Distribution by Scientific Domains

Kinds of Ground

  • bare ground
  • breeding ground
  • clinical ground
  • common ground
  • economic ground
  • empirical ground
  • feeding ground
  • fertile ground
  • find common ground
  • fishing ground
  • foraging ground
  • good ground
  • methodological ground
  • middle ground
  • new ground
  • nursery ground
  • other ground
  • scientific ground
  • spawning ground
  • staging ground
  • sufficient ground
  • testing ground
  • theoretical ground
  • wintering ground

  • Terms modified by Ground

  • ground acceleration
  • ground area
  • ground beef
  • ground beef patty
  • ground beetle
  • ground chicken breast meat
  • ground condition
  • ground contact
  • ground cover
  • ground floor
  • ground investigation
  • ground layer
  • ground level
  • ground measurement
  • ground meat
  • ground motion
  • ground observation
  • ground pattern
  • ground penetrating radar
  • ground plan
  • ground plane
  • ground pork
  • ground reaction force
  • ground sample
  • ground section
  • ground squirrel
  • ground state
  • ground state energy
  • ground state transition
  • ground states
  • ground substance
  • ground surface
  • ground survey
  • ground temperature
  • ground theory
  • ground truth
  • ground truth data
  • ground vegetation
  • ground vehicle
  • ground water
  • ground water concentration
  • ground water contamination
  • ground water extraction
  • ground water flow
  • ground water flow model
  • ground water head
  • ground water level
  • ground water plume
  • ground water quality
  • ground water remediation
  • ground water resources
  • ground water sample
  • ground water system
  • ground water velocity

  • Selected Abstracts




    NEW BLACKFRIARS, Issue 1034 2010
    First page of article [source]


    RATIO, Issue 2 2009
    Axel Gelfert
    Local reductionism purports to defend a middle ground in the debate about the epistemic status of testimony-based beliefs. It does so by acknowledging the practical ineliminability of testimony as a source of knowledge, while insisting that such an acknowledgment need not entail a default-acceptance view, according to which there exists an irreducible warrant for accepting testimony. The present paper argues that local reductionism is unsuccessful in its attempt to steer a middle path between reductionism and anti-reductionism about testimonial justification. In particular, it challenges local reductionism ,from within', without appealing to anti-reductionist intuitions. By offering novel arguments to the effect that local reductionism fails by its own standards, the present paper considerably strengthens the case against this version of reductionism. Local reductionism, it is argued, fails for three main reasons. First, it cannot account for the rationality of testimonial rejection in paradigmatic cases, even though the possibility of rational rejection is thought to be of central justificatory importance. Second, it does not provide a sufficiently distinct non-testimonial basis to which testimonial justification can be successfully reduced. Finally, local reductionism is shown to be an intrinsically unstable position, in danger of collapsing into full-fledged ,credulism' of the kind historically associated with Thomas Reid. [source]


    Chrie A. Keller
    Abstract Standardized aerial surveys were used to document the winter (December,March) distribution of North Atlantic right whales in their calving area off the coasts of Georgia and northeastern Florida (1991,1998). Survey data were collected within four survey zones in and adjacent to federally designated critical habitat. These data, including whale-sighting locations and sampling effort, were used to describe right whale distribution in relation to sea-surface temperature (SST) from satellite-derived images. Locations where whales were sighted (n= 609) had an overall mean SST of 14.3C 2.1 (range 8,22C). Data from two survey zones having sufficient data (including the "early warning system" (EWS) zone and the Florida nearshore) were pooled by season and stratified by month to investigate changes in monthly ambient SST and fine-scale distribution patterns of right whales in relation to SST within spatially explicit search areas. Using Monte Carlo techniques, SSTs and latitudes (means and standard deviations) of locations where whales were sighted were compared to a sampling distribution of each variable derived from daily-search areas. Overall, results support a nonrandom distribution of right whales in relation to SST: during resident months (January and February), whales exhibited low variability in observed SST and a suggested southward shift in whale distribution toward warmer SSTs in the EWS zone; while in the relatively warmer and southernmost survey zone (Florida nearshore), right whales were concentrated in the northern, cooler portion. Our results support that warm Gulf Stream waters, generally found south and east of delineated critical habitat, represent a thermal limit for right whales and play an important role in their distribution within the calving grounds. These results affirm the inclusion of SST in a multivariate predictive model for right whale distribution in their southeastern habitat. [source]

    Closer to the Shifting Ground: The Rise of Relationship in God-Talk

    DIALOG, Issue 3 2005
    By Paul R. Sponheim
    Abstract:, The article argues that God-talk has changed significantly over the last fifty years and identifies the rise of the notion of relationship (reflecting postmodern dissatisfaction with modernity) as a key factor in this change. That factor is cited in Trinitarian studies, the Creator's relationship with and to the creatures, the science and religion conversation, the connection with context, and the increasing recognition of the adjectival character of theology. In closing the author looks ahead to further relational work in soteriology, anthropology and metaphysics. [source]

    Review of Policies and Guidelines on Infant Feeding in Emergencies: Common Ground and Gaps

    DISASTERS, Issue 2 2001
    Andrew Seal
    Recent crises in regions where exclusive breastfeeding is not the norm have highlighted the importance of effective policies and guidelines on infant feeding in emergencies. In 1993, UNICEF compiled a collection of policy and guideline documents relating to the feeding of infants in emergency situations. In June 2000 Save the Children, UK, UNICEF and the Institute of Child Health undertook a review of those documents, updating the list and identifying the common ground that exists among the different policies. The review also analysed the consistency of the policy framework, and highlighted important areas where guidelines are missing or unclear. This article is an attempt to share more widely the main issues arising from this review. The key conclusions were that, in general, there is consensus on what constitutes best practice in infant feeding, however, the lack of clarity in the respective responsibilities of key UN agencies (in particular UNICEF, UNHCR and WFP) over issues relating to co-ordination of activities which affect infant-feeding interventions constrains the implementation of systems to support best practice. Furthermore, the weak evidence base on effective and appropriate intervention strategies for supporting optimal infant feeding in emergencies means that there is poor understanding of the practical tasks needed to support mothers and minimise infant morbidity and mortality. We, therefore, have two key recommendations: first that the operational UN agencies, primarily UNICEF, examine the options for improving co-ordination on a range of activities to uphold best practice of infant feeding in emergencies; second, that urgent attention be given to developing and supporting operational research on the promotion of optimal infant-feeding interventions. [source]

    Ground motion duration effects on nonlinear seismic response

    Iunio Iervolino
    Abstract The study presented in this paper addresses the question of which nonlinear demand measures are sensitive to ground motion duration by statistical analyses of several case studies. A number of single degree of freedom (SDOF) structures were selected considering: (1) four oscillation periods; (2) three evolutionary and non-evolutionary hysteretic behaviours; (3) two target ductility levels. Effects of duration are investigated, by nonlinear dynamic analysis, with respect to six different demand indices ranging from displacement ductility ratio to equivalent number of cycles. Input is made of six real accelerogram sets representing three specific duration scenarios (small, moderate and large duration). For all considered demand quantities time-history results are formally compared by statistical hypothesis test to asses the difference, if any, in the demand concerning different scenarios. Incremental dynamic analysis curves are used to evaluate duration effect as function of ground motion intensity (e.g. spectral acceleration corresponding to the SDOF's oscillation period). Duration impact on structural failure probability is evaluated by fragility curves. The results lead to the conclusion that duration content of ground motion is statistically insignificant to displacement ductility and cyclic ductility demand. The conclusions hold regardless of SDOF's period and hysteretic relationship investigated. Copyright 2005 John Wiley & Sons, Ltd. [source]

    On Foreign Ground: One Attempt at Attracting Non-French Majors to a French Studies Course

    Article first published online: 31 DEC 200, Jean M. Fallon
    ABSTRACT: This article presents a description of "Americans in Paris," a class in English that was developed to attract nonlanguage majors to French Studies classes. The class focuses on American writers who lived and worked in Paris between 1890 and 1955 as part of a literary and cultural exchange between French and American societies. Learning about French writers and the dynamic, international community of writers and artists who came to Paris in the early twentieth century, students come to understand the literary and cultural heritages that were passed between France and America. The course's content showcases input that French professors can bring to this cross-disciplinary subject by examining American works through a French cultural viewpoint and highlighting French literary and artistic traditions. [source]

    FedEx Ground retools its succession planning and development processes to deliver business results

    Heather D'Alesandro
    A revamped succession planning process at FedEx Ground keeps succession and development decisions clearly focused on the road ahead to ensure the company has its best talent ready for those roles that drive its business strategies and critical initiatives. Changes to the annual talent review process were designed to find and close talent gaps in pivotal leadership roles and competencies, where near-term talent shortages could pose significant business risks. Prework and the review meeting agenda concentrate the discussion on whether the high-potential and promotable individuals are filling these pivotal roles and being developed as rapidly as possible. Enabled by a robust technology platform, officers can also devise broader targeted actions across the organization for addressing shared developmental needs related to critical leadership competencies. 2009 Wiley Periodicals, Inc. [source]

    Providing multimedia communications services from high altitude platforms

    D. Grace
    Abstract System level design considerations for high altitude platforms operating in the mm-wave bands are examined. Propagation effects in these bands are outlined, followed by a brief introduction to different platform scenarios. Ground-based and platform-based fixed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The effects on performance of platform displacement from its desired location with both fixed and steerable antennas are also examined. It is shown that steerable antennas are of most use when fixed stations are immediately below the platform, with no benefit for fixed stations on the edge of coverage. The bandwidths required to serve several traffic distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The effects of temporal changes in the spatial traffic distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes. Copyright 2001 John Wiley & Sons, Ltd. [source]

    Claiming the Moral High Ground: NGOs as Stakeholders

    Pauline P. Cullen
    First page of article [source]

    New Yorkers Respond to the World Trade Center Attack: An Anatomy of an Emergent Volunteer Organization

    William R. Voorhees
    In the aftermath of the New York World Trade Center attack, an emergent group of citizen volunteers organized to provide needed supplies to the workers at Ground Zero. The emergent-group phenomenon has been documented after many disasters. This paper examines the organization of this emergent group through the organizational characteristics of structure, legitimacy, communications, leadership and organizational change. Finally, it argues that through a better understanding of the organizational characteristics, emergency-management personnel will be better prepared to manage and coordinate the activities of disaster-related emergent groups. [source]

    Using SWAT to Model Streamflow in Two River Basins With Ground and Satellite Precipitation Data,

    Kenneth J. Tobin
    Abstract:, Both ground rain gauge and remotely sensed precipitation (Next Generation Weather Radar , NEXRAD Stage III) data have been used to support spatially distributed hydrological modeling. This study is unique in that it utilizes and compares the performance of National Weather Service (NWS) rain gauge, NEXRAD Stage III, and Tropical Rainfall Measurement Mission (TRMM) 3B42 (Version 6) data for the hydrological modeling of the Middle Nueces River Watershed in South Texas and Middle Rio Grande Watershed in South Texas and northern Mexico. The hydrologic model chosen for this study is the Soil and Water Assessment Tool (SWAT), which is a comprehensive, physical-based tool that models watershed hydrology and water quality within stream reaches. Minor adjustments to selected model parameters were applied to make parameter values more realistic based on results from previous studies. In both watersheds, NEXRAD Stage III data yields results with low mass balance error between simulated and actual streamflow (13%) and high monthly Nash-Sutcliffe efficiency coefficients (NS > 0.60) for both calibration (July 1, 2003 to December 31, 2006) and validation (2007) periods. In the Middle Rio Grande Watershed NEXRAD Stage III data also yield robust daily results (time averaged over a three-day period) with NS values of (0.60-0.88). TRMM 3B42 data generate simulations for the Middle Rio Grande Watershed of variable qualtiy (MBE = +13 to ,16%; NS = 0.38-0.94; RMSE = 0.07-0.65), but greatly overestimates streamflow during the calibration period in the Middle Nueces Watershed. During the calibration period use of NWS rain gauge data does not generate acceptable simulations in both watersheds. Significantly, our study is the first to successfully demonstrate the utility of satellite-estimated precipitation (TRMM 3B42) in supporting hydrologic modeling with SWAT; thereby, potentially extending the realm (between 50N and 50S) where remotely sensed precipitation data can support hydrologic modeling outside of regions that have modern, ground-based radar networks (i.e., much of the third world). [source]

    Breaking New Ground in Juvenile Justice Settings: Assessing for Competencies in Juvenile Offenders

    ABSTRACT The field of juvenile justice has made great strides in developing a research base of effective practices and principles, including an understanding of risk factors and needs that contribute to juvenile offending. However, the research base and practice of systematic assessment has not yet fully incorporated youth, family, and community strengths. To address this need, three juvenile justice agencies in the northwestern United States participated in a pilot study to develop and implement an assessment tool (the Youth Competency Assessment) and process that would identify and utilize strengths to help balance the risk and needs focus of their assessment and case planning practices. This article provides descriptions and implementation strategies of the three pilot sites. The article concludes with recommended system changes and policy interventions to support ongoing utilization of this kind of strength-based tool in juvenile justice settings, and a clear set of recommendations for other communities wishing to implement strength-based assessment in their own agencies. [source]

    Be/X-ray binary SXP6.85 undergoes large Type II outburst in the Small Magellanic Cloud

    L. J. Townsend
    ABSTRACT The Small Magellanic Cloud (SMC) Be/X-ray binary pulsar SXP6.85 = XTE J0103,728 underwent a large Type II outburst beginning on 2008 August 10. The source was consistently seen for the following 20 weeks (MJD = 54688,54830). We present X-ray timing and spectroscopic analysis of the source as a part of our ongoing Rossi X-ray Timing Explorer (RXTE) monitoring campaign and INTEGRAL key programme monitoring the SMC and 47 Tuc. A comparison with the Optical Gravitational Lensing Experiment (OGLE) III light curve of the Be counterpart shows the X-ray outbursts from this source coincide with times of optical maximum. We attribute this to the circumstellar disc increasing in size, causing mass accretion on to the neutron star. Ground based infrared photometry and H, spectroscopy obtained during the outburst are used as a measure of the size of the circumstellar disc and lend support to this picture. In addition, folded RXTE light curves seem to indicate complex changes in the geometry of the accretion regions on the surface of the neutron star, which may be indicative of an inhomogeneous density distribution in the circumstellar material causing a variable accretion rate on to the neutron star. Finally, the assumed inclination of the system and H, equivalent width measurements are used to make a simplistic estimate of the size of the circumstellar disc. [source]

    From the Ground, Looking Up: Report on the Video nas Aldeias Tour

    ABSTRACT, This report compares two recent media events centered on the iconography of Amazonian indigenous peoples to highlight the cultural activism of the collaborative video project, Video nas Aldeias. [Keywords: Amazonia, Video nas Aldeias, indigenous media, cultural activism] [source]

    Ground-based detection of thermal emission from the exoplanet WASP-19b,

    N. P. Gibson
    ABSTRACT We present an occultation of the newly discovered hot Jupiter system WASP-19, observed with the High Acuity Wide-field K -band Imager instrument on the VLT, in order to measure thermal emission from the planet's dayside at ,2 ,m. The light curve was analysed using a Markov Chain Monte Carlo method to find the eclipse depth and the central transit time. The transit depth was found to be 0.366 0.072 per cent, corresponding to a brightness temperature of 2540 180 K. This is significantly higher than the calculated (zero-albedo) equilibrium temperature and indicates that the planet shows poor redistribution of heat to the night side, consistent with models of highly irradiated planets. Further observations are needed to confirm the existence of a temperature inversion and possibly molecular emission lines. The central eclipse time was found to be consistent with a circular orbit. [source]

    On Fertile Ground: A Natural History of Human Reproduction

    Nadine R. Peacock
    On Fertile Ground:. Natural History of Human Reproduction. Peter T. Ellison. Cambridge, MA: Harvard University Press, 2001. 358 pp. [source]

    Keep Your Head to the Sky: Interpreting African American Home Ground

    Evelyn Newman Phillips
    Keep Your Head to the Sky: Interpreting African American Home Ground. Grey Gundaker. ed., with the assistance of Tynes Cowan. Charlottesville: University Press of Virginia, 1998. 344 pp. [source]

    The aesthetics of absence: Rebuilding Ground Zero

    Marita Sturken
    ABSTRACT In this article, I examine the narratives and meanings that have been projected onto the space of Ground Zero in New York City since September 11, 2001, how they have been deployed for various political agendas, and how they have informed the ways in which the site will be rebuilt and memorialized. I investigate the changing meanings attributed to the dust and the footprints of the World Trade Center buildings and the debates over architectural designs and the proposed memorial. [source]

    Searching for Common Ground between Supporters and Opponents of Affirmative Action

    Christine Reyna
    Supporters and opponents of affirmative action are often characterized as debating about a single, consensually understood type of affirmative action. However, supporters and opponents instead may have different types of policies in mind when thinking about affirmative action and may actually agree on specific manifestations of affirmative action policies more than is commonly believed. A survey conducted using a student sample and a sample from the broader Chicago-area community showed that affirmative action policies can be characterized into merit-violating versus merit-upholding manifestations. Supporters of affirmative action in general were more likely to think of affirmative action in its merit-upholding manifestations, whereas opponents were more likely to think of the merit-violating manifestations. However, both supporters and opponents showed more support for merit-upholding rather than merit-violating manifestations of affirmative action. The same pattern of results was upheld even when splitting the samples into those who endorsed negative racial attitudes versus those who did not, suggesting that even those who may be considered racist will endorse affirmative action policies that uphold merit values. The results are discussed in terms of the importance of clarifying the political discourse about what affirmative action is and what it is designed to do. [source]

    Buffering an Acidic Stream in New Hampshire with a Silicate Mineral

    Gene E. Likens
    Abstract Ground and pelletized Wollastonite (Wo; CaSiO3) was added to a 50-m reach of an anthropogenically acidified stream within the Hubbard Brook Experimental Forest, New Hampshire, to evaluate its buffering and restoration potential. The Wo was highly effective in raising the pH, acid-neutralizing capacity (ANC), dissolved inorganic carbon (DIC), and Ca2+ concentrations of the stream water, but during the short duration of the experiment had no discernable effect on the stream biota. After initial, spike-like fluctuations in pH and concentrations of ANC, DIC, and Ca2+, the relatively slow dissolution rates of the Wo dampened extreme concentrations and contributed to relatively long-lasting (4 months) amelioration of streamwater acidity. Changes in concentrations of Ca2+, dissolved Si, ANC, and DIC were inversely related to streamflow. After several high, stream-discharge events, concentrations quickly and consistently returned to pre-event conditions. [source]

    Reclaiming Public Ground: The Right to Peaceful Assembly

    THE MODERN LAW REVIEW, Issue 2 2000
    Gina Clayton

    An observing-system experiment with ground-based GPS zenith total delay data using HIRLAM 3D-Var in the absence of satellite data

    Reima Eresmaa
    Abstract Ground-based receiver networks of the Global Positioning System (GPS) provide observations of atmospheric water vapour with a high temporal and horizontal resolution. Variational data assimilation allows researchers to make use of zenith total delay (ZTD) observations, which comprise the atmospheric effects on microwave signal propagation. An observing-system experiment (OSE) is performed to demonstrate the impact of GPS ZTD observations on the output of the High Resolution Limited Area Model (HIRLAM). The GPS ZTD observations for the OSE are provided by the EUMETNET GPS Water Vapour Programme, and they are assimilated using three-dimensional variational data assimilation (3D-Var). The OSE covers a five-week period during the late summer of 2008. In parallel with GPS ZTD data assimilation in the regular mode, the impact of a static bias-correction algorithm for the GPS ZTD data is also assessed. Assimilation of GPS ZTD data, without bias correction of any kind, results in a systematic increase in the forecast water-vapour content, temperature and tropospheric relative topography. A slightly positive impact is shown in terms of decreased forecast-error standard deviation of lower and middle tropospheric humidity and lower tropospheric geopotential height. Moreover, verification of categorical forecasts of 12 h accumulated precipitation shows a positive impact. The application of the static bias-correction scheme is positively verified in the case of the mean forecast error of lower tropospheric humidity and when relatively high precipitation accumulations are considered. Copyright 2010 Royal Meteorological Society [source]

    Intercomparison of line-parameter spectroscopic databases using downwelling spectral radiance

    F. Esposito
    Abstract Ground-based Fourier Transform Spectrometer observations in the infrared, acquired during the Italian phase of the EAQUATE campaign, have been considered in this study and compared to calculations. Synthetic spectral radiances have been obtained using the 2000 and 2004 releases and the 2006 upgrade of HITRAN spectral databases. It has been found that synthetic radiance computations fit the data quite well, even though the goodness of the fit depends on the spectral database. Differences in the spectral residual behaviour appear to be mostly localized in the long-wave side of the Earth emission spectrum, i.e. in the spectral region 520,610 cm,1, which is dominated by the water vapour rotational absorption band. In this range, computation performed with the latest updates provides almost the same results as those of HITRAN2000, while HITRAN2004 shows a mixed behaviour,better than the first two in a large region of the spectral range, but worse at very few specific wave numbers. Overall, HITRAN2006 yields the highest consistency with the observations. No sensitive differences appear at higher wave numbers. Copyright 2007 Royal Meteorological Society [source]

    Eclipsing binaries in the MOST satellite fields

    T. Pribulla
    Abstract Sixteen new eclipsing binaries have been discovered by the MOST satellite among guide stars used to point its telescope in various fields. Several previously known eclipsing binaries were also observed by MOST with unprecedented quality. Among the objects we discuss in more detail are short-period eclipsing binaries with eccentric orbits in young open clusters: V578 Mon in NGC 2244 and HD 47934 in NGC 2264. Long nearly-continuous photometric runs made it possible to discover three long-period eclipsing binaries with orbits seen almost edge-on: HD 45972 with P = 28.1 days and two systems (GSC 154 1247 and GSC 2141 526) with P > 25 days. The high precision of the satellite data led to discoveries of binaries with very shallow eclipses (e.g., HD 46180 with A = 0.016 mag, and HD 47934 with A = 0.025 mag). Ground-based spectroscopy to support the space-based photometry was used to refine the models of several of the systems ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Basic Emergency Medicine Skills Workshop as the Introduction to the Medical School Clinical Skills Curriculum

    Wallace Carter
    Introduction:,Most medical school curricula lack training in basic skills needed in a medical emergency. After the September 11th, 2001 terrorist attacks, junior level medical students at our institution volunteered their time in the emergency department[ or at Ground Zero. They quickly realized they had little or no practical training for an emergency situation. Objectives:,To correct this curriculum deficit, a five hour basic emergency medicine skills / first responder course for students in their first few weeks of medical school was designed. Methods:,The course consists of lectures followed by related skills stations. Lectures include an introduction to the first responder concept, basic airway, breathing, and circulation management, and a rapid, systematic approach to common emergencies. Skills stations teach basic airway management, bag valve mask ventilation, splinting and immobilizing, and moving patients in the field, stressing improvisation. Multiple skills are practiced in a final simulation station using actors with wound moulage and scripted scenarios. Results:,This course, instituted at Weill Cornell Medical School in 2002, has become a mainstay of the first year curriculum. Student evaluations have been uniformly superlative. There is strong student sentiment that this is the most practical course of the first year. Conclusion:,After six years of experience, we have shown it is possible to present a truncated first responder course as part of the first year curriculum. The course generates tremendous interest and awareness regarding emergency medicine. Future research will examine whether skills taught in this course are retained and can be correctly applied later in medical school. [source]

    Why do some species in arid lands increase under grazing?

    AUSTRAL ECOLOGY, Issue 5 2009
    Mechanisms that favour increased abundance of Maireana pyramidata in overgrazed chenopod shrublands of South Australia
    Abstract While the abundance of some plant species decreases under high grazing intensity, others become more abundant. Release from competition by decreaser species contributes to this pattern in mesic systems, but this may not be the case in xeric systems where competition may be less intense. Here we examine three mechanisms that may be involved: (i) increased recruitment and growth because of soil changes produced by grazing, for example, increased soil nutrient availability through dung accumulation; (ii) increased recruitment favoured by the breaking up of the lichen crust; and (iii) reduced competition because of the decline of decreaser species. We used field and glasshouse experiments to determine the possible contribution of these mechanisms to the increase of the chenopod Maireana pyramidata around a watering point in a chenopod shrubland of South Australia. There was no evidence of nutrient accumulation close to the watering point, and while seedlings of M. pyramidata responded to nutrient addition, their growth was the same in soil collected from areas with different grazing intensity. While a broken lichen crust increased the emergence of both M. pyramidata and the decreaser Atriplex vesicaria, the effect was larger for the former. We found no competition between seedlings of the two species or between juveniles of A. vesicaria and seedlings of M. pyramidata in glasshouse experiments. Adult plants of both A. vesicaria and M. pyramidata produced similar growth reduction in seedlings of M. pyramidata. Furthermore, a field removal experiment failed to detect any competitive effect of A. vesicaria on M. pyramidata. Our data indicate that the disintegration of the soil crust by grazer activities can be a major factor controlling floristic changes in overgrazed rangelands. These results imply that factors that control establishment may be more important than competition in shaping shrub population dynamics in these systems. Ground surface itself can affect establishment opportunities, and this should be taken into account in management and restoration efforts in arid lands. [source]

    Experiments on the mechanism of tree and shrub establishment in temperate grassy woodlands: Seedling emergence

    AUSTRAL ECOLOGY, Issue 4 2001
    Peter J. Clarke
    Abstract Field experiments were designed to examine tree and shrub seedling emergence in temperate grassy woodlands on the New England Tablelands. The effects of study sites, intensity of previous grazing, removal of ground cover by fire or clearing, burial of seeds and ant seed theft on seedling emergence were tested in two field experiments. Six tree and seven shrub species were used in the experiments and their cumulative emergence was compared with laboratory germination studies. All species used in field experiments had lower cumulative emergence than those in laboratory germination studies despite prolonged periods of above average rainfall before and after seeds were sown. Eucalypt species emerged faster in the field than the shrub species and generally attained higher cumulative emergence than the shrubs. Spatial effects of sites and patches within sites, and of previous grazing history did not strongly influence patterns of seedling emergence in most species. Ground and litter cover generally did not enhance or suppress the emergence of seedlings, although the removal of cover in recently grazed areas enhanced the emergence of some species. Burning enhanced the emergence of some tree and shrub species where plots had more fuel and intense fires, but this effect was not strong. Compared with other treatments, seedbed manipulations produced the strongest effects. In the absence of both invertebrate and vertebrate predators, seedling emergence was lower for surface-sown seed, compared with seed sown on scarified soil surfaces. Higher seedling emergence of buried seeds in the presence of invertebrate predators probably resulted from the combined effects of predator escape and enhanced moisture status of the germination environment. Some promotion of emergence was achieved for all species in most sown treatments probably as a result of a prolonged above average rainfall. In contrast, the natural recruitment of trees and shrubs was negligible in experimental plots, highlighting the importance of seed supply and dispersal as ultimate determinants of recruitment. [source]

    The Juggler with Half the Balls on the Ground

    BRAIN PATHOLOGY, Issue 1 2010
    Arie Perry MD
    No abstract is available for this article. [source]