Preference for Grassland Heterogeneity: Implications for Biodiversity in the Great Plains     

Terrie A. Becerra  David M. Engle  Samuel D. Fuhlendorf  R. Dwayne Elmore 《社会与自然资源》2017,30(5):601-612

The Great Plains of the United States is a grassland region managed primarily for homogeneity associated with production agriculture. The resulting decline of obligate fauna makes enhancing biodiversity an increasingly important ecological goal. A survey was administered to land managers and the general population in ranching regions of Nebraska, Kansas, Oklahoma, and the Texas Panhandle. This research explores the preferred characteristics of privately owned grasslands among ranchers and the general population for vegetation structure and biodiversity. Results indicate a knowledge gap between biodiversity and the vegetation heterogeneity required to support it. Preference for grassland structure is seen as a sociocultural driver of decisions on management practices that constrain adoption of heterogeneity management. Conserving biodiversity and enhancing ecosystem services provided by heterogeneous grasslands can be accomplished by demonstrating that conservation advantages of heterogeneity and production agriculture are compatible.  相似文献   

The Pedagogical Benefits of Participatory GIS for Geographic Education     

Gaurav Sinha  Thomas A. Smucker  Eric J. Lovell  Kgosietsile Velempini  Samuel A. Miller  Daniel Weiner 《The Journal of geography》2017,116(4):165-179

In this article, participatory GIS (PGIS) is explored and established as a powerful platform for geographic education. PGIS pedagogy can help educators meet diverse learning objectives pertaining to: (1) local knowledge and place-based thinking; (2) community engagement; (3) field mapping with geospatial technologies; (4) mixed-methods research; and (5) fostering of critical reflexivity in students. The discussion is supported with insights from multiple student-facilitated PGIS projects organized in rural Tanzania. There also is a thorough discussion of the challenges and caveats associated with involving students in PGIS projects, and a call for new research for assessing and advancing PGIS pedagogy.  相似文献   

Erratum to: Combined effect of pulse density and grid cell size on predicting and mapping aboveground carbon in fast-growing Eucalyptus forest plantation using airborne LiDAR data     

Carlos Alberto Silva  Andrew Thomas Hudak  Carine Klauberg  Lee Alexandre Vierling  Carlos Gonzalez-Benecke  Samuel de Padua Chaves Carvalho  Luiz Carlos Estraviz Rodriguez  Adrián Cardil 《Carbon balance and management》2017,12(1):14

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Modelling future lahars controlled by different volcanic eruption scenarios at Cotopaxi (Ecuador) calibrated with the massively destructive 1877 lahar     

Theresa Frimberger  S. Daniel Andrade  Samuel Weber  Michael Krautblatter 《地球表面变化过程与地形》2021,46(3):680-700

Lahars are among the most hazardous mass flow processes on earth and have caused up to 23 000 casualties in single events in the recent past. The Cotopaxi volcano, 60 km southeast of Quito, has a well-documented history of massively destructive lahars and is a hotspot for future lahars due to (i) its ~10 km² glacier cap, (ii) its 117–147-year return period of (Sub)-Plinian eruptions, and (iii) the densely populated potential inundation zones (300 000 inhabitants). Previous mechanical lahar models often do not (i) capture the steep initial lahar trajectory, (ii) reproduce multiple flow paths including bifurcation and confluence, and (iii) generate appropriate key parameters like flow speed and pressure at the base as a measure of erosion capacity. Here, we back-calculate the well-documented 1877 lahar using the RAMMS debris flow model with an implemented entrainment algorithm, covering the entire lahar path from the volcano edifice to an extent of ~70 km from the source. To evaluate the sensitivity and to constrain the model input range, we systematically explore input parameter values, especially the Voellmy–Salm friction coefficients μ and ξ. Objective selection of the most likely parameter combinations enables a realistic and robust lahar hazard representation. Detailed historic records for flow height, flow velocity, peak discharge, travel time and inundation limits match best with a very low Coulomb-type friction μ (0.0025–0.005) and a high turbulent friction ξ (1000–1400 m/s²). Finally, we apply the calibrated model to future eruption scenarios (Volcanic Explosivity Index = 2–3, 3–4, >4) at Cotopaxi and accordingly scaled lahars. For the first time, we anticipate a potential volume growth of 50–400% due to lahar erosivity on steep volcano flanks. Here we develop a generic Voellmy–Salm approach across different scales of high-magnitude lahars and show how it can be used to anticipate future syneruptive lahars.  相似文献   

SPECTRAL SIGNATURE OF COUPLED FLOW IN THE REFREEZING ACTIVE LAYER,NORTHERN ALASKA     

Samuel I. Outcalt  Kenneth M. Hinkel  Frederick E. Nelson 《自然地理学》2013,34(3):273-284

Soil temperature records obtained from the active layer above permafrost at a site in northern Alaska during autumn and winter have variance spectra inconsistent with a purely conductive heat-transfer system. Although conductive heat-transfer theory predicts that temperature fluctuations are attenuated with depth, sub-diurnal thermal variance at the 50-cm level, near the base of the active layer, exceeded that at the 10-cm level. Short segments of the temperature record were drawn from three distinct periods of soil-frost conditions: (1) at the maximum vertical development of the active layer in early autumn; (2) during frost penetration and the formation of a zero curtain in early winter; and (3) after freezeback of the active layer. The variance spectra of these time series show systematic seasonal transitions that reflect changing mechanisms of heat transfer. During the first and second periods, heat transfer by internal evaporation and condensation dominates at wavelengths in the diurnal range. The spectral traces are not strongly self-similar and the fractal dimensions indicate extreme space-filling, especially at deeper levels. Once the active layer is frozen, conductive heat transfer dominates, producing a trend toward self-similarity. Both the thermal variance and the fractal dimension decrease with depth in the frozen regime. [Key words: Alaska, active layer, coupled flow, fractal dimension, frozen ground, heat transfer, permafrost, soil freezing, spectral analysis, zero curtain.]  相似文献   

A method for discovery and analysis of temporal patterns in complex event data     

Donna J. Peuquet  Anthony C. Robinson  Samuel Stehle  Franklin A. Hardisty  Wei Luo 《International journal of geographical information science》2013,27(9):1588-1611

Pattern analysis techniques currently common within geography tend to focus either on characterizing patterns of spatial and/or temporal recurrence of a single event type (e.g., incidence of flu cases) or on comparing sequences of a limited number of event types where relationships between events are already represented in the data (e.g., movement patterns). The availability of large amounts of multivariate spatiotemporal data, however, requires new methods for pattern analysis. Here, we present a technique for finding associations among many different event types where the associations among these varying event types are not explicitly represented in the data or known in advance. This pattern discovery method, known as T-pattern analysis, was first developed within the field of psychology for the purpose of finding patterns in personal interactions. We have adapted and extended the T-pattern method to take the unique characteristics of geographic data into account and implemented it within a geovisualization toolkit for an integrated computational-geovisual environment we call STempo. To demonstrate how T-pattern analysis can be employed in geographic research for discovering patterns in complex spatiotemporal data, we describe a case study featuring events from news reports about Yemen during the Arab Spring of 2011–2012. Using supplementary data from the Global Database of Events, Language, and Tone, we briefly summarize and reference a separate validation study, then evaluate the scalability of the T-pattern approach. We conclude with ideas for further extensions of the T-pattern technique to increase its utility for spatiotemporal analysis.  相似文献   

Damped Lyman α systems and disc galaxies: number density, column density distribution and gas density     

Samuel Boissier  Céline Péroux  Max Pettini 《Monthly notices of the Royal Astronomical Society》2003,338(1):131-140

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Shear and vorticity in inflationary Brans–Dicke cosmology with lambda-term     

Marcelo Samuel Berman 《Astrophysics and Space Science》2007,310(3-4):205-207

We find a solution for exponential inflation in Brans–Dicke cosmology endowed with a cosmological term, which includes time-varying shear and vorticity. We find that the scalar field and the scale factor increase exponentialy while shear, vorticity, energy density, cosmic pressure and the cosmological term decay exponentialy for negative beta, where beta is defined in the text.  相似文献   

The link between volcanism and plutonism in epizonal magma systems; high-precision U–Pb zircon geochronology from the Organ Mountains caldera and batholith,New Mexico     

Matthew Rioux  G. Lang Farmer  Samuel A. Bowring  Kathleen M. Wooton  Jeffrey M. Amato  Drew S. Coleman  Philip L. Verplanck 《Contributions to Mineralogy and Petrology》2016,171(2):13

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Oxygen isotope record of oceanic and high-pressure metasomatism: a P–T–time–fluid path for the Monviso eclogites (Italy)     

Daniela Rubatto  Samuel Angiboust 《Contributions to Mineralogy and Petrology》2015,170(5-6):1-16

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