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871.
872.
The species diversity at the regeneration stage, inflenced by different water levels, is important for community composition in the later growing season. Regeneration diversity of Carex lasiocarpa community under different water levels was studied at two stages, recruitment and adult, in the Sanjiang Plain, Heilongjiang Province, China. The results showed that, at the two growing stages, important value of C. lasiocarpa population and species richness of the community decreased with the increasing water level, while the Simpson and Shannon-Wiener diversity indexes and Pielou evenness index increased. Under different water levels, community diversities were higher at the recruitment stage, while population important values of C. lasiocarpa were higher at the adult stage. Indexes in vegetation evaluation must be chosen prudentially for successful restoration and effective management of wetlands, and especially for wetland restoration, the optimal time should be selected according to the restoration objectives and costs. 相似文献
873.
对我国东南陆缘地区的人工地震测深、大地电磁测深、重磁测量、地热测量、地学大断面编制以及天然地震的层析成像等大量深部构造研究结果作综合分析。地热异常、地壳内存在低速层和高导层、强烈地震频繁发生等现象说明,这一地区是现代构造运动的活动区。中国东南陆缘的现今应力场主压应力方向为NWW-SEE,认为是菲律宾板块对欧亚板块的挤压,以及冲绳海槽的扩张等联合作用的结果。因此,这一地区地壳运动的驱动力是太平洋板块和菲律宾板块向欧亚板块推挤产生的。 相似文献
874.
云南省单台地震预报6年报准了12次5.2~7.3级地震。总结了反映孕震过程的矢量凹形、应力凹形、地电凹形等3种凹形震兆,阐述了水汞、水氡突跳,形变相关系数和地磁最大相关系数等前兆图像及其预报作用。认为:按照以场求源的思路,追踪孕震过程,是提高地震预报水平的有效途径。 相似文献
875.
In 2008,a green tide broke out before the sailing competition of the 29th Olympic Games in Qingdao.The causative species was determined to be Enteromorpha prolifera (Ulva prolifera O.F.Müller),a familiar green macroalga along the coastline of China.Rapid accumulation of a large biomass of floating U.prolifera prompted research on different aspects of this species.In this study,we constructed a nonnormalized cDNA library from the thalli of U.prolifera and acquired 10 072 high-quality expressed sequence tags ... 相似文献
876.
In this study,we evaluated the anti-proliferative activity of phlorotannins derived from brown algae Laminaria japonica Aresch extracts on the human hepatocellular carcinoma cell (BEL-7402) and on murine leukemic cells (P388) by MTT assay.Cells were incubated with 100 μg/mL of the phlorotannin extract (PE) for 48 h.The inhibitory rate of PE on BEL-7402 and P388 cells was 30.20±1.16% and 43.44±1.86%,respectively,and the half-inhibitory concentration of PE (IC50) on P388 and BEL-7402 cells was 120 μg/mL and >... 相似文献
877.
Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages,and the sediment sources and depositional dynamics of the environment reconstructed.The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea.Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor),the core might have previously been divided into th... 相似文献
878.
To reconstruct the productivity changes for the last 10 500 a in the northeastern East China Sea (ECS),biogenic compounds (such as carbonate,organic carbon and opal),marine micropaleontological fossils (planktonic foraminifera,benthic foraminifera,radiolarian and silicoflagellate) and the compositional characters of benthic foraminifera fauna analyses were carried out on a sediment core DOC082 obtained from the western slope of Okinawa Trough (29°13.93'N,128°08.53'E;1 128 m water depth).The long-term changes of biogenic and micropaleontological proxies display some similarities through the last 10 500 a,which show three different phases:lower values are recorded during the early and middle Holocene (before about 4 000 a BP),followed by an abrupt and remarkable increase at about 4 000 a BP,the late Holocene (after about 3 000 a BP) is characterized by continuously high values.The multi-proxy data of paleoproductivity and percents of benthic foraminifera genera (Uvigerina and Bulimina) show that during the early and middle Holocene (10 500-4 000 a BP) productivity was relatively low with a sudden and distinct increase at about 4 000 a BP,and the late Holocene (3 400-0 a BP) is marked by significantly higher productivity.Also,the radiolarian-based sea surface temperature (SST) records reveal a distinct decline in SST in the late Holocene after 3 200 a BP,very different from the early and middle Holocene.For the last 3 000 a,the enhanced biological productivity and distinctly lower SST indicate a major change of oceanographic conditions in the northeastern ECS.These marine environmental anomalies are consistent with other paleoclimatic records for the late Holocene in the Chinese continent and its surrounding regions.After analyzing the mechanisms of modern productivity and SST changes in the northeastern ECS,and based on the climatic anomalies in the Chinese continent and variations in the Kuroshio Current during modern El Nio periods,we suggest that the anomalous environmental conditions in the northeastern ECS may imply intensified El Nio activity during the late Holocene. 相似文献
879.
王克林 《中国地理科学(英文版)》1998,(3)
I.INTRODUCTIONItisgeneralyacceptedthatthedegradationofrenewableresourcesandfragileenvironmentsindevelopingcountriesisbecomin... 相似文献
880.
利用CitesSpace软件对1997-2017年DMSP/OLS夜间灯光数据进行知识图谱分析,梳理国内外研究热点与演化历史,发掘研究难点,为后来研究者提供方向。本文选取Web of Science 核心数据集数据库收录的文献,进行合著特征分析、关键词共现分析和文献共被引分析。结果表明:① 夜间灯光数据相关研究最活跃的国家、机构和作者分别是美国、中国科学院和Elvidge;② 社会经济条件估计(人口、人口密度和电力)和城市扩展变化监测一直是国内外研究的热点和前沿;③ 目前的研究难点是如何减少灯光溢出效应以及灯光过饱和现象对研究精度的影响;④ 研究学科交叉性强,涉及地理学、测绘科学与技术、应用经济学、社会学等领域。因此,未来的研究趋势主要表现在数据处理方法的优化、研究领域的拓展以及深化已有研究成果3个方面。 相似文献