排序方式： 共有5条查询结果，搜索用时 0 毫秒
1
1.
The satellite digital vegetation index data has been correlated with the forest growing stock by fitting linear regression models. The goodness of fit was tested. The analysis showed that the vegetation index which is the ratio of reflectance of vegetation in near infrared band to red wave band of electromagnetic spectrum is highly correlated to forest growing stock and the same can be used to predict the volume in remote forest areas for quick assessment purpose. Implications for future forest inventory are discussed. 相似文献
2.
海拉尔盆地基底晚古生代adakite的发现及其地质意义 总被引：5，自引：1，他引：4
海拉尔盆地的前中生代基底隶属中亚造山带东段的兴蒙造山带。 在盆地基底地层中发现了具有adakite成分特征的粗面安山岩、英安岩和闪长玢岩。 这些火成岩与晚古生代沉积地层交互或伴生, 共同构成晚中生代裂陷盆地的基底。 地球化学研究表明, 这些火成岩基本上属于高钾钙碱性和准铝质岩石系列, 具有高SiO2和Al2O3含量, 高Sr、Sr/Y和La/Yb值, 富集轻稀土(LREE), 亏损重稀土(HREE)、Y和高场强元素(HFSE),Eu表现弱的负异常或轻微的正异常, 相容元素Mg、Cr和Ni含量低, 这些特征与增厚下地壳部分熔融成因的adakite非常相似, 而明显不同于典型的由俯冲洋壳熔融形成的adakite。 样品的(87Sr/86Sr)i值基本一致,为0.7041, (143Nd/144Nd)i值为0.51243~0.51247, εNd (t)为正值(+3.7~+4.5), 显示其岩浆源区可能源于弱亏损地幔, 或亏损地幔受到地壳物质混染。 本文认为海拉尔地区晚古生代adakite型岩浆很可能是由当时新底侵的玄武质下地壳在角闪岩相向榴辉岩相过度或榴辉岩相条件下部分熔融形成。 这些adakite岩石的出现反映了兴蒙造山带晚古生代受到了古亚洲洋的俯冲消减引起的强烈的地幔玄武质岩浆底侵作用, 并由此导致地壳垂向上显著的增生加厚过程。 相似文献
3.
The KwaZulu-Natal Bight comprises the only sizeable shelf region on the eastern coast of South Africa, and is influenced by both the Agulhas Current on its seaward side and rivers and estuaries on its landward side. Established knowledge of the effect of the Agulhas Current includes the influence on nutrient concentrations in the bight of a semi-permanent upwelling cell at its northern border (St Lucia) and, to a much lesser extent, of a semi-permanent eddy feature at its southern extremity. Current modelling efforts, however, point to a very important role of land-derived nutrients, which supplement the productivity of food webs of the bight. This connectivity of the bight to its adjacent ecosystems has various implications. First, its productivity has traditionally been viewed via phytoplankton growth, whereas ecosystem modelling efforts point to a very high reliance on imported detritus (mainly land-derived) in order to sustain especially the rich benthic food web. The benthos in the bight dominates the food web, and is in marked contrast to the upwelling system of the west coast of South Africa (Atlantic Ocean) where water-column productivity dominates. Second, the importance of the connectivity of the Thukela Bank prawn-trawling ground to estuarine nursery areas, which has been modelled quantitatively, highlights the significance of this particular ecosystem connectivity for fisheries and also for the Thukela Bank food web. Heterogeneity across the bight is apparent for nutrient turnover rates (carbon, nitrogen, phosphorus), CNP content and stoichiometry, whereas nitrogen is a limiting nutrient across the entire bight. The food web near the Thukela River is richer in nutrient content and more active (higher turnover rates) compared to the northern and southern parts of the bight. This environmental heterogeneity was also apparent from the CNP content and stoichiometry of the various species and species groups in the bight. Requirements to take the hydrodynamic, biogeochemical and first ecosystem modelling efforts towards a meaningful predictive capability are discussed. The importance of adopting a system-level view of the bight and its connected systems for realistic exploration of global change scenarios is highlighted. 相似文献
4.
RC Babcock 《新西兰海洋与淡水研究杂志》2013,47(3):360-373
Abstract The Leigh Marine Laboratory (LML) has taken full advantage of its location on the shores of one of the world's first no-take marine reserves. The foresight of the founders of the laboratory has enabled the pursuit of ecological studies that have been amongst the first to demonstrate the effectiveness of reserves as a tool for conservation and restoration. The insights flowing from this work at Leigh are important, not only for targeted marine species, but also at the ecosystem level, and have proven to be highly relevant to broader resource management issues. Novel methodologies have been employed in the pursuit of these aims, helping to popularise their wider use. More recent work has focused on understanding the processes underlying the variability in response to marine conservation in marine reserves across the spectrum of coastal marine habitats in New Zealand. The LML has probably exceeded the expectations of its founders, who hoped the laboratory might generate information of interest in the fields of ‘resource management, food web dynamics and natural fluctuations distinct from man-induced changes’, and its contribution in the field of marine conservation has been significant both within New Zealand and internationally. This has been a 50-year journey that has gone from a focus on local effects of conservation to the broader context, from direct effects of protection to indirect effects, and from small-scale spatial conservation management to ecosystem-based management. 相似文献
5.
安徽女山麻粒岩包体：矿物学特征、下地壳地温曲线及其成因意义 总被引：10，自引：2，他引：10
女山玄武岩中麻粒岩包体的主要矿物组合为 Opx+Cpx+Pl,均呈条带状构造 ,具有细粒粒状变晶结构或不等粒结构。女山麻粒岩包体的斜方辉石及单斜辉石的化学成分都非常相似于华北太古代麻粒岩地体 ,而明显区别于汉诺坝麻粒岩包体。通过对世界上含石榴石麻粒岩的检验 ,表明 Wells(1977) :二辉石温度计与 Mc Carthy & Pati～no Douce(1998)的 Cpx+Pl+Qz压力计的温压计组合是计算麻粒岩平衡温压的可行方法 ,并得到了女山麻粒岩包体平衡温度分布于 80 9～ 899℃之间 ,主要集中于 85 0± 2 0 C,平衡压力为 0 .6 0～ 0 .95 GPa。由麻粒岩包体的平衡温压所建立起的女山地区下地壳地温曲线与 Xuet a1.(1998)建立的上地幔地温曲线上延部分非常吻合。根据地温线推得的“岩石学”Moho面深度为 31km土 ,与“地震”Moho面深度相一致 ,表明女山地区不具有明显的壳幔过渡带。女山地区缺乏强烈的底侵作用以及麻粒岩包体的特征矿物化学成分暗示了女山麻粒岩包体可能来源于华北克拉通结晶基底 相似文献
1