Optimal water depth management on river-fed National Wildlife Refuges in a changing climate     

Sam Nicol  Brad Griffith  Jane Austin  Christine M. Hunter 《Climatic change》2014,124(1-2):271-284

The prairie pothole region (PPR) in the north-central United States and south-central Canada constitutes the most important waterfowl breeding area in North America. Projected long-term changes in precipitation and temperature may alter the drivers of waterfowl abundance: wetland availability and emergent vegetation cover. Previous studies have focused on isolated wetland dynamics, but the implications of changing precipitation on managed, river-fed wetlands have not been addressed. Using a structured decision making (SDM) approach, we derived optimal water management actions for 20 years at four river-fed National Wildlife Refuges (NWRs) in North and South Dakota under contrasting increasing/decreasing (+/?0.4 %/year) inflow scenarios derived from empirical trends. Refuge pool depth is manipulated by control structures. Optimal management involves setting control structure heights that have the highest probability of providing a desired mix of waterfowl habitat, given refuge capacities and inflows. We found optimal seasonal control structure heights for each refuge were essentially the same under increasing and decreasing inflow trends of 0.4 %/year over the next 20 years. Results suggest managed pools in the NWRs receive large inflows relative to their capacities. Hence, water availability does not constrain management; pool bathymetry and management tactics can be greater constraints on attaining management objectives than climate-mediated inflow. We present time-dependent optimal seasonal control structure heights for each refuge, which are resilient to the non-stationary precipitation scenarios we examined. Managers can use this information to provide a desired mixture of wildlife habitats, and to re-assess management objectives in reserves where pool bathymetry prevents attaining the currently stated objectives.  相似文献   

Instruments, Detectors and the Future of Astronomy with Large Ground Based Telescopes     

Douglas A. Simons  Paola Amico  Dietrich Baade  Sam Barden  Randall Campbell  Gert Finger  Kirk Gilmore  Roland Gredel  Paul Hickson  Steve Howell  Norbert Hubin  Andreas Kaufer  Ralf Kohley  Philip MacQueen  Sergej Markelov  Mike Merrill  Satoshi Miyazaki  Hidehiko Nakaya  Darragh O'Donoghue  Tino Oliva  Andrea Richichi  Derrick Salmon  Ricardo Schmidt  Hongjun Su  Simon Tulloch  Maria Luisa García Vargas  R. Mark Wagner  Olivier Wiecha  Binxun Ye 《Experimental Astronomy》2005,19(1-3):15-44

Results of a survey of instrumentation and detector systems, either currently deployed or planned for use at telescopes larger than 3.5 m, in ground based observatories world-wide, are presented. This survey revealed a number of instrumentation design trends at optical, near, and mid-infrared wavelengths. Some of the most prominent trends include the development of vastly larger optical detector systems (> 10⁹ pixels) than anything built to date, and the frequent use of mosaics of near-infrared detectors – something that was quite rare only a decade ago in astronomy. Some future science applications for detectors are then explored, in an attempt to build a bridge between current detectors and what will be needed to support the research ambitions of astronomers in the future.  相似文献   

On the Centre Manifold of Collinear Points in the Planar Three-Body Problem     

Regina Martínez  Anna Samà 《Celestial Mechanics and Dynamical Astronomy》2003,85(4):311-340

We study the existence of invariant tori in a neighbourhood of the collinear equilibrium points of the planar three-body problem. To this end some properties of the normal form of the Hamiltonian reduced to the 4D central manifold are proved. Using this normal form, we show that the nondegeneracy conditions of KAM theorem are satisfied for all positive masses, including the 2:1 resonance case. The evaluation of the conditions is done numerically.  相似文献   

The WISERD Geoportal: A Tool for the Discovery,Analysis and Visualization of Socio‐economic (Meta‐) Data for Wales     

Richard Fry  Robert Berry  Gary Higgs  Scott Orford  Sam Jones 《Transactions in GIS》2012,16(2):105-124

  相似文献   

The Jurassic Coast Story Book: An approach to geoheritage interpretation from the Jurassic Coast World Heritage Site     

Sam Scriven 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(3-4):493-506

The World Heritage status of the Jurassic Coast has important implications for how the geoheritage of the site is communicated to audiences. UNESCO defines World Heritage Sites as places with Outstanding Universal Value to all people that must be preserved for future generations. Building relationships between people and place is key to conservation and on the Jurassic Coast that is delivered by providing audiences with physical, intellectual and emotional access to the Site. Heritage interpretation offers an effective way to develop these connections and create diverse ways for people to engage with the unique Earth Science stories that underpin the World Heritage Status of the Dorset and East Devon Coast. This paper reflects on the approach to interpretation taken by the Jurassic Coast Team and explores the ways in which geoheritage is a challenging subject to interpret. Practitioners on the Jurassic Coast have more recently developed an interpretive approach to help overcome these difficulties. Three categories of geoheritage stories were identified (Landscape, Cultural geology and Earth History) and three interpretive principles were devised (perspective, intimacy and imagination) as a way of scoping out a relevant emotional context for interpretive content. This approach laid the foundation for the development of a new interpretation framework for the Jurassic Coast – The Jurassic Coast Story Book, which will be subject to ongoing testing and evaluation by the new organisation leading on the protection and promotion of the Jurassic Coast World Heritage Site; Jurassic Coast Trust.  相似文献   

Estuarine biofilm patterns: Modern analogues for Precambrian self-organization     

Roeland C. van de Vijsel  Jim van Belzen  Tjeerd J. Bouma  Daphne van der Wal  Valentina Cusseddu  Sam J. Purkis  Max Rietkerk  Johan van de Koppel 《地球表面变化过程与地形》2020,45(5):1141-1154

This field and laboratory study examines whether regularly patterned biofilms on present-day intertidal flats are equivalent to microbially induced bedforms found in geological records dating back to the onset of life on Earth. Algal mats of filamentous Vaucheria species, functionally similar to microbial biofilms, cover the topographic highs of regularly spaced ridge–runnel bedforms. As regular patterning is typically associated with self-organization processes, indicators of self-organization are tested and found to support this hypothesis. The measurements suggest that biofilm-induced sediment trapping and biostabilization enhance bedform relief, strength and multi-year persistence. This demonstrates the importance of primitive organisms for sedimentary landscape development. Algal-covered ridges consist of wavy-crinkly laminated sedimentary deposits that resemble the layered structure of fossil stromatolites and microbially induced sedimentary structures. In addition to layering, both the morphological pattern and the suggested formation mechanism of the recent bedforms are strikingly similar to microbialite strata found in rock records from the Precambrian onwards. This implies that self-organization was an important morphological process in times when biofilms were the predominant sessile ecosystem. These findings furthermore emphasize that self-organization dynamics, such as critical transitions invoking ecosystem emergence or collapse, might have been captured in fossil microbialites, influencing their laminae. This notion may be important for paleoenvironmental reconstructions based on such strata. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Grain‐size distributions on high‐energy sandy beaches and their relation to wave dissipation          下载免费PDF全文

Sam Prodger  Paul Russell  Mark Davidson 《Sedimentology》2017,64(5):1289-1302

Grain size and sorting represent two key parameters when characterizing sediments or modelling beach morphology and sediment transport. Traditionally, an average value for grain size or sorting is often assumed for the entire area, determined from only a few sediment samples, ignoring any spatial (or temporal) variability in sediment characteristics. This contribution uses a data set of physical surface sediment samples from 53 beach locations around the south‐west peninsula of the United Kingdom, in addition to bi‐monthly, high spatial resolution (mean 240 samples) digital grain‐size surveys from a high‐energy, oceanic, sandy beach (Perranporth, North Cornwall). Systematic spatial variations in grain size and sorting were consistently observed in the seaward direction across the intertidal zone of sandy beaches, with grain‐sizes coarsening and sorting improving by up to 51·7% and 64·3%, respectively. This variability was deterministically related to the time‐averaged, antecedent‐adjusted energy dissipated by breaking waves, with the observed maximum grain‐size and sorting values correlating with the location of peak wave energy dissipation (r² = 0·998, P < 0·01).  相似文献   

Tephra dispersal during the Campanian Ignimbrite (Italy) eruption: implications for ultra-distal ash transport during the large caldera-forming eruption     

Victoria C. Smith  Roberto Isaia  Sam L. Engwell  Paul. G. Albert 《Bulletin of Volcanology》2016,78(6):45

  相似文献   

Role of Subsurface Brines in Salt Balance: The Case Study of the Caspian Sea and Kara Bogaz Bay     

Norbert Clauer  Marie-Claire Pierret  Sam Chaudhuri 《Aquatic Geochemistry》2009,15(1-2):237-261

The water level of the Caspian Sea fluctuated significantly during recent history, without consensus for the cause. The varied chemistry of the Caspian, Kara Bogaz and sediment a interstitial waters provides a further insight. Element concentrations and ⁸⁷Sr/⁸⁶Sr ratios of the interstitial waters were compared to those of Caspian and Kara Bogaz open waters, and of acid-leached extractable components. The ⁸⁷Sr/⁸⁶Sr ratios of the interstitial waters are explained by addition of subterranean waters similar to nearby spring waters. These subterranean waters yield chemical characteristics such as a Cl/SO₄, ⁸⁷Sr/⁸⁶Sr, Ca/Sr and K/Rb ratios of respectively 80, 0.7086, 250 and 1,800. However, their addition does not explain the large difference in the K/Rb ratio of the Caspian and Kara Bogaz waters, respectively at 7,630 and 17,550, which implies also a leaching of salt deposits by the upward migrating subterranean waters. The sediments of the southern Caspian basin, with low Na, Cl and SO₄ in their interstitial waters, deposited apparently in an anoxic environment. The related chemical changes in the waters are also indicative of a recent change in the hydrologic regime, possibly induced by a changing morphology of the drainage basin.  相似文献   

TWO ELECTRIC POTENTIAL SIGNATURES OF SERIAL DIURNAL FROST     

Sam I. Outcalt  Donald H. Gray 《自然地理学》2013,34(4):354-360

During a 96-hour period in mid-March 1987, a series of four serial frost-thaw events occurred in a research field at the University of Michigan Matthaei Botanical Gardens. Soil temperature and electric potential were recorded at two near surface probe arrays (0, 3, 6 & 9 cm) and (0, 5, 10 & 15 cm) with a horizontal separation of approximately 1 m beneath the organic-mineral soil interface at hourly intervals. These time series revealed strong repetitive serial patterns. When the electric potential measurements were converted to a surrogate measure of electrolyte concentration, the C-index, strong coupled flow effects appeared to be present in the time series owing to the effects of surface freeze-thaw, evaporation-distillation and soil water advection.

The data set shows the low frequency effects of upward soil water advection increasing the soil temperature and modulating the electrolyte concentration. These observations also demonstrate that soil freezing processes have two distinct regimes dominated by (1) early soil water advection toward the frost front from below and (2) downward expulsion of electrolyte-rich water as ice fills the pore space. These two processes of soil water advection and expulsion augmented by local evaporation produce two distinct near surface C-index signatures of serial diurnal frost. The signature depends on the direction of the vertical electrolyte gradient near the surface. [Key words: soil, frost-thaw, soil water, soil temperature.]  相似文献