排序方式: 共有35条查询结果,搜索用时 31 毫秒
21.
本文根据无人机工作环境限制少、操作灵活、可控性高等特点,利用无人机航测技术实现建设适宜性分析的优化与改进,有效解决了建设适宜性分析区域面积大、地势复杂、影响因素众多、传统测量手段局限性大等问题。利用无人机航测技术实现了航测数据分类采集与测绘元素分类建模,为航测成果叠加提供了更加准确独立的数据基础,对建设适宜性分析的元素选择提供了更大的空间,使航测成果叠加运算更加灵活可控、准确高效。 相似文献
22.
To understand the ecological status and macrobenthic assemblages of the Xin'an River Estuary and its adjacent waters, a survey was conducted for environmental variables and macrobenthic assemblage structure in September 2012(Yantai, China). Several methods are adopted in the data analysis process: dominance index,diversity indices, cluster analysis, non-metric multi-dimentional scaling ordination, AMBI and M-AMBI. The dissolved inorganic nitrogen and soluble reactive phosphorus of six out of eight sampling stations were in a good condition with low concentration. The average value of DO((2.89±0.60) mg/L) and p H(4.28±0.43) indicated that the research area faced with the risk of ocean acidification and underlying hypoxia. A total of 62 species were identified, of which the dominant species group was polychaetes. The average abundance and biomass was577.50 ind./m2 and 6.01 g/m2, respectively. Compared with historical data, the macrobenthic assemblage structure at waters around the Xin'an River Estuary was in a relatively stable status from 2009 to 2012.Contaminant indicator species Capitella capitata appeared at Sta. Y1, indicating the animals here suffered from hypoxia and acidification. AMBI and M-AMBI results showed that most sampling stations were slightly disturbed,which were coincided with the abiotic measurement on evaluating the health conditions. Macrobenthic communities suffered pressures from ocean acidification and hypoxia at the research waters, particularly those at Stas Y1, Y2 and Y5, which displays negative results in benthic health evaluation. 相似文献
23.
古代鉴湖兴废与山会平原农田水利 总被引:3,自引:0,他引:3
鉴湖又称镜湖,还有南湖、长湖、大湖、贺监湖等许多别名,是长江以南最古老的大型农田水利工程之一。由于其对古代山会平原农田水利上的重要作用,因而成为我国东南地区历史上的著名湖泊。解放以来,地理学界对于古代鉴湖地区(即目前的萧绍平原)现 相似文献
24.
25.
一部反映北京地区历史早期人类活动与自然环境的地图集《北京历史地图集二集》于1997年2月由北京出版社出版。该图集由我国著名历史地理学家侯仁之教授主编。无论从北京地区历史地理研究还是从历史地理学的学科角度看,该图集都有许多特点、贡献和作出了有益的探索。 相似文献
26.
27.
为探明现阶段太湖流域江苏片区底栖大型无脊椎动物群落结构及物种多样性,于2013年1—3、7—8和10—11月对120个样点开展了调查.共记录6门124科280种,各点位物种数(4~51种)、个体密度(5.5~23363.4 ind./m~2)和生物量(0.1~6269.2 g/m~2)差异较大.不同水体类型的群落结构存在显著差异,其中溪流以蜉蝣目和毛翅目等水生昆虫为优势,水库以摇蚊为优势,河流以寡毛纲为绝对优势,湖荡以寡毛纲、摇蚊幼虫和软体动物为优势.聚类结果显示,同水体类型点位的群落结构也呈现不同程度的空间差异.结合丰度/生物量曲线、特征种及多样性分析,各聚类组受胁迫程度从轻到重依次为溪流(组Ⅸ),太湖敞水区(组Ⅱ)和东部水草区(组Ⅲ),太湖下游湖荡(组Ⅳ)、河流(组Ⅵ)和水库(组Ⅶ),太湖上游湖荡(组Ⅰ)、其他河流(组Ⅴ)和水库(组Ⅷ)点位.底栖大型无脊椎动物的分布与物理生境和水质条件呈较好的空间一致性,生境的多样性和良好的水质条件是保护和恢复物种多样性的关键因素. 相似文献
28.
29.
30.