Suitability of airborne laser scanning for the assessment of forest protection effect against rockfall     

Jean-Matthieu Monnet  Franck Bourrier  Sylvain Dupire  Frederic Berger 《Landslides》2017,14(1):299-310

Rockfall simulation models are now able to quantify the protective effect of forest with the integration of rock impacts on trees. Those models require spatially explicit forest characteristics which are costly to acquire in operational conditions. The present study compares rockfall simulation results obtained with different forest input data sources: field data with different levels of spatial detail and two methods based on airborne Lidar data. Three different forest stands are tested with several virtual terrain configurations. When rockfall energies are below 200 kJ, the forest protection effect is significant. For higher energies, it also exists but it is minor compared to the effects of topography and rock volume. For all forest input data sources, the estimated rockfall intensity is within ?13 and 16 % of the reference value, whereas the frequency is generally overestimated. Both Lidar methods yield a satisfactory forest protection effect evaluation, but single tree detection tends to underestimate it. Improvements are possible regarding the spatial heterogeneity of stem density and the diameter distribution by tree species.  相似文献   

The Use of Statistical Tools for Evaluating Computer Simulations – An Editorial Essay     

Richard A. Berk  Robert G. Fovell  Frederic Schoenberg  Robert E. Weiss 《Climatic change》2001,51(2):119-130

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Seasonal growth in the bivalveMacoma balthica near the southern limit of its range     

Frederic H. Nichols  Janet K. Thompson 《Estuaries and Coasts》1982,5(2):110-120

Shell-length growth inMacoma balthica from San Francisco Bay, California, as measured on living animalsin situ, is highly seasonal despite a mild Mediterranean climate: a long period of near non-growth from May to the following February is followed by a short period of rapid growth between March and May. The rapid-growth period follows the spawning period during January/February and ends as water temperature rises above about 15°C. Despite the shortness of the growth period,M. balthica grows larger at a given age in San Francisco Bay than is recorded elsewhere in the world. Application of a model, developed elsewhere from these same field measurements, shows that (1) measurable growth occurs during the summer/autumn/early winter “nongrowth” period, (2) there is an autumn recruitment, and (3) both spring and autumn recruits combine to form a single “one-year-old” size grouping. None of these features is detectable through growth-ring analysis of field samples, apparently because of indistinct climatic seasons, or through size-frequency histogram analysis because of the combined effects of slow growth and intermittent recruitment.  相似文献   

Stratigraphic responses to a major tectonic event in a foreland basin: the Ecuadorian Oriente Basin from Eocene to Oligocene times   总被引：2，自引：0，他引：2  

Frdric Christophoul  Patrice Baby  Celso Dvila 《Tectonophysics》2002,345(1-4)

The Eocene to Oligocene sediments of the Ecuadorian Oriente Basin record two kinds of second-order stratigraphic response to the tectonic evolution. Lower Eocene shows evidences of local scale syntectonic deposits. This tectonic activity can be related to right lateral convergent movements inverting pre-cretaceous extensional structures. Upper Eocene and Oligocene sediments are integrated as the expression of an isostatic rebound characterizing a basin scale syntectonic deposition. This response is evidenced by a reciprocal architecture of the depositional sequences identified in the sedimentary formations. These data have allowed us to propose a new geodynamic model for the Paleogene evolution of the Oriente Basin.  相似文献   

Interannual changes in recruitment of the Atlantic salmon (Salmo salar) population in the River Oir (Lower Normandy, France): relationships with spawners and in-stream habitat     

Bagliniere  Jean-Luc; Marchand  Frederic; Vauclin  Vincent 《ICES Journal of Marine Science》2005,62(4):695-707

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Introduction to the fundamental tables for the deflection of the vertical     

Frederic W. Darling 《Journal of Geodesy》1948,22(3):199-240

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Solar EUV/FUV irradiance variations: analysis and observational strategy     

Matthieu Kretzschmar  Thierry Dudok de Wit  Jean Lilensten  Jean-Francois Hochedez  Jean Aboudarham  Pierre-Olivier Amblard  Frederic Auchère  Said Moussaoui 《Acta Geophysica》2009,57(1):42-51

The knowledge of solar extreme and far ultraviolet (EUV) irradiance variations is essential for the characterization of the Earth’s upper atmosphere. For a long time, this knowledge has been based on empirical models, which are themselves based on proxies of the solar activity. However, the accurate modeling and prediction of the Earth’s upper atmosphere necessitate to improve the precision on the irradiance and its variations below about 200 nm. Here, we present a review of recent works made by the authors that aim at quantifying the irradiance variability at these wavelengths, and that lead to new way of monitoring the solar EUV/FUV irradiance spectrum. In more details, it is shown that the quantification of the high level of redundancy in the solar spectrum variability allows to envisage measuring only a small portion of the spectrum without losing essential knowledge. Finally, we discuss what should and could be measured in order to retrieve the solar extreme and far ultraviolet spectrum.  相似文献   

Al–Mg and Pb–Pb systematics of Allende CAIs: Canonical solar initial Al/Al ratio reinstated     

Benjamin Jacobsen  Qing-zhu Yin  Frederic Moynier  Yuri Amelin  Alexander N. Krot  Kazuhide Nagashima  Ian D. Hutcheon  Herbert Palme 《Earth and Planetary Science Letters》2008,272(1-2):353-364

The precise knowledge of the initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] is crucial if we are to use the very first solid objects formed in our Solar System, calcium–aluminum-rich inclusions (CAIs) as the “time zero” age-anchor and guide future work with other short-lived radio-chronometers in the early Solar System, as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation. New high-precision multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) measurements of ²⁷Al/²⁴Mg ratios and Mg-isotopic compositions of nine whole-rock CAIs (six mineralogically characterized fragments and three micro-drilled inclusions) from the CV carbonaceous chondrite, Allende yield a well-defined ²⁶Al–²⁶Mg fossil isochron with an (²⁶Al/²⁷Al)₀ of (5.23 ± 0.13) × 10^− 5. Internal mineral isochrons obtained for three of these CAIs (A44A, AJEF, and A43) are consistent with the whole-rock CAI isochron. The mineral isochron of AJEF with (²⁶Al/²⁷Al)₀ = (4.96 ± 0.25) × 10^− 5, anchored to our precisely determined absolute ²⁰⁷Pb–²⁰⁶Pb age of 4567.60 ± 0.36 Ma for the same mineral separates, reinstate the “canonical” (²⁶Al/²⁷Al)₀ of 5 × 10^− 5 for the early Solar System. The uncertainty in (²⁶Al/²⁷Al)₀ corresponds to a maximum time span of ± 20 Ka (thousand years), suggesting that the Allende CAI formation events were culminated within this time span. Although all Allende CAIs studied experienced multistage formation history, including melting and evaporation in the solar nebula and post-crystallization alteration likely on the asteroidal parent body, the ²⁶Al–²⁶Mg and U–Pb-isotopic systematics of the mineral separates and bulk CAIs behaved largely as closed-system since their formation. Our data do not support the “supra-canonical” ²⁶Al/²⁷Al ratio of individual minerals or their mixtures in CV CAIs, suggesting that the supra-canonical ²⁶Al/²⁷Al ratio in the CV CAIs may have resulted from post-crystallization inter-mineral redistribution of Mg isotopes within an individual inclusion. This redistribution must be volumetrically minor in order to satisfy the mass balance of the precisely defined bulk CAI and bulk mineral data obtained by MC-ICP-MS.The radiogenic ²⁰⁸Pb/²⁰⁶Pb ratio obtained as a by-product from the Pb–Pb age dating is used to estimate time-integrated ²³²Th/²³⁸U ratio (κ value) of CAIs. Limited κ variations among the minerals within a single CAI, contrasted by much larger variations among the bulk CAIs, suggest Th/U fractionation occurred prior to crystallization of igneous CAIs. If interpreted as primordial heterogeneity, the κ value can be used to calculate the mean age of the interstellar dust from which the CAIs condensed.  相似文献   

Voluminous lava flows at Oldoinyo Lengai in 2006: chronology of events and insights into the shallow magmatic system     

Matthieu Kervyn  Gerald G. J. Ernst  Jurgis Klaudius  Jörg Keller  François Kervyn  Hannes B. Mattsson  Frederic Belton  Evelyne Mbede  Patric Jacobs 《Bulletin of Volcanology》2008,70(9):1069-1086

The largest natrocarbonatite lava flow eruption ever documented at Oldoinyo Lengai, NW Tanzania, occurred from March 25 to April 5, 2006, in two main phases. It was associated with hornito collapse, rapid extrusion of lava covering a third of the crater and emplacement of a 3-km long compound rubbly pahoehoe to blocky aa-like flow on the W flank. The eruption was followed by rapid enlargement of a pit crater. The erupted natrocarbonatite lava has high silica content (3% SiO₂). The eruption chronology is reconstructed from eyewitness and news media reports and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, which provide the most reliable evidence to constrain the eruption’s onset and variations in activity. The eruption products were mapped in the field and the total erupted lava volume estimated at 9.2 ± 3.0 × 10⁵ m³. The event chronology and field evidence are consistent with vent construct instability causing magma mixing and rapid extrusion from shallow reservoirs. It provides new insights into and highlights the evolution of the shallow magmatic system at this unique natrocarbonatite volcano.  相似文献   

Geoarchaeology and prehistory of the Kipsing and Tol river watersheds in the Mukogodo Hills region of Central Kenya     

Frederic B. Pearl  D. Bruce Dickson 《Geoarchaeology》2004,19(6):565-582

An archaeological survey and geomorphological investigation were conducted over a period of three years in the Tol and Kipsing River valleys, both located in the Mukogodo Hills‐Upper Ewaso Ng'iro Plains region of Central Kenya. Eleven alluvial‐stratigraphic sections were studied, and five late‐Quaternary alluvial stratigraphic units were identified on the basis of lithology, chronology, and soil stratigraphy. The locations of 63 archaeological sites recorded during the reconnaissance were compared with the distribution of the alluvial units. These data were used to predict where sites of different cultural periods are most likely to be found and to determine the relationship between site location and alluvial deposition. Since natural processes of deposition and erosion do not fully account for the distribution of Middle and Later Stone Age sites in the study area, the hypothesis that these differences reflect human choices, not the operation of natural processes, cannot be rejected. © 2004 Wiley Periodicals, Inc.  相似文献