岛屿海岸线自动化提取及其时空变迁研究——以大连市獐子岛为例   总被引：1，自引：1，他引：0  

丁小松  单秀娟  陈云龙  金显仕  杨涛 《海洋科学》2018,42(2):46-55

海岸带是受人类活动和全球海平面上升影响的敏感地带,海岸线的提取和监测是海岸带生态系统研究和社会管理的重要内容。本文在遥感和地理信息系统的支持下,以修正的归一化水体指数(Modified Normalized Difference Water Index,MNDWI)为基础,结合遥感影像处理和直方图均衡化等技术,实现了大连市獐子岛1985—2016年海岸线的自动化提取。结果表明:(1)通过与三位专家目视解译的成果比对,本文提取海岸线的精度能满足后续研究的要求(相对误差分别为0.045%,0.032%和0.023%);(2)近30年来,獐子岛海岸线总体呈现蚀退趋势,岸线长度与岛屿面积分别呈现变短和变小的趋势,獐子岛(主岛)和大耗岛的岸线蚀退速率最大,褡裢岛次之,小耗岛最小;在人类活动较为密集的区域,海岸线呈现出较为强烈的增长趋势,海水养殖和圈海建坝是岸线增长的主要驱动力;(3)獐子岛海岸线具有显著的分形性质,分形维数随时间呈现增大的趋势,獐子岛(主岛)的分形维数最大,褡裢岛的分形维数最小。  相似文献   

1970-2016年青藏高原岗扎日冰川变化与物质平衡遥感监测研究     

张震  刘时银 《地球信息科学学报》2018,20(9):1338-1349

可可西里处于青藏高原腹地,是青藏高原自然环境的交接与过渡地带。近年来该区域冰川物质平衡可能有从西向东由正转负的趋势,但是其过渡地带岗扎日地区冰川状态未知。本研究利用地形图、SRTM、ASTER和Landsat等资料分析了岗扎日地区冰川面积变化和物质平衡变化,并对可可西里地区冰川变化空间规律进行了探讨,结果表明：①1970-2016年岗扎日冰川总面积年均缩小率为0.08±0.02%。2006年后冰川退缩趋势减缓。②1970-2012年岗扎日冰川平均减薄-8.64±0.30 m,体积减少1.45±0.06 km³,平均物质平衡为-0.21±0.01 m w.e. a^-1。冰川物质平衡趋势由负转正（1970-1999年：-0.34±0.01 m w.e. a^-1;1999-2012：0.16±0.02 w.e. a^-1）。③东南、南、西南朝向作为迎风坡,1970年以来其冰川物质亏损较小,1999-2012年呈现强烈的正平衡。冰川面积变化滞后于物质平衡变化,东朝向和东南朝向冰川面积缩小率最大,主要是因为冰川冰舌较长,末端所处的海拔较低。④气温升高是岗扎日冰川1970-1999年呈现负物质平衡状态的主因,降水增多是1999-2012年正平衡状态的主因。⑤可可西里地区冰川1970s以来面积年均缩小率从西向东不断增大、物质平衡下降,与西风环流和季风环流相关,但局地气候也影响冰川变化和物质平衡。  相似文献   

Modelling the effect of changing precipitation inputs on deep soil water utilization          下载免费PDF全文

Ji Qi  Daniel Markewitz  David Radcliffe 《水文研究》2018,32(5):672-686

Forests in the Southeastern United States are predicted to experience future changes in seasonal patterns of precipitation inputs as well as more variable precipitation events. These climate change‐induced alterations could increase drought and lower soil water availability. Drought could alter rooting patterns and increase the importance of deep roots that access subsurface water resources. To address plant response to drought in both deep rooting and soil water utilization as well as soil drainage, we utilize a throughfall reduction experiment in a loblolly pine plantation of the Southeastern United States to calibrate and validate a hydrological model. The model was accurately calibrated against field measured soil moisture data under ambient rainfall and validated using 30% throughfall reduction data. Using this model, we then tested these scenarios: (a) evenly reduced precipitation; (b) less precipitation in summer, more in winter; (c) same total amount of precipitation with less frequent but heavier storms; and (d) shallower rooting depth under the above 3 scenarios. When less precipitation was received, drainage decreased proportionally much faster than evapotranspiration implying plants will acquire water first to the detriment of drainage. When precipitation was reduced by more than 30%, plants relied on stored soil water to satisfy evapotranspiration suggesting 30% may be a threshold that if sustained over the long term would deplete plant available soil water. Under the third scenario, evapotranspiration and drainage decreased, whereas surface run‐off increased. Changes in root biomass measured before and 4 years after the throughfall reduction experiment were not detected among treatments. Model simulations, however, indicated gains in evapotranspiration with deeper roots under evenly reduced precipitation and seasonal precipitation redistribution scenarios but not when precipitation frequency was adjusted. Deep soil and deep rooting can provide an important buffer capacity when precipitation alone cannot satisfy the evapotranspirational demand of forests. How this buffering capacity will persist in the face of changing precipitation inputs, however, will depend less on seasonal redistribution than on the magnitude of reductions and changes in rainfall frequency.  相似文献   

不同盐度对文蛤(Meretrix meretrix)呼吸代谢及体内酶活性的影响     

白奕天  丁天扬  李东东  聂鸿涛  闫喜武 《海洋科学》2018,42(6):123-131

为研究不同盐度对文蛤呼吸代谢的影响,本实验设置5个盐度(‰)梯度(11、18、25、32、39),检测不同盐度对文蛤(Meretrixmeretrix)耗氧和排氨的影响,以及文蛤的外套膜、鳃、肝胰腺三种组织中乳酸脱氢酶和Na+/K+-ATP酶活性的变化。结果表明:随着盐度的不断升高,文蛤耗氧率先升后降再升,在盐度18时达到最大值;排氨率先升后降,在盐度32时达到最大值。随着盐度不断升高和胁迫时间延长,文蛤的肝胰腺中乳酸脱氢酶活力总体呈先升高后下降再升高的趋势(P0.05),酶活力在盐度39时为最高;随着盐度不断升高和胁迫时间延长,文蛤的外套膜中Na+/K+-ATP酶活力总体呈先下降再升高后下降的趋势(P0.05),在盐度32时为最高;文蛤的外套膜和鳃中乳酸脱氢酶活力以及鳃和肝胰腺中Na+/K+-ATP酶活力受盐度影响不显著(P0.05),酶活力变化也多呈现"W"形的变化趋势。研究结果为文蛤的人工养殖提供参考。  相似文献   

Terrestrial discharge influences microbioerosion and microbioeroder community structure in coral reefs     

SA Mwachireya  M Carreiro-Silva  BE Hartwick  TR McClanahan 《African Journal of Marine Science》2018,40(1):25-42

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m^?2 y^?1 (SEM) and 134.7 g CaCO₃ m^?2 y^?1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO₃ m^?2 y^?1), which was almost double that in the pristine reef (69.5 g CaCO₃ m^?2 y^?1) and the mangrove-fringed reef (56.2 g CaCO₃ m^?2 y^?1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future.  相似文献   

中国大城市的城市组成对城市热岛强度的影响研究     

王美雅  徐涵秋 《地球信息科学学报》2018,20(12):1787-1798

城市的快速扩张诱发并加剧了城市热岛效应,对人类健康和生存发展提出严峻挑战,因此,探索城市组成对城市热岛的影响具有重要意义。本研究在传统城市热岛影响因子的基础上,重点分析城市组成与城市热岛的关系。以13个中国大城市为研究区,利用2015年夏季（6-8月）白天和夜间的MODIS LST数据计算城市热岛强度,并结合土地覆盖数据、人口、区位和气象数据,分析热岛强度和城市地表组成、地表空间格局、人口和区位4类因子的关系。研究结果表明：中国的13个大城市均存在不同程度的热岛效应,城市白天的热岛效应比夜间显著。影响城市白天热岛强度的主要因子为城市建筑用地和林地面积比例、城市建筑用地和林地平均斑块面积、城市建筑用地聚集度和人口密度。城市建筑用地和林地平均斑块面积、城市建筑用地聚集度和林地斑块密度是夜间热岛强度的主要影响因子。城市建筑用地面积和乡村林地面积的增加会导致城市热岛情况的加剧,而通过调节城市地表空间格局（减少平均建筑用地斑块面积和降低建筑用地斑块聚集度）可以更好地降低城市地表温度,减缓城市热岛效应。  相似文献   

从第三极到北极： 积雪变化研究进展   总被引：5，自引：5，他引：0  

刘一静  孙燕华  钟歆玥  王树发  肖雄新  马丽娟  苏航  赵文宇  张廷军 《冰川冻土》2020,42(1):140-156

在全球气候变化背景下， 第三极和北极地区积雪是地表最活跃的自然要素之一， 其动态变化对气候环境和人类生活产生重要影响。通过回顾第三极和北极积雪研究进展， 阐述了降雪、 积雪范围、 积雪日数、 积雪深度和雪水当量在第三极和北极地区的时空分布特征和变化趋势。结果表明： 近50年， 特别是进入21世纪以来， 第三极和北极地区降雪比率均呈下降趋势； 积雪范围、 积雪日数、 积雪深度、 雪水当量总体均呈减小趋势， 融雪首日有所提前。同时就积雪变化对生态系统与气候系统的影响进行了论述， 评估了积雪的反馈作用。通过总结第三极和北极积雪变化研究进展， 凝练研究中存在的不足和未来发展趋势， 为提升积雪对气候变化及经济社会发展影响的认识提供重要科学支撑。  相似文献   

贵州省沿河县耕地土壤元素地球化学特征及其特色耕地利用建议          下载免费PDF全文

石睿  张锡贵 《贵州地质》2020,37(3):266-272

针对现有烟包上包机存在的占地面积过大，易发生掉包以及移动困难等问题，设计了一种基于可编程逻辑控制器（PLC)控制的新型烟包上包机。该设备采用提升链条为输送装置，可以对烟包进行垂直运输，从而减小占地面积；以托盘作为烟包输送的载体，可以使烟包在上包过程中放置平稳，减小掉包的可能性。利用SolidWorks软件完成整机机械结构的三维建模，采用PLC控制系统来控制烟包上包机的上包作业流程。与传统的烟包上包机相比，该新型烟包上包机具有占地面积小，上包作业过程运行平稳，操作简单轻便等优点，可适应多种工作场所。  相似文献   

Environmental change and the informal plastic recycling networks of Kolkata     

Nicolas Schlitz 《Singapore journal of tropical geography》2020,41(3):450-467

This article introduces plastic recycling networks in Kolkata, India, as a case to illustrate the contradictory entanglement of economic and environmental change in urban informal contexts of the Global South. In light of the prevailing environmental critique of informal plastic recycling in India, this article discusses plastic recyclers’ environmental impact and contribution as well as the potential to enhance the environmental and economic performance of their business. Network and chain approaches in the emerging field of Environmental Economic Geography are combined with the notion of social metabolism to conceptualize the entanglement of environmental and economic processes as well as socio-environmental inequalities entailed in recycling networks. The analysis reveals the impact that the heterogeneity and fluctuation of plastic waste supply has on the economic organization of recycling networks, giving rise to distinct forms of governance in its intermediate and down-stream segments. Such an integrated perspective also serves to explain why environmental upgrading is hard to achieve under prevailing circumstances by plastic recyclers in Kolkata. Based on an assessment of the social and political conditions of informality under which plastic recyclers operate, the adoption of common assumptions about ecological modernization imbuing parts of Environmental Economic Geography is called into question.  相似文献   

Tectonostratigraphic framework and depositional history of the deepwater Ulleung Basin,East Sea/Sea of Japan     

Kyoung-Jin Kim  Dong-Geun Yoo  Nyeon-Keon Kang  Bo-Yeon Yi 《Basin Research》2020,32(4):613-635

The Ulleung Basin, East Sea/Japan Sea, is a Neogene back-arc basin and occupies a tectonically crucial zone under the influence of relative motions between Eurasian, Pacific and Philippine Sea plates. However, the link between tectonics and sedimentation remains poorly understood in the back-arc Ulleung Basin, as it does in many other back-arc basins as well, because of a paucity of seismic data and controversy over the tectonic history of the basin. This paper presents an integrated tectonostratigraphic and sedimentary evolution in the deepwater Ulleung Basin using 2D multichannel seismic reflection data. The sedimentary succession within the deepwater Ulleung Basin is divided into four second-order seismic megasequences (MS1 to MS4). Detailed seismic stratigraphy interpretation of the four megasequences suggests the depositional history of the deepwater Ulleung Basin occurred in four stages, controlled by tectonic movement, volcanism, and sea-level fluctuations. In Stage 1 (late Oligocene through early Miocene), syn-rift sediment supplied to the basin was restricted to the southern base-of-slope, whereas the northern distal part of the basin was dominated by volcanic sills and lava flows derived from initial rifting-related volcanism. In Stage 2 (late early Miocene through middle Miocene), volcanic extrusion occurred through post-rift, chain volcanism in the earliest time, followed by hemipelagic and turbidite sedimentation in a quiescent open marine setting. In Stage 3 (late middle Miocene through late Miocene), compressional activity was predominant throughout the Ulleung Basin, resulting in regional uplift and sub-aerial erosion/denudation of the southern shelf of the basin, which provided enormous volumes of sediment into the basin through mass transport processes. In Stage 4 (early Pliocene through present), although the degree of tectonic stress decreased significantly, mass movement was still generated by sea-level fluctuations as well as compressional tectonic movement, resulting in stacked mass transport deposits along the southern basin margin. We propose a new depositional history model for the deepwater Ulleung Basin and provide a window into understanding how tectonic, volcanic and eustatic interactions control sedimentation in back-arc basins.  相似文献