Knowledge of the paleoclimatic record of the northeastern Tibetan Plateau (NETP) can potentially improve our understanding of the evolution of the Asian summer monsoon (ASM). However, the history of climate change and inferred spatial extent of the ASM on the NETP since the last deglaciation remain unclear. Here, we use several environmental proxies from the sediments of Hala Lake (beyond the modern limit of ASM), including chironomids, loss-on-ignition, grain size and element data, to explore the climatic history of the NETP and the northern boundary of the ASM since the last deglaciation. The results document a series of climatic events during the deglaciation, including Heinrich Event 1, the Bolling-Allerod interstadial and the Younger Dryas event. The records also reveal the timing of the megathermal and precipitation maximum, the lake-level maximum, and strongest chemical weathering, which occurred during similar to 10-7 ka. The inferred precipitation maximum during the early Holocene in the Hala Lake basin, which can be verified by the simulated precipitation change, is consistent with that in typical Indian summer monsoon (ISM) regions, suggesting that the ISM has penetrated into Hala Lake basin at that time. The monsoon-dominated climate in the Hala Lake basin during the early Holocene and the westerlies-dominated climate in the arid central Asia indicate that the maximum areal extent of the ASM on the NETP since the last deglaciation lay to the northwest of Hala Lake basin. In combination with other published records, the northernmost boundary of the ASM over China since the last deglaciation has been tentatively delineated, to shed some lights on this long-standing debate.

Aim We aim to use species attributes such as distributions and indicator values to reconstruct past biomes, environment, and temperatures from detailed plant-macrofossil data covering the late glacial to the early Holocene (ca. 14-9 ka). Location Krakenes, western Norway. Methods We applied attributes for present-day geographical distribution, optimal July and January temperatures, and Ellenberg indicator values for plants in the macrofossil data-set. We used assemblage weighted means (AWM) to reconstruct past biomes, changes in light (L), nitrogen (N), moisture (F), and soil reaction (R), and temperatures. We compared the temperature reconstructions with previous chironomid-inferred temperatures. Results After the start of the Holocene around 11.5 ka, the Arctic-montane biome, which was stable during the late-glacial period, shifted successively into the Boreo-arctic montane, Wide-boreal, Boreo-montane, Boreo-temperate, and Wide-temperate biomes by ca. 9.0 ka. Circumpolar and Eurasian floristic elements characteristic of the late-glacial decreased and the Eurosiberian element became prominent. Light demand (L), soil moisture (F), nitrogen (N), and soil reaction (R) show different, but complementary responses. Light-demanding plants decreased with time. Soil moisture was relatively stable until it increased during organic soil development during the early Holocene. Soil nitrogen increased during the early Holocene. Soil reaction (pH) decreased during the Allerod, but increased during the Younger Dryas. It decreased markedly after the start of the Holocene, reaching low but stable levels in the early Holocene. Mean July and January temperatures show similar patterns to the chironomid-inferred mean July temperature trends at Krakenes, but chironomids show larger fluctuations and interesting differences in timing. Conclusion Assigning attributes to macrofossil species is a useful new approach in palaeoecology. It can demonstrate changes in biomes, ecological conditions, and temperatures. The late-glacial to early-Holocene transition may form an analogue for changes observed in the modern arctic and in mountains, with melting glaciers, permafrost thaw, and shrub encroachment into tundra.