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1.
An analysis is made of the karst geomorphosystems of the Yucatán Peninsula. It is found that the main factors influencing its formation were climate and ocean level oscillations, tectonic movements, and impact effects. It is established that as a result of an active influence of the Maya civilization on the karst landscape of the peninsula, the geomorphosystems was transformed to the karst-anthropogenic system. The karstic landforms, and also the underground caverns experienced the anthropogenic impact, and the subsurface waters were particularly heavily influenced, which, on the one hand, determined the places of concentration of settlements and were actively consumed by the population, and, on the other, their reserves were replenished at regular intervals as a result of the creation of artificial subsurface water storages. In a further transformation of the karst-anthropogenic system, two stages were additionally identified: dominated by natural karstic processes (after the decline of the Maya civilization), and with a renewed intensification of anthropogenic pressure (1980s–current period). The last transformation stage is distinguished by an extension of the impact to the surface karst as well as to the underground caverns: they are subjected to mechanical destruction with an enhancement in the chemical impact as a result of inputs of polluted runoffs to encompass ever deeper horizons of subsurface waters. It is established that the rates of transformation processes of anthropogenic objects created of limestone are, in general, comparable with the mean rates of natural karstic processes on the neighboring territories: the formation of karrens on Maya steles is generally proceeding at the rate of 0.04 mm/year, while the growth rates of flowstones within urban structures of limestone vary from 0.03 to 0.6 mm/year. 相似文献
2.
《Urban geography》2013,34(2):211-235
This study examines the changing demography of the Spanish city of León, and aims to explore the manner in which its urban fabric was reshaped by processes of reurbanization, a dynamic whereby the inner city becomes more attractive to a wide variety of household types and social groups. We draw on sociodemographic analyses of municipal census data, as well as a customized questionnaire survey of local residents. Empirical evidence is provided both for the city as a whole and two inner-city districts, Casco Antiguo and El Ejido. Among other findings, it is argued that, although the contiguous built-up area of the city is clearly losing its inhabitants through out-migration and aging, there are a series of small-scale migration flows that increasingly concentrate "nontraditional" households in and around the city center. This is accompanied by an increasing trend toward "city-mindedness" as a residential choice and housing preference among both in-migrants and the long-time residential population. Overall, the evidence points to the emergence of a spatially fragile, fragmented reurbanization process. 相似文献
3.
Seed germination was compared among wild, in situ-managed (wild plants let standing in areas cleared for agriculture), and cultivated populations of the columnar cacti Stenocereus pruinosus, Polaskia chichipe, Myrtillocactus schenckii, and Polaskia chende, species representing a gradient from higher to lower management intensity, respectively. We hypothesized that seeds from cultivated populations have higher water requirements to germinate than seeds of other populations, and that such difference is stronger in species more intensely managed. Germination was evaluated under water potential treatments at 0.0, ?0.2, and ?0.4 MPa. Interspecific differences were identified; germination rates markedly decreased in S. pruinosus and P. chichipe as water potential reduced. M. schenckii seeds germinated better at ?0.2 MPa, and seeds of P. chende in all treatments. Seed germination of wild and cultivated populations was similar in all cases and, therefore, at the population level domestication does not appear to have influenced variations in germination of the studied cacti species. However, experiments to test whether germination of seeds from plants with clear signs of domestication differs with seeds from other plants and their differential germination and seedling survival in wild, in situ-managed and cultivated environments could help to precise the influence of domestication on these plants. 相似文献
4.
Arif Mert Eker Mehmet Dikmen Selim Cambazoğlu Şebnem H.B. Düzgün 《International journal of geographical information science》2013,27(1):132-158
The purpose of this study was to investigate the capabilities of different landslide susceptibility methods by comparing their results statistically and spatially to select the best method that portrays the susceptibility zones for the Ulus district of the Bart?n province (northern Turkey). Susceptibility maps based on spatial regression (SR), linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), logistic regression (LR) method, and artificial neural network method (ANN) were generated, and the effect of each geomorphological parameter was determined. The landslide inventory map digitized from previous studies was used as a base map for landslide occurrence. All of the analyses were implemented with respect to landslides classified as rotational, active, and deeper than 5 m. Three different sets of data were used to produce nine explanatory variables (layers). The study area was divided into grids of 90 m × 90 m, and the ‘seed cell’ technique was applied to obtain statistically balanced population distribution over landslide inventory area. The constructed dataset was divided into two datasets as training and test. The initial assessment consisted of multicollinearity of explanatory variables. Empirical information entropy analysis was implemented to quantify the spatial distribution of the outcomes of these methods. Results of the analyses were validated by using success rate curve (SRC) and prediction rate curve (PRC) methods. Additionally, statistical and spatial comparisons of the results were performed to determine the most suitable susceptibility zonation method in this large-scale study area. In accordance with all these comparisons, it is concluded that ANN was the best method to represent landslide susceptibility throughout the study area with an acceptable processing time. 相似文献
5.
《Urban geography》2013,34(2):152-173
The current global housing policy, the enabling approach, emphasizes the need for governments to encourage community participation in the shelter sector. This research examines the role of the government and community-based organizations (CBOs) in the housing sector and analyzes how they interact. To determine whether governments and CBOs are participating in the shelter sector as advocated under the approach, this study examines the role of two CBOs engaged in upgrading shelter for the poor in Santo Domingo, the Dominican Republic. This research demonstrates that the enabling approach can be effective if the government is supportive and CBOs are engaged in the planning, decision-making, and implementation of the housing project. This study finds that cooperation between the implementing NGO, CBOs, and households is crucial for the success of the housing project. The study also demonstrates how the enabling policies employed in Santo Domingo, including low-cost labor and use of low-cost building materials, help overcome obstacles encountered under previous housing policies such as displacement and affordability issues. 相似文献
6.
《Journal of Arid Environments》1998,39(2):299-313
Temperate and semi-arid regions of Argentina are undergoing rapid habitat conversion as a result of several human activities (i.e. grazing, logging, agriculture, etc.). These arid ecosystems contain many endemic species and have played an important role in the evolution of South American biota. The Man and Biosphere Reserve of Ñacuñán (12,800 ha) is located in the central region of the lowland Monte Desert. The reserve is a stand within a highly disturbed matrix characterized by deforestation (i.e. mesquite,Prosopis)and overgrazing. Major vegetational and animal communities recovered after the reserve was fenced in 1972, and Ñacuñán thus provides critical data describing the recovery of biotic and abiotic components of the Monte Desert when anthropogenic assaults are minimized. Indeed, the Reserve of Ñacuñán protects many distinctive habitats of the Monte Desert, including mesquite forest, or algarrobal, and several representative animals of the South American biota (i.e. tinamous, rhea, marsupials, edentates and caviomorph rodents). Several research projects on community ecology, herbivory, disturbances, ecology and ecophysiology have been or are being developed in the reserve. Although the town of Ñacuñán lies within the reserve, the link between the research community and the local people has not been strong, persistent or effective. The reserve is the most important site in Argentina for monitoring the ecological health of the Monte Desert and for developing indicators of desertification. Its potential is great for long-term ecological research and for strengthening the infrastructure of science. Sustainable development in the next millennium requires integrating the activities of the research, local people, ranch landowners and governmental sectors so as to infuse science-based proposals into management and conservation initiatives. 相似文献
7.
Michael Gentile 《Urban geography》2013,34(10):1455-1464
ABSTRACTDespite the recent planetary turn that has swept through gentrification research, the theoretical barycentre remains pegged to a few strongholds located in the global north-west. Against this background, this essay offers a provincialized account of three gentrification-like trends – tele-urbanization, Schengtrification and colour-splashing – which are currently taking place in Tbilisi, Riga and Kiev. It is proposed that these processes are supported by an underlying logic that is not pinned to these cities’ specific (“post-communist”) contexts, raising questions about the avowedly universal validity of theories of gentrification stemming from the global northwest, and particularly those developed within the more critical scholarly tradition. 相似文献
8.
Limnological responses to warming on the Xizang Plateau,Tibet, over the past 200 years 总被引：1，自引：0，他引：1
Paleolimnological analyses can be used to evaluate limnological responses to changing climate over decadal to centennial timescales,
especially in regions with sparse lake monitoring data. We used a training set with 90 lakes to develop a diatom-based conductivity
transfer function and address climate-driven changes in lakes on the Qinghai-Xizang Plateau, Tibet. This new training set
is an expanded version of a previous model (Yang et al. in J Paleolimnol 30:1–19, 2003) and shows improved performance statistics for the conductivity model. The expanded training set also contains diatom species
not previously identified from the region, such as Stephanodiscus sp. and Cyclotella sp., which are common eutrophic indicator species in other regions, but can also be influenced by water column conductivity.
The new conductivity transfer function was applied to Lakes Nam Co and Chen Co in Tibet. Recent conductivity inferences were
compared with climate data from the Dangxiong weather station and water level records from Yangzhuyong Co, which show increasing
temperature and lower water levels, respectively, since AD 1960. Other studies showed that the water balance for many lakes
on the Qinghai-Xizang Plateau is complex, affected by both evaporation and glacial melting. Our paleolimnological reconstructions,
which include sediment particle size data, indicate that over relatively short timescales glacial meltwater can influence
lake hydrology, but over decadal timescales, increases in evaporation, driven by rising temperatures, dominate. Our findings
suggest that regional warming is lowering water levels at these sites and will continue to do so given predicted future climate
warming. 相似文献
9.
Ramesh Dhussa 《The Professional geographer》2013,65(2):312-313
In this article, we first replicate and then adapt an existing index of social vulnerability to hazard developed for the United States to a non-U.S. context. We construct indexes for Norwegian municipalities, describe the adjustment process, and compare the replicated and adapted assessments. Our results indicate only a moderate correlation between the replicated and adapted vulnerability indexes and for several municipalities the difference between the indexes is considerable. This demonstrates that context matters and that indexes of vulnerability need to be adapted rather than replicated. To facilitate such adaption processes, we identify three types of accommodation: conceptual, technical, and geographic. 相似文献
10.
Heike Jöns 《The Professional geographer》2017,69(4):670-682
This article examines the role of early female academics at the University of Cambridge in the production and dissemination of knowledge between 1926 and 1955. A statistical comparison of women's use of academic leave of absence with that of their male colleagues reveals that, across disciplines, women were less integrated into (inter)national knowledge networks and thus less visible in their epistemic communities than men because women focused their academic leaves more on research, rarely attended conferences, traveled overseas less often than men, and went more frequently to destinations within Europe than the United States as the new economic hegemon. Biographical case studies of these early female academics demonstrate the importance, variously, of their upper middle-class background, academic excellence, and familial and nonfamilial patronage in developing their careers, overcoming multiple hurdles, and producing intellectual contributions of equal quality to that of their male peers. Conceptually, this article calls for the inclusion of academic travelers from disciplines other than geography into feminist histories of geographical knowledge and argues that rather than stereotyping gender differences, greater comparative research on the experiences of female and male academics is needed to understand the mechanisms of gender inequality within the university. 相似文献
11.
12.
Nicholas L. Balascio Stephen Wickler 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(3):146-160
Integrated archaeological and paleoenvironmental investigations provide long-term perspectives on human–environment interactions. In the North Atlantic region, early human settlements were established in marginal agricultural environments and were susceptible to various environmental stressors. The Lofoten Islands have had an important role in the history of this region, particularly during the Iron Age, when Lofoten developed from pioneering agricultural settlements to a prominent node of power and trade under Viking chieftains. Iron Age developments in Lofoten were concurrent with significant natural environmental changes, including variations in climate and sea level. However, there has not been a comprehensive investigation of their influence on early settlements. The purpose of the study is to review Iron Age cultural developments in Lofoten using published archaeological data and paleoenvironmental records of past climate and sea-level change, and to present specific examples of the intersection of early human development and natural environmental changes. The findings show that climate changes probably influenced agricultural phases and that relative sea-level variations had important impacts on maritime developments. In conclusion, the findings demonstrate that human–environment interactions were significant factors in Lofoten’s history and the authors suggest specific areas for future research. 相似文献
13.
This article presents some of the findings of a multi-indicator investigation of the history of vegetational changes and land degradation in the Lake Baringo basin, Kenya, East Africa, during the Late Holocene. 14C- and 210Pb-dated record of the lithostratigraphy is used to reconstruct the paleoenvironment in the region of the lake. The stratigraphic record from Lake Baringo reveals the presence of two abrupt dry episodes at ca. AD 1650 and AD 1720 in east Africa that led to drying up of the lake. The record also shows evidence of a third period of desiccation at ca. AD 1880, which resulted in lowering of the lake level and is corroborated by oral tradition from the area. This article shows the potential of how the paleoenvironmental record can be combined with the historical record to understand East Africa's paleoenvironment. 相似文献
14.
Sedimentation rates in the Wanggang salt marshes, Jiangsu 总被引：1，自引：0，他引：1
WANGAijun GAOShu JIAJianjun PANShaoming 《地理学报(英文版)》2005,15(2):199-209
1 IntroductionLand-ocean interaction in coastalzone is one of the key m atters of the International G eosphereand Biosphere Program (IG BP). The key problem s of the second phase in the next decadeinclude the m aterial cycle, the system evolution process … 相似文献
15.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):193-197
Located at approximately 150 m above the present base level, the caves of Niaux, Lombrives and Sabart are an old drainage system, which worked between the Vicdessos and Ariège Valleys. In these caves, three successive sedimentary units were studied in detail. Each unit consists of two parts: the lower deposit is detrital, of fluvial origin, and testifies to a hydrological working of the conduit system; the upper deposit of each unit is mostly speleothems, corresponding to a draining of the conduits as the palcokarst evolved above base level. This is similar to the present environment of the caves. Only the speleothems from the upper part of each unit were dated by the 230Th/234 U method. The dates, from 27 samples, are in good agreement with Europe and North America data. The data from the middle (250 to 200 ka BP) and upper (90 to 20 ka BP) fluvial sediments correspond to major glacial events, which re-activated the karst system. Two further events resulted in a lack of carbonated sedimentation, the first between 350 and 290 ka BP, the second between 175 and 130 ka BP. Comparing the data from other places, these two events can be related to glacial periods of minor importance in the study area, because of the lack of erosion and of detrital sediments. The oldest detrital sediments are covered by speleothems older than 350 ka BP and, partly, older than 720 ka BP (from paleomagnctic data to be confirmed); from sedimentary data, they may not be related to a glacial event. They are perhaps contemporary with the area's initial cave formation. 相似文献
16.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3-4):165-174
The behaviour of the ice-dammed lake, Strupvatnet, Troms County, Norway, is described. Past observations are noted and related to observations in 1959 and to other ice-dammed lakes. Mechanisms for opening and maintaining water flow during a ‘hlaup’ are discussed. It is considered that Liestol's melt widening process operates after initiation by a pressure gradient across the dam. The lake and the internal drainage system of the glacier are thus linked. There is no evidence of lifting of the ice dam at Strupbreen. 相似文献
17.
Dominik Pawłowski Beata Gruszka Hanna Gallas Joanna Petera-Zganiacz 《Journal of Paleolimnology》2013,49(4):679-696
Upper Saalian (Illinoian) glaciolacustrine deposits in central Poland, preserved in a tectonic graben, were exposed in an opencast lignite mine and investigated using sedimentological and micro-paleontological methods. The extraglacial lake sediments provide the first records of late Saalian cladoceran communities in central Europe, recovered from glaciolacustrine deposits. Sedimentation was dominated by a supply of clastics that fluctuated with the seasons, forming rhythmites. In addition to seasonal cyclicity, sedimentary and environmental conditions changed every several years to decades, with periods of increased inflow to the lake delivering sandy material, and periods of almost stagnant water dominated by suspension settling. The sediments contain Cladocera assemblages that indicate the lake was initially deep, oligotrophic, and filled with moderately cold water. Changes in Cladocera community composition and abundance were perhaps responses to climate seasonality. Zones without Cladocera were associated with seasons of higher inflow and sediment supply, and directly or indirectly, with tectonic activity in the graben. Earthquakes, documented by the presence of seismites, caused not only deformation of unconsolidated lake-bottom sediments, but possibly also changes in habitat characteristics. Combined sedimentological and biological data were used to infer the lake’s history and show that deposits of glaciolacustrine lakes can be used as indicators of past ecological and climate changes. 相似文献
18.
Karin Holmgren Jan Risberg Johan Freudendahl Mussa Achimo Anneli Ekblom Joao Mugabe Elin Norstr?m Sandra Sitoe 《Journal of Paleolimnology》2012,48(2):311-322
Stratigraphic variations in diatom composition and phytolith abundance in a sediment core from a small, hydrologically isolated waterbody, Lake Nhauhache, Mozambique, provide evidence of water-level fluctuations over the past ~2,300?years. Ten AMS radiocarbon dates on bulk sediment samples show that the lake came into existence about 2,300?years ago and that it has dried out since then, but only for brief time periods. Changes in the diatom assemblage composition indicate that lake level fluctuated in response to shifting humidity conditions. The changes reflect wetter conditions ca. 300 BC?CAD 800, more variable conditions between AD 800 and 1150, a distinct dry phase within the time span AD 1150?C1700 and a return thereafter to more humid conditions until present. There is general agreement between the Lake Nhauhache record and other records from the Southern Hemisphere summer rainfall region. This suggests that sediments from small interdunal lakes, which are abundant along the coast of southern Africa, provide reliable, regional paleoenvironmental information about an area from which more such data are needed. 相似文献
19.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(1-2):47-51
During The summers of 1957 and 1958 the junior author served as glacial geologist with the Swedish Glaciological Expedition to Nordaustlandet (North-East Land), Spitsbergen (Fig. 1). One of the main objectives was to establish an absolute chronology of events leading to the partial deglaciation of this island. 相似文献
20.