晚中新世云南先锋植物群及古气候的定量重建
星耀武
学位类型博士
导师周浙昆
2010-01
学位授予单位中国科学院研究生院
学位专业植物学
摘要通过对采自先锋盆地植物化石的研究,恢复了该植物群的基本面貌,并且利用3种方法定量恢复了先锋植物群的古气候,探讨了新近纪以来云南植被类型和古环境的变化。主要研究结论如下:1)通过初步鉴定该植物群含植物34种,分属9科,21属,另有29个未鉴定的形态种。34种植物中,包括2种裸子植物,其余全为双子叶植物。其中以壳斗科、樟科含种数量最多,占较大优势。因此,先锋植物群是一个以壳斗科、樟科植物为主的亚热带植物群。2)利用CT扫描技术对植物群中的松科三维球果化石进行了详细地研究发表了松属,铁杉属各一个新种,分别为Pinus prekesiya和Tsuga miodumosa。松属新种Pinus prekesiya的发现支持了分子生物学认为P. kesiya和P. yunnanensis有可能在早上新世分化的观点,而不是以往所认为的两个种是在始新世分化。并提出一个假说,随着青藏高原在新近纪的持续隆起及季风气候的逐渐加强,滇中高原及以北地区逐渐变得干旱,温度也更低,P. prekesiya开始向两支分化,一支逐渐适应更加干旱的环境,演化成为P. yunnanensis;另一支仍生活中较湿润的山地地区,分化成为P. kesiya。 铁杉属新种Tsuga miodumosa的最近亲缘种是Tsuga dumosa。该新种是云南铁杉属大化石的最早记录。T. miodumosa的发现支持了分子生物学认为T. dumosa可能在中新世时分化出来,并且认为T. dumosa的祖先类群在亚洲的观点。通过铁杉属化石记录的研究认为,铁杉属是由于青藏高原抬升后导致了气候的变凉和生境的多样化才逐渐演化而来。3)三种方法得到的年均温(CA:17.2-18.0°C;CLAMP3B-Revised:15.7±1.33°C;LMA:17.2±1.6°C)都稍高于植物群现代年均温,说明晚中新世时,先锋盆地年均温稍高于现代。利用CA和CLAMP重建的先锋植物群的年均降水分别是1206-1537.4mm和1297.0±184.7mm,两者均明显高于现代的年降水(1003.2mm)。说明在晚中新世时,当地气候要比现在更湿润。与所模拟的中新世平均降水比现代高的结论相吻合,且这种趋势在欧洲中部和中国多个中新世古气候恢复的研究中被证实。两种方法计算的湿润月和干旱月的降水都有明显差别,说明当时已经有了明显的季节变化,但是由于晚中新世时干季降水远大于现在,所以当时的季节变化没有现在明显。利用共存法的原理恢复了先锋植物群的古海拔,结果为1330-1500m,比现今海拔2200m低,说明自晚中新世以来先锋植物群至少抬升了700m。4)通过云南新近纪植物群化石记录和古气候资料的对比,探讨了云南新近纪以来的古环境变化。认为中新世时,云南植物群多是以壳斗科、樟科等为优势的常绿阔叶林的植被类型,气候普遍温暖且湿润,中新世到上新世气温和降水变化不大,可能与一些植物群恢复古气候区间较大有关。而晚上新世以后,气温有了一定的下降,降水有了很大减少,植物群中适应高寒环境的成分增多,尤其是高山栎化石的大量出现,说明了这个时期出现了较剧烈的环境变化,环境变得寒冷而干燥,但温度下降幅度小于高纬度植物群的古气候变化。这也说明晚上新世以后的全球变冷对低纬度植物群的影响较小。5)利用旱季降水占全年降水的百分比和雨季旱季降水差值占全年降水的百分比两个指标探讨了自中新世以来季风强度的变化。两个指标的计算结果都表明晚中新世时虽然有干湿季节的变化,但是没有现在明显,说明自新近纪以来,云南地区季风强度有了很大的增强,而且也证明这两个参数可以很好地反映季风强度的变化,可以为讨论季风的演化提供较好的参考。
资助项目The Xianfeng flora and its palaeoclimte were studied using three quantitative methods. The vegetation and climatic change in Yunnan were also discussed in this paper. The results are summarized as follows:1) 34 species belonging to 9 families, 21 genera were identified in Xianfeng flora. The dominant families are Fagaceae and Lauraceae. Most genera are tropic and subtropic distribution. Consequently, Xianfeng flora is a typical subtropic flora dominanted by Fagaceae and Lauraceae.2)Two new coniferous species were identified, Pinus prekesiya and Tsuga miodumosa. P. prekesiya sp. nov., which belongs to subsection Pinus of subgenus Pinus shows a combination of characters of P. kesiya and P. yunnanensis, but has a closer affinity with P. kesiya which distributes in the humid region of Yunnan and therefore suggests a more humid climate in central Yunnan during the late Miocene than today. The general cooling trend during the late Neogene and topographic change due to the dramatic Tibetan uplift might have cause a vicariance origin of P. kesiya and P. yunnanensis from the ancestral P. prekesiya. Tsuga miodumosa shows a closest affinity with T. dumosa and might represent the ancestral stock of T. dumosa. The discovery of the Tsuga cone confirmed the presence of Tsuga in the Miocene of southwestern China and represents the earliest Tsuga megafossil record in China. The new species provides fossil evidence to support molecular phylogeny study that T. dumosa might be differentiated in the Miocene. It also support the hypothesis that diversification of the genus occurred mainly during Miocene and Pliocene time as global climate cooled and new habitats formed in response to major orogenic events.3)The MATs results from three methods (CA: 17.2-18.0°C;CLAMP3B: 15.7±1.33°C;LMA: 17.2±1.6°C) are higher than present. This indicates that the climate at late Miocene is warmer than today. The MAPs from CA and CLAMP are 1206-1537.4mm and 1297.0±184.7mm respectively, which are higher than today (1003.2mm) obviously. This indicates that the climate is more humid in late Miocene. The differences between precipitation in humid season and dry season suggest the existence of seasonality,but not so strong as today. The palaeoelevation was reconstructed using CA method; the result indicates a lower elevation (1330-1500m) of Xianfeng in late Miocene compared to today.4) The palaeoenvirmental change was discussed based on the comparisons of fossil records and paleoclimate constructions. The results show that, at late Miocene, most floras represented ever-green forests dominanted by Fagaceae and Lauraceae etc. The climate of Yunnan in Miocene was warmer and more humid than today. At Pliocene age, the vegetation type in West Yunnan is still typical ever-green forest, while in the Sanying flora, the species adapt to cold environment like Quercus sect. Heterobalnus increased greatly.5) Two monsoon sensitivity indices were used to illustrate the change of sensitivity of monsoon climate. The results suggest lower seasonality and monsoon sensitivity, especially the winter monsoon sensitivity during late Miocene.
语种中文
文献类型学位论文
条目标识符http://ir.kib.ac.cn/handle/151853/16132
专题昆明植物所硕博研究生毕业学位论文
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星耀武. 晚中新世云南先锋植物群及古气候的定量重建[D]. 中国科学院研究生院,2010.
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