东亚中高纬Heinrich 1事件的表现特征:呼伦湖孢粉记录

Heinrich 1事件是发生于末次冰消期的极端气候突变事件之一,对全球大气环流和陆地生态格局产生了深刻影响.基于对东亚夏季风边缘区最北端呼伦湖 HL08 孔5. 75 m 以上沉积岩芯的 AMS 14C定年技术和 415~275 cm段140个样品的孢粉分析,重建了东亚中高纬地区呼伦湖21500~13000 cal. a B. P.高分辨率植被变化历史,在此基础上揭示了Heinrich 1事件期间呼伦湖区植被响应过程,明确了Heinrich 1事件在东亚中高纬地区的表现特征.结果显示:呼伦湖区Heinrich 1事件发生于16500~15400 cal. a B. P.,以剧烈降温和显著干旱化为表现特征;事件发生期间湖区周围山地发育亚高山草甸,森林植被稀疏;湖盆区域以藜科为主的荒漠草原显著扩张,区域植被盖度降低、生态环境明显恶化;同时,不同植被类型对Heinrich 1事件的响应存在明显差别,亚高山草甸和蒿属为主的典型草原较藜科为主的荒漠草原和桦属为主的落叶阔叶林响应更为快速、敏感.

The character and impact of the Heinrich event 1 in the middle-high latitude of East Asia: Pollen records from the Hulun Lake

The Heinrich event 1 was the most prominent cooling events in the North Atlantic region during the last deglaciation, and had a profound influence on global atmospheric circulation and terrestrial ecosystems;however, its behavior and consequence in eastern Asia remain unclear. In order to reveal the character and impact of the Heinrich event 1 in the middle-high latitude of East Asia. Hulun Lake was selected as a research target, which is on the northeastern edge of the current monsoon margin. In this paper, we presented a detailed record of the development of regional vegetation during 21500~13000 cal.a B. P. based a total of 16 AMS14C samples for the upper 5.75 m of core HL08 (49°06'52.4"N, 117°31'56.0"E) and 140 pollen samples at the depth of 4.15~2.75 m of core HL08 from Hulun Lake, and discussed the response process of regional vegetation around the Hulun Lake to the Heinrich event 1. The results show that:(1) During the period of 21500~13000 cal.a B. P., the vegetation changed from subalpine meadow and coniferous forest to deciduous forest in the surrounding mountains, and typical steppe occupied the area around the lake basin gradually, implying an overall increase in the density of the vegetation cover.(2) Based on principal component analysis of major pollen taxa, we suggested that the cold and dry event that occurred in the Hulun Lake region at 16500~15400 cal.a B. P. would be the regional manifestation of the Heinrich event 1 occurred in the North Atlantic region, and the climate was extreme cold and catastrophic drought in the middle-high latitude of East Asia.(3) During the Heinrich event 1, Cyperaceae and Gramineae denominated subalpine meadow and scattered sparse forest were present in the surrounding mountains, and Chenopodiaceae denominated desert steppe developed around the lake basin, suggesting that the regional ecological environment deteriorated and the vegetation cover was reduced around the Hulun Lake.(4) The change of regional vegetation around the Hulun Lake region can be divided into two stages:16500~16000 cal.a B. P., Artemisia dominated typical steppe decreased significantly and Cyperaceae and Gramineae denominated subalpine meadow expanded, the vegetation cover also reduced rapidly;16000~15400 cal.a B. P., Artemisia dominated typical steppe further reduced and Chenopodiaceae denominated desert steppe occupied the lake basin, the vegetation cover further reduced and the regional ecological environment deteriorated obviously.(5) The responses of different vegetation type to the Heinrich event 1 were significantly different around the Hulun Lake region:the response of subalpine meadow and Artemisia dominated typical steppe to the onset and end of the Heinrich event 1 was more sensitive than Chenopodiaceae denominated desert steppe and deciduous broad-leaved forest, which would be related to the difference of life form for different species;Therefore, the differential response of vegetation to climate change needs to be addressed in future global change research.