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991.
An assessment was made of the mean levels of major and trace elements and of biogenic and organic matter in glacial and river waters within the Aktru river basin (Gornyi Altai, Russia). The analysis showed a general tendency for an increase in mineralization along the direction from the region of alimentation of glaciers to the mouth of the river. A relatively abrupt increase was revealed in Al, Zn, Cu, Pb, Si, NO2 ? and NH4 + concentrations in the source of the Aktru river and its glacial tributaries, with their subsequent decrease downstream. The mechanism for such changes is governed by the conditions of interaction of rocks with meltwaters and river waters. 相似文献
992.
A. Geddes D.A. Elston M.E.A. Hodgson R. V. Birnie 《International journal of geographical information science》2013,27(4):785-803
Handling of uncertainty in the estimation of values from source areas to target areas poses a challenge in areal interpolation research. Stochastic model-based methods offer a basis for incorporating such uncertainty, but to date they have not been widely adopted by the GIS community. In this article, we propose one use of such methods based in the problem of interpolating count data from a source set of zones (parishes) to a more widely used target zone geography (postcode sectors). The model developed also uses ancillary statistical count data for a third set of areas nested within both source and target zones. The interpolation procedure was implemented within a Bayesian statistical framework using Markov chain Monte Carlo methods, enabling us to take account of all sources of uncertainty included in the model. Distributions of estimated values at the target zone level are presented using both summary statistics and as individual realisations selected to illustrate the degree of uncertainty in the interpolation results. We aim to describe the use of such stochastic approaches in an accessible way and to highlight the need for quantifying estimation uncertainty arising in areal interpolation, especially given the implications arising when interpolated values are used in subsequent analyses of relationships. 相似文献
993.
The Haji-Gak iron deposit of eastern Bamyan Province, eastern Afghanistan, was studied extensively and resource calculations
were made in the 1960s by Afghan and Russian geologists. Recalculation of the resource estimates verifies the original estimates
for categories A (in-place resources known in detail), B (in-place resources known in moderate detail), and C1 (in-place resources estimated on sparse data), totaling 110.8 Mt, or about 6% of the resources as being supportable for the
methods used in the 1960s. C2 (based on a loose exploration grid with little data) resources are based on one ore grade from one drill hole, and P2 (prognosis) resources are based on field observations, field measurements, and an ore grade derived from averaging grades
from three better sampled ore bodies. C2 and P2 resources are 1,659.1 Mt or about 94% of the total resources in the deposit. The vast P2 resources have not been drilled or sampled to confirm their extent or quality. The purpose of this article is to independently
evaluate the resources of the Haji-Gak iron deposit by using the available geologic and mineral resource information including
geologic maps and cross sections, sampling data, and the analog-estimating techniques of the 1960s to determine the size and
tenor of the deposit. 相似文献
994.
995.
We provide a rationale for the technique of revaluating the natural-resource potential which is built upon the natural crop
yield of Ukrainian lands obtained, with the observance of rotation cropping and by implementing the complex of mechanical
tillage operations without fertilizer application. An assessment is made of Ukraine’s natural-resource potential within the
context of three physical-geographical countries, four zones, three subzones, and 14 krais. 相似文献
996.
S. Fracchia L. KrapovickasA. Aranda-Rickert V.S. Valentinuzzi 《Journal of Arid Environments》2011,75(11):1016-1023
In arid and semi-arid environments, root-associated fungi may play a key role in plant communities (e.g., seedling establishment, nutrient acquisition, plant survival and heat tolerance). Several studies have shown the importance of small mammals as consumers and dispersal agents of mycorrhizal fungi spores in tropical and temperate ecosystems. However, little is known about the dispersal of infective propagules of endophytic fungi in arid and semi-arid ecosystems. This study analyzed the potential role of the subterranean rodent Ctenomys cf. knighti as a dispersal agent of root-associated fungi. In order to demonstrate this role, we analyzed: (1) the incidence of colonization of arbuscular mycorrhizae and dark septate endophytes on representative plant species of the Monte Desert; (2) the presence of fungal structures of arbuscular mycorrhizae and dark septate endophytes in C. cf. knighti fecal samples; and (3) the infectivity of the fungal propagules contained in the scat and their growth effects on nine native plant species. Data strongly suggest that this South American subterranean rodent may play a key role as a dispersal agent of arbuscular mycorrhizae and dark septate endophytes fungi in the arid environment of the northern Monte Desert of Argentina. 相似文献
997.
Adrian M. Shrader Joel S. Brown Graham I.H. Kerley Burt P. Kotler 《Journal of Arid Environments》2008,72(10):1811-1819
One factor that influences foraging is predation risk. As a result, herbivores may not use landscapes uniformly due to spatial differences in perceived predation risk. Wild herbivores forage across these ‘landscapes of fear’; however, the extent to which domestic herbivores consider them is generally unknown. Using a grid of artificial food patches and measuring giving up densities (GUDs), we mapped landscapes of fear of free-ranging domestic goats on three substrates. In the first experiment, we related GUDs to landscape variables. Goats preferred feeding in open ground with firm substrate compared to a sandy riverbed or a rocky hillside. We suggest that differences relate to escape potential and the occurrence of ambush sites. Landscape variables that influenced feeding effort were patch visibility and plants next to a patch. In a second experiment, we increased predation risk by adding predator dung and urine into the habitats. In response, feeding effort declined across all three habitats. Furthermore, goats only responded to patch visibility and not plants next to the patches. Better sightlines increase predator detection and allow individuals to see group members. Our results indicate that predation risk influences the extent to which free-ranging domestic herbivores utilise landscapes. 相似文献
998.
This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from
the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate
signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 14C yr BP to 11,100 14C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 14C yr BP and finally, at 8,500 14C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500
14C yr BP) to deciduous parkland, followed by grassland at 9,300 14C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent
uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and
geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting
of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused
the lower-elevation Wendel site to capture the ground water of up-gradient lakes. 相似文献
999.
Pirogova A. S. Tikhotskii S. A. Tokarev M. Yu. Suchkova A. V. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(11):1755-1765
Izvestiya, Atmospheric and Oceanic Physics - This paper provides an overview of several seismic inversion approaches and their application to very- and ultra-high-resolution marine seismic... 相似文献
1000.