Response of diatom community in Lugu Lake (Yunnan–Guizhou Plateau,China) to climate change over the past century     

Chuanhong Chen  Liangyuan Zhao  Chi Zhu  Jingzhong Wang  Jinhui Jiang  Shao Yang 《Journal of Paleolimnology》2014,51(3):357-373

A mean annual temperature increase has been recorded on the Yunnan–Guizhou Plateau of China during the last century. This temperature increase has been significantly greater since the 1950s. Thus, paleolimnological analyses may be utilized to better understand ecological responses to recent changing climate over decadal to centennial timescales, especially in regions with sparse lake monitoring data. Here, we present paleolimnological results from a ²¹⁰Pb/¹³⁷Cs-dated sediment core spanning approximately the last ~250 years from a remote, alpine, semi-closed oligotrophic lake (Lugu Lake) on the northwestern Yunnan–Guizhou Plateau. Sediment profiles of diatoms, geochemical variables (LOI₅₅₀, TOC and C/N) and median grain size were analyzed and compared with the climate data (1951 AD–2010 AD) from the Lijiang weather station. Endogenous productivity of Lugu Lake has increased gradually over the last 30 years. The majority of diatom taxa encountered in the core are typical of alkaline oligotrophic lakes. Diatom assemblages were dominated by Cyclostephanos dubius, Cyclotella taxa, and fragilarioid taxa. Diatom species composition has changed significantly with three assemblage shifts at different scales over the ~250-year period. Diatom species diversity reveals a distinct increase before ~1970 AD, followed by a decline. In addition, a decreasing trend in diatom cell-size was consistent with recent warming trends. Redundancy analysis (RDA) shows that regional air temperature trends (annual, spring, summer, and winter) have played a significant role (p < 0.05) in determining diatom compositional changes over the past six decades. Results of this study suggest that regional warming is the main driving force behind recent changes in diatom composition at Lugu Lake, while nutrients may also have impact on the diatom change in recent 10 years.  相似文献   

LiDAR及倾斜摄影技术在数字实景城市模型中的应用     

阚晓云  孙景振 《测绘信息与工程》2014,(3):43-46

倾斜摄影技术是近几年来国际测绘领域发展起来的一项新技术,相比于传统航空摄影获得的垂直拍摄影像,它可以从多个角度获得地物影像,以及常规摄影无法得到的地物立面的纹理信息和几何信息。而经过多年的发展,激光雷达技术已经非常成熟地应用于数字城市建模中。本文研究利用机载倾斜摄影数据和激光雷达数据结合的方式进行数字实景城市的建模,通过在成宁的实验与应用表明,这种方式高效、精度高,具有非常好的应用前景。  相似文献   

Regional ecosystem services relationships and their potential driving factors in the Yellow River Basin,China     

SHAO Yajing  LIU Yansui  LI Yuheng  YUAN Xuefeng 《地理学报(英文版)》2023,33(4):863-884

The Yellow River Basin(YRB) occupies an important position in China’s socioeconomic development and ecological conservation efforts. Understanding the spatiotemporal characteristics of the relationships among multiple ecosystem services(ESs) and their drivers is crucial for regional sustainable development and human-earth system coordination. This study simulated food production(FP), water yield(WY), net primary production(NPP), soil conservation(SC), and habitat quality(HQ) in the YRB from 2000...  相似文献   

Screening Indian Mustard Genotypes for Phytoremediating Arsenic‐Contaminated Soils     

Mohd Kafeel Ahmad Ansari  Shahid Umar  Altaf Ahmad  Shahid Hussain Ansari  Muhammad Iqbal  Gary Owens  Hong‐Bo Shao 《洁净——土壤、空气、水》2013,41(3):313-314

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全球及中国大陆强震时序活动特征     

邵志刚  马宗晋  蔡晋安  任金卫  陈会忠  张浪平 《中国地震研究》2013,27(3):301-315

基于强震目录,讨论了全球、中国大陆西部及周边“大三角地区”和中国大陆地区强震活动时序特征。依据8级地震分段活动特征分析认为,20世纪60年代前后全球特大地震活动状态存在显著差异;利用最优分割统计分析认为,自1800年以来“大三角地区”经历了持续时间为100余年的8级地震活动过程;进一步分析认为全球和“大三角”地区强震活动可能具有至少百年尺度的地震“周期”,而且具有一定的准同步性。中国大陆地区MS≥7.0浅源地震活动明显受控于“大三角”地区和全球更大空间尺度的地震活动,地震活动时序上表现为十几年和近百年不同时间层次上的活动特征。  相似文献   

Water quantity and quality simulation by improved SWAT in highly regulated Huai River Basin of China   总被引：1，自引：0，他引：1  

Yongyong Zhang  Jun Xia  Quanxi Shao  Xiaoyan Zhai 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(1):11-27

High regulation of dams or sluices disturbs flow regimes and pollutant transformation process significantly in most basins over the world. The water quality and quantity simulation in highly regulated river basins is always a very complicated task. The Huai River Basin is a typical area in China with the highest density of water projects and serious pollution problems simultaneously. In this paper, a procedure based on Soil and Water Assessment Tool (SWAT) was proposed to carry out the water quantity and quality simulation of Huai River Basin by incorporating the operation rules of dams or sluices into the reservoir regulation module. The water quality module in SWAT is extended to suit the actual situation of river basin in China. The results show that: for runoff simulation, 28 of all the 38 stations (73.7%) have the acceptable performance, with the average correlation coefficient and efficiency coefficient of 0.83 and 0.66, respectively in the calibration period. In the validation period, 17 of all the 34 stations (50%) have the acceptable performance, with the average correlation coefficient and efficiency coefficient of 0.77 and 0.54, respectively. The model performs the worst for reservoirs, little better for sluices and the best for unregulated stations. Comparing to the low flow and high flow simulation of original SWAT model, the low flow simulation of reservoirs and the high flow simulation of sluices are much better because of their different main purposes. For water quality simulation, the standard reaching rates of NH₃–N and COD_Mn are 55.9% (19/34) and 67.6% (23/34) respectively for all the stations, and the average relation coefficients are 0.46 and 0.48 respectively. Comparing with the results of original SWAT model, the improved model better reproduces the long-term water quantity and quality processes in the Huai River Basin of China. This study provides a new approach and reference to understand the variation of water quantity and quality in highly regulated river basin, and is expected as technical support for the environment restoration and integrated management in the basins, especially in China.  相似文献   

A micromechanical-based elasto-viscoplastic model for the Callovo-Oxfordian argillite: Algorithms,validations, and applications     

Tao Zeng  Jian-Fu Shao  Yao Yao 《国际地质力学数值与分析法杂志》2020,44(2):183-207

For a potential geological barrier of high-level radioactive waste repositories in France, the long-term mechanical behavior of the Callovo-Oxfordian (COx) argillite is the most concern for engineers. In this paper, a micromechanical-based elasto-viscoplastic model is proposed, and its numerical realization is our main object. The COx argillite is considered as a three-phase composite consists of porous clay, quartz, and calcite. By assigning appropriate constitutive laws to those constituents, the macroscopic elasto-viscoplastic behavior of the COx argillite is determined with an extended Hill's incremental approach. The numerical aspects includes (a) a new formulation is proposed for the plastic multiplier when adopting the overstress (Perzyna) model to define the viscoplastic strain. Meanwhile, a new formulation is also proposed to solve it within the framework of an implicit returning mapping scheme. (b) The corresponding consistent tangent moduli are strictly derived by extending the method proposed for solving plastic problems; (c) the efficiency of the proposed integration algorithms for the local constitutive equations and the homogenization procedure are validated, receptively, by a built-in porous plasticity model of a commercial finite element (FE) program ABAQUS and by FE computations of a two-phase unit cell; and (d) the proposed micromechanical model is finally applied to simulate experiment data in short-term triaxial compression tests and long-term triaxial creep tests. And the numerical results show that it is able to reflect the variation of the mechanical behavior with respect to the varied mineralogical compositions.  相似文献   

Mesoscale spatial variability of soil‐water content in an alpine meadow on the northern Tibetan Plateau     

Xuchao Zhu  Mingan Shao  Yin Liang  Zhiyuan Tian  Xin Wang  Lili Qu 《水文研究》2019,33(19):2523-2534

Soil water is an important limiting factor for restoring alpine meadows on the northern Tibetan Plateau. Field studies of soil‐water content (SWC), however, are rare due to the harsh environment, especially in a mesoscale alpine‐meadow ecosystem. The objective of this study was to assess the spatial variability of SWC and the temporal variation of the spatial variability in a typical alpine meadow using a geostatistical approach. SWC was measured using a neutron probe to a depth of 50 cm at 113 locations on 22 sampling occasions in a 33.5‐hm² alpine meadow during the 2015 and 2016 growing seasons. Mean SWC in the study plot for the two growing seasons was 18.7, 14.0, 13.9, 14.3, and 14.8% for depths of 10, 20, 30, 40, and 50 cm, respectively, and SWC was significantly larger at 10 cm than at other depths. SWC was negatively correlated with its spatial variability, and the spatial variability was higher when SWC was lower. Thirty‐three sampling locations in this study plot met the requirement of accuracy of the central limit theorem. A Gaussian model was the best fit for SWC semivariance at depths of 10, 20, and 30 cm, and the spatial structural ratio was between 0.997 and 1, indicating a strong spatial dependence of SWC. The sill and range fluctuated temporally, and the nugget and spatial structural ratio did not generally vary with time. The sill was significantly positively correlated with SWC and was initially stable and then tend to increase with SWC. The nugget, range, and spatial structure ratio, however, were not correlated with SWC. These results contribute to our understanding of SWC spatial distribution and variation in alpine meadows and provide basic empirical SWC data for mesoscale model simulations, optimizing sampling strategies and managing meadows on the Tibetan Plateau.  相似文献   

Bayesian model selection for sand with generalization ability evaluation     

Yin-Fu Jin  Zhen-Yu Yin  Wan-Huan Zhou  Jian-Fu Shao 《国际地质力学数值与分析法杂志》2019,43(14):2305-2327

Current studies have focused on selecting constitutive models using optimization methods or selecting simple formulas or models using Bayesian methods. In contrast, this paper deals with the challenge to propose an effective Bayesian-based selection method for advanced soil models accounting for the soil uncertainty. Four representative critical state-based advanced sand models are chosen as database of constitutive model. Triaxial tests on Hostun sand are selected as training and testing data. The Bayesian method is enhanced based on transitional Markov chain Monte Carlo method, whereby the generalization ability for each model is simultaneously evaluated, for the model selection. The most plausible/suitable model in terms of predictive ability, generalization ability, and model complexity is selected using training data. The performance of the method is then validated by testing data. Finally, a series of drained triaxial tests on Karlsruhe sand is used for further evaluating the performance.  相似文献   

Demonstration and application of NMM‐based fractured porous medium flow model     

Qi‐Hua Zhang  Shao‐Zhong Lin  Hai‐Dong Su  Gen‐Hua Shi 《国际地质力学数值与分析法杂志》2021,45(1):132-153

In natural rock masses, the shapes of three‐dimensional (3‐D) blocks cut by arbitrary fracture networks may be very complex. Owing to the geometric complexity and difficulty of mesh discretization of 3‐D blocks and fracture facets, explicit consideration of fracture networks in flow analysis of fractured porous medium (FPM) is very challenging. Using the numerical manifold method based on independent covers (NMMIC), an FPM flow model was proposed that can deal with very complex 3‐D fracture networks. In this paper, the convergence of NMMIC was first demonstrated. The theoretical basis of the arbitrary refinement of computational meshes was proven. Moreover, three peculiarities of NMMIC meshes, that is, arbitrary shape, arbitrary connection, and arbitrary refinement of independent covers, were concluded. Finally, some two‐dimensional (2‐D) tunnel flow examples were analyzed and the numerical results were compared with the analytical results. 3‐D examples with complex fracture distributions were also analyzed. In addition, the computational scale of the developed program was tested by increasing the number of computational elements. The results show that our model can accurately analyze the groundwater flow of rocks surrounding tunnels with complex fracture distributions.  相似文献