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11.
中更新世以来气候转型与陆地植被生态系统演变是近年来全球变化研究领域关注的热点问题。基于华北平原东部G3孔上部的孢粉分析结果、磁性地层年代,对中更新世以来华北平原植被演化及其气候响应过程进行研究。结果显示华北平原地区近1.6Ma以来植被演化可分为4个阶段:1.6~1.2Ma为密度较高的暖温带针阔叶混交林,1.2~0.7Ma为开阔的暖温带落叶阔叶林,0.7~0.3Ma为阔叶疏林草原,0.3Ma以来为暖温带落叶阔叶林。华北平原地区中更新世植被转型期对应O同位素36阶段,显示转型开始发生于1.2Ma,与全球中更新世转型期对应良好。其主要特征表现为林地减少,针叶林比例下降,藜科、蒿属、禾本科等草地面积显著增加。0.7Ma前后华北平原林地进一步退化,区域植被由原来的落叶阔叶林向疏林草原转变,0.3Ma后区域乔木比例可能有所回升。周期性气候变化对植被的影响在花粉谱中也有一定显示,1.2Ma之前主要表现为植被林地类型的交替发展,而1.2Ma则主要表现为草原与森林交替发展。 相似文献
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北京延庆盆地早更新世孢粉组合及其气候地层学意义 总被引：5，自引：0，他引：5
本文孢粉化石是通过延庆盆地杨户庄、阜高营及东龙湾地区地层剖面研究的。自上而上划分个孢粉组合带、植被演替和气候变化阶段。１．Ｑｕｅｒｃｕｓ－Ｒａｎｕｎｃｕｌａｃｅａｅ－Ｇｒａｍｉｎａｅ，针阔混交林－草原，气候温暖偏干。２．Ｐｉｎｕｓ－Ｐｏｌｅｍｏｎｉａｃｅａｅ，森林－草原，气候温凉干爽。３．Ｑｕｅｒｃｕｓ－Ｐｉｎｕｓ－Ｇｒａｍｉｎａｅ，针阔混交林－草原，气候温暖干燥。４．Ａｂｉｅｓ－Ｐｉｃｅａ－Ｐｏ 相似文献
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札达盆地晚上新世生长着以高山荒漠小灌木、草原、亚高山常绿针叶林和中低山常绿针叶林为主的植被。气候显示了从干旱寒冷至温暖湿润的垂向分异，总体偏于干、寒，属亚热带高山或亚高山类型。当时区内海拔已较高，南低北高的地势特征也已形成。古植被重建及现青藏高原的植被调查资料表明，当时盆地最低处的海拔可能不会超过2 500 m，其周围及北部可能存在海拔4 000 m的高地或更高的山峰。中、晚上新世迄今，该地区隆升的高度的可能不会超过1千米，幅度较喜马拉雅山中部地区小。 相似文献
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第三纪的板块运动驱动着澳大利亚的气候和植被进行演化。广布的湿润森林区是澳大利亚早第三纪的特征。一直到始新世,生物多样性都在不断地提高。毫无疑问,这是澳大利亚由高南纬区向北部中纬区运移的结果。从始新世到上新世,澳大利亚的气候总体上要比现在湿润,但降水量季节性变化的增强推动了中新世以后硬叶植物和旱生植物的发展。上新世晚期似乎与第四纪一样,都出现过周期性干旱。这种干旱与冰期条件有关,至少由南澳大利亚晚第四纪的记录可以认识到这一点,澳大利亚的这段历史与东亚的气候变迁是同步发生的。在东亚,印一澳板块的运动致使青藏高原抬升,从而引发了区内乃至全球气候的巨变。穿越赤道区的季风和信风的环流格局致使晚第三纪和第四纪中国与澳大利亚的气候系统的相关性更强。 相似文献
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西双版纳橄榄坝泥炭剖面的放射性碳测年和孢粉分析研究表明,该沼泽泥炭堆积始于约７２５０ａＢ．Ｐ．,当时橄榄坝盆地的植被是以千果榄仁和龙脑香科为代表的热带雨林植被,约５６９０ａＢ．Ｐ．在气候变凉干和人类活动的双重影响下,热带雨林逐渐从盆地内消失,并再也未能恢复起来 相似文献
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共和盆地末次冰消期以来的植被和环境演变 总被引：10，自引：1，他引：9
在青藏高原共和盆地中的内陆湖泊--达连海获取40.92 m长的湖泊岩芯(DLH钻孔),选用植物残体作为测年材料,利用AMS14C测年技术建立可靠的地层年代序列,对岩芯进行孢粉分析,重建该地末次冰消期以来的古植被和古环境。末次冰消期以来达连海周围山地在14.8～12.9Cal ka BP和9.4～3.9 Cal ka BP时段曾发育森林,气候较湿润,达连海附近盆地发育的荒漠草原盖度增加或演化为草原;在15.8～14.8 Cal ka BP、12.9～9.4 Cal ka BP 和3.9～1.4 Cal ka BP 时段该地气候比较干旱,依据干旱的程度周围山地森林退化或消失,盆地内发育盖度较低的荒漠草原或草原化荒漠。1.4 Cal ka BP以来湿度有所增加,发育草原植被类型。依据植被的演替历史推断该地气候的变化历程是15.8～14.8 Cal ka BP 干旱,14.8～12.9 Cal ka BP 湿润,12.9～9.4 Cal ka BP干旱,9.4～3.9 Cal ka BP湿润,3.9～1.4 Cal ka BP干旱,1.4～0 Cal ka BP湿润。达连海的孢粉记录与附近青海湖的孢粉结果对比,发现两地植被发育基本一致。末次冰消期Bølling-Allerød 时期,山地森林发育;新仙女木事件发生时森林萎缩;全新世中期两地针叶林发育达到鼎盛,之后逐渐减少至消失。早全新世达连海森林扩张的时间滞后于青海湖,主要与两地森林树种的不同和植被演替的时间差异有关。该区森林发育的全盛时期在中全新世,这与石笋记录到的亚洲季风强盛时期在早全新世不相一致,可能与植被复杂的响应机制有关。 相似文献
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笔者在西藏仲巴县隆格尔地区进行1∶5万区域地质调查过程中,在渐新统日贡拉组地层中上部采集了孢粉化石,为裸子植物花粉(Abietineaepollenites sp.、Pinuspollenites sp.、Tsugaepollenites sp.、Piceapollis sp.)、被子植物花粉(Artemesiaepollenites sp.、Betulaceoipollenites sp.、Rutaceoipollenites sp.、Betulaepollenites sp.、Graminipidites sp.)、蕨类植物孢子(Deltoidospora sp.、Lycopodiumsporites sp.、Toroisporis sp.)等组合,时代属于古近纪渐新世,可能跨及中新世。孢粉组合的发现对隆格尔地区日贡拉组地层的划分、对比及沉积时期的古气候、古地理和古植被的分析提供了依据,丰富了地层的古生物数据。在这一时期,古植被以松科和蒿属为主,反映了一次与构造运动密切相关的古环境变化事件,同时指示了古气候的轨迹及特征,揭示了构造的演化发展和沉积盆地响应过程与古气候的耦合关系。 相似文献
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19.
青藏高原东北部共和盆地末次冰消期以来古植被和环境演变(英文) 总被引：5，自引：0，他引：5
Paleoenvironmental history in the monsoonal margin in the northeast Tibetan Pla-teau provides important clue to the regional climate. Previous researches have been limited by either poor chronology or low resolution. Here we present a high-resolution pollen record from a 40.92-m-long sediment core (DLH) taken from Dalianhai, a terminal lake situated in the Gonghe Basin, the northeast Tibetan Plateau for reconstructing the vegetation and climate history since the last deglacial on the basis of a chronology controlled by 10 AMS 14C dates on plant remains preserved in the core sediments. The pollen assemblages in DLH core can be partitioned into 6 pollen zones and each zone is mainly characterized by the growth and decline of tree or herb pollen percentage. During the periods of 14.8-12.9 ka and 9.4-3.9 ka, the subalpine arboreal and local herbaceous pollen increased, indicating the subalpine forest developed in the surrounding mountains and a desert steppe or typical steppe developed in Gonghe Basin under a relatively moister climate. During the periods of 15.8-14.8 ka, 12.9-9.4 ka and 3.9-1.4 ka, the forest shrank or disappeared according to different degrees of aridity, and the desert steppe degraded to a more arid steppe desert in the basin, indicating a dry climate. After 1.4 ka, vegetation type around Dalianhai was mainly dominated by steppe suggested by increased Artemisia. Our results suggested the climate history in this region was dry from 15.8-14.8 ka, humid from 14.8-12.9 ka and dry from 12.9-9.4 ka, after which the climate was humid during 9.4-3.9 ka, followed by dry conditions during 3.9-1.4 ka and humid conditions in the last 1.4 ka. The change of pollen percentage and the evolution of palaeovegetation in Dalianhai since the last deglacial were similar to those recorded in Qinghai Lake. The forest expanded in the mountains around Dalianhai during the B?l-ling-Aller?d period, shrank during the Younger Dryas and the early Holocene, then it devel-oped and reached its maximum in the mid-Holocene. During the late Holocene, the vegetation began to shrink till disappearance. However, the timing of forest expansion in the Holocene lagged behind that of Qinghai Lake, and this spatial heterogeneity was probably caused by the different forest species between these two places. The maximum of forest development in the mid-Holocene was inconsistent with the period of stronger summer monsoon in the early Holocene indicated by stalagmite records, the reason might be related to the complexity of vegetation response to a large-scale climatic change. 相似文献
20.
Palynological evidence for vegetational and climatic changes from the HQ deep drilling core in Yunnan Province, China 总被引：6，自引：0，他引：6
The high-resolution pollen study of a 737.72-m-long lake sediment core in the Heqing Basin of Yunnan Province shows that the vegetation and climate of mountains around the Heqing Basin went through six obvious changes since 2.780 Ma B.P. Namely, Pinus forest occupied most mountains around the studied area and the structure of vertical vegetational belt was simple between 2.780 and 2.729 Ma B.P., reflecting a relatively warm and dry climate. During 2.729―2.608 Ma B.P., the areas of cold-temperate conifer forest (CTCF) and Tsuga forest increased and the structure of vertical vegetational belt became clear. According to percentages of tropical and subtropical elements growing in low-altitude regions rifely increased, we speculate that the increase of CTCF and Tsuga forest areas mainly resulted from strong uplift of mountains which provided upward expanding space and growing condition for these plants. Thus, the climate of the low-altitude regions around the basin was relatively warm and humid. Between 2.608 and 1.553 Ma B.P., Pinus forest occupied most mountains around the studied area and forest line of CTCF rose, which reflects a moderately warm-dry climate on the whole. During 1.553―0.876 Ma B.P., the structure of vertical vegetational belt in mountains around the studied area became complicated and the amplitude of vegetational belts shifting up and down enlarged, which implies that the amplitude of climatic change increased, the climatic associational feature was more complex and the climate was moderately cold at a majority of the stage. During 0.876―0.252 Ma B.P., there were all vertical vegetational belts existing at present in mountains around the studied area. The elements of each belt were more abundant and complex than earlier. At different periods in the stage vertical vegetational belts occurred as expanding or shrinking, and alternated each other. The amplitude of vegetational belts shifting up and down was the maximum in the whole section. This change suggests that the amplitude of climatic change was evidently larger than earlier, but the frequency reduced and the climatic associational feature was more complex. From 0.252 Ma B.P. to the present, the most time was characteristic of the expanding of Pinus forest and semi-humid evergreen broad-leaved forest (SEBF) in mountains around the studied area, while expanding time of other vegetational belts was very short, which reflects a smaller amplitude of cold and warm fluctuation. On the basis of the six obvious cycles of vegetational and climatic changes, there were still many times of secondary vegetational successions and climatic oscillations. Based on the above analysis, the forcing mechanism of vegeta-tional succession and climatic change in the Heqing Basin is further discussed. It is primarily consid-ered that main influential factors were exterior factors such as orbital parameters, etc., but the uplift of the Qinghai-Tibet Plateau played a very important function for environmental changes in the Heqing Basin at two times obvious increase of vertical vegetational belts and three climatic transitions. 相似文献