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The Earth has undergone a significant climate switch from greenhouse to icehouse during the Plio-Pleistocene transition (PPT) around 2.7-2.4 million years ago (Ma), marked by the intensification of the Northern Hemisphere glaciation (NHG) ~2.7 Ma. Evidence based on oceanic CO2 [(CO2)aq], supposed to be in close equilibrium with the atmospheric CO2 [(CO2)atm], suggests that the CO2 decline might drive such climate cooling. However, the rarity of direct evidence from [CO2]atm during the interval prevents determination of the atmospheric CO2 level and further assessment on the impact of its fluctuation. Here, we reconstruct the [CO2]atm level during 2.77-2.52 Ma based on a new developed proxy of stomatal index on Typha orientalis leaves from Shanxi, North China, and depict the first [CO2]atm curve over the past 5 Ma by using stomata-based [CO2]atm data. Comparisons of the terrestrial-based [CO2]atm and the existed marine-based [CO2]aq curves show a similar general trend but with different intensity of fluctuations. Our data reveal that the high peak of [CO2]atm occurred at 2.77-2.52 Ma with a lower [CO2]aq background. The subsequent sharp fall in [CO2]atm level might be responsible for the intensification of the NHG based on their general temporal synchronism. These findings shed a significant light for our understanding toward the [CO2]atm changes and its ecological impact since 5 Ma., (© 2014 John Wiley & Sons Ltd.)

Previous palaeoenvironmental reconstructions have implied that East Asia was dominated by a zonal climate pattern during the Eocene, with an almost latitudinal arid/semiarid band at ~ 30° N. However, this long-standing model has recently been challenged by growing body of multidisciplinary evidence. Some studies indicated that central China was characterized by climatic fluctuations between humid and drier conditions during the Early Eocene, akin to the present East Asian monsoon (EAM) regime. Using palynological assemblages in the Tantou Basin, central China, we quantitatively reconstructed climate changes from the Late Palaeocene to Early Eocene to better understand climate change in central China. Palynological assemblages revealed that the coniferous and broad-leaved mixed forest in this area received no less than 800 mm of annual precipitation and experienced a climate change from warm and wet to relatively cool and dry. According to palaeoclimate curves, a sudden climate change occurred in the Early Eocene, with the mean annual temperature and precipitation decreasing by 5.1 °C and 214.8 mm, respectively, and the climate became very similar to the present climate, which is controlled by the monsoon. Therefore, this significant climate change during the Early Eocene may signal the emergence of the EAM in East Asia. [ABSTRACT FROM AUTHOR]

The Hengduan Mountains, with a distinct altitudinal differentiation and strong vertical vegetation zonation, occupy an important position in southwestern China as a global hotspot of biodiversity. Pollen analysis of lake sediments sampled along an altitudinal gradient in this region helps us to understand how this vegetation zonation arose and how it has responded to climate change and human impacts through time. Here we present a ~30-ka pollen record and interpret it in terms of vegetational and climatic change from a 310 cm-long core from Shudu Lake, located in the Hengduan Mountains region. Our results suggest that from 30 to 22 cal. ka BP, the vegetation was dominated by steppe/grassland (comprising mainly Artemisia, Poaceae and Polygonaceae) and broad-leaved forest (primarily Quercus, Betula and Castanopsis) in the lake catchment, reflecting a relatively warm, wet climate early in this phase and slightly warmer, drier conditions late in the phase. The period between 22 and 13.9 cal. ka BP was marked by a large expansion of needle- and broad-leaved mixed forest (Pinus, Abies and Quercus) and a decline in the extent of steppe/grassland, indicating warming, drying climatic conditions followed by a cold, wet period. Between 13.9 and 3 cal. ka BP, steppe/grassland expanded and the area covered by needle- and broad-leaved mixed forest reduced, implying a fluctuating climate dominated by warm and humid conditions. After 3 cal. ka BP, the vegetation was characterized by an increase in needle-leaved forest and reduction in steppe/grassland, suggesting warming and drying climate. A synthesis of palynological investigations from this and other sites suggests that the vegetation succession patterns seen along an altitudinal gradient in northwestern Yunnan since the Late Pleistocene are comparable, but that each site has its own characteristics probably due to the influences of altitude, topography, microclimate and human impact. [ABSTRACT FROM AUTHOR]

The early Cenozoic was characterized by a very warm climate especially during the Early Eocene. To understand climatic changes in eastern Asia, we reconstructed the Early Eocene vegetation and climate based on palynological data of a borehole from Wutu coal mine, East China and evaluated the climatic differences between eastern Asia and Central Europe. The Wutu palynological assemblages indicated a warm temperate vegetation succession comprising mixed needle- and broad-leaved forests. Three periods of vegetation succession over time were recognized. The changes of palynomorph relative abundance indicated that period 1 was warm and humid, period 2 was relatively warmer and wetter, and period 3 was cooler and drier again. The climatic parameters estimated by the coexistence approach (CA) suggested that the Early Eocene climate in Wutu was warmer and wetter. Mean annual temperature (MAT) was approximately 16°C and mean annual precipitation (MAP) was 800–1400 mm. Comparison of the Early Eocene climatic parameters of Wutu with those of 39 other fossil floras of different age in East China, reveals that 1) the climate became gradually cooler during the last 65 million years, with MAT dropping by 9.3°C. This cooling trend coincided with the ocean temperature changes but with weaker amplitude; 2) the Early Eocene climate was cooler in East China than in Central Europe; 3) the cooling trend in East China (MAT dropped by 6.9°C) was gentler than in Central Europe (MAT dropped by 13°C) during the last 45 million years. [ABSTRACT FROM AUTHOR]

The ages of a fruticose lichen of Usnea aurantiacoatra (Jacq.) Bory, from Fildes Peninsula, King George Island, Southwest Antarctic, were determined by radiocarbon (14C), and it is 1993–1996 at bottom and 2006–2007 at top of the lichen branch. The growth rates of U. aurantiacoatra calculated are 4.3 to 5.5 mm year−1 based on its length and ages. The comparisons show that the growth rates of U. aurantiacoatra are higher than those of U. antarctica (0.4 to 1.1 mm year−1). The growth rates of fruticose lichens are always higher, usually >2 mm year−1, than those of crustose ones, usually <1 mm year−1, in polar areas. A warming trend on Fildes Peninsula is recorded in the period from 1969 to 2010 obviously: the mean annual temperature rose from −2.75 to −1.9°C and the average temperature of summer months from 0.95 to 1.4°C, as well as the average temperature of winter months from −6.75 to −5.5°C. The alteration of lichen growth rates in polar areas may respond to the climatic and environmental changes, and the lichens may act as bio-monitor of natural condition. [ABSTRACT FROM AUTHOR]

Abstract The Holocene (11,500 cal a B.P. to the present) is marked by the beginning of the Neolithic Age and the origin of agriculture. Holocene climatic changes have certainly influenced vegetation successions and human living conditions. However, few studies have attempted to link the palaeo-ecological data with archaeological evidence to understand Holocene human-environmental interactions. Beijing, an early human settlement and the ancient and modern capital of China, is a hotspot for studying human activities and the development of civilization in Eastern Asia. The extensive literature on Holocene vegetation and climatic changes and the uninterrupted archaeological records from this region provide an excellent opportunity to explore how the climatic changes influenced the successions of vegetation and human living conditions since 12,000 cal a B.P. Here, we use Beijing as a case study and quantitatively reconstruct the Holocene climatic changes and the dynamic landscapes and human living conditions on the Beijing Plain based on compiled pollen data and archaeological literature. The results show that the mean annual temperature curve for Beijing during the early Holocene was similar to that of 90–30°N and has been the opposite since the middle to late Holocene. The mean annual precipitation curve is consistent with those from other monsoon regions in the Northern Hemisphere. The rising mean maximum monthly precipitation since 3330 cal a B.P. indicates the presence of more frequent rainstorms in summer, which suggests that the Beijing city government should prepare for more frequent heavy rainfalls and related geological disasters. In addition, the records from archaeological sites in Beijing show that human settlements first occurred in montane regions during the early Holocene before spreading into the plains during the middle Holocene. The warmer and wetter climate being suitable for farming probably drove this human migration. This study is an example of how to use past climatic data to understand current weather and the potential changes to human living environments that may occur under the current global warming trend. Graphical abstract Unlabelled Image Highlights • To quantitatively determine the Holocene MAT and MAP curves of the Beijing Plain at a local scale. • To determine the Holocene precipitation pattern in the East Asian Monsoon region at a regional scale. • To explore changes in the monsoonal precipitation and potential driving forces at a global scale. • To reveal ancient human feedback to the Holocene climate change in the Beijing Plain. • To alert the Beijing city government to address increasing summer precipitation and related geological disasters. [ABSTRACT FROM AUTHOR]

Multi-proxy study of a 240 cm deep Lashoda Tal (lake) sediment profile, located adjacent to an archaeological mound in Central Ganga Plain, highlights the climate induced changes in the vegetation, ecology and culture since ∼25500 cal BP. Between ∼25500 and 22200 cal BP, the region shows grassland, incipient drainage and small ponds formed seasonally with moisture loving terrestrial thecamoeba suggesting supply of moisture in short spells under the winter monsoon regime. The sediment became sandy and invaded by trees during ∼22200 to 14300 cal BP indicating an increase in lake levels with more aquatic pollen and algal forms portraying the strengthened monsoon and high energy fluvial system. This observation is further supported by low percentage of thecamoeba. Subsequently, the climate became increasingly supportive showing low seasonality and formation of meandering channels, which favoured aquatic weeds and meadew-cutoffs with marshy areas and dense vegetation in the vicinity during ∼14300 to 7100 cal BP. High arboreal and non-arboreals pollen and thecamoebian diversity with, change in nature of sediment (increasing clay content) suggest the expansion of Lashoda lake ecosystem ∼7100 cal BP. Since the last 2 millennium and until ∼1550 AD the studied site was under immense human pressure of Kushana, Gupta and Mughal cultures, which is evident by the artifacts recovered from the mound situated near the study site. The palynological study revealed reduced monsoon, fragmentation or desiccation of lake ecosystem ∼1550 AD, which is attributed to geomorphological changes caused by the ameliorating climate. The records of Cerealia pollen ∼1300 cal BP indicate expansion of agricultural activities that might have affected the lake ecosystem. [ABSTRACT FROM AUTHOR]

The Younger Dryas (YD) is one of the most abrupt climatic events in Earth's recent history. The warming at the end of the YD, in particular, is considered to be comparable to the global warming seen in the 21 st century. However, the YD termination has received little attention, particularly in the Hengduan Mountains of Southwestern China, a low latitude temperate biodiversity hotspot. Here we present evidence for a rapid response in the diversity and composition of vegetation to the warming at the YD termination, based on a continuous, well-dated pollen sequence and loss-on-ignition data (12.9–9.2 cal. ka BP) from Haligu wetland in the Hengduan Mountains. Our data indicate that variations in plant diversity were correlated with relative humidity during this period, and suggest a distinct shift from Pinus-Abies-Picea forest to Pinus -dominated forest at the YD-Holocene transition, accompanied by an increase in coverage of generally temperate taxa such as Salix and Betula . This finding provides insights that may be of relevance to biodiversity conservation under future warming scenarios in similar mountain ecosystems worldwide. [ABSTRACT FROM AUTHOR]

We apply the Coexistence Approach (CoA) to reconstruct mean annual precipitation (MAP), mean annual temperature (MAT), mean temperature of the warmest month (MTWA) and mean temperature of the coldest month (MTCO) at 44 pollen sites on the Qinghai–Tibetan Plateau. The modern climate ranges of the taxa are obtained (1) from county-level presence/absence data and (2) from data on the optimum and range of each taxon from Lu et al. (2011). The CoA based on the optimum and range data yields better predictions of observed climate parameters at the pollen sites than that based on the county-level data. The presence of arboreal pollen, most of which is derived from outside the region, distorts the reconstructions. More reliable reconstructions are obtained using only the non-arboreal component of the pollen assemblages. The root mean-squared error (RMSE) of the MAP reconstructions are smaller than the RMSE of MAT, MTWA and MTCO, suggesting that precipitation gradients are the most important control of vegetation distribution on the Qinghai–Tibetan Plateau. Our results show that CoA could be used to reconstruct past climates in this region, although in areas characterized by open vegetation the most reliable estimates will be obtained by excluding possible arboreal contaminants. [ABSTRACT FROM AUTHOR]

Pollen, phytoliths and δ 13 C signatures of soil organic matter from two fluvial sedimentary sequences of the Darjeeling foothill region, eastern Himalayas are used to portray palaeoclimatic oscillations and their impact on regional plant communities over the last ∼50 ka. Quantitative palaeoclimate estimation using coexistence approach on pollen data and other proxies indicate significant oscillations in precipitation during the late part of MIS 3 (46.4–25.9 ka), early and middle part of MIS 2 (25.9–15.6 ka), and 5.4 to 3.5 ka. Middle to late MIS 3 (ca 46.4–31 ka.) was characterized by a comparatively low monsoonal activity and slightly higher temperature than that during ca 31 ka onwards. Simultaneous expansion of deciduous trees and chloridoid grasses also imply a drier and warmer phase. Between 31 and 22.3 ka (late MIS 3 to mid-MIS 2), higher precipitation and a slightly cooler temperature led to an increase in evergreen elements over deciduous taxa and wet-loving panicoid grasses over dry-loving chloridoid grasses than earlier. After ca 22.3 ka, shrinking of forest cover, expansion of C4 chloridoid grasses, Asteraceae and Cheno-ams in the vegetation with lowering of temperature and precipitation characterized the onset of the LGM which continued till 18.3 ka. End of the LGM is manifested by a restoration in the forest cover and in the temperature and precipitation regime. Later, during 5.4 to 4.3 ka, a strong monsoonal activity supported a dense moist evergreen forest cover that subsequently declined during 4.3 to 3.5 ka. A further increase in deciduous elements and non-arboreals might be a consequence of reduced precipitation and higher temperature during this phase. A comparison between monsoonal rainfall, MAT and palaeoatmospheric CO 2 with floral dynamics since last ∼50 ka indicates that these fluctuations in plant succession were mainly driven by monsoonal variations. [ABSTRACT FROM AUTHOR]

The global climate changed significantly during the Pliocene–Pleistocene transition, and a worldwide aridification occurred. In order to investigate the influence of the aridification during the Pliocene–Pleistocene transition in the East Asian interior, diatom assemblages from the Upper Zhangcun Formation, north China, deposited during 2.7–2.5 Ma BP were analyzed, and the lake salinity was reconstructed using diatom–environment transfer functions. A total of 74 diatom taxa were found in the sediments, belonging to 21 families and 32 genera. Four zones were established from the bottom to the top, based on the changes in the diatom assemblages over the 15.7 m sediment sequence. In Zone 1, Cyclotella iris dominated in assemblage while Caloneis westii and Staurosira construens were less presented among representative species. In Zone 2, C. iris dominated, which indicates carbonate-rich water. But in Zone 3, benthic pennate taxa such as C. westii and Anomoeoneis sphaerophora became more abundant, indicating a significant increase in water salinity, from carbonate type to sulfate type, caused by climatic change. In Zone 4, C. iris became dominant again, with abundant Gomphonema intricatum and rare Pinnularia rathsbergiana and Martyana martyi species. The salinity inferred by conductivity reconstruction increased from 1.9 ppt in Zone 2 to 4.1 ppt in Zone 3. The significant changes of anion ratio (Alk / (Cl − + SO 4 2− )) indicate an abrupt change from carbonate-rich to a sulfatic type water. The increase of salinity reflects changes in the precipitation –evaporation balance. The change from carbonate to sulfatic water inferred from the diatom assemblages could indicate a significant aridification around ca. 2.6 Ma BP on the eastern edge of the Loess Plateau. This is the most easterly record of aridification across the Eastern Asian interior and may be related with the global cooling and the development of the Northern Hemisphere glaciation. [ABSTRACT FROM AUTHOR]

Abstract: To understand the vegetation succession and climatic changes at the southeastern margin of the Tibetan Plateau in the Neogene, we reconstructed the Middle Miocene vegetation and climate based on palynological data from four localities, which are at different latitudes along the Ailao Mountains in Yunnan, southwest China. The palynological assemblages suggest that the vegetation there was composed of mixed evergreen and deciduous broad-leaved forests growing under subtropical conditions. Based on the palynological data, the palaeoclimatic parameters from the four localities are established. The new parameters were compared with those of the Late Miocene, of the Late Pliocene, and of today. The comparison revealed that the temperatures were obviously lower in the Middle Miocene than they are today. This suggested that the Ailao Mountains were not high enough to block the Asian Winter Monsoon in the Middle Miocene. The Middle Miocene vegetation at the southeastern edge of the Tibetan Plateau was also compared to that of Central Tibet. It would appear that the palaeoclimate at the southeastern edge of the Tibetan Plateau was warmer and wetter than in Central Tibet. In contrast to the Neogene cooling in Central Europe, the climate at the southeastern edge of the Tibetan Plateau has gradually warmed since the Middle Miocene. This phenomenon was most likely caused by the uplift of the Tibetan Plateau, which has succeeded in blocking the Asian Winter Monsoon since the Middle Miocene. [Copyright &y& Elsevier]

Abstract: Quantifying the elevation history of the 2000km-wide Tibetan Plateau to an average elevation of 5km is important for understanding key aspects of Cenozoic global climate change, collision tectonics and the evolution of the Asian monsoon, yet quantitative measures of Cenozoic surface height change across Tibet remain few and are sometimes contradictory. Here we report the first exploratory application of a modified Co-existence Approach (CoA) using previously published fossil pollen records to reconstruct quantitatively the Cenozoic minimum palaeoaltitudes of Gangdise-Nyainqentanglha Area of the Tibetan Plateau. GCM simulations were used to adjust Eocene and Miocene raw CoA values for secular climate change and changes in palaeolatitude. This modelled correction increased the CoA-derived altitudes by 895±96m to give a minimum overall Eocene altitude of 3295–3495m. The Miocene correction factor of 481±25m gave an overall minimum altitude estimate of 3000–3150m. For the Holocene CoA returns four equally likely elevations of 4800–4950m, 3800–3900m, 3000–3100m and 2900–3000m. The first of these is indistinguishable from the present day regional average while the others suggest significant upslope pollen transport. Both the Eocene and Miocene palynologically-derived height estimates are consistent with suggestions of significant core plateau elevation by the Eocene, but are likely to underestimate the true palaeoelevation due to pre-Himalayan upslope pollen transport. [ABSTRACT FROM AUTHOR]

Abstract: By applying the Coexistence Approach (CA) to palynological data from the Laohutai, Lizigou, Guchengzi, Jijuntun and Xilutian Formations in Fushun, northeastern China, a quantitative reconstruction of the Palaeocene to Eocene climate is made. During that time, Mean Annual Temperature changed from 11.3 to 21°C, Mean Annual Precipitation from 654 to 1540mm, Mean Temperature of the Warmest Month from 19.4 to 28.2°C, Mean Temperature of the Coldest Month from 3.6 to 13.9°C, Mean Annual Range of Temperature from 12.8 to 23.5°C, Mean Maximum Monthly Precipitation from 175 to 354mm, and Mean Minimum Monthly Precipitation from 8 to 27mm. All the parameters in the five formations indicate a subtropical climate. This situation is different from the current climate at the same site, a mid-temperate and continental monsoon climate, with a Mean Annual Temperature of 6.6°C and a Mean Annual Precipitation of 804mm. In addition, the climatic parameters obtained from megafossil data (only found in the Jijuntun Formation) were analyzed and approximate those from the palynological data. The parameters from the palynological data support the view that the Palaeogene climate of Northeast Asia and North America was similar, but unlike that of Europe. [ABSTRACT FROM AUTHOR]

Abstract: Elucidating the spatio-temporal distributions of terrestrial plants is a key for interpreting the origin of distribution patterns and the tempo of intercontinental disjunction. Nordenskioeldia was distributed in eastern Asia and North America from the Late Cretaceous to the Miocene. Its fossil record provides important information on former patterns of disjunction and dispersal in the Northern Hemisphere. New specimens from the Paleocene of China allow us to further extend the history of the group and provide the impetus to review its distribution in space and time. The comparative morphological survey on fossil Nordenskioeldia found in the Paleocene sediments in both eastern Asia and North America confirms that they belonged to the same morpho-species, which indicates a close floristic continuity between both continents due to land connection available during that time. The spatio-temporal distributions of Nordenskioeldia indicate that the taxon probably expanded eastward from eastern Asia into North America by the end of Early/Middle Maastrichtian, subsequently colonized Greenland, northeastern North America and Spitsbergen in the Early Paleocene, and finally became extinct in the Miocene. The fluctuations in its northern limits took place in response to climate changes: warming from the Paleocene to the Eocene, cooling during the Eocene–Oligocene and amelioration during the Late Oligocene–Mid-Miocene. [Copyright &y& Elsevier]

The Miocene Shanwang biota from eastern China contains exceptionally well-preserved plant fossils with abundant leaf fossils and palynomorphs co-occurring at several levels in the sedimentary succession. This has provided an ideal opportunity to undertake detailed comparative quantitative palaeoclimate reconstruction, based on both mega- and microfloral assemblages, using various approaches, namely the coexistence approach (CoA), leaf margin analysis (LMA) and Climate Leaf Analysis Multivariate Programme (CLAMP). By applying these approaches to the same dataset and using multiple fossil assemblages from different levels we are able to compare results from the different methods of climate prediction. CLAMP and LMA give consistently lower temperature (mean annual temperature, MAT) predictions than the CoA. Taking errors into account all methods indicate no overall climate change through the sequence studied. Results from CoA show overall agreement in the palaeoclimate parameters obtained using both pollen and leaf datasets indicating a high degree of internal consistency with this method. [Copyright &y& Elsevier]

The Hengduan Mountains of Southwest China are considered the most biologically diverse temperate ecosystem in the world. Here, we present a ~ 10,000-year pollen record from Shuanghaizi Lake, northwestern Yunnan, which we use to reconstruct vegetation dynamics, climatic fluctuations and variability in the Indian Summer Monsoon (ISM). The results suggest that, between 10,000 and 7900 cal. yr BP, vegetation comprised mainly mixed needle- and broad-leaved forest (mostly Abies , Pinus , Quercus , and Salix), indicating a warm and humid climate, corresponding to a strong ISM. From 7900 to 6900 cal. yr BP, the mixed needle- and broad-leaved forest persisted, while an increase in Abies pollen and decrease in pollen of Pinus and Salix implies a reduction in temperature and precipitation, suggesting a slightly weaker ISM than in the preceding phase. Between 6900 and 2400 cal. yr BP, an expansion of Pinus and Quercus in mixed needle- and broad-leaved forest, together with the first occurrence of the aquatic Potamogeton , suggest a warmer and more humid climate, likely due to the strengthening monsoon, consistent with the Holocene climatic optimum. From 2400 to 970 cal. yr BP, the vegetation shifted to needle-leaved forest with sparse patches of broad-leaved forest, concurrent with a weakening ISM through the middle of this period. During the first half of the period covering 970 to 470 cal. yr BP, Abies and Picea increased and we inferred the lowest temperature and precipitation of the whole study, implying the weakest ISM. In the middle of this period, an expansion of broad-leaved trees including Quercus , Alnus , Betula and Castanopsis plus diverse herbaceous plants suggests that the climate developed towards warmer and more humid conditions, in agreement with a gradual intensification of the ISM. After 470 cal. yr BP, the vegetation became dominated by needle-leaved forest and most broad-leaved elements became intermittent. Although the climate was generally cool and dry in this period, temperature and precipitation gradually increased compared with the previous stage, indicating a slight intensification of the ISM. These findings provide a more detailed understanding of Holocene vegetation dynamics, climatic change, and the evolution of the palaeomonsoon in the Hengduan Mountains biodiversity hotspot, southwestern China. Unlabelled Image • Pollen record reflects Holocene vegetation dynamics and climate history in SW China • Quantitative climatic data reveal the fluctuations of temperature and precipitation in the Holocene • Changes in summer solar insolation at 30° N may have triggered Holocene variability in ISM intensity [ABSTRACT FROM AUTHOR]

The Younger Dryas (YD) is the most recent abrupt climatic event recognized during the transition from the last glaciation to the Holocene. Growing evidence from the middle and high latitudes of Europe and North America shows that the climate within the YD event was highly unstable. Until recently, however, climate instability during this event has received little attention elsewhere in the world. Here we present evidence of a climatically unstable YD based on pollen-climate transfer function and REDFIT spectral analysis of pollen data from Haligu in the Hengduan Mountains of southwestern China, a low latitude temperate biodiversity hotspot. Our data show that the climate fluctuated significantly during the YD, with three warm peaks recognized at 11.5, 11.7 and 12.3 cal kyr BP. In particular, we estimate a gradual rise in mean annual temperature by 3.7 °C between the end of the YD and the early Holocene (11.2–10.9 cal kyr BP). In response to this, the subalpine conifer forest dominated by Picea and Abies may have migrated about 610 m upwards. We also detected that the climate fluctuations during the YD-Holocene transition show significant centennial periodicities of 76 yr, 84 yr, 91 yr, 95 yr, and 638 yr. The former four cycles are possibly related to the Gleissberg (around 80 yr) solar cycle, which was also detected in the Hongyuan peat, the PC-6 core of the East China Sea and the GISP2 ice core. These new findings enhance our understanding of millennial-scale abrupt climate events which may be of great significance in predicting the impact of future climate change on mountainous ecosystems in southwestern China. The warming at the end of the YD may provide a potential analog for global warming in the near future, during which the upward migration of vegetation zones will likely lead to the loss of habitat for threatened species. We therefore should take action to restore habitats and provide protected areas for species at risk. Unlabelled Image • Three warm peaks during the YD interval were recognized in the Hengduan Mountains. • Climate fluctuations during the YD-Holocene transition show significant periodicities. • Subalpine conifer forest migrated about 610 m upwards at the YD-Holocene transition. [ABSTRACT FROM AUTHOR]