Fig 1.
Distribution of Pollen Sites in the Qinghai-Tibetan Plateau and Adjacent Areas, and Location Map of the Study Area.
(Zhang, Y. (2019). Integration dataset of Tibet Plateau boundary (TPBoundary_HF). National Tibetan Plateau/ Third Pole Environment Data Center. https://doi.org/10.11888/Geogra.tpdc.270099. https://cstr.cn/18406.11.Geogra.tpdc.270099.).
Table 1.
Data types and sources.
Fig 2.
Pollen experimental pretreatment process.
Fig 3.
Relationship between instrumental and simulated values of January and July temperatures in the Sanjiangyuan region (1923–2023).
Table 2.
Chronostratigraphic ages for the XDW2 profile.
Table 3.
Chronostratigraphic ages for the Zhongda profile.
Fig 4.
Age-Depth Relationship of the Xia Dawu Profile (left) and Zhongda Profile (right).
(In the formula, X denotes Age; Y denotes Depth; the columnar diagram represents stratigraphic characteristics of the profiles).
Fig 5.
Characteristics of the sporo-pollen assemblage in the Xia Dawu Profile (The blue section is magnified 3×).
Fig 6.
Characteristics of the sporopollen assemblage in the Zhongda Profile (Blue section magnified 3×).
Table 4.
(TOL) and (VIF) diagnostic metrics for January temperatures at 10 fossil pollen sampling sites.
Table 5.
(TOL) and (VIF) diagnostic metrics for July temperatures at 10 fossil pollen sampling sites.
Fig 7.
Correlation test of January (left) and July (right) temperatures across 10 fossil sporopollen sampling sites.
Table 6.
Construction of the DMFS-1 regression model.
Table 7.
Establishment of the DMFS-7 regression model.
Fig 8.
Reconstructed January (left) and July (right) Mean Temperatures from 10 fossil Pollen Sites (Unit:°C).
(a) Bande Lake sediment core BDH19A [30]; (b) Maqin profile [25]; (c) Kuhai drilling core [23]; (d) Koucha Lake drilling core [24]; (e) Donggi Cona profile [26]; (f) Gaqing profile [28]; (g) Canxiong Gasu profile [27]; (h) Xia Dawu Profile; (i) Zhongda Profile; (j) Ngoring Lake Profile [29]; (k) Sanjiangyuan region.
Fig 9.
Comparison of integrated Holocene January and July temperature reconstructions in the Sanjiangyuan region with other environmental records.
(a) The Zangser Kangri δ18O record indicates 30-year means [50]; (b) Summer solar radiation at 30°N [51]; (c) Northern Hemisphere (30°–90°N) temperature reconstruction [1]; (d) Tiancai Lake Chironomid-inferred mean July temperatures using a 5 sample running average (~250 year mean) [52]; (e) Chinese Holocene temperature reconstruction [53]; (f) Greenland ice core temperature reconstruction [54]; (g) Sanjiangyuan region Holocene January temperature; (h) Sanjiangyuan region Holocene July temperature; Color annotations: Blue shading: Markscold events (e.g., 8.2 ka BP and 4.2 ka BP anomalies); Orange shading: Indicates the Holocene Thermal Maximum (HTM) period (~6.0–4.0 ka BP in Sanjiangyuan). Environment Data Center. https://doi.org/10.11888/Geogra.tpdc.270099. https://cstr.cn/18406.11.Geogra.tpdc.270099).