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91.
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Jordi Figuerola Iris Charalambidou Luis Santamaria Andy J. Green 《Die Naturwissenschaften》2010,97(6):555-565
Long distance dispersal may have important consequences for gene flow and community structure. The dispersal of many plants
depends on transport by vertebrate seed dispersers. The shapes of seed shadows produced by vertebrates depend both on movement
patterns of the dispersers and on the dynamics and effects of passage through the disperser’s gut (i.e. the retention time,
survival and germination of ingested seeds). A combination of experiments with captive waterbirds and aquatic plant seeds
was used to analyse the following: (a) the effects of inter- and intra-specific variation in seed size and duck species on
seed retention time in the gut and (b) the relationship between retention time and the percent germination and germination
rates of seeds. Among the three Scirpus species used, those with smaller seeds showed higher survival after ingestion by birds and longer retention times inside
their guts than those with larger seeds. For Potamogeton pectinatus, only seeds from the smaller size class (<8 mg) survived ingestion. Retention time affected the percent germination and germination
rate of Scirpus seeds but in a manner that varied for the different plant and bird species studied. We recorded both linear and non-linear
effects of retention time on percent germination. In addition, germination rate was positively correlated with retention time
in Scirpus litoralis but negatively correlated in Scirpus lacustris. Small seed size can favour dispersal over larger distances. However, the effects of retention time on percent germination
can modify the seed shadows produced by birds due to higher percent germination of seeds retained for short or intermediate
periods. The changes in dispersal quality associated with dispersal distance (which is expected to be positively related to
retention time) will affect the probability of seedling establishment over longer distances and, thus, the spatial characteristics
of the effective seed shadow. 相似文献
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Peng Ying Zhou Fengwu Cui Jian Du Ke Leng Qiangmei Yang Fumo Chan Andy Zhao Hongting 《Environmental science and pollution research international》2017,24(19):16206-16219
Environmental Science and Pollution Research - The Three Gorges Dam’s construction and industrial transfer have resulted in a new air pollution pattern with the potential to threaten the... 相似文献
95.
Andy Spoerri Daniel J. Lang Beat Staeubli Roland W. Scholz 《Waste management (New York, N.Y.)》2010,30(7):1382-1394
Understanding technological change provides a crucial basis for governing sustainability transitions. In this paper we present an analysis of technological change using the example of Swiss thermal waste processing. In recent years, increased concerns about the low quality of residues from grate-firing systems led to the examination of alternative technologies. Yet despite clear indications of a potential better performance with respect to residue quality, none of these alternatives has been adopted. Based on a two-stage knowledge integration among 15 leading experts, in a retrospective analysis we identified factors that have significantly affected technological change in Swiss thermal waste processing. These factors were then related to three technological options representing different types of technological change, i.e., from incremental improvements of the existing to the implementation of a new technology. The results indicate that technological change is currently in a technological lock-in and provide detailed insights on the causes. The lock-in results in the step-wise further development of the status quo grate-firing system despite its limitations for improving the residue qualities. Almost all factors (legal, economic, societal, technological) of the existing ‘thermal waste management’ system have been well adapted to the cost- and energy-efficient grate-firing technology, blocking innovative technologies from entering the Swiss market. In addition, pressures from the context, e.g., societal pressure related to landfill risks, have not been strong enough to promote non-incremental change. 相似文献
96.
Jones A 《Environmental management》2002,30(4):560-576
The contemporary food system provides consumers with convenience, extensive choice, and the year-round availability of fresh
produce. In this paper these achievements are recognized within the context of the associated environmental impacts. While
many analyses have considered the energy and material efficiency of various options for food production and packaging, very
few studies have investigated the environmental impacts of the transport components of food supply chains. This is surprising,
given that the global sourcing of food produce, centralized distribution systems, and shopping by car have become prevalent
in recent decades and have contributed to an increase in the distance between producer and consumer or “food miles.”
In a case study the transport energy consumption is calculated for all possible ways in which dessert apples can be supplied
to the UK consumer. The aim is to assess the environmental performance of the predominant fresh produce supply chains and
to investigate claims that localized systems are more environmentally efficient. The main criteria used to compare the environmental
efficiency in alternative food supply chains are the transport-related fossil-fuel energy consumption and associated carbon
dioxide emissions.
Analysis of the empirical data shows that transportation is now responsible for a considerable fraction of the total energy
consumption in the life cycle of fresh apples, and in most cases exceeds the energy consumed in commercial apple cultivation.
By developing local production and marketing systems for fresh products, transport demand can be reduced and many of the environmental
impacts associated with existing supply chains can be avoided. The results of the study are then discussed in relation to
the wider issues of transport policy, international trade, food security, and product-related environmental information for
consumers. 相似文献
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Fourteen (2.5 per cent) of 568 chromosome preparations after CVS showed discrepancies between the placental and fetal karyotype, mainly due to placental mosaicism. The presence of a second cell line within the placenta was confirmed in all but one case, in which cytogenetic reinvestigations were carried out. Our clinical data indicate that severe developmental retardation in the newborn is not to be expected if only the placenta carries the chromosomally abnormal cell line. 相似文献