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排序方式: 共有124条查询结果,搜索用时 593 毫秒
21.
Fortuniak Krzysztof Przybylak Rajmund Araźny Andrzej Pawlak Włodzimierz Wyszyński Przemysław 《Theoretical and Applied Climatology》2017,130(3-4):959-970
Maize is grown by millions of smallholder farmers in South Asia (SA) under diverse environments. The crop is grown in different seasons in a year with varying exposure to weather extremes, including high temperatures at critical growth stages which are expected to increase with climate change. This study assesses the impact of current and future heat stress on maize and the benefit of heat-tolerant varieties in SA. Annual mean maximum temperatures may increase by 1.4–1.8 °C in 2030 and 2.1–2.6 °C in 2050, with large monthly, seasonal, and spatial variations across SA. The extent of heat stressed areas in SA could increase by up to 12 % in 2030 and 21 % in 2050 relative to the baseline. The impact of heat stress and the benefit from heat-tolerant varieties vary with the level of temperature increase and planting season. At a regional scale, climate change would reduce rainfed maize yield by an average of 3.3–6.4 % in 2030 and 5.2–12.2 % in 2050 and irrigated yield by 3–8 % in 2030 and 5–14 % in 2050 if current varieties were grown under the future climate. Under projected climate, heat-tolerant varieties could minimize yield loss (relative to current maize varieties) by up to 36 and 93 % in 2030 and 33 and 86 % in 2050 under rainfed and irrigated conditions, respectively. Heat-tolerant maize varieties, therefore, have the potential to shield maize farmers from severe yield loss due to heat stress and help them adapt to climate change impacts. 相似文献
22.
Oimahmad Rahmonov Tadeusz Szczypek Tadeusz Niedźwiedź Urszula Myga-Piątek Małgorzata Rahmonov Valerian A. Snytko 《Environmental Earth Sciences》2017,76(8):324
Detailed analyses were conducted of human impact on juniper forest landscapes occurring within the Zarafshan Range (Pamir-Alay). Juniperus seravschanica and J. semiglobosa belong to forest-forming species in Central Asia. At present, juniper forests all over Tajikistan are seriously threatened as a result of excessive logging and cattle grazing. The aim of this paper is to present juniper forest transformation as a result of human activities as well as the diversity of soil properties in the organic and humus horizons in the altitudinal system of soil zonation. Three groups of phytocoenoses were distinguished: those with a dominant share of Juniperus seravschanica; those with a dominant share of J. semiglobosa; and mixed. Associations with Juniperus seravschanica and J. semiglobosa feature several variants of phytocoenoses with dominant species: Artemisia lehmanniana, A. dracunculus, Eremurus olgae, Festuca sulcata, Ligularia thomsonii, Stipa turkestanica, Thymus seravschanicus, and Ziziphora pamiroalaica. The collected soil samples differ in their granulometric composition. Gravelly cobble fractions >2 mm are dominant; the share of sandy particles <2 mm is much lower (about 10–20%). Fraction 0.5–0.05 attains 35% on average. The Corg content of the soil varied from 0.26 to 11.40% in the humus horizon (A) and from 4.3 to 25% in the organic (O). Similar relationships were reported in the case of Ntot concentration. A clear relationship can be observed between concentrations of Corg and Ntot. Soil pH varied, ranging from very low acidic (pH 5.5) to neutral (pH 8.5). The content of available P varied; high concentrations were noted in organic (O) (40.46–211 mg kg?1) and mixed horizons (OA) (2.61–119 mg kg?1). Maximum accumulations of Pavail (1739.6 mg kg?1) and Ptot (9696 mg kg?1) were observed at a site heavily affected by intense grazing. Concentrations of Mgavail varied from 116 to 964 mg kg?1. Most of the analysed soil profiles lacked an organic horizon; only thin humus occurred. 相似文献
23.
Jadwiga Wyszkowska Edyta Boros-Lajszner Waldemar Lajszner Jan Kucharski 《Environmental Earth Sciences》2017,76(11):403
Study was carried out to compare the effect of the degree of contamination of soil with copper on the soil enzyme activity, depending on the type of chemical compound with which a metal reaches the soil and on the method of soil use. An effect of increasing doses of copper on growth and the development of spring barley has been studied. The study was carried out as a pot experiment on two types of soil: loamy sand and light loam. Copper was introduced to soil as copper(II) sulphate(VI) and copper(II) chloride at four doses: 150, 300, 450 and 600 mg Cu2+ kg?1 d.m. of soil. Soil without copper was used as a control sample. The experiment showed that contamination of soil with copper applied as CuCl2 and CuSO4·5H2O upset the homeostasis of soil. Dehydrogenases and urease were the most sensitive to contamination of soil with Cu2+, both as copper(II) chloride and as copper(II) sulphate(VI), and acid phosphatase and alkaline phosphatase were the least sensitive. Greater changes in enzymatic activity were observed in loamy sand than in light loam. The differences in the impact of copper(II) sulphate(VI) and copper(II) chloride on the soil microbiome were relatively small, because mean ED50 for copper(II) chloride was 341 mg Cu2+ kg?1 d.m. of soil, and for copper(II) sulphate(VI) it was 364 mg Cu2+ kg?1 d.m. of soil. This inhibitory effect of copper persisted throughout the period of the experiment. The sensitivity of spring barley to copper compounds was lower than the enzymes under study. 相似文献
24.
M. Jamrozy D. Kozieł-Wierzbowska S. Zoła A. Kuźmicz J. Machalski 《Journal of Astrophysics and Astronomy》2011,32(4):467-470
J1159+5820 is an extended radio galaxy with a quite unusual morphology, featuring two pairs of radio lobes. Such sources,
called double–double radio galaxies, constitute a very rare class of extragalactic radio sources. Furthermore, the extended
radio structure of this source shows an X-shape form. According to a much likely scenario, such a morphology is due to interrupting
nuclear activity in its central active galactic nucleus. Interestingly, the host of this source is a near-distance bright
galaxy named CGCG 292-057, which is clearly disturbed, with tidal features and shells as plausible signs of a recent merger. 相似文献
25.
26.
Filiz Bilgili Hans-Jürgen Götze Roman Pašteka Sabine Schmidt Ron Hackney 《International Journal of Earth Sciences》2009,98(3):571-583
An unsolved problem of regional importance for both the evolution and structure of the Northwest German Basin is the existence
or non-existence of the so-called Bramsche Massif. Explaining the nature of this massif and the cause of a related strong,
positive Bouguer anomaly (Bramsche Anomaly) is critical. In the study described here, we tested an existing “intrusion model”
against a newer “inversion model” in the southern Northwest German Basin. In the intrusion model, the strongly-positive Bouguer
anomaly represents the gravity effect of an intrusion at depths between 6 and 10 km. More recent interpretations invoke tectonic
inversion rather than intrusion to explain increased burial and the low level of hydrocarbon maturity found in boreholes.
We tested these different interpretations by constructing 3D forward density models to 15 km depth. The intrusion model was
updated and adjusted to incorporate recent data and we also modelled pre-Zechstein structures using different scenarios. The
final model has a very good fit between measured and modelled gravity fields. Based on currently available seismic and structural
models, as well as borehole density measurements, we show that the positive Bouguer anomaly cannot be modeled without a high-density,
intrusive-like body at depth. However, further in-sight into the crustal structures of the Bramsche region requires more detailed
investigations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
27.
Vladimir Yu. Semenov Josef Pek Antal Ádám Waldemar Jóźwiak Boris Ladanyvskyy Igor M. Logvinov Pavel Pushkarev Jan Vozar 《Acta Geophysica》2008,56(4):957-981
In the years 2001–2003, we accomplished the experimental phase of the project CEMES by collecting long-period magnetotelluric
data at positions of eleven permanent geomagnetic observatories situated within few hundreds kilometers along the south-west
margin of the East European Craton. Five teams were engaged in estimating independently the magnetotelluric responses by using
different data processing procedures. The conductance distributions at the depths of the upper mantle have been derived individually
beneath each observatory. By averaging the individual cross-sections, we have designed the final model of the geoelectrical
structure of the upper mantle beneath the CEMES region. The results indicate systematic trends in the deep electrical structure
of the two European tectonic plates and give evidence that the electrical structure of the upper mantle differs between the
East European Craton and the Phanerozoic plate of west Europe, with a separating transition zone that generally coincides
with the Trans-European Suture Zone. 相似文献
28.
This publication is a contribution to discussion on the geometry and petrography of the rock complex responsible for the Carpathian
conductivity anomaly. We analysed arguments showing that this anomaly is caused by induction in the sedimentary basin, and
make a critical review of various data to find out whether the good conductivity is connected with a rock complex containing
graphite or mineralized water. We conclude that a more likely mechanism is the ionic one, i.e., the existence of fluids, although
a final decision can only be made on the basis of deep drillings. 相似文献
29.
西藏羊卓雍湖流域近45 年气温和降水的变化趋势 总被引:4,自引:0,他引:4
利用西藏羊卓雍湖流域气象、水文观测站1961-2005 年逐月的平均气温、降水量等资 料, 分析了近45 年流域气温、降水的年际和年代际变化特征和异常年份, 以及羊湖水位变化趋势及影响因子, 结果表明: 近45 年流域年平均气温以0.25 oC/10a 的速率显著升高, 增温主要表现在秋、冬季。近25 年, 流域平均降水量除冬季呈减少趋势外, 其他各季节表现为显 著的增加趋势, 增幅为11.4~30.0 mm/10a, 夏季增幅最大; 年降水量以54.2 mm/10a 的速率明显增加。20 世纪60 年代至90 年代, 除夏季外, 其他3 季表现为逐年代增温趋势。在夏季, 降水量除80 年代偏少外, 其他3 个年代偏多; 而冬季相反, 80 年代降水偏多, 其他3 个年代偏少。流域年平均气温异常偏高年出现过3 次, 且发生在20 世纪90 年代末至21 世纪初; 60 年代后期和70 年代初降水多异常年份。自1997 年发电以来, 降水量呈增加趋势, 流域平均降水量达409.7 mm, 明显高于平衡降水量, 水位呈较明显的上升趋势。降水增多、日照减少, 以及气温明显升高、冰雪融水增加是造成水位上升的主要原因。 相似文献
30.
Visual observations of 1995 Perseid meteor stream made by Polish astronomy amateurs are reported. Using this material we obtained new accurate points in the activity profile during maximum. The Zenithal Hourly Rates (ZHRs) for the whole period of activity are presented. We also discuss the magnitude, the colour and the velocity distributions of Perseids. 相似文献