Long-term monitoring revealed fish assemblage zonation in the Three Gorges Reservoir

Reservoirs are important artificial ecosystems that modify the hydrological and ecological characteristics of a river. Knowledge of the basic characteristics of fish assemblages in reservoirs is a first step toward the development of effective conservation policies. We used the information collected over a 10-year period (2006-2015) to assess the structure of the fish assemblages in the Three Gorge Reservoir (TGR) in a river-dam gradient. Three fish zones were detected in TGR. Species richness was the highest in the upper zone and lowest in the lower zone. The riverine zones were dominated by rheophilic species Coreius guichenoti and Pelteobagrus vachelli. The transitional zones were dominated by Coreius heterodon and Rhinogobio cylindricus. The lacustrine zones were dominated by eurytopic species Hypophthalmichthys molitrix, Aristichthys nobilis, Hemiculter bleekeri and Cyprinus carpio. For the functional characteristics, fish assemblages in riverine and transitional zones were dominated by insectivorous species, equilibrium strategists and rheophilic species (e.g., Coreius heterodon and Coreius guichenoti). In lacustrine zones, the fish assemblage was dominated by habitat generalists common to lakes and reservoirs (e.g., Hemiculter bleekeri, Hypophthalmichthys molitrix, Aristichthys nobilis). Moreover, 18 exotic species (e.g., Protosalanx hyalocranius, Ictalurus punctatus, Megalobrama amblycephala, Tilapia) were collected in TGR, most of which only existed in the lacustrine zone. The results highlight the importance of freely flowing riverine reaches for conserving native fish in the upper Changjiang River and adaptive management strategies for fisheries in TGR.     

基于核密度分析的无障碍设施分析

为提升首都城市的基础设施环境质量,本文基于核心区无障碍设施数据成果,应用核密度分析方法,开展对首都功能核心区的盲道、出入口、地铁电梯、公共厕所、停车场、坡道进行现状分析,并对其无障碍设施普及程度展开研究。通过核密度分析,盲道呈现“三心汇聚、离心递减”的特征,出入口呈现“两翼齐飞”的特征。通过现状研究,无障碍设施存在的问题总体上表现为设施数量不足,质量不高,分布不均衡等特点,为政府和规划管理部门提供相应的决策依据。     

河南关山地质公园古崩塌地貌旅游资源开发

南太行是我国重要的旅游风景线,河南关山的古崩塌地貌是迄今为止南太行地区发现的规模最大、景观最全的古崩塌遗迹。这种崩塌现象与岩性、地层、产状、结构构造、节理裂隙、新构造运动以及地形地貌条件等关系密切。紫红色石英砂岩和碳酸盐岩构成的山体因崩塌作用而形成了造型奇特的山峰、石柱、崖壁、岩洞、峡谷、一线天等异彩纷呈的崩塌地貌景观。这些在特定背景下形成的独特地貌景观是十分典型的灾害地质遗迹和极为重要的旅游地质资源,具有特殊的地球科学意义、环境保护意义和旅游观赏价值,通过深入研究和科学规划,把关山地质公园建设成地学研究基地、教学实习基地和青少年科普教育基地,同时结合当地优美的生态环境和引人入胜的各种自然景观,开发建设成休闲度假的场所和健身娱乐的区域。     

Density functional study of AunCu (n=1-7) clusters

The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copper-doped gold clusters, Au_nCu (n=1-7), are investigated using the density functional theory. Several low-lying isomers are determined. The results indicate that the ground-state Au_nCu clusters have planar structures for n = 1-7. The stability trend of the Au_nCu clusters (n=1-7), shows that odd-numbered Au_nCu clusters are more stable than the neighbouring even-numbered ones, thereby indicating the Au₅Cu clusters are magic cluster with high chemical stability.     

Contribution of different functional groups to the diet of major predatory fishes at a seagrass meadow in northeastern Japan

We examined the variation in habitat use and diet of three dominant fish species (Myoxocephalus brandti, Pholidapus dybowskii, and Pholis crassispina) in a seagrass meadow in the Akkeshi-ko estuary in northeastern Japan, where broad and dense Zostera marina beds exist, using a semi-quantitative census of the fishes and analyses of their stomach contents. Differences among the three fish species in the temporal variation in abundance of each age class (mainly 1- and 2-year age classes) indicated that the temporal pattern of utilization of the seagrass meadow were different among them. In the semi-quantitative dietary analysis, two prey categories, i.e., taxonomic group (order and suborder) and functional group, were used to explain the variation in prey composition with size-dependent changes. The six prey functional groups were classified based on the ecological traits of the prey, i.e., trophic level, size, and life type (habitat and behavior). Ontogenetic shifts in prey of the three fish species could be fully explained by a combination of the two prey categories, and not by the use of only one category (taxonomic or functional group). The pattern of ontogenetic shifts in prey differed among the fish species and size (age) classes. These results indicate that segregation of habitat (seagrass meadow) and prey group (taxonomic and functional group) is performed among the three species, which may contribute to their coexistence in this estuary.     

On predicting boat drift for search and rescue

A theoretical model for predicting boat drift for search and rescue missions is presented in this work. The drift model is based on the law of physics which govern the motion of a floating body in a given wind and surface current field. In terms of the empirical aerodynamics force coefficients of the boat or any other drifting object, external wind field, and current field, the drift velocity of the boat being searched for can be obtained. The uncertainty of the characteristics of the boat’s drift is evaluated by interval analysis of the uncertainties of the characteristics of the drifting boat and external forcing fields. The search area expansion and the source of uncertainty are systematically evaluated. The current statistical model-based operational definitions of leeway drift, leeway rate, leeway angle, divergence angle, leeway divergence, downwind component of leeway, and crosswind component of leeway are clarified in light of the presented theoretical model. The divergence angle and leeway divergence are evaluated through the interval analysis of the uncertainty of the parameters involved.     

The role of biocrusts in nitrogen cycling on the tropical reef islands,South China Sea

Harboring polyextremotolerant microbial topsoil communities, biological soil crusts(biocrusts) occur across various climatic zones, and have been well studied in the terrestrial drylands. However, little is known about the functional metabolic potential of microbial communities involved in the biogeochemical processes during the early succession of biocrusts on the tropical reef islands. We collected 26 biocrusts and bare soil samples from the Xisha Islands and Nansha Islands, and applied a functional gene array(GeoChip 5.0) to reveal nitrogen(N)cycling processes involved in these samples. Both physicochemical measurement and enzyme activity assay were utilized to characterize the soil properties. Results revealed the composition of N-cycling functional genes in biocrusts was distinct from that in bare soil. Additionally, microorganisms in biocrusts showed lower functional potential related to ammonification, denitrification, N assimilation, nitrification, N fixation, and dissimilatory nitrate reduction to ammonium compared to bare soils. Although the abundance of nifH gene was lower in biocrusts, nitrogenase activity was significantly higher compared to that in bare soils. Precipitation, soil physicochemical properties(i.e., soil available copper, soil ammonia N and pH) and soil biological properties(i.e., β-glucosidase, fluorescein diacetate hydrolase, alkaline protease, urease, alkaline phosphatase, catalase and chlorophyll a) correlated to the N-cycling functional genes structure. Nitrate N and ammonia N were more abundant in biocrusts than bare soil, while pH value was higher in bare soil. Our results suggested biocrusts play an important role in N-cycling in coral sand soil, and will be helpful in understanding the development and ecological functions of biocrusts on tropical reef islands.     

基于面向对象和MapX技术开发测深数据管理软件

为了实现测深数据的数据库管理模式,采用面向对象和GIS技术来开发测深数据管理软件,测深项目的所有数据如测线、水深点、潮位、声速剖面以及相关的图片和文档均保存到单一的Access数据库中,数据处理和数据管理工具通过可视化的组件或者以类的方法来提供。软件以MapX和C Builder进行开发,并在实际的测深项目中得到应用。     

象山港游泳动物群落功能群组成与功能群多样性

依据2011年4月、7月和11月象山港水域桁杆拖网和单拖网渔业资源定点调查资料,对象山港水域游泳动物群落的功能群组成及功能群多样性特征进行了系统研究。依据摄食习性,本文将调查海域出现的96种游泳动物划分为7个功能群,其中底栖动物/游泳动物食性、游泳动物食性、底栖动物食性和腐屑食性功能群是该水域的优势功能群。相似性分析检验结果显示:不同季节象山港游泳动物群落的功能群结构保持相对稳定,不存在显著性季节差异。4月、7月和11月该水域游泳动物群落的功能群多样性均值分别为1.303、1.261和1.185,亦未呈现显著性季节差异。功能群多样性指数与大个体生物(体重大于50g)的总重量资源密度显著正相关;功能群多样性与物种多样性的关系可用斜率为0.463、截距为0.266的线性方程进行描述,这表明该水域物种多样性的大量丧失可能引起功能群多样性的降低。象山港水域部分功能群所含物种数明显偏少,冗余度较低,在强大的外界干扰下,某些重要物种的衰退可能将使该水域功能群多样性显著降低。     

一阶非线性泛函方程解的振动性(英文)

考虑两类带有分布型超前或滞后量的方程 (Ⅰ)x'(t)=a(t)x(t)+φ, (Ⅱ)x'(t)=a(t)x(t)-φ.其中β(t)>a(t),t+a(t)→∞(t→∞),f(x)和φ(u)是满足某些条件的非线性函数。 本文给出了方程(Ⅰ)和(Ⅱ)的所有解振动的若干充分性判定定理。作为应用,我们又讨论了如下方程的振动性,并给出了相应的判定准则。 (Ⅲ)x'(t)=a(t)x(t)+φ[sum from i=1 to n a_i(t)f(x(t+τ_i(t)))], (Ⅳ)x'(t)=a(t)x(t)-φ[sum from i=1 to n a_i(t)f(x(t+τ_i(t)))] 本文的结果是张炳根的若干结果的推广。