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151.
Populus nigra L. establishment and fluvial landform construction: biogeomorphic dynamics within a channelized river 下载免费PDF全文
Dov Corenblit Johannes Steiger Gaspard Charrier José Darrozes Virginia Garófano‐Gómez Alexandre Garreau Eduardo González Angela M. Gurnell Borbála Hortobágyi Frédéric Julien Luc Lambs Sébastien Larrue Thierry Otto Erwan Roussel Franck Vautier Olivier Voldoire 《地球表面变化过程与地形》2016,41(9):1276-1292
Populations of the riparian pioneer species Populus nigra L. which establish on alluvial bars within river channels modulate sediment dynamics and fluvial landforms. Dense cohorts of P. nigra have colonized gravel point bars along the channelized River Garonne, France, during the last 20 years and have enhanced the vertical, lateral and longitudinal development of the bars. For this period, the geomorphic characteristics of two wooded point bars on this laterally stable river are closely linked to the spatial distribution and intensity of establishment and resistance of different cohorts of P. nigra. Furthermore, P. nigra colonization dynamics were controlled by engineer effects of this same species. This relationship is illustrated by a significant correlation between key geomorphic and biological variables measured in situ and characterized with a set of four aerial photographs taken between 2000 and 2010. The development of wooded point bars, which are discrete biogeomorphic units, over the studied period, appear to result from a specific biogeomorphic positive feedback of matter aggregation and vegetation establishment related to sediment trapping and stabilization by pioneer engineer plants. We propose a conceptual model of biogeomorphic unit construction for channelized, lateral stable rivers. We consider the resultant biogeomorphic units as functional from an ecological point of view because P. nigra enhances at the cohort scale (i) its own inherent capacity to resist hydrogeomorphic disturbances, and (ii) its resilience capacity as a result of successful colonization, especially downstream of mature poplar stands. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
152.
Guillaume Bertrand Hélène Celle-Jeanton Sébastien Loock Frédéric Huneau Véronique Lavastre 《Aquatic Geochemistry》2013,19(2):147-171
Mineralization of groundwater in volcanic aquifers is partly acquired through silicates weathering. This alteration depends on the dissolution of atmospheric, biogenic, or mantellic gaseous CO2 whose contributions may depend on substratum geology, surface features, and lava flow hydrological functionings. Investigations of $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ13CTDIC (total dissolved inorganic carbon) on various spatiotemporal scales in the unsaturated and saturated zones of volcanic flows of the Argnat basin (French Massif Central) have been carried out to identify the carbon sources in the system. Mantellic sources are related to faults promoting CO2 uplift from the mantle to the saturated zone. The contribution of this source is counterbalanced by infiltration of water through the unsaturated zone, accompanied by dissolution of soil CO2 or even atmospheric CO2 during cold periods. Monitoring and modeling of δ13CTDIC in the unsaturated zone shows that both $ {\text{P}}_{{{\text{CO}}_{ 2} {\text{eq}}}} $ and δ13CTDIC are controlled by air temperature which influences soil respiration and soil-atmosphere CO2 exchanges. The internal geometry of volcanic lava flows controls water patterns from the unsaturated zone to saturated zone and thus may explain δ13C heterogeneity in the saturated zone at the basin scale. 相似文献
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T. Appourchaux K. Belkacem A.-M. Broomhall W. J. Chaplin D. O. Gough G. Houdek J. Provost F. Baudin P. Boumier Y. Elsworth R. A. García B. N. Andersen W. Finsterle C. Fröhlich A. Gabriel G. Grec A. Jiménez A. Kosovichev T. Sekii T. Toutain S. Turck-Chièze 《Astronomy and Astrophysics Review》2010,18(1-2):197-277
Solar gravity modes (or g modes)—oscillations of the solar interior on which buoyancy acts as the restoring force—have the potential to provide unprecedented inference on the structure and dynamics of the solar core, inference that is not possible with the well-observed acoustic modes (or p modes). The relative high amplitude of the g-mode eigenfunctions in the core and the evanesence of the modes in the convection zone make the modes particularly sensitive to the physical and dynamical conditions in the core. Owing to the existence of the convection zone, the g modes have very low amplitudes at photospheric levels, which makes the modes extremely hard to detect. In this article, we review the current state of play regarding attempts to detect g modes. We review the theory of g modes, including theoretical estimation of the g-mode frequencies, amplitudes and damping rates. Then we go on to discuss the techniques that have been used to try to detect g modes. We review results in the literature, and finish by looking to the future, and the potential advances that can be made—from both data and data-analysis perspectives—to give unambiguous detections of individual g modes. The review ends by concluding that, at the time of writing, there is indeed a consensus amongst the authors that there is currently no undisputed detection of solar g modes. 相似文献
156.
Olivier Morissette Frédéric Lecomte Guy Verreault Michel Legault Pascal Sirois 《Estuaries and Coasts》2016,39(2):571-582
Migratory contingents, groups of individuals belonging to the same population that adopt different migratory patterns, have been identified in numerous Striped Bass (Morone saxatilis) populations along North American East Coast. We tested the hypothesis that migratory contingents may develop early in life to maximize the exploitation of the variety of habitats faced by a recently introduced fish population. Using the discriminatory power provided by otolith chemistry, we studied early-life history stages of Striped Bass in a recently reintroduced population in the St. Lawrence Estuary. Migratory patterns were inferred using multivariate analysis of four otolith trace elements (Sr, Ba, Mn, and Mg) on juveniles (0+ and 1+). Three migratory contingents were identified during early-life history stages: freshwater residents, oligohaline migrants, and mesohaline migrants. This study demonstrates the rapid establishment, in less than 10 years since initial stocking, of three migratory contingents initiated early in life among the St. Lawrence Striped Bass population. We postulate that diversification provided by the establishment of distinct migratory contingents among early-life history stages promotes the rapid colonization of new environments through the exploration and exploitation of an increased number of nursery habitats. 相似文献
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Human thermal perception is best described through thermal indices. The most popular thermal indices applied in human bioclimatology are the perceived temperature (PT), the Universal Thermal Climate Index (UTCI), and the physiologically equivalent temperature (PET). They are analysed focusing on their sensitivity to single meteorological input parameters under the hot and windy meteorological conditions observed in Doha, Qatar. It can be noted, that the results for the three indices are distributed quite differently. Furthermore, they respond quite differently to modifications in the input conditions. All of them show particular limitations and shortcomings that have to be considered and discussed. While the results for PT are unevenly distributed, UTCI shows limitations concerning the input data accepted. PET seems to respond insufficiently to changes in vapour pressure. The indices should therefore be improved to be valid for several kinds of climates. 相似文献
160.
Dieudonné Bitom Boris Volkoff Anicet Beauvais Frédérique Seyler Paul-Désiré Ndjigui 《Comptes Rendus Geoscience》2004,336(13):1161-1170
Analysis of landscapes and soil covers from the outer to the inner part of a watershed in the South-Cameroon rainforest zone, characterized by important remnants of inherited ferricretes and stable hydrostatic base levels, indicates that the development of present landforms has not involved significant erosion by slope retreat because of the relative preservation of downslope residual ferricrete and that soil covers have vertically decayed under in situ geochemical process. To cite this article: D. Bitom et al., C. R. Geoscience 336 (2004). 相似文献