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41.
42.
Hydraulic redistribution and hydrological controls on aspen transpiration and establishment in peatlands following wildfire 总被引:1,自引:0,他引:1
Midori Depante Matthew Q. Morison Richard M. Petrone Kevin J. Devito Nicholas Kettridge James M. Waddington 《水文研究》2019,33(21):2714-2728
In the sub‐humid Western Boreal Plains of Alberta, where evapotranspiration often exceeds precipitation, trembling aspen (Populus tremuloides Michx.) uplands often depend on adjacent peatlands for water supply through hydraulic redistribution. Wildfire is common in the Boreal Plains, so the resilience of the transfer of water from peatlands to uplands through roots immediately following wildfire may have implications for aspen succession. The objective of this research was to characterize post‐fire peatland‐upland hydraulic connectivity and assess controls on aspen transpiration (as a measure of stress and productivity) among landscape topographic positions. In May 2011, a wildfire affected 90,000 ha of north central Alberta, including the Utikuma Region Study Area (URSA). Portions of an URSA glacio‐fluval outwash lake catchment were burned, which included forests and a small peatland. Within 1 year after the fire, aspen were found to be growing in both the interior and margins of this peatland. Across recovering land units, transpiration varied along a topographic gradient of upland midslope (0.42 mm hr?1) > upland hilltop (0.29 mm hr?1) > margin (0.23 mm hr?1) > peatland (0.10 mm hr?1); similar trends were observed with leaf area and stem heights. Although volumetric water content was below field capacity, P. tremuloides were sustained through roots present, likely before fire, in peatland margins through hydraulic redistribution. Evidence for this was observed through the analysis of oxygen (δ18O) and hydrogen (δ2H) isotopes where upland xylem and peat core signatures were ?10.0‰ and ?117.8‰ and ?9.2‰ and ?114.0‰, respectively. This research highlights the potential importance of hydraulic redistribution to forest sustainability and recovery, in which the continued delivery of water may result in the encroachment of aspen into peatlands. As such, we suggest that through altering ecosystem services, peatland margins following fire may be at risk to aspen colonization during succession. 相似文献
43.
Eighy-one CTD profiles gathered in springtime were used for northem East China Sea tbermohalinefinestructure studies indicating that the finestructure properties vaned with region and depth, as shown infinesructure specra, distribution of Cox numbers etc..Some results closely wiated to distribution of watermasses and Analysis of two typical profiles revealed differenes in autospectra of temperature,salihity and potential density gradients, probobility distribution of temperature finestructure gradient,Cox numberc.etc. The probability density function of vertical temperature gradients, which varied withsample interval, is given. The variances of temperatare finestructare gradient are used to estimate the lat-eral diffusivity and lateral temperatare flux, which were 10.3 (m~2/s) and 5.5×10~(-4) (℃ m/s),respectivly. 相似文献
44.
《The Professional geographer》1986,38(1):105-130
Book Reviewed in this article: Unfairly Structured Cities . Blair Badcock Religion and Rural Revolt . Janos M. Bak and Gerhard Benecke The Industrial Geography of Canada . Anthony Blackbourn and Robert G. Putnam The Cuban-American Experience, Culture, Images, and Perspectives. Thomas D. Boswell and James R. Curtis Quaternary Paleoclimatology . R. S. Bradley Development and Crisis in Brazil, 1930–1983 . Luiz Bresser Pereiras Centres of Origin in Biogeography . John C. Briggs Analytical Urban Geography . Martin Cadwallader Geomorphology . Richard J. Chorley , Stanley A. Schumm, and David E. Sugden South Africa: The Impact of Past Geographies . A. J. Christopher The Geography of Underdevelopment. A Critical Survey . D. K. Forbes Health Care in Developing Countries . Wilbert M. Gesler Place to Grow Old: The Meaning of Environment in Old Age . Stephen M. Golant The Emerging Marine Economy of the Pacific . Chennat Gopalakrishnan An Introduction to Agricultural Geography . David B. Grigg The Soviet Union: A Geographical Study . G. Melvyn Howe Geographical Aspects of Health: Essays in Honour of Andrew Learmonth . N. D. Mc Glashan and J. R. Blunden Physical Geography: A Landscape Appreciation . Tom L. Mc Knight Mountain Experience. The Psychology and Sociology of Adventure. Richard G. Mitchell Jr . Systematic and Regional Biogeography. Stanley A. Morain The Economic Transformation of American Cities. T. J. Noyelle and T. M. Stanback , Jr . Normal Accidents: Living With High-Risk Technologies. Charles Perrow Vanishing Farmland: A Legal Solution for the States. Sarah E. Redfield Applied Methods of Regional Analysis: The Spatial Dimensions of Development Policy. Dennis A. Rondinelli Urbanization in Romania. A Geography of Social and Economic Change Since Independence. Per Ronnas Statistical Techniques in Geographical Analysis. Gareth Shaw and Dennis Wheeler The Granite Garden: Urban Nature and Human Design. Anne Whiston Spirn Political Geography: Recent Advances and Future Directions. Peter Taylor and John House Geographia y Medio Ambiente. Manuel Valenzuela -Rubío Nãgara and Commandery: Origins of the Southeast Asian Urban Traditions. Paul Wheatley The Common Fisheries Policy of the European Community. Mark Wise Geography and Gender. Women and Geography Study Group of the IBG Technological Hazards. D. J. Zeigler , J. H. Johnson , S. D. Brunn 相似文献
45.
Amine Ait-Ouahmed Didier Josselin Fen Zhou 《International journal of geographical information science》2018,32(2):367-398
Car-sharing system with electric cars is a very convenient service for urban transportation: it allows users to pick up a vehicle at a station and rent it during a short time. To manage this kind of system in the best way, it is necessary to solve the critical problem of vehicle stock imbalance across the stations. Several decision levels must be considered to balance the car distribution by taking into account the quality of service and the system operation cost. To this end, a linear programming model is proposed to formalize the problem in a mathematical framework, which allows the computation of optimal vehicle distribution strategies. To make our solution time efficient and usable for solving large problems, a greedy algorithm and a tabu search algorithm are proposed. These two algorithms are applied to the Auto Bleue network in Nice and its surrounding (France) using extensive simulations. Besides, an integrated mapping method is provided within the Geographical Information System QGIS to estimate flows and their locations. Numerical results demonstrate that the tabu search algorithm is able to find near-optimal solutions and good compromises between client satisfaction, number of staff agents and vehicles used, and computing time. 相似文献
46.
7Be is a naturally occurring cosmogenic radionuclide produced in the stratosphere and troposphere as a result of cosmic ray spallation of nitrogen and oxygen. The constant fallout via precipitation and short half-life (53.3 days), coupled with shallow depth distribution in soil profile (~2 cm) provide the unique advantages for its application as a soil and sediment tracer over short timescales, such as a single storm or short period of extreme rainfall. With the climate change and increasing rainfall events, the 7Be tracing method will exhibit wide application prospect in future. To date, however, this technique is still in its infancy and some important assumptions have not yet been effectively validated. Consequently, the use of 7Be to document soil erosion rates has been limited. This contribution briefly reviews the history and current status relating to this tracing method. In addition, the basic principles and recent research progresses in conversion models for use of 7Be measurements to estimate soil redistribution rates are introduced. The key assumptions and uncertainties of the technique, as well as the effects of the vegetation interception and particle size selectivity are discussed. Additionally, some new investigation directions are provided, including the assumption validation and uncertainty analysis, the impact of vegetation interception, the extending of spatial and temporal scales, and the development of new conversion models. 相似文献
47.
本文介绍了自动校准的温度和盐度测量技术,该技术应用在海洋863项目中水质监测浮标的温盐传感器中,自动校准技术可使传器稳定性,准确芳得到很大提高,对应用到海洋领域进行长期观测的传感器具有重要意义。 相似文献
48.
Decadal Climatic Anomalies in the Northern Adriatic Sea Inferred from a New Oceanographic Data Set 总被引:1,自引:0,他引:1
Abstract. In 1997, Artegiani et al. depicted for the first time the seasonal climatology of the Adriatic Sea; they used the ATOS data set, formed by 5540 oceanographic stations sampled over this continental basin from 1911 to 1980. Lately, two Italian institutes working on the Adriatic Sea for long time, IBM and IRPEM, merged their recent data sets for the northernmost part of the basin. This yielded 3600 new oceanographic stations, concentrated in an area where 809 ATOS stations were located. The new data were quality checked, and then a seasonal climatology was drawn up as a first analysis step. The new climatology differed significantly from the ATOS results; this could be explained, at least partially, by the climatic changes that have occurred on this area. For example, air temperature increased significantly over northern Italy starting from 1988. Variations of the observed air temperature and Po River runoff qualitatively agree with sea surface temperature and salinity variations. A preliminary computation of heat fluxes based on ECMWF reanalysis confirms an increased heat flux to the Northern Adriatic Sea starting from 1988. 相似文献
49.
Oceanic double-infusion: introduction 总被引:1,自引:0,他引:1
Double-diffusion, the mixing of fluids with two constituents of different molecular diffusivities, was originally discovered in the mid-1800s, forgotten, then rediscovered as an ‘oceanographic curiosity’ a century later. Many oceanographers suspect that double-diffusion has major effects on oceanic water masses and circulation, but direct measurement of the effects has proven difficult. In 1996, a Working Group was formed under the auspices of the Scientific Committee on Ocean Research (SCOR WG108), with the goal to identify progress and barriers to quantifying oceanic double-diffusive fluxes, and make recommendations for further progress. This document gives a brief history of double-diffusion, a review of evidence of its potential effects in the ocean, and gives an overview of the review articles contained in this volume, written by the Working Group members with the above aim in mind. 相似文献
50.