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Atmosphere-borne acidic pollutants constitute an important, potentially critical, risk to aquatic ecosystems. Long-time series
datasets are a requirement in the assessment of the biological impacts of both increased and decreased loadings of acidic
pollutants and allow for the anticipation of future pollution loadings and their effects that can be acted upon with some
confidence. Little is known concerning levels of deposition of atmospheric pollutants and their effects on acid-sensitive
aquatic ecosystems in Ireland. Moreover, unequivocal evidence of acidification by atmospheric deposition is limited. The objective
of this study was to provide a preliminary assessment of pH response in three lake sites that are situated in acid-sensitive
areas of Ireland, and to determine whether pH response tends to be uniform or differs due to variations in atmospheric loading
and catchment properties. Levels of spheroidal carbonaceous particle (SCP) deposition have been used as a general indicator
of the timing and extent of atmospheric pollutant loading and ecosystem response has been assessed by estimating diatom-inferred
pH with a weighted-averaging calibration model (72 lakes) developed specifically for the Irish ecoregion. Levels of diatom-inferred
pH (DI-pH) appear to respond to increased and decreased levels of atmospheric pollution loads—as represented by SCPs—at two
of the three sites examined in the east and west of Ireland. In contrast, the site situated in the southwest of Ireland showed
a varying and less directional DI-pH response, possibly due to lower deposition pressures, large lake size, and more buffered
edaphic geology. 相似文献
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Roland Pape 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(4):230-246
Due to increasing anthropogenic habitat alteration, fragmentation, and loss, the analysis of how, when, and why animals select particular habitats has become a central issue in ecology and biogeography. Animals adapt to spatiotemporal variability in resources either by tracking these resources or by plasticity in behavior to cover their needs, leading to three important implications: movement, temporal variation, and individual trade-offs leading to intra-species variability, all of which are directly linked to the use of space by animals. Based on GPS-tracking of domesticated reindeer in southern Norway, the authors addressed these issues by analyzing movement patterns and space use simultaneously across different temporal and organizational scales. Emerging information about the space use by reindeer was found explicitly linked to scaling relations, reflecting the matter of scale as having important functional implications rather than solely being a technical question of extent and resolution. Adding movement into the analysis of space use further advances the necessary functional perspective on space use. The authors conclude that scaling not only space but also time and the organizational level, in combination with accounting for different behavioral states, brings biogeography closer to a process-based view, rather than solely pattern-based view. 相似文献
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Cropland displacement, as an important characteristic of cropland change, places more emphasis on changes in spatial location than on quantity. The effects of cropland displacement on global and regional food production are of general concern in the context of urban expansion. Few studies have explored scale-effects, however, where cropland is displaced not only within, but also outside, the administrative boundary of a certain region. This study used a spatially explicit model (LANDSCAPE) to simulate the potential cropland displacement caused by urban land expansion from 2020 to 2040 at four scales of the Chinese administration system (national, provincial, municipal, and county levels). The corresponding changes in potential cereal production were then assessed by combining cereal productivity data. The results show that 4700 km2 of cropland will be occupied by urban expansion by 2040, and the same amount of cropland will be supplemented by forest, grassland, wetland, and unused land. The potential loss of cropland will result in the loss of 3.838×106 tons of cereal production, and the additional cropland will bring 3.546×106 tons, 3.831×106 tons, 3.836×106 tons, and 3.528×106 tons of potential cereal production in SN (national scale), SP (provincial scale), SM (municipal scale), and SC (county scale), respectively. Both SN and SC are observed to make a huge difference in cereal productivity between the lost and the supplemented cropland. We suggest that China should focus on the spatial allocation of cropland during large-scale displacement, especially at the national level. 相似文献
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W.H. Maes W.M.J. Achten B. Reubens D. Raes R. Samson B. Muys 《Journal of Arid Environments》2009,73(10):877-884
Although Jatropha curcas, an important tropical biofuel crop, is reputed for its drought resistance, its ability to perform under dry conditions has hardly been investigated. In a greenhouse experiment we investigated the plant–water relationships of Jatropha seedlings from different accessions under different levels of drought stress. There was little difference in plant–water relations between accessions. Drought significantly reduced leaf area, biomass and relative growth rate, but had no effect on specific leaf area, daily range in leaf water potential, leaf water content, transpiration efficiency or aboveground biomass water productivity, corrected for atmospheric conditions. Stem wood density was equally low (0.26 g cm?3) for all treatments. Stem water content was lowest for dry treatment seedlings. Based on these results, Jatropha could be characterized as a stem-succulent tree. In contrast to other stem-succulent deciduous trees, leaves were not shed immediately after the seedlings were confronted with drought. Instead, at the onset of drought, leaves with a higher adaxial stomatal density were formed, after which leaves were only gradually shed. The role of the succulent stem in the water economy of Jatropha was confined to balancing the small water losses of the leaves during drought. 相似文献
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In Nepal, changing demographic patterns are leading to changes in land use. The high level of outmigration of men in the hills of Kaski District, Western Development Region of Nepal, is affecting the household structure but also land management. Land is often abandoned, as the burden on those left behind is too high. How do these developments affect the state of the land in terms of land degradation? To find out, we studied land degradation, land abandonment caused by outmigration, and existing sustainable land management practices in a subwatershed in Kaski District. Mapping was done using the methodology of the World Overview of Conservation Approaches and Technologies (WOCAT). While previous studies expected land abandonment to exacerbate slope erosion, we demonstrate in this paper that it is in fact leading to an increase in vegetation cover due to favourable conditions for ecosystem recovery. However, negative impacts are several, including the increase of invasive species harmful to livestock and a decline in soil fertility. Traditional land management practices such as terraces and forest management exist. To date, however, these measures fail to take account of the changing population dynamics in the region, making the question of how migration and land degradation are linked worth revisiting. 相似文献
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Yongze Song Peng Wu Xiangyu Wang 《International journal of geographical information science》2018,32(12):2447-2476
Urban forms reflect spatial structures of cities, which have been consciously and dramatically changing in China. Fast urbanisation may lead to similar urban forms due to similar habits and strategies of city planning. However, whether urban forms in China are identical or significantly different has not been empirically investigated. In this paper, urban forms are investigated based on two spatial units: city and block. The boundaries of natural cities in terms of the density of human settlements and activities are delineated with the concept of ‘redefined city’ using points of interests (POIs), and blocks are determined by road networks. Urban forms are characterised by city-block two-level spatial morphologies. Further, redefined cities are classified into four hierarchies to examine the effects of different city development stages on urban forms. The spatial morphology is explained by urbanisation variables to understand the effects. Results show that the urban forms are spatially clustered from the perspective of city-block two-level morphologies. Urban forms tend to be similar within the same hierarchies, but significantly varied among different hierarchies, which is closely related to the development stages. Additionally, the spatial dimensional indicators of urbanisation could explain 41% of the spatial morphology of redefined cities. 相似文献
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James B. Elsner 《The Professional geographer》2013,65(4):559-560
Books reviewed: Bassin, Mark, Imperial Visions: Nationalist Imagination and Geographical Expansion in the Russian Far East, 1840 – 1865 Shortridge, James R., Our Town on the Plains: J. J. Pennell's Photographs of Junction City, Kansas, 1893 – 1922 Jakle, John A. and Sculle, Keith A., Fast Food: Roadside Restaurants in the Automobile Age Boeschenstein, Walter, Historic American Towns along the Atlantic Coast McKee, Jesse O., Ethnicity in Contemporary America: A Geographical Appraisal Luciuk, Lubomyr Y., Searching for Place: Ukrainian Displaced Persons, Ottawa, and the Migration of Memory Hausladen, Gary, Places for Dead Bodies Phillips, Richard, Watt, Diane and Shuttleton, David, De-Centering Sexualities: Politics and Representations beyond the Metropolis Goldin, Liliana R., Identities on the Move, Transnational Processes in North America and the Caribbean Basin McDonald, David A., On Borders: Perspectives on International Migration in Southern Africa Fox, Roddy and Rowntree, Kate, The Geography of South Africa in a Changing World Takeuchi, Keiichi, Modern Japanese Geography: An Intellectual History Amery, Hussein A., and Wolf, Aaron T., Water in the Middle East: A Geography of Peace Karl, Thomas R., Nicholls, Neville and Ghazi, Anver, Weather and Climate Extremes: Changes, Variations, and a Perspective from the Insurance Industry Pittman, Blair, Texas Caves 相似文献
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Høgni Kalsø Hansen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2015,115(2):105-118
Contemporary studies in urban and regional development stress the importance of large city-regions as key places in modern capitalism taking the form of agglomerations of economic activities by industries, firms and highly skilled people. In this article, we challenge the strong focus on academic human capital in understanding regional growth. We examine to what extent different labour competences and capabilities relate to municipal employment growth using nine stratified, educational categories as proxies for different levels of human capital. Dividing municipalities into four spatial categories ranging from the urban to the peripheral, we conclude that there is a strong spatial distinction of educational structures with an urban bias, and that educational categories other than academic human capital can make an important contribution to our understanding of what drives employment growth on the municipal level. 相似文献