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141.
Marsh surface sediment deposition and the role of tidal creeks: Implications for created and managed coastal marshes 总被引:3,自引:0,他引:3
Denise J. Reed Thomas Spencer Anne L. Murray Jonathan R. French Lynn Leonard 《Journal of Coastal Conservation》1999,5(1):81-90
The need to understand the processes contributing to marsh sedimentation has become more urgent with the recent recognition
of the role of tidal marshes as sea defences, as well as the many restoration efforts currently under way. This study was
designed to build upon previous sedimentation work at Scolt Head Island by Combining techniques for measuring short-term sedimentation,
with detailed assessment of hydroperiod, previously used only in comparison with longer-term accretion measurements or in
micro-tidal systems. Measurements of water level, sediment deposition (at various distances from the creek margin) and suspended
sediment concentration (SSC) (creek margin and an interior site) were made at Hut Marsh over three sequential over-marsh tides
during May 1994. Sediment trap data show a significant trend of declining sediment deposition away from the creek when data
from all three tides are combined. All tides show higher SSC on the flood tide than on the ebb tide at the creek margin location.
There is little difference in flood and ebb SSCs at the interior site. An order of magnitude decrease in sediment deposition
within 20 m on the creek shows the rapidity with which sediment is deposited on these marshes. Higher tides influence both
the magnitude and pattern of marsh surface sediment deposition. Increased creek velocities on higher tides provide more potential
for resuspension within the creek and increase the supply of sediment to the marsh surface. This study suggests that the design
of tidal creeks may be essential for the development of sustainable coastal marshes in restoration projects. 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.
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
144.
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
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146.
Francesca Romana Grati Denise Molina Gomes Jose Carlos Pinto B. Ferreira Celine Dupont Viola Alesi Laetitia Gouas Nina Horelli-Kuitunen Kwong Wai Choy Sandra García-Herrero Alberto Gonzalez de la Vega Krzysztof Piotrowski Rita Genesio Gloria Queipo Barbara Malvestiti Bérénice Hervé Brigitte Benzacken Antonio Novelli Philippe Vago Kirsi Piippo Tak Yeung Leung Federico Maggi Thibault Quibel Anne Claude Tabet Giuseppe Simoni François Vialard 《黑龙江环境通报》2015,35(8):801-809
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