Satellite-based Estimates of Canopy Photosynthetic Parameters for an Alpine Meadow in Northern     

NIU Ben  HE Yongtao  ZHANG Xianzhou  SHI Peili  DU Mingyuan 《资源与生态学报(英文版)》2020,11(3):253-262

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Deformation history of the ophiolite sequence from the Balagne Nappe,northern Corsica: insights in the tectonic evolution of Alpine Corsica     

M. Marroni  L. Pandolfi 《Geological Journal》2003,38(1):67-83

In Alpine Corsica, the Jurassic ophiolites represent remnants of oceanic lithosphere belonging to the Ligure‐Piemontese Basin located between the Europe/Corsica and Adria continental margins. In the Balagne area, a Jurassic ophiolitic sequence topped by a Late Jurassic–Late Cretaceous sedimentary cover crops out at the top of the nappe pile. The whole ophiolitic succession is affected by polyphase deformation developed under very low‐grade orogenic metamorphic conditions. The original palaeogeographic location and the emplacement mechanisms for the Balagne ophiolites are still a matter of debate and different interpretations for its history have been proposed. The deformation features of the Balagne ophiolites are outlined in order to provide constraints on their history in the framework of the geodynamic evolution of Alpine Corsica. The deformation history reconstructed for the Balagne Nappe includes five different deformation phases, from D1 to D5. The D1 phase was connected with the latest Cretaceous/Palaeocene accretion into the accretionary wedge related to an east‐dipping subduction zone followed by a Late Eocene D2 phase related to emplacement onto the Europe/Corsica continental margin. The subsequent D3 phase was characterized by sinistral strike‐slip faults and related deformations of Late Eocene–Early Oligocene age. The D4 and D5 phases were developed during the Early Oligocene–Late Miocene extensional processes connected with the collapse of the Alpine belt. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A quantitative assessment of snow shielding effects on surface exposure dating from a western North American 10Be data compilation     

《Quaternary Geochronology》2023

To better assess the spatiotemporal variations of the snow shielding effect on surface exposure dating, we compiled a dataset of 1341 ¹⁰Be ages from alpine moraines and glacially eroded valleys across western North America, and conducted a sensitivity test with both modern and time-integrated snow data covering the same region. Our analyses reveal significant differences in snow shielding both across our geographic domain and through time. In our time-integrated experiments we find snow-based exposure age corrections as low as 3.5% in the Great Basin region and high as 28.4% in the Pacific Northwest for samples dating to the Last Glacial Maximum (LGM) when no wind-sweeping is assumed. As demonstrated with our time-varying snow conditions with a global climate model and a positive degree day model, modern snow conditions across western North America cannot account for the varying snow patterns under large scale climate shifts since the LGM. The snow-based exposure age corrections from the modern data differ from those calculated by our time-varying model by up to 17% across our model domain. In addition, we find that the ¹⁰Be ages calculated under two end-member scenarios regarding wind-sweeping effects, specifically whether boulders were shielded only when the total snow accumulation exceeded boulder heights or were always shielded when the snow was present, can differ by ∼7.6% on average for LGM aged samples. Our analyses provide a model-based estimates of the spatiotemporal variability and complexity of snow shielding effects on surface exposure dates across western North America and highlight the need to consider snow depth variations both spatially and temporally when conducting surface exposure dating in terrains where snowfall accumulation is significant.  相似文献   

天山天池水体季节性分层特征   总被引：4，自引：1，他引：3  

王斌  马健  王银亚  尹湘江 《湖泊科学》2015,27(6):1197-1204

于2014年6-10月,对高山深水湖泊天山天池水温、电导率、溶解氧、p H值、叶绿素a浓度和蓝绿藻细胞密度进行垂直剖面的连续监测,通过对其季节动态和垂直分层结构的分析,探讨天池水体季节性分层特征.天池出现明显水温分层的时间短(6-9月),夏季温跃层变化范围为2~18 m,而秋季温跃层不断下移,10月在18 m水深以下;受水温分层影响,天池水体溶解氧浓度、电导率、p H值、叶绿素a浓度和蓝绿藻细胞密度在垂直剖面表现出明显的季节性分层,尤其是夏季水温分层影响溶解氧浓度、叶绿素a浓度和蓝绿藻细胞密度在水体中的分布,对天池水质变化产生重要影响.天池浅水层(水深小于10 m)溶解氧浓度较高(大于8 mg/L),而深水层(水深超过18 m)溶解氧浓度9月接近4 mg/L,季节性缺氧导致底泥营养盐向上扩散,对水体水质产生不利影响.所以,应在夏、秋季节加强水质监测,以防止天池水华发生;天池叶绿素a浓度与蓝绿藻细胞密度的垂直剖面变化趋势相似,均随水深增加呈先增加后减小的趋势,但叶绿素a浓度在2~12 m水深处较高,蓝绿藻细胞密度在5~15 m水深处较高,表明5~15 m深度适合藻类生长,同时,电导率、p H值的垂直变化也说明藻类的生长情况,这为监测天池水体富营养化取样和分析提供依据.  相似文献   

海洋生物诞生过程、新资源发掘与高值利用     

刘建国  刘洋  王海艳  庞通  肖永双  杨娜 《海洋与湖沼》2021,52(2):537-550

本文以46亿年来地球、海洋及生命的形成与演化为主线,简要回顾了生命体由简单到复杂、从低级向高级、从水生到陆生逐级演化的历史进程,以及重大环境变化事件对生物毁灭性灭绝、生物适应与多样性演化的影响,阐明海洋尤其热带海洋在生命诞生、孕育及庇护等过程中所发挥的不可替代作用。同时,分析了热带海洋生物资源多样性中心形成的重要自然环境因素及可能机制。并针对印太交汇区深海极端环境微生物生态系统、浅海典型的海草/藻床、珊瑚礁、生物多样性和热带渔业资源,论述了热带海洋生物多样性资源的保护、发掘与高值开发利用。  相似文献   

Near-bankfull floods in an Alpine stream: Effects on the sediment mobility and bedload magnitude   总被引：1，自引：0，他引：1  

Riccardo Rainato  Luca Mao  Lorenzo Picco 《国际泥沙研究》2018,33(1):27-34

In a mountain environment, the transport of coarse material is a key factor for many fields such as geomorphology, ecology, hazard assessment, and reservoir management. Despite this, there have been only a few field investigations of bedload, in particular using multiple monitoring methods. In this sense, attention has frequently focused on the effects of “high magnitude/low frequency floods” rather than on “ordinary events”. This study aims to analyze the sediment dynamics triggered by three high-frequency floods (recurrence interval “RI” between 1.1 and 1.7 yr) that occurred in the Rio Cordon basin during 2014. The flood events were investigated in terms of both sediment mobility and bedload magnitude. The Rio Cordon is an Alpine basin located in northeastern Italy. The catchment has a surface area of 5 km², ranging between 1763 and 2763 m above sea level. The Rio Cordon flows on an armored streambed layer, with a stable step-pool configuration and large boulders. Since 1986, the basin has been equipped with a permanent station to continuously monitor water discharge and sediment flux. To investigate sediment mobility, 250 PIT-tags were installed in the streambed in 2012. The 2014 floods showed a clear difference in terms of tracer displacement. The near-bankfull events showed equal mobility conditions, with mean travel distance one order of magnitude higher than the below-bankfull event. Furthermore, only the near-bankfull events transported coarse material to the monitoring station. Both events had a peak discharge up to 2.06 m³ s^-1, but the bedload transport rates differed by more than one order of magnitude, proving that under the current supply-limited condition, the bedload appears more related to the sediment supply than to the magnitude of the hydrological features. In this sense, the results demonstrated that near-bankfull events can mobilize large amounts of material for long distances, and that floods of apparently similar magnitude may lead to different sediment dynamics, depending on the type and amount of sediment supply.  相似文献   

长江黄河源区高寒草甸退化研究进展     

徐丽华  李梅  谢德体 《测绘与空间地理信息》2010,33(1):3-7

长江黄河源区内高寒草甸退化是当前研究的热点问题之一。但多数研究中涉及的源区范围、高寒草甸的分类、高寒草甸的退化原因及恢复治理措施等方面,各学者的看法并不相同,难以实现各项研究结果的比较研究。从源区范围、高寒草甸的分类、高寒草甸的退化原因及恢复治理措施等方面阐述了各学者研究的差异,指出:长江黄河源区高寒草甸的进一步深入研究有必要对源区的范围进行界定;高寒草甸的分类常常因研究目的不同而有所差异,以退化程度进行的分类能够反映高寒草甸的动态变化过程,但需要定量指标对退化的不同程度进行界定;遥感影像解译的结果由于遥感影像本身的不确定性和主观因素的影响而难以统一;退化的原因目前主要集中于自然因素和人为因素两方面的研究,针对这些因素采取的控制措施在局部区域取得了一定效果,但并没有抑制高寒草甸在总体上的进一步退化,寻找一种综合的有效的治理措施还是今后的研究目标。  相似文献   

Using path analysis to identify the influence of climatic factors on spring peak flow dominated by snowmelt in an alpine watershed   总被引：4，自引：1，他引：4  

Fei-Yun Zhang  Lan-Hai Li  Sajjad Ahmad  Xue-Mei Li 《山地科学学报》2014,11(4):990-1000

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Systems of agriculture farming in the Uttranchal Himalaya,India     

VishwambharPrasadSati 《山地科学学报》2005,2(1):76-85

Agricultural practices are the main stay of the people of Uttranchal. Out of the total population,more than 75% people are engaged either with the main occupation of agriculture or its allied practices,dominated by traditional subsistence cereal farming.Among them, the main crops are rice, wheat, millet,barley, all types of pulses, all types of oilseeds and almost all types of fruits. The crops, vegetables and fruits of all varieties are grown in the different climatic zones such as tropical, temperate, and cold because, the region is characterized by the different altitudinal zones elevated from 200 m to more than 8000m. As a result, different climates are found from hot tropical to sub temperate and chilly cold. Pulses varieties are grown extensively. Among vegetables,potato, onion, carrot, all types of green leaf vegetables,brinzal, pumpkin, ladyfinger, pea, gram, radish,ginger, garlic, etc, are grown widely. All fruit varieties are grown in the different altitudinal zones. The mainfruits are orange, malta (a big size of orange),elephant citrus, lemon and all other types of citrus,apple, stone fruits including peach and pears, manykinds of nuts, and the fruits which are grown in the low lying areas. In spite of feasible climatic conditions,agricultural dominant society, and availability of all types of crops, the production and productivity of these crops are very low, even they are unable to meet the grain-need of the people in Uttaranchal. Agricultural crops are grown almost in all the altitudinal zones -- from the low-lying areas, which are called ‘Ga. ngarh‘, to the highly elevated region,where the legendary term is given as ‘Danda‘. The growing seasons vary according to the heights. The present paper aims to discuss the agricultural practices including cropping season, cropping pattern,land use, production of cropsagricultural system in thisand ecological aspect of Himalayan state and suggest some measures for developing farming system,which could lead the sustainability, in terms of meeting the food grain needs of the people on the one hand and restoring the ecological balance on the other.  相似文献   

Analysis of suspended sediment dynamics at event scale: comparison between a Mediterranean and an Alpine basin     

Stefano Giorgio Pagano  Adriana García-Rama  Francesco Gentile  Mario Aristide Lenzi 《水文科学杂志》2019,64(8):948-961

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