Fishes, their biology and fisheries management in Lake Peipsi

The management of aquatic weeds in an irrigation scheme is constrained by the agro-economic system in relation to scheme layout, the nature and ecology of the aquatic weeds, agricultural practice, irrigation and drainage requirements, and the available resources for maintenance. The way in which the ecology, engineering and economics of irrigation and drainage channels interact to produce a pattern of management is investigated for the Mwea Irrigation Settlement Scheme, Central Province, Kenya. This is used to develop a simple model which enables the economic implications of varying the aquatic weed management practice to be identified. The model brings the selection of a weed control programme within the principles of engineering economy.     

Trait coordination and environmental filters shape functional trait distributions of forest understory herbs

1. Understanding the drivers of trait selection is critical for resolving community assembly processes. Here, we test the importance of environmental filtering and trait covariance for structuring the functional traits of understory herbaceous communities distributed along a natural environmental resource gradient that varied in soil moisture, temperature, and nitrogen availability, produced by different topographic positions in the southern Appalachian Mountains.
2. To uncover potential differences in community‐level trait responses to the resource gradient, we quantified the averages and variances of both abundance‐weighted and unweighted values for six functional traits (vegetative height, leaf area, specific leaf area, leaf dry matter content, leaf nitrogen, and leaf δ¹³C) using 15 individuals of each of the 108 species of understory herbs found at two sites in the southern Appalachians of western North Carolina, USA.
3. Environmental variables were better predictors of weighted than unweighted community‐level average trait values for all but height and leaf N, indicating strong environmental filtering of plant abundance. Community‐level variance patterns also showed increased convergence of abundance‐weighted traits as resource limitation became more severe.
4. Functional trait covariance patterns based on weighted averages were uniform across the gradient, whereas coordination based on unweighted averages was inconsistent and varied with environmental context. In line with these results, structural equation modeling revealed that unweighted community‐average traits responded directly to local environmental variation, whereas weighted community‐average traits responded indirectly to local environmental variation through trait coordination.
5. Our finding that trait coordination is more important for explaining the distribution of weighted than unweighted average trait values along the gradient indicates that environmental filtering acts on multiple traits simultaneously, with abundant species possessing more favorable combinations of traits for maximizing fitness in a given environment.

     

Costs and benefits of cervical screening. III. Cost/benefit analysis of a call of previously unscreened women

A population‐based cervical screening programme issued invitations to women with no record of a previous smear. This call was very good value, at £5780 per life saved or £159 per life‐year saved at 1991 prices. The first priority for the cervical screening service should be comprehensive coverage.     

Tree hydraulic traits are coordinated and strongly linked to climate‐of‐origin across a rainfall gradient

Plant hydraulic traits capture the impacts of drought stress on plant function, yet vegetation models lack sufficient information regarding trait coordination and variation with climate‐of‐origin across species. Here, we investigated key hydraulic and carbon economy traits of 12 woody species in Australia from a broad climatic gradient, with the aim of identifying the coordination among these traits and the role of climate in shaping cross‐species trait variation. The influence of environmental variation was minimized by a common garden approach, allowing us to factor out the influence of environment on phenotypic variation across species. We found that hydraulic traits (leaf turgor loss point, stomatal sensitivity to drought [P_gs], xylem vulnerability to cavitation [P_x], and branch capacitance [C_branch]) were highly coordinated across species and strongly related to rainfall and aridity in the species native distributional range. In addition, trade‐offs between drought tolerance and plant growth rate were observed across species. Collectively, these results provide critical insight into the coordination among hydraulic traits in modulating drought adaptation and will significantly advance our ability to predict drought vulnerability in these dominant trees species.     

The Value of Forests to World Food Security

We assembled information on the contribution and value of forests to world food security. An assessment was made of the role of forests and non-timber products in the food system of developing countries. We estimated that upwards of 300 million people annually earn part or all of their livelihood and food from forests. A total of about $90 billion in non-timber products are harvested each year. Forests also help to protect land, water, and biological resources, and they play an important role in maintaining the productivity of agricultural and environmental systems.     

End-of-Life Infrastructure Economics for "Clean Vehicles" in the United States

Rising fuel prices and concern over emissions are prompting automakers and legislators to introduce and evaluate "clean vehicles" throughout the United States. Hybrid electric vehicles (HEVs) are now on the roads, electric vehicles (EVs) have been test marketed, and niche vehicles such as high-fuel-economy microcars are being considered for introduction. As these vehicles proliferate and mature, they will eventually reach their end of life (EOL). In the United States, an extensive recycling infrastructure exists for conventional, internal combustion engine (ICE) vehicles. Its primary constituents are the disassembler and the shredder. These industries, as well as battery recyclers, are expected to play integral roles in the EOL processing of clean vehicles.
A model of the automobile-recycling infrastructure and goal programming techniques are used to assess the materials streams and process profitabilities for several different clean vehicles. Two-seat EVs with lead-acid or NiMH batteries are compared with two- and four-seat HEVs and microcars. Changes to the nonferrous content in the vehicle bodies are explored and compared for the effect on processing profit-ability. Despite limitations associated with the linearity of goal programming techniques, application of this tool can still provide informative first-order results. Results indicate that although these clean vehicles may not garner the same profit levels as conventional ICE vehicles, they are profitable to process if there are markets for parts and if there are sufficient quantities of nonferrous materials.     

Impact of Firm-Based Environmental Standards on Subsidiaries and Their Suppliers: Evidence from Motorola-Penang

How successful are multinational corporations in extending their firm-based environmental standards to their subsidiaries and those subsidiaries' local suppliers in their global production networks in developing countries? We address this question through an in-depth case study of how Motorola, a prominent multinational electronics firm with an extensive global production network, is using a set of firm-based standards to meet several new stringent European Union environmental directives. The case study demonstrates that these firm-based standards appear to be enabling a major subsidiary and its suppliers in one developing economy to reduce the environmental intensities of their production activities. This finding suggests that the firm-based environmental standards of multinationals with extensive global production networks might contribute to a leveling up of environmental standards in subsidiaries and their local suppliers, rather than a "race to the bottom", thus reinforcing the technique or intensity effects associated with open trade, investment, and technology policies.     

北京植物园不同功能型植物叶经济谱

通过对北京植物园不同功能型植物的叶片光合参数、叶绿素荧光参数、叶面积、叶干质量以及叶氮含量等性状参数进行测定,分析了不同功能型植物的叶经济谱.结果表明: 生活型中草本植物、生活史中一年生植物、光合型中C4植物靠近叶经济谱中快速投资-收益型物种的一端,而生活型中乔木和灌木、生活史中多年生植物、光合型中C3植物位于缓慢投资-收益型物种的一端,表明不同功能型植物通过叶片性状间的权衡采取不同的环境适应策略,验证了不同功能型植物叶经济谱的存在.不同功能型植物叶片性状具有明显差异,其中不同生活型间的叶片比叶面积(SLA)、叶氮含量(N_mass)、最大净光合速率(A_mass)、光合氮利用效率(PNUE)均表现出草本植物>藤本植物>灌木>乔木;不同生活史间一年生植物的SLA、N_mass、A_mass、PNUE均显著高于多年生植物;不同光合型间植物的A_mass、PNUE、PSⅡ实际光化学效率(Φ_PSⅡ)均表现出C4>C3.N_mass、A_mass、SLA两两之间呈显著正相关,而PSⅡ有效光化学量子产量(F_v′/F_m′)与SLA呈显著负相关;PNUE与SLA呈显著正相关.