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Models that link ecological responses to hydrologic changes are important for assessing the effects of flow regulation on aquatic and riparian ecosystems. Based on the Recruitment Box Model, a graphical model used to prescribe environmental flows for cottonwood (Populus spp.) recruitment, we designed a simulation model to represent the influence of river flow dynamics on seedling recruitment of riparian pioneer woody plants. The model simulates the influence of temporal patterns of river stage on dispersal, germination, initial recruitment and over‐winter survival of first‐year seedlings of riparian pioneer shrubs and trees. We used the model to simulate seedling recruitment patterns for five species (Acer saccharinum, Betula nigra, Populus deltoides, Salix nigra and Salix exigua) on the Wisconsin River (Wisconsin, USA) under three flow scenarios: historic (1935–2002), simulated natural (1915–1975) and simulated regulated flows (1915–1975). Simulation results agreed well with field‐observed relative differences among years (1997–2000) in seedling densities for the five focal species. Simulated successful recruitment years were highly synchronous among species, but species differed in their sensitivity to flows at different times during the growing season, consistent with among‐species differences in seed dispersal timing. Comparison of simulated natural and regulated flows for 1915–1975 showed that flow regulation decreased monthly flow variability, increased late summer to winter baseflow and reduced the magnitude of spring peaks. Simulated recruitment and over‐winter survival of tree seedlings of all species was enhanced under the regulated flow scenario, likely due to increased summer baseflow and reductions in peak flood magnitude. Our analyses show the utility of extending the Recruitment Box Model to include multiple species of riparian shrubs and trees, and the effects of post‐colonization flows on their recruitment success. However, some key functional relationships between flow patterns and woody seedling demography (e.g. shear stress thresholds for seedling mortality) have not been adequately quantified and merit further study. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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为保证核电厂反应堆压力容器与蒸汽发生器检修工作能够同时进行,需使用堵板密封装置对主管道进行封堵。这可以使得反应堆一回路水位的升降不影响蒸汽发生器的检修工作,同时也可保证人员和设备安全,避免人员或异物掉入主管道。使用西门子S7-1200 PLC作为控制器,采用全集成自动化博途软件进行编程设计。根据工艺流程,设计了可编程逻辑控制器(PLC)控制系统程序,实现了对堵板密封胶囊各腔室压力的监控。相较于市场上现有的手动调节系统,所设计的系统具有密封胶囊压力自动控制、故障远程报警功能。控制系统操作画面简洁,易于操作等特点。试验结果表明,该系统操作方便、运行可靠,可为用户在核电厂检修期间,提供一回路主管道和蒸汽发生器一次侧之间安全、可靠的隔离效果。使用该系统对充气式密封胶囊进行耐久性测试,通过对测试数据的分析,可用于优化密封胶囊的生产工艺。 相似文献
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中国拱坝数量占全世界的40%,数量最多;世界最高的三座拱坝都在中国,因此中国是世界拱坝大国。中国解决了岩溶地区拱坝防渗、狭窄河谷拱坝大流量泄洪等技术难题,发展了碾压混凝土拱坝筑坝技术。中国学者首创大坝混凝土标号分区技术,首创混凝土坝温度应力理论体系,解决了大坝裂缝这一世界性难题;建立了拱坝优化理论、混凝土坝仿真分析方法、混凝土坝有限元等效应力方法、混凝土坝数值监控方法等,在拱坝设计和科研上取得了全世界最多的重要成果,因此中国既是世界拱坝大国,又是世界拱坝强国。 相似文献
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Local‐scale Benefits of River Connectivity Restoration Planning Beyond Jurisdictional Boundaries 下载免费PDF全文
A. W. Milt P. J. Doran M. C. Ferris A. T. Moody T. M. Neeson P. B. McIntyre 《河流研究与利用》2017,33(5):788-795
Conservation planning aims to optimize outcomes for select species or ecosystems by directing resources toward high‐return sites. The possibility that local benefits might be increased by directing resources beyond the focal area is rarely considered. We present a case study of restoring river connectivity for migratory fish of the Great Lakes Basin by removing dams and road crossings within municipal jurisdictions versus their broader watersheds. We found that greater river connectivity could often be achieved by considering both intra‐jurisdictional and extra‐jurisdictional barriers. Focusing on jurisdictional barriers alone generally forfeited <20% (median = 0%) of habitat gains for those who value solely habitat gains within the jurisdiction, but >75% (median = 100%) for planners who value larger‐scale habitat gains. Similarly, cost savings tended to be between ?50% and +50%, but in some cases were very negative. Our study underscores the local‐scale benefits of broadening restoration investments, especially for decision makers of the Great Lakes Basin and contributes to a discussion of appropriate and efficient scales of conservation planning. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献