花椒农林复合生态系统的简化对某些相关因子的影响

对单一种植和复合种植两种模式的花椒林地(即有草模式和无草模式)进行了相关生态因子的对比调查,以评价现存花椒林单一模式的合理性．结果表明,在单一种植模式下,花椒林的高度、地径和冠幅虽显著优于复合模式,但是病虫害严重;两种模式中土壤含水率均是随土层厚度的增加而增大,但是变幅有较大差异：复合模式的变幅较稳定,为7．59%～23．79％;而单一模式的变化较剧烈,为4．73％～49．72％,复合模式的土壤含水率显著高于单一模式．复合模式的昆虫种类、多样性、丰富度和均匀度也明显高于单一模式,其中单一模式中的肉食性和寄生性昆虫种类低于复合模式,而植食性蚜虫数量则高于复合模式,暗示单一模式中天敌的栖境和资源以及特定的食草昆虫与有益菌缺少．讨论认为,杂草在花椒林生态系统中起着重要的生态作用,现存的单一种植模式虽然对花椒的生长和产量有利,但却是以牺牲农林系统的可持续发展以及生物多样性为代价的．表3参9。     

Echelon approach to areas of concern in synoptic regional monitoring

Echelons provide an objective approach to prospecting for areas of potential concern in synoptic regional monitoring of a surface variable. Echelons can be regarded informally as stacked hill forms. The strategy is to identify regions of the surface which are elevated relative to surroundings (Relative ELEVATIONS or RELEVATIONS). These are areas which would continue to expand as islands with receding (virtual) floodwaters. Levels where islands would merge are critical elevations which delimit echelons in the vertical dimension. Families of echelons consist of surface sectors constituting separate islands for deeper waters that merge as water level declines. Pits which would hold water are disregarded in such a progression, but a complementary analysis of pits is obtained using the surface as a virtual mould to cast a counter-surface (bathymetric analysis). An echelon tree is a family tree of echelons with peaks as terminals and the lowest level as root. An echelon tree thus provides a dendrogram representation of surface topology which enables graph theoretic analysis and comparison of surface structures. Echelon top view maps show echelon cover sectors on the base plane. An echelon table summarizes characteristics of echelons as instances or cases of hill form surface structure. Determination of echelons requires only ordinal strength for the surface variable, and is thus appropriate for environmental indices as well as measurements. Since echelons are inherent in a surface rather than perceptual, they provide a basis for computer-intelligent understanding of surfaces. Echelons are given for broad-scale mammalian species richness in Pennsylvania.     

Land-based sources of marine pollution: organochlorine pesticides in stream systems

BACKGROUND: Organochlorine pesticides (OCPs) have been dispersed ubiquitously in the environment. Bottom sediments act as sinks for these compounds and their concentrations often reflect the degree of anthropogenic pollution. This study was designed to evaluate the occurrence and distribution of OCPs in superficial streambed sediments and their relation to land use in two creeks that contribute to the coastal pollution of the southeastern region of Argentina. METHODS: Sampling sites were selected by a combination of land use and stream type. Las Brusquitas creek, which passes through vast agricultural areas, and La Tapera creek which originates in a natural wetland and passes through horticultural farming and urban areas. OCPs quantification was carried out by GC-ECD. RESULTS AND DISCUSSION: Results showed similar total OCP concentrations in sediments from both creeks in the range of 6-25 ng/g dry wt. However, when OCPs were expressed in ng/g total organic carbon (TOC), La Tapera creek presented 4-fold higher total levels as a consequence of a higher OCP input during the recent past in that watershed. La Tapera outfall showed 4-fold higher levels than that seen in Las Brusquitas, although both values were below the sediment quality criteria demanded to protect wildlife. Sigmaendosulfans, sigmaDDTs and sigmachlordanes were the main OCP group in all samples, with Endosulfan sulfate being the most frequent and abundant compound. The predominance of metabolites with respect to parent compounds suggests a contamination mainly by runoff from aged and weathered agricultural soils. CONCLUSIONS: Despite OCPs being banned, they still exist in creek sediments from the studied region, representing continuous contributions of land-based source contaminants to the marine environment. OUTLOOK: Future research on OCP levels in suspended sediments is recommended in order to determine the total OCP concentrations in the selected stream systems.     

Linking on-farm dairy management practices to storm-flow fecal coliform loading for California coastal watersheds

How and where to improve water quality within an agricultural watershed requires data at a spatial scale that corresponds with individual management decision units on an agricultural operation. This is particularly true in the context of water quality regulations, such as Total Maximum Daily Loads (TMDLs), that identify agriculture as one source of non-point source pollution through larger tributary watershed scale and above and below water quality investigations. We have conducted a systems approach study of 10 coastal dairies and ranches to document fecal coliform concentration and loading to surface waters at the management decision unit scale. Water quality samples were collected on a storm event basis from loading units that included: manure management systems; gutters; storm drains; pastures; and corrals and lots. In addition, in-stream samples were collected above and below the dairy facilities and from a control watershed, managed for light grazing and without a dairy facility or human residence and corresponding septic system. Samples were analyzed for fecal coliform concentration by membrane filtration. Instantaneous discharge was measured for each collected sample. Storm runoff was also calculated using the curve number method (SCS, 1985). Results for a representative dairy as well as the entire 10 dairy data set are presented. Fecal coliform concentrations demonstrate high variability both within and between loading units. Fecal coliform concentrations for pastures range from 206 to 2,288,888 cfu/100 ml and for lots from 1,933 to 166,105,000 cfu/100 ml. Mean concentrations for pastures and lots are 121,298 (SE=62,222) and 3,155,584 (SE=1,902,713) cfu/100 ml, respectively. Fecal coliform load from units of concentrated animals and manure are significantly more than units such as pastures while storm flow amounts were significantly less. Compared with results from earlier tributary scale studies in the watershed, this systems approach has generatedwater quality data that is beneficial for management decisions because of its scale and representation of current management activities. These results are facilitating on-farm changes through the cooperative efforts of dairy managers, regulatory agency staff, and sources of technical and financial assistance.     

Long-range transport potential of semivolatile organic chemicals in coupled air-water systems

Ongoing deliberations on the regulation of semivolatile organic chemicals require the assessment of chemical transport in atmospheric and marine systems. The characteristic travel distance was proposed as a measure for the transport potential in air and water. However, the existing definition treats the transport processes separately. It is shown that combined transport in coupled air-ocean systems can accelerate the overall transport into remote regions. Concentration ratios in air and water change with distance from sources depending on the initial concentration ratio and on the difference between the transport velocities. A measure is suggested facilitating the chemical screening with respect to transport potentials in such air-ocean systems. A case study for alpha and gamma-hexachlorocyclohexane shows that the suggested measure qualitatively reveals the transport potentials of these chemicals and exemplifies possible concentration patterns.     

INTERPRETATION OF THE DUAL PROGRAM FOR OPTIMAL GROUNDWATER HYDRAULIC CONTROL1

ABSTRACT: Optimization formulations for hydraulic control that take the form of linear programs possess a corresponding dual linear program. The economic and physical interpretations of the dual linear program are examined for formulations in which hydraulic head in groundwater systems is constiained. In each case it is shown that the dual linear program has a physically meaningful interpretation. For a hydraulic gradient control formulation used for remedial analysis it is shown that the dual variable can be interpreted as the remedial benefit due to each gradient control constraint. The dual linear program maximizes the remedial benefit. The value of the dual variable can be used to compute such useful properties as the total remedial benefit of pumping at a specific location. For a formulation that optimizes aquifer yield while constraining drawdown the dual variable can be used to measure the total cost of drawdown capacity consumption per unit of pumping at a specific location. The dual program minimizes the cost of drawdown capacity consumption. By examining the meaning of the dual linear program an alternate statement of the problem under study is revealed. Quantities arising from the dual program add to the value of the optimization approach. Significant new information can be derived from existing linear optimization formulations with minimal additional computational effort.     

国际船舶油污损害赔偿机制评述

介绍和分析了国际船舶油污损害赔偿机制的运转概况，特别注重论述了其主要经验和特点，以供参考。     

IMPACT OF VARIED DATA RESOLUTION ON HYDRAULIC MODELING AND FLOODPLAIN DELINEATION1

ABSTRACT: Current data collection technologies such as light detection and ranging (LIDAR) produce dense digital terrain data that result in more accurate digital terrain models (DTMs) for engineering applications. However, such data are redundant and often cumbersome for hydrologic and hydraulic modeling purposes. Data filtering provides a means of eliminating redundant points and facilitates model preparation. This paper demonstrates the impact of varied data resolution on a case study completed for a 2.3 mi² area with mild slopes (about 001 ft/ft) along Leith Creek near Laurinburg, North Carolina. For the original data set and seven filtered data sets, filtering induced changes in elevation, area, and hydraulic radius were determined for 10 water depths at 23 cross sections. Water surface elevations resulting from HEC‐RAS (Hydrologic Engineering Center‐River Analysis System) models for each data set were then compared. A hydraulic model sensitivity analysis was also conducted to compare filtering error to error introduced by variation in flow rates and roughness values. Finally, automated floodplain delineation was performed for each filter level based on the computed hydraulic model results and the filtered LIDAR elevations. Data filtering results indicate that significant time savings are achieved throughout the modeling process and that filtering to four degrees can be performed without compromising cross‐sectional geometry, hydraulic model results, or floodplain delineation results.     

A FRAMEWORK FOR QUANTITATIVE SMART GROWTH IN LAND DEVELOPMENT1

ABSTRACT: Increasing awareness about the problems brought on by urban sprawl has led to proactive measures to guide future development. Such efforts have largely been grouped under the term “Smart Growth.” Although not widely recognized as such, the “smart” in Smart Growth implies an optimization of some quantity or objective while undertaking new forms of urban development. In this study, we define Smart Growth as that development plan that leads to the optimal value of a precisely defined measure identified by a stakeholder or stakeholders. To illustrate a formal, quantitative framework for Smart Growth, this study develops definitions of optimal development from the perspectives of four different types of stakeholders: a government planner, a land developer, a hydrologist, and a conservationist subject to certain development constraints. Four different objective functions are posed that are consistent with each of these stakeholders’perspectives. We illustrate the differences in consequences on future development given these different objective functions in a stylized representation for Montgomery County, Maryland. Solutions to Smart Growth from the individual perspectives vary considerably. Tradeoff tables are presented that illustrate the consequences experienced by each stakeholder depending on the viewpoint that has been optimized. Although couched in the context of an illustrative example, this study emphasizes the need to apply rigorous, quantitative tools in a meaningful framework to address Smart Growth. The result is a tool that a range of parties can use to plan future development in ways that are environmentally and fiscally responsible and economically viable.     

Disaster preparedness in a complex urban system: the case of Kathmandu Valley,Nepal

The city is a growing centre of humanitarian concern. Yet, aid agencies, governments and donors are only beginning to comprehend the scale and, importantly, the complexity of the humanitarian challenge in urban areas. Using the case study of the Kathmandu Valley, Nepal, this paper examines the analytical utility of recent research on complex urban systems in strengthening scholarly understanding of urban disaster risk management, and outlines its operational relevance to disaster preparedness. Drawing on a literature review and 26 interviews with actors from across the Government of Nepal, the International Red Cross and Red Crescent Movement, non‐governmental organisations, United Nations agencies, and at‐risk communities, the study argues that complexity can be seen as a defining feature of urban systems and the risks that confront them. To manage risk in these systems effectively, preparedness efforts must be based on adaptive and agile approaches, incorporating the use of network analysis, partnerships, and new technologies.