Tail reconnection triggering substorm onset     

Angelopoulos V  McFadden JP  Larson D  Carlson CW  Mende SB  Frey H  Phan T  Sibeck DG  Glassmeier KH  Auster U  Donovan E  Mann IR  Rae IJ  Russell CT  Runov A  Zhou XZ  Kepko L 《Science (New York, N.Y.)》2008,321(5891):931-935

Magnetospheric substorms explosively release solar wind energy previously stored in Earth's magnetotail, encompassing the entire magnetosphere and producing spectacular auroral displays. It has been unclear whether a substorm is triggered by a disruption of the electrical current flowing across the near-Earth magnetotail, at approximately 10 R(E) (R(E): Earth radius, or 6374 kilometers), or by the process of magnetic reconnection typically seen farther out in the magnetotail, at approximately 20 to 30 R(E). We report on simultaneous measurements in the magnetotail at multiple distances, at the time of substorm onset. Reconnection was observed at 20 R(E), at least 1.5 minutes before auroral intensification, at least 2 minutes before substorm expansion, and about 3 minutes before near-Earth current disruption. These results demonstrate that substorms are likely initiated by tail reconnection.  相似文献   

Schwermetallanreicherung in den Böden des Abwasserbehandlungsgebietes Braunschweig     

R. Mühlnickel  G. Sngerlaub  Harald Gebhardt 《植物养料与土壤学杂志》1989,152(1):93-97

The accumulation of heavy metals in the soils of the Braunschweig wastewater irrigation area The concentration of lead, zink and cadmium in the Ap-horizons and subsoils of sandy Podzols and Cambisols were investigated. As compared with same soils outside the irrigation area an accumulation of the heavy metals in the Ap-horizons of the older sprinkler irrigation plots was found. On the rill irrigation area the heavy metals also were concentrated in the subsoils.  相似文献   

亚热带红壤地区水土流失的原因、后果和控制措施   总被引：2，自引：0，他引：2  

Zepp Harald 《中国水土保持》2002,(7)

中国亚热带低丘红壤地区水土流失是造成土壤退化的重要原因 ,而土地利用方式的改变是形成严重水土流失的最主要原因。该区第一次土地利用方式变化发生在 2 0世纪 50年代后期 ,自然的次生林被开垦为茶园。第二次变化发生在 80～ 90年代联产承包制改革时期 ,农民有更大的自由决策  相似文献   

Modelling the effects of mulching and fallow cropping on water balance in the Chinese Loess Plateau   总被引：4，自引：0，他引：4  

Shulan Zhang  Lars Lvdahl  Harald Grip  Per-Erik Jansson  Yanan Tong 《Soil & Tillage Research》2007,93(2):283-298

To improve water use efficiency on drylands it is essential to understand the mechanisms affecting water balance partitioning in arable land ecosystems. A field experiment was conducted, from October 2001 to October 2004, to evaluate the effects of field management regimes on water balance and water use efficiency in a winter wheat (Triticum aestivum L.) system in the Loess Plateau, China. The field management regimes tested were: (i) conventional agricultural management (winter wheat followed by a ploughed summer fallow); (ii) conventional management plus a fallow crop used as green manure; (iii) application of wheat straw mulch (0.8 kg m⁻²), which was retained throughout the year (no summer ploughing). A process-oriented ecosystem model (CoupModel) was calibrated with field measurements of soil water contents, leaf area indices, plant heights and crop yields, then used to generate comparative simulations of the water balance partitioning under the wheat straw mulch, fallow crop and conventional management regimes. The simulations indicated that during the experimental period mulching increased soil water storage by 5–8%, decreased soil evaporation by 11–13%, and increased wheat transpiration by 2–5% compared with the conventional management regime, thus increasing the wheat yield and water use efficiency. Furthermore, water reached deeper horizons under mulching than under conventional practice, resulting in 15% more deep percolation in a wet year. The simulation results also indicated that growing green manure during the fallow period decreased soil water storage, leading to lower wheat yields. Mulching proved to be an efficient measure for increasing yields, and possibly contributed to groundwater recharge.  相似文献   

Vergleichende Betrachtung von Verfahren zur Auswertung von Nährstoffsteigerungsversuchen am Beispiel Phosphor     

Harald Munk  Johannes Heyn  Martin Rex 《植物养料与土壤学杂志》2005,168(6):789-796

Comparison of two procedures to evaluate phosphate‐fertilizing field trials Growth response of agricultural crops to different input levels (e.g., fertilizer rates) can be described by the “law of diminishing increments”, which has been formulated mathematically amongst others by Mitscherlich (1928) and von Boguslawski and Schneider (1962, 1963, 1964). In the present paper, the economically optimal phosphate‐fertilizer requirements in 43 long‐term phosphate (P)‐fertilization experiments were calculated using equations on the basis of the yield functions of Mitscherlich or von Boguslawski and Schneider, respectively. For three field trials with linear or disproportionately high yield responses on P fertilization, none of the two procedures could be used. The same held for four trials with maximum yields already appearing at the first fertilization level. Similar P‐fertilization optima were calculated for 36 trials following the “law of diminishing increments”, resulting in a highly significant correlation (R² = 0.946) between both procedures. The correlation coefficients between the phosphate balance at the calculated optimum profitability and CAL‐P content in the soils at trial start were R² = 0.70 (Mitscherlich, 1928) and R² = 0.65 (von Boguslawski and Schneider, 1962, 1963, 1964), respectively. An optimal soil P content of 8–10 mg CAL‐P (100 g soil)^–1 was deduced. Both methods are applicable to calculate the optimum phosphate‐fertilizer requirement if yield effects due to P fertilization follow the “law of diminishing increments” and the increments of fertilization levels in each trial are established in a way that diminishing yield increments can be expected.  相似文献   

Establishing a spatial grouping base for surface soil properties along urban–rural gradient—A case study in Nanjing,China     

Yu-Guo Zhao  Gan-Lin Zhang  Harald Zepp  Jin-Ling Yang 《CATENA》2007

Conventional classification systems based on vegetation and land use are frequently used to characterize or describe urban soils to determine the influence of urbanization on soils. In this study, the sensitivity of different grouping methods in reflecting soil variations along an urban–rural gradient was compared. The objective of this study was to determine the most sensitive grouping system in depicting and explaining variations of soil attributes around an urban area. Grouping methods, including urban–rural division, in situ vegetation type, land use types in different scales and numerical clustering, were compared for both single soil attributes and “soil set” defined by multiple variables. The result shows urbanization has a strong impact on many soil properties, especially that of gravel content, sand content, pH, phosphorus and soil compaction. In terms of the variations of soil attributes, in situ vegetation type is the most sensitive in comparison with local land use types and district-viewed land use types. In other words, soil properties in this study are not sensitive to coarser spatial resolution. Therefore, it's hard to interpret the spatial variation of urban soil by regular methods using natural soil-landscape paradigm. Furthermore, vegetation would best proxy the delineation of single attribute of urban soils. Numerical clusters effectively reflect the land use types and their change during urbanization. All clusters were interpreted as different sets with practical meanings: soil in abandoned greenbelt, soil in ill-managed greenbelt, soil in new vegetable land, extreme urban conditioned soil, soil in well-managed greenbelt, soil in highly mellowed vegetable land, soil in common urban–peri-urban greenbelt and weak-urban-impacted soil. They can be used as bases for soil regionalization in urban and peri-urban environment.  相似文献   

The ‘Bavarian Turnip’ — a rediscovered local vegetable variety of <Emphasis Type="Italic">Brassica rapa</Emphasis> L. em. Metzg. var. <Emphasis Type="Italic">rapa</Emphasis>     

Ludwig?ReinerEmail author  Thomas?Gladis  Harald?Amon  Andreas?Emmerling-Skala 《Genetic Resources and Crop Evolution》2005,52(1):111-113

The Bavarian Turnip (Bayerische Rübe, Brassica rapa L. em. Metzg. var. rapa) is a nearly lost crop today. Until 1900, this local variety was commonly grown in Bavaria for human consumption. The special and very distinct characters of this variety in comparison with recent breeds are preferred by the farmers families and assured the persistence and survival of this turnip in situ (on farm). In the region of Dachau and Freising, located north of Munich, only four farms are known, where this old crop is still grown and maintained. Urgent measures have to be taken to safe this cultural relict for future generations.  相似文献   

Regional assessment of the temporal trends in soil acidification in Southern Sweden,using the safe model     

Mattias Alveteg  Harald Sverdrup  Per Warfvinge 《Water, air, and soil pollution》1995,85(4):2509-2514

The dynamic soil acidification model SAFE was applied to 44 forested sites in Skåne, southern Sweden, using available Swedish databases on present soil status, vegetation and deposition. Time series of deposition were derived for each site from present deposition in a generalized fashion by dividing deposition into different classes and scaling with deposition trends from the literature. This study connects the current status of the soil and the soil development with critical load maps calculated with the steady-state model PROFILE.The model was calibrated against measurements of present base saturation from the Swedish Forest Inventory. Model output was compared with available measurements of soil water chemistry.  相似文献   

Taxonomy and evolution of cultivated plants: Literature review 1982/1983     

Jurgen Schultze-Motel  Reinhard Fritsch  Karl Hammer  Peter Hanelt  Joachim Kruse  Helga I. Maass  Harald Ohle  Klaus Pistrick 《Genetic Resources and Crop Evolution》1984,32(4):245-259

Summary Important papers on taxonomy and evolution of cultivated plants published in 1982 and 1983 were compiled and briefly discussed.

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Taxonomie und Evolution der Kulturpflanzen: Literaturübersicht 1982/1983

Zusammenfassung Wichtige Arbeiten über Taxonomie und Evolution der Kulturpflanzen aus den Jahren 1982 und 1983 wurden zusammengestellt und kurz kommentiert.

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: 1982–1983

, 1982 1983 . .

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Wheat transformation – an update of recent progress     

Prem L. Bhalla  Harald H. Ottenhof  Mohan B. Singh 《Euphytica》2006,149(3):353-366

Summary Genetic transformation is vital to the transfer of novel genes into crop plants as well as to the emerging area of functional genomics. However, the successful genetic transformation of wheat still remains time consuming and genotype dependent. This paper updates the progress made in last 3 years towards developing a robust genetic transformation system for wheat. Agrobacterium-mediated wheat transformation offers advantages such as single-copy gene insertion, minimal rearrangement of DNA, low cost and comparatively high efficiency. The reported recent developments in wheat transformation will lead to increased efficiency of wheat breeding programs. The most promising recent progress is in the development of drought-tolerant wheat, since water stress continues to be a major limiting factor hindering world wheat productivity under adverse hot and dry weather conditions.  相似文献