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排序方式: 共有95条查询结果,搜索用时 62 毫秒
51.
小灵猫的引种驯化技术研究   总被引:1,自引:1,他引:0  
本文介绍了野生小灵猫捕捉的时间、地点和方法;提出了小灵猫的引种与驯化技术.  相似文献   
52.
A unique long term, 49-year record (divided into three time periods 1961–1976, 1977–1992, and 1993–2009) of snow profile stratigraphy from the Swedish sub Arctic, was analyzed with a focus on changes in snow characteristics. The data set contained grain size, snow layer hardness, grain compactness, and snow layer dryness, observed every second week during the winter season. The results showed an increase in very hard snow layers, with harder snow in early winter and more moist snow during spring. There was a striking increase in the number of observations with very hard snow at ground level over time. More than twice as many occasions with hard snow at ground level were observed between 1993 and 2009 compared to previous years, which may have a significant effect on plants and animals. The changes in snow characteristics are most likely a result of the increasing temperatures during the start and the end of the snow season.  相似文献   
53.

Liver samples of 42 birds belonging to 6 species of Ciconiiformes (grey heron (n = 17), little egret (n = 12), cattle egret (n = 1), glossy ibis (n = 1), little bittern (n = 1), and white stork (n = 10)), collected from two different zones of Spain (Ebro Delta and Madrid) in 1992–1997, were analyzed for organochlorine pesticides and PCBs. ΣPCBs (sum of concentrations of individual congeners), p,p′-DDE, HCB, γ-HCH, and heptachlor epoxide were the most prevalent residues detected in all samples (occurrence > 95%). There were no statistically significant differences in organochlorine levels between grey herons and little egrets, while levels of ΣPCBs, p,p′-DDE, HCB, γ-HCH, and heptachlor were significantly lower for white storks. These results could be explained by the different habitat of these species, aquatic in the Ebro Delta (grey herons, little egrets) and dry in Madrid (white stork), and their diverse feeding habits.  相似文献   
54.
Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20–30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (≥4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees ≥100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988–99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.  相似文献   
55.
We studied the impact of industrial pollution on population demography (age structure), growth and reproduction of crowberry, Empetrum nigrum L. Crowberry growing in severely polluted sites near non-ferrous smelters (at Harjavalta, Monchegorsk and Nikel) was on average twice as old as in unpolluted habitats, as indicated by the number of annual rings at root collar. Shoot length decreased both with plant ageing and due to pollution impact, while neither the proportion of generative plants nor berry production was affected by pollution or plant age. Our results suggest that death of the extant individuals of E. nigrum near the non-ferrous smelters is to a large extent explained by age-related damage of the main stem accelerated by pollution. Since vegetative propagation, seed germination and seedling establishment are hampered by soil toxicity, E. nigrum populations near the smelters continue to decline with ageing in spite of the gradual decline of emissions.  相似文献   
56.

Problem

The purpose of this research was to examine the impact of age and health on patterns of driving and self-regulation among older adults who still drive.

Method

This analysis presents the results of a nationwide survey of drivers who are 50 + (N = 3,824, 53.11% response rate), focusing on questions about the impact of their self-reported health on attitudes toward and self-regulation of driving.

Results

The data indicate that as age increases, so too does reported self-regulation of driving, increasing sharply among those ages 70 and older. The data also indicate that respondent's reported confidence in driving and their enjoyment of driving decline as they age. Health status bears a significant relationship with all three of these variables, positively related to confidence in driving skills and to enjoyment in driving, but negatively related to self-regulation reports. As self-reported health declines, respondent's report engages in greater voluntary restrictions of their driving.

Discussion

All too often, the driving decision is linked primarily to chronological age. Analysis done here indicates that age alone is not the best indicator of self-regulation and how older adults change their driving behaviors.

Summary

This research presents the results of a nationwide survey of 50+ drivers and their self-reported driving, self-regulation behaviors, and health status. Strong support was found for the argument that chronological age is not an adequate measure of self-regulating behaviors and driver safety among those 50+. In particular, it was found that a person's health status and the interaction between age and health are essential considerations in the decisions around self-regulation and driving. People tend to self-regulate more with age, but the effect becomes much more pronounced as health status declines.

Impact on industry

In the coming years, if older adults can't get to where they want to go and continue to be viable consumers in our national fabric, all industries will eventually suffer. Transportation is a key component to the nation's social contract with older individuals and their families.  相似文献   
57.
A dynamic model of radionuclide accumulation in fish is developed. In the model, the fish population is represented by a set of discrete age classes. Each age class is characterized by a specific growth rate, diet and activity of metabolic processes. The model describes all known types of size effect in the contamination of fish with radiocaesium. The detailed dynamics of 137Cs accumulation by fish are demonstrated using the results of the model's application to ichtiofauna in a water body which has a high level of contamination with radiocaesium — namely, the cooling pond of the Chernobyl NPP.  相似文献   
58.
How do climate fluctuations affect DDT and hexachlorocyclohexane (HCH) distribution in the global scale? In this study, the interactions between climate variations and depositions of DDT and HCH in ice cores from Mt. Everest (the Tibetan Plateau), Mt. Muztagata (the eastern Pamirs) and the Rocky Mountains were investigated. All data regarding DDT/HCH deposition were obtained from the published results. Concentrations of DDT and HCH in an ice core from Mt. Everest were associated with the El Nino-Southern Oscillation. Concentrations of DDT in an ice core from Mt. Muztagata were significantly correlated with the Siberia High pattern. Concentrations of HCH in an ice core from Snow Dome of the Rocky Mountains responded to the North Atlantic Oscillation. These associations suggested that there are some linkages between climate variations and the global distribution of persistent organic pollutants.  相似文献   
59.
Organochlorines are found even in organisms living in remote areas such as the Arctic marginal ice zone. Organochlorine concentrations in ice-associated (sympagic) amphipods are related to their diet. Therefore, the size-dependent diet shift of Gammarus wilkitzkii may influence its organochlorine content. In this preliminary study, the organochlorine concentrations in two size classes (small 29 mm and large >29 mm) of G. wilkitzkii were analysed. The concentrations of more lipophilic compounds [e.g. polychlorinated biphenyls (PCBs)] were lower in the small than the large size class, whereas concentrations of less lipophilic compounds [e.g. hexachlorocyclohexanes (HCHs)] did not differ by size class.

Since contamination transport by the atmosphere, ocean currents and sea ice may vary, the organochlorine burden in sympagic organisms may also vary. There are no data available on temporal variation of organochlorine burden in Arctic sympagic fauna. Therefore, we compared organochlorine concentrations in sympagic amphipods (G. wilkitzkii, Apherusa glacialis and Onisimus spp.) between 1998 and 1999. Organochlorine concentrations in all amphipods were low in both years, with sum organochlorines from 50.7 to 621.9 ng g−1 lipid weight. The concentrations of hexachlorobenzene (HCB), chlordanes, DDTs and PCBs were higher in 1999 than 1998, whereas the HCH concentrations were lower in 1999 than 1998. The organochlorine concentrations differed between the taxa in both years in a similar increasing manner from A. glacialis to both G. wilkitzkii and Onisimus spp.

In studies of bioaccumulation relative to body size and temporal variation, a thorough interpretation requires samples from several size classes and years. Nevertheless, the present data provide new knowledge on contaminants in Arctic invertebrates where data are scarce.  相似文献   

60.
The rapid developments in all kinds of new information technologies, information networks and social media are increasingly affecting societies around the world. The so termed Information Age not only influences social relationships, economy and science, but also governance. Against this background and in the specific field of sustainability, informational governance is an emerging concept. It addresses two interrelated processes: (1) new forms of governing through information, and (2) transformative changes in governance institutions due to the new information flows. The aim of this article is to gain more insights into ways in which the Information Age impacts sustainability, and to suggest a research agenda with relevance to the field of informational governance. A systematic literature review resulted in a selection of 39 articles, of which 23 and 16 articles were identified in two-parallel searches. The increased human interconnectedness through e-governance, self-organization, private governing and empowerments are identified as core informational governance trends dealing with sustainability in the Information Age, and essential to future research.  相似文献   
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