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31.
Fire is a natural part of most forest ecosystems in the western United States, but its effects on nonnative plant invasion have only recently been studied. Also, forest managers are engaging in fuel reduction projects to lessen fire severity, often without considering potential negative ecological consequences such as nonnative plant species introductions. Increased availability of light, nutrients, and bare ground have all been associated with high-severity fires and fuel treatments and are known to aid in the establishment of nonnative plant species. We use vegetation and environmental data collected after wildfires at seven sites in coniferous forests in the western United States to study responses of nonnative plants to wildfire. We compared burned vs. unburned plots and plots treated with mechanical thinning and/or prescribed burning vs. untreated plots for nonnative plant species richness and cover and used correlation analyses to infer the effect of abiotic site conditions on invasibility. Wildfire was responsible for significant increases in nonnative species richness and cover, and a significant decrease in native cover. Mechanical thinning and prescribed fire fuel treatments were associated with significant changes in plant species composition at some sites. Treatment effects across sites were minimal and inconclusive due to significant site and site x treatment interaction effects caused by variation between sites including differences in treatment and fire severities and initial conditions (e.g., nonnative species sources). We used canonical correspondence analysis (CCA) to determine what combinations of environmental variables best explained patterns of nonnative plant species richness and cover. Variables related to fire severity, soil nutrients, and elevation explained most of the variation in species composition. Nonnative species were generally associated with sites with higher fire severity, elevation, percentage of bare ground, and lower soil nutrient levels and lower canopy cover. Early assessments of postfire stand conditions can guide rapid responses to nonnative plant invasions.  相似文献   
32.
The dissipation of the fungicides captan, cyprodinil, fludioxonil, dithianon, and tebuconazole and of the insecticides chlorpyrifos, fenitrothion, and malathion was studied, following a single treatment of different cultivars of pears, apples, and peaches. The study was conducted in northern Italy, over two successive growing seasons (2004 and 2005). The treatments were performed by the farmers involved, in line with their usual practice. At various time intervals from treatment to harvest, representative samples of fruit were collected and analyzed for pesticide residues. In some cases, concentrations lower than the maximum residue levels (MRLs) were found immediately after treatment. In all trials a rapid decline in pesticide concentrations was observed leading to residues at harvest greatly below the MRLs.  相似文献   
33.
A case of aortic atresia with insufficiency of mitral valve diagnosed prenatally at 33 weeks of gestation is presented. An accurate diagnosis of this fetal cardiovascular malformation was possible by application of Doppler colour flow mapping, which demonstrated (a) the absence of forward flow in the hypoplastic ascending aorta, (b) reverse flow of blood from the ductus arteriosus into the severely hypoplastic ascending aorta in the late systole, (c) pansystolic mitral valve regurgitation, and (d) absent flow across the foramen ovale as a result of premature closure of the foramen ovale.  相似文献   
34.
The importance of information technology to the world economy has brought about a surge in demand for electronic equipment. With rapid technological change, a growing fraction of the increasing stock of many types of electronics becomes obsolete each year. We model the costs and benefits of policies to manage 'e-waste' by focusing on a large component of the electronic waste stream-computer monitors-and the environmental concerns associated with disposal of the lead embodied in cathode ray tubes (CRTs) used in most monitors. We find that the benefits of avoiding health effects associated with CRT disposal appear far outweighed by the costs for a wide range of policies. For the stock of monitors disposed of in the United States in 1998, we find that policies restricting or banning some popular disposal options would increase disposal costs from about US dollar 1 per monitor to between US dollars 3 and US dollars 20 per monitor. Policies to promote a modest amount of recycling of monitor parts, including lead, can be less expensive. In all cases, however, the costs of the policies exceed the value of the avoided health effects of CRT disposal.  相似文献   
35.
The San Francisco Bay Region of the California Regional Water Quality Control Board (SFB CRWQCB) and the San Francisco District of the US Army Corps of Engineers (US ACOE) are looking for an expeditious means to determine whether regulated wetland projects produce ecologically valuable systems and remain in compliance with their permits (i.e. fulfill their legal requirements) until project completion. A study was therefore undertaken in which 20 compensatory wetland mitigation projects in the San Francisco Bay Region were reviewed and assessed for both permit compliance and habitat function, and this was done using a rapid assessment method adapted for this purpose. Thus, in addition to determining compliance and function, a further goal of this study was to test the efficacy of the assessment method, which, if useful, could be applied not only to mitigation projects, but also to restoration projects and natural wetland systems. Survey results suggest that most projects permitted 5 or more years ago are in compliance with their permit conditions and are realizing their intended habitat functions. The larger restoration sites or those situated between existing wetland sites tend to be more successful and offer more benefits to wildlife than the smaller isolated ones. These results are consistent with regulatory experience suggesting that economies of scale could be realized both with (1) large scale regional wetland restoration sites, through which efforts are combined to control invasive species and share costs, and (2) coordinated efforts by regulatory agencies to track project information and to monitor the increasing number and size of mitigation and restoration sites. In regard to the assessment methods, we find that their value lies in providing a consistent protocol for evaluations, but that the ultimate assessment will rely heavily on professional judgment, regulatory experience, and the garnering of pre-assessment information.  相似文献   
36.
Three methods (membrane filtration, multiple tube fermentation, and chromogenic substrate technology kits manufactured by IDEXX Laboratories, Inc.) are routinely used to measure indicator bacteria for beach water quality. To assess comparability of these methods, quantify within-laboratory variability for each method, and place that variability into context of variability among laboratories using the same method, 22 southern California laboratories participated in a series of intercalibration exercises. Each laboratory processed three to five replicates from thirteen samples, with total coliforms, fecal coliforms or enterococci measured depending on the sample. Results were generally comparable among methods, though membrane filtration appeared to underestimate the other two methods for fecal coliforms, possibly due to clumping. Variability was greatest for the multiple tube fermentation method. For all three methods, within laboratory variability was greater than among laboratories variability.  相似文献   
37.
The goal of this paper is to provide a methodology for assessing the optimal localization of new monitoring stations within an existing rain gauge monitoring network. The methodology presented, which uses geostatistics and probabilistic techniques (simulated annealing) combined with GIS instruments, could be extremely useful in any area where an extension of whatever existing environmental monitoring network is planned. The methodology has been applied to the design of an extension to a rainfall monitoring network in the Apulia region (South Italy). The considered monitoring network is managed by the Apulian Regional Consortium for Crop Protection (ARCCP), and, currently consists of 45 gauging stations distributed over the regional territory, mainly located on the basis of administrative needs. Fifty new stations have been added to the existing monitoring network, split in two groups: 15 fixed and 35 mobile stations. Two different methods were applied and tested: the Minimization of the Mean of Shortest Distances method (MMSD) and Ordinary Kriging (OK) whose related objective function is estimation variance. The MMSD, being a purely geometric method, produced a spatially uniform configuration of the gauging stations. On the contrary, the approach based on the minimization of the average of the kriging estimation variances, produced a less regular configuration, though a more reliable one from a spatial standpoint. Nevertheless, the MMSD approach was chosen, since the ARCCP's intention was to create a new monitoring network characterized by uniform spatial distribution throughout the regional territory. This was the most important constraint given to the project by the ARCCP, whose main objective was to accomplish a territorial network capable of detecting hazardous events quickly. A seasonal aggregation of the available rainfall data was considered. The choice of the temporal aggregation in quarterly averages allowed four different optimal configurations to be determined per season. The overlapping of the four configurations allowed a number of new station locations, which tended to remain fixed season after season, to be identified. Other stations, instead, changed their coordinates considerably over the four seasons. Constraints were defined in order to avoid placing new monitoring locations either near existing stations, belonging to other Agencies, or near the coast line.  相似文献   
38.
Despite a common understanding of the harmful impacts of Western conservation models that separate people from nature, widespread progress toward incorporating socioeconomic, political, cultural, and spiritual considerations in conservation practice is lacking. For some, the concept of nature-based solutions (NbS) is seen as an interdisciplinary and holistic pathway to better integrate human well-being in conservation. We examined how conservation practitioners in the United States view NbS and how social considerations are or are not incorporated in conservation adaptation projects. We interviewed 28 individuals working on 15 different such projects associated with the Wildlife Conservation Society's Climate Adaptation Fund. We completed 2 rounds of iterative coding in NVivo 12.6.1 to identify in the full text of all interview responses an a priori set of themes related to our research questions and emergent themes. Many respondents saw this moment as a tipping point for the field (one in which the perceived values of social considerations are increasing in conservation practice) (76%) and that social justice concerns and the need to overcome racist and colonial roots of Western conservation have risen to the forefront. Respondents also tentatively agreed that NbS in conservation could support social and ecological outcomes for conservation, but that it was far from guaranteed. Despite individual intention and awareness among practitioners to incorporate social considerations in conservation practice, structural barriers, including limited funding and inflexible grant structures, continue to constrain systemic change. Ultimately, systemic changes that address power and justice in policy and practice are required to leverage this moment to more fully address social considerations in conservation.  相似文献   
39.
Despite the popularity of diversity training in corporate America, a lack of systematic evaluation has left managers with little guidance on how to design effective diversity training programmes. In this research, we examine how training group composition and trainee experience interact to influence the effects of diversity training on cognitive, affective, and behavioral outcomes. Results indicate that trainees with prior experience with diversity training responded most positively to training groups homogeneous with respect to racioethnicity and nationality; trainees without prior experience with diversity training were generally unaffected by training group composition. The implications of these findings for the design of diversity training programmes in organizations and future research on diversity training are discussed. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   
40.
Environmental time series are often affected by the “presence” of missing data, but when dealing statistically with data, the need to fill in the gaps estimating the missing values must be considered. At present, a large number of statistical techniques are available to achieve this objective; they range from very simple methods, such as using the sample mean, to very sophisticated ones, such as multiple imputation. A brand new methodology for missing data estimation is proposed, which tries to merge the obvious advantages of the simplest techniques (e.g. their vocation to be easily implemented) with the strength of the newest techniques. The proposed method consists in the application of two consecutive stages: once it has been ascertained that a specific monitoring station is affected by missing data, the “most similar” monitoring stations are identified among neighbouring stations on the basis of a suitable similarity coefficient; in the second stage, a regressive method is applied in order to estimate the missing data. In this paper, four different regressive methods are applied and compared, in order to determine which is the most reliable for filling in the gaps, using rainfall data series measured in the Candelaro River Basin located in South Italy.  相似文献   
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