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991.
Although most UK sand dune systems are now fossilized, with little mobility and reducing amounts of bare sand, they support
important populations and assemblages of terrestrial invertebrates. Offering open conditions, warm substrates and a range
of habitats and habitat structures, they have become increasingly significant as other coastal habitats have been lost. In
Wales, 680 Red Data Book and Nationally Scarce species have been recorded from dunes. 109 species in the UK are restricted
to dunes, and in Wales there are an additional 145 species confined to dunes and 208 species strongly associated with dunes.
Of these, 172 species are dependent upon bare and sparsely-vegetated sand, in grey dunes and early-successional dune grassland,
at some stage of their life cycle, rising to 292 species if those associated with the strandline, foredunes, yellow dunes
and pioneer dune slacks are included, equating to 63% of the 462 dune species. Bees and wasps are particularly well represented,
with 278 species (68% of the Welsh fauna) recorded on Welsh dunes, including 17 obligates and 44 species with a strong dependence,
52 of which are associated with bare and sparsely-vegetated sand. Key to maintaining invertebrate populations on UK dunes
is the provision of bare sand but in Wales, bare sand accounts for only 1.7% of the total sand dune resource. As a more appropriate
bare sand threshold is likely to range between 10 and 30%, radical action is required to re-mobilize at least the key sand
dune systems. 相似文献
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996.
The spatiotemporal dynamics of forest-tundra communities in the 20th century have been studied in the timberline ecotone of the Polar Urals. Maps reflecting the distribution of different types of forest-tundra communities have been made, and data on the morphological and age structure of tree stands have been obtained for three time sections (the mid-1910s, 1960s, and 2000s). They show that open and closed forests have markedly expanded due to natural afforestation of the tundra and increase in the density and productivity of existing forest stands. The unidirectional pattern of plant community transition (from the tundra to closed forests) and meteorological data provide evidence that this transition has been conditioned by climate warming and increasing humidity recorded during the past 90 years.Translated from Ekologiya, No. 2, 2005, pp. 83–90.Original Russian Text Copyright © 2005 by Shiyatov, Terentev, Fomin. 相似文献
997.
G. D. Kataev 《Russian Journal of Ecology》2005,36(6):421-426
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact. 相似文献
998.
Risk assessment of landfill disposal sites--State of the art 总被引:1,自引:0,他引:1
A risk assessment process can assist in drawing a cost-effective compromise between economic and environmental costs, thereby assuring that the philosophy of 'sustainable development' is adhered to. Nowadays risk analysis is in wide use to effectively manage environmental issues. Risk assessment is also applied to other subjects including health and safety, food, finance, ecology and epidemiology. The literature review of environmental risk assessments in general and risk assessment approaches particularly regarding landfill disposal sites undertaken by the authors, reveals that an integrated risk assessment methodology for landfill gas, leachate or degraded waste does not exist. A range of knowledge gaps is discovered in the literature reviewed to date. From the perspective of landfill leachate, this paper identifies the extent to which various risk analysis aspects are absent in the existing approaches. 相似文献
999.
S. K. Jain G. N. Yoganarasimhan S. M. Seth 《Journal of the American Water Resources Association》1992,28(6):1037-1043
ABSTRACT: Many approaches are available for operation of a multipurpose reservoir during flood season; one of them is allocation of storage space for flood control. A methodology to determine a reservoir operation policy based on explicit risk consideration is presented. The objective of the formulation is to maximize the reservoir storage at the end of a flood season while ensuring that the risk of an overflow is within acceptable limits. The Dynamic Programming technique has been used to solve the problem. This approach has been applied to develop operation policies for an existing reservoir. The performance of the policy was evaluated through simulation and was found to be satisfactory. 相似文献
1000.
Body (thorax and prosoma) weight, shell growth, and Zn, Cu, Fe, Mn and Ca levels were measured in artificially settled Elminius modestus over a 14-month period following transfer to high, mid and low tide positions in the uncontaminated Menai Strait and two mid tide sites within a Zn and Cu polluted bay on the North West coast of Anglesey. Barnacles showed higher mortality and slower growth at the upper shore position than at any other site. There was no evidence of Zn and Cu regulation by the bodies or shells, and both seemed to reflect environmental levels. Body metal levels were lowest in early winter and the highest second year values were found in January (Zn), March (Cu, Fe) or May (Ca). Higher shore barnacles contained larger concentrations of Zn than mid or low tide animals. Differences in feeding activity and the amount of testes may account for these variations. Reciprocal transplants between polluted and 'clean' sites indicate that body Cu and Zn accumulation and loss was very rapid. Spatial and temporal changes in shell metal levels closely mirror that of the body. 相似文献