Diving associated coral breakage in Hong Kong: Differential susceptibility to damage     

Alfred Cheuk-sun Au  Liye Zhang  Shan-shan Chung  Jian-Wen Qiu 《Marine pollution bulletin》2014

We conducted the first quantitative assessment of coral breakage along a gradient of diving activities in Hong Kong, the most densely populated city in southern China. A survey of six 1 × 25 m transects at seven sites revealed a total of 81 broken corals, among which 44% were branching, 44% plate-like and 12% massive. There were 3–19 broken colonies per site. At most study sites, the percentage of broken corals exceeded the recommended no-action threshold of 4%, suggesting that management intervention is justified. There was a significant positive correlation between the number of broken coral colonies and the number of divers visiting the site. The branching Acropora and the plate-like Montipora suffered from much higher frequency of damage than their relative abundance, raising the concern that the cumulative impact of such differential susceptibility to breakage may affect coral community composition.  相似文献   

Influence of river channel morphology and bank characteristics on water surface boundary delineation using high‐resolution passive remote sensing and template matching          下载免费PDF全文

İnci Güneralp  Anthony M. Filippi  Billy Hales 《地球表面变化过程与地形》2014,39(7):977-986

Accurate mapping of water surface boundaries in rivers is an important step for monitoring water stages, estimating discharge, flood extent, and geomorphic response to changing hydrologic conditions, and assessing riverine habitat. Nonetheless, it is a challenging task in spatially and spectrally heterogeneous river environments, commonly characterized by high spatiotemporal variations in morphology, bed material, and bank cover. In this study, we investigate the influence of channel morphology and bank characteristics on the delineation of water surface boundaries in rivers using high spatial resolution passive remote sensing and a template‐matching (object‐based) algorithm, and compare its efficacy with that of Support Vector Machine (SVM) (pixel‐based) algorithm. We perform a detailed quantitative evaluation of boundary‐delineation accuracy using spatially explicit error maps in tandem with the spatial maps of geomorphic and bank classes. Results show that template matching is more successful than SVM in delineating water surface boundaries in river sections with spatially challenging geomorphic landforms (e.g. sediment bar structures, partially submerged sediment deposits) and shallow water conditions. However, overall delineation accuracy by SVM is higher than that of template matching (without iterative hierarchical learning). Vegetation and water indices, especially when combined with texture information, improve the accuracy of template matching, for example, in river sections with overhanging trees and shadows – the two most problematic conditions in water surface boundary delineation. By identifying the influence of channel morphology and bank characteristics on water surface boundary mapping, this study helps determine river sections with higher uncertainty in delineation. In turn, the most suitable methods and data sets can be selectively utilized to improve geomorphic/hydraulic characterization. The methodology developed here can also be applied to similar studies on other geomorphic landforms including floodplains, wetlands, lakes, and coastlines. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

‘Universal’ recession curves and their geomorphological interpretation     

《Advances in water resources》2014

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金矿中的黄铁矿标型特征   总被引：9，自引：0，他引：9       下载免费PDF全文

李红兵  曾凡治 《地质找矿论丛》2005,20(3):199-203

黄铁矿是金矿中最常见的金属矿物,它不仅与金的矿化有着密切联系,而且还是主要的载金矿物.通过对黄铁矿的形态、物性、主成分及微量元素等标型特征的研究,可反映金矿床的不同成因,也是预测成矿远景地段、指导深部找矿的有效方法之一.文章对黄铁矿在金矿中的标型特征进行了归纳总结,以期对金矿床的勘探有一定的指导意义.  相似文献   

辽宁省凤城市林家金矿地质特征及成因探讨          下载免费PDF全文

刘恒刚  陈贺  赵经刚  李太阳 《地质找矿论丛》2009,24(1):66-68

林家金矿的赋矿地层为早元古界辽河群变质岩系,矿体形态产状严格受断裂控制,呈脉状、扁豆状产出,沿走向呈舒缓的波状,局部有膨缩变化,矿床成因类型为岩浆期后中低温热液充填交代型金矿床。  相似文献   

基于ENVI-met模式的城市近地表气温模拟与分析-以南京市部分区域为例     

祝善友  高牧原  陈亭  张桂欣 《气候与环境研究》2017,22(4):499-508

城市不同下垫面与建筑物空间形态对近地表气温等微气候要素产生了重要影响。开展城市气温时空变化模拟与影响因素分析,对于城市热环境评价与城市规划具有重要意义。论文基于高空间分辨率Geoeye-1立体影像,在建筑物高度、下垫面覆盖类型信息提取的基础上,选择南京一中、光华东街、玄武湖、头陀岭4个区域,采用ENVI-met微气候模式,以城市基本气象站南京站的实时气象数据作为背景气象场,模拟不同区域近地表气温的时空分布特征,并利用区域自动气象站观测数据进行精度检验。结果表明:在时间变化上,ENVI-met模拟气温与实测值之间吻合程度较高;在空间分布上,南京一中与光华东街区域气温时空分布规律总体相似,但城市空间形态的差异使得局部区域气温变化不同,玄武湖区域气温由陆地中心向外围呈递减趋势,而头陀岭地形复杂多变,白天气温变化剧烈,夜间空间变化较小。  相似文献   

基于形态分割的高分辨率遥感影像道路提取   总被引：27，自引：1，他引：26  

朱长青  王耀革  马秋禾  史文中 《测绘学报》2004,33(4):347-351

基于灰度形态学,提出一种从高分辨率遥感图像提取道路网络的方法.首先利用灰度形态特征对遥感影像进行分割,进而得到基本的道路网络轮廓.然后在此基础上,利用线段特征匹配方法提取道路网络.提出的方法能适应于从道路和背景区别不很清楚的遥感图像中提取道路.实验结果也表明,本文方法能有效地从遥感影像中提取道路网络.  相似文献   

基于SPOT遥感影像的九段沙潮沟信息提取及分维研究   总被引：2，自引：0，他引：2  

郭永飞  韩震 《海洋与湖沼》2013,44(6):1436-1441

以长江口九段沙为研究区, 应用灰度形态学提取了九段沙湿地的潮沟信息, 并对提取出的潮沟信息分区域采用网格法进行了分维研究, 得出了九段沙不同区域潮沟的分维值, 并对分维值进行了比较与分析。比较发现, 九段沙不同区域的分维值, 上沙最大, 下沙次之, 中沙最小。而在不同区域的不同岸段中, 处于上沙北部沿岸的潮沟分维值大于上沙其它地区; 处于中沙、下沙西北-东南沿岸的潮沟分维值分别大于中沙、下沙的其它地区。这主要与它们所处地理位置水动力条件不同有关。另外也计算了九段沙南岸与北岸的分维值, 发现南岸的分维值要大于北岸, 这与其发育时间、水动力条件和长江口深水航道工程等有一定联系。  相似文献   

Morphological analysis and recognition of scanned raster nautical chart     

Zhai Jingsheng  Li Deren 《Marine Geodesy》2013,36(4):325-339

In current practice in the development of hydrographic information systems, the automatic acquisition of spatial data has been considered to be very difficult. One of the key problems is recognition and correct separation of a feature from a complex graphic background. For these problems, this article presents a new concept of graph subsets to describe graph structures and composition rules of symbols in nautical charts. Based on this concept, morphological methods and operations in graph theory are unified into a coherent mathematical framework specially designed for analysis and recognition of binary chart images. In particular, an experimental system composed of feature extraction, symbol recognition, geometric reasoning, and intelligent control is developed for automatic digitization of nautical charts.  相似文献   

The fauna and chemical composition of some athalassic saline waters in New Zealand     

I. A. E. Bayly 《新西兰海洋与淡水研究杂志》2013,47(2):105-117

The fauna and chemical composition of two athalassic saline waters located near central Otago are discussed, and available rainfall and evaporation data for the region summarised. One water (dominated by Na and C1) had a salinity of 15‰ and contained the rotifer Brachionus plicatilis, the copepod Microcyclops monacanthus, the ostracod Diacypris, and larvae of the dipteran Ephydrella The second water (dominated by Na and HCO₃) had a salinity of 6‰ and contained larvae of Ephydrella (adults of E. novaezealandiae occurred on the shore), and the hemipterans Sigara arguta, Anisops wakefieldi and Anisops assimilis The relationship between Microcyclops monacanthus and M. arnaudi (an Australian species), and the basis of their current taxonomic separation is discussed in some detail.

At a minimum, the faunas of Australian and New Zealand athalassic saline waters have in common the following distinctive (non‐cosmopolitan) forms: Ephydrella, Diacypris, and two closely related halobiont species of Microcyclops  相似文献