榆树地震台地电场观测系统运行评价     

张可佳  赵卫星  朱伟楠  李宁  吕晨阳  王宇 《地震地磁观测与研究》2015,(2):84-90

详细介绍榆树地震台地电场观测系统的运行状况,从数据完整率、静日、扰日变化形态以及相关系数、差值等方面对观测系统运行进行综合评价,结果表明:榆树地震台地电场观测系统运行稳定可靠,能够记录到震前地电场异常变化,可以为地震预测预报研究提供一定依据。  相似文献   

科尔沁沙地植物功能性状的尺度变异及关联   总被引：1，自引：1，他引：0  

周欣  左小安  赵学勇  刘川  吕朋 《中国沙漠》2016,36(1):20-26

调查了科尔沁沙地流动沙丘、半固定沙丘和固定沙丘18个样地的物种组成,测定了28种植物的叶面积(LA)、比叶面积(SLA)和叶干物质含量(LDMC)等3个植物功能性状,并用性状梯度分析法对3个功能性状在群落水平上的变化进行了分解,研究了沙丘固定过程中的植物功能性状的尺度变异及其与生境变化的关系。结果表明:(1)随着沙丘的固定,群落平均LA逐渐增大,群落平均SLA及LDMC在半固定沙丘上最小;(2)群落平均SLA的生态位宽度随着沙丘固定程度依次减小,流动、半固定沙丘植物群落的适应能力较固定沙丘更强;(3)沙丘固定过程中物种性状值的变化与群落内共生植物种性状间变异的关联相比于群落间性状的变异更密切。沙丘固定导致了物种LA与LDMC较强的正相关关系,两性状在群落间的依赖性比群落内的强。物种在群落内和群落间采取不同的策略来适应沙丘固定过程生境的变化。  相似文献   

科尔沁沙地不同沙地景观区植被指数对水热因素响应   总被引：1，自引：1，他引：0  

黄海涛  常学礼  岳喜元  吕德燕 《中国沙漠》2016,36(1):40-49

在全球气候变化背景下,不同尺度下植物对环境条件的响应机制是生态学研究的核心。为了更好理解不同沙地景观区域植被指数(NDVI)对气象水热环境因子的响应机制,以2000-2013年7-9月MODIS遥感影像为数据源,采用3S空间分析技术和通径分析方法,对科尔沁沙地围封保护区、人工造林固沙区和流动沙丘区等3种景观类型区NDVI的变化趋势和影响其变化的同期气象水热因子年降水、关键期降水、关键期最大一次性降水、重要期降水、年均温、关键期均温、关键期最高气温、关键期最低气温等8个因素进行了分析。结果表明:不同景观类型区NDVI整体上呈现增长的态势。降水的影响明显高于气温,且降水主要起正相关作用,气温主要起负相关作用。促进沙地围封保护景观区NDVI增长的气象因子是关键期降水,决策系数最大且为正(0.445);人工造林固沙景观区受到人工造林更新和农业开垦的影响,削弱了水热条件对NDVI的影响,相比较而言,重要期降水影响较大;流动沙丘景观类型区主要受到关键期气温极值的影响,其他因子影响不显著。  相似文献   

Impacts of Climate Change on Growth Period and Planting Boundaries of Spring Wheat in China under RCP4.5 Scenario     

Sun Zhen  Jia Shaofeng  Lv Aifeng  Jesper Svensson  Gao Yanchun 《资源与生态学报(英文版)》2016,7(1):1-11

This article contributes to research on how climate change will impact crops in China by moving from ex-post empirical analysis to forecasting. We construct a multiple regression model, using agricultural observations and meteorological simulations by GCMs, to simulate the possible planting boundaries and suitable planting regions of spring wheat under RCP4.5 scenario for the base period 2040s and 2070s. We find that the south boundary of possible planting region for spring wheat spreads along the belt: south Shandong-north Jiangsu-north Anhui-central Henan-north Hubei-southeast Sichuan-north Yunnan provinces, and will likely move northward under RCP4.5 scenario in 2040s and 2070s, resulting in the decrease of possible planting area in China. Moreover, the sowing and harvest date of spring wheat in the base period shows a gradually delayed phenomenon from the belt: south Xinjiang - Gansu, to the Tibet Plateau. As a result, the growth period of spring wheat in China will shorten because of the impacts of climate change. These results imply that a variety of adaptations measures should be set up in response to changing climatic conditions, including developing the planting base for spring wheat, restricting the planting area of spring wheat in sub-suitable areas at risk while expanding the planting area of optimal crops.  相似文献   

Identifying sources and hazardous risks of heavy metals in topsoils of rapidly urbanizing East China   总被引：3，自引：0，他引：3  

Yang Liu  Zongwei Ma  Jianshu Lv  Jun Bi 《地理学报(英文版)》2016,26(6):735-749

With rapid economic and social development, soil contamination arising from heavy metals has become a serious problem in many parts of China. We collected a total of 445 samples (0–20 cm) at the nodes of a 2 km×2 km grid in surface soils of Rizhao city, and analyzed sources and risk pattern of 10 heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn). The combination of Multivariate statistics analysis and Geostatistical methods was applied to identify the sources and hazardous risk of heavy metals in soils. The result indicated that Cr, Ni, Co, Mn, Cu, and As were mainly controlled by parent materials and came from natural sources. Cd and Hg originated from anthropogenic sources. Pb and Zn, belonging to different groups in multivariate analysis, were associated with joint effect of parent materials and human inputs. Ordinary Kriging and Indicator Kriging suggested that single element and elements association from the same principal components had similar spatial distribution. Through comprehensive assessment on all elements, we also found the high risk areas were located in the populated urban areas and western study area, which could be attributed to the higher geological background in the western part and strong human interference in the eastern part.  相似文献   

Migration of induced-infiltration stream water into nearby aquifer due to a transverse horizontal well in loess areas     

Wei Wang  Jing Lv  Donghui Xu  Lingbo Li  Yike Jia 《Environmental Earth Sciences》2017,76(16):572

Analysis of the migration paths of stream water introduced into a transverse horizontal well is important to better understand the interactions between streams and aquifers. This paper presents a method of using particle-tracking techniques to evaluate the transport of stream water that infiltrates through a transverse horizontal well that runs transverse to a stream and extends from the stream banks. By conceptualizing the horizontal well as a discrete pipe network, MODFLOW is coupled with the pipe flow equations that govern the movement of water in the horizontal well, and this coupled seepage-pipe flow model is used to calculate the transient groundwater flow field. MODPATH is then used to record the locations of each of the water particles from the interface between the stream and the aquifer. The path lines, travel times, influence zones and the production of infiltrated stream water are determined to depict the migration process. The results suggest that the infiltrated stream water that originates from different stream transects located upstream and downstream from the horizontal well has different migration characteristics, as does the infiltrated stream water coming from different locations on the same stream transect. Eventually, the pumpage of the horizontal well consists partly of the infiltrated stream water and groundwater inflow from the upstream model boundary. The groundwater enters the horizontal well through the two end segments of the horizontal well, and the infiltrated stream water enters the middle segment of the well. The pumped water is still a mixture of infiltrated stream water and groundwater, even if the pumping lasts for a long period. The hydrochemistry of the infiltrated stream water cannot be simply used to evaluate the hydrochemistry of the water pumped from a transverse horizontal well.  相似文献   

2010年1月24日山西河津-万荣Ms4.8地震特征   总被引：2，自引：0，他引：2  

宋美琴  李斌  吕芳  刘素珍  王秀文  梁向军 《地震地磁观测与研究》2012,33(1):18-22

分析2010年1月24日山西河津-万荣Ms4.8地震序列特征,利用P波初动及振幅比和波形反演CAP两种方法计算震源机制解,结合本次地震的地质构造和历史地震活动背景、震源机制、余震分布、极震区长轴方向等分析,结果表明,隐伏的西辛封断裂为发震构造的可能性较大.  相似文献   

The Neoproterozoic continental rift magmatism of the eastern Jiangnan orogen: new evidence from the mafic sheets in northern Zhejiang Province,South China     

Xiao-Xiong Ma  Chao Zhou  Qing Lv  Hong-Yan Gu  Wei-Wei Wu 《International Geology Review》2017,59(7):829-844

Massive mafic sheets were recently recognized intruding the Neoproterozoic strata in Fuyang area, eastern Jiangnan orogen. Geochronological, geochemical, and isotopic studies were carried out to understand their mantle source, crust–mantle interaction, and tectonic setting. LA-ICP-MS U-Pb zircon data indicate that the sheets were generated at 808 ± 7 Ma. The mafic sheets consist of two groups: high Ti and low Ti. They are enriched in light rare earth elements (LREE; 3.3–5.3 ppm) and show negligible Eu anomalies (δEu = 0.77–1.12). They also have strong large-ion lithophile element (LILE; Sr, K, Rb, Ba) enrichment, moderately strong high-field-strength element (HFSE) enrichment (except for Nb-Ta depletion), and positive εNd(t) (5.1–9.1). Geochemical and isotopic data indicate that the mafic sheets were generated from a depleted asthenospheric mantle source. The high-Ti mafic sheets have higher HFSE contents and less Nb-Ta depletion than the low Ti series, indicating a lower degree of partial melting and crustal contamination. The mafic sheets grew in a within-plate setting, concurrent with the ~820–750 Ma rifting events in the eastern Jiangnan orogen. They are likely related to the breakup of the Rodinia supercontinent.  相似文献   

磴口县景观格局演变特征及生态网络构建   总被引：2，自引：0，他引：2  

于强  岳德鹏  张启斌  吕奇  李宁  侯宏冰 《中国沙漠》2017,37(3):601-609

城市生态基础设施是城市可持续发展的基础,西部干旱区生态脆弱性大,县域尺度的生态基础设施网络是保证干旱区城市稳定与发展的重要保障。在快速城市化的背景下,选择西部典型生态脆弱区磴口县为研究区,运用景观格局指数、景观转移网络及核密度分析等方法,分析景观格局演变,在此基础上确定生态源地并分级,基于Cost Path模型提取生态廊道与生态节点,构建城市化背景下基于景观格局演变的磴口县生态基础设施网络。结果表明：2014年磴口县域景观破碎化程度高,景观生态流流动性差,城市与建设用地、荒漠灌木林地、耕地、沙漠之间的转移情况决定了磴口县整体景观变化的特征,2001-2014年共存在28种景观转移关系;基于Cost Path模型构建的县域尺度生态基础设施优化网络共包含391块生态源地、47 466条生态廊道和799个生态节点。针对干旱区构建的县域尺度的城区防护型生态网络,能够为磴口县城市化发展提供重要保障,对干旱区城市生态规划具有重要的参考价值。  相似文献   

Experimental study on settling velocity of soil particles in dredged slurry     

Nan Zhang  Wei Zhu  Hongtao He  Yiyan Lv  Shengwei Wang 《Marine Georesources & Geotechnology》2017,35(6):747-757

Studying sedimentation and consolidation of dredged slurry has significant implications to the design of storage yard and subsequent ground improvement. In this study, settling velocity of soil particles in dredged slurry during sedimentation and consolidation processes was investigated using an improved multilayer extraction sampling (MES) method. A series of sedimentation column tests were performed on dredged slurry with three different initial water contents. Distributions of volume of soil particles and density of dredged slurry were first obtained by the MES method, settling velocity of soil particles was then calculated by volume flux function approach. It was found that the density and velocity inflection points can be used to distinguish the settling zone and the consolidation zone. The experimental results reveal that the velocity of soil particles was quite low and monotonically decreased with sedimentation height at low initial water content throughout the whole test period, whereas it was increased at 0–1 hours and almost remained constant at 1–7 hours in the settling zone at high initial water content. The effects of initial water content on sedimentation and consolidation mode of dredged slurry and the settling velocity of soil particles were discussed. The relationship between settling velocity of soil particles and particle diameter was also studied. It is indicated that the measured velocity of soil particles was much lower than that calculated by the Stokes equation, and it was related to 0.4881–0.5906 order of particle diameter at 0–1 hours and 0.1117–0.1825 order of particle diameter at 1–7 hours for the test slurries.  相似文献