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Matt King 《Al-Masaq: Islam & the Medieval Mediterranean》2017,29(3):221-234
The release of the Old World Drought Atlas (OWDA) in November 2015 provides historians with an unprecedented glimpse into the climate of the medieval world. Through the careful examination of tree-ring data provided by the OWDA, historians can better gauge how the environment affected the course of medieval Mediterranean history, particularly in times and places where textual data is sparse, such as North Africa. The case studies of the Norman conquest of the coast of Ifrīqiyya in the 1140s and the invasion by the Banū Hilāl in the mid-eleventh century show the utility of the OWDA for gaining a better understanding the medieval Mediterranean. In particular, OWDA data shows that the arrival of the Banū Hilāl into Ifrīqiyya coincided with a period of extended drought that is not documented in the written sources and suggests that increased competition for scarce resources was instrumental to their entrance into the region. 相似文献
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研究了干旱胁迫时不同抗旱性大豆品种苗中游离脯氨酸积累与大豆抗旱性的关系．结果表明，随着水分胁迫的加强，游离脯氨酸的累积显著增加，且抗旱性强的品种在干旱胁迫的前期游离脯氨酸累积量小于抗旱性弱的品种，但深度胁迫时其累积量则明显大于抗旱性弱的品种．脯氨酸的积累可作为大豆抗旱性的筛选指标． 相似文献
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卡德尔·阿布都热西提 《喀什师范学院学报》2008,29(6):57-59
对不同玉米品种进行干旱处理,对叶片含水量、土壤含水量、叶片质膜透性进行测定．结果表明,土壤干旱胁迫条件下,玉米叶片含水量下降,叶片质膜透性上升;随着胁迫时间的延长,即土壤含水量的降低,叶片质膜透性不断的增加,其中新实1号的变化幅度最小,而叶片含水量则随之不断的减少,与叶片质膜透性的结果相符．这说明幼苗期新实1号的抗旱能力较强．因此,对叶片含水量、土壤含水量、叶片质膜透性的测定可以作为幼苗期抗旱鉴定的重要指标． 相似文献
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Kiumars Zarafshani Marjan J. Gorgievski Ghossein H. Zamani 《The Journal of Agricultural Education and Extension》2013,19(1):69-80
Abstract This paper reports the results of a study to understand why some New Zealand dairy farmers are changing from twice-a-day (TAD) to once-a-day (OAD) milking. Increasing herd size, unavailability of suitable labour and changing lifestyle expectations from farmers and their staff have led some to explore OAD milking as a means of alleviating these issues. A convergent interviewing process was used with 21 dairy farmers who had all adopted OAD milking. A marketing approach, based on consumer behaviour theory and farming systems theory, was used to classify farmers into segments based on their different reasons for adoption. Six segments were identified, viz., herd expansion, time needed to build capital, decreasing labour, increasing labour flexibility, feed shortfalls, and herd health, motivating farmers to adopt OAD milking. Farmers in some segments such as herd expansion and feed shortfalls indicated that they were less likely to be long-term adopters than those in the other segments. Farmers interviewed unanimously understood that OAD milking led to reduced milk yield but were generally prepared to tolerate this to achieve their short-term or long-term goals. 相似文献
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Ch Surendhar Reddy A. Prasad Babu B. P. Mallikarjuna Swamy K. Kaladhar N. Sarla 《Journal of Zhejiang University. Science. B》2009,10(2):133-141
Drought,flood,salinity,or a combination of these limits rice production.Several rice varieties are well known for their tolerance to specific abiotic stresses.We determined genetic relationship among 12 rice varieties including 9 tolerant to drought,flood,or salinity using inter-simple sequence repeat (ISSR) markers.Based on all markers,the nine tolerant varieties formed one cluster distinct from the cluster of three control varieties.The salt-tolerant varieties were closest to two flood-tolerant varieties,and together they were distinct from the drought-tolerant varieties.(GA)8 YG was the most informative primer,showing the highest polymorphic information content (PIC) and resolving power (Rp).The drought-,flood-,and salt-tolerant varieties grouped in three distinct clusters within the group of tolerant varieties,when (GA)8 YG was used.Sabita was the only exception.The two aus varieties,Nagina22 and FR13A,were separated and grouped with the drought-and flood-tolerant varieties,respectively,but they were together in dendrograms based on other primers.The results show that ISSR markers associated with (GA)8 YG delineated the three groups of stress-tolerant varieties from each other and can be used to identify genes/new alleles associated with the three abiotic stresses in rice germplasm. 相似文献
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近30年来,随着气候干暖化现象日趋严峻,旱灾对农业生产的影响愈加受到关注。本文以部门均衡理论为基础,构建了一个用于分析并预测区域干旱对全国主要农产品市场价格影响的模型。基于该模型,并辅以中国统计年鉴与中国农业年鉴统计数据,本文分析、预测了在华北地区发生不同程度旱灾情景下的我国8种主要农产品市场价格变化。研究结果表明,华北地区干旱会对全国主要农产品市场价格产生一定的影响,但影响程度普遍较低。即便是在严重干旱情景下,全国各主要农产品市场价格的增幅也不会超过3.59%,不会影响我国农产品市场的正常运行。本文探索的方法及其结论为评估干旱对我国农产品市场的影响、制订防灾减灾规划、确保区域乃至全国主要农产品供给安全提供了一定的决策参考价值。 相似文献
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以邵阳市15个雨量站逐月降雨资料为基础,采用适线法估计干旱历时和干旱烈度的分布函数,利用3种Archimedean Copula函数分别构建了两干旱特征变量之间的联合分布,并比较了3种Copula函数的拟合效果,最后分析了邵阳市干旱重现期的空间分布特征。结果表明：Copula理论能够为多变量干旱特征分析提供有效的研究途径,Archimedean Copula函数中的Gumbel—Hougaard Copula和Frank Copula函数较好地描述各站干旱特征变量之间的相互关系;适线法避免了基于数据估计分布函数参数的不合理性,使基于Copula函数的频率分析结果更客观可靠;区域干旱具有显著的空间分布特性,各站干旱程度差异较大。 相似文献
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抗旱剂浸种干旱胁迫发芽试验表明,浸种处理可以提高干旱条件下小麦的出苗率,增大根冠比,有助于小麦的苗期生长.浸种处理的平均效应以浸种4h出苗率最高,但品种与浸种时间存在互作,不同品种应选择不同的浸种时间. 相似文献
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北方农牧交错区降水过程的持续性特征与干旱发生趋势 总被引：3，自引：1，他引：2
过去50多年来,环境脆弱的北方农牧交错带中部区域增温明显且干旱频发,对生态系统和农牧民的生计造成极为严重的影响。认识该区域降水过程的持续性特征对准确预测未来可能面临的灾害事件及政策调整有重要意义。本文采用时序距平分析法与基于分形理论的重标极差分析法相结合的方式,详细分析了北方农牧交错带中部地区6个站点1956年-2009期间降水变化过程及其持续性特征。结果表明,研究区过去54年间的年降水量总体呈下降趋势,夏季降水量年际变化曲线与年降水量变化曲线基本一致,但春季降水量略有上升;在1年与5年时间尺度上,年降水量和各季节降水量变化均呈剧烈波动态势。值得注意的是,在5年时间尺度上,Hurst指数在整个研究区域上的平均值比其在1年时间尺度上的平均值更接近于1．0,即随着时间尺度的增大,降水过程的自相关性、持续性增强明显。在10年尺度上,研究区全年少水期的出现即距平值为负值的持续时间长约10年,而春季少水期出现的持续时间则可能长达20．30年。 相似文献