Herbivores enable plant survival under nutrient limited conditions in a model grazing system

We make a theoretical study of nitrogen cycling in a model of a grazing system with five compartments. The rates of uptake of nutrient by plants and herbivores are allowed nonlinear forms which involve no a priori assumptions about whether the system is subject to top-down or bottom-up control. We derive a method of piecewise linear approximation which allows analytical study of the system. We then use this method to investigate the properties of the equilibrium states of the system, and in particular whether the system favours donor- or recipient-control, the grazing optimization problem, and the potential benefits of herbivory to plant growth. We are able to generalise our results to all uptake functions of the same qualitative class as those considered, and to show that in general the system will tend to a stable equilibrium state of donor-controlled herbivory. In this model, the presence of the ‘right’ class of herbivore is not only beneficial to plant growth in certain circumstances, but can be essential to their survival, allowing plants to co-exist with herbivores under conditions in which they would be unable to survive alone.     

Response of Fish and Macroinvertebrate Bioassessment Indices to Water Chemistry in a Mined Appalachian Watershed

Multimetric indices based on fish and benthic macroinvertebrate assemblages are commonly used to assess the biological integrity of aquatic ecosystems. However, their response to specific stressors is rarely known. We quantified the response of a fish-based index (Mid-Atlantic Highlands Index of Biotic Integrity, MAH-IBI) and a benthic invertebrate-based index (West Virginia Stream Condition Index, WV-SCI) to acid mine drainage (AMD)-related stressors in 46 stream sites within the Cheat River watershed, West Virginia. We also identified specific stressor concentrations at which biological impairment was always or never observed. Water chemistry was extremely variable among tributaries of the Cheat River, and the WV-SCI was highly responsive across a range of AMD stressor levels. Furthermore, impairment to macroinvertebrate communities was observed at relatively low stressor concentrations, especially when compared to state water quality standards. In contrast to the WV-SCI, we found that the MAH-IBI was significantly less responsive to local water quality conditions. Low fish diversity was observed in several streams that possessed relatively good water quality. This pattern was especially pronounced in highly degraded subwatersheds, suggesting that regional conditions may have a strong influence on fish assemblages in this system. Our results indicate that biomonitoring programs in mined watersheds should include both benthic invertebrates, which are consistent indicators of local conditions, and fishes, which may be indicators of regional conditions. In addition, remediation programs must address the full suite of chemical constituents in AMD and focus on improving linkages among streams within drainage networks to ensure recovery of invertebrate and fish assemblages. Future research should identify the precise chemical conditions necessary to maintain biological integrity in mined Appalachian watersheds.     

Passive and active adaptive management: approaches and an example

Adaptive management is a framework for resource conservation that promotes iterative learning-based decision making. Yet there remains considerable confusion about what adaptive management entails, and how to actually make resource decisions adaptively. A key but somewhat ambiguous distinction in adaptive management is between active and passive forms of adaptive decision making. The objective of this paper is to illustrate some approaches to active and passive adaptive management with a simple example involving the drawdown of water impoundments on a wildlife refuge. The approaches are illustrated for the drawdown example, and contrasted in terms of objectives, costs, and potential learning rates. Some key challenges to the actual practice of AM are discussed, and tradeoffs between implementation costs and long-term benefits are highlighted.     

我国当前城乡建设用地置换的实践探索及问题剖析

当前我国城乡建设用地利用存在着城市建设用地指标紧缺、农村建设用地低效利用和城乡建设用地"双增"大量侵占耕地等问题。城乡建设用地增减挂钩政策推动下的城乡建设用地置换有望成为破解该问题的综合途径。2004年开始,伴随相关政策陆续出台,城乡建设用地置换实践在多个省市试点推进,其中江苏省万顷良田建设工程、天津市宅基地换房、山东省农村社区化、重庆市地票交易市场的实践较为典型。基于上述典型案例和系统要素分析,总结了实践的问题、根源与演进,认为目前系统中的要素与相应的操作环节中存在问题隐患且部分问题表现突出;实践中主要以涉及"非自愿"置换、补偿与保障不足、生产生活方式改变等的农民利益受损问题较为突出;问题的根源集中在三个方面,即国家层面的约束性的法律、法规、政策尚不健全,地方政府操作不合理和缺乏科学研究支撑。今后的实践中,应该建立统一的城乡土地市场并逐步完善政府主导下的城乡土地市场运行机制,建立科学合理的征地补偿机制,深入开展相关科学研究,遵循集约型用地增长模式,同小城镇建设紧密结合,注重保护村落景观风貌。     

HUMAN BEHAVIOR AND RESPONSE TOWARDS STORM HAZARD IN WEST VANCOUVER,BRITISH COLUMBIA1

ABSTRACT: Human behavior and response towards storm hazard are examined in this study. One-hundred and twenty flood victims in West Vancouver, British Columbia, were administered a sentence completion test to ascertain how these victims behaved and responded to the flash flood of July 12, 1972. The sentence completion test consisted of 11 sentence stems. Seven of these dealt with the respondent's behavior toward the storm experience, and four with the issue of internal vs. external locus of control. Completions of the seven sentence stems at three time situations showed that West Vancouverites expressed the normal reactions of fear and anxiety before the storm; showed negative emotions during the storm; and displayed a feeling of mutual cooperation after the storm. Completions of the remaining four sentence stems revealed that West Vancouverites emphasized the importance of internal factors, viz., autonomy, drive and hard work, in controlling their lives. They recognized God as a benevolent - protective and almighty - powerful figure. Forty percent of the respondents did not believe in luck, while 8 percent regarded it as important in their lives. One might conclude that West Vancouverites could cope with natural hazardous threats better than those who rely on external factors in directing their lives.     

Enforcement and price controls in emissions trading

This paper examines how enforcement affects the structure and performance of emissions trading programs with price controls under uncertainty about firms' abatement costs. The analysis highlights how an enforcement strategy can cause abatement-cost risk to be transmitted to enforcement costs via the price of permits. When this occurs, accommodating the effect of abatement-cost risk with an optimal policy results in higher expected emissions and lower expected permit price than their second-best optimal values. However, it is possible to design an enforcement strategy that shields enforcement costs from abatement-cost risk by tying sanctions directly to permit prices. This enforcement strategy stabilizes enforcement effort, the optimal permit supply and price controls are independent of enforcement costs, and the policy produces the second-best optimal outcome.     

Effective application of monitoring information: the case of San Francisco Bay

The San Francisco Estuary Regional Monitoring Program (RMP) for Trace Substances is an innovative partnership among a regulatory agency, more than 70 regulated entities, and an independent scientific organization. The institutional arrangement behind the RMP has made the regulatory system increasingly responsive to emerging management needs, particularly with regard to the development of total maximum daily loads and ecosystem impairment assessment. Through multi-agency partnerships within and outside the RMP institutional structure, major information gaps for several pollutants of concern have been narrowed, resulting in a successful consensus-based regulatory approach to managing copper and nickel mass inputs into the Estuary. Short-term research efforts, based upon monitoring results, helped identify the most cost-effective control and remediation options for various bioaccumulative substances. Additionally, adaptive changes to the monitoring program documented the existence of widespread aquatic toxicity in the Estuary that is apparently due to pesticide runoff from agricultural and urban areas. One of the most important contributions of this collaborative monitoring program is the deliberate and systematic adjustment of management and research questions that serve to influence and add relevance to the overall research agenda related to San Francisco Estuary ecosystem assessment.     

The Airline Lifesaver: a 17-year analysis of a technique to prompt the delivery of a safety message

INTRODUCTION: The Airline Lifesaver (AL) is a 13.3 cm x 9.8 cm card any passenger can deliver to the attendant of a commercial airline in order to prompt the delivery of an important safety message. In particular, the AL requests the following safety--belt reminder be added to the regular announcements given at the end of the flight-"Now that you have worn a seat belt for the safest part of your trip, the flight crew would like to remind you to buckle-up during your ground transportation." METHOD: The AL card was handed to 1,258 flight attendants over a 17-year period and compliance with the request for the safety message was systematically tracked. Slightly more than one-third of the AL cards (n=460) included an incentive for making the announcement. RESULTS: Without the incentive, compliance to give the buckle-up reminder was 35.5% of 798 flights. With the incentive, compliance was significantly higher (i.e., 53.3%). IMPACT: The validity of the AL intervention is discussed with regard to its: (a) relevance to cognitive dissonance and consistency theory, and (b) broad-based applicability as a component of community-wide efforts to facilitate a safety-focused culture. The 17-year study also demonstrated a practical and cost-effective application of a behavior-based incentive program.     

珠三角地区冬季大气中PCBs的空间分布

为了考察珠三角地区冬季大气中PCBs的空间分布,于2001年12月24日至2002年1月16日在广州的市区、郊区和背景区进行连续的空气样品采样.采用GC-MS-SIM模式进行PCBs分析.结果表明,空气中PCBs的总浓度按照距离市区从近到远的次序依次降低.市区PCBs平均浓度是郊区的1.61倍,是背景区的2.54倍.PCBs各单体化合物的浓度分布表现出明显的地区差异.低氯取代PCBs的市区浓度比郊区和背景区的浓度高出很多,而高氯取代PCBs的空间差异不明显.在不同氯数PCB浓度之和对PCBs总浓度的百分贡献率分布中,市区、郊区和背景区都表现为三氯和四氯取代PCBs的贡献最大,而且不同地区两者的贡献率之和非常接近.市区和郊区空气中三氯和四氯取代PCBs的贡献比较接近;而背景区空气中四氯取代PCBs的贡献高达52.79%,是三氯贡献的近2倍.郊区和背景区空气中五氯取代PCBs的平均贡献率分别是9.65%和10.87%.仅就颗粒相而言,其PCBs平均贡献率在市区、郊区和背景区表现出非常好的一致性.对市区、郊区和背景区空气中log Kp与log PLo进行回归分析,其斜率mr分别是-0.60、-0.42和-0.45,都明显地偏离空气中气/固分配的理想平衡状态.