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561.
562.
563.
José M. Aparicio 《Behavioral ecology and sociobiology》1997,41(2):129-137
Lesser kestrels (Falco naumanni) lay clutches which appear excessive as only 3% of them yield as many young as eggs laid. Four hypotheses may explain the
adaptive value of producing surplus eggs: (1) the bet-hedging hypothesis assumes that the environment varies unpredictably
and surplus eggs serve to track uncertain resources; (2) the ice-box hypothesis suggests that surplus offspring serve as a
reserve food during a period of shortage; (3) the progeny choice hypothesis says that parents produce surplus offspring in
order to choose these with higher fitness; and (4) the insurance-egg hypothesis proposes that extra eggs are an insurance
against the failure of any egg. To test the significance of this strategy in the lesser kestrel, an experiment manipu-lating
brood size at hatching was carried out over 2 years, with good and bad feeding conditions. The experiment consisted of adding
a chick to experimental broods where one egg failed to hatch or removing a randomly selected chick from experimental broods
where all eggs had hatched. Independently of annual food availability, pairs with brood sizes reduced by one chick fledged
more nestlings than pairs with brood size equalling their clutch sizes. Body condition of young was also better in the former
group, but only in 1993 (a high-food year). Independently of year, mean local survival of parents with complete broods at
hatching was lower than for parents raising reduced broods. These results supported only the insurance-egg hypothesis which
says that surplus eggs may be an insurance against the failure of any egg, but parents may suffer reproductive costs when
all eggs hatch.
Received: 17 January 1997 / Accepted after revision: 27 April 1997 相似文献
564.
Food supply and hatching asynchrony were manipulated for 90 broods of American kestrels (Falco sparverius) during 1989–1991. We measured the growth and mortality of nestlings within four treatment groups (asynchronous, synchronous, food-supplemented, unsupplemented) to test the brood reduction hypothesis of Lack (1947, 1954). Fledging success did not differ between synchronous and asynchronous broods when food was poor but consistent with the brood reduction hypothesis, nestlings died at a younger age in asynchronous broods. When food was supplemented, mortality did not occur in the synchronous broods but youngest nestlings still died in asynchronous nests despite apparently adequate food for the brood. Oldest nestlings in asynchronous broods fledged with a greater mass than their younger siblings, also consistent with Lack's hypothesis. Average nestling quality in synchronous broods was very dependent on food levels. Synchronous young that were supplemented were, on average, the heaviest of any treatment group but young from unsupplemented synchronous broods were the lightest. Overall, patterns of mortality and growth for kestrels support the brood reduction hypothesis when food is limited, but not when it is abundant. This food-dependent benefit of asynchrony in the nestling period is a prerequisite for facultatively adjusted hatching spans during laying. 相似文献
565.
Yu Gang Zhang Qing Huang Jun Cai Zhenxiao Sui Qian 《Frontiers of Environmental Science & Engineering in China》2007,1(1):13-17
As a party of the Stockholm Convention on Persistent Organic Pollutants, China must submit its national implementation plan
(NIP) for this convention. The strategy and action plan for reducing the release of dioxins in China are the most important
components of the NIP. Three problems are key points for developing such strategy and action plan—what are the key sources
for applying the best available technology/best environmental practice (BAT/BEP) to reduce the release of dioxins? How about
the capacity for reducing the dioxins release from the key sources? Where are the areas of priority for applying BAT/BEP?
This paper shows the efforts towards the solution of these problems. The list of key sources covering about half of the total
dioxins release was determined considering four criteria. The capacity of key sources were estimated based on the difference
between the emission factor corresponding to the actual situation in 2004 and that corresponding to the scenario that all
key sources have been applied BAT/BEP to reduce the dioxins release. The priority analysis using the geographical information
system (GIS) tool has revealed that castern provinces should be of high priority in the future reduction activities of dioxins
release in China. 相似文献
566.
活性炭选择性催化还原(SCR)烟道气中NO_X 总被引:22,自引:2,他引:22
研 究了几 种已商业 化的 沥青 基活 性 炭纤 维经 硫 酸进 一 步活 化处 理 后, 对烟 道 气 中 N O X 进行选择 性催化还 原。结果 表明,当 气体中氧 含量 约低 于10 % 时,硫 酸 活化 处理 可 提高 沥青 基 活性炭纤维 对 N O X 选择性催 化还原的 活性。在 本实验 条件 下,获 得 较高 的 N O X 还 原 率的 重要 条 件是气体中 氧含量 大于10 % 和较 低的温度 ;将气体 中 N O 预氧化为 N O2 可 显著提高 N O X 的还 原率;气体中水 分的存 在降低活 性炭纤维 的活性 相似文献
567.
568.
生物相分离系统的污泥减量效能 总被引:1,自引:0,他引:1
为了寻找有效的污泥减量途径,采用生物相分离系统将细菌、原生动物、后生动物及其它大型微型动物相对分离,使有机物在系统的前端被降解,而在后端则主要由原生动物和后生动物完成污泥减量化.试验结果表明,当有机负荷为4.8 kg·m-3·d-1时,生物相分离系统的污泥产率为0.1 kg·kg-1(以COD计),减量比例为80%左右.同时,系统对COD去除率超过了90%,且出水水质满足污水综合排放标准GB8978-2002的一级标准要求. 相似文献
569.
570.
Tuhkanen Sami Lehtilä Antti Savolainen Ilkka 《Mitigation and Adaptation Strategies for Global Change》1999,4(2):91-112
The reduction of carbon dioxide (CO2) emissions may be quite expensive and it is necessary to consider reduction measures for other anthropogenic greenhouse gases, such as methane (CH4) and nitrous oxide (N2O) as well. Their contribution to the total GHG emission from Finland is about 15–20%. In Finland most of the CH4 emissions are due to waste management, agriculture and burning processes. N2O emissions originate from burning processes, agriculture, industry and atmospheric deposition of nitrogen. The cost-effective reduction of the Finnish GHG emissions has been studied with the EFOM-ENV model, which is a quasi-dynamic linear energy system optimisation model. The target function to be minimised is the total discounted cost for the modelled system. In this study the model has been expanded to cover all well-known anthropogenic CO2, CH4 and N2O sources and reduction measures. The results indicate it is economic to reduce the emissions of CO2, CH4 and N2O in Finland. It is profitable to exploit the economic reduction potential of CH4 and N2O, because then the abatement of CO2 emissions does not need to be as extensive as when the reduction is aimed only at CO2 emissions. The inclusion of CH4 and N2O decreases the annual reduction costs about 20% in the year 2010. 相似文献