2001-2015年间我国陆地植被覆盖度时空变化及驱动力分析          下载免费PDF全文

赵明伟  王妮  施慧慧  江岭  王春 《干旱区地理》2019,42(2):324-331

本文基于MODIS-NDVI遥感数据反演计算了我国陆地2001—2015年地表植被覆盖度的空间分布，讨论了植被覆盖度的时空变化规律，分析了影响植被覆盖度近十几年来动态变化的主要驱动因素。研究结果表明：我国陆地植被覆盖度从2001—2015年，植被覆盖度总体上呈增加趋势，其中淮河流域、华北平原地区、以及黄土高原地区增加趋势显著。根据植被覆盖度在时间序列上的变化特征，可将其变化类型分为持续增长型、先减小后增长等六种类型，其中农业种植区基本为一直增长型，而主要森林覆盖区，特别是西南地区的植被覆盖度在研究时段内表现出波动性的变化特征。降水是驱动华北平原北部，内蒙古，以及西北大部分区域植被覆盖度动态变化的重要因素，东北、青藏高原等地区植被覆盖度受温度的影响较大，而在中国东南沿海地区，光照条件是影响该区域植被覆盖度的主要因素。  相似文献   

川西甲基卡矿床外围中酸性侵入岩LA-ICP-MS锆石U-Pb年龄及地球化学特征     

李名则  秦宇龙  赵春  詹涵钰  周雄  孙光银 《中国地质调查》2020,7(5):1-9

在川西甲基卡矿床外围新发现了建巴村中酸性侵入岩体,为了探讨其形成时代、成岩构造背景及其成矿条件,开展了LA-ICP-MC锆石U-Pb年代学和地球化学特征研究。结果表明: 该岩体的结晶年龄为(211.8±1.0) Ma; 岩石属于钙碱性-高钾钙碱性准铝质中酸性侵入岩系列,具有I型花岗岩类的特征,其物质来源可能为壳源物质与幔源物质部分熔融。地球化学特征表明其形成于后碰撞环境,与此时期内川西地区的区域性岩浆活动相对应。建巴村岩体的构造位置及岩浆活动特征指示其可能不具备形成伟晶岩矿床的条件。  相似文献   

Binary Star Fractions from the LAMOST DR4     

Zhi-Jia Tian  Xiao-Wei Liu  Hai-Bo Yuan  Bing-Qiu Chen  Mao-Sheng Xiang  Yang Huang  Chun Wang  Hua-Wei Zhang  Jin-Cheng Guo  Juan-Juan Ren  Zhi-Ying Huo  Yong Yang  Meng Zhang  Shao-Lan Bi  Wu-Ming Yang  Kang Liu  Xian-Fei Zhang  Tan-Da Li  Ya-Qian Wu  Jing-Hua Zhang 《天文和天体物理学研究(英文版)》2018,(5)

Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multiepoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions,are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with Teff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy.  相似文献   

乌鲁木齐公共交通基础设施对低收入群体就业的影响研究     

张纯  程志华  于晓萍  王亚群  沈忱 《地理科学进展》2020,39(1):111-119

中国西部城市在大规模、快速度和高投资的交通基础设施推进的同时,审视其建设的社会经济效益就显得尤为重要。尤其对于城市低收入群体来说,公共交通基础设施投入是否能对提升就业水平、提升整体生活品质产生积极作用,值得规划者和决策者关注。论文基于乌鲁木齐2014年居民交通出行调查数据,采用带有交叉变量的多元线性回归和多元Logit回归方法,考察快速公交(Bus Rapid Transit, BRT)对于提升低收入群体就业可达性和通勤满意度的影响。分析结果显示：在就业可达性方面,低收入、男性和拥有住房产权者的通勤时间更长,距离BRT车站越近则通勤时间更短,私家车出行的通勤时间更长;在通勤满意度方面,低收入群体的通勤满意度水平更低,距离BRT车站近、选择私家车出行的通勤满意度水平更高。分析也表明,通勤时间短,通勤满意度水平不一定就高。这些研究结果表明,整体上公共交通基础设施建设对于提升就业可达性和满意度有着积极的带动作用,但个体经济社会属性的差异影响也不可忽视。研究乌鲁木齐公共交通基础设施对就业可达性和满意度的影响,有助于帮助西部城市制定提升低收入群体整体就业水平的公共政策,尤其对于促进地方就业稳定和带动区域经济发展有重要意义。  相似文献   

GIS: an introduction to mapping technologies     

Yongwan Chun 《International journal of geographical information science》2020,34(7):1500-1501

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Effects of Anthropogenic Disturbance on Sediment Organic Carbon Mineralization Under Different Water Conditions in Coastal Wetland of a Subtropical Estuary     

Xiaojie Mou  Xingtu Liu  Zhigao Sun  Chuan Tong  Jiafang Huang  Siang Wan  Chun Wang  Bolong Wen 《中国地理科学(英文版)》2018,28(3):400-410

The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P 0.001), and the interaction between human disturbance activities and water conditions was also significant(P 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil aquaculture pond sediment soil near the discharge outlet rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R~2 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.  相似文献   

鄂尔多斯块体西南缘地区震源机制解与构造应力场特征分析     

王莹  赵韬  刘春  冯希杰 《地震地磁观测与研究》2020,41(4):18-25

计算了2001年1月至2018年9月鄂尔多斯块体西南缘地区（33°—38°N，103°—109°E）M_L≥3.0地震的震源机制，分析了该区域震源机制解特征，在此基础上，采用平均矩张量技术反演了该区域的构造应力场特征。结果表明，研究区震源机制类型以走滑型和逆冲型为主，其空间分布基本与区域构造动力背景和断裂性质一致，少量不符合区域构造性质的震源机制则反映了局部地质构造的复杂性。区域构造变形主体为NE向压缩，NW向相对扩张，反映了青藏高原块体对鄂尔多斯块体的直接作用。  相似文献   

Estimating aboveground biomass using Pléiades satellite image in a karst watershed of Guizhou Province,Southwestern China     

Yin-ming Guo  Jian Ni  Li-bin Liu  Chun-zi Guo  Xin Xu  Qiao-lian Zhong 《山地科学学报》2018,15(5):1020-1034

Biomass in karst terrain has rarely been measured because the steep mountainous limestone terrain has limited the ability to sample woody plants.Satellite observation, especially at high spatial resolution, is an important surrogate for the quantification of the biomass of karst forests and shrublands. In this study, an artificial neural network(ANN) model was built using Pléiades satellite imagery and field biomass measurements to estimate the aboveground biomass(AGB) in the Houzhai River Watershed, which is a typical plateau karst basin in Central Guizhou Province, Southwestern China. A back-propagation ANN model was also developed.Seven vegetation indices, two spectral bands of Pléiades imagery, one geomorphological parameter,and land use/land cover were selected as model inputs. AGB was chosen as an output. The AGB estimated by the allometric functions in 78 quadrats was utilized as training data(54 quadrats, 70%),validation data(12 quadrats, 15%), and testing data(12 quadrats, 15%). Data-model comparison showed that the ANN model performed well with an absolute root mean square error of 11.85 t/ha, which was 9.88%of the average AGB. Based on the newly developed ANN model, an AGB map of the Houzhai River Watershed was produced. The average predicted AGB of the secondary evergreen and deciduous broadleaved mixed forest, which is the dominant forest type in the watershed, was 120.57 t/ha. The average AGBs of the large distributed shrubland,tussock, and farmland were 38.27, 9.76, and 11.69 t/ha, respectively. The spatial distribution pattern ofthe AGB estimated by the new ANN model in the karst basin was consistent with that of the field investigation. The model can be used to estimate the regional AGB of karst landscapes that are distributed widely over the Yun-Gui Plateau.  相似文献   

地闪对崇明地震台地球物理观测的干扰     

朱培育  戴乐翔  张艺  魏薇  赵俊香  朱佳苗  施俊杰  毕波  倪友忠 《地震地磁观测与研究》2018,40(1):91-95

通过对比崇明地区地闪及崇明地震台地球物理观测资料，发现受地闪引起的电磁场变化的直接作用或对仪器元件的间接作用，地磁、地电、电磁扰动和水位观测干扰比例较高，干扰幅度与地闪距离及形成的电流强度有关。具体干扰形态如下：①对电磁扰动干扰表现为单向突跳和测值的整体抬升；②对地磁测项干扰表现为正负方向的单点突跳；③对大地电场干扰表现为大幅震荡；④对水位观测干扰表现为大幅突跳。  相似文献   

短期重现性地磁日变化感应电流集中分布与地震关系初步研究     

冯志生  姜楚峰  冯丽丽  李军辉  戴勇  黄颂  姚丽  章鑫  袁桂平  倪晓寅  戴苗  李鸿宇 《中国地震》2020,36(3):502-516

通过分析台站之间地磁垂直分量日变化相关性,研究中国大陆南北带地区90°E～110°E,2009～2018年地磁日变化感应电流线状集中分布现象与M_S≥6.0地震关系。统计发现,我国每月平均出现约2次感应电流集中分布现象,且10天左右内有原地重复出现现象——感应电流集中分布重叠异常,原地重现的集中分布感应电流日期间隔一般在10天左右以内,原地重现日期一般不连续,重现次数一般仅有2次。研究发现,我国南北带2009～2018年共出现重叠异常23次,20次重叠异常出现后18个月内重叠段发生M_S≥6.0地震,对应率高达87%,地震基本发生在重叠段端部250km以内,重叠段发生2次M_S≥6.0地震的比例较低,约35%;重叠段2个端部均发生M_S≥6.0地震的比例极小,仅约9%。部分重叠段走向与已经发现的上地幔和地壳高导带埋深走向基本一致,推测重叠异常发生在上地幔和地壳高导带附近,是来自上地幔和地壳内高导带附近的地震异常信息。目前已知,中国大陆强地震主要发生在上地幔高导层的隆起区一带及其壳内高导层发育地区,深部电性测深结果表明,大震易于发生在电导率急剧变化的梯度带,但这些地区何时发生地震还未得知,本文发现的重叠异常解释了这些地区1～2年内是否发生地震这一问题。  相似文献