Patterns and drivers of asteroid abundances and assemblages on the continental margin of Atlantic Canada

Although continental shelf and slope environments typically exhibit high epifaunal biomass and have been subjected to increasing fishing pressure, ecological information on assemblages of non‐commercial invertebrate species from subtidal and bathyal areas remains limited. Sea stars (Echinodermata: Asteroidea), which are known to influence communities through their feeding habits, have received less attention than structural taxa such as corals and sponges. To better understand the ecological roles of asteroids on continental shelves, we investigated ~30 species and assessed their distributions and co‐occurrence with other benthic invertebrates on the shelf and slope of Eastern Canada. Using fisheries data and in situ video footage, we compiled a large dataset covering ~600,000 km² that included over 350,000 individual asteroid records (37–2243 m depth). Multivariate analyses revealed geographically distinct asteroid assemblages, with a maximal overall density at 400–500 m and the highest diversity at 500–700 m. The most abundant and densely occurring species was Ctenodiscus crispatus. We found that asteroids associate with corals, sponges, bivalves, and other echinoderms, and that depth and substrate influence these assemblages. We identified species likely to affect coexisting organisms by their burrowing behavior that can disrupt epi‐ and infauna (C. crispatus) and through predation on ecologically important corals (Hippasteria phrygiana). In addition to providing baseline distribution and ecological information for many bathyal asteroid species in the Northwest Atlantic, this work highlights the abundance and diversified roles of asteroids within continental shelf and slope ecosystems.     

国土调查遥感40年进展与挑战

运用遥感技术进行土地资源调查,摸清其数量及分布状况,长期以来都是遥感领域研究的重要内容。本文首先回顾了过去40年来遥感技术在我国国土调查中的应用情况,然后围绕高分辨率影像的特征提取、大范围影像的样本获取、多时相/多传感器影像的迁移学习以及多源异构数据融合4个方面介绍了相关进展情况;接着归纳总结了现有遥感信息提取技术在国土调查中面临的4个挑战：① 高分辨率影像分类存在如何定义、选择、挖掘高级特征的问题;② 国土调查中的遥感数据集规模庞大,存在着类间不平衡和类内多样性,为这种复杂数据集获取足够、均衡、多样化的样本集是一个巨大挑战;③ 对于多传感器/多时相影像,如何低成本、及时地实现土地利用分类是值得考虑的问题;④ 从土地覆盖到土地利用存在语义鸿沟,如何合适地引入语义信息以弥合语义鸿沟需要被考虑。最后,本文对国土调查遥感技术的未来发展方向和应用点进行了展望。     

蓄水后向家坝库区鱼类物种、分类和功能多样性变化

为了解向家坝水电工程对金沙江下游鱼类多样性的影响,基于2016—2018年邵女坪(库首)、绥江(库中)和桧溪(库尾)3个江段的鱼类群落调查数据,分析了向家坝库区鱼类物种、分类和功能多样性空间格局,结合蓄水前(2011年)和蓄水初期(2015年)的资料,探讨了蓄水后向家坝库区不同维度鱼类多样性的变化趋势。向家坝库区各江段以广适性的瓦氏黄颡鱼(Pelteobagrus vachelli)和静水性的(Hemiculter leucisculus)占优势,两者的数量百分比分别为30.15%±14.82%和13.91%±11.16%。非度量多维尺度分析显示,蓄水后向家坝库区库首邵女坪和库中绥江鱼类群落差异最小,库首邵女坪和库尾桧溪鱼类群落差异最大;库中绥江在蓄水前、蓄水初期和2016—2018年3个时期的鱼类群落差异均较大,表明蓄水后绥江江段鱼类群落经历了剧烈变化。库区不同江段鱼类Margalef丰富度指数、Shannon-Wiener多样性指数和Pielou均匀度指数均表现为:桧溪>邵女坪>绥江,鱼类分类多样性指数和分类差异指数均表现为:桧溪>绥江>邵女坪。库区鱼类摄食、运动和繁殖等不同维度的功能多样性(功能丰富度、功能均匀度、功能离散度)空间格局不同,但总体上库中绥江鱼类功能丰富度最高,功能均匀度最低。与蓄水前相比,绥江江段鱼类物种、分类多样性呈下降趋势,鱼类功能丰富度和均匀度也有下降趋势。蓄水后绥江江段鱼类群落主要功能性状发生了明显变化,如蓄水前以下位口、纺锤形体型鱼类占优势,蓄水后以端位口、侧扁形体型鱼类占优势。不同维度多样性指数侧重于鱼类多样性的不同方面,结合多种指数分析有利于更全面地了解鱼类群落对环境变化和外界干扰的响应。研究结果有助于深入了解水电工程建设对金沙江下游鱼类多样性的影响,为鱼类多样性保护提供依据,也可为长江“十年禁渔”效果评估提供本底资料。     

Mapping favorable groundwater potential recharge zones using a GIS-based analytical hierarchical process and probability frequency ratio model:A case study from an agro-urban region of Pakistan

In Punjab(Pakistan),the increasing population and expansion of land use for agriculture have severely exploited the regional groundwater resources.Intensive pumping has resulted in a rapid decline in the level of the water table as well as its quality.Better management practices and artificial recharge are needed for the development of sustainable groundwater resources.This study proposes a methodology to delineate favorable groundwater potential recharge zones(FPRI) by integrating maps of groundwater potential recharge index(PRI) with the DRASTIC-based groundwater vulnerability index(VI).In order to evaluate both indexes,different thematic layers corresponding to each index were overlaid in ArcGIS.In the overlay analysis,the weights(for various thematic layers) and rating values(for sub-classes) were allocated based on a review of published literature.Both were then normalized and modified using the analytical hierarchical process(AHP) and a frequency ratio model respectively.After evaluating PRI and FPRI,these maps were validated using the area under the curve(AUC) method.The PRI map indicates that 53% of the area assessed exists in very low to low recharge zones,22% in moderate,and 25% in high to excellent potential recharge zones.The VI map indicates that 38% of the area assessed exists in very low to low vulnerability,33% in moderate,and 29% in high to very high vulnerability zones.The FPRI map shows that the central region of Punjab is moderately-to-highly favorable for recharge due to its low vulnerability and high recharge potential.During the validation process,it was found that the AUC estimated with modified weights and rating values was 79% and 67%,for PRI and VI indexes,respectively.The AUC was less when evaluated using original weights and rating values taken from published literature.Maps of favorable groundwater potential recharge zones are helpful for planning and implementation of wells and hydraulic structures in this region.     

嵌入式GIS中最优路径规划算法研究与实现

针对现有大区域范围路径规划算法存在的一些问题,提出一种多比例尺最优路径规划算法。该算法在进行路径规划时,在小区域范围内根据道路的属性信息对路网进行分层,在大区域范围内根据多比例尺信息对路网进行分级,在每级或每层内采用基于弧段的改进型A*算法。从实例分析可以看出,该算法能较好满足车载导航系统的需求。     

不同演替阶段人工柠条林丛枝菌根真菌分子多样性研究

采用PCR-DGGE和DNA克隆测序技术对黄土沟壑区一时间演替序列（5、13、20 a和42 a）上的人工柠条林的丛枝菌根真菌(Arbuscular Mycorrhizal Fungi;AMF)进行群落结构及多样性研究。结果显示,所有DNA序列聚为四个均属于AMF Glomus属的序列群,分别与Genbank上已登录的G.intraradices（同源性≥98%）、G. fasciculatum（=99%）、Glo18（=98%）和G. sp.（=98%）相关,这表明,在特定的时间点上柠条根系的AMF多样性十分低下。这四个序列群在5~20 a的柠条林中均出现,而在42 a的柠条林中只有G. sp.未出现,这表明,AMF群落组成并未随着柠条林的演替而发生显著改变,即AMF群落并未随着人工柠条林的恢复演替而得到恢复;土壤理化性质的稳定以及人工柠条林中的AMF群落与植被之间的正向反馈关系可能是导致这种现象的主要原因。     

白令海北部表层沉积物中细菌多样性的研究

提取白令海表层沉积物样品总DNA,构建沉积物中的细菌16SrDNA文库,通过RFLP酶切分型与序列测定,进行沉积物中的细菌多样性及系统发育分析。结果表明,该沉积物中细菌多样性丰富,获得的125条序列归属于10个细菌类群,包括占据优势地位的变形细菌(Pro-teobacteria,49.6%)、酸杆菌门(Acidobacteria,20.8%),以及拟杆菌门(Bacteroidetes,6.4%)、放线菌门(Actinobacteria,5.6%)、浮霉菌门(Planctomycetes,5.6%)、硝化螺旋菌门(Nitrospirae,4%)、疣微菌门(Verrucomicrobia,2.4%)、绿弯菌门(Chloroflexi,1.6%)、纤维杆菌门(Fibrobacteres,0.8%)、螺旋体(Spirochaetes,0.8%)。此外,还有一部分分类地位尚不明确的细菌(2.4%)。而在变形细菌中,δ、γ亚群为其中的优势类群。     

西藏土地利用综合分区

从西藏社会经济可持续发展的需要出发,开展西藏土地利用综合分区研究.依据2004年西藏土地利用数据,在全面分析西藏土地利用结构类型和社会经济发展的基础上,结合地域一致性,建立土地利用结构、经济指标体系,运用多元统计软件SPSS的系统聚类分析法,将西藏土地利用划分为藏中综合发展区、藏东农林牧区、藏南农牧区和藏北牧区,并综合分析评述了各分区土地利用现状、经济发展特征及土地利用功能与方向.     

Effects of relative motion between gas and liquid on 1-dimensional steady flow in silicic volcanic conduits: 2. Origin of diversity of eruption styles

We investigate the origin of diversity of eruption styles in silicic volcanoes on the basis of a 1-dimensional steady conduit flow model that considers vertical relative motion between gas and liquid (i.e., vertical gas escape). The relationship between the assemblage of steady-state solutions in the conduit flow model and magma properties or geological conditions is expressed by a regime map in the parameter space of the ratio of liquid-wall friction force to liquid–gas interaction force (non-dimensional number ε), and a normalized conduit length Λ. The regime map developed in the companion paper shows that when ε is smaller than a critical value ε_cr, a solution of explosive eruption exists for a wide range of Λ, whereas an effusive solution exists only when Λ ~ 1. On the other hand, when ε > ε_cr, an effusive solution exists for a wide range of Λ. Diversity of eruption styles observed in nature is explained by the change in ε accompanied by the change in magma viscosity during magma ascent. As magma ascends, the magma viscosity increases because of gas exsolution and crystallization, leading to the increase in ε. For the viscosity of hydrous silicic magma at magma chamber, ε is estimated to be smaller than ε_cr, indicating that an explosive solution exists for wide ranges of geological parameters. When magma flow rate is small, the viscosity of silicic magma drastically increases because of extensive crystallization at a shallow level in the conduit. In this case, ε can be greater than ε_cr; as a result, a stable effusive solution co-exists with an explosive solution.