Spatiotemporal characteristics of the Huangtupo landslide in the Three Gorges region (China) constrained by radar interferometry

The Huangtupo landslide is one of the largest in the Three Gorges region, China. The county-seat town of Badong, located on the south shore between the Xiling and Wu gorges of the Yangtze River, was moved to this unstable slope prior to the construction of the Three Gorges Project, since the new Three Gorges reservoir completely submerged the location of the old city. The instability of the slope is affecting the new town by causing residential safety problems. The Huangtupo landslide provides scientists an opportunity to understand landslide response to fluctuating river water level and heavy rainfall episodes, which is essential to decide upon appropriate remediation measures. Interferometric Synthetic Aperture Radar (InSAR) techniques provide a very useful tool for the study of superficial and spatially variable displacement phenomena. In this paper, three sets of radar data have been processed to investigate the Huangtupo landslide. Results show that maximum displacements are affecting the northwest zone of the slope corresponding to Riverside slumping mass I#. The other main landslide bodies (i.e. Riverside slumping mass II#, Substation landslide and Garden Spot landslide) exhibit a stable behaviour in agreement with in situ data, although some active areas have been recognized in the foot of the Substation landslide and Garden Spot landslide. InSAR has allowed us to study the kinematic behaviour of the landslide and to identify its active boundaries. Furthermore, the analysis of the InSAR displacement time-series has helped recognize the different displacement patterns on the slope and their relationships with various triggering factors. For those persistent scatterers, which exhibit long-term displacements, they can be decomposed into a creep model (controlled by geological conditions) and a superimposed recoverable term (dependent on external factors), which appears closely correlated with reservoir water level changes close to the river's edge. These results, combined with in situ data, provide a comprehensive analysis of the Huangtupo landslide, which is essential for its management.

三峡大坝的修建对库区动物的影响

世界上最大的大坝—三峡大坝―于2003年6月正式建成并蓄水，三峡水库的水位由蓄水前的84m上升至蓄水后的139m。三峡大坝的修建与蓄水，已经显著地改变了三峡库区陆地生态系统和水域生态系统的生态环境。三峡大坝的修建将如何影响生活在这一区域（包括陆地和水域）的野生动植物资源，是个亟待解决的问题。 对于陆地生态系统，三峡大坝的修建，使三峡库区的生态环境进一步破碎化（Fragmentation）和岛屿化（Island）。为了了解三峡大坝的修建对三峡库区野生动物所产生的影响，我们选择适应性强且对环境变化敏感的啮齿动物为研究对象，在三峡库区选取两个岛屿（洛碛岛和皇华岛）及其对岸为研究点，在野外调查了啮齿动物的群落组成、种群密度与分布，并用胃容物分析和稳定性同位素分析方法研究了两个研究点优势种啮齿动物的食物来源与组成。结果表明，两个研究点间啮齿动物群落组成有很大差异，这主要是由于啮齿动物分布的地域性差异引起的。在同一个研究点，岛屿上的啮齿动物群落组成与对岸的没有差异，但在岛屿上的啮齿动物种群密度却明显高于其对岸的，这说明随着库区水位的大幅度提升，岛屿的面积急剧减小，使原本栖息在水边的啮齿动物不得不向岛屿的中上部迁移，致使岛屿上的啮齿动物的种群密度迅速增加。啮齿动物的食物来源有四种：C3非豆科植物，C3豆科植物，C4植物及水生生物。不同种啮齿动物的食物种类组成也不同，四川短尾鼩（Anourosorex squamipes）的食物中有水生生物的组成成分，但其它啮齿动物食物中不含水生生物。不同食物来源在啮齿动物的整体食物中所占比例也不同，并呈明显的季节性变化，这种变化与田间的农作物种类密切相关。动物组织的稳定性同位素组成不仅可以示踪动物的食物来源，也反映了动物的生存状况。我们的结果显示：对岸啮齿动物的稳定性同位素组成相对集中，并且不同种啮齿动物间没有重叠。这一方面说明对岸啮齿动物的食物来源相对丰富，啮齿动物可以选择各自喜食食物，在此环境下的啮齿动物种间竞争相对较弱，至少是种间食物竞争较弱。岛屿上啮齿动物的稳定性同位素值分布范围远大于在对岸的，并且种间稳定性同位素组成有明显的重叠部分。稳定性同位素组成的重叠意味着有相似的食物来源，也即栖息生境相似。这说明岛上的啮齿动物种间存在较剧烈的食物竞争关系。在资源限制情况下，多种啮齿动物不得不利用共同的食物来源。换句话说，岛屿化过程将加剧岛屿上啮齿动物的种间竞争。 洛碛岛上的四川短尾鼩因为可以利用水生食物来源，这使得它在岛屿化过程中处于有利地位。随着岛屿化进程的加剧，四川短尾鼩在岛屿上的优势将更加明显。而皇华岛屿上的褐家鼠的食物来源单一，会因岛屿面积的进一步减小，食物来源更加缺乏，它们将不得不改其食物组成或面临消失。而白腹巨鼠的栖息环境靠近江边，将因水位的上升进一步上移，它们的栖息环境与普通田鼠的发生重叠，使得白腹巨鼠与普通田鼠发生栖息地的竞争与食物竞争，并面临更多的人为因素干扰。 对于水域生态系统，长江是我国最大的河流，也是我国淡水鱼类最丰富的区域。三峡大坝的修建已经显著改变了三峡库区的水文特征。为了了解三峡大坝的修建是否会改变三峡库区的有机物组成，并进而影响到三峡库区水生生物的食物来源和组成，我们选择了三个水文特征不同的研究点（洛碛江段、皇华城江段和茅坪江段）调查了三峡库区的常见鱼种类组成，并用稳定性同位素方法研究了三峡库区洪水前后的有机物组成变化与鱼类的食物网模型，用稳定性同位素划分了鱼类食物网结构及鱼类体长与其肌肉δ15N值间的关系。结果表明，三峡大坝的修建，已经显著改变了皇华城和茅坪江段的水文特征，同时也“干扰”了生活在这一区域的鱼类。适应于流水环境的鱼类在库区回水处和大坝附近几乎消失，而喜欢静态环境的其它鱼类却得到极大的发展，例如鲢鱼（H. molitrix）和草鱼（ C. idellus）。 洪水前后，三峡库区的有机物组成成分有明显改变。洪水前，水中有机物主要以河流自身生产力产生的有机物为主（浮游植物、藻类等）;洪水后，水中有机物主要以外来有机物为主（陆地植物、土壤有机物和从上游带来的有机物）。对于三个食物网模型：河流连续体模型（RCC）、脉冲模型（FPC）和河流生产力模型（RPM），河流生产力模型能更好的解释三峡库区的水生生物的食物来源，即三峡库区的水生生物的食物主要来源于河流自身生产力产生的有机物。但外来有机物作为水生生物的一种辅助食物来源，在洪水期间起到不可忽视的作用。 在本研究中，鱼类体长与其δ15N值间的关系与选取鱼的种类有关，比如南方大口鲇（Silurus asotus）的体长与其肌肉的δ15N值呈明显负相关关系（R2≈0.5），而鱖鱼（Siniperca）、铜鱼（Coreius guichenoti）和草鱼（Ctenopharyngodon idellus）的体长与其肌肉的δ15N值却呈正相关关系。 三峡库区常见鱼类主要以杂食性和广普性鱼类为主，食物网结构十分复杂。通过胃容物分析和稳定性同位素分析，三峡库区水生生物营养级间的判别值约为3.1‰。依据鱼类肌肉的δ15N值，三峡库区的常见鱼类可以划分为四个营养级：草食性鱼类（herbivorous fish）、初级杂食性鱼类（1ºomnivorous fish）、次级杂食性鱼类（2ºomnivorous fish）和食鱼性鱼类（piscivorous fish）。营养级间没有明确的分界限，鱼类的营养级从2到4.8，是连续分布的营养级结构，从而更真实的反映了自然界中动物的捕食关系和在食物网中的位置。 自然丰度变化的稳定性同位素(Stable isotope)作为一种天然的示踪物，在动物生态学上已经得到广泛应用。动物的稳定性同位素可以清楚的示踪动物的食物来源、食物组成、栖息地情况和生存状况等多种信息，结合传统的胃容物分析，或其它的粪便分析、储藏物分析等，稳定性同位素技术在动物生态学研究方面必将得到更广泛的应用。

Mitochondrial DNA variation, effective female population size and population history of the endangered Chinese sturgeon, Acipenser sinensis

The anadromous Chinese sturgeon (Acipenser sinensis), mainly endemic to the Yangtze River in China, is an endangered fish species. The natural population has declined since the Gezhouba Dam blocked its migratory route to the spawning grounds in 1981. In the near future, the completion of the Three Gorges Dam, the world's largest hydroelectric project, may further impact this species by altering the water flow of the Yangtze River. Little is currently known about the population genetic structure of the Chinese sturgeon. In this study, DNA sequence data were determined from the control region (D-loop) of the mitochondrial genome of adult sturgeons (n = 106) that were collected between 1995-2000. The molecular data were used to investigate genetic variation, effective female population size and population history of the Chinese sturgeon in the Yangtze River. Our results indicate that the reduction in abundance did not change genetic variation of the Chinese sturgeon, and that the population underwent an expansion in the past. AMOVA analysis indicated that 98.7% of the genetic variability occurred within each year's spawning populations, the year of collection had little influence on the diversity of annual temporary samples. The relative large effective female population size (N-ef) indicates that good potential exists for the recovery of this species in the future. Strikingly, the ratio of N-ef to the census female population size (N-f) is unusually high (0.77-0.93). This may be the result of a current bottleneck in the population of the Chinese sturgeon that is likely caused by human intervention.

Effects of damming on population sustainability of Chinese sturgeon, Acipenser sinensis: evaluation of optimal conservation measures

The numbers of spawning sites for Chinese sturgeon have been drastically reduced since the construction of the Gezhouba Dam across the Yangtze River. This dam has blocked migration of Chinese sturgeon to their historic spawning ground causing a significant decline of the Chinese sturgeon population. We conducted a VORTEX population viability analysis to estimate the sustainability of the population and to quantify the efficiency of current and alternative conservation procedures. The model predicted the observed decline of Chinese sturgeon, resulting from the effect of the Gezhouba Dam. These simulations demonstrated the potential interest of two conservation measures: increasing spawning area and reducing predation on sturgeon eggs. The simulations also demonstrated that the actual restocking program is not sufficient to sustain sturgeon population as the artificial reproduction program induce the loss of more wild mature adults that the recruitment expected by the artificial reproduction.

Using drift nets to capture early life stages and monitor spawning of the Yangtze River Chinese sturgeon (Acipenser sinensis)

P>A sampling system for capturing sturgeon eggs using a D-shaped bottom anchored drift net was used to capture early life stages (ELS) of Chinese sturgeon, Acipenser sinensis, and monitor annual spawning success at Yichang on the Yangtze River, 1996-2004, before and just after the Three Gorges Dam began operation. Captured were 96 875 ELS (early life stages: eggs, yolk-sac larvae = eleuthero embryos, and larvae); most were eggs and only 2477 were yolk-sac larvae. Most ELS were captured in the main river channel and inside the bend at the Yichang spawning reach. Yolk-sac larvae were captured for a maximum of 3 days after hatching began, indicating quick dispersal downstream. The back-calculated day of egg fertilization over the eight years indicated a maximum spawning window of 23 days (20 October-10 November). Spawning in all years was restricted temporally, occurred mostly at night and during one or two spawning periods, each lasting several days. The brief temporal spawning window may reduce egg predation by opportunistic predators by flooding the river bottom with millions of eggs. During 1996-2002, the percentage of fertilized eggs in an annual 20-egg sample was between 63.5 to 94.1%; however, in 2003 the percentage fertilized was only 23.8%. This sudden decline may be related to the altered environmental conditions at Yichang caused by operation of the Three Gorges Dam. Further studies are needed to monitor spawning and changes in egg fertilization in this threatened population.

Polymorphic microsatellites in largemouth bronze gudgeon (Coreius guichenoti) developed from repeat-enriched libraries and cross-species amplifications

Largemouth bronze gudgeon (Coreius guichenoti) is a medium-sized fish endemic from the upper Yangtze River of China and its survival is threatened by the construction of the Three Gorges Dam. This study reports 20 new polymorphic microsatellites from a repeat-enriched genomic library with a mean number allele of 5.2, and observed and expected heterozygosities ranging from 0.035 to 1, and from 0.13 to 0.917, respectively. In a cross-species amplification test, nine of the 37 tested loci were found to be also polymorphic in a congeneric species, brass gudgeon (C. heterodon). In addition, other four loci from common carp (Cyprinus carpio) were also polymorphic in C. guichenoti. Out of these 24 polymorphic microsatellites, only three loci significantly deviated from Hardy-Weinberg equilibrium in the sampled population (P < 0.0025), and all pairwise tests for linkage disequilibrium among loci were nonsignificant after applying sequential Bonferroni correction (P > 0.0026). These novel microsatellites provide sufficient levels of polymorphism for studies on population genetics and conservation in C. guichenoti and its related species.

Population genetic structure of an endemic cyprinid fish, Ancherythroculter nigrocauda, in the upper reaches of the Yangtze River and its implication for conservation

Ancherythroculter nigrocauda is a cyprinid fish endemic to the upper reaches of the Yangtze River, which has been reported to have 2 or 3 chambers to its air bladder. Morphological studies showed no differences between individuals with different types of air bladder, but did demonstrate geographical differences from different sources. After the completion of the Three Gorges Dam, it was expected that the population of this species would decrease, but artificial breeding and stocking is under consideration to protect this species from extinction. In the present study, mtDNA cytochrome b gene sequences were determined and analyzed for A. nigrocauda samples of different morphotypes and sources to identify their genetic differentiations, and thereby guide plans for the artificial propagation and conservation of this species. Haplotype diversity index values (h) and nucleotide diversity values (pi) for all the populations were found to be high indicating their high level genetic diversity. An analysis of molecular variance identified no differentiation among the studied populations. Therefore, we suggested that the individuals of different morphological types and geographical sources belong to the same species. To maintain its high level genetic diversity, it mill he necessary to use large and diverse sources of parental fish for artificial reproduction.

Nutrients in the Changjiang River

N, P and SiO3-Si in the Changjiang mainstream and its major tributaries and lakes were investigated in the dry season from November to December, 1997, and in the flood season in August and October, 1998. An even distribution of SiO3-Si was found along the Changjiang River. However, the concentrations of total nitrogen, total dissolved nitrogen, dissolved inorganic nitrogen, nitrate and total phosphorus, total particulate phosphorus increased notably in the upper reaches, which reflected an increasing impact from human activities. Those concentrations in the middle and lower reaches of the Changjiang River were relatively constant. Dissolved N was the major form of N and the particulate P was the major form of P in the Changjiang River. The molar ratio of dissolved N to dissolved P was extremely high (192.5-317.5), while that of the particulate form was low (5.6-37.7). High N/P ratio reflected a significant input of anthropogenic N such as N from precipitation and N lost from water and soil etc. Dissolved N and P was in a quasi-equilibrium state in the process from precipitate to the river. In the turbid river water, light limitation, rather than P limitation, seemed more likely to be a controlling factor for the growth of phytoplankton. A positive linear correlationship between the concentration of dissolved N and the river's runoff was found, mainly in the upper reaches, which was related to the non-point sources of N. Over the past decades, N concentration has greatly increased, but the change of P concentration was not as significant as N. The nutrient fluxes of the Changjiang mainstream and tributaries were estimated, and the result showed that the nutrient fluxes were mainly controlled by the runoff, of which more than a half came from the tributaries. These investigations carried out before water storage of the Three Gorges Dam will supply a scientific base for studying the influences of the Three Gorges Dam on the ecology and environment of the Changjiang River and its estuary.

The environment effect on fish assemblage structure in waters adjacent to the Changjiang (Yangtze) River estuary (1998-2001)

We collected fish abundance data in the Changjiang (Yangtze River) estuary and adjacent waters in November 1998, May 1999, November 2000, and May 2001. Using the data, we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors. We used a multivariate analysis, including community ordination methods such as detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA), and two-way indicator species analysis (TWINSPAN). We analyzed the biological community structure and environmental factors to determine their spatial distributions, temporal dynamics, and seasonal variations. Among the fish species, five exceeded 5% of the total abundance: Harpodon nehereus (42.82%), Benthosema pterotum (13.85%), Setipinna taty (11.64%), Thryssa kammalensis (9.17%) and Apogonichthys lineatus (6.49%). These were separated into four ecological assemblages: hypsithermal-saline, hypsithermal-brackish, hypothermal-brackish, and hypothermal-saline. We evaluated the degree of influence of environmental factors on the fish community. Our analyses suggested that environmental factors including water depth, salinity, turbidity, transparency, nutrient, and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas. Ecological and environmental factors changed temporally from 1998 to 2001, and drove the fish community succession. The environmental factors driving the fish community structure included bottom temperature, water depth, bottom and surface pH, surface total phosphorous, and bottom dissolved oxygen. This investigation was completed before completion of the Three Gorges Dam; therefore the results of this study provide an important foundation for evaluating the influence of the human activities.

Dissolved oxygen and O-2 flux across the water-air interface of the Changjiang Estuary in May 2003

The field observation of this study was carried out in the Changjiang Estuary from May 19 to 26,2003, just a few days before the Three Gorges Dam began to store water. A total of 29 stations, including 2 anchor stations, were distributed through almost the whole salinity gradient Based on the data gained from these stations, the biogeochemical characteristics of dissolved oxygen (DO) were examined. Spatial distribution of DO concentrations showed the pattern that it increased in a downriver direction. DO concentration generally varied within a narrow range of 733-8.10 mg l(-1) in the freshwater region and the west part of the mixed water region, and after that it increased rapidly. In vertical direction, the differences in DO concentrations between surface and 2 m above the bottom were big at the stations with water depths exceeding 20 m; DO concentration up to 14.88 mg l(-1) was recorded at the sea surface, while at 2 m above the bottom its concentration was only about 4 mg l(-1). The fluctuation in DO concentrations was small during a period of 48 h in the mixed water region and 2 m above the bottom of the seawater region; while it was large during the same period in the seawater region for surface and 5 m below the surface layer, and a maximum variation from 8.77 to 12.66 mg l(-1) in 4 h was recorded. Oxygen fluxes also showed a marked spatio-temporal variation. As a whole, the freshwater region and mixed water region were an oxygen sink while the seawater region was a source. Relationships between dissolved oxygen and some biogeochemical parameters which could markedly influence its spatio-temporal distribution were discussed in this paper. (C) 2008 Elsevier B.V. All rights reserved.

龙滩水电站左岸边坡监测信息系统研制及其监测资料分析

Guangxi Longtan Hydropower Station is not only a representative project of West Developing and Power Transmission from West to East in China, but also the second Hydropower Station to Three Gorges Project which is under construction in China. There are 770 X 104m3 creeping rock mass on the left bank slope in upper reaches, in which laid 9 water inlet tunnels and some underground plant buildings. Since the 435m high excavated slope threatens the security of the Dam, its deformation and stability is of great importance to the power station.Based on the Autodesk Map2004, Longtan Hydropower Station Monitoring Information System on Left Bank has been basically finished on the whole. Integrating the hydropower station monitoring information into Geographic Information System(GIS) environment, managers and engineers can dynamically gain the deformation information of the slop by query the symbols. By this means, designers can improve the correctness of analysis, and make a strategic and proper decision. Since the system is beneficial to effectively manage the monitoring-data, equitably save the cost of design and safe construction, and decrease the workload of the engineers, it is a successful application to the combination of hydropower station monitoring information management and computer information system technology.At the same time, on the basis of the geological analysis and rock mass toppling deformation and failure mechanism analysis of Longtan engineering left bank slope, the synthetic space-time analysis and influence factors analysis on the surface monitoring data and deep rock mass monitoring data of A-zone on left bank slope are carried on. It shows that the main intrinsic factor that effects the deformation of Zone A is the argillite limestone interbedding toppling structure, and its main external factors are rain and slope excavation. What's more, Degree of Reinforcement Demand(DRD) has been used to evaluate the slop reinforce effect of Zone A on left bank according to the Engineering Geomechanics-mate-Synthetics(EGMS). The result shows that the slop has been effective reinforced, and it is more stable after reinforce.At last, on the basis of contrasting with several forecast models, a synthetic forecast GRAV model has been presented and used to forecast the deformation of zone A on left bank in generating electricity period. The result indicates that GRAV model has good forecast precision, strong stability, and practical valuable reliability.