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31.
A Framework and Software Tool to Support Collaborative Landscape Analysis: Fitting Square Pegs into Square Holes 总被引:2,自引:0,他引:2
For landscape models to be applied successfully in management situations, models must address appropriate questions, include relevant processes and interactions, be perceived as credible and involve people affected by decisions. We propose a framework for collaborative model building that can address these issues, and has its roots in adaptive management, computer‐supported collaborative work and landscape ecology. Models built through this framework integrate a variety of information sources, address relevant questions, and are customized for the particular landscape and policy environment under study. Participants are involved in the process from the start, and because their input is incorporated, they feel ownership of the resulting models, increasing the chance of model acceptance and application. There are two requirements for success: a tool that supports rapid model prototyping and modification, that makes a clear link between a conceptual and implemented model, and that has the ability to implement a wide range of model types; and a core team with skills in communication, research and analysis, and knowledge of ecology and forestry in addition to modelling. SELES (Spatially Explicit Landscape Event Simulator) is a tool for building and running models of landscape dynamics. It combines discrete event simulation with a spatial database and a relatively simple modelling language to allow rapid development of landscape simulations, and provides a high‐level means of specifying complex model behaviours ranging from management actions to natural disturbance and succession. We have applied our framework in several forest modelling projects in British Columbia, Canada. We have found that this framework increases the interest by local experts and decision‐makers to participate actively in the model building process. The workshop process and resulting models have efficiently provided insight into the dynamics of large landscapes over long time frames. The use of SELES has facilitated this process by providing a flexible, transparent environment in which models can be rapidly implemented and refined. As a result, model findings may be more readily incorporated into decision‐support systems designed to assist resource managers in making informed decisions. 相似文献
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Olivier J. Hardy Céline Born Katarina Budde Kasso Daïnou Gilles Dauby Jérôme Duminil Eben-Ezer B.K. Ewédjé Céline Gomez Myriam Heuertz Guillaume K. Koffi Andrew J. Lowe Claire Micheneau Dyana Ndiade-Bourobou Rosalía Piñeiro Valérie Poncet 《Comptes Rendus Geoscience》2013,345(7-8):284-296
The biogeographic history of the African rain forests has been contentious. Phylogeography, the study of the geographic distribution of genetic lineages within species, can highlight the signatures of historical events affecting the demography and distribution of species (i.e. population fragmentation or size changes, range expansion/contraction) and, thereby, the ecosystems they belong to. The accumulation of recent data for African rain forests now enables a first biogeographic synthesis for the region. In this review, we explain which phylogeographic patterns are expected under different scenarios of past demographic change, and we give an overview of the patterns detected in African rain forest trees to discuss whether they support alternative hypotheses regarding the history of the African rain forest cover. The major genetic discontinuities in the region support the role of refugia during climatic oscillations, though not necessarily following the classically proposed scenarios. We identify in particular a genetic split between the North and the South of the Lower Guinean region. Finally we provide some perspectives for future study. 相似文献
35.
Andrew D. Czaja Anatoliy B. Kudryavtsev George D. Cody J. William Schopf 《Organic Geochemistry》2009,40(3):353-364
The processes of organic maturation that occur during the permineralization of fossils and the detailed chemistry of the resulting products are incompletely understood. Primary among such processes is the geochemical alteration of biological matter to produce kerogen, such as that which comprises the cell walls of the fossils studied here: essentially unmetamorphosed, Eocene plant axes (specimens of the fossil fern Dennstaedtiopsis aerenchymata cellularly permineralized in cherts of the Clarno Formation of Oregon and the Allenby Formation of British Columbia). The composition and molecular structure of the kerogen that comprises the cell walls of such axes were analyzed using ultraviolet Raman spectroscopy (UV–Raman), solid state 13C nuclear magnetic resonance spectroscopy (13C NMR) and pyrolysis–gas chromatography–mass spectrometry (py–GC–MS).Cellularly well-preserved fern axes from both geologic units exhibit similar overall molecular structure, being composed primarily of networks of aromatic rings and polyene chains that, unlike more mature kerogens, lack large polycyclic aromatic hydrocarbon (PAH) constituents. The cell walls of the Allenby Formation specimens are, however, less altered than those of the Clarno chert, exhibiting more prevalent oxygen-containing and alkyl functional groups and comprising a greater fraction of rock mass.The study represents the first demonstration of the effectiveness (and limitations) of the combined use of UV–Raman, 13C NMR and py–GC–MS for the analysis of the kerogenous cell walls of chert-permineralized vascular plants. 相似文献
36.
Levke Kp Kazuhide Nagashima Andrew M. Davis Alexander N. Krot 《Meteoritics & planetary science》2020,55(3):524-534
NASA's Genesis mission revealed that the Sun is enriched in 16O compared to the Earth and Mars (the Sun's Δ17O, defined as δ17O–0.52×δ18O, is –28.4 ± 3.6‰; McKeegan et al. 2011). Materials as 16O‐rich as the Sun are extremely rare in the meteorite record. Here, we describe a Ca‐Al‐rich inclusion (CAI) from a CM chondrite that is as 16O‐enriched as the Sun (Δ17O = –29.1 ± 0.7‰). This CAI also has large nucleosynthetic anomalies in 48Ca and 50Ti (δ‐values are –8.1 ± 3.3 and –11.7 ± 2.4‰, respectively) and shows no clear evidence for incorporation of live 26Al; (26Al/27Al)0 = (0.03 ± 0.11) × 10–5. Due to their anomalous isotopic characteristics, the rare CAIs consistent with the Genesis value could be among the first materials that formed in the solar system. In contrast to the CAI studied here, the majority of CAIs formed in or interacted with a reservoir characterized by a Δ17O value near –23.5‰. Combined with 26Al‐26Mg systematics, the oxygen isotopic compositions of FUN (fractionation and unidentified nuclear effects), UN, and normal CAIs suggest that nebular conditions were favorable for solids to inherit this value for an extended period of time. Many later‐formed materials, such as chondrules, planetesimals, and terrestrial planets, formed in reservoirs with Δ17O near 0‰. The distribution could be easier to explain if the common CAI value of –23.5‰, which is consistent with the Genesis value within 3σ, represented the average composition of the protoplanetary disk. 相似文献
37.
Andrew W. Beck Timothy J. McCoy Jessica M. Sunshine Christina E. Viviano Catherine M. Corrigan Takahiro Hiroi Rhiannon G. Mayne 《Meteoritics & planetary science》2013,48(11):2155-2165
Identifying and mapping olivine on asteroid 4 Vesta are important components to understanding differentiation on that body, which is one of the objectives of the Dawn mission. Harzburgitic diogenites are the main olivine‐bearing lithology in the howardite‐eucrite‐diogenite (HED) meteorites, a group of samples thought to originate from Vesta. Here, we examine all the Antarctic harzburgites and estimate that, on scales resolvable by Dawn, olivine abundances in putative harzburgite exposures on the surface of Vesta are likely at best in the 10–30% range, but probably lower due to impact mixing. We examine the visible/near‐infrared spectra of two harzburgitic diogenites representative of the 10–30% olivine range and demonstrate that they are spectrally indistinguishable from orthopyroxenitic diogenites, the dominant diogenitic lithology in the HED group. This suggests that the visible/near‐infrared spectrometer onboard Dawn (VIR) will be unable to resolve harzburgites from orthopyroxenites on the surface of Vesta, which may explain the current lack of identification of harzburgitic diogenite on Vesta. 相似文献
38.
Jan Mangerud Valery I. Astakhov Andrew Murray John Inge Svendsen 《Global and Planetary Change》2001,31(1-4)
Beach and shoreface sediments deposited in the more than 800-km long ice-dammed Lake Komi in northern European Russia have been investigated and dated. The lake flooded the lowland areas between the Barents–Kara Ice Sheet in the north and the continental drainage divide in the south. Shoreline facies have been dated by 18 optical stimulated luminescence (OSL) dates, most of which are closely grouped in the range 80–100 ka, with a mean of 88±3 ka. This implies that that the Barents–Kara Ice Sheet had its Late Pleistocene maximum extension during the Early Weichselian, probably in the cold interval (Rederstall) between the Brørup and Odderade interstadials of western Europe, correlated with marine isotope stage 5b. This is in strong contrast to the Scandinavian and North American ice sheets, which had their maxima in isotope stage 2, about 20 ka. Field and air photo interpretations suggest that Lake Komi was dammed by the ice advance, which formed the Harbei–Harmon–Sopkay Moraines. These has earlier been correlated with the Markhida moraine across the Pechora River Valley and its western extension. However, OSL dates on fluvial sediments below the Markhida moraine have yielded ages as young as 60 ka. This suggests that the Russian mainland was inundated by two major ice sheet advances from the Barents–Kara seas after the last interglacial: one during the Early Weichselian (about 90 ka) that dammed Lake Komi and one during the Middle Weichselian (about 60 ka). Normal fluvial drainage prevailed during the Late Weichselian, when the ice front was located offshore. 相似文献
39.
Hypothesis of possible superconductivity of the iced matter of the rings of Saturn (based on the data of Voyager and Pioneer
space missions) allow us to explain many phenomena which have not been adequately understood earlier. Introducing into planetary
physics force of magnetic levitation of the superconducting iced particle of the rings, which interact with magnetosphere
of the planet, becomes to be possible to explain origin, evolution, and dynamics of the rings; to show how the consequent
precipitation of the rings’ matter upon the planet was concluded; how the rings began their rotation; how they were compressed
by the magnetic field into the thin disc, and how this disc was fractured into hundreds of thousands of separated rings; why
in the ring B do exist “spokes”; why magnetic field lines have distortion near by ring F; why there is a variable azimuth brightness of the ring A; why the rings reflected radio waves so efficiently; why exists strong electromagnetic radiation of the rings in the 20.4
kHz–40.2 MHz range and Saturnian kilometric radiation; why there is anomalous reflection of circularly polarized microwaves;
why there are spectral anomalies of the thermal radiation of the rings; why the matter of the various rings does not mix but
preserves its small-scale color differences; why there is an atmosphere of unknown origin nearby the rings of Saturn; why
there are waves of density and bending waves within Saturn’s rings; why planetary rings in the solar system appear only after
the Belt of Asteroids (and may be the Belt of Asteroids itself is a ring for the Sun); why our planet Earth has no rings of
its own. 相似文献
40.
Richard P. Binzel Andrew S. Rivkin Cristina A. Thomas Pierre Vernazza Thomas H. Burbine Francesca E. DeMeo Schelte J. Bus Alan T. Tokunaga Mirel Birlan 《Icarus》2009,200(2):480-485
The known close approach of Asteroid (99942) Apophis in April 2029 provides the opportunity for the case study of a potentially hazardous asteroid in advance of its encounter. The visible to near-infrared (0.55 to 2.45 μm) reflectance spectrum of Apophis is compared and modeled with respect to the spectral and mineralogical characteristics of likely meteorite analogs. Apophis is found to be an Sq-class asteroid that most closely resembles LL ordinary chondrite meteorites in terms of spectral characteristics and interpreted olivine and pyroxene abundances, although we cannot rule out some degree of partial melting. A meteorite analog allows some estimates and conjectures of Apophis' possible range of physical properties such as the grain density and micro-porosity of its constituent material. Composition and size similarities of Apophis with (25143) Itokawa suggest a total porosity of 40% as a “current best guess” for Apophis. Applying these parameters to Apophis yields a mass estimate of 2×1010 kg with a corresponding energy estimate of 375 Mt for its potential hazard. Substantial unknowns, most notably the total porosity, allow uncertainties in these mass and energy estimates to be as large as factors of two or three. 相似文献