A landscape analysis of the candelaria watershed in mexico: Insights into paleoclimates affecting upland horticulture in the southern yucatan peninsula semi-karst     

Joel D. Gunn  William J. Folan  Hubert R. Robichaux 《Geoarchaeology》1995,10(1):3-42

Biocultural systems adapt to global climate change through its regional manifestations. Subsistence customs are the cultural interface between regional climate and culture at large. Swidden horticulturalists in Campeche, Mexico report that dry April followed by early onset of the wet season enhances the productivity of upland tropical gardens, or milpas. To relate regional seasonality of moisture to global climate, growing season discharge for Mexico's Candelaria River from 1958 to 1990 was analyzed relative to global average temperature. Analysis of covariance revealed a statistically significant relationship (p < 0.001). Further analysis showed that hot global climate eliminates the dry season, which lowers milpa productivity by preventing burning of the slash. Cold global climate delays the wet season and planting, also at cost of productivity. Intermediate global temperature fosters optimal wet—dry season combinations. Productivity of milpas is therefore directly related to global climate through the intervening mechanism of seasonality of moisture. A regression model reflecting these findings is used to retrodict paleohydrology for the last 3000 years. The pattern of ascendancy and decline of ancient southern Maya lowland urban centers is reviewed in the perspective of changing hydrological conditions. The model indicates that fluorescence occurred with optimal balance of wet and dry season duration and catastrophes unfolded during extended wet or dry periods. We suggest that the southern Maya lowlands have had a precipitous record of urban development and collapse in part because of complex interactions of global climate and upland horticulture. The most productive conditions for milpa issue from an inherently unstable overlay of global climate on a relatively narrow band of partially developed karst (semikarst) geological formations.  相似文献   

Evolution of cutoffs across meander necks in Powder River,Montana, USA     

Glenn R. Gay  Hubert H. Gay  William H. Gay  Holly A. Martinson  Robert H. Meade  John A. Moody 《地球表面变化过程与地形》1998,23(7):651-662

Over a period of several decades, gullies have been observed in various stages of forming, growing and completing the cutoff of meander necks in Powder River. During one episode of overbank flow, water flowing over the down-stream bank of the neck forms a headcut. The headcut migrates up-valley, forming a gully in its wake, until it has traversed the entire neck, cutting off the meander. The river then follows the course of the gully, which is subsequently enlarged as the river develops its new channel. The complete process usually requires several episodes of high water: in only one of the five cases described herein was a meander cutoff initiated and completed during a single large flood. © 1998 John Wiley & Sons, Ltd.  相似文献   

Field observations in a small subtropical estuary during and after a rainstorm event     

Hubert Chanson 《Estuarine, Coastal and Shelf Science》2008

In Australia, a large majority of small subtropical estuaries are narrow, elongated and meandering channels with large width to depth ratio and cross-sections which deepen and widen towards the mouth. Up to date, episodic rainstorm events in such small systems were rarely documented, and this study presents a field data set collected during and immediately after a rainstorm. A number of hydrodynamic and physio-chemical parameters were recorded simultaneously at several longitudinal locations for 12 h. The field measurements demonstrated a significant flushing of the estuarine zone, caused primarily by the rainfall runoff from the nearby shopping malls and roadways. Some strong vertical stratification of the water column was observed at all sampling locations, and the depth-averaged salinity data exhibited a dome-shaped intrusion curve. A solution of the salt dispersion equation provided some agreement with the freshwater flushing conditions during the wet weather.  相似文献   

Turbulence characteristics of a small subtropical estuary during and after some moderate rainfall   总被引：1，自引：0，他引：1  

Mark Trevethan  Hubert Chanson  Richard Brown 《Estuarine, Coastal and Shelf Science》2008,79(4):661-670

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Meeting review: The nice symposium on the origin of the solar system     

Hubert Reeves 《Icarus》1973,19(4):604-606

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Excursion to Cardiff: March 31st to April 8th. Easter, 1920     

A. Hubert Cox  T. Franklin Sibly  A.E. Trueman 《Proceedings of the Geologists' Association. Geologists' Association》1920,31(4):200-IN5

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Quality assurance of hydroacoustic surveys: the repeatability of fish-abundance and biomass estimates in lakes within and between hydroacoustic systems   总被引：1，自引：1，他引：1  

Wanzenbock  Josef; Mehner  Thomas; Schulz  Michael; Gassner  Hubert; Winfield  Ian J 《ICES Journal of Marine Science》2003,60(3):486-492

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Resilience,Adaptability, and Regime Shifts Thinking: A Perspective of Dryland Socio-ecology System     

PENG Yu  ZHANG Qiuying  CHEN Yuanzhan  XU Ning  QIAO Yunfeng  TIAN Chao  Hubert HIRWA  Salif DIOP  Aliou GUISSE  LI Fadong 《资源与生态学报(英文版)》2021,12(3):376-383

Arid areas are widespread globally and support a third of the world’s population’s livelihoods. The increasing population, urbanization, land-use changes, and the climate significantly affect coupled natural and human systems and threaten environments and socio-ecological land systems. The degradation of drylands poses a severe and widespread threat to the lives of millions of people, especially in developing countries and in the global environment. This review assesses published literature on dryland socio-ecological systems to reveal current research trends and changes in research themes over time and introduces basic theories and advances in dryland socio-ecological system frameworks, resilience measurement, and regime shifts. Developing a more general but adaptable framework and a more practical strategy for long-term coordination and partnership and attaining specific insights into ecological services should receive more attention and be strengthened in future studies on drylands sustainability.  相似文献   

Measurements of the helium 584 Å airglow during the Cassini flyby of Venus     

J.-C. Gérard  J. Gustin  B. Hubert  G.R. Gladstone  L.W. Esposito 《Planetary and Space Science》2011,59(13):1524-1528

The helium resonance line at 584 Å has been observed with the UltraViolet Imaging Spectrograph (UVIS) Extreme Ultraviolet channel during the flyby of Venus by Cassini at a period of high solar activity. The brightness was measured along the disk from the morning terminator up to the bright limb near local noon. The mean disk intensity was ∼320 R, reaching ∼700 R at the bright limb. These values are slightly higher than those determined from previous observations. The sensitivity of the 584 Å intensity to the helium abundance is analyzed using recent cross-sections and solar irradiance measurements at 584 Å. The intensity distribution along the UVIS footprint on the disk is best reproduced using the EUVAC solar flux model and the helium density distribution from the VTS3 empirical model. It corresponds to a helium density of 8×10⁶ cm⁻³ at the level of where the CO₂ is 2×10¹⁰ cm⁻³.  相似文献   

Post-depositional redistribution of trace metals in reservoir sediments of a mining/smelting-impacted watershed (the Lot River,SW France)     

Stéphane Audry  Cécile Grosbois  Hubert Bril  Jörg Schäfer  Jakub Kierczak  Gérard Blanc 《Applied Geochemistry》2010

Mining/smelting wastes and reservoir sediment cores from the Lot River watershed were studied using mineralogical (XRD, SEM–EDS, EMPA) and geochemical (redox dynamics, selective extractions) approaches to characterize the main carrier phases of trace metals. These two approaches permitted determining the role of post-depositional redistribution processes in sediments and their effects on the fate and mobility of trace metals. The mining/smelting wastes showed heterogeneous mineral compositions with highly variable contents of trace metals. The main trace metal-bearing phases include spinels affected by secondary processes, silicates and sulfates. The results indicate a clear change in the chemical partitioning of trace metals between the reservoir sediments upstream and downstream of the mining/smelting activities, with the downstream sediments showing a 2-fold to 5-fold greater contribution of the oxidizable fraction. This increase was ascribed to stronger post-depositional redistribution of trace metals related to intense early diagenetic processes, including dissolution of trace metal-bearing phases and precipitation of authigenic sulfide phases through organic matter (OM) mineralization. This redistribution is due to high inputs (derived from mining/smelting waste weathering) at the water–sediment interface of (i) dissolved SO₄ promoting more efficient OM mineralization, and (ii) highly reactive trace metal-bearing particles. As a result, the main trace metal-bearing phases in the downstream sediments are represented by Zn- and Fe-sulfides, with minor occurrence of detrital zincian spinels, sulfates and Fe-oxyhydroxides. Sequestration of trace metals in sulfides at depth in reservoir sediments does not represent long term sequestration owing to possible resuspension of anoxic sediments by natural (floods) and/or anthropogenic (dredging, dam flush) events that might promote trace metal mobilization through sulfide oxidation. It is estimated that, during a major flood event, about 870 t of Zn, 18 t of Cd, 25 t of Pb and 17 t of Cu could be mobilized from the downstream reservoir sediments along the Lot River by resuspension-induced oxidation of sulfide phases. These amounts are equivalent to 13-fold (Cd), ∼6-fold (Zn), 4-fold (Pb) the mean annual inputs of the respective dissolved trace metals into the Gironde estuary.  相似文献