Preprints
https://doi.org/10.5194/egusphere-2022-366
https://doi.org/10.5194/egusphere-2022-366
 
13 Jun 2022
13 Jun 2022
Status: this preprint is open for discussion and under review for Climate of the Past (CP).

An arid early Holocene revealed by palynological evidence for the north-east Tibetan Plateau

Nannan Wang1,2, Lina Liu1,2, Xiaohuan Hou1, Yanrong Zhang1, Haicheng Wei3, and Xianyong Cao1 Nannan Wang et al.
  • 1Alpine Paleoecology and Human Adaptation Group (ALPHA), State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
  • 2University of the Chinese Academy of Sciences, Beijing 100049, China
  • 3Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China

Abstract. Situated in the triangle of the East Asian monsoon, the Indian monsoon, and the westerlies, the Holocene patterns of climate and vegetation changes on the north-east Tibetan Plateau are still unclear or even contradictory. By investigating the distribution of modern pollen taxa on the east Tibetan Plateau, we infer the past vegetation and climate since the last 14.2 ka BP (thousand years before present) from a fossil pollen record extracted from Gahai Lake (102.3133° E, 34.2398° N; 3444 m a.s.l.) together with multiple proxies (grain-size, contents of total organic carbon and total nitrogen) on the north-east Tibetan Plateau. Results indicate that the Gahai Basin was covered by arid alpine steppe or even desert between 14.2 and 7.4 ka BP with a mild and dry climate, and high percentages of arboreous pollen are thought to be long-distance wind transported grains. Montane forest (dominated by Abies, Picea, and Pinus) migrated into the Gahai Basin between 7.4 and 3.8 ka BP driven by wet and warm climatic conditions (the climate optimum within the Holocene) but reverted to alpine steppe between 3.8 and 2.3 ka BP, indicating a drying climate trend. After 2.3 ka BP, vegetation shifted to alpine meadow represented by increasing abundances of Cyperaceae, which may reflect a cooling climate. The strange pollen spectra with high abundances of Cyperaceae and total pollen concentrations after ca. 0.24 ka BP (1710 CE) could be an indication of disturbance by human activities to some extent, but needs more direct evidence to be confirmed. Our study confirms the occurrence of a climate optimum in the mid-Holocene on the north-east Tibetan Plateau, which is consistent with climate records from the fringe areas of the East Asian summer monsoon, and provides new insight into the evolution of the Asian monsoon system.

Nannan Wang et al.

Status: open (until 08 Aug 2022)

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Nannan Wang et al.

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Short summary
We reconstructed the vegetation and climate change since the last 14.2 ka BP from a fossil pollen record together with multiple proxies (grain-size, contents of total organic carbon and total nitrogen) on the north-east Tibetan Plateau. The results reveal that an arid climate occurs across in the early Holocene and the vegetation could be disturbed by human activities to some extent after ca. 0.24 ka BP (1710 CE).