Resprout characteristics of creosote bush (Larrea tridentata) when subjected to repeated vehicle damage     

Arthur C. Gibson  M. Rasoul Sharifi  Philip W. Rundel 《Journal of Arid Environments》2004,57(4):411

Studies were conducted in the central Mojave Desert to quantify how creosote bushes (Larrea tridentata) respond to physical damage during large-scale military training exercises. Creosote bush possesses a resilient growth form that recovers from repeated physical damage via resprouts arising from meristems in stem bark below severed or crushed canopy units. At high levels of disturbance by heavy vehicles, nearly all individuals showed measurable breakage, but without additional damage each plant can regain a full canopy within 5 years under arid field conditions. Resprouts exhibited more vigorous growth and doubled the biomass accumulation stimulated by high rainfall of 1998, an El Niño year, vs. a normal year. New shoots of resprouted individuals were markedly different in morphological traits than canopy old growth and had slightly higher predawn shoot water potentials. The natural ability of this evergreen species to recover from cutting and crushing bodes well for re-establishment of creosote bush desert scrub communities following episodes of severe damage by vehicles.  相似文献   

Denitrification capacity in a subterranean estuary below a Rhode Island fringing salt marsh     

Kelly Addy  Arthur Gold  Barbara Nowicki  James McKenna  Mark Stolt  Peter Groffman 《Estuaries and Coasts》2005,28(6):896-908

Coastal waters are severely threatened by nitrogen (N) loading from direct groundwater discharge. The subterranean estuary, the mixing zone of fresh groundwater and sea water in a coastal aquifer, has a high potential to remove substantial N. A network of piezometers was used to characterize the denitrification capacity and groundwater flow paths in the subterranean estuary below a Rhode Island fringing salt marsh.¹⁵N-enriched nitrate was injected into the subterranean estuary (in situ push-pull method) to evaluate the denitrification capacity of the saturated zone at multiple depths (125–300 cm) below different zones (upland-marsh transition zone, high marsh, and low marsh). From the upland to low marsh, the water table became shallower, groundwater dissolved oxygen decreased, and groundwater pH, soil organic carbon, and total root biomass increased. As groundwater approached the high and low marsh, the hydraulic gradient increased and deep groundwater upwelled. In the warm season (groundwater temperature >12 °C), elevated groundwater denitrification capacity within each zone was observed. The warm season low marsh groundwater denitrification capacity was significantly higher than all other zones and depths. In the cool season (groundwater temperature <10.5 °C), elevated groundwater denitrification capacity was only found in the low marsh. Additions of dissolved organic carbon did not alter groundwater denitrification capacity suggesting that an alternative electron donor, possibly transported by tidal inundation from the root zone, may be limiting. Combining flow paths with denitrification capacity and saturated porewater residence time, we estimated that as much as 29–60 mg N could be removed from 11 of water flowing through the subterranean estuary below the low marsh, arguing for the significance of subterranean estuaries in annual watershed scale N budgets.  相似文献   

Public attitudes towards flooding and property-level flood protection measures     

Seth Owusu  Grant Wright  Scott Arthur 《Natural Hazards》2015,77(3):1963-1978

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Let us have some consideration for the lowly reviewer          下载免费PDF全文

Arthur J. Horowitz 《水文研究》2014,28(12):3999-4000

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Modeling the risk of spread and establishment for Asian longhorned beetle (Anoplophora glabripennis) in Massachusetts from 2008-2009     

Andrew J. Shatz  Florencia Sangermano  Jennifer Miller  Arthur Elmes 《国际地球制图》2016,31(8):813-831

Land managers responsible for invasive species removal in the USA require tools to prevent the Asian longhorned beetle (Anoplophora glabripennis) (ALB) from decimating the maple-dominant hardwood forests of Massachusetts and New England. Species distribution models (SDMs) and spread models have been applied individually to predict the invasion distribution and rate of spread, but the combination of both models can increase the accuracy of predictions of species spread over time when habitat suitability is heterogeneous across landscapes. First, a SDM was fit to 2008 ALB presence-only locations. Then, a stratified spread model was generated to measure the probability of spread due to natural and human causes. Finally, the SDM and spread models were combined to evaluate the risk of ALB spread in Central Massachusetts in 2008–2009. The SDM predicted many urban locations in Central Massachusetts as having suitable environments for species establishment. The combined model shows the greatest risk of spread and establishment in suitable locations immediately surrounding the epicentre of the ALB outbreak in Northern Worcester with lower risk areas in suitable locations only accessible through long-range dispersal from access to human transportation networks. The risk map achieved an accuracy of 67% using 2009 ALB locations for model validation. This model framework can effectively provide risk managers with valuable information concerning the timing and spatial extent of spread/establishment risk of ALB and potential strategies needed for effective future risk management efforts.  相似文献   

Exploring seven hundred years of transhumance,climate dynamic,fire and human activity through a historical mountain pass in central Spain     

José Antonio López-Sáez  Francisca Alba-Sánchez  Sandra Robles-López  Sebastián Pérez-Díaz  Daniel Abel-Schaad  Silvia Sabariego-Ruiz  Arthur Glais 《山地科学学报》2016,13(7):1139-1153

A high-altitude peat sequence from the heart of the Spanish Central System (Gredos range) was analysed through a multi-proxy approach to determine the sensitivity of high-mountain habitats to climate, fire and land use changes during the last seven hundred years, providing valuable insight into our understanding of the vegetation history and environmental changes in a mountain pass close to a traditional route of transhumance. The pollen data indicate that the vegetation was dominated by shrublands and grasslands with scattered pines in high-mountain areas, while in the valleys cereals, chestnut and olive trees were cultivated. Strong declines of high-mountain pines percentages are recorded at 1540, 1675, 1765, 1835 and 1925 cal AD, which may be related to increasing grazing activities and/or the occurrence of anthropogenic fires. The practice of mountain summer farming and transhumance deeply changed and redesigned the landscape of the high altitudes in central Spain (Gredos range) since the Middle Ages, although its dynamics was influenced in some way by climate variability of the past seven centuries.  相似文献   

Holocene landscape evolution in the pawnee river valley,southwestern kansas,rolfe d. mandel, 1994, kansas geological survey and kansas state historical society,bulletin 236, iv + 117 pp., $12.00 (softbound)     

E. Arthur Bettis 《Geoarchaeology》1995,10(1):90-92

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Changing trust relations within the Dutch fishing industry: The case of National Study Groups     

Birgit I. de Vos  Arthur P.J. Mol 《Marine Policy》2010

This paper focuses on changing trust relationships among fishermen following new governance arrangements. The previous ‘thick’ trust relationships that characterized the Dutch fisheries industry under a neo-corporatist arrangement had resulted in an isolation of local fishermen groups vis-à-vis outsiders. However, under new governance arrangements, in particular the so-called Study Groups, these trust relationships are changing. The establishment of Study Groups, where fishermen from different localities have to cooperate on sustainability innovations in order to receive subsidies, lead to more diversity within the industry, more collaborations across localities and new forms of ‘thin’ trust. As such, these Study Groups can be understood as successful experiments in further opening up of the fisheries community.  相似文献   

大马士革非正式聚落的讨论(英文)     

KHADOUR Yassar  KAFA Main 《地球空间信息科学学报》2009,12(4):289-295

Toadies cities are accumulating the global population in their territories,occurring formally and informally.The in-crease of urban informality is the most significant trend shaping the 21st century world.Furthermore,the urban informality theory should be considered in urbanization courses and development studies.With the rapid economic market development,changes mapped the major Syrian cities.Damascus is in the midst of a profound transformation of architectural and planning changes.Damascus urbanization i...  相似文献   

A review of numerical experiments on seismic wave scattering     

Arthur Frankel 《Pure and Applied Geophysics》1989,131(4):639-685

This paper reviews applications of the finite-difference and finite-element methods to the study of seismic wave scattering in both simple and complex velocity models. These numerical simulations have improved our understanding of seismic scattering in portions of the earth where there is significant lateral heterogeneity, such as the crust. The methods propagate complete seismic wavefields through highly complex media and include multiply scattered waves and converted phases (e.g.,P toSV, SV toP, body wave to surface wave). The numerical methods have been especially useful in cases of moderate and strong scattering in complex media where multiple scattering becomes important. Progress has been made with numerical methods in understanding how near-surface, low-velocity basin structures scatter surface waves and vertically-incident body waves. The numerical methods have proven useful in evaluating scattering of surface waves and body waves from topography of both the free surface and interfaces buried at depth. Numerical studies have demonstrated the importance of conversions from body waves to surface waves (andvice versa) when lateral heterogeneities and topographic relief are present in the uppermost crust. Recently, several investigations have applied numerical methods to study seismic wave propagation in velocity models which vary randomly in space. This stochastic approach seeks to understand the effects of small-scale complexity in the earth which cannot be resolved deterministically. These experiments have quantified the relationships between the statistical properties of the random heterogeneity and the measurable properties of high-frequency (1 Hz) seismograms. These simulations have been applied to the study of many features observed in actual high-frequency seismic waves, including: the amplitude and time decay of seismic coda, the apparent attenuation from scattering, the dispersion of waveforms, and the travel time and waveform variations across arrays of receivers.  相似文献