Molecular phylogeny of the genus Clibanarius(Decapoda: Anomura: Diogenidae) based on mitochondrial and nuclear DNA sequences

Clibanarius , a genus of hermit crabs, is one of the most diverse genera within Diogenidae. However, studies on the phylogeny within Clibanarius is very limited. We reconstruct the molecular phylogeny of the genus Clibanarius based on two mitochondrial (16S rRNA and COI) and two nuclear protein-coding (NaK and PEPCK) genes using a multigene phylogenetic approach. Eleven selected Clibanarius species from the Indo-West Pacifi c are analyzed and the Bayesian and maximum likelihood analyses produced identical results in topology. Results suggest that C . rutilus and C . infraspinatus are more closely related to each other than to C . snelliusi , and C . striolatus shows a close relationship to C . longitarsus . The close association of C . merguiensis with C . englaucus and C . humilis is strongly supported by the divergence of C . virescens from them. Our phylogenetic results contradict the morphological classifi cation scheme proposed for Clibanarius and indicate that the relative length of dactyls and propodi is not phylogenetically signifi cant in Clibanarius . In addition, we speculate that the morphological characteristic of the median cleft of the telson might be phylogenetically important for Clibanarius .     

Opportunistic-tended life history traits of Siniperca kneri in the Three Gorges Reservoir,China: potential responses to impoundment

Reservoir impoundment changes original fluvial habitats into lentic environments. Fish species adapted to lentic habitats may take the advantage of such habitat changes and show typical life history traits might facilitate the population increase. Siniperca kneri rarely occurred in fishery landing in the Three Gorges Reservoir (TGR) area before its impoundment in 2003, but it is now a dominant species. In this study, a total of 438 females of S . kneri were collected monthly during September 2012 through January 2014 using gill nets in the TGR. The age, growth, and reproductive biology were then investigated, and compared with other S . kneri populations. The standard length at age 1 was 149.9 mm in the TGR, which is larger than the three compared populations (i.e., Sandaohe Reservoir, Xinfengjiang Reservoir, and North River), but smaller than one (the Guishi Reservoir). The youngest mature female in the TGR was age 1, which is younger than that of the two compared populations (i.e., Xinfengjiang Reservoir and the North River). The relative fecundity in the TGR was 140 eggs/g, which is higher than that of the only available compared population (Xinfengjiang Reservoir, 96 eggs/g). Our results demonstrated that S . kneri in the TGR tended to have faster growth in the first year, a younger age at first maturation, and higher reproductive eff ort. We suggest that such opportunistic-tended life history traits might facilitate rapid increase of the population.     

运用人工鱼群算法的3D扫描碎片重建探究

针对传统三维碎片拼接匹配过程中依赖单一特征及存在误差累积的问题,提出了一种运用鱼群算法的全局最优匹配方法。该方法先对碎片点云数据进行多特征提取,结合纹理、专家经验信息对混合在一起的多种类型碎片进行粗糙集分类,之后采用鱼群算法的最优解求得最佳匹配方案。实例验证所提全局匹配方法具有能力强、与初始位置无关及较强的稳健性等特点,为三维碎片的全局匹配提供了一种有效的解决方案。     

秦岭地区NDVI与地形因子的相关性分析

秦岭山区地形因子是影响植被分布的重要因素。选取2001、2009和2017年MODIS陆地产品MOD13Q1数据和DEM数据,从DEM中提取地形因子,高程、坡度和坡向,与MODIS的NDVI数据结合,分析了地形对秦岭地区植被空间分布影响。研究结果表明:(1)NDVI随着高程的增大而逐渐增大,在高程1800 m左右时达到最大值,随后又随着高程的增大而减小;(2)NDVI在坡度0°～5°间逐渐增大,在5°～40°呈稳定趋势,从40°开始缓慢减小,60°达到乔木能够生长的坡面倾角临界值,当坡面倾角大于60°时植被指数开始快速减小;(3)受太阳辐射的影响,坡向在NW 270°～360°,SE 240°～270°之间的植被长势较好,其余坡向上长势一般。     

北极地区地缘关系研究综述

论文检索了科学引文索引(Web of Science)和中国知网(CNKI)中北极地区地缘关系的相关文献,借助CiteSpace文献分析软件的关键词共现分析功能,系统综述了2000年以来国内外关于北极地区地缘关系的研究重点。从研究内容上看,国外研究主要关注主权政治、航道利用、资源管理和原住民权益等主体性议题,而国内则着重关注地缘政治、航道交通、资源经济和地区治理等参与性议题。就研究方法上看,国内外研究中定性与定量方法兼具,但仍以定性方法和描述性方法为主。随着北极地区的发展,研究方法和研究视角有待丰富,研究领域和研究深度亟需进一步拓展和加强。北极地区具有重要的战略意义,未来应结合现代技术,借鉴国际上的地区发展理论,开展北极地区的可持续发展研究和中国参与研究,并构建新时代北极地区地缘环境理论。     

基于DEM分形特征的坡度尺度变换模型

利用DEM提取坡度具有明显的尺度依赖性,探求DEM在不同尺度下表现出的规律关系,建立多尺度变换模型,以实现不同尺度间的转换是地形分析研究的热点和难点。本文阐释了DEM表面与地表粗糙度分形维数值的地学意义及内在关系,并利用分形对象的自相似性原理,建立了一种基于DEM分形特征的坡度尺度变换模型。选取四川丘陵地区某小流域为研究区,进行坡度尺度变换实验和误差分析,结果表明该模型能有效实现坡度尺度变换:在非平坦地区(坡度>1°)一般重采样方法变换得到的坡度误差为该方法的1.86倍;从信息熵理论分析,经该方法转换后的坡度信息得到了显著恢复。对于无1︰1万及以上精度地形数据的西南山区,利用该方法获取高精度坡度数据具有重要的理论价值和现实意义。     

河流静水滩区潜流带水交换空间分布模式研究（英文）

Hyporheic zone(HZ) influences hydraulic and biogeochemical processes in and alongside streams, therefore, investigating the controlling geographic factors is beneficial for understanding the hydrological processes in HZ. Slack water pool (SWP) is an essential micro-topographic structure that has an impact on surface water and groundwater interactions in the HZ during and after high flows. However, only a few studies investigate HZ surface water and groundwater exchange in the SWP. This study used the thermal method to estimate the HZ water exchange in the SWP in a segment of the Weihe River in China during the winter season. The findings show that on the flow-direction parallel to the stream, river recharge dominates the HZ water exchange, while on the opposing flow-direction bank groundwater discharge dominates the water exchange. The water exchange in the opposing flow-direction bank is about 1.6 times of that in the flow-direction bank. The HZ water exchange is not only controlled by flow velocity but also the location and shape of the SWP. Great water exchange amount corresponds to the shape with more deformation. The maximum water exchange within the SWP is close to the river bank where the edge is relatively high. This study provides some guidelines for water resources management during flooding events.     

Assessment of Desert Ecological Assets and Countermeasures for Ecological Compensation

Can deserts be transformed into resources, into assets, and further into cash? It is necessary to scientifically assess desert ecological assets and incorporate them into the national economic accounting system and the current evaluation system for socio-economic development. This study will provide a scientific basis and robust data for establishing a target system that is compatible with both ecological civilization and an associated reward and punishment mechanism, as well as for designing and implementing effective compensation policies for desert ecosystems. This paper first defines desert ecological assets, and then develops a framework for assessing them based on the evaluation of desert ecological resources and desert ecosystem services. This framework paves the foundation for quantitatively assessing desert ecological assets and preparing balance sheets of desert ecological assets. Finally, this paper analyzes current policies relating to desert ecological compensation, discusses how to design compensation policies based on assessment of desert ecological assets, and puts forward suggestions for improving current policies.     

天然气水合物赋存区甲烷渗漏活动的地球化学响应特征

综述了天然气水合物赋存区甲烷渗漏活动的地球化学响应指标的研究进展,分析了应用单一指标识别甲烷渗漏活动各自所存在的问题,包括浅表层沉积物孔隙水中CH_4、SO_4~(2–)、Cl~–等离子浓度随深度的变化;浅层沉积物全岩W_(TOC)(W表示质量分数,TOC表示总有机碳)和W_(TS)(TS表示总硫)之间的相关性及比值;自生碳酸盐岩δ~(13)C和δ~(18)O;自生矿物重晶石、黄铁矿、自生石膏的δ~(34)S;有孔虫壳体和生物标志化合物的δ~(13)C等。结果表明孔隙水中的CH_4、SO4_~(2–)浓度及溶解无机碳的碳同位素组成可以用来识别目前正在发生的甲烷渗漏活动;而沉积物中的WTS、自生矿物的δ~(34)S、钡含量及其异常峰值和生物标志化合物的δ~(13)C等指标的联合使用可以更真实准确地反映地质历史时期天然气水合物赋存区的甲烷渗漏活动。因此,在实际研究过程中,可将孔隙水和沉积物两种介质的多种指标相结合。随着非传统稳定同位素(Fe、Ca、Mg等)和沉积物氧化还原敏感元素(Mo、V、U等)等研究的发展,甲烷渗漏活动地球化学响应指标的研究也将得到拓展,而多种地球化学指标的联合使用将为天然气水合物勘探及其形成分解过程识别研究提供重要的科学依据。     

黄河三角洲孤东近岸冲淤演变及其影响因素

为更好地了解近40年来孤东近岸的演变过程,以研究区剖面水深地形、Landsat影像和利津站水沙数据为数据源,采用遥感技术及数理统计法对研究区域岸线及面积变化进行监测计算,并分析1976—1986年、1986—1996年、1996—2002年、2002—2014年4个不同阶段的冲淤演变及影响因素。结果表明:(1)孤东近岸经历"强淤积-冲淤平衡-侵蚀-强侵蚀"4个阶段。孤东近岸海域由淤积向侵蚀转变始于1996年,且在2002—2014年间侵蚀最为严重,大部分近岸海域蚀深达到6～8 m,侵蚀最大深度超过8 m;(2)等深线变化时空差异明显,蚀退最先出现在北侧,且近岸5 m水深区域内冲淤变化较水深10 m内敏感;(3)研究区近岸侵蚀,离岸淤积,剖面冲淤平衡位置由CS19剖面的11 m水深变化到CS21剖面的5m水深;(4)黄河入海水沙的减少、河口人工改汊、孤东大堤建设和海洋动力作用都对孤东近岸的冲淤演变产生影响,维持研究区冲淤平衡的年均来沙阈值为3.78亿t/a。通过此来进一步探究孤东近岸演变进程,为孤东近岸防护提供科学指导。