美国濒危物种保护制度及其对我国的启示

美国的濒危物种保护法律制度是极有特色和卓有成效的，其主要内容包括：立法目的和政策、法律实施机构、列名单制度、危险制度、夺取违法制度、栖息地保护方案制度和公民诉讼制度等。而重视对栖息地的保护、政府机构对濒危物种保护负有法定义务以及重视公众参与和司法实施则是对我国物种保护法制建设的重要启示。     

Scale-Dependent Influence of Topography-Based Hydrologic Features on Patterns of Woody Plant Encroachment in Savanna Landscapes

Rainfall in drylands is erratic. Topographic features of landscapes can dampen or amplify temporal variability by spatially influencing patterns of water loss and accumulation. The extent to which portions of a landscape may differentially capture or retain scarce water and nutrient resources is an important determinant of vegetation patterns, particularly with respect to the distribution of woody plants. We therefore hypothesized that historic changes in woody cover on landscapes experiencing similar climate and disturbance regimes would vary with catena-to-catena (hillslope-to-hillslope) variation in topography-based hydrologic features. We tested this hypothesis by comparing topographic wetness index (TWI) values on replicate landscapes where woody plant abundance has increased over the past 100 yr. These landscapes are characterized by savanna parklands on coarse-textured upland portions of catenas that grade (1–3% slopes) into closed-canopy woodlands on fine-textured (lowland) portions of catenas. TWI values for woody and herbaceous communities were comparable within uplands, suggesting factors unrelated to surface/subsurface hydrology determine patterns of woody cover in these catena locations. TWI values for upland savanna parklands were significantly lower than those of closed-canopy woodlands occupying catena footslopes. Furthermore, uplands adjoining historically static woodland boundaries had lower TWI values than those where woodland boundaries had moved upslope 2.1 m yr⁻¹ from 1976 to 1995. Results suggest runoff–runon relationships influence patterns of woody plant cover and change at the catena scale and may override constraints imposed by soil texture. As a result, changes in woody cover potentially accompanying changes in disturbance regimes, climate or atmospheric chemistry are likely to be constrained by topoedaphic settings. Models of vegetation dynamics may therefore need to explicitly account for rainfall–topography–soil texture relationships and associated scale-dependent mechanisms to accurately predict rates and patterns of change in woody and herbaceous plant abundance.     

Movements of cactus bugs: Patch transfers,matrix resistance,and edge permeability

Individual movement is a key process affecting the distribution of animals in heterogeneous landscapes. For specialist species in patchy habitat, a central issue is how dispersal distances are related to landscape structure. We compared dispersal distances for cactus bugs (Chelinidea vittiger) on two naturally fragmented landscapes (≤ 4% suitable habitat) with different matrix structures (i.e., vegetation height of nonsuitable habitat between suitable patches). Using mark-release-recapture studies, we determined that most transfers between cactus patches occurred during the mating season. Dispersal distances were reduced by > 50% on the landscape that had reduced structural connectivity due to relatively high matrix structure and low patch density. An experiment with detailed movement pathways demonstrated that greater matrix structure decreased mean step lengths, reduced directionality, and thus decreased net displacement by > 60%. However, habitat edges between two matrix elements that differed substantially in resistance to movement were completely permeable. Therefore, the difference in distributions of dispersal distances between the two landscapes mainly reflected the average resistance of matrix habitat and not the level of matrix heterogeneity per se. Our study highlights the merits of combining estimates of dispersal distances with insights on mechanisms from detailed movement pathways, and emphasizes the difficulty of treating dispersal distances of species as fixed traits independent of landscape structure.     

Simulated rainfall evaluation of revegetation/mulch erosion control in the Lake Tahoe basin—3: soil treatment effects

Revegetation, or other erosion control treatments of disturbed soil slopes in forested areas and along highways of the Lake Tahoe basin are directed at reduction of sediment loading to waterways reaching the lake. However, following treatment, little vegetation monitoring, or hydrologic evaluation has been conducted either to determine if the various treatments are successful or to assess the duration of erosion control anticipated in the field. Here, we build upon results from use of the portable rainfall simulator (RS) described in the first two papers of this series to evaluate cover and revegetation treatment effects on runoff rates and sediment concentrations and yields from disturbed granitic and volcanic soils in the basin. The effects of slope on rainfall runoff, infiltration and erosion rates were determined at several revegetated road cut and ski run sites. Rainfall simulation (∼60 mm h⁻¹, approximating a 100‐year, 15‐minute storm) had a mean drop size of ∼2·1 mm and approximately 70 per cent of ‘natural’ rainfall kinetic energy. Measurements of: time to runoff; infiltration; runoff amount; sediment yield; and average sediment concentration were obtained. Runoff sediment concentrations and yields from sparsely covered volcanic and bare granitic soils can be correlated to slope. Sediment concentrations and yields from nearly bare volcanic soils exceeded those from granitic soils by an order of magnitude across slopes ranging from 30–70 per cent. Revegetation, or application of pine‐needle mulch covers to both soil types dramatically decreased sediment concentrations and yields. Incorporation of woodchips or soil rehabilitation that includes tillage, use of amendments (biosol, compost) and mulch covers together with plant seeding resulted in little or no runoff or sediment yield from both soils. Repeated measurements of sediment concentrations and yields in the subsequent two years following woodchip or soil rehabilitation treatments continued to result in little or no runoff. Revegetation treatments involving only use of grasses to cover the soils were largely ineffective due to sparse sustainable coverage (< 35 per cent) and inadequate infiltration rates. Copyright © 2005 John Wiley & Sons, Ltd.     

周氏啮小蜂防治桑园内美国白蛾技术研究

释放周氏啮小蜂对桑园内美国白蛾进行防治试验。一是放蜂数量与防治效果对比试验,结果表明,每667m2地投放3万头小蜂,美国白蛾的寄生率最优达到68%。二是周氏啮小蜂扩散距离所需时间,在越冬代美国白蛾老熟幼虫期和化蛹初期释放周氏啮小蜂,周氏啮小蜂扩散到50m、100m、150m、200m所需的时间分别为20天、25天、30天、35天。在第一代美国白蛾老熟幼虫期和化蛹初期释放周氏啮小蜂,花角蚜小蜂扩散到100m只需要20天,三是是周氏啮小蜂扩散距离与寄生率的关系,结果表明,离放蜂点越近处,周氏啮小蜂的寄生率越高,反之则越低。     

中美林业发展与林业高等教育联动关系比较与启示

世界各国林业发展与林业高等教育各具特色,两者互为联动。文中在分析中美两国相关林业数据和报告的基础上,比较了两国在不同发展阶段林业行业发展与林业高等教育的相互关系,以及两国林业高等教育尤其是林科专业本科阶段的发展状况;分析其规模变化的影响因素。分析认为,中美两国林业发展都经历了从产业型到公益型的发展阶段,而同期的林业高等教育发展阶段也呈现出相适应的变化,林业高等教育发展与同期的林业发展呈现出正相关关系。文中最后提出要以生态文明建设为导向,注重林业和林业高等教育的联动关系,使其相互促进和共同发展,为我国林业发展提供可靠保障。     

美国柑桔业“三高一体化”给我们的启示——中国实现21世纪高效柑桔业的努力方向

通过柑桔联合体形式，实现柑桔生产的“三高一体化”，是美国柑桔业成功的重要因素之一．介绍美国目前柑桔联合公司的构成、产业化和一体化带来的积极有利方面，以及值得借鉴的成功经验，并就如何实现中国柑桔产业化和一体化问题进行了探讨．     

Sediment remediation: U.S. focus on capping and monitored natural recovery

The Battelle Conferences series represent the state-of-the-art of emerging technologies, science and management issues for contaminated sediment remediation. In the 2007 Conference held in Savannah, GA, two in situ technologies for cleanup sites were at the centre of interest: Sediment capping, a form of in situ containment, which involves the placement of a subaqueous covering of clean sediment and/or other materials to isolate contaminated sediments, and monitored natural recovery (MNR), where natural processes are used to mitigate the transfer of particle-bound contaminants into the water phase and/or biota. A third priority technology in the Superfund program, recommended by the U.S. Environmental Protection Agency (EPA), is environmental dredging, i.e., removing the sediments from the aquatic environment. About 30 platform or poster presentations dealt with in situ capping as a technology, reflecting the rapid developments in this field, both in assessments and enhancements of ‘classic’ passive caps and the development and demonstration of active capping technologies. Issues relevant to monitored natural recovery were spread throughout many sessions; e.g., contaminant source identification, control, remediation strategies; innovative characterization and assessment, chemical/toxicological/biological measurements and characterization, bioavailability of contaminants, contaminant fate and transport and remediation effectiveness: defining, monitoring, and demonstrating success. Presentations addressing the role of science and stakeholder input were complemented by discussions on the importance of data quality considerations, uncertainty analysis, and careful selection of reference sites highlighted the complex nature of these multidisciplinary assessments. Case studies, in which site-specific information was linked to regional management objectives, various approaches to watershed-scale assessment and management, and the role of ecosystem considerations, were all discussed in these sessions, as well as in a complementary panel discussion. One compelling feature of the Savannah Conference 2007 (relative to the first couple of meetings) is that there were a much larger number of presentations that provided the tools, models, case studies, etc to fill in the lines of evidence that allow a fair comparison between removal and in situ management when appropriate, and evidence of a growing acceptance that the residuals and impacts of removal approaches can at times offset perceived benefits, so that in situ management can be considered if exposure risk can be properly assessed.     

Wasted fishery resources: discarded by-catch in the USA

Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.     

Seasonal habitat use by brook trout,Salvelinus fontinalis (Mitchill), in a second-order stream

Abstract Seasonal habitat use by over-yearling and under-yearling brook trout, Salvelinus fontinalis (Mitchill), was examined in a second-order stream in north-central Pennsylvania, USA. The habitat occupied by brook trout and available habitat were determined in a 0.5-km stream reach during the spring, summer and autumn of 1989 and the spring and summer of 1990. Cover, depth, substrate and velocity were quantified from over 2000 observations of individual brook trout. Habitat used by under-yearling brook trout was more uniform between seasons and years than that used by over-yearling brook trout. Over-yearling brook trout occupied areas with more cover and greater depth than did under-yearling brook trout, suggesting ontogenetic shifts in these variables. Differences for velocity and substrate were not as great as those for cover and depth. The selection of areas with low water velocities governed trout habitat use in spring, whereas cover and depth were the most important habitat variables in summer and autumn. Principal component analysis showed that available habitat and trout habitat centroids diverged most in spring, indicating that habitat selection by brook trout may be greatest at this time.