Double Allee Effects and Extinction in the Island Fox

Abstract:  An Allee effect (AE) occurs in populations when individuals suffer a decrease in fitness at low densities. If a fitness component is reduced (component AE), per capita population growth rates may decline as a consequence (demographic AE) and extinction risk is increased. The island fox ( Urocyon littoralis ) is endemic to six of the eight California Channel Islands. Population crashes have coincided with an increase in predation by Golden Eagles ( Aquila chrysaetos ). We propose that AEs could render fox populations more sensitive and may be a likely explanation for their sharp decline. We analyzed demographic data collected between 1988 and 2000 to test whether fox density (1) influences survival and reproductive rates; (2) interacts with eagle presence and affects fox fitness parameters; and (3) influences per capita fox population trends. A double component AE simultaneously influenced survival (of adults and pups) and proportion of breeding adult females. The adult survival AE was driven by predation by eagles. These component AEs led to a demographic AE. Multiple-component AEs, a predation-driven AE, and the simultaneous occurrence of both component and demographic AEs in a mammal are all previously unreported processes. Populations below 7 foxes/km² could have suboptimal population growth rates due to the demographic AE, and AEs may have contributed to the dramatic declines in three fox populations. Because fox densities in critically endangered populations are well below this level, removing Golden Eagles appears necessary to prevent a predation-driven AE. Conservationists should also be aware of AEs when planning the release of captive foxes. More generally, our findings highlight the danger of overlooking AEs in the conservation of populations of rare or threatened species.     

富营养化水体底泥释磷的影响因素及其机理

磷是湖泊富营养化的主要限制因子，在此综述了沉积物中磷的赋存形态，释放机理及其影响因素。内源磷的赋存形态主要分为铝磷、铁磷、钙磷及有机磷，磷释放受pH值、溶解氧、生物、温度、扰动等5种因素影响，对富营养水体内源磷释放的影响因素及其机理进行研究，可为富营养化水体的治理提供理论依据。     

重庆地铁岩石隧道环境振动衰减规律

本文研究了重庆地铁岩石隧道环境振动衰减规律，并预测了重庆地铁振动的影响范围和程度。     

三峡库区堆存垃圾浸出污染物的水质影响模拟

以三峡库区坝前水位135～175m范围的生活垃圾为研究对象,调查分析了其堆存量、空间分布和理化特性;通过污染物溶出动态模拟和放大实验研究,估算了生活垃圾中有机污染物的溶出源强,并运用河流岸边稳态衰减模式计算了不同处置方案对库区水质的影响程度.针对基准方案和135m蓄水期处置方案,分别对库区局部河段水质和干流水质的影响进行了分析比较.结果表明,若采用基准方案,即将淹没区内约600×104t的生活垃圾就地处置,淹没于水中,将会对库区水质安全构成较大的威胁;若采用135m蓄水期处置方案,则水体中CODcr值增加不超过0.03mg·L-1,对库区干流水质的影响较小.     

Double dividend hypothesis, golden rule and welfare distribution

This paper analyzes the double dividend issues within the framework of overlapping generations models. We characterize the necessary conditions for obtaining a double dividend, i.e. an improvement of environmental and non-environmental welfare when the revenue from the pollution tax is recycled into a change in the labor tax rate. We show that, depending on the initial capital stock and on the intertemporal elasticity of substitution, conditions may be defined to simultaneously allow (i) the obtaining of a long-term double dividend, (ii) the economy to move closer to the modified golden rule and (iii) in the short term, an improvement in the welfare of the two present generations.     

三峡库区沿江堆存垃圾浸泡污染物COD溶出规律研究

三峡库区沿江两岸堆存了大量的生活垃圾，随着三峡工程二期蓄水的I临近，二期水位以下的垃圾必须得到清理。为了科学有效的治理库区的生活垃圾，达到环境效益，社会效益和经济效益三者的最优结合，本文通过浸泡生活垃圾污染负荷浸出理论分析和动态冲刷实验研究，建立了理论模型和实验模型，并且对二者进行了对比分析。结果表明实验和理论模型能较好的反映垃圾污染物的溶出规律，将为三峡库区库底生活垃圾对水环境的影响预测和其清理提供基础和决策依据。     

依法做好地震应急是减轻地震灾害的关键环节

本文结合当前地震形势及地震灾害的突发性、社会性、广泛性，对《破坏性地震应急条例》作了阐述，进而论证了依法搞好地震应急总工作是减轻地震灾害的重要环节。     

MONITORING OPERATIONS PERFORMANCE IN LARGE-SCALE PUBLIC IRRIGATION SYSTEMS IN INDONESIA1

ABSTRACT: Different allocation and delivery performance ratios are used to assess operations performance in a large scale public irrigation system in Indonesia. Results from this analysis indicate that field management practices deviate substantially from the official operating procedures. The lack of application of a single, standardized procedure for planning water allocations represents a serious constraint to effective monitoring and evaluating system performance. Underestimated and unrealistic planned allocations becomes the justification for overdiversion of water, and has the effect of undermining the resolve of managers to see to it that actual flows meet planned flows. Miscalculating planned allocations, poor matches between planned flows and actual deliveries, overdiversion and misreporting have economic consequences as well. For example, strict adherence to the standard operating rule during the second dry season of 1987 would have resulted in 19,070,000 m³ less water diverted into the irrigation system from the Brantas River or, at a conservative estimate of $1.78 per 100 m³ water, a savings of $339,500. Scope exists for making improvements in management by closer adherence to the standard delivery rule, which will also facilitate proper monitoring and evaluation.     

安岳 县城大气二氧化硫污染特征的研究

本文揭示了安岳县城大气二氧化硫污染特征及其变化规律。针对大气环境质量存在的问题,从宏观上提出了防治大气污染的对策。     

行为形成因子与人为差错模式的定性关联分析

为揭示人为差错的发生规律以便有效管理人为差错,研究行为形成因子与人为差错模式间的对应关系。将行为形成因子作为情景环境的表征,在SRK(skill,rule,knowledge)模型的基础上,将认知功能的效能分为3种指标:全面性、准确性和效率,将认知功能与效能指标相结合得到人为差错模式的分类。在此基础上,根据经验详细分析行为形成因子对认知功能3种效能指标的影响,得到行为形成因子与人为差错模式的关联关系表格。该关联关系是定性的,包含密切关联、重要关联、一般关联和没有关联4种关联程度,不但可以用于人为差错事件的调查,而且可以用于人为差错模式的预测。