Impact factors identification of spatial heterogeneity of herbaceous plant diversity on five southern islands of Miaodao Archipelago in North China     

池源  石洪华  王晓丽  覃雪波  郑伟  彭士涛 《中国海洋湖沼学报》2016,34(5):937-951

Herbaceous plants are widely distributed on islands and where they exhibit spatial heterogeneity. Accurately identifying the impact factors that drive spatial heterogeneity can reveal typical island biodiversity patterns. Five southern islands in the Miaodao Archipelago, North China were studied herein. The spatial distribution of herbaceous plant diversity on these islands was analyzed, and the impact factors and their degree of impact on spatial heterogeneity were identified using CCA ordination and ANOVA. The results reveal 114 herbaceous plant species, belonging to 94 genera from 34 families in the 50 plots sampled. The total species numbers on different islands were significantly positively correlated with island area, and the average α diversity was correlated with human activities, while the β diversity among islands was more affected by island area than mutual distances. Spatial heterogeneity within islands indicated that the diversities were generally high in areas with higher altitude, slope, total nitrogen, total carbon, and canopy density, and lower moisture content, pH, total phosphorus, total potassium, and aspect. Among the environmental factors, pH, canopy density, total K, total P, moisture content, altitude, and slope had significant gross effects, but only canopy density exhibited a significant net effect. Terrain affected diversity by restricting plantation, plantation in turn influenced soil properties and the two together affected diversity. Therefore, plantation was ultimately the fundamental driving factor for spatial heterogeneity in herbaceous plant diversity on the five islands.  相似文献   

Mixing of Enriched Lithospheric Mantle-Derived and Crustal Magmas: Evidence from the Habo Cenozoic Porphyry in Western Yunnan     

XIA Bin  LU Ye  YUAN Yajuan  CHEN Weiyan  ZHANG Xiao  XU Chi  YU Shengrui  WAN Zhifeng 《《地质学报》英文版》2018,92(5):1753-1768

New zircon U–Pb ages, whole-rock geochemistry and zircon Hf isotopes from the Habo porphyry Western Yunnan, China, were determined to provide constraints on the timing of uplift of the Eastern Tibetan Plateau. The intrusive rocks consist of shoshonitic porphyry (syenite porphyry and monzonite porphyry). Zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating indicates coeval emplacement ages of ~35 Ma. The porphyries have alkaline affinities, enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) (e.g., Rb, Th, U, Pb), with depletion of high field strength elements (HFSEs) (e.g., Nb, Ti, Ta) and weak Eu anomalies. They display uniform Lu–Hf isotopic compositions with negative zircon εHf(t) values ranging from -3.9 to -0.6. The chemical characteristics of the syenite porphyries indicated that they most likely originated from the lower crust, with mantle-derived material involved in their generation. Geochemically, the monzonite porphyries are similar to the syenite porphyries; however, the lower MgO contents suggest that they were produced by different degrees of partial melting of the same lower crust source. Combined with the geochemical and isotopic data in this paper, imply that the alkali-rich porphyries of the Habo polymetallic deposit were derived from the partial melting of lower crust, enriched by mantle magma, formed in a conversion stage from stress extrusion (a strike-slip shear process) to local stress relaxation (a strike-slip pull-apart process) at the Ailaoshao tectonic zone.  相似文献   

Correction to: Assessing real options in urban surface water flood risk management under climate change     

Haixing Liu  Yuntao Wang  Chi Zhang  Albert S. Chen  Guangtao Fu 《Natural Hazards》2018,92(1):19-25

Windblown dust originating in China and Mongolia causes health effects and agricultural damage in its source areas and causes Asian dust events in Japan. An early warning system that could be combined with weather forecasts would be helpful in preventing serious damage. However, it is difficult to specify source areas of dust with current dust modeling systems because land surface information, including vegetation coverage and land surface soil water content, is inadequate. To find and monitor dust source regions, a semi-real-time dust erodibility map was developed based on MODIS satellite data that focuses particularly on the threshold wind speed in a target area of northeast Asia including China and Mongolia (35°–50°N, 75°–120°E). The mapping system incorporates satellite data on snow cover, areas of frozen soil, surface soil water content, and vegetation cover.  相似文献   

内蒙古白乃庙逆冲推覆构造特征及其地质意义   总被引：1，自引：0，他引：1  

周志广  张达  谷永昌  王果胜  李红英  於炀森  柳长峰  刘文灿 《大地构造与成矿学》2018,(1):1-17

白乃庙逆冲推覆构造自四子王旗北东的十二台向东经白乃庙、博日和延至化德地区,大致沿北纬42°线东西向延伸超过190 km。它发育于华北克拉通与其北侧的奥陶纪白乃庙岛弧带之间,成为华北克拉通与北缘增生带的构造界线,是一套较为典型的陆缘褶冲带。它表现为华北克拉通北缘的中-新元古界白云鄂博群向北逆冲于白乃庙群及其弧后盆地的上志留统徐尼乌苏组和顶志留统西别河组之上。根据构造变形解析并结合音频大地电磁测深资料(CSAMT),得出白乃庙逆冲推覆构造由一系列分支逆断层组成,并向深部于120~800 m处交汇成主底板断层,构成一套叠瓦式逆冲推覆构造,并发育规模不同的构造窗和飞来峰。根据构造窗与飞来峰之间的距离,提出逆冲位移量大于14 km。通过线理及褶皱枢纽统计,指出白乃庙逆冲推覆构造的逆冲方向为自南向北。依据逆冲岩席中发育的断夹块的叠置关系及构造岩的特征,认为其经历了两个期次的活动。对断裂带内同构造形成的包裹石英透镜体的白云母分别进行了Rb-Sr和Ar-Ar同位素测年,认为白乃庙逆冲推覆构造早期活动于450~410 Ma,是白乃庙岛弧带与华北板块碰撞的构造反映。白乃庙逆冲断层晚期活动于晚二叠世至早三叠世,是古亚洲洋最终闭合的构造表现,亦印证研究区经历了印支期构造运动。  相似文献   

Changes in air pollutants during the COVID-19 lockdown in Beijing:Insights from a machine-learning technique and implications for future control policy          下载免费PDF全文

Jiabao Hu  Yuepeng Pan  Yuexin He  Xiyuan Chi  Qianqian Zhang  Tao Song  Weishou Shen 《大气和海洋科学快报》2021,14(4):63-69

基于2015-2020年北京35个环境空气站和20个气象站观测资料,应用机器学习方法(随机森林算法)分离了气象条件和源排放对大气污染物浓度的影响.结果发现,为应对疫情采取的隔离措施使北京2020年春节期间大气污染物浓度降低了35.1％-51.8％;其中,背景站氮氧化物和一氧化碳浓度的降幅最大,超过了以往报道较多的交通站点.同时,2020年春节期间的气象条件不利于污染物扩散,导致多次霾污染事件发生.为进一步改善北京空气质量,未来需要优化减排策略.  相似文献   

GIS多准则的城市垃圾楼空间布局优化选址     

刘思君  靖常峰  杜明义  付艳丽  戴培培 《测绘科学》2018,(8):45-49

针对城市公共设施的传统选址方法较少考虑空间维度因素的问题,该文提出了基于地理信息系统(GIS)多准则的城市公共设施选址模型,利用GIS多准则技术基于空间维度分析了城市自然环境和人文要素等综合影响下的公共设施选址方法,并以城市垃圾楼选址为例进行了实例应用。实验结果表明:该方法不仅充分考虑了城市复杂的地理环境,还深度探究了影响城市公共设施选址的综合性因素。  相似文献   

参数优化DBSCAN算法的城管案件聚类分析   总被引：1，自引：0，他引：1  

伏家云  靖常峰  杜明义  付艳丽  戴培培 《测绘科学》2018,(8):135-140

针对DBSCAN算法参数对聚类结果具有较大的不确定性问题,该文提出了基于空间分析的参数优化思想:首先,基于Ripley’s K函数分析,实现自适应确定数据聚类范围EPS值;基于K-D树分析,实现自适应确定在Eps阈值内的点数量MinPts值;然后,基于以上参数的自适应确定思想,利用R语言编写了DBSCAN算法,进一步实现了数据的精确聚类。基于典型城市管理案件的实验结果表明:该方法充分考虑了空间数据统计特性,具有较好的适用性,聚类簇特征明显,聚类质量较高。  相似文献   

国产高分辨率遥感影像辐射质量改善方法研究     

任海艳  刘驰  韩昱  董忠亮  王欢 《测绘与空间地理信息》2018,(7):156-159

受制于光学器件的性能与观测环境的影响,国产高分辨率遥感影像通常存在条带噪声、光谱分辨率低、纹理不清晰等问题,给后续的自动化影像产品生产及目标解译工作带来极大的不利。本研究先后从去除条带噪声、对比度增强、边缘增强三个方面,对遥感影像进行质量改善,使遥感影像更好地为地理信息公众服务。以高分二号全色影像为实验数据,目视和定量评价结果均证实了本文算法的有效性。  相似文献   

Dynamic Response and Mechanical Behaviours of Geogrid for High Earth-rockfill Dams     

Zhu  Yalin  Ma  Chi  Tan  Kun  Chen  Juxiang  Wang  Yixian 《Geotechnical and Geological Engineering》2021,39(8):5479-5492

Geotechnical and Geological Engineering - Due to the complexity of the interaction between the geogrid and the soil interface in high earth-rock dams, the method of replacing the grid with steel...  相似文献   

华北平原与大同盆地原生高碘地下水赋存主控因素的异同          下载免费PDF全文

王雨婷  李俊霞  薛肖斌  田小伟  迟秀成 《地球科学》2021,46(1):308-320

原生高碘地下水在我国有广泛分布,为查明不同区域地下水碘赋存机理的异同,通过选取我国大同盆地以及华北平原为代表性区域,完成区域地下水样品系统性采集及水化学、碘形态测试工作,对区域地下水水环境及其演化特征完成详细刻画.结果表明:大同盆地地下水总碘含量为2.86~1 286 μg/L,华北平原地下水总碘含量为2.40~1 106 μg/L,分别约有50.0%及49.5%地下水碘含量超过（GB19380- 2016）《水源性高碘地区和高碘病区的划定》中界定的100 μg/L国家标准.地下水水环境特征表明,在大同盆地,第四纪河湖相沉积所形成的,富含有机质、偏碱性、还原性、Na-HCO₃型水环境,利于赋存于固相介质上的碘以碘离子的形式进入地下水中,沿地下水流向,富集于盆地中心排泄区;在华北平原,由第四纪6次海侵形成的冲湖积、海积松散沉积物中富含Na、Cl、I等元素,其偏碱性、还原性、Na-Cl型水环境及低水力坡度的平缓地形利于赋存在固相介质上的碘以碘离子的形式进入地下水,沿地下水流向富集于沿海排泄区.控制两个地区高碘地下水形成的相同因素是偏碱性及偏还原的地下水环境,且该环境下碘的主要赋存形态均为碘离子,但大同盆地高碘地下水形成主要受富有机质环境影响,而华北平原高碘地下水形成的主要受富碘的海相沉积控制.   相似文献