Policies and Practices for an Antiracist Geography at the Millennium     

Linda Peake  Audrey Kobayashi 《The Professional geographer》2002,54(1):50-61

As we enter the new millennium, geographers have a momentous opportunity to reflect upon the historical development of our discipline and the academic culture within which it thrives, with the aim of setting out an antiracist agenda. We advocate a fundamental refashioning of the discipline, not simply an extension of its research agenda; for racism, like gender, is not just another item in the lexicon of geographical subjects. The agenda includes, but is not limited to: clarifying relations between racism and law; racism and immigration policy; racism and poverty; and mobilizing racialized groups around policy issues. These items need to be addressed both through scholarship and through activism, as centering geographical practices in the streets rather than in the academy impels not only more effective social change, but also new theoretical understanding of geographies of engagement. Our agenda for antiracist geography also involves three aspects of institutional change: to build up on and extend traditional geographical scholarship; to change the basis of the discipline by extending the principles of antiracism throughout our institutional practices, particularly in the classroom; and to change the face of the discipline by increasing the participation and contributions of geographers of color.  相似文献   

Reducing the effects of vegetation phenology on change detection in tropical seasonal biomes     

Eduarda Martiniano de Oliveira Silveira  Fernando Del Bon Espírito-Santo  Fausto Weimar Acerbi-Júnior  Lênio Soares Galvão  Kieran Daniel Withey  George Alan Blackburn 《地理信息系统科学与遥感》2019,56(5):699-717

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Simulation of the 2004 tsunami of Les Saintes in Guadeloupe (Lesser Antilles) using new source constraints     

Cordrie  Louise  Gailler  Audrey  Escartin  Javier  Feuillet  Nathalie  Heinrich  Philippe 《Natural Hazards》2020,103(2):2103-2129

Natural Hazards - The arc of the Lesser Antilles is associated with a significant tectonic activity due to the subduction of the Atlantic oceanic plate under the Caribbean plate. Earthquakes in...  相似文献   

Worm holes and their space-time continuum: Spatial and temporal variability of macroinfaunal annelids in a Northern New England salt marsh     

David S. Johnson  John W. Fleeger  Kari A. Galván  E. Barry Moser 《Estuaries and Coasts》2007,30(2):226-237

Coastal systems serve many human uses and as a result are susceptible to anthropogenic activities such as nutrient loading and overfishing. In soft sediments, infauna frequently serve as key indicators of such activities. To use infauna effectively as bioindicators, it is important to understand how infaunal abundances and community patterns vary naturally within ecosystems. We examined the spatial and temporal dynamics of infaunal annelids in four tidal creeks of the Plum Island Estuary, Massachusetts, USA, from June to October 2003, sampling along a tidal inundation gradient that crossed five distinct habitats from creek bottoms to the vegetated high marsh platform. Annelids comprised 97% of the total number of macroinfauna. Highest densities were found in creek wall habitats (33,418–65,535 individuals m⁻²), and lowest densities (2,421–10,668 individuals m⁻²) were found inSpartina patens habitats. Five numerically abundant species comprised 87% of the annelid assemblage and three species,Manayunkia aestuarina (Polychaeta),Paranais litoralis (Oligochaeta), andCernosvitoviella immota (Oligochaeta), were broadly distributed across the marsh landscape.Streblospio benedicti (Polychaeta) andFabricia sabella (Polychaeta) were abundant only in mudflat and creek wall habitats, respectively.P. litoralis experienced a summer decline in all habitats, whereasM. aestuarina abundance increased 4–5 fold, in October relative to June in creek wall and tall-formSpartina alterniflora habitats. Hierarchical spatial, analysis revealed that >90% of the variability in annelid abundances was found at the mesospatial scale (<50 m). Variation among the four creeks, (>1 km) was relatively small.  相似文献   

Segmentation of the Nazca and South American plates along the Ecuador subduction zone from wide angle seismic profiles     

Audrey Gailler  Philippe Charvis  Ernst R. Flueh 《Earth and Planetary Science Letters》2007,260(3-4):444-464

We describe the deep structure of the south Colombian–northern Ecuador convergent margin using travel time inversion of wide-angle seismic data recently collected offshore. The margin appears segmented into three contrasting zones. In the North Zone, affected by four great subduction earthquakes during the 20th century, normal oceanic crust subducts beneath the oceanic Cretaceous substratum of the margin underlined by seismic velocities as high as 6.0–6.5 km/s. In the Central Zone the subducting oceanic crust is over-thickened beneath the Carnegie Ridge. A steeper slope and a well-developed, high velocity, Cretaceous oceanic basement characterizes the margin wedge. This area coincides with a gap in significant subduction earthquake activity. In the South Zone, the subducting oceanic crust is normal. The fore-arc is characterized by large sedimentary basins suggesting significant subsidence. Velocities in the margin wedge are significantly lower and denote a different nature or a higher degree of fracturing.

Even if the distance between the three profiles exceeds 150 km, the structural segmentation obtained along the Ecuadorian margin correlates well with the distribution of seismic activity and the neotectonic zonation.  相似文献   

Aircraft observations of Venus' near-infrared reflection spectrum: Implications for cloud composition     

James B. Pollack  Edwin F. Erickson  Fred C. Witteborn  Charles Chackerian  Audrey L. Summers  Warren Van Camp  Betty J. Baldwin  Gordon C. Augason  Lawrence J. Caroff 《Icarus》1974,23(1):8-26

We have obtained measurements of Venus' reflection spectrum in the 1.2 to 4.1-μm spectral region from a NASA-Ames operated Lear jet. This was accomplished by observing both Venus and the sun with a spectrometer that contained a circular, variable interference filter, whose effective spectral resolution was 2%. The aircraft results were compared with computer generated spectra of a number of cloud candidates. The only substance which gave an acceptable match to the profile of Venus' strong 3-μm absorption feature, was a water solution of sulfuric acid, that had a concentration of 75% or more H₂SO₄ by weight. However, our spectra also show a modest decline in reflectivity from 2.3 μm towards 1.2-μm wavekength, which is inconsistent with the flat spectrum of sulfuric acid in this spectral region. We hypothesize that this decline is due to impurities in the sulfuric acid droplets.We also compared our list of cloud candidates with several other observed properties of the Venus clouds. While this comparison does not provide as unique an answer as did our analysis of the 3-μm band, we find that, in agreement with the results of Young (1973) and Sill (1973), concentrated sulfuric acid solutions are compatible with these additional observed properties of the Venus clouds. We conclude that the visible cloud layer of Venus is composed of sulfuric acid solution droplets, whose concentration is 75% H₂SO₄, or greater, by weight.  相似文献   

Ecohydrological modelling with EcH2O‐iso to quantify forest and grassland effects on water partitioning and flux ages     

Audrey Douinot  Doerthe Tetzlaff  Marco Maneta  Sylvain Kuppel  Hubert Schulte‐Bisping  Chris Soulsby 《水文研究》2019,33(16):2174-2191

We used the new process‐based, tracer‐aided ecohydrological model EcH₂O‐iso to assess the effects of vegetation cover on water balance partitioning and associated flux ages under temperate deciduous beech forest (F) and grassland (G) at an intensively monitored site in Northern Germany. Unique, multicriteria calibration, based on measured components of energy balance, hydrological function and biomass accumulation, resulted in good simulations reproducing measured soil surface temperatures, soil water content, transpiration, and biomass production. Model results showed the forest “used” more water than the grassland; of 620 mm average annual precipitation, losses were higher through interception (29% under F, 16% for G) and combined soil evaporation and transpiration (59% F, 47% G). Consequently, groundwater (GW) recharge was enhanced under grassland at 37% (~225 mm) of precipitation compared with 12% (~73 mm) for forest. The model tracked the ages of water in different storage compartments and associated fluxes. In shallow soil horizons, the average ages of soil water fluxes and evaporation were similar in both plots (~1.5 months), though transpiration and GW recharge were older under forest (~6 months compared with ~3 months for transpiration, and ~12 months compared with ~10 months for GW). Flux tracking using measured chloride data as a conservative tracer provided independent support for the modelling results, though highlighted effects of uncertainties in forest partitioning of evaporation and transpiration. By tracking storage—flux—age interactions under different land covers, EcH₂O‐iso could quantify the effects of vegetation on water partitioning and age distributions. Given the likelihood of drier, warmer summers, such models can help assess the implications of land use for water resource availability to inform debates over building landscape resilience to climate change. Better conceptualization of soil water mixing processes and improved calibration data on leaf area index and root distribution appear obvious respective modelling and data needs for improved simulations.  相似文献   

Mapping a geothermal anomaly using apatite (U‐Th)/He thermochronology in the Têt fault damage zone,eastern Pyrenees,France     

Gatan Milesi  Roger Soliva  Patrick Moni  Philippe Münch  Mathieu Bellanger  Olivier Bruguier  Michael Bonno  Audrey Taillefer  Sylvain Mayolle 《地学学报》2019,31(6):569-576

(U‐Th)/He ages on apatite obtained in the vicinity of the Têt fault hydrothermal system show a large variability. In the inner damage zone adjacent to the fault core, where fluid flows are concentrated, AHe ages display a large scatter (3–41 Ma) and apatite ageing. Samples from the outer damage zone show young ages with less dispersion (0.9–21.1 Ma) and apatite rejuvenation. Outside the damage zone, ages are consistent with the regional exhumation history between 20 and 12 Ma. The important age dispersion found in the damage zone is interpreted as the result of ⁴He mobility during fluid infiltration. Our results show that thermochronological data close to a fault should be interpreted with caution, but may offer a new tool for geothermal exploration.  相似文献   

River evaporation and corresponding heat fluxes in forested catchments          下载免费PDF全文

Audrey Maheu  Daniel Caissie  André St‐Hilaire  Nassir El‐Jabi 《水文研究》2014,28(23):5725-5738

River water temperature is a very important variable in ecological studies, especially for the management of fisheries and aquatic resources. Temperature can impact on fish distribution, growth, mortality and community dynamics. River evaporation has been identified as an important heat loss and a key process in the thermal regime of rivers. However, its quantification remains a challenge, mainly because of the difficulty of making direct measurements. The objectives of this study were to characterize the evaporative heat flux at different scales (brook vs river) and to improve the estimation of the evaporative heat flux in a stream temperature model at the hourly timescale. Using a mass balance approach with floating minipans, we measured river evaporation at an hourly timescale in a medium‐sized river (Little Southwest Miramichi) and a small brook (Catamaran Brook) in New Brunswick, Canada. With these direct measurements of evaporation, we developed mass transfer equations to estimate hourly evaporation rates from microclimate conditions measured 2 m above the stream. During the summer 2012, river evaporation was more important for the medium‐sized river with a mean daily evaporation rate of 3.0 mm day^?1 in the Little Southwest Miramichi River compared with that of 1.0 mm day^?1 in Catamaran Brook. Evaporation was the main heat loss mechanism in the two studied streams and was responsible for 42% of heat losses in the Little Southwest Miramichi River and 34% of heat losses in Catamaran Brook during the summer. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Ammonium,nitrate and phytoplankton interactions in a freshwater tidal estuarine zone: potential effects of cultural eutrophication   总被引：2，自引：0，他引：2  

Rita B. Domingues  Ana B. Barbosa  Ulrich Sommer  Helena M. Galvão 《Aquatic Sciences - Research Across Boundaries》2011,73(3):331-343

Nitrate and ammonium are the most important nitrogen sources for phytoplankton growth. Differential utilization of inorganic nitrogenous compounds by phytoplankton has been observed and may have significant impacts on primary productivity at local scales. We used enrichment experiments with natural phytoplankton populations from the freshwater tidal zone of the Guadiana estuary, a coastal ecosystem increasingly subjected to anthropogenic influences, to study the effects of nitrate and ammonium on N-consumption and phytoplankton growth. In addition, we used combined additions of nitrate and ammonium to understand the inhibitory effect of ammonium over nitrate uptake. Ammonium concentrations in the freshwater tidal reaches of the Guadiana estuary throughout the sampling period were too low to exert an inhibitory effect on nitrate uptake or a toxic effect on phytoplankton growth. Nitrate was clearly the main nitrogen source for phytoplankton at the study site. Overall, nitrate seemed to become limiting at concentrations lower than 20 μM and N-limitation was particularly significant during summer. A trend of decreasing nitrate uptake with increasing ammonium concentrations and uptake suggested an overall preference for ammonium. However, preference for ammonium was group-specific, and it was observed mainly in green algae and cyanobacteria. In fact, cyanobacteria relied only on ammonium as their N-source. On the contrary, diatoms preferred nitrate, and did not respond to ammonium additions. The increasing eutrophication in the Guadiana estuary and particularly increased inputs of nitrogen as ammonium due to urban waste effluents may result in a shift in phytoplankton community composition, towards a dominance of cyanobacteria and green algae.  相似文献