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1.
万继康 《测绘与空间地理信息》2020,(1):72-75
针对研究城市热环境的过程中,利用归一化植被指数(NDVI)进行地表温度(LST)反演,再将LST和NDVI结合说明地物变迁与城市热环境的影响的现状,利用Landsat-8多时相遥感影像、高分辨率影像、公开GIS等多源数据,通过人工交互判读和量化统计分析,实现了2013—2017年北京建成区NDVI变化及其对地表热环境影响分析,再对分析结果进行差值拟合评价。对NDVI阈值分割按照大小为LC1、LC2、LC3、LC4,对LST分为高温区(TH)、常温区(TR)和低温区(TL)。结果表明,2013年至2017年:1)建成区的平均NDVI增加0.03,其中LC1增加1.0%,LC2减少11.6%,LC3区域减少1.7%,LC4区域增加12.3%。2)建成区平均LST增加2.55 K,TH百分比增加0.6%;TR百分比减少1.1%,TL百分比增加0.5%。3)NDVI相对增加,地表温度相对下降以及NDVI相对减少,地表温度相对上升占60%,NDVI相对下降,地表温度相对下降以及NDVI相对增加,地表温度相对上升的占40%。 相似文献
2.
在原有CHZ重力仪研制基础上,设计新一代海洋重力仪CHZ-Ⅱ并进行硬件搭建与测试。阐述了为CHZ-Ⅱ重力敏感结构设计的测试方案、实验过程及其结果分析,主要包括弹性系统的刚度、交叉耦合效应和漂移效应。实验表明,该结构在目前的测试内容下符合设计要求。 相似文献
3.
High‐resolution pollen, plant macrofossil and sedimentary analyses from early Holocene lacustrine sediments on the Faroe Islands have detected a significant vegetation perturbation suggesting a rapid change in climate between ca. 10 380 cal. yr BP and the Saksunarvatn ash (10 240±60 cal. yr BP). This episode may be synchronous with the decline in δ18O values in the Greenland ice‐cores. It also correlates with a short, cold event detected in marine cores from the North Atlantic that has been ascribed to a weakening of thermohaline circulation associated with the sudden drainage of Lake Agassiz into the northwest Atlantic, or, alternatively, a period with distinctly decreased solar forcing. The vegetation sequence begins at ca. 10 500 cal. yr BP with a succession from tundra to shrub‐tundra and increasing lake productivity. Rapid population increases of aquatic plants suggest high summer temperatures between 10 450 and 10 380 cal. yr BP. High pollen percentages, concentrations and influx of Betula, Juniperus and Salix together with macrofossil leaves indicate shrub growth around the site during the initial phases of vegetation colonisation. Unstable conditions followed ca. 10 380 cal. yr BP that changed both the upland vegetation and the aquatic plant communities. A decrease in percentage values of shrub pollen is recorded, with replacement of both aquatics and herbaceous plants by pioneer plant communities. An increase in total pollen accumulation rates not seen in the concentration data suggests increased sediment delivery. The catchment changes are consistent with less seasonal, moister conditions. Subsequent climatic amelioration reinitiated a warmth‐driven succession and catchment stabilisation, but retained high precipitation levels influencing the composition of the post‐event communities. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
互花米草入侵下福建漳江口红树林湿地土壤生态化学变化 总被引：1，自引：0，他引：1
采集了福建云霄漳江口米草入侵下红树林自然湿地保护区内红树林群落、米草群落、红树林—米草交互群落以及光滩的剖面土壤样品,分析了土壤的总养分库、有效养分库及微生物活性等指标。结果表明,不同植被群落下土壤理化性质均存在明显差异。土壤有机质、全氮、全磷、阳离子交换量和微生物生物量碳、氮在同一深度的含量变化为：红树林>红树林—米草混作>米草>光滩;土壤蔗糖酶、脲酶、磷酸酶、过氧化氢酶和多酚氧化酶等酶活性指标也表现出相似的变化趋势。从深度变化而言,上述各项土壤质量指标均随剖面深度而降低。米草入侵后土壤的各项养分指标均有明显下降,湿地土壤生态化学性质发生了明显的退化。土壤有机碳、土壤微生物生物量碳、氮含量以及土壤蔗糖酶与磷酸酶活性对滨海湿地土壤退化的反映最为强烈, 可以作为指示性指标。 相似文献
5.
A treeline can respond to climate change by shifting position, infilling, increasing recruitment, and increasing radial growth. More studies from understudied areas and their associated species are needed to understand treeline structure and dynamics. We established two transects of 20 m width and 120 m length (100 m above and 20 m below the forestline) in the Betula utilis subalpine forest of the Dhorpatan Hunting Reserve in Western Nepal. All individuals of B. utilis within the transects were classified into three height classes – trees (>2 m), saplings (0.5–2 m), and seedlings (<0.5 m) – and measured for morphometric features. Tree-ring cores were collected for age structure analysis. B. utilis forms an abrupt treeline in the region, and the mean forestline and treeline elevations were 3893 and 3898 m, respectively. The average age (57 yr) of trees at the treeline ecotone suggests a young stand. Poor regeneration was observed above the forestline in both transects when compared to below the forestline. Low regeneration at the treeline ecotone suggests site-specific biotic and abiotic controlling factors. Seedling and sapling establishment above the forestline is limited by a lack of moisture, absence of suitable microsites, and presence of herbivores. 相似文献
6.
大兴安岭北部地区落叶松和白桦树稀土元素分布特征 总被引：1，自引：1，他引：0
大兴安岭北部的落叶松和白桦树对稀土元素Eu选择吸收性十分明显.Eu的生物吸收系数是其它稀土元素的20倍以上.落叶松和白桦树稀土元素均具有明显的铕正异常.落叶松和白桦树对二价金属元素Zn、Sr也具有强烈的摄取能力,而对一价和高价金属元素吸收能力较弱.土壤的稀土元素不是影响植物中稀土元素分布特征的重要因素.该区落叶松和白桦树稀土元素分布特征与水-土壤-植物系统的物理化学条件具有密切的关系. 相似文献
7.
长白山岳桦林化学元素生物地球化学分析 总被引：14，自引：0，他引：14
从化学元素生物学和地球化学分类的角度,分析了大量营养元素,必需微量元素,可能必需元素,非必需元素和有毒元素在岳桦体内的含量特征和变化规律,结果表明,大量营养元素在岳桦体内的含量高于其它元素的含量;在新陈代谢旺盛的叶片中各类型元素含量均高于其它器官;化学性质和地球化学性质相近、生物学功能相似的大量营养元素和必需微量元素在岳桦不同器官中的含量变化具有相似的规律;其它三种类型的元素变化无规律可循,表明植 相似文献
8.
Climate change with respect to summer temperature throughout the Holocene is inferred from oscillations in the local Pinus sylvestris, Alnus incana and Betula pubescens forest‐lines, as recorded by fossil pollen and plant macrofossils in lake sediments at four altitudinal levels. Mt Skrubben (848 m a.s.l.), in Dividalen, was deglaciated down to below 280 m a.s.l. during 10 800–10 300 cal. yr BP. Betula pubescens established 10100 cal. yr BP at 280 m a.s.l. and expanded up to near the summit during the next 700 years. Birch woodland prevailed on the mountain plateau until 3300 cal. yr BP. Local Pinus sylvestris stands are recorded up to 400 m a.s.l. at 8450 cal. yr BP and >548 m a.s.l. about 8160 cal. yr BP. Alnus incana expanded from 400 to nearly 790 m a.s.l. during the period 7900–7600 cal. yr BP. The maximum forest distribution lasted until ca. 6000 cal. yr BP. Marked climatic deteriorations caused lowering of the forest‐lines around 4600 and 3000 cal. yr BP. Reconstruction of the summer temperature indicated mean July temperatures at 400 m a.s.l. of 1.5–3°C above the present during the period of maximum forest expansion, whereas >3°C above the present temperature at 548 m a.s.l. This is in accordance with other regional temperature reconstructions from northern Europe. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
9.
湖泊沉积物中DNA提取与PCR扩增 总被引：2，自引：0，他引：2
对湖泊沉积物中保存的生物大分子—DNA进行研究分析,以探讨湖泊生态系统随环境改变而演变的过程。根据前人对土壤和海洋沉积物DNA的提取方法,针对湖泊沉积物的特点进行改进,在此基础上对太湖梅梁湾湖泊沉积岩芯进行DNA提取和扩增。结果表明：不同深度湖泊沉积物均能获得DNA,且纯度较高,OD260/ OD280均大于1.4、OD260/ OD230大于1.1,可直接用于PCR（polymerase chain reaction ）扩增。对微囊藻的16S rRNA基因进行PCR扩增,结果发现在前5个沉积物样品中,均得到了200 bp左右的微囊藻16S rRNA基因片段,表明微囊藻或已降解的微囊藻基因片段存在于这5个层位的湖泊沉积物中。这为利用湖泊沉积物中的生物分子来推断历史湖泊生物群落结构,判断湖泊生态演变的历史提供了新的研究思路。 相似文献
10.
随着古气候和古环境研究的日渐深入,“特有种气候分析法”成为新生代定量重建古气候研究的重要方法之一。使用这一方法分析了浙江东部天台中新统下南山组的古亮叶桦（Betula mioluminifera Hu et Chaney）压型化石,研究了其叶结构特征及表皮微细构造,定量推论浙江天台中新世时年平均温度为12.5～22.1℃,春季平均温度为13.0～23.1℃,较现在温暖。我国内蒙、吉林、山东、云南等地的新近系发现过古亮叶桦,分布的北界为42°N。其现存最近亲缘种亮叶桦（Betula luminifera）生活在101～119°E,23～34°N之间,海拔500～1800 m的山区,是我国特有树种。亮叶桦分布范围的缩小显示中新世一段时期我国气候逐渐变冷的趋势。 相似文献