Changes in Soybean Yields in the Midwestern United States as a Result of Future Changes in Climate, Climate Variability, and CO2 Fertilization     

Jane Southworth  R. A. Pfeifer  M. Habeck  J. C. Randolph  O. C. Doering  J. J. Johnston  D. G. Rao 《Climatic change》2002,53(4):447-475

This modeling study addresses the potential impacts of climate change and changing climate variability due to increased atmospheric CO₂ concentration on soybean (Glycine max (L.) Merrill) yields in theMidwestern Great Lakes Region. Nine representative farm locations and six future climate scenarios were analyzed using the crop growth model SOYGRO. Under the future climate scenarios earlierplanting dates produced soybean yield increases of up to 120% above current levels in the central and northern areas of the study region. In the southern areas, comparatively small increases (0.1 to 20%) and small decreases (–0.1 to–25%) in yield are found. The decreases in yield occurred under the Hadley Center greenhouse gas run (HadCM2-GHG), representing a greater warming, and the doubled climate variability scenario – a more extreme and variableclimate. Optimum planting dates become later in the southern regions. CO₂fertilization effects (555 ppmv) are found to be significant for soybean, increasing yields around 20% under future climate scenarios.For the study region as a whole the climate changes modeled in this research would have an overall beneficial effect, with mean soybean yield increases of 40% over current levels.  相似文献   

Enhanced Degradation of Halogenated Aliphatics by Zero-Valent Iron   总被引：89，自引：0，他引：89  

Robert W. Gillham  Stephanie F. O'Hannesin 《Ground water》1994,32(6):958-967

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Detecting sampling outliers and sampling heterogeneity when catch-at-length is estimated using the ratio estimator     

Vigneau  Joel; Mahevas  Stephanie 《ICES Journal of Marine Science》2007,64(5):1028-1032

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Groundwater fluctuations and footslope ferricrete soils in the humid tropical zone of southern Cameroon     

Emile Temgoua  Henri‐Bosko Djeuda Tchapnga  Emile Tanawa  Claire Guenat  Hans‐Rudolf Pfeifer 《水文研究》2005,19(16):3097-3111

This paper discusses the relationship between the differentiation of ferruginous accumulations and the variable water saturation of footslope soil patterns. An analysis of the slope morphology of a typical hill in the forest zone of southern Cameroon and a seasonal survey of the levels of groundwaters, springs and rivers were considered in relation to the petrology of different soil patterns. The study site is a tabular hillock whose slopes present a progressive development from steep to gentle slopes. The variable residence time of water within the soil, creating an alternation of reducing and oxidizing conditions, affects soil chemistry, structure and lateral extension of the soil patterns. The ferruginous soil patterns, being formed on the footslopes, gradually increase in extent with decreasing slope angle and the relative rise of the groundwater level. The steep footslopes, where groundwater has a shorter residence time, show a soft mottled clay pattern, restricted to the bottom part of the slope. The moderate footslopes exhibit a deep permanent and a temporary perched groundwater table. The latter, with its regular capillary fringe, contributes to more reducing conditions within isolated domains in the soil patterns, and thus to the alternation with oxidizing conditions, generating a continuous hard soil pattern (massive carapace). The more gently dipping footslopes exhibit groundwater levels near the surface and also a significant amplitude of groundwater fluctuation. Iron, previously accumulated in moderate footslope patterns, is reduced, remobilized, and leached. The soil patterns formed develop into a variegated carapace, more extended along the slope, containing less iron, but nevertheless more hardened, due to the important fluctuations of the groundwater table. These patterns are limited to the zone of groundwater fluctuation and deteriorate as the water fluctuation zone recedes. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

A fission-track and (U–Th)/He thermochronometric study of the northern margin of the South China Sea: An example of a complex passive margin     

Yan Yi  Andy Carter  Bin Xia  Lin Ge  Stephanie Brichau  Hu Xiaoqiong 《Tectonophysics》2009,474(3-4):584-594

Zircon fission track (ZFT), apatite fission track (AFT) and (U–Th)/He thermochronometric data are used to reconstruct the Cenozoic exhumation history of the South China continental margin. A south to north sample transect from coast to continental interior yielded ZFT ages between 116.6 ± 4.7 Ma and 87.3 ± 4.0, indicating that by the Late Cretaceous samples were at depths of 5–6 km in the upper crust. Apatite FT ages range between 60.9 ± 3.6 and 37.3 ± 2.3 Ma with mean track lengths between 13.26 ± 0.16 µm and 13.95 ± 0.19 µm whilst AHe ages are marginally younger 47.5 ± 1.9–15.3 ± 0.5 Ma. These results show the sampled rocks resided in the top 1–1.5 km of the crust for most of the Cenozoic. Thermal history modeling of the combined FT and (U–Th)/He datasets reveal a common three stage cooling history which differed systematically in timing inland away from the rifted margin. 1) Initial phase of rapid cooling that youngs to the north, 2) a period of relative (but not perfect) thermal stasis at ~ 70–60 °C which increases in duration from the south to the north; 3) final-stage cooling to surface temperatures that initiated in all samples between 15 and 10 Ma. The timing and pattern of rock uplift and erosion does not fit with conventional passive margin landscape models that require youngest exhumation ages to be concentrated at or close to the rifted margin. The history of South China margin is more complex aided by weakened crust from the active margin period that immediately preceded rifting and opening of the South China Sea. This rheological inheritance created a transition zone of steeply thinned crust that served as a flexural filter disconnecting the northern margin of the South China block and site of active rifting to the south. Consequently whilst the South China margin displays many features of a rifted continental margin its exhumation history does not conform to conventional images of a passive margin.  相似文献   

On probabilities of avalanches triggered by alpine skiers. An empirically driven decision strategy for backcountry skiers based on these probabilities     

Christian Pfeifer 《Natural Hazards》2009,48(3):425-438

Most fatal avalanche accidents in the Alps are caused by skiers and snowboarders. It has been one aim from the beginning to give guidelines for backcountry skiers in order to avoid avalanche accidents. About 10 years ago, the mountain guide Werner Munter developed a strategy for backcountry skiers whether to go or not to go on a skiing tour. However, his decision strategy has a lack of empirical evidence because he does not take into account incidents without avalanche accidents. This article proposes a decision strategy for backcountry skiers based on probabilities of a logistic regression model using variables, such as danger level, incline of the slope and aspect of the slope, which turned out to be the most important ones. Additional information on frequencies of skiers on slopes under specific conditions is included in the model. We used accident data and avalanche forecasts in Tyrol reported by the Tyrolean avalanche information service within three seasons (1999–2002, 497 days of observations) for model building. Additionally we carried out a holdout validation using data of the same type within two seasons (2002–2004, 314 days of observation) in order to check the accuracy of the model. Our proposal shows a remarkable correlation with Munter’s method.  相似文献   

Ecological criteria, participant preferences and location models: A GIS approach toward ATV trail planning   总被引：1，自引：0，他引：1  

Stephanie A. Snyder  Jay H. Whitmore  Ingrid E. Schneider  Dennis R. Becker   《Applied geography (Sevenoaks, England)》2008,28(4):248-258

This paper presents a geographic information system (GIS)-based method for recreational trail location for all-terrain vehicles (ATVs) which considers environmental factors, as well as rider preferences for trail attributes. The method utilizes the Least-Cost Path algorithm within a GIS framework to optimize trail location. The trail location algorithm considered trail impacts and benefits associated with water bodies, slope, land ownership, noise, trail separation, views, and rider preferences for vegetation types and loop trails. Alternative trails were generated to highlight the influence of different preferences for trail attributes and to demonstrate the capabilities of the Least-Cost Path algorithm as applied to trail location. The method shows promise for use in generating ATV trails, as well as other types of recreational trails, for consideration in recreational planning and analysis.  相似文献   

Northern fulmars as biological monitors of trends of plastic pollution in the eastern North Pacific     

Avery-Gomm S  O'Hara PD  Kleine L  Bowes V  Wilson LK  Barry KL 《Marine pollution bulletin》2012,64(9):1776-1781

Marine plastic debris is a global issue, which highlights the need for internationally standardized methods of monitoring plastic pollution. The stomach contents of beached northern fulmar (Fulmarus glacialis) have proven a cost-effective biomonitor in Europe. However, recent information on northern fulmar plastic ingestion is lacking in the North Pacific. We quantified the stomach contents of 67 fulmars from beaches in the eastern North Pacific in 2009-2010 and found that 92.5% of fulmars had ingested an average of 36.8 pieces, or 0.385g of plastic. Plastic ingestion in these fulmars is among the highest recorded globally. Compared to earlier studies in the North Pacific, our findings indicate an increase in plastic ingestion over the past 40years. This study substantiates the use of northern fulmar as biomonitors of plastic pollution in the North Pacific and suggests that the high levels of plastic pollution in this region warrant further monitoring.  相似文献   

Statistically downscaled projections of snow/rain partitioning for Alaska          下载免费PDF全文

Stephanie A. McAfee  John Walsh  T. Scott Rupp 《水文研究》2015,29(9):2267-2267

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A subregional-scale method to assess aquifer vulnerability to pesticides   总被引：4，自引：0，他引：4  

Schlosser SA  McCray JE  Murray KE  Austin B 《Ground water》2002,40(4):361-367

A method to predict aquifer vulnerability to pesticide contamination at the subregional scale was developed. The assessment method was designed to incorporate relevant hydrologic and pesticide-transport information and to use generally available data. The method assumes steady-state advection of pesticides in the vadose zone, including sorption and biological decay. The solution is presented as a vulnerability index (VI) that increases as the aquifer vulnerability increases. The hydrologic input data for the VI model are obtained from the soil survey geographic database. Pesticides were grouped into three leachability classes using a leachability ratio (half-life divided by organic carbon partition coefficient). Pesticide transformation is assumed to occur in the surface layer. The influence of vertical transport in the remainder of the vadose zone has been incorporated by applying a multiplying factor to the VI that varies with depth to ground water. Hydraulic conductivity is used as a surrogate for soil-water velocity for practical purposes. The performance of the VI model is evaluated using ground water data from Weld County, Colorado. The model is demonstrated to be successful at predicting relative vulnerability, defined as the magnitude of pesticide concentration and percent of wells in a unit that exhibit a pesticide detection. Areas of low, medium, and high vulnerability are assigned. Results indicate that the vulnerability classifications are most dependent on the leachability ratio, hydraulic conductivity, and organic carbon content.  相似文献