Predicting potential distributions of geographic events using one-class data: concepts and methods     

Q. Guo  W. Li  Y. Liu  D. Tong 《International journal of geographical information science》2013,27(10):1697-1715

One common problem with geographic data is that, for a specific geographic event, only occurrence information is available; information about the absence of the event is not available. We refer to these specific types of geospatial data as geographic one-class data (GOCD). Predicting the potential spatial distributions that a particular geographic event may occur from GOCD is difficult because traditional binary classification methods that require availability of both positive and negative training samples cannot be used. The objective of this research is to define GOCD and propose novel approaches for modelling potential spatial distributions of geographic events using GOCD. We investigate the effectiveness of one-class support vector machine (OCSVM), maximum entropy (MAXENT) and the newly proposed positive and unlabelled learning (PUL) algorithm for solving GOCD problems using a case study: species distribution modelling from synthetic data. Our experimental results indicate that generally OCSVM, MAXENT and PUL are effective in modelling the GOCD. Each method has advantages and disadvantages, but PUL seems to be the most promising method.  相似文献   

南流江河口红树林潮沟主要鱼类时空生态位     

承亚男  黄欣  吴志强  刘昊  徐浩  苏琼源  朱亮  胥鹏  黄亮亮 《热带地理》2023,43(1):59-70

基于2019年7月(夏)、2019年10月(秋)、2020年1月(冬)、2020年5月(春)的季节性鱼类采样数据,运用相对重要性指数(IRI)、Shannon指数和Pianka指数对南流江河口红树林潮沟主要鱼类的时空生态位宽度和重叠进行分析,结合冗余分析探讨主要鱼类间的生态位分化。结果表明：共采集到鱼类17 680尾,隶属12目23科37属45种,其中主要鱼类(IRI>100) 10种。在主要鱼类中,时间生态位宽度值变化范围为0.46～1.78,其中嵴塘鳢最大,爪哇拟虾虎鱼最小;空间生态位宽度值变化范围为0.81～2.05,其中斑尾刺虾虎鱼最大,爪哇拟虾虎鱼最小。时空生态位宽度值达到2以上(广生态位种)的种类有6种,分别是鲻、齐氏罗非鱼、中华乌塘鳢、斑尾刺虾虎鱼、嵴塘鳢和杂食豆齿鳗。鲻与爪哇拟虾虎鱼的时间生态位重叠值最高(0.928),尾纹双边鱼与食蚊鱼的空间生态位重叠值最高(0.979),齐氏罗非鱼与斑尾刺虾虎鱼的时空生态位重叠值最高(0.822)。南流江河口红树林潮沟主要鱼类时空二维生态位有6.7%的种对显著重叠(Q_ik>0.6),表明物种时空分布...  相似文献   

基于生态位理论的重庆市物流企业优势区位及影响因素研究     

刘思婧  孙文杰  李国旗 《地理科学》2020,40(3):393-400

基于重庆市5 937家物流企业,采用物流企业生态位模型和计数模型,从多尺度甄别物流企业优势区位及影响因素。结果表明：① 在区县尺度上,生态位宽度处于高中低水平的区县分别有8、8、22个,围绕主城区和万州区呈现“一主一副”的空间结构;② 在街道尺度上,物流企业密度处于前3层的29个街道中仅有1个街道的物流企业态处于前3层,物流企业密度处于后3层的413个街道中有29个街道的物流企业态处于前3层,态值与密度空间分布总体不协调,高密度低态值问题突出;③ 商品交易市场交易额和是否有物流节点布局与物流企业数量高度正相关,不受规模影响;对物流企业规模加权后,工业产值被是否有港口布局因素取代。  相似文献   

基于均分法的小生境遗传算法     

赵远东  汪怡 《南京气象学院学报》2013,5(6):553-556

为了避免遗传算法种群中个体过早陷入局部最小,在以往随机初始种群的基础上提出一种均分法,使得初始种群随机平均地分为若干个子种群,形成小生境,这样既维持了种群的多样性,也使得种群中的个体不会过早出现早熟现象,更提高了算法的收敛速度.同时采用了自适应技术控制交叉和变异的概率,使得算法能更快速地找到最优解.仿真结果表明,与传统的遗传算法优化RBF网络相比较,新算法的迭代次数更少,精度更高,大大提高了收敛速度.  相似文献   

行政区域界线破幅控制面积算法研究     

侯恩兵  周国祥  马卫春 《测绘科学》2009,34(6)

计算行政区域界线的破幅控制面积,是第二次全国土地调查中计算整个行政区域界线控制面积的一个核心问题。本文作者综合利用计算机图形学、地理信息系统及数学模型知识,提出了一种计算方法。利用该算法,作者对安徽省境内1∶10000标准分幅下的行政区域界线的控制面积进行了计算,精度满足了实际工作的需要,具有推广价值。  相似文献   

Recognition and palaeoclimatic implications of late Quaternary niche glaciation in eastern Lesotho     

Stephanie C. Mills  Stefan W. Grab  Simon J. Carr 《第四纪科学杂志》2009,24(7):647-663

Geomorphic evidence of former glaciation in the high Drakensberg of southern Africa has proven controversial, with conflicting glacial and non‐glacial interpretations suggested for many landforms. This paper presents new geomorphological, sedimentological and micromorphological data, and glacier mass‐balance modelling for a site in the Leqooa Valley, eastern Lesotho, preserving what are considered to be moraines of a former niche glacier that existed during the Last Glacial Maximum (LGM). The geomorphology and macro‐sedimentology of the deposits display characteristics of both active and passive transport by glacial processes. However, micromorphological analyses indicate a more complex history of glacial deposition and subsequent reworking by mass movement processes. The application of a glacier reconstruction technique to determine whether this site could have supported a glacier indicates a reconstructed glacier equilibrium line altitude (ELA) of 3136 m a.s.l. and palaeoglacier mass balance characteristics comparable with modern analogues, reflecting viable, if marginal glaciation. Radiocarbon dates obtained from organic sediment within the moraines indicate that these are of LGM age. The reconstructed palaeoclimatic conditions during the LGM suggest that snow accumulation in the Drakensberg was significantly higher than considered by other studies, and has substantial relevance for tuning regional climate models for southern Africa during the last glacial cycle. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

剑叶金鸡菊对植物群落结构的影响   总被引：1，自引：0，他引：1  

许媛  孙进  王军  王年爽  孙颖材  宫相忠 《海洋湖沼通报》2009,(2)

剑叶金鸡菊(Coreopsis lanceolata)原产北美,19世纪德国占领青岛时作为花卉植物带入.现在已经逸生为青岛常见外来杂草.本文调查了剑叶金鸡菊入侵地植物群落的多样性指数和剑叶金鸡菊与群落中其它伴生植物的生态位重叠值.结果表明:(1)入侵样地植物群落物种多样性指数随剑叶金鸡菊重要值的增加而下降;(2)7、8月份,与剑叶金鸡菊生态位重叠值较大的物种有野青茅,画眉草,鸭跖草,狗尾草,美洲商陆;(3)剑叶金鸡菊有很强的竞争生存能力,其扩散受人为因素影响较大.  相似文献   

西部干旱区省会城市生态经济位比较研究     

徐厚琴  方一平 《干旱区地理》2007,30(3):26-430

从生态经济位理论出发,提出了城市生态经济位概念及度量方法,并根据生态经济位计算模型,从社会、经济和环境因子三个层面归结了30个指标,建立了定量评价指标体系,依此测算了2002年、2003年西部干旱区6个省会城市的生态经济位,得出2002年和2003年在西部干旱区省会城市中,乌鲁木齐的生态经济位最大,西宁的生态经济位最小的结论。文章最后分析、解释了西部干旱区6省会城市生态经济位动态变化及其原因。  相似文献   

Ecological patterns and sustainability of freshwater swamp forest ecosystems: assessing climate and disturbance interactions     

《Singapore journal of tropical geography》2018,39(1):62-74

Species composition and factors that control the distribution of freshwater swamp forests in West Africa are largely unknown. To achieve this, 24, one‐hectare forest plots were established to assess the tree species (DBH ≥ 10 cm) distribution across the ecosystem. A total of 138 species within 100 genera and 41 families were distributed across the forest plots and 47 species were identified as indicator species. These indicator species were used to constrain the species‐environmental categories across three broad habitat types: the disturbed freshwater zone, the mangrove‐freshwater transition zone and the intact freshwater zone. While 40 species are associated with one of the three forest categories, seven of them coexisted in disturbed and mangrove‐freshwater zones. Disturbance (local factors) was identified as the most important determinant of the species distribution followed by the climatic factors. Future climate predictions for the locations are quite variable and suggest that some species may be non‐viable as the ecosystem's composition may alter. While the indicator species provides insights on the species‐environment relationships, and is useful for informing forest conservation and planning, their tendency to continually co‐exist with others and provide vital functions is dependent on how sustainably the people use them.  相似文献   

基于生态位理论的山东省城市旅游竞争力评价及空间格局研究     

李淑娟  王肖  隋玉正 《地域研究与开发》2017,36(5)

基于生态位理论,通过构建市场维、资源维、社会经济维、生态环境维的指标体系,评价2004—2009,2009—2014年山东省城市旅游竞争力,根据聚类分析结果和核心边缘理论,建立山东省城市旅游竞争力空间格局。研究发现:青岛市城市旅游综合竞争力排名稳居第一,烟台市、济南市紧随其后,其余城市的排名变化不大;山东省城市旅游竞争力呈现核心城市—次级城市—边缘城市的空间格局。核心城市可采取协同发展策略,带动和辐射周边城市的发展;次级城市重在加强市场营销,提升市场竞争力;边缘城市以特色策略为主,生态位扩充策略为辅,扩大生态位,提高城市旅游竞争力。  相似文献