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741.
Circulation and Stream Plume Modeling in Conesus Lake 总被引:1,自引:0,他引:1
Yan Li Anthony Vodacek Nina Raqueño Robert Kremens Alfred J. Garrett Isidro Bosch Joseph C. Makarewicz Theodore W. Lewis 《Environmental Modeling and Assessment》2008,13(2):275-289
A three-dimensional hydrodynamic model that includes the effect of drag from macrophytes was applied to Conesus Lake to study
the seasonal circulation and thermal structure during spring and early summer. Local weather conditions and stream flow data
were used to drive the model. The drag coefficient for macrophytes was calculated as a function of leaf density. In general,
the model results show good agreements with the observations, including vertical temperature profiles measured at two locations
and average surface temperature derived from calibrated thermal imagery for large-scale simulations of the entire lake. Additional
high-resolution simulations were carried out to understand water circulation and transport of sediment and model-generated
tracer during hydrometeorological events at stream mouths for two experimental sites. The model results show that the plume
development at stream mouths during storm events in Conesus Lake are site-dependent and may either be current- or wind-driven.
The results also show a significant effect from the presence of macrophytes on sediment deposition near stream mouths. 相似文献
742.
743.
陈红 《长江流域资源与环境》2017,26(5):771-777
利用CMIP5三个耦合模式的历史模拟及不同情景预测结果、NCEP/NCAR再分析资料和长江中下游观测降水资料,采用统计降尺度方法对长江中下游夏季极端降水频次进行模拟和预估。首先,通过计算相关的方法,获取建立统计降尺度预测模型所需的预测因子。提取的预测因子同时满足既是观测环流要素场影响极端降水的关键区域,又是模式要素场预报的高技巧区域两个条件;然后,结合挑选出的预测因子,利用多元线性回归方法建立长江中下游极端降水的统计降尺度预测模型,并对模型性能进行检验。交叉检验结果表明,此种统计降尺度方法能对过去长江中下游极端降水变化有较好的再现能力,且多个降尺度模型结果的集合能进一步提高降尺度方法的模拟技巧;最后,将建立的统计降尺度模型应用于CMIP5未来3种不同的排放情景来对极端降水进行未来预估,并对多模式结果进行集合。结果显示,统计降尺度模型预估未来几个年代际长江中下游夏季极端降水频次相对于1986~2005年呈增加趋势,21世纪中、后期高排放情景下极端降水频次增加幅度高于低排放情景。 相似文献
744.
有机氯农药(Organochlorine pesticides,OCPs)曾在全世界被大量使用,即使禁用多年,仍能在各种环境介质中被广泛检出,对生态环境和人体健康存在着潜在的威胁。因此OCPs的环境迁移和归趋一直是该领域的研究热点。树皮是一种天然的被动采样器,能够很好的反映出大气有机物长期的污染程度。本文简要论述了树皮作为被动采样器在大气污染物监测研究中应用的优势,并对OCPs在树皮中的残留浓度、特征及影响其富集的因素进行了探讨,最后特别针对具有手性的OCPs在树皮中的对映体选择性特征进行了评述。 相似文献
745.
为了实现石油企业的效益与安全兼顾,引入安全管理的事故树(FTA)分析法查找主要风险点,利用计算机软件模拟预测主营业务的生产流程,对每个技术环节定量计算、精准投入,规避并控制风险点,在收获并保护油层的同时保证安全生产,从而实现效益与安全兼顾;通过实例表明,该方法在企业的安全管理中是可行的. 相似文献
746.
合理确定战场防护需求是对野战弹药实施合理防护的前提。通过对野战弹药防护系统的分析,建立了野战弹药非战斗损耗事故树,对事故树进行了定性、定量分析,确定了野战弹药防护的主要内容,并在此基础上提出了野战弹药综合防护系统设计方案。 相似文献
747.
我国神农架林区海拔高、气候复杂,森林类型多样,结构破碎,森林遥感分类难度较大。将2013年时间序列HJ-1A/B CCD遥感影像作为数据源,计算出植被指数(NDVI、DVI、RVI)和主成分第一分量(PC1),使用DEM数据生成地形因子(高程、坡度、坡向),构建植被分类时序因子集。运用C5.0决策树分类法将神农架林区植被细分为七类:针叶林;针阔混交林;落叶阔叶林;常绿和落叶阔叶混交林;常绿阔叶林;灌丛和草甸。结果表明:该方法的总体精度为72.7%,Kappa系数为0.67;在6~8月,针叶林、草甸和灌丛的植被指数明显低于常绿阔叶林、常绿和落叶阔叶混交林、落叶阔叶林和针阔混交林,对分类的贡献较大,称为植被分类的"窗口期"。PC1、NDVI和高程因子对神农架林地的区分度较高,而坡度、坡向和RVI因子对分类帮助不大。作为一种智能分类方法,C5.0决策树分类方法应用于30m分辨率的时间序列HJ-1A/B CCD数据,能够将地貌复杂的神农架林区植被分为七类,提高了类别精度,具有更高的应用价值。 相似文献
748.
SOON-WOONG CHANG SI-JIN LEE CHUNG-HWAN JE 《Journal of environmental science and health. Part. B》2013,48(6):801-811
Toxicity, uptake, and transformation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] by three species of poplar tree were assessed. Poplar cuttings were grown in sealed flasks with hydrophonic solutions and exposed to various concentrations of atrazine for a period of two weeks. Toxicity effects were evaluated by monitoring transpiration and measuring poplar cutting mass. Exposure to higher atrazine concentrations resulted in decrease of biomass and transpiration accompanied by leaf chlorosis and abscission. However, poplar cuttings exposed to lower concentrations of atrazine grew well and transpired at a constant rate during experiment periods. Poplar cuttings could take up, hydrolyze, and dealkylate atrazine to less toxic metabolites. Metabolism of atrazine occurred in roots, stems, and leaves and became more complete with increased residence time in tissue. These results suggest that phytoremediation is a viable approach to removing atrazine from contaminated water and should be considered for other contaminants. 相似文献
749.
The loss of large animals due to overhunting and habitat loss potentially affects tropical tree populations and carbon cycling. Trees reliant on large-bodied seed dispersers are thought to be particularly negatively affected by defaunation. But besides seed dispersal, defaunation can also increase or decrease seed predation. It remains unclear how these different defaunation effects on early life stages ultimately affect tree population dynamics. We reviewed the literature on how tropical animal loss affects different plant life stages, and we conducted a meta-analysis of how defaunation affects seed predation. We used this information to parameterize models that altered matrix projection models from a suite of tree species to simulate defaunation-caused changes in seed dispersal and predation. We assessed how applying these defaunation effects affected population growth rates. On average, population-level effects of defaunation were negligible, suggesting that defaunation may not cause the massive reductions in forest carbon storage that have been predicted. In contrast to previous hypotheses, we did not detect an effect of seed size on changes in seed predation rates. The change in seed predation did not differ significantly between exclosure experiments and observational studies, although the results of observational studies were far more variable. Although defaunation surely affects certain tree taxa, species that benefit or are harmed by it and net changes in forest carbon storage cannot currently be predicted based on available data. Further research on how factors such as seed predation vary across tree species and defaunation scenarios is necessary for understanding cascading changes in species composition and diversity. 相似文献
750.
Daniel Kozák Marek Svitok Veronika Zemlerová Martin Mikoláš Thibault Lachat Laurent Larrieu Yoan Paillet Arne Buechling Radek Bače William S. Keeton Lucie Vítková Krešimir Begovič Vojtěch Čada Martin Dušátko Matej Ferenčík Michal Frankovič Rhiannon Gloor Jeňýk Hofmeister Pavel Janda Ondrej Kameniar Tomáš Kníř Linda Majdanová Marek Mejstřík Jakob Pavlin Dheeraj Ralhan Ruffy Rodrigo Catalin-Constantin Roibu Michal Synek Ondřej Vostarek Miroslav Svoboda 《Conservation biology》2023,37(3):e14066
Protecting structural features, such as tree-related microhabitats (TreMs), is a cost-effective tool crucial for biodiversity conservation applicable to large forested landscapes. Although the development of TreMs is influenced by tree diameter, species, and vitality, the relationships between tree age and TreM profile remain poorly understood. Using a tree-ring-based approach and a large data set of 8038 trees, we modeled the effects of tree age, diameter, and site characteristics on TreM richness and occurrence across some of the most intact primary temperate forests in Europe, including mixed beech and spruce forests. We observed an overall increase in TreM richness on old and large trees in both forest types. The occurrence of specific TreM groups was variably related to tree age and diameter, but some TreM groups (e.g., epiphytes) had a stronger positive relationship with tree species and elevation. Although many TreM groups were positively associated with tree age and diameter, only two TreM groups in spruce stands reacted exclusively to tree age (insect galleries and exposed sapwood) without responding to diameter. Thus, the retention of trees for conservation purposes based on tree diameter appears to be a generally feasible approach with a rather low risk of underrepresentation of TreMs. Because greater tree age and diameter positively affected TreM development, placing a greater emphasis on conserving large trees and allowing them to reach older ages, for example, through the establishment of conservation reserves, would better maintain the continuity of TreM resource and associated biodiversity. However, this approach may be difficult due to the widespread intensification of forest management and global climate change. 相似文献