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Different morphology of Nuphar lutea in two contrasting aquatic environments and its effect on ecosystem engineering 
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下载免费PDF全文 Jonas Schoelynck Kris Bal Veerle Verschoren Ellis Penning Eric Struyf Tjeerd Bouma Dieter Meire Patrick Meire Stijn Temmerman 《地球表面变化过程与地形》2014,39(15):2100-2108
Aquatic plants (macrophytes) can have a large effect on river hydraulics and geomorphology. Though, the extent to how plant morphological plasticity actively influences these feedbacks has received little scientific attention. The nymphaeid macrophyte species Nuphar lutea (L.) Smith is characterized by a distinct leaf duality. Floating leaves shade most of the submerged leaves thereby limiting light penetration in the water. Despite their apparent negligible photosynthetic role, submerged leaves of N. lutea remain intact during summer and contribute a significant part to the total biomass. Our results indicate that the submerged leaves are crucial in plant–flow interactions and hence in the engineering potential of the plant, i.e. the capacity to locally reduce flow velocities and to promote sedimentation, including organic matter deposition. Plant individuals growing in running river water were compared to individuals from adjacent oxbow lake water. The number and size of submerged leaves were significantly higher for river standing individuals and the accumulated sediment contained significantly more organic matter, total nitrogen and total phosphorus, and was characterized by a lower carbon/nitrogen ratio and a finer grain size. We therefore argue that the submerged N. lutea canopy in rivers has the ability to create a high‐nutrient, low hydrodynamic environment, resembling the conditions found in oxbow lakes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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On the Elimination of Bias Averaging-Errors in Proxy Records 总被引：2，自引：2，他引：0
Veerle Beelaerts Fjo De Ridder Nele Schmitz Maite Bauwens Frank Dehairs Johan Schoukens Rik Pintelon 《Mathematical Geosciences》2009,41(2):129-144
Knowledge of and insight into past environmental conditions can be obtained by processing and analyzing proxies. The proxies
need to be processed as precisely and accurately as possible, otherwise the conclusion of the analysis will be biased. A calibration
method which reduces bias errors in the proxy measurements due to averaging is presented. Sampling with nonzero sample sizes
causes an averaging of the true proxy signal over the volume of the sample. The method is applied on a linear synthetic record
which results in an optimal correction for frequency components ranging from the dc-frequency (DC) to one half of the sample
frequency (f
s
/2). Next, the method is tested on non-linear synthetic data where the signal is reconstructed reasonably well. Finally, the
method is applied to a real vessel density record of R.
mucronata from Makongeni, Kenya, and to a real delta deuterium record of ice core EDC from dome C, Antarctica. The method discussed
in this paper is a valuable tool for the calibration of proxy measurements; it can be applied as a correction for low resolution
measurements and expanded to other types of samples and proxies. Working with small sample sizes (high resolution) amounts
to working near the detection limit, where the signal-to-noise-ratio is low. This correction method provides an alternative
in which low resolution measurements can be upgraded to minimize the loss of information due to larger sample sizes. 相似文献
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Katrin Heindel Jürgen Titschack Boris Dorschel Veerle A.I. Huvenne André Freiwald 《Continental Shelf Research》2010
Here we provide a detailed qualitative and quantitative insight on recent sediment composition and facies distribution of a cold-water coral (CWC) mound using the example of the Propeller Mound on the Irish continental margin (Hovland Mound Province, Porcupine Seabight). Five facies types on Propeller Mound are defined: (1) living coral framework, (2) coral rubble, (3) dropstone, (4) hardground, representing the on-mound facies, and (5) hemipelagic sediment facies, which describes the off-mound area. This facies definition is based on already published video-data recorded by Remotely Operated Vehicle (ROV), photo-data of gravity cores, box cores, and dredges from sediment surfaces as well as on the composition of the sediment fraction coarser than 125 μm, which has been analyzed on five selected box cores. Sediment compositions of the living coral framework and coral rubble facies are rather similar. Both sediment types are mainly produced by corals (34 and 35 wt%, respectively), planktonic foraminifers (22 and 29 wt%, respectively), benthic foraminifers (both 7 wt%), and molluscs (21 and 10 wt%, respectively), whereas the living coral framework characteristically features additional brachiopods (6 wt%). Hardgrounds are well-lithified coral rudstones rich in coral fragments (>30 surf%), foraminifers, echinoderms, and bivalves. The dropstone facies and the hemipelagic sediment typically carry high amounts of lithoclasts (36 and 53 wt%, respectively) and planktonic foraminifers (35 and 32 wt%, respectively); however, their faunal diversity is low compared with the coral-dominated facies (12 and <2 wt% coral fragments, 7 and 6 wt% benthic foraminifers, and 4 and 0 wt% balanids). Using the maximum likelihood algorithm within ArcGIS 9.2, spatial prediction maps of the previously described mound facies are calculated over Propeller Mound and are based on mound morphology parameters, ground-truthed with the sedimentary and faunal information from box cores, photographs, and video-data. This method is tested for the first time for CWC ecosystems and provides areal estimates of the predicted facies, as well as suggests further occurrences of living coral frameworks, coral rubble, and dropstones, which are not discovered in the area yet. Thus, sediment composition analysis combined with facies prediction mapping might provide a potential new tool to estimate living CWC occurrences and sediment/facies distributions on CWC mounds, which is an important prerequisite for budget calculations and definition of marine protected areas, and which will improve our understanding of CWC mound formation. 相似文献
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新元古代冰期事件作为一个显著的沉积记录,广泛留存在各个古克拉通。新元古代凤台组肉红色冰碛杂岩仅发育在华北克拉通东南缘,以单一的碳酸盐成分为主要鉴定特征。本文通过细致研究,认为华北克拉通东南缘在新元古代中晚期为陡坡镶边碳酸盐台地环境,受到海洋型冰川作用,形成了凤台组为代表的大陆边缘型冰川沉积地层。冰川运动仅局限于大陆边缘而未引入腹地陆源碎屑,导致凤台组冰碛杂岩中的基质和角砾基本来源于下伏碳酸盐岩地层,并具有冰碛沉积和重力流沉积特征。结合前人的研究资料和成果,凤台组的发育时限为埃迪卡拉纪,可对比关联华北克拉通南缘罗圈组和西缘正目观组,从而在华北克拉通周缘形成了显著的埃迪卡拉纪冰川沉积。另外,凤台组包含多套冰期—间冰期的沉积地层,应指示着次一级的冷暖气候周期,可能记录着埃迪卡拉纪冰期的完整沉积记录。厘清凤台组的沉积序列及演化过程,有利于研究碳酸盐台地在冰期—间冰期的沉积历史,继而完善不同古地理背景下的冰期沉积类型,并补充低纬度地区的冰川作用案例。 相似文献
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Hailemariam Meaza Amaury Frankl Jean Poesen Amanuel Zenebe Veerle Van Eetvelde Biadgilgn Demissie 《水文科学杂志》2018,63(6):957-977
Marginal grabens are major development corridors in Ethiopia, and need to be understood for proper assessment of the hydrological budget. This study investigates the water balance of the Aba’ala graben (553 km2) in the period 2015–2016 under the challenge of data scarcity. We measured the rainfall and river discharge in order to analyse the runoff components of the graben. The rainfall volume in the Aba’ala graben showed erratic behaviour, which led to rapid flood runoff of the major river into the graben bottom. The average annual inflow and outflow of the graben bottom for the period 2015–2016 amounted to 364 and 254 hm3, respectively. However, flood runoff and evapotranspiration had a marked effect on water availability. Water storage took 36% of the water inflow into the graben bottom. Sustainable water management could reduce the temporal variation of the water storage in Aba’ala graben. 相似文献
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Kristien Ooms Philippe De Maeyer Veerle Fack Eva Van Assche Frank Witlox 《International journal of geographical information science》2013,27(10):1773-1788
The experiments described in this article combine response time measurements and eye movement data to gain insight into the users' cognitive processes while working with dynamic and interactive maps. Experts and novices participated in a user study with a ‘between user’ design. Twenty screen maps were presented in a random order to each participant, on which he had to execute a visual search. The combined information of the button actions and eye tracker reveals that both user groups showed a similar pattern in the time intervals needed to locate the subsequent names. From this pattern, information about the users' cognitive load could be derived: use of working memory, learning effect and so on. Moreover, the response times also showed that experts were significantly faster in finding the names in the map image. This is further explained by the eye movement metrics: experts had significantly shorter fixations and more fixations per second meaning that they could interpret a larger part of the map in the same amount of time. As a consequence, they could locate objects in the map image more efficiently and thus faster. 相似文献
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The Tree Shelter site dates to the Early to Mid-Holocene (8000 to 4900 14C yr BP). Present conditions around the site are hyperarid, but charcoal remains indicate less severe aridity at the time of its occupation. The environment around the site then supported a rich wadi vegetation, which allowed hunting during the Epipaleolithic and herding during the Neolithic occupation. Although more favorable than today, the environmental conditions also displayed a desert character and seem to have limited the range of domestic herbivores introduced in the area. 相似文献