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Impact of seasonal water-level fluctuations on autumn vegetation in Poyang Lake wetland,China

Frontiers of Earth Science 2019年第2期13卷 398-409页

作者： Xue DAI Rongrong WAN Guishan YANG Xiaolong WANG Ligang XU Yanyan LI Bing LI Key Laboratory of watershed Geographic Sciences Nanjing Institute of Geography and LimnologyChinese Academy of SciencesNanjing 21000& China University of Chinese Academy of Sciences Beijing 100049China Jiangsu Second Normal University Nanjing 210013China

water level fluctuations (WLF) are natural patterns that are necessary for the survival of various plants,and WLF guarantee both the productivity and the biodiversity of wetlands.However,the underlying mechanisms of how changes in vegetation are linked to seasonal WLF remain unclear.Using vegetation and hydrological data from 1989 to 2009,we identified the key seasonal fluctuations and their impacts on vegetation in the Poyang Lake wetland by utilizing a tree-based hierarchical model.According to our results: 1) WLF in summer had significant impacts on both sedges and reeds.The severe summer floods promoted the expansion of sedges,while they inhibited the expansion of reeds;2) WLF in autumn also greatly impacted sedges,while reeds were severely affected in spring.Specifically,we found that low water levels in autumn led to the expansion of sedges,and low water levels in spring led to the expansion of reeds.The results were well corroborated through comparisons of the vegetation distribution patterns over the last two decades (i.e.,the 1990s and 2000s),which may shed light on corresponding water resource and wetland management.

关键词： wetland reeds sedges seasonal water-level fluctuations classification and regression tree model

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Fractal characterization of sediment particle-size distribution in the water-level fluctuation zone of the Three Gorges Reservoir, China

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Journal of Mountain Science 2019年第9期16卷 2028-2038页

作者： LI Jin-lin BAO Yu-hai WEI Jie HE Xiu-bin TANG Qiang Jean de Dieu NAMBAJIMANA Key Laboratory of Mountain Surface Processes and Ecological Regulation Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China Chongqing Key Laboratory of Earth Surface Processes and Environmental Remote Sensing in the Three Gorges Reservoir Area Chongqing 401331 China University of Chinese Academy of Sciences Beijing 100049 China Sustainable Agriculture Sciences Department Rothamsted Research North Wyke Okehampton Devon EX20 2SB UK

The combined effect of periodic water impoundment and seasonal natural flood events has created a 30 m high water-level fluctuation zone(WLFZ) around the Three Gorges Reservoir(TGR), China, forming a unique eco-landscape. Siltation, eutrophication, enrichment of heavy metals, and methane emissions in the WLFZ have been widely associated with sediment and soil particles generated from the upstream catchment or upland slopes. However, little attention has been paid to the complexity of sediment particle-size distributions in the WLFZ. In the present study, core samples(from a 345 cm thick sediment core from the base of the WLFZ), slope transect surface samples(across/up a WLFZ slope), and along-river/longitudinal surface samples(from the reservoir reaches) were collected. Laser granulometry and a volume-based fractal model were used to reveal the characteristics of sediment particle-size distributions. Results indicate that the alternation of coarse and fine particles in the sedimentary core profile is represented as a fluctuation of low and high values of fractal dimension(D), ranging from 2.59 to 2.77. On the WLFZ slope transect, surface sediment particles coarsen with increasing elevation, sand content increases from 3.3% to 78.5%, and D decreases from 2.76 to 2.53. Longitudinally, surface sediments demonstrate a downstream-fining trend, and D increases gradually downstream. D is significantly positively correlated with the fine particle content. We conclude that D is a useful measure for evaluating sediment particle-size distribution.

关键词： Spatial differentiation Sediment particle Fractal dimension water-level fluctuation zone Three Gorges Reservoir

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Preliminary study on coseismic step-like changes of water-level in the Dazhai well, Simao city, Yunnan Province

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Acta Seismologica Sinica(English Edition) 2005年第5期18卷 117-123,133页

作者：杨竹转邓志辉赵云旭朱培耀 Institute of Geology China Earthquake Administration Beijing 100029 China Earthquake Administration of Simao City Simao Yunnan Province 665000 China Earthquake Administration of Yunnan Province Kunming 650000 China

The study on coseismic step-like changes of water-level is of theoretical and practical significance to the mitigation of secondary hazards, identification of earthquake precursors, tracking of the subsequent shocks, and the research of crustal activity (Nur and Booker, 1972; WANG et al, 1988). A lot of researches have been done by previous geoscientists. Among them, ZHANG et al (1994) inverted stress variation in the aquifers through the analysis of coseismic step-like changes of well water level. LI (1995), WANG (2000), and FU et al (2002) studied the relationship between coseismic step-like changes of water level and future seismic activity. HUANG et al (2000) investigated the water-level changes in many wells after the occurrence of one great earthquake. However,the analysis of the quantitative relation between the coseismic step-like changes of water level and earthquakes in China has not been reported so far. This paper describes the coseismic step-like changes of water level in the Dazhai well, Simao city, Yunnan Province, and tries to discuss the possible mechanism of these changes.

关键词： water-level coseismic step-like change earthquake Dazhai well

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Analysis of the Frequency Domain water-level Deconvolution Method Based on Reservoir Airgun Source Data

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Earthquake Research in China 2018年第3期32卷 355-366页

作者： You Xiuzhen Li Jun Lin Binhua Huang Yandan Wu Lihua Guo Yang Fujian Earthquake Agency Fuzhou 350003China

Based on the 2016 airgun experimental data of the Fujian Nanyi reservoir,we adopted the frequency domain water-level deconvolution method and cross-correlation time delay detection technique to study the influence of level scaling factor and the background noise level of the station on deconvolution calculation results, and analyze the effect of deconvolution on eliminating the influence of the source caused by different air-gun pressures. The results show that:( 1) When the level scaling factor is smaller,the signal to noise ratio of the waveform after the deconvolution is smaller,and when the level scaling factor is over smaller,the identification error of travel time is greater.( 2) When the SNR of the station record is higher,the recognition accuracy of travel time is higher,the influence of SNR on the reference station record is far greater than the far station,when the SNR of the far station record is more than 10,the error of travel time is within6 ms,but when the SNR of the reference station record is 30,the travel time error may reach to 20 ms.( 3) When the airgun source difference is big,the frequency domain waterlevel deconvolution method has better effect on eliminating the source influence,but the method error may be introduced when the source difference is small.

关键词： Large volume airgun water-level deconvolution in frequency domain Cross-correlation time delay Green s function

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water-level Fluctuations of Urmia Lake: Relationship with the Long-Term Changes of Meteorological Variables (Solutions for water-Crisis Management in Urmia Lake Basin)

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Atmospheric and Climate Sciences 2014年第3期4卷 358-368页

作者： Mojtaba Zoljoodi Ali Didevarasl Atmospheric Sciences and Meteorological Research Center Tehran Iran Iranian National Institute for Oceanography and Atmospheric Science Tehran Iran

Urmia Lake in northwest of Iran, through the recent years has been extremely faced with the water crisis. Climate variations and anthropogenic impacts could be two main affiliated factors in this regard. We considered the long term data series of precipitation, temperature and evaporation in monthly and yearly scales in order to compare to water-level values of Urmia Lake. The statistics approaches such as: standard deviation, trend analysis, T test, Pearson and Spearman correlations, liner regression are used to analyze all variables. The results released that the water-level of Urmia Lake along with the precipitation and temperature of the lake’s basin have experienced the periodic changes through 1961 to 2010, as there are some gradual dryness trends on the study area according to precipitation and temperature variations. Urmia Lake periodic water-level fluctuations show more significant correlation to temperature than the precipitation. Whiles, the water-level’s decreasing behavior especially through 1998 to 2010 is more harsh and different than the rate that is considered for precipitation’s decrease and temperature’s increase. Thus, there could be some anthropogenic factors in the basin which produced some supplementary causes to shrink Urmia Lake. Extracting the double precipitation over the basin through introducing and categorizing of atmospheric synoptic systems in order to cloud seeding operation could be one of urgent and innovative solutions to mitigate water crisis in the basin.

关键词： Urmia Lake water-level Fluctuation Climate Variations water Crisis Anthropogenic Impacts Cloud Seeding Operation

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