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171.
Climate change coupled with increasing demands for water necessitates an improved understanding of the water–food nexus at a scale local enough to inform farmer adaptations. Such assessments are particularly important for nations with significant small-scale farming and high spatial variability in climate, such as Sri Lanka. By comparing historical patterns of irrigation water requirements (IWRs) to rice planting records, we estimate that shifting rice planting dates to earlier in the season could yield water savings of up to 6%. Our findings demonstrate the potential of low-cost adaptation strategies to help meet crop production demands in water-scarce environments. This local-scale assessment of IWRs in Sri Lanka highlights the value of using historical data to inform agricultural management of water resources when high-skilled forecasts are not available. Given national policies prioritizing in-country production and farmers’ sensitivities to water stress, decision-makers should consider local degrees of climate variability in institutional design of irrigation management structures. 相似文献
172.
173.
Conservation Biology for the Biodiversity Crisis 总被引:12,自引:0,他引:12
174.
175.
Edith Gego Christian Hogrefe George Kallos Antigoni Voudouri John S. Irwin S. Trivikrama Rao 《Environmental Fluid Mechanics》2005,5(1-2):63-85
While fluctuations in meteorological and air quality variables occur on a continuum of spatial scales, the horizontal grid spacing of coupled meteorological and photochemical models sets a lower limit on the spatial scales that they can resolve. However, both computational costs and data requirements increase significantly with increasing grid resolution. Therefore, it is important to examine, for any given application, whether the expected benefit of increased grid resolution justifies the extra costs. In this study, we examine temperature and ozone observations and model predictions for three high ozone episodes that occurred over the northeastern United States during the summer of 1995. In the first set of simulations, the meteorological model RAMS4a was run with three two-way nested grids of 108/36/12 km grid spacing covering the United States and the photochemical model UAM-V was run with two grids of 36/12 km grid spacing covering the eastern United States. In the second set of simulations, RAMS4a was run with four two-way nested grids of 108/36/12/4 km grid spacing and UAM-V was run with three grids of 36/12/4 km grid spacing with the finest resolution covering the northeastern United States. Our analysis focuses on the comparison of model predictions for the finest grid domain of the simulations, namely, the region overlapping the 12 km and 4 km domains. A comparison of 12 km versus 4 km fields shows that the increased grid resolution leads to finer texture in the model predictions; however, comparisons of model predictions with observations do not reveal the expected improvement in the predictions. While high-resolution modeling has scientific merit and potential uses, the currently available monitoring networks, in conjunction with the scarceness of highly resolved spatial input data and the limitations of model formulation, do not allow confirmation of the expected superiority of the high-resolution model predictions.The U.S. Governments right to retain a non-exclusive royalty-free licence in and to any copyright is acknowledged. 相似文献
176.
Following uptake of technetium-95m and americium-241 by lobsters (Homarus gammarus) from food, the subcellular distribution and binding in the major organ of accumulation, the digestive gland, were analysed.95mTc was predominantly bound to soluble proteins; approximately 40% was bound to two proteins displaying the same elution characteristics as Cdthioneins as indicated by gel permeation and ion-exchange chromatography, indicating reduction and sequestration by metallothionein in vivo. The identity of a third anionic low molecular weight Tc-binding component was not established. No evidence was found for binding of Tc to haemocyanin, ferritin or transferrin. Particulate Tc [probably TcO(OH)2] was bound to plasma membranes and was also present in lysosomes, indicating reduction of pertechnetate and pinocytosis in the digestive gland. In contrast,241Am was mainly sequestered by the lysosomal/vacuolar system, indicative of uptake by pinocytosis. Approximately 2 to 3% of the Am was bound to ferritin and 20% was bound to unidentified ligands of 10 and 20 kdaltons mol. wt. There was no evidence for sequestration of Am by metallothionein. These studies prove that waste radionuclides discharged by the nuclear industry are metabolically active and enter the normal metal metabolism and detoxication pathways of a marine shellfish. 相似文献
177.
Forest Restoration on a Closed Landfill: Rapid Addition of New Species by Bird Dispersal 总被引:9,自引:0,他引:9
Urban areas often contain sizeable pockets of degraded land, such as inactive landfills, that could be reclaimed as wildlife habitat and as connecting links to enhance remnant natural areas. In the northeastern U.S., many such lands fail to undergo natural succession to woodland, instead retaining a weedy, herbaceous cover for many years. We hypothesize that seed dispersal is a limiting factor, and that a form of secondary succession could be stimulated by introducing clusters of trees and shrubs to attract avian seed dispersers. As a direct test, we censused a 1.5-ha experimental plantation on the Fresh Kills Landfill (Staten Island, New York) one year after installation, in search of evidence that the plantation was spreading or increasing in diversity. The 17 planted species, many from coastal scrub forests native to this region, were surviving well but contributed almost no seedlings to the area, in part because only 20% of the installed trees or shrubs were reproductive. Of the 1079 woody seedlings found, 95% came from sources outside the plantation; most (71%) were from fleshy-fruited, bird-dispersed plants from nearby woodland fringes. Although the restoration planting itself had not begun to produce seedlings, it did function as a site for attracting dispersers, who enriched the young community with 20 new species. One-fourth of all new recruits were from nine additional wind-dispersed species. Locations with a high ratio of trees to shrubs had proportionately more recruits, indicating that plant size contributed to disperser attraction. The density of new recruits of each species was dependent on distance from the nearest potential seed source. Introducing native species with the capacity to attract avian dispersers may be the key to success of many restoration programs. 相似文献
178.
Summary Play behavior of young ponies accounted for two-thirds of total running exercise and over 95% of all high-speed turns in ten animals from birth to age six weeks. The classical supposition, never previously demonstrated, that most exercise of young mammals occurs in play, is confirmed in these subjects. 相似文献
179.
韩海东 《Ambio-人类环境杂志》2004,(Z1):35-38
山地不仅为全球60多亿人口提供了必需的生境和包括水资源在内的各种资源,而且可以使我们深入地了解全球人类的生境是如何发展的、全球气候发生变化时它又是如何响应的、以及气候突变是如何引起全球生物退化和经济衰退等这样的环境问题.在全世界60多亿人口中,至少有6亿人生活在山区.山区同时又是世界上哺育其他数十亿人口的主要河流的发源地.在河谷流域中,至少有一半人的生活用水部分或者全部依赖于山区的冰雪融水.由于人类活动致使大气组成成分发生变化,引起全球气候不断变暖,从而导致冰川的不断退缩.许多冰川已经或正在消失,这将严重威胁全球城市用水需求.全球温度升高在高纬地区表现得最为明显,从而使得像格陵兰和南极大陆的一些大冰盖变得非常脆弱.北半球冰川的剧烈消融又产生了许多其他的问题:如挪威海湾流的减弱,斯堪的纳维亚半岛和北欧气候的大规模变化等.在生物海洋中,山地是一些生物岛,特有的物种生态型很多.全球气候变暖,使环境的变化已超出了这些山地物种特有生态型的适应范围,致使这些物种特有生态型不能适应环境的改变而对所有类型的病害都很脆弱.这一过程是系统性的衰退,在越来越多暴露于极端气候条件下的山坡上表现得非常明显.现在我们注意到,随着气候变化的累积,植物的死亡率与发病率也不断增加.山区尤其清楚地反映出全球气候突变的严重性.尽管目前的美国政府对一些建设性的建议和措施持强硬立场,但我们还是能够而且必须对此做出应对. 相似文献
180.
Very low maternal serum alpha-fetoprotein (MSAFP) levels (<10 ng/mL) are known to be associated with non-viable pregnancies, including conditions such as fetal death, molar pregnancies, and non-pregnancies. There has not been agreement, however, as to whether very low MSAFP levels indicate already existing fetal deaths or are actually predictive. We analysed 230 pregnancies with MSAFP levels <10 ng/mL from among 15 807 women (1.5 per cent) screened consecutively during a three-year period and identified 26 non-viable pregnancies, 22 of which were diagnosed sonographically as part of the screening process (17 missed abortions, 3 blighted ova, 2 non-pregnancies). Furthermore, 20 of these 22 pregnancies were associated with essentially undetectable MSAFP levels (<5 ng/mL). Our data indicate that pregnancies with MSAFP values <5 ng/mL are the group most strongly associated with fetal non-viability and that very low MSAFP values are not strongly predictive for fetal death. 相似文献