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Quantitative paleoclimatic reconstruction is crucial for understanding the operation and evolution of the global climate system. For example, a quantitative paleoclimatic reconstruction for the Last Glacial Maximum (18±2 ka 14C, LGM) is fundamental to understanding the evolution of Earth's climate during the last glacial-interglacial cycle. Previous quantitative palaeoclimate reconstructions in China are generally based on statistical comparison of modern pollen assemblages and modern climate data. These methods are based on the premise that vegetation-climate interactions remain the same through time, and implicitly assume that the interactions are independent of changes in seasonality and atmospheric CO2 concentration. However, these assumptions may not always be valid, which may affect the reconstructions. Here, we present the results of a quantitative study of the LGM climate of China based on an improved inverse vegetation model which incorporates physiological processes combined with a new China Quaternary Pollen Database. The results indicate that during the LGM, mean annual temperature (ANNT), mean temperature of the coldest month (MTCO) and mean temperature of the warmest month in China were lower by ~5.6±0.8, ~11.0±1.6 and ~2.6±0.9°C, respectively, compared to today, and that the changes in ANNT were mainly due to the decrease of MTCO. The ANNT decrease in southern China was ~5.5±0.5°C. Mean annual precipitation was lower by ~46.3±17.8 mm compared to today and was especially low in northern China (~51.2±21.4 mm) due to the decrease in summer rainfall. Comparison of our results with recent outputs from paleoclimatic modelling reveals that while the latter are broadly consistent with our estimated changes in mean annual climatic parameters, there are substantial differences in the seasonal climatic parameters. Our results highlight the crucial importance of developing seasonal simulation on paleoclimatic models, as well as the need to improve the quality of paleoclimatic reconstructions based on proxy records from geological archives. [ABSTRACT FROM AUTHOR]

Highlights • A temporal-spatial vegetation variation since the LGM in China was mapped. • Relative to today, forest expanded northwards by 2–5° by warm early and mid-Holocene. • Inverse vegetation model was used to study the dominant factors for paleovegetation. • The dominant factors differ between Holocene and the last glacial periods. Abstract The need to reduce the uncertainty of predictions of vegetation change under global warming highlights the importance of understanding the vegetation patterns and possible mechanisms of vegetation response during past warming intervals. Here, we present quantitative regional vegetation reconstructions for China during the Last Glacial Maximum (LGM, 18 ± 2 14C kyr B.P.), early Holocene (EH, 8.5 ± 0.5 14C kyr B.P.), and mid-Holocene (MH, 6 ± 0.5 14C kyr B.P.), using the biomization method and based on 249 pollen records. In addition, we used an inverse vegetation modeling approach to investigate the effect of climate change and CO 2 concentration on the observed vegetation changes. The results demonstrate that during the LGM, steppe expanded southeastwards, reaching the present-day temperate deciduous forest (TEDE) zone; in contrast, the forest in eastern China underwent a substantial southward retreat and its percentage reached a minimum. The warm mixed forest (WAMF) and TEDE shifted southwards of ∼10° N relative to today, and tropical seasonal rain forest (TSFO) was almost absent. In addition, the forest-steppe boundary shifted southwards to near the middle and lower reaches of the Yangtze River. During the EH and MH, the TSFO, WAMF, and TEDE exhibited respective northward shifts of 2°, 4° and 5° relative to today. In MH, the percentage of forest sites increased and reached a maximum, and the forest-steppe boundary had shifted northwestwards to near the present-day 300 mm isohyet. Our palaeovegetation reconstructions and model sensitivity experiments suggest that temperature was the dominant factor controlling the vegetation distribution during the LGM, while precipitation became increasingly more important during the Holocene throughout China. We further show that precipitation was the primary factor controlling palaeovegetation distribution in northern China, while temperature became increasingly more important in southern China. Our findings are potentially important for understanding the evolution of vegetation in China in response to ongoing global warming. [ABSTRACT FROM AUTHOR]

Large-scale palaeovegetation reconstruction plays a critical role in improving our understanding of the response of vegetation to climate change and in reducing the uncertainty in predictions of vegetation change under global warming scenarios. Here, we present quantitative vegetation reconstructions for China since the Last Glacial Maximum (LGM), using 286 selected fossil pollen records analyzed using the biomization method. The results show that from 23 to 19 ka (1 ka = 1000 cal yr BP), steppe and desert expanded southeastwards, dominating northern China, whereas forest in eastern China shrank southwards to near the middle and lower reaches of the Yangtze River; the percentage of forested sites at this time was the lowest during the studied interval. Forest then developed gradually during 18–12 ka. During the early and middle Holocene, tropical seasonal forest, broad-leaved evergreen / warm mixed forest, and temperate deciduous forest shifted northwards by 2°, 4° and 5° in latitude, respectively, relative to today, and then declined in the late Holocene. In detail, forest flourished in the middle Holocene (9–4 ka) in semi-arid and semi-humid northern China, whereas it reached a maximum in the early and middle Holocene (11.5–6 ka) in humid southern China. Our results suggest that although forest throughout China exhibited the expected response to the evolution of the East Asian summer monsoon, precipitation exerted a more significant effect on vegetation change in northern China, whereas temperature and precipitation played a more important role in southern China. Our results are a potentially useful reference for assessing future vegetation dynamics under global warming scenarios. [ABSTRACT FROM AUTHOR]