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1.
Botany of two Antarctic mountain ranges: Gjelsvikfjella and Muhlig-Hofmannfjella, Dronning Maud Land
TORSTEIN ENGELSKJøN 《Polar research》1986,4(2):205-224
The investigated area is located between 71°45' and 72°20'S and between 1°35' and 5°33'E, from 1, 080 to 2, 695 m above sea level. An outline of climate, soil chemistry and main units of vegetation is provided. Of particular importance is the wet oasis area of Jutulsessen in Gjelsvikfjella which supports cyanophyceans, green algae, lichens and the mosses Grimmia lawiana and Sarconeurum glaciate , which have developed a series of distinctive communities. The nunataks fringing the Polar plateau harbour an impoverished cyanophycean and lichen vegetation up to approximately 2, 500 m a.s.l., which is the highest elevation that macroscopic plant life has hitherto been reported in Antarctica. The thermal relations of the vegetation are discussed, based on the climatological record and on local measurements during the Norwegian Antarctic Research Expedition 1984/85. Some zonal and vertical belt subdivisions are indicated for this part of Greater Antarctica. 相似文献
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Richard A. Armstrong 《Geografiska Annaler: Series A, Physical Geography》2014,96(2):217-226
Variation in lichen growth rates poses a significant challenge for the application of direct lichenometry, i.e. the construction of lichen dating curves from direct measurement of growth rates. To examine the magnitude and possible causes of within‐site growth variation, radial growth rates (RaGRs) of thalli of the fast‐growing foliose lichen Melanelia fuliginosa ssp. fuliginosa (Fr. ex Duby) Essl. and the slow‐growing crustose lichen Rhizocarpon geographicum (L.) DC. were studied on two S‐facing slate rock surfaces in north Wales, UK using digital photography and an image analysis system (Image‐J). RaGRs of M. fuliginosa ssp. fuliginosa varied from 0.44 to 2.63 mm yr–1 and R. geographicum from 0.10 to 1.50 mm yr–1.5. Analysis of variance suggested no significant variation in RaGRs with vertical or horizontal location on the rock, thallus diameter, aspect, slope, light intensity, rock porosity, rock surface texture, distance to nearest lichen neighbour or distance to vegetation on the rock surface. The frequency distribution of RaGR did not deviate from a normal distribution. It was concluded that despite considerable growth rate variation in both species studied, growth curves could be constructed with sufficient precision to be useful for direct lichenometry. 相似文献
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《自然地理学》2013,34(2):183-192
Rock outcrops along ridgelines, in block fields, and on cliff faces of Shenandoah National Park (SNP) provide unique habitats for numerous rare and endemic biotas. However, there are recent concerns about the long-term sustainability of these populations because of increased park usage (e.g., hiking, rock climbing) and environmental change (e.g., air chemistry, quality). Analysis of lichen-population dynamics provides insight into the rate at which these habitats are being degraded. As such, there is a need to develop a method to rapidly and accurately assess changes in lichen communities through space and over time. This study presents a new approach designed to record lichen species on rock outcrops. Terrestrial laser scanning (TLS) offers a new technique for recording individual lichen species (e.g., abundance, spatial distribution, extent, size, shape). An automated process is described to extract the lichen extent and shape in a standard GIS environment. These data are used to examine size classes, frequency, percent cover, and spatial pattern of a species of Phlyctis. The methodology and data extracted greatly improve rapid assessments and long-term monitoring of lichen populations. 相似文献
4.
Age and hydrological significance of lichen limits on sandstone river channels near Sydney,Australia
Jesmond Sammut Wayne D. Erskine 《Geografiska Annaler: Series A, Physical Geography》2013,95(3):227-239
Trimmed lichen communities (lichen limits) are abrupt changes from a lichen community to a scoured bare rock surface and have been used to determine bankfull channel capacity on bedrock channels and their response to the combined disturbances of flow regulation and climate change. They can also be used to set flushing flows in bedrock channels. In sandstone gorges of the Nepean River, Australia, the crustose lichen, Lecidea terrena Nyl, was common at both gorge and cemetery (sandstone headstones) sites, enabling construction of growth curves for above and below dam areas. Growth curves were used to date lichen colonisation of sandstone surfaces in rivers. The oldest, highest lichen limit at all sites represented the pre‐flow regulation lichen community because its characteristics above and below Nepean Dam were similar and were trimmed to a level that produced consistent discharges across a range of catchment areas. They corresponded to return periods of less than 2 years on the annual maximum series and was developed during the flood‐dominated regime (FDR) of 1857–1900. Lichen limits form by the phycobiont dominating the mycobiont and hence degrading lichen thalli due to water inundation causing weak or dead thalli to be scrubbed from the rock surface. Trimming to the unregulated lichen limit represents a small flood of frequent occurrence appropriate for flushing bedrock channels. A lower lichen limit was only found below a diversion weir and was formed by frequent dam spills between 1950 and 1952 during an extraordinary wet period at the start of the FDR between 1949 and 1990. Lichens colonised exposed sandstone between the level of frequent flows from 1949 to 1952, and the high lichen limit. On the Avon River, an additional lower limit reflected a massive downward shift in flow duration following the start of interbasin diversions to Wollongong in 1962. 相似文献
5.
气候和土地利用变化对塔里木河干流区植被覆盖变化的影响 总被引：4，自引：0，他引：4
基于遥感和地理信息系统技术,利用1998—2008年SPOT-VEGETATION归一化植被指数（NDVI）数据对塔里木河干流区1998—2007年植被覆盖的时空变化进行了监测,并从气候变化和土地利用变化双重角度分析了植被覆盖变化的原因。研究表明,塔里木河干流区植被覆盖变化经历了两个阶段:1998—2001年植被覆盖严重退化时期;2002—2007年植被覆盖度由急剧上升到缓慢下降再到持续升高时期,NDVI明显高于20世纪末期水平。塔里木河干流区植被覆盖变化存在显著的空间差异,绿洲农业灌溉区和退耕还林还草生态恢复区的植被覆盖度显著提高,天然草地植被区的植被退化严重。塔里木河干流区植被覆盖变化是气候和土地利用变化共同作用的结果。温度对植被覆盖变化的影响表现为对植被生长年内韵律的控制和秋季植被生长期的延长,年降水量的波动式上升是导致塔里木河干流区植被覆盖变化两个阶段呈现差异的主导因素。 相似文献
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Global warming has led to significant vegetation changes in recent years. It is necessary to investigate the effects of climatic variations(temperature and precipitation) on vegetation changes for a better understanding of acclimation to climatic change. In this paper, we focused on the integration and application of multi-methods and spatial analysis techniques in GIS to study the spatio-temporal variation of vegetation dynamics and to explore the vegetation change mechanism. The correlations between EVI and climate factors at different time scales were calculated for each pixel including monthly, seasonal and annual scales respectively in Qinghai Lake Basin from the year of 2001 to 2012. The primary objectives of this study are to reveal when, where and why the vegetation change so as to support better understanding of terrestrial response to global change as well as the useful information and techniques for wise regional ecosystem management practices. The main conclusions are as follows:(1) Overall vegetation EVI in the region increased 6% during recent 12 years. The EVI value in growing seasons(i.e. spring and summer) exhibited very significant improving trend, accounted for 12.8% and 9.3% respectively. The spatial pattern of EVI showed obvious spatial heterogeneity which was consistent with hydrothermal condition. In general, the vegetation coverage improved in most parts of the area since nearly 78% pixel of the whole basin showed increasing trend, while degraded slightly in a small part of the area only.(2) The EVI change was positively correlated with average temperature and precipitation. Generally speaking, in Qinghai Lake Basin, precipitation was the dominant driving factor for vegetation growth; however, at different time scale its weight to vegetation has differences.(3) Based on geo-statistical analysis, the autumn precipitation has a strong correlation with the next spring EVI values in the whole region. This findings explore the autumn precipitation is an important indicator, and then, limits the plant growth of next spring. 相似文献
9.
Global warming has led to significant vegetation changes in recent years. It is necessary to investigate the effects of climatic variations（temperature and precipitation） on vegetation changes for a better understanding of acclimation to climatic change. In this paper, we focused on the integration and application of multi-methods and spatial analysis techniques in GIS to study the spatio-temporal variation of vegetation dynamics and to explore the vegetation change mechanism. The correlations between EVI and climate factors at different time scales were calculated for each pixel including monthly, seasonal and annual scales respectively in Qinghai Lake Basin from the year of 2001 to 2012. The primary objectives of this study are to reveal when, where and why the vegetation change so as to support better understanding of terrestrial response to global change as well as the useful information and techniques for wise regional ecosystem management practices. The main conclusions are as follows：（1） Overall vegetation EVI in the region increased 6% during recent 12 years. The EVI value in growing seasons（i.e. spring and summer） exhibited very significant improving trend, accounted for 12.8% and 9.3% respectively. The spatial pattern of EVI showed obvious spatial heterogeneity which was consistent with hydrothermal condition. In general, the vegetation coverage improved in most parts of the area since nearly 78% pixel of the whole basin showed increasing trend, while degraded slightly in a small part of the area only.（2） The EVI change was positively correlated with average temperature and precipitation. Generally speaking, in Qinghai Lake Basin, precipitation was the dominant driving factor for vegetation growth; however, at different time scale its weight to vegetation has differences.（3） Based on geo-statistical analysis, the autumn precipitation has a strong correlation with the next spring EVI values in the whole region. This findings explore the autumn precipitation is an important indicator 相似文献
10.
Yoon‐Seop Chang 《International journal of geographical information science》2013,27(4):371-399
Most of the current Internet Geographic Information System (GIS) applications cannot be shared and are not interoperable because of their heterogeneous environments. With the growth of Internet GIS, many difficulties have occurred in integrating GIS components because of their diversity. The main objective of this study is to suggest a new development model for dynamic and interoperable Internet GIS applications. The model is based mainly on the dynamic integration of Internet GIS components by applying Extensible Markup Language (XML), XML Web Service, Geography Markup Language (GML), and Scalable Vector Graphics (SVG), etc. The relevant technologies of Internet GIS were reviewed thoroughly, and then a new model was designed. During the design of the new model, typical examples of GIS Web Service components were suggested, together with practical structures for applications using these components. Six examples of components and four types of applications were suggested, and they were experimentally implemented for model validation and improvement. The suggested model and components will enable easier and more rapid development of Internet GIS applications through the dynamic integration of distributed GIS components. Users will be able to avoid redundancy and consequently reduce both cost and time during each GIS project. 相似文献
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对采集自南极乔治王岛和北极新奥尔松地区的32份地衣标本中共生藻rDNA ITS序列进行测定,发现均为Trebouxia jamesii;结合Genbank中来自不同地区地衣中该藻的序列信息,发现T. jamesii的基因型与地衣物种及采集地都没有明确的对应关系。广布于全球范围的T. jamesii作为地衣优势共生藻,存在多种基因型,并且可以被多种地衣共生菌选择;其中优势基因型A在采集自南极洲、欧洲、北美洲和北极地区的地衣中均有发现,而其它基因型则在一定程度上出现地区特有性。本研究为地衣中的藻交换提供了证据,并提出地衣体碎片是实现地衣共生藻长距离传播的载体。 相似文献
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虽然采用遥感图像提取的植被指数在空间上能较好的反映作物的状况,但其不能预测植被指数在空间上的变化范围,如果能从整体上了解不同市县在不同季节的平均植被指数值,就可以对该区域整体植被状态进行量化分析,也就可以从大范围内进行植被指数的预测分析.利用地理信息系统(GIS)和地统计学相结合的地理统计分析模块(ArcGIS Geostatistical Analyst),根据MODIS遥感数据提取的每季度不同市县平均NDVI植被指数,采用Kriging插值的方法分析了海南岛归一化植被指数(NDVI)季节性变化趋势,并 相似文献
14.
Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens
on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of
epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns,
mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore,
it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic
weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out
in Antarctica. 相似文献
15.
为了研究南极的植物与环境间的关系 ,探讨植物在南极环境监测中的作用 ,在无标样条件下 ,利用微束 X荧光分析法对南极菲尔德斯半岛的 6种藻类和地衣植物进行了元素分析。其中藻类植物有孔石莼 (Ulva pertusa)、海膜 (H alymenia sp.)和大型鞘丝藻 (Lyngbya major) ,地衣植物有筛石蕊 (Cladonia borealis)、喇叭石蕊 (C.fimbriata)和松萝 (Usnea sp.)。研究结果发现 ,不同的藻类植物对各种元素的吸收能力不同 ,在 XRF(X射线荧光 )谱中 ,孔石莼比海膜含有更多的元素 ,象 As、Br和 Rb,Cu和 Zn的含量也较高。在大型鞘丝藻中 ,K比 Ca少 ,Zn的含量较高。在 3种地衣植物中 ,其 XRF谱中的元素种类组成非常相似 ,只是 Mn、Fe、Cu和 Zn等元素的相对含量有些差异 相似文献
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Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns, mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore, it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out in Antarctica. 相似文献
18.
基于变化轨迹探测的植被景观格局动态分析——以塔里木河下游生态输水区域为例 总被引：2，自引：0，他引：2
在遥感与GIS技术支持下,以2006、2007、2009、2010年Landsat-5/TM影像与2008年的CBERS/CCD影像为主要数据源,获得5 a的植被/非植被类型图。在此基础上,提取并归纳5 a间的植被变化轨迹:恒定植被、恒定非植被、转变为植被、转变为非植被、非稳定变化。利用景观格局分析软件FRAGSTATS 3.3计算了变化轨迹景观格局的3种景观指标。结果表明,2006—2010年植被面积减小,主要因为生态输水量减小、输水间隔较大,导致草本植被、乔灌木幼苗死亡;恒定非植被的比重最大,表明非植被类型是研究区的基质,其次是转变为非植被的比重,说明5 a间植被的衰退程度要强于恢复程度;转变为植被与非稳定变化两种类型属于过渡性植被变化类型,受生态输水量、分布的制约严重;各种变化轨迹类型的形状规则较为稳定,其中以恒定非植被类型最稳定而非稳定变化类型最不稳定。 相似文献
19.
Eric A. Colhoun 《The Australian geographer》1992,23(1):11-23
Pollen analysis of 3.25 m of late glacial and Holocene sediments gives a mid‐altitude (600 m) record of vegetation development after the last or Margaret Glaciation. Alpine herbfield, coniferous heath and Nothofagus gunnli scrub developed on the moraines until 11,400 BP. Wet montane forest and heath then developed with Phyllocladus aspleniifolius, Nothofagus cunninghamii and Eucalyptus until c. 10,000 BP. After 10,000 BP a mosaic of N. cunninghamii rainforest, Myrtaceae and Proteaceae scrub and Sprengelia incarnata heath occurred. The development of the vegetation from alpine communities to temperate rainforest, which is near its limit at 600 m, occurred under the influence of improving climatic conditions with rapid upslope migration or local expansion of taxa during the late glacial. Temperatures were warm enough for the development of rainforest at 600 m by 10,000 BP, if not earlier. The development of a mosaic of rainforest, scrub and heath vegetation rather than extensive rainforest after 10,000 BP reflects the influence of poor soils, bad drainage and fires. Comparison with similar pollen diagrams from western Tasmania suggests that the development of pollen/vegetation associations was time transgressive with altitude during the late glacial when climatic influences and migration rates were important, and that the mosaic of vegetation communities became more complex during the Holocene because of adjustment to or control by local ecological factors. 相似文献
20.
自然植被对气候变化响应的研究:建模 总被引：6，自引：0，他引：6
预测性植被制图（PVM）是自然植被对气候变化响应建模的重要思想和方法，已为国外的许多生态学家、地理学家在开展全球变化的影响研究中所采用。本文在简述了PVM发展过程的基础上，对其方法进行了归纳，并探讨了PVM对气候-植被响应模型研究的作用。在文中作者特别强调地理信息系统（GIS）在自然植被对气候变化响应建模中的重要性，并对GIS支持下的构模方法和步骤进行了总结。 相似文献