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Palaeoenvironmental Changes during the Last 20,000 Years in the Humid Tropics : A Comparative Study by Means of Database and Palaeoenvironmental Map Compilation

湿润热带地区近2万年的古环境变迁:基于数据库和古环境图编制的比较研究

基本信息

批准号：
05452343
负责人：
KADOMURA Hiroshi
金额：
$ 1.73万
依托单位：
Tokyo Metropolitan University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

State of arts and future problems of palaeoenvironments research in the world humid tropics being elucidated by this project can be summarized as follows :1) The sites, where high-resolution pollen spectra with radiocarbon age controls from the LGM,are only 2-3 for every three humid tropical areas, i.e. Africa, Amazon and Southeast Asia-Australia.2) Even during the LGM extreme arid period, in Southeast Asia forests persisted on windward slopes exposed to the monsoons, and in the Zaire basin as gallery forests with montane taxa over the low plateaux. No valid data are available from the Amazon for this question.3) Pollen spectra have suggested that form mid-Holocene onward the climates of tropical South America and tropical Africa showed completely opposite tendency. However, no concrete explanations are so far available.4) Pollen spectra have shown that both in the Amazon and the Guineo-Congolian rainforests, forest began to reestablished from 14-13 ka, but full forest development achieved at ca. 9.5 ka for both regions. This cannot be explained by delayd response of vegetation, and requires reassessment of climate conditions.5) The most spectacular hydrogeomorphic events occurrecd during 13-10 ka in response to the return of tropical convective storms. In the Amazon, in addition, meltwater flux from the Andean Highlands must have playd important role in generating catastrophic floodings and the Amazon cone.6) Anthropogenic forest degradation and induced erosion and sedimentation date back to 9-7 ka in Southeast Asia, and ca. 3 ka in Africa. The data for this question are lacking for Amazon basin.7) More data with high time-resolution and the elimination of the effects of crustal movements on environmental changes are crucial to better comparative studies.

本项目所揭示的世界湿热带地区古环境研究的现状和未来问题可概括如下：1）在末次盛冰期，每三个湿热带地区（即非洲、亚马逊和东南亚-澳大利亚）中，只有2-3个地点有高分辨率的花粉光谱和放射性碳年代控制。2）即使在末次盛冰期极端干旱时期，东南亚的森林仍然存在于暴露于季风的迎风坡上，扎伊尔盆地的森林则是低高原上的画廊森林和山地分类群。3）花粉光谱表明，自中全新世以来，热带南美洲和热带非洲的气候变化趋势完全相反。4）花粉光谱研究表明，亚马逊雨林和刚果-圭亚那热带雨林的森林重建开始于14-13 ka，但森林完全发育的时间约为2000 ~ 3000万年。9.5这两个地区。这不能用植被的延迟响应来解释，需要重新评估气候条件。5）最壮观的水文地貌事件发生在13-10 ka期间，是对热带对流风暴回归的响应。此外，在亚马逊地区，来自安第斯高原的融水通量在产生灾难性的森林退化和亚马逊锥形中也起着重要作用。6）东南亚地区的人为森林退化和引起的侵蚀和沉积可以追溯到9-7 ka，约1000万年前。3、在非洲。7）更多的时间分辨率高的数据和消除地壳运动对环境变化的影响对于更好地进行比较研究至关重要。