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Biodiversity change under current global warming scenario has attracted wide attentions, representing general stability and balance in ecosystems. Understanding the temporal patterns and potential driving mechanisms of biodiversity changes would provide significant knowledge for ecosystem sustainability, which requires necessary investigations on long-term records during the late Holocene. The high elevation and specific environment on the Qinghai-Tibetan Plateau (QTP) promote the development of fragile alpine ecosystems, responding sensitively to regional climate variations. Based on a high-resolution fossil pollen record retrieved from Lake Kusai on the northern QTP, late Holocene vegetation diversities were estimated based on the Hill number indices, which were subsequently evaluated at three time scales, i.e., millennial, centennial and multi-decadal time scales. The results indicate that Hill number indices could represent vegetation diversity changes on the northern QTP. Reconstructed vegetation diversity indices indicate gradual variations on millennium scale in each diversity index, along with different responses to environmental factors of regional moisture and total solar irradiance. On the centennial time scale, high consistencies were identified among the vegetation diversity indices as well as correlations with environmental factors, revealing overall positive responses between diversity variations and environmental changes. Rather complicated correspondences to environmental factors appeared on the multi-decadal scale, showing different patterns in diversity indices, which illustrates variations through time as well. Accordingly, vegetation diversity changes of the alpine communities on the northern QTP experienced serious variations during the late Holocene, and revealed complicated responses to regional environmental changes, that further investigations particularly at different time scales would be necessary in the future. [ABSTRACT FROM AUTHOR]

A mismatch between model- and proxy-based Holocene climate change, known as the "Holocene conundrum", may partially originate from the poor spatial coverage of climate reconstructions in, for example, Asia, limiting the number of grid cells for model–data comparisons. Here we investigate hemispheric, latitudinal, and regional mean time series and time-slice anomaly maps of pollen-based reconstructions of mean annual temperature, mean July temperature, and annual precipitation from 1908 records in the Northern Hemisphere extratropics. Temperature trends show strong latitudinal patterns and differ between (sub-)continents. While the circum-Atlantic regions in Europe and eastern North America show a pronounced Middle Holocene temperature maximum, western North America shows only weak changes, and Asia mostly shows a continuous Holocene temperature increase. Likewise, precipitation trends show certain regional peculiarities such as the pronounced Middle Holocene precipitation maximum between 40 and 50 ∘ N in Asia and Holocene increasing trends in Europe and western North America, which can all be linked with Holocene changes in the regional circulation pattern responding to temperature change. Given a background of strong regional heterogeneity, we conclude that the calculation of global or hemispheric means, which initiated the Holocene conundrum debate, should focus more on understanding the spatiotemporal patterns and their regional drivers. [ABSTRACT FROM AUTHOR]

The variation of climate over the past 2 000 years is the key to understanding the mechanism of past global changes, and for investigating the correlation between human activity and natural environmental evolution, especially in southwestern China which is directly influenced by the summer monsoon. A 2 050-year continuous sediment core was recovered from the from Beihai Wetland, northwestern Yunnan province. Based on the age-depth model determined by radiocarbon dating, grain size and loss on ignition (LOI) data was used to reconstruct regional climate variation. This showed distinct variations since 2 050 cal. a B. P. The period between 2 050 cal. a B. P. and 1 400 cal. a B.P. was generally dry and cold, especially in the last 300 years of this stage. It then became warm and wet from 1 400 cal. a B.P. to 750 cal. a B.P., temporally consistent with the Medieval Warm Period (MWP). It was cold and dry during the Little Ice Age (LIA) from 750 cal. a B.P. to 300 cal. a B.P., the last 300 years of which was characterized by increasing temperature and moisture. A comparison with historical records from Yunnan showed that the settlements of the Nanzhao and Dali Kingdoms existed mainly in the warm and wet conditions of the MWP. In addition, the variation in population of Yunnan also showed a close correlation with changes in the climate. Both aspects have confirmed the general influence of natural climate change on the evolution of civilization. [ABSTRACT FROM AUTHOR]

• A new Holocene Organic Carbon Accumulation Rate (OCAR) record from southwest China. • Temporal pattern of OCAR and response to climate/environment changes are evaluated. • Synchronous late Holocene increases in OCAR are widely reported from southwest China. • Long-term variations in OCAR respond closely to intensity of Asian Summer Monsoon. The deposition of organic carbon (OC) in terrestrial water bodies serves as an important carbon sink in global carbon cycle, while the responding mechanism of organic carbon accumulation rate (OCAR) to various climate processes is still unclear. Here, we provide a continuous sediment record covering the past 11.1 kyrs retrieved from Beihai Wetland, which is predominantly influenced by the Indian Summer Monsoon (ISM) in southwest China. The temporal variation of OCAR was established and classified into five evolution stages. Subsequently, potential responses of OCAR to climatic and environmental processes were evaluated based on the Spearman's rank correlation analysis between OCAR and individual sedimentary proxies. During the early Holocene, relatively stable and low OCAR was determined owing to the predominant contributions of detrital influx and low terrestrial organic matters. Following the intensification of summer monsoon and corresponding increase in regional precipitation, extremely low OCAR were yielded in the mid-Holocene, resulted from low values of both sedimentary accumulation rate (SAR) and Loss on Ignition (LOI). The abrupt retreat of ISM led to the development of current wetland from a lake-like system, while the extremely low SAR contributed significantly to the identified low OCAR values between 5.2 and 3.0 cal. kyr BP. Afterwards, the wetland developed progressively following further retreat of ISM, that the preservation of a great amount of organic matters contributed significantly to both SAR and LOI, resulting in the highest OCAR levels during the Holocene. In addition, the rapid decline of OCAR during the last 700 years was interpreted in terms of intensified regional human activities. Such increase in OCAR during the late Holocene was broadly reported from the southwest China, proposing potential responses to the large-scale climate changes, namely the variation of ISM. [ABSTRACT FROM AUTHOR]

• A continuous Holocene sediment record was recovered from southwestern China. • Grain size and elements represented catchment erosions and regional moisture changes. • Mid-Holocene intensification of ISM was modulated by tropical Indian Ocean SST modes. • Synchronous positive phases of IOB and IOD modes triggered the strengthening of ISM. The evolution of the Indian Summer Monsoon (ISM) has been widely investigated owing to its significant climatic and socioeconomic influences. However, debates remain concerning the temporal variation during the Holocene and its driving mechanisms, particularly the potential contribution of sea-surface temperature (SST) in the tropical Indian Ocean (TIO). Here, we present a continuous sediment record covering the past 11.1 kyrs from the Beihai Wetland, southwestern China. The grain size, geochemical element composition and total organic carbon content (TOC) were analyzed and interpreted in terms of the sedimentary conditions, catchment erosion and regional climate variations. Higher detrital inputs and possibly high water levels were determined during the early to mid-Holocene period, suggesting strong catchment erosion under an intensified ISM. The maximum monsoon intensity appeared between 7.5 and 5.2 cal. kyr BP, which is broadly consistent with various ISM records. We propose that such mid-Holocene monsoon strengthening was primarily triggered by the TIO SST anomaly modes, i.e., the Indian Ocean Basin (IOB) mode and the Indian Ocean dipole (IOD) mode. Based on Holocene SST records from the TIO, a positive SST anomaly (positive IOB mode) and positive zonal SST anomaly gradient (positive IOD mode) may have occurred during the mid-Holocene, which jointly triggered intensification of the ISM. Our findings emphasize the significant contribution of the TIO in modulating the summer monsoon system. The abrupt increases in TOC content and median grain size indicate the formation of the current wetland system at approximately 5.2 cal. kyr BP following the decline in regional moisture as well as the retreat of the ISM. In addition, notable human impacts were determined during the last 800 years, as indicated by intensified catchment erosion in response to human-induced deforestation. [ABSTRACT FROM AUTHOR]

Abstract: The numerical meta-analysis of 92 proxy records (72 sites) of moisture and/or temperature change confirms earlier findings that the dominant trends of climatic evolution in monsoonal central Asia since the Last Glacial roughly parallel changes in Northern Hemisphere summer insolation, i.e. the period following the Last Glacial Maximum was characterized by dry and cold conditions until 15cal. kyr BP, followed by a warm, wet period coincident with the Bølling/Allerød warm period and terminated by a cold, dry reversal during the Younger Dryas period. After an abrupt increase at the start of the Holocene, warm and wet conditions prevailed until ca. 4cal. kyr BP when moisture levels and temperatures started to decrease. Ordination of moisture records reveals strong spatial heterogeneity in moisture evolution during the last 10cal. kyr. The Indian Summer Monsoon (ISM) areas (northern India, Tibetan Plateau and southwest China) exhibit maximum wet conditions during the early Holocene, while many records from the area of the East Asian Summer Monsoon indicate relatively dry conditions, especially in north-central China where the maximum moisture levels occurred during the mid-Holocene. We assign such phenomena to strengthened Hadley Circulation centered over the Tibetan Plateau during the early Holocene which resulted in subsidence in the East Asian monsoonal regions leading to relatively dry conditions. Our observations of the asynchronous nature of the two Asian monsoon subsystems on millennial time scales have also been observed on annual time-scales as well as implied through the spatial analysis of vertical air motion patterns after strong ascending airflows over the Tibetan Plateau area that were calculated from NCEP/NCAR reanalysis data for the last 30years. Analogous with the early Holocene, the enhancement of the ISM in a ‘future warming world’ will result in an increase in the asynchronous nature of the monsoon subsystems; this trend is already observed in the meteorological data from the last 15years. [Copyright &y& Elsevier]

• Late Holocene climate variation was inferred from barely investigated northern TP. • Variation of mirabilite represented temperature change assisted by Pitzer model. • Sediment grain size and subsequent end-members indicated regional moisture variation. • Regional moisture change was driven by NAO and migration of mid-latitude westerlies. • Solar activity expresses significant effects on late Holocene temperature change. Understanding late Holocene climate variation on the northern Tibetan Plateau is essential for understanding regional climate dynamics, especially the potential response to mid-latitude westerlies. A continuous lacustrine sediment record covering the past 1500 years was recovered from Lake Ayakum on the northern margin of the Tibetan Plateau, in which a typical cold-phase mineral (mirabilite) was detected. Assisted by the simulation results in the Pitzer model, the preservation of mirabilite in the sediment core as well as its relative proportion was interpreted in terms of past temperature variations, in which a high mirabilite content corresponded to a relatively cold environment. Grain size analysis and subsequent end-member modeling results revealed potential correlations with regional moisture conditions, that more coarse materials were transported by increased river discharge under relatively wet conditions. The results showed that cold and humid conditions dominated the Dark Age Cold Period and Little Ice Age, while warm and dry conditions dominated the Medieval Warm Period. Following the increase in regional temperature, more coarse materials were deposited during the last 200 years owing to probable increased fluvial transport supplied by glacier meltwater. The overall temperature and moisture variations were broadly consistent with records from western China and central Asia, indicating that the northern Tibetan Plateau was predominately influenced by the mid-latitude westerlies during the late Holocene. In addition, the temperature change showed a close correlation with solar irradiance, pointing to a potential response to solar activity. On the other hand, the moisture change responded sensitively to the North Atlantic Oscillation and the migration of mid-latitude westerlies. [ABSTRACT FROM AUTHOR]

Improved studies of past vegetation change are required to better understand the variation of alpine ecosystems on the Qinghai-Tibetan Plateau (QTP) in response to future climate change. Spatial and temporal variations of past vegetation can be traced by fossil pollen data mapping. In this paper, we synthesized 57 continuous pollen records on the QTP covering the past 15 kyr to depict large-scale vegetation change and its response to climate variations. In order to minimize potential chronological biases, age-depth models were revised using a state-of-the-art and consistent method for all the records. The spatial and temporal variation of major pollen taxa were examined based on interpolated pollen maps at 1000-year intervals. The arboreal pollen (AP, mainly of Pinus , Betula and Abies / Picea) content expressed significant climate signals over a broad spatial and temporal gradient. During the late glacial period, high proportions of AP widely occurred in regions that are presently unforested owing to the sparse local vegetation coverage. For the Holocene period, AP showed relatively high contributions in records from the southeastern margin of the QTP, with a decreasing gradient in abundance towards the northwest. The transportation of AP to unforested regions corresponds closely to the intensity of monsoon wind, which can be used to track the Holocene evolution of the summer monsoon. The dominant shrub and herbaceous taxa (including Artemisia , Chenopodiaceae, Cyperaceae, Poaceae and Ephedra) generally represent developments of local vegetation responding to climate variations. In addition, the persistent increase in Poaceae pollen during the mid to late Holocene correlates possibly to regional human activities. The inferred spatial and temporal patterns of major pollen types on the QTP provide significant knowledge about long-term vegetation change and its potential response to climate variations. • An initial plateau-scale examination of fossil pollen records on the Tibetan Plateau. • Spatial and temporal patterns of major pollen types were mapped at 1000-year interval. • Arboreal pollen from unforested plateau surface represents intensity of summer monsoon. • Herbaceous pollen reveals local vegetation development in response to climate change. [ABSTRACT FROM AUTHOR]

The Indian Summer Monsoon (ISM) is one of the most important climate systems, whose variability and driving mechanisms are of broad interest for academic and societal communities. Here, we present a well-dated high-resolution pollen analysis from a 4.82-m long sediment core taken from Basomtso, in the southeastern Tibetan Plateau (TP), which depicts the regional climate changes of the past millennium. Our results show that subalpine coniferous forest was dominant around Basomtso from ca. 867 to ca . 750 cal. yr BP, indicating a warm and semi-humid climate. The timberline in the study area significantly decreased from ca. 750 to ca. 100 cal. yr BP, and a cold climate, corresponding to the Little Ice Age (LIA) prevailed. Since ca. 100 cal. yr BP, the vegetation type changed to forest-meadow with rising temperatures and moisture. Ordination analysis reveals that the migration of vegetation was dominated by regional temperatures and then by moisture. Further comparisons between the Basomtso pollen record and the regional temperature reconstructions underscore the relevance of the Basomtso record from the southeastern TP for regional and global climatologies. Our pollen based moisture reconstruction demonstrates the strong multicentennial-scale link to ISM variability, providing solid evidence for the increase of monsoonal strengths over the past four centuries. Spectral analysis indicates the potential influence of solar forcing. However, a closer relationship has been observed between multicentennial ISM variations and Indian Ocean sea surface temperature anomalies (SSTs), suggesting that the variations in monsoonal precipitation over the southeastern TP are probably driven by the Indian Ocean Dipole on the multicentennial scale. [ABSTRACT FROM AUTHOR]

Abstract: A sediment core from a closed basin lake (Lake Kuhai) from the semi-arid northeastern Tibetan Plateau was analysed for its pollen record to infer Lateglacial and post glacial vegetation and climatic change. At Lake Kuhai five major vegetation and climate shifts could be identified: (1) a change from cold and dry to relatively warmer and more moist conditions at 14.8 cal ka BP; (2) a shift to conditions of higher effective moisture and a stepwise warmer climate at 13.6 cal ka BP; (3) a further shift with increased moisture but colder conditions at 7.0 cal ka BP; (4) a return to a significantly colder and drier phase at 6.3 cal ka BP; (5) and a change back to relatively moist conditions at 2.2 cal ka BP. To investigate the response of lake ecosystems to climatic changes, statistical comparisons were made between the Lake Kuhai pollen record and a formerly published ostracod and sedimentary record from the same sediment core. Furthermore, the pollen and lacustrine proxies from Lake Kuhai were compared to a previously published pollen and lacustrine record from the nearby Lake Koucha. Statistical comparisons were done using non-metric multidimensional scaling and Procrustes rotation. Differences between lacustrine and pollen responses within one site could be identified, suggesting that lacustrine proxies are partly influenced by in-lake or local catchment processes, whereas the terrestrial (pollen) proxy shows a regional climate signal. Furthermore, we found regional differences in proxy response between Lake Kuhai and Lake Koucha. Both pollen records reacted in similar ways to major environmental changes, with minor differences in the timing and magnitude of these changes. The lacustrine records were very similar in their timing and magnitude of response to environmental changes; however, the nature of change was at times very distinct. To place the current study in the context of Holocene moisture evolution across the Tibetan Plateau, we applied a five-scale moisture index and average link clustering to all available continuous palaeo-climate records from the Tibetan Plateau to possibly find general patterns of moisture evolution on the Plateau. However, no common regional pattern of moisture evolution during the Holocene could be detected. We assign this to complex responses of different proxies to environmental and atmospheric changes in an already very heterogeneous mountain landscape where minor differences in elevation can cause strong variation in microenvironments. [Copyright &y& Elsevier]

Climate change on the southeastern Tibetan Plateau (TP) is assumed to impact lake ecosystems. However, parallel changes in climate and non-climate factors and mediation of signals by catchment processes complicate the assessment of climate-change effects on lake ecosystems requiring long-term and high resolution multi-variable time-series. Here we present a diatom record from sediments in the lake Basomtso, southeastern TP, covering the period 1083–2012 CE with sub-decadal resolution which we relate to available proxies for potential climate and non-climate factors. The record is dominated by planktonic species and the compositional change is mainly characterized by alternations between big- and small-celled Pantocsekiella ocellata and between planktonic and benthic diatom species. The diatom assemblages show a decrease of P. ocellata (big form) since the end of 17th century and an increase of P. ocellata (small form) as well as an increase in diatom productivity, reflecting changes on a centennial timescale which mainly follow temperature increase. We recorded several changes in the ratio of planktonic to benthic species abundance (P: B) on a sub-decadal or decadal timescale. Noticeable decreases in P: B were a result of rapid sedimentary events caused by high energy flows. Cross-correlation analyses reveal synchronous responses of diatoms and asynchronous responses of terrestrial vegetation to regional temperature change, indicating a higher potential of lake diatoms to detect the timing and magnitude of climate shifts on the southeastern TP. The results imply that aquatic ecosystems in Basomtso, as well as in other mountain lakes on the southeastern TP, are probably subject to a larger risk of regime shift than terrestrial ecosystems under future climate scenarios. Conceptual model of the effects of centennial-scale climate change and short-lived sedimentary events on diatom composition in Basomtso. Rising temperature promotes diatom productivity and favors small-cell planktonic species. The responses of terrestrial vegetation are slower than that of lacustrine diatoms which change synchronously with temperature. Sedimentary events caused by high-energy inflow or subaqueous slumps alter diatom composition by introducing more benthic diatoms from the catchment or the littoral zone. Image 1 • Rising temperature promotes diatom productivity and favor small-cell planktonic species. • Sedimentary events alter sediment diatom composition by introducing more benthic diatoms. • Terrestrial vegetation response to climate change slower than that of lacustrine diatoms. • Aquatic ecosystems are subject to a larger risk of regime shift than terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

We present a calibration-set based on modern pollen and satellite-based Advanced Very High Resolution Radiometer (AVHRR) observations of woody cover (including needleleaved, broadleaved and total tree cover) in eastern continental Asia, which shows good performance under cross-validation with the modern analogue technique (all the coefficients of determination between observed and predicted values are greater than 0.65). The calibration-set is used to reconstruct woody cover from a taxonomically harmonized and temporally standardized fossil pollen dataset (including 274 cores) with 500-year resolution over the last 22 kyr. The spatial range of forest has not noticeably changed in eastern continental Asia during the last 22 kyr, although woody cover has, especially at the margin of the eastern Tibetan Plateau and in the forest-steppe transition area of north-central China. Vegetation was sparse during the LGM in the present forested regions, but woody cover increased markedly at the beginning of the Bølling/Allerød period (B/A; ca. 14.5 ka bp ) and again at the beginning of the Holocene (ca. 11.5 ka bp ), and is related to the enhanced strength of the East Asian Summer Monsoon. Forest flourished in the mid-Holocene (ca. 8 ka bp ) possibly due to favourable climatic conditions. In contrast, cover was stable in southern China (high cover) and arid central Asia (very low cover) throughout the investigated period. Forest cover increased in the north-eastern part of China during the Holocene. Comparisons of these regional pollen-based results with simulated forest cover from runs of a global climate model (for 9, 6 and 0 ka bp (ECHAM5/JSBACH ∼1.125° spatial resolution)) reveal many similarities in temporal change. The Holocene woody cover history of eastern continental Asia is different from that of other regions, likely controlled by different climatic variables, i.e. moisture in eastern continental Asia; temperature in northern Eurasia and North America. [ABSTRACT FROM AUTHOR]

Fires are sensitive to climate changes, and in addition they have a major influence on the global carbon cycle, land-surface properties, and chemical composition of the atmosphere, which in turn can affect the climate system. Projecting the impacts of future climate changes on fire-mediated biogeochemical processes requires understanding of how various climatic factors influence regional fire regimes. However, long-term variations in fire activity and their controls are poorly known. In this study, we report the concentration of black carbon (BC) and its isotopic composition (δ 13 C BC ) in an upland lake sediment core from southwest China in order to elucidate linkages between changes in fire regime, climate and vegetation over the past 18.5 ka. The results show that the sedimentary BC content recorded variations in fire activity and exhibits a close negative correlation with the amount of precipitation delivered by the Indian Summer Monsoon (ISM). During Heinrich Event 1(18.5–15.0 cal ka BP), the Younger Dryas (12.8–11.1 cal ka BP) and the mid- to late-Holocene, the weakening of the ISM led to greatly increased fire activity in southwest China. In the last 1.0 ka, the BC record may have been affected by human activity in the catchment which may have caused an increased influx of minerogenic material to the lake thereby diluting the sedimentary BC concentration. The general trend of changing vegetation compositions inferred from the δ 13 C BC values also tracks the variations of the ISM, suggesting a change from mixed C 3 /C 4 -plant ecosystems during the last glacial maximum to C 3 -plant-dominated forest during the Holocene. However, the abundance of C 4 plants may be overestimated during the Bølling–Allerød warm interval and the early Holocene due to the fact that fires were probably limited to the savanna ecosystem in the valleys and low-lying basins. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pollen record since mid-MIS 3 was provided for a current-hyperarid region of China. • The climate was subhumid during the mid-late MIS 3 and hyperarid during the Holocene. • Insolation and ice volume were the forcing mechanisms for climate changes in the Jilantai Basin. The climate conditions of the marginal region of the Asian summer monsoon (ASM) domain during Marine isotope stage (MIS) 3 (60–27 cal kyr BP) are poorly understood and require further study. Here, we collected fossil pollen samples from a 24.0-m-long drill core from Jilantai Salt Lake (Inner Mongolia, China) to reconstruct the regional climate changes since mid-MIS 3. During 47.0–43.0 cal kyr BP, the frequencies of the occurrence of aquatics and Pediastrum indicate relatively humid conditions. At approximately 43.0 cal kyr BP, the climate became dry, as revealed by the increase in Ephedra and the reduced aquatics and Pediastrum concentrations. The climate during 43.0–27.1 cal kyr BP was drier than that in the previous interval. Aquatics, ferns, and algae were barely detectable, indicating harsh climate conditions during 27.1–12.2 cal kyr BP. During the Holocene, aquatics and algae vanished, and the observed pollen assemblages were dominated by herb taxa; however, a substantial loss of taxa numbers occurred, suggesting that the climate was hyperarid. In general, the climate was relatively humid during the mid-late MIS 3, arid during MIS 2 (27.0–11.7 cal kyr BP), and hyperarid during the Holocene. The evaporation capacity connected with the Northern Hemisphere summer insolation and the Northern Hemisphere ice volume may have played a vital role in vegetation and climate changes in the Jilantai Basin since mid-MIS 3. [ABSTRACT FROM AUTHOR]

Abstract: Little is known about decadal- to centennial-scale climate variability and its associated forcing mechanisms on the Qinghai–Tibetan Plateau. A decadal-resolution record of total organic carbon (TOC) and grainsize retrieved from a composite piston core from Kusai Lake, NW China, provides solid evidence for decadal- to centennial-scale Asian monsoon variability for the Northern Qinghai–Tibetan Plateau during the last 3770 yr. Intensified winter and summer monsoons are well correlated with respective reductions and increases in solar irradiance. A number of intensified Asian winter monsoon phases are potentially correlated with North Atlantic climatic variations including Bond events 0 to 2 and more recent subtle climate changes from the Medieval Warm Period to the Little Ice Age. Our findings indicate that Asian monsoon changes during the late Holocene are forced by changes in both solar output and oceanic–atmospheric circulation patterns. Our results demonstrate that these forcing mechanisms operate not only in low latitudes but also in mid-latitude regions (the Northern Qinghai–Tibetan Plateau). [Copyright &y& Elsevier]

Montane vegetation belts are sensitive to climate change; however, it is uncertain to what degree their evolution is influenced by changes in mean annual temperature or seasonal climate. In this study, we use pollen assemblages from a high elevation lake (3780 m.a.s.l.) in the Gongga Mountains on the southeast margin of the Qinghai-Tibetan Plateau, China, to study changes in altitudinal vegetation zones during the last 12,000 years. The relationships between vegetation belts and winter and summer climate parameters are analyzed. Results indicate that winter temperature mainly controlled the development of evergreen broadleaved forest (Cyclobalanopsis and Taxodiaceae), deciduous broadleaved forest (Betula), and sub-alpine shrubland (Rosaceae, Cyperaceae and Gramineae dominated). In contrast, the development of temperate coniferous forest (Pinus and Tsuga) and alpine herbfield (Artemisia and Chenopodiaceae) was mainly controlled by summer temperature and precipitation. Results show that winter temperature gradually increased from the Greenlandian to Meghalayan, indicating that the main driving factor was winter solar insolation in the Northern Hemisphere. Meanwhile, changes in summer temperature and precipitation are consistent with the results from Indian monsoon-dominated areas of China, suggesting that the summer climate in this region is mainly driven by the migration of the Intertropical Convergence Zone. Our findings suggest that the influence of seasonal climate changes should be considered on the evolution of montane vegetation belts. • The vegetation dynamics in SW China are reconstructed during the Holocene. • Contrasting effects of seasonal climate on altitudinal vegetation belts evolution. • Winter temperature followed gradual decline with winter insolation in the NH. • Summer climate is mainly driven by migration of the ITCZ under insolation forcing. [ABSTRACT FROM AUTHOR]