaches have active areas that are 72 smaller than the active areas of similar unregulated reaches. The geomorphic complexity (number of separate functional surfaces per unit of channel length) is 37% less in regulated reaches. Reductions in the size of hydrologically active functional surfaces are greatest in rivers in the Great Plains and least in Eastern streams. The largest differences in geomorphic complexity are in interior western rivers. The shrunken, simplified geomorphology of regulated large rivers has had direct effects on riparian ecology, producing spatially smaller, less diverse riparian ecosystems compared to the larger, more complex ecosystems along unregulated reaches of rivers.  相似文献   

Metal ion binding to colloids from database to field systems     

M.F. Benedetti   《Journal of Geochemical Exploration》2006,88(1-3):81

Nowadays, environmental problems related to soil pollution with heavy metals are numerous, therefore, it is important to understand metals behaviour in aquatic sediments and soils and to estimate their transfer. The fate of metals in the environment is closely related to their interactions with the major reactive compartments (organic matter, iron and manganese oxides, clays). The objective of this work is to develop an approach based on the combination of several models to study metal ion speciation in different environmental systems. Models used to describe the interactions of metals with the main reactive phases in the soil are CD-MUSIC (amorphous and crystallized iron oxides), NICA-Donnan (organic matter and manganese oxides) and cationic ion exchange model (clays). First, this work implies the definition of generic parameters to describe the interactions of the studied metals with iron and manganese oxides and part of this information is missing in the literature. Then, after a validation of the approach by comparison with analytical results, this multi-surface model is applied to test sites corresponding to one soil and two riverine environments.These new models give good predictions of the behaviour of major and trace metal ions even in heterogeneous systems characteristic of natural environment. The measured free metal concentrations in the solution are in agreement with those obtained from model calculations. In the case of the soil test site, the soil solution composition and speciation are predicted using the soil major constituents characteristics.  相似文献   

三江并流世界遗产区土地覆盖与可持续发展     

李勇张军彦  程根伟 《山地学报》2006,24(B10):355-359

三江（金沙江、澜沧江、怒江）并流区于2003—07加入世界遗产，被世界遗产组织提名为地资源价值的“唯一性和完整性”区。但是长期的过量森林砍伐，落后的农业生产方式，导致本地区的生态功能退化严重，恢复重建异常困难。因此如何改变过去的生产方式，充分发挥土地生产潜力，提高人民生活，促进社会经济持续发展，成为国内国际关注的重点。运用土地生态学和土地生态学原理，就三江并流世界遗产区土地利用与可持续发展关系进行探讨，提出了以保护为前提，调整产业结构，适度开展生态旅游，实现景观资源的可持续利用，取得最大的社会、生态、经济效益的观点。  相似文献   

Diatoms from the genus Achnanthidium in flowing waters of the Appalachian Mountains (North America): Ecology, distribution and taxonomic notes     

Karin C. Ponader  Marina G. Potapova 《Limnologica》2007,37(3):227-241

Diatoms from the genus Achnanthidium are abundant in rivers, streams, and springs of the Appalachian Mountains. They inhabit clean and polluted waters, including those affected by acid mine drainage. The identification of Achnanthidium taxa is difficult due to their small cell size and insufficient information in the diatom floras. We studied the taxonomy and ecology of Achnanthidium in Appalachian rivers by analyzing a data set of benthic diatom samples and corresponding water chemistry data collected during several water-quality surveys from 181 sampling sites. Ten species were identified using scanning electron and light microscopy: A. alpestre (Lowe & Kociolek) Lowe & Kociolek, A. atomus (Hustedt) Monnier, Lange-Bertalot, & Ector, A. deflexum (Reimer) Kingston, A. duthii (Sreenivasa) Edlund, A. eutrophilum (Lange-Bertalot) Lange-Bertalot, A. cf. gracillimum (Meister) Lange-Bertalot, A. cf. latecephalum Kobayasi, A. minutissimum (Kützing) Czarnecki (sensu lato), A. reimeri (Camburn) comb. nov., and A. rivulare Potapova & Ponader. The distribution of common taxa in relation to water chemistry was studied by fitting non-parametric regression models (generalized additive models, GAM, and non-parametric multiplicative regression models, NPMR) to species relative abundances. Studied Achnanthidium species differed considerably in their responses to water chemistry. These results suggest that species-level identifications will lead to more accurate bioassessments.  相似文献   

逆插支流的演变与河流掉向的关系   总被引：1，自引：0，他引：1  

廖喜林 《地质灾害与环境保护》1999,10(2):14-17

逆插支流是相对正插和顺插支流而言,它们之间的演变过程,受到新构造运动、流水地质作用等诸因素的影响。尤其是逆插支流的演变,对主干河流是否掉向,意义重大,但不是所有逆插支流都对指示主干河流掉向有意义。试图从演变的角度,来剖析逆插、正插和顺插支流的内在联系,以求探讨上述问题。  相似文献   

The georgia rivers land margin ecosystem research program     

R.G. Wiegert  M. Alber  C. Alexander  J.O. Blanton  A. Chalmers  R.E. Hodson  M.A. Moran  L.R. Pomeroy  W.J. Wiebe 《Limnologica》1999,29(3):286

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