A biodiversity evaluation framework for restoration of aquatic macrophyte communities in shallow lakes driven by hydrological process management     

Shuhan Li  Tao Sun  Wei Yang  Baoshan Cui  Xinan Yin 《水文研究》2021,35(1):e13983

Macrophyte community diversity and composition respond to ecosystem conservation and local environmental factors. In this study, we developed a multidimensional diversity framework for macrophyte communities, including the taxonomic and functional alpha and beta diversity. We used the framework to explore the relationships among water level regimes and these diversity parameters in a case study of China's Baiyangdian Lake. Analysis of indicators of hydrologic alteration divided the water level from 1959 to 2019 into four regimes (dry, <6.42 m; low, 6.42–7.23 m; medium, 7.23–8.19 m; high, >8.19 m). Alpha and beta diversity were significantly higher in the medium regime than in the low and high regimes. Redundancy analysis indicated that the maximum water depth significantly affected taxonomic alpha diversity, and total nitrogen (TN) and chemical oxygen demand (COD) concentration significantly affected functional alpha diversity, respectively. Mantel tests showed that TN, Secchi depth (SD), and water depth in the high water level regime significantly increased the total beta diversity and turnover components. TN was the main factor that increased total taxonomic beta diversity. Water level regime mainly influenced interspecific relationships by changing the TN and COD concentration. The water level should be maintained between the medium and high water level regimes to promote restoration of the macrophyte community and improve ecosystem stability. The biodiversity evaluation framework would provide a deeper insight into the hydrological process management for restoration of aquatic macrophyte communities in shallow lakes.  相似文献   

Rainfall intensity affects runoff responses in a semi-arid catchment     

Ze Tao  Min Li  Bingcheng Si  Dyan Pratt 《水文研究》2021,35(4):e14100

The source and hydrochemical makeup of a stream reflects the connectivity between rainfall, groundwater, the stream, and is reflected to water quantity and quality of the catchment. However, in a semi-arid, thick, loess covered catchment, temporal variation of stream source and event associated behaviours are lesser known. Thus, the isotopic and chemical hydrographs in a widely distributed, deep loess, semi-arid catchment of the northern Chinese Loess Plateau were characterized to determine the source and hydrochemical behaviours of the stream during intra-rainfall events. Rainfall and streamflow were sampled during six hydrologic events coupled with measurements of stream baseflow and groundwater. The deuterium isotope (²H), major ions (Cl⁻, SO₄²⁻, NO₃⁻, Ca²⁺, K⁺, Mg²⁺, and Na⁺) were evaluated in water samples obtained during rainfall events. Temporal variation of ²H and Cl⁻ measured in the groundwater and stream baseflow prior to rainfall was similar; however, the isotope compositions of the streamflow fluctuated significantly and responded quickly to rainfall events, likely due to an infiltration excess, overland dominated surface runoff during torrential rainfall events. Time source separation using ²H demonstrated greater than 72% on average, the stream composition was event water during torrential rainfall events, with the proportion increasing with rainfall intensity. Solutes concentrations in the stream had loglinear relationships with stream discharge, with an outling anomaly with an example of an intra-rainfall event on Oct. 24, 2015. Stream Cl⁻ behaved nonconservative during rainfall events, temporal variation of Cl⁻ indicated a flush and washout at the onset of small rainfall events, a dilution but still high concentration pattern in high discharge and old water dominated in regression flow period. This study indicates rainfall intensity affects runoff responses in a semi-arid catchment, and the stored water in the thick, loess covered areas was less connected with stream runoff. Solute transport may threaten water quality in the area, requiring further analysis of the performance of the eco-restoration project.  相似文献   

流星暴的航天定义     

马月华  徐品新  李广宇  包纲 《天文学报》2005,46(2):158-164

定义ZHR^*以每小时穿过1000平方公里天顶截面的，能在铝质表面打出直径不小于1厘米的弹坑的流星体数，作为流星群对航天安全威胁强度的定量标志，给出了从ZHR到ZHR^*的换算公式．用ZHR^*取代ZHR来评价20世纪90年代以来的一些强流星雨，发现1998年的贾可比尼(天龙座)流星雨对航天安全来说，是比公认的1999、2001、2002年3次狮子座流星暴强数倍的更强流星暴．  相似文献   

平凉隐伏岩溶水环境同位素研究     

马致远  马蒂尔·亨德尔 《地球科学与环境学报》2003,25(4):60-66

地下水资源可持续利用的一个急待解决的重要问题,是对地下水补给和更新能力的评价.利用环境同位素技术研究地下水的补给和可更新性是当前较为新颖的方法之一.在西北干旱、半干旱的隐伏岩溶地区,地下水埋藏条件复杂,常规的地质勘探方法所能提供的水文地质信息有限,环境同位素方法在研究地下水的补给及可更新能力方面发挥了优势,可对传统方法进行补充和验证.其结果表明,研究区隐伏岩溶水形成较早,且有大量现代水的混入,平均混入量为54%.说明区内隐伏岩溶水的补给和更新能力较好.环境同位素分析结果还显示,大岔河隐伏岩溶水为一相对独立、半开放的水文地质单元,其补给来源部分为流域内大气降水、地表水的补给,部分为东南部三道沟岩溶地下水的补给;根据环境同位素EPM模型计算,地下水的滞留时间为36 a.地下水储存量为1.314×108 m3; 储水系数为7.29×10-3.这一结果与传统勘探方法的计算结果基本吻合,说明环境同位素方法的实用性.  相似文献   

Approach to Mountain Hazards in Tibet, China   总被引：1，自引：1，他引：0  

MADongtao TUJianjun CUIPeng LURuren 《山地科学学报》2004,1(2):143-154

Tibet is located at the southwest boundary of China. It is the main body of the Qinghai-Tibet Plateau, the highest and the youngest plateau in the world. Owing to complicated geology, Neo-tectonic movements, geomorphology, climate and plateau environment, various mountain hazards, such as debris flow, flash flood, landslide, collapse, snow avalanche and snow drifts, are widely distributed along the Jinsha River (the upper reaches of the Yangtze River), the Nu River and the Lancang River in the east, and the Yarlungzangbo River, the Pumqu River and the Poiqu River in the south and southeast of Tibet. The distribution area of mountain hazards in Tibet is about 589,000 km^2, 49.3% of its total territory. In comparison to other mountain regions in China, mountain hazards in Tibet break out unexpectedly with tremendously large scale and endanger the traffic lines, cities and towns, farmland, grassland, mountain environment, and make more dangers to the neighboring countries, such as Nepal, India, Myanmar and Bhutan. To mitigate mountain hazards, some suggestions are proposed in this paper, such as strengthening scientific research, enhancing joint studies, hazards mitigation planning, hazards warning and forecasting, controlling the most disastrous hazards and forbidding unreasonable human exploring activities in mountain areas.  相似文献   

有限元法与伪谱法混合求解弹性波动方程   总被引：6，自引：0，他引：6  

马德堂  朱光明 《地球科学与环境学报》2004,26(1):61-64

在地震波场数值模拟中,有限差分法、有限元法和伪谱法都是常用的基本方法,但它们各有不同的适应性和优缺点,如有限差分法、有限元法都存在减弱网格频散和提高计算效率的矛盾,而伪谱法的网格频散小且计算效率高.有限差分法和伪谱法在处理地表结构复杂或地表剧烈起伏以及地下结构复杂的情况时存在较大的难度,而有限元法可较为理想地拟合起伏地表和任意弯曲界面,且可方便地处理自由边界条件和界面边界条件.尝试将有限元法和伪谱法相结合,形成地震波场数值模拟的一种混合方法,利用二者的优点,克服二者的缺点,达到既减弱网格频散又提高计算精度和效率的目的.并采用所谓的‘过度区域‘技术解决两种不同算法的衔接问题.模拟实例表明,给出的混合模拟方法不失为弹性波场数值模拟的一种有效方法.  相似文献   

在BPL信道上增加数据广播内容的探讨   总被引：1，自引：1，他引：0  

吴海涛  边玉敬 《时间频率学报》2001,24(1):38-44

分析了现有罗兰C（包括BPL）在授时方面存在的不足，提出了在BPL信道上实现数据广播的主要目的。详细讨论了各种可能的数据信息的结构，并给出了有关参数和数据的计算方式和公式。认为发播内容的选择是由期望的系统功能决定的，广播内容的编排则与具体实现技术相关。最后给出了在不同调制方法下的传输速率，这是合理编排广播内容的基础。  相似文献   

毫秒级快速尖峰辐射事件的时间和频率特性     

马媛  谢瑞祥 《天文研究与技术》2001,(1):26-31

介绍了太阳22周峰年期间云南天文台米波射电频谱仪的观测结果。主要对1557个单个Spike的时间和频率分布作了统计分析，着重指出太阳快速精细结构的观测特征并定性地指出其产生机制。  相似文献   

First Post-Newtonian Angular Momentum In Relativistic Celestial Mechanics     

Jin-He Tao  Tian-Yi Huang  Zhao-Hua Yi 《Astrophysics and Space Science》1997,254(2):173-186

With a new theory on the 1PN celestial mechanics recently developed by Damour, Soffel and Xu (1991,1992,1993,1994), definitions and expressions of the 1PN spin angular momentum are investigated and analysed. The total spin angular momentum of a system of extended bodies such as the solar system is calculated and expressed as the function of local parameters and observables under reasonable assumptions, which would find its application in the evolution and dynamics of systems of celestial bodies. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Urban tourism research methodology     

Tao Wei  Zhong Wen-hui  Hong Yan 《中国地理科学(英文版)》2005,15(2):173-178

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