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141.
We combined a natural experiment with field surveys and GIS to investigate the effects of dust from recreational trails and
access roads on the federally threatened Valley elderberry longhorn beetle (“VELB,” Desmocerus californicus dimorphus) and its host plant, elderberry (Sambucus mexicana). Dust is listed in the species recovery plan as a threat to the VELB and unpaved surfaces are common throughout the riparian
corridors where the VELB lives, yet the effects of dust on the VELB have been untested. We found that dust deposition varied
among sites and was highest within 10 m of trails and roads, but was similar adjacent to dirt and paved surfaces within sites.
Elderberry density did not differ with distance from dirt surfaces. Despite similar within-site dust levels, elderberry adjacent
to paved surfaces were less stressed than those near dirt ones, possibly because increased runoff from paved surfaces benefited
elderberry. Dust deposition across sites was weakly correlated with elderberry stress symptoms (e.g., water stress, dead stems,
smaller leaves), indicating that ambient dust (or unmeasured correlates) influenced elderberry. Direct studies of the VELB
showed that its distribution was not negatively affected by the proximity to dirt surfaces. Dust from low traffic dirt and
paved access roads and trails, therefore, affected VELB presence neither directly nor indirectly through changed elderberry
condition. These results suggest that the placement of VELB mitigation, restoration, and conservation areas can proceed independently
of access roads if dust and traffic levels do not exceed those in our study site. Furthermore, dust control measures are likely
to be unnecessary under such conditions. The potential effects of increased traffic and dust levels are addressed through
a literature review. 相似文献
142.
Larry S. Dolan Denise K DeLuca 《Journal of the American Water Resources Association》1993,29(1):107-117
ABSTRACT: The Montana Department of Natural Resources and Conservation developed a hydrologic model to help analyze the effects of allocating water for consumptive and instream uses in the upper Missouri River basin of Montana. The model, a PC-based FORTRAN program, uses a mass-balance approach to compute monthly streamflows, reservoir operations, hydropower production, and irrigation and municipal water uses throughout the 54,000 square mile basin for a 59-year base period. Simulation results are presented as monthly mean and percentile-exceedence values. The model was run for baseline conditions and six hypothetical water-allocation alternatives. Results were used by staff resource area specialists to assess potential impacts to water quantity and distribution, water rights, water quality, stream channel form, fisheries, wildlife, recreation, hydropower production, and economics. These analyses were presented to the public and the decision-making board in an environmental impact statement (EIS). Though, in many instances, the model did not allow for detailed, site-specific analyses, the model was an important tool and its simulation results formed the hydrologic basis for the EIS. 相似文献
143.
Denise Lach 《Environmental management》2014,53(1):88-93
While interdisciplinary research is increasingly practiced as a way to transcend the limitations of individual disciplines, our concepts, and methods are primarily rooted in the disciplines that shape the way we think about the world and how we conduct research. While natural and social scientists may share a general understanding of how science is conducted, disciplinary differences in methodologies quickly emerge during interdisciplinary research efforts. This paper briefly introduces and reviews different philosophical underpinnings of quantitative and qualitative methodological approaches and introduces the idea that a pragmatic, realistic approach may allow natural and social scientists to work together productively. While realism assumes that there is a reality that exists independently of our perceptions, the work of scientists is to explore the mechanisms by which actions cause meaningful outcomes and the conditions under which the mechanisms can act. Our task as interdisciplinary researchers is to use the insights of our disciplines in the context of the problem to co-produce an explanation for the variables of interest. Research on qualities necessary for successful interdisciplinary researchers is also discussed along with recent efforts by funding agencies and academia to increase capacities for interdisciplinary research. 相似文献
144.
Ann T. Chalmers Denise M. Argue David A. Gay Mark E. Brigham Christopher J. Schmitt David L. Lorenz 《Environmental monitoring and assessment》2011,175(1-4):175-191
A national dataset on concentrations of mercury in fish, compiled mainly from state and federal monitoring programs, was used to evaluate trends in mercury (Hg) in fish from US rivers and lakes. Trends were analyzed on data aggregated by site and by state, using samples of the same fish species and tissue type, and using fish of similar lengths. Site-based trends were evaluated from 1969 to 2005, but focused on a subset of the data from 1969 to 1987. Data aggregated by state were used to evaluate trends in fish Hg concentrations from 1988 to 2005. In addition, the most recent Hg fish data (1996?C2005) were compared to wet Hg deposition data from the Mercury Deposition Network (MDN) over the same period. Downward trends in Hg concentrations in fish from data collected during 1969?C1987 exceeded upward trends by a ratio of 6 to 1. Declining Hg accumulation rates in sediment and peat cores reported by many studies during the 1970s and 1980s correspond with the period when the most downward trends in fish Hg concentrations occurred. Downward Hg trends in both sediment cores and fish were also consistent with the implementation of stricter regulatory controls of direct releases of Hg to the atmosphere and surface waters during the same period. The southeastern USA had more upward Hg trends in fish than other regions for both site and state aggregated data. Upward Hg trends in fish from the southeastern USA were associated with increases in wet deposition in the region and may be attributed to a greater influence of global atmospheric Hg emissions in the southeastern USA. No significant trends were found in 62% of the fish species from six states from 1996 to 2005. A lack of Hg trends in fish in the more recent data was consistent with the lack of trends in wet Hg deposition at MDN sites and with relatively constant global emissions during the same time period. Although few significant trends were observed in the more recent Hg concentrations in fish, it is anticipated that Hg concentrations in fish will respond to changes in atmospheric Hg deposition, however, the magnitude and timing of the response is uncertain. 相似文献
145.
Kiwon Park Karl S. Rosengren Gavin P. Horn Denise L. Smith Elizabeth T. Hsiao-Wecksler 《Safety Science》2011,49(5):719-726
Each year, roughly 11,000 firefighters are injured as a result of slips, trips and falls, which account for over 25% of all fireground injuries. Wearing personal protective equipment (PPE) can increase risk of fall-related injuries due to its weight, restrictiveness, and increased heat stress. Modification of PPE may serve to mitigate firefighter injuries related to loss of balance and falls. We examined the effects of choosing ‘enhanced’ protective clothing (lightweight, breathable, and less restrictive compared to typical firefighting PPE) and simulated firefighting tasks (18-min bout over four activities) on subsequent gait performance. To assess the effect of wearing protective clothing and firefighting activity, seven gait parameters and three movement errors were assessed during level and obstacle-crossing walking tasks. Forty-four firefighters wore one of two types of PPE (‘Standard’, ‘Enhanced’) during three testing conditions (baseline in station uniform, pre-firefighting activity in PPE, and post-firefighting activity in PPE). The effect of donning any PPE was found to significantly impair gait performance. Fatigue may impact effective mobility since more movement errors were observed during post-activity than pre-activity assessments. Although the Enhanced PPE did not lead to any significant differences in gait parameters compared to Standard PPE, participants in Enhanced PPE made twice as many movement errors, potentially attributed to lack of familiarity with the gear. These results suggest that wearing firefighting PPE and heat-stress induced fatigue are associated with reduced gait performance and increased risk for tripping over obstacles. 相似文献
146.
The effect of dairy farming on water quality in New Zealand streams has been identified as an important environmental issue. Stream fencing, to keep cattle out of streams, is seen as a way to improve water quality. Fencing ensures that cattle cannot defecate in the stream, prevents bank erosion, and protects the aquatic habitat. Stream fencing targets have been set by the dairy industry. In this paper the results of a study to identify the factors influencing dairy farmers' decisions to adopt stream fencing are outlined. Qualitative methods were used to gather data from 30 dairy farmers in four New Zealand catchments. Results suggest that farm contextual factors influenced farmers' decision making when considering stream fencing. Farmers were classified into four segments based on their reasons for investing in stream fencing. These reasons were fencing boundaries, fencing for stock control, fencing to protect animal health, and fencing because of pressure to conform to local government guidelines or industry codes of practice. This suggests that adoption may be slow in the absence of on-farm benefits, that promotion of stream fencing needs to be strongly linked to on-farm benefits, and that regulation could play a role in ensuring greater adoption of stream fencing. 相似文献
147.
148.
Denise M. Rousseau 《组织行为杂志》1990,11(5):389-400
Psychological contracts are individual beliefs in reciprocal obligations between employees and employers. In a sample of 224 graduating MBA students who had recently accepted job offers, beliefs regarding employment obligations were investigated. Two types of obligation were demonstrated empirically: transactional obligations of high pay and career advancement in exchange for hard work and relational obligations exchanging job security for loyalty and a minimum length of stay. These types of obligations are connected with two forms of legal contracts: transactional and relational. Relational contract obligations for employers correlated with employee expected length of stay with the firm. Transactional contract obligations were associated with careerist motive on the part of new recruits. The relationship between these and other motives of new hires was also investigated. 相似文献
149.