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Spatial distribution changes in major crops can reveal important information about cropping systems.Here,a new centroid method that applies physics and mathematics to spatial pattern analysis in agriculture is proposed to quantitatively describe the historical centroids of rice,maize and wheat in China from 1949 to 2014.The geographical centroids of the rice area moved 413.39 km in a 34.32° northeasterly(latitude 3.08°N,longitude 2.10°E) direction at a speed of 6.36 km/year from central Hunan province to Hubei province,while the geographical centroids of rice production moved 509.26 km in the direction of 45.44° northeasterly(latitude 3.22°N,longitude 3.27°E) at a speed of 7.83 km/year from central Hunan province to Henan province.The geographical centroids of the maize area and production moved 307.15 km in the direction of 34.33° northeasterly(latitude 2.29°N,longitude 1.56°E) and 308.16 km in the direction of 30.79° northeasterly(latitude 2.39°N,longitude 1.42°E),respectively.However,the geographical centroids of the wheat area and production were randomly distributed along the border of Shanxi and Henan provinces.We divided the wheat into spring wheat and winter wheat and found that the geographical centroids of the spring wheat area and production were distributed within Inner Mongolia,while the geographical centroids of winter wheat were distributed in Shanxi and Henan provinces.We found that the hotspots of crop cultivation area and production do not always change concordantly at a larger,regional scale,suggesting that the changing amplitude and rate of each crops' yield differ between different regions in China.Thus,relevant adaptation measures should be taken at a regional level to prevent production damage in those with increasing area but decreasing production. 相似文献
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针对测震台网定位存在偏差的问题,采用双差定位方法,对2008—2019年9月内蒙古测震台网及周边台站记录的内蒙古中西部地区4410个地震事件进行重新定位。研究表明,利用双差定位方法重新定位后地震分布更集中,更符合内蒙古中西部地区的地质构造特征,定位精度显著提高。 相似文献
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一般地说。试卷知识点的命题和布局似乎不成问题。过去的试卷在这一方面已经积累了一定的经验。在当前的形式下，如何使命题工作适应新形势的要求?如何进一步地提高试卷质量和命题技术?从学科考试来说，这是一个比较重要的、带有确定研究方向的问题。 相似文献
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鄂尔多斯盆地深层发育长城纪裂陷槽,但相关的圈闭类型和成藏条件不清。近期,在盆地北部杭锦旗地区发现了长城系砂岩潜山气藏,揭示该领域具有较好的勘探前景。通过最新的三维地震和钻井资料综合分析,结合区域构造演化阶段和典型气藏解剖,本次研究针对中元古界潜山圈闭的分布、类型及天然气成藏模式展开。结果表明：(1)研究区长城纪发育三个NW向裂陷槽,其中的独贵、蒋家梁裂陷槽受基底断裂反转活动影响,隆升剥蚀,形成低幅度的潜山隆起带;(2)残丘、隐丘及断丘型圈闭沿潜山隆起带呈带状分布,其中断丘型圈闭的闭合幅度最高;(3)潜山圈闭的成藏模式可分“上生下储”、“源储侧接”及“源外运移”等三种类型;(4)天然气藏分布受四个因素控制,其中烃源岩分布制约潜山气藏的分布范围;圈闭类型控制气藏规模与富集程度;断-缝发育程度控制储层物性及含气性;而侧向输导控制源外圈闭的成藏效率。因此,邻近煤系烃源岩的断丘型、残丘型圈闭将是研究区中元古界潜山勘探的首要目标。 相似文献
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