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... The Changbai Mountain range is a major volcanic region in East Asia, which experienced intensive volcanic activity during the Cenozoic era, creating depressions in the landscape that promoted the development of peatlands (Liu 1989;Fan et al. 2002;Fan 2008;Zhao and Liu 2012;Li et al. 2017b). Among them, the Gushantun (GST) peatland has a relatively complete and long history that can be traced back 13 000 years and has been well studied (Liu 1989;Li et al. 2013bLi et al. , 2014Li et al. , 2017bGao et al. 2018b;Zhao and Liu 2012). ...
... The Changbai Mountain range is a major volcanic region in East Asia, which experienced intensive volcanic activity during the Cenozoic era, creating depressions in the landscape that promoted the development of peatlands (Liu 1989;Fan et al. 2002;Fan 2008;Zhao and Liu 2012;Li et al. 2017b). Among them, the Gushantun (GST) peatland has a relatively complete and long history that can be traced back 13 000 years and has been well studied (Liu 1989;Li et al. 2013bLi et al. , 2014Li et al. , 2017bGao et al. 2018b;Zhao and Liu 2012). The GST peatland (42818 0 22.1 00 N, 126816 0 57.7 00 E) is located to the west of the Changbai Mountains and belongs to the Longgang volcanic group (Fig. 1). ...
... The peatland is nearly circular in shape with a diameter of ,1000 m and is surrounded by Cenozoic basalt. Long-term water accumulation has resulted in the development of the peatland with an average of ,7 m of accumulated peat (Liu 1989;Li et al. 2013bLi et al. , 2014Li et al. , 2017b. ...
The Changbai Mountains forest ecosystem is one of the best-preserved temperate mountain forest ecosystems in Asia. Since the establishment of the reserve in 1960, extensive forest fires have been excluded as a result of strict regulation and suppression efforts and thus fuels have accumulated for several decades. Due to the lack of historical fire records in the area, the risk of fire occurrence cannot be properly estimated. In this study, we used charcoal records to reconstruct the palaeo-fire frequency in the Changbai Mountains during the last 13 000 years. The results indicate that fires were frequent during 13.0–11.0, 7.0–6.0, and 2.5–2.0 calender (cal) kyr before present (BP) and from 1.0 cal kyr BP to the present. The fire frequencies are largely consistent with other palaeoenvironmental records from the study area and we conclude that since 13.0 cal kyr BP fires were more frequent at the regional scale during intervals of a weak summer monsoon, caused by a cold and dry climate and the abundance of flammable trees. Archaeological data from the study area since 3.0 cal kyr BP indicate increasing human activity, which dominated the occurrence of local fires. In addition, intermittent volcanic activity influenced the occurrence of fires during the past millennium.
... The Gushantun (GST) peatland is developed within a relatively low-lying platform area. Its surrounding plants are mainly Cenozoic basalt and its diameter is~1,000 m (Liu, 1989). We obtained peat sediment cores in the summer of 2009 using an Eijkelkamp peat sampler. ...
... Notably, there is disparity regarding the timing of the onset of the Holocene in the study region. Pollen analysis results for the GST region indicate that the climate became warm around 10,000 cal yr BP, and that the regional temperature increased from the Late Glacial period to the Holocene (Liu, 1989). The δ 18 O record of cellulose in Hani peatland also indicates a significant decrease at~11,300 cal yr BP, and that this date is defined as the beginning of the Holocene . ...
... The phytolith data in our dataset indicate that precipitation was concentrated within the range of~500-700 mm. The pollen of boreal coniferous trees almost disappeared at this time, and the major vegetation types turned into the temperate broadleaf deciduous forest (Liu, 1989). The phytolith and pollen records reveal that there was a stepwise increase in temperature and precipitation of the regional climate. ...
Phytoliths can act as efficient carriers of information about palaeovegetation and palaeoclimatic conditions, but the representativeness of soil phytoliths from palaeoecological sediments has not been fully understood. In this study, phytolith assemblages in topsoils and associated plant communities at 55 sites in Northeast China were compared. The results indicate that samples from herbaceous and woody communities could be reliably differentiated by topsoil phytoliths. Notably, different phytolith types exhibit varying degrees of representational bias in terms of the aboveground plant community. Some morphotypes (e.g., bilobate, rondel and lanceolate) over‐represent the richness of the corresponding plant; some morphotypes, including microhair, conical epidermal, silicified stomata and epidermal phytoliths, under‐represent the parent plant abundance; additional morphotypes (e.g., elongate, saddle and trapeziform sinuate) are consistent with the changes of associated plants. Based on the representational bias, we calibrated the percentages of topsoil phytoliths and established a phytolith‐based transfer function for precipitation in Northeast China. A palaeoclimate reconstruction in the Changbai Mountains (in the eastern part of Northeast China) based on the above phytolith‐based transfer function for precipitation shows that the region has gone through continuous climatic changes since the late glacial period: from cold and dry conditions to warm and dry conditions, then to warm and wet conditions, and finally to cool and dry conditions. The phytolith‐based reconstructed climate changes since the late glacial period correspond well to those reconstructed by other records from the same stratigraphic profile, and our phytolith‐based climatic reconstruction also confirms the reliability of abrupt cold climatic shifts at 8.2, 6.8, 5.6, 4.6 and 4.2 ka. In conclusion, our results provide the basis for the reliability of phytoliths for reconstructing climatic changes in the northern temperate region.
Highlights
• Calibrating soil phytolith assemblages for any quantitative palaeovegetation reconstruction using phytoliths is necessary.
• Phytolith morphotypes in topsoils may over‐ or under‐represent or agree with the abundance of modern plant taxa.
• Phytolith‐based climatic reconstruction corresponds well with the abrupt climate changes evident since the Late Glacial period and other proxy records.
... In northeastern China, there is a strong moisture gradient which has been recognized by the international geosphere biosphere program (IGBP) as a control on vegetation cover and environment. Taiga forest, mixed coniferous-deciduous forest, and deciduous forest spread from North to South and as vertical vegetation zonation on Mountains (Liu, 1989;Li et al., 2001). Therefore, change in these typical terrestrial ecosystems is regarded as an ideal place to study vegetation dynamics in relation to climate change. ...
... Northestern China has many published pollen records to study Holocene vegetation (The Quaternary Pollen Group of the Guiyang Geochemistry Institute, 1977;Liu, 1989), to reconstruct environment (Sun and Yuan, 1992;Xia, 1988Xia, , 1992Kong and Du, 1984;Li et al., 2000), and to consider the relationship between vegetation succession and environmental change Machida et al., 1990). However, there are still problems related to low resolution chronology precision, to assist reconstruction of the mechanisms of vegetation change, especially where fire events may control vegetation changes. ...
... Before the once in a millennium scale eruption of the Tianchi volcano in the Changbaishan Mountain, a mixed forest of Picea-Pinus and deciduous broadleaved trees developed below 950 m a.s.l., which was slightly higher than it is today (Li, 2002). An analysis of buried woods clearly shows that the pre-eruption vegetation was characterized by a vertical zonation, such as Picea-Abies forest above 1300 m a.s.l., and mixed forest of Pinus and deciduous broadleaved trees below (Li, 2002;Liu, 1989). ...
Volatiles erupted from large-scale explosive volcanic activities have a significant impact on climate and environmental changes. As an important ecological factor, the occurrence of fire is affected by vegetation cover, and fire can feed back into both vegetation and climatic change. The causes of fire events are diverse; and can include volcanic eruptions. The amount of charcoal in sediment sequences is related to the frequency and intensity of fire, and hence under good preservation conditions fire history can be reconstructed from fossil charcoal abundance. Until now, little research on the role of fire has been carried out in northeastern China. In this study, through research on charcoal and tephra shards from Gushantun and Hanlongwan, Holocene vegetation change in relation to fire and volcanic events in Jilin, Northeastern China, was investigated. Where tephra shards are present in Gushantun it is associated with low level of both conifers and broadleaved trees, and is also associated with a pronounced charcoal peak. This suggests forest cover was greatly reduced from a fire caused by an eruption of the Tianchi volcano. We also detected one tephra layer in Hanlongwan, which also has the almost same depth with low level forest pollen values and one charcoal peak. This was caused probably by an eruption of the Jinlongdingzi volcano.
... The vegetation is very sensitive to the variation of the East Asian Monsoon (EAM; Zhou et al., 2002). The climate changes in this area were nearly synchronous with changes in East China during the Holocene (Xia, 1988;Liu, 1989;Sun and Yuan, 1990;Yuan and Sun, 1990;Hong et al., 1997Hong et al., , 2001Wang and Liu, 2001). Both climate change and human activities may have influenced the vegetation during the mid-Holocene (Foley et al., 1994). ...
... More studies need to be done to reveal the relationship between human influence and forest development. Palynological analyses of Holocene peat sequences revealed vegetation and climate changes from forested areas of the Dongbei plain (Xia, 1988;Liu, 1989;Yuan and Sun, 1990). These studies focus on peat that may reflect vegetation variations of a small area. ...
... Pinus-dominated forest was broadly distributed 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 in Changbai Mountain and Sanjiang plain after about 5800 cal. BP (5000 14 C a BP; Liu, 1989;Sun and Yuan, 1990;Yuan and Sun, 1990;Li et al., 2005). Peat and black soil also formed after about 5800 cal. ...
Vegetation and climate changes in Northeast China during the Late Quaternary are poorly known. Pollen analyses were undertaken on a 890-cm-long lacustrine sediment core recovered from Jingbo Lake, located in Southeastern Heilongjiang Province, China. Based on 14C dating, the pollen record provides a basis for the reconstruction of vegetation and climatic changes since 9600 cal. BP in NE China. Prior to 6100 cal. BP, broad-leaved deciduous forest of Quercus, Fraxinus, and Betula dominated this area, which indicates that the climate during this period was warm and the Asian summer monsoon was stronger. From 6100 to 5600 cal. BP, the deciduous trees declined and Pinus increased, which suggests a transition of vegetation from broad-leaved deciduous forest to mixed coniferous–deciduous forest. Mixed coniferous–deciduous forest with Pinus, Quercus, and Betula expanded and dominated since 5600 cal. BP, indicating a gradual weakening of the Asian summer monsoon. During 2000–680 cal. BP, trees such as Pinus and Quercus declined and herbs including Artemisia, Labiatae, and Scrophulariaceae increased, indicating an extensive human impact on the vegetation. After 680 cal. BP, the forest regenerated due to changed agricultural activities, although the forest was cleared after the 18th century. The vegetation changes superimposed upon this general trend, especially the abundance of trees demanding warm climate conditions, show eight low temperature events at 9200–9000, 8200, 7000–6900, 6000–5600, 4200–3800, 2200–1800, 800, and 600 cal. BP. These short-lived events can be correlated to the spells of δ18O depletion in the Dongge Cave stalagmite record, which is widely accepted as a summer monsoon record.
... samples. In some cases, compounds 1 and 7 show comparable abundance to that of the dominant nC 23 and nC 25 alkanes. However, the concentration of these des-A-triterpenes decreases to almost zero at 10 cm of the top peat section (Figure 1). ...
... From the bottom to about 14100 cal a BP, the total des-A-triterpenes abundance is lowest in the whole sequence and the ratios of DT/MT and DL/(MT+DT) are higher (Figures 3 and 4). The pollen records indicated the lake clay accumulated and the vegetation was sparse and reflected to be somewhat comparable with the tundra-type during the periods between 13400 and 11400 a at the Gushantun bog (42°N, 126°E) which is not far away from the Hani region [23]. The tundra-like vegetation indicates a low temperature climate and is not favourable to the development of vegetation [23]. ...
... The pollen records indicated the lake clay accumulated and the vegetation was sparse and reflected to be somewhat comparable with the tundra-type during the periods between 13400 and 11400 a at the Gushantun bog (42°N, 126°E) which is not far away from the Hani region [23]. The tundra-like vegetation indicates a low temperature climate and is not favourable to the development of vegetation [23]. This period is the transition from the last maximum glacial period to last deglaciation. ...
Aliphatic des-A-triterpenes, the degradation products of pentacyclic triterpenes have been tentatively assigned in samples taken from a
963-cm-thick peat sequence from the Hani region of Northeast China using gas chromatography-mass spectrometry (GC-MS) in order
to understand and identify these des-A-triterpenes response to climate and ecology. The study indicates that aliphatic des-A-triterpenes are abundant in the Hani peat bog. The high relative abundance of the total des-A-triterpenes mainly occurs at the Holocene periods and is corresponding to the low sedimentation rate. The mechanism of
des-A-triterpenes accumulation is not consistent with the previous studies. It is proposed that the biological community is also
one influence factor. The obvious stage variations of the total des-A-triterpenes in the whole sequence reveal the different biological (microbes and plants) processes and responses, possibly
revealing the four large replacements of biological community and functional composition in the swamp environment over the
16000 cal a BP. The low total des-A-triterpenes values occur at about 10200, 8700, 7700, 6600, 4480–3940 and 3040 cal a BP, reflecting the multiple millennial
micro-environment oscillations under the macro-environment of the swamp during the Holocene. The ratios of diene and monoene
des-A-triterpenes (DT/MT), des-A-lupane and diene and monoene des-A-triterpenes (DL/(DT+MT)), ratios of individual compounds exhibit vertical opposite to the total des-A-triterpenes. Namely, these ratios are high during the last deglaciation and late Holocene whereas they are low at other
periods, indicating different compounds have different responses to micro-environment and microbial activities. This study
discusses the diversity of biological community and biological functional composition response to micro-environment, which
not only provides the complement in Northeast China, but also bears important fundamental information for the implication
to ecological environment in the future.
KeywordsNortheast China-peat-swamp environment-
des-A-triterpene-distribution-ecological significance
... Considerable attention has been directed to the history of Chinese monsoon climate (e.g., Zhou et al., 1984, Li andLiang, 1985;Xia, 1988;Liu, 1989;Yang, 1989;Sun and Yuan, 1990;An et al., 1990b;Shi et al., 1992). Of signi"cance to this history is the Holocene optimum, not only because it was an important recent climatic episode, and produced a varied array of geologic records, but also because it might serve as an important analog for future climatic change in this region. ...
... Region A (northeastern China) is mainly characterized by an interconnected system of Holocene lakes and swamps that drain externally, but are sensitive to climatic change (Harrison and Digerfeldt, 1993). Four lakes, Gushantun of Jilin (Liu, 1989), Jingchuan (Sun and Yuan, 1990), Qindeli of Heilongjiang (Xia, 1988), and Hulonghu ...
... A similar increase in Betula ca. 11,000 yr BP has also been observed in the Gushantun pro"le (Liu, 1989). The Jingchuan pro"le ( Fig. 3, a ) has a similar pattern, with a steady high in broadleaf pollen (Quercus, Ulmus, and Juglans) since at least 10,000 yr BP. ...
The spatial and temporal distribution of summer monsoon precipitation (or effective moisture) during the Holocene has been reconstructed on the basis of geological data, including lake levels, pollen profiles, and loess/paleosol records. In addition, the summer (July) precipitation increment, effective precipitation, and monsoon strength index have been obtained from numerical modeling experiments. Both geological data and numerical modeling indicate that the Holocene optimum, as defined by peak East Asian summer monsoon precipitation, was asynchronous in central and eastern China, reaching a maximum at different times in different regions, e.g., ca. 10,000–8000 yr ago in northeastern China, 10,000–7000 yr ago in north-central and northern east-central China, ca. 7000–5000 yr ago in the middle and lower reaches of the Yangtze River, and ca. 3000 yr ago in southern China. In southwestern China the maximum appeared ca. 11,000 yr ago, but probably was related to the maximum landward extension of the Indian summer monsoon. The regional shift in the maximum precipitation belt from northwest to southeast over the past 10,000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate. The southeastward shift of the East Asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the Holocene and the East Asian monsoon index declined, while the early maximum in southwestern China matches the maximum of the Indian monsoon index.
... The Gushantun (GST) peatland (42 18 0 22.1 00 N, 126 16 0 57.7 00 E, 506 m a.s.l) is located to the west of the Changbai Mountains in Longgang Volcanic Field. The peatland is surrounded by Cenozoic basalt, and it formed within the relatively low-lying platform area; the diameter of the peatland is~1000 m (Liu, 1989). We obtained peat sediment cores in the summer of 2009, using an Eijkelkamp peat sampler. ...
... These vegetation types are also recognized by pollen-based records which show that the GST region was also occupied by open mixed broadleaf-conifer forest. These results confirm that the GST region was not predominantly a tundra zone, contrary to suggestions based on pollen-analytical results for the GST peatland (Liu, 1989). In terms of vegetation composition, the phytolith data indicate that elements of Larix, other Pinaceae, and C3 grass plants, expanded in an open landscape; whereas based on pollen data, Picea, Betula and the understory taxa Artemisia and Cruciferae predominated. ...
... Indeed, Northeastern (NE) China is one of the most important peat distribution regions of the world (Chai, 1990). Up to now, several Holocene paleoclimate reconstructions have been carried out using peat deposits in the Changbai Mountains, and many proxies have been used as indicators to study Holocene environment change, including pollen (Liu, 1989;Xu et al., 1994;Xia and Wang, 2000;Makohonienko et al., 2004), phytolith (Zhang et al., 2007;Guo et al., 2012), stable isotopes (Hong et al., 2009(Hong et al., , 2010, testate amoebae (Li et al., 2009), chemical element (Zhang et al., 2011) and biomarkers (Zhou et al., 2010). However, the inorganic mineral composition of peat deposits has been overlooked, yet grain size is recognized as an important paleoenvironmental proxy in other depositional environments (Liu, 1985;Ding et al., 1998;Lu and An, 1998;Sun et al., 2003;Huang et al., 2011;Qiao et al., 2011). ...
... Artemisia values represent around 40%, indicating a dry and cold climate (Yu et al., 2008). Similarly, pollen data from marr lakes (Liu et al., 2008;Stebich et al., 2009) and other peatland cores (Liu, 1989) have shown the same dry/cold late-glacial paleoclimate pattern in NE China. It is mostly because the semi-arid climate and strong EAWM during the late-glacial period were conducive to aeolian transport that more C1 was taken into the peatland. ...
Peatlands provide a widespread terrestrial archive for Holocene study. However, little is known about the grain-size characteristics of peaty sediments and their environmental significance. In order to study these phenomena in detail, two sections from the Hani and Gushantun peatlands in the Changbai Mountain Area were cored and sub-sampled. Based on reliable calibrated AMS ¹⁴C ages, we established grain size variations in the peat cores since 15.6 ka cal. BP. Our results showed that the peaty sediments in the Changbai Mountains are mainly composed of silt. Moreover, the grain size component, which is related to paleoclimate variables, can be classified into three groups based on the “Grain size class vs. standard deviation” method. These sensitive grain size components are <37.0 μm (Component 1 or C1), 37.0–497.8 μm (Component 2 or C2) and >497.8 μm (Component 3 or C3). C1 comprises the finest silt in the peaty sediment and is mainly conveyed by the East Asian winter monsoon (EAWM), whereas C2 is transported into the peatland by surface runoff related to the enhancement of the East Asian summer monsoon (EASM). C3 is conveyed in saltation and bed-load mode by strong surface runoff linked to high-energy flow caused by a strong EASM, and perhaps is an indicator of extreme rainfall events in the Changbai Mountains. Our results suggest that the study region was dominated by a cold/dry environment during the late-glacial period under a strong EAWM. However, there was a marked climatic shift from an EAWM-dominated cold/dry climate to an EASM-dominated more mesic environment during the early Holocene. Increased percentage of C2 in peat cores during the Holocene Optimum (9.0–4.5 ka) indicates abundant rainfall in the study region (even with extreme rainfall events) as a result of a significant enhancement of the EASM. Weak monsoon events occurred at 10.5 ka, 9.2 ka, 8.2 ka, 7.2 ka, 6.2ka, 5.5 ka and 4.2 ka shown by sharp decreases in C2, agreeing with the stalagmite δ¹⁸O records in China. The results obtained from environmentally sensitive grain-size component records are largely consistent with other palaeoenvironmental records in the East Asian monsoon area, substantiating the regional climate patterns and monsoon evolution since late-glacial time. Because intensity of the East Asian monsoon is likely responsible for the grain-size change in the peat samples, the grain size components in peat samples may be used for reconstructions of past environmental conditions and of variability in the East Asian monsoon.
... Previous paleoclimate reconstructions for the Changbai Mountains have shown that the climate was warm from 9000 to 4000 a BP and became cooler from 4000 to 2300 a BP (Yuan and Sun, 1990;Liu, 1989) (Table 5). Our phytolith indices agree with the results of those reconstructions. ...
... Therefore, even based on the tree pollen percentage of Chen's record (1997), the climatic condition would be cool. In addition, Yuan and Sun (1990) and Liu (1989) found cooler climate between 4000 a BP and 2300 a BP. Nevertheless, the climate record reconstructed by our study agrees well with the previous results. ...
This study uses new herbaceous phytolith indices to reconstruct the paleoclimate in the Changbai Mountains, NE China. In this study, we collected 52 pairs of herbaceous quadrats and corresponding topsoils: 25 were from the understory (UND) and 7 were from the non-understory (NON) in the Changbai Mountains; whereas the other 20 were from the grassland (GRA) of Songnen Plain for comparing the forest area of the Changbai Mountains. The phytolith analyses of the 104 modern samples provide a guide of using herbaceous phytolith indices as paleoclimate reconstruction. The herbaceous quadrats of the Changbai Mountains contained more long-cell phytoliths and fewer short-cell phytoliths compared to the herbaceous quadrats of the Songnen grassland; and similar situations appeared in the corresponding topsoil phytoliths. The ratio of short cell% to long cell% (S/L) in the topsoil can be used to discriminate grassland (S/L > 1.65) and forest (<1.65), with discriminant accuracy of 80%. Furthermore, in the forest region, S/L in the topsoil is low for the non-understory (NON) (<0.46), and relatively high for the understory (UND) (0.46 < S/L < 1.65), probably due to preservation of short-cell phytoliths. The ratio of rondel% to lanceolate% (Ro/La) reflected the same trend as S/L for the forest region: Ro/La < 0.23 indicating NON, and Ro/La > 0.89 indicating UND. Thus, lower S/L and Ro/La ratios may reflect more development of NON in the forest region under relatively warm conditions, whereas higher S/L and Ro/La values indicate better development of UND with cold climates. These two indices (S/L and Ro/La) from a peat profile in the Changbai Mountains were further used to reconstruct the paleoclimate since 7670 a BP. The phytolith analyses of 33 peat samples from the 326-cm long core showed four ordinal clustering zones: Zone I (7670–4060 a BP) with low mean S/L (0.42) and Ro/La (0.78) was characterized as warm. In Zone II (4060–2580 a BP), S/L and Ro/La fluctuated around mean values of 0.47 and 3.40, respectively; indicating cooler climate than Zone I. Zone III (2580–640 a BP) was characterized by the highest mean values of S/L (0.53) and Ro/La (6.97) in the profile, reflecting the coldest condition in the record. In Zone IV (640 a BP–modern), the average values of S/L and Ro/La were 0.31 and 1.14, respectively. Both indices increased initially and then declined, perhaps reflecting the colder climate of the Little Ice Age, followed by a warming period. The climatic patterns of the Changbai Mountains reconstructed from the herbaceous phytolith indices agreed with the Ic index and pollen analysis from the same peat profile, suggesting that these new herbaceous phytolith indices should be applicable in paleoclimate reconstruction.
... This result is in good agreement with some previous studies from other areas, such as Mt. Changbaishan and Sanjiang Plain in NE China (Xia, 1988;Liu, 1989;Sun and Chen, 1991), Huabei Plain (Kong et al., 1992) and the middle-lower reaches of Yangtze River (Liu et al., 1992;Yi et al., 2003Yi et al., , 2006Shu et al., 2007;Chen et al., 2009;Wang et al., 2010). This stage is also in accordance with the Holocene maximum marine transgression in China Meng, 1984, 1985;Zhao et al., 1994). ...
... This result is in good agreement with some previous studies from other areas, such as Mt. Changbaishan in NE China (Liu, 1989) and Lake Jianhu in Jiangsu Province (Zhao et al., 1994). It is notable that the content of Chenopodiaceae reaches its maximum. ...
There is almost no detailed Holocene pollen data in Shandong Province. This paper reports a pollen record from a natural profile at Qingdao of Shandong Province, East China between 7250 and 3500 cal. BP, and provides new evidence for the collapse of Neolithic cultures around Central China in the middle Holocene. It reveals a subtropical deciduous and evergreen broad-leaved forest was well-developed during 7250–5900 cal. BP, representing the Holocene Maximum warm climate condition. During 5900–4550 cal. BP, pollen flora retained the main features of the former stage, but the contents for the major tree components in the flora decreased, implying an end of the Holocene Maximum warmth. From 4550 cal. BP to 3900 cal. BP, the percentage of AP (Arboreal Pollen) abruptly fell to the lowest value in the profile, inferring a distinct climate deterioration. During 3900–3500 cal. BP, a major recovery of AP is captured, indicating a possible climate change. The above mentioned climate changes are in good coherence with the local Neolithic Culture evolution. It is assumed that the cold climate during 4550–3900 cal. BP is possibly responsible for the collapse of the Longshan Culture in Shandong Province.
... Similar dates of ca. 4220-4070 BP for pine expansion in the region have been obtained from Gushantun bog (Liu, 1989;Sun et al., 1991). Pine expansion in the Changbai Mountains region has been interpreted as a response to climatic cooling dated between 5000 and 4000 BP by different authors (Liu, 1989;Sun et al., 1991;Ren and Zhang, 1998). ...
... 4220-4070 BP for pine expansion in the region have been obtained from Gushantun bog (Liu, 1989;Sun et al., 1991). Pine expansion in the Changbai Mountains region has been interpreted as a response to climatic cooling dated between 5000 and 4000 BP by different authors (Liu, 1989;Sun et al., 1991;Ren and Zhang, 1998). The initialisation of peat growth on the sites in Manchurian Plain and mid-Holocene spread of mixed forests with Korean pine in Changbai Mts. may have had a common climatic background. ...
Two peat profiles from the Manchurian Plain in northeastern China, with chronology based on 20 AMS measurements, provide new evidence for natural and anthropogenic environmental changes that occurred in the region during late Holocene. The onset of continuous organic accumulation interpreted as climatically induced shift in hydrological regime was dated at the Muchang site to 4200 (uncal.) BP, and at the Dahuofang site to at least 3560 BP. The start of peat growth, documented in the Muchang profile, was preceded by temporal intensification of fluvial processes around 4400/4300 BP. The evidence of hydrological changes in the Manchurian Plain correlates with the spread of Korean pine in the nearby Changbai mts. area in 4300–4000 BP, and can be associated with the initial stages of a trend towards present-day climatic conditions in the region.Late Holocene pollen sequences from Muchang and Dahuofang revealed the presence of oak and pine forests with the other minor deciduous constituents as Ulmus, Tilia, Carpinus, Acer and Fraxinus. Local distribution of oak was confirmed by plant macrofossil remains (leaf fragments) ascribed to Quercus x hopeiensis. The vegetation cover formed sparse woodland or mosaic of forests and steppe communities with Artemisia, Gramineae and Chenopodiaceae. Fossil pollen data clearly indicates that the spread of grasslands in the western part of Manchurian Plain occurred as a result of human impact. Extensive deforestation accompanied by agricultural practices (buckwheat cultivation) has been dated to 900–1100cal yr AD and were correlated with development of the state of Liao dynasty (907–1125 AD). Evidence of earlier human involvement in forest destruction has been dated to around 900cal yr BC. With each progressing anthropogenic deforestations phase, there was increased circulation of eolian dust resulting from landscape opening and soil erosion.
... The first researcher to deal with the Holocene climate in China using archaeological evidence was Zhu (1972), who indicated that the mean annual temperature in the Yellow River basin between 5000 and 3100 yr ago was 2jC higher than that of the present, and that the winter temperature was 3 -5jC higher. Later work on vegetation changes in relation to Holocene climatic variations in different parts of China ( Fig. 1) was reported by Chen et al. (1977) from southern Liaoning province, Kong et al. (1982) from the Beijing region, Zhou et al. (1990) from northern China, Li and Liang (1985) from eastern Hebei province, Liu (1989) from Mt. Changbai, northeastern China, Kong et al. (1990) from Qinghai Lake, Tang and Shen (1992) from northern Jiangsu province, Van Campo et al. (1996) from the Bangong lake basin, western Tibet, Liu et al. (1998) from the Dunde ice cap, Mt. Qilian, and Tang and Li (2001) from the Tibetan plateau. ...
... The data sets from nine sampling sites in eastern and central parts of China ( Fig. 1) display qualitative climatic variations, at time scales of hundreds to thousands of years (Fig. 2). The data sequences were recovered and analyzed by Wang et al. (1990) from Mt. Luojie (Fig. 2a), Kong et al. (1990) from Qinghai Lake (Fig. 2b), Cui and Kong (1992) from Baisuhai, Inner Mongolia (Fig. 2c), Sun and Zhao (1991) from the central part of the loess plateau (Fig. 2d, a combination of four sampling sites on the plateau, Xi'an, Lantian, Fuping, and Yulin), Zhang et al. (1981) from Beijing (Fig. 2e), Li and Liang (1985) from eastern Hebei (Fig. 2f), Chen et al. (1977) from southern Liaoning (Fig. 2g), Liu (1989) from Mt. Changbai (Fig. 2h), and Tang and Shen (1992) from Qingfeng (Fig. 2i). ...
A review of Holocene climatic variations in different parts of China shows that they were asynchronous. Proxy data from ice cores, pollen, loess, lacustrine sediments, and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in China during the Holocene, including a most important climatic event known as the “Holocene optimum,” a milder and wetter period, and that the duration and amplitude of the optimum period, as well as its start and end times, differed in different parts of China. Uplift of the Tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental China during the Holocene. As a result, the Holocene optimum began and terminated earlier in high-altitude regions of western China than at lower elevations in eastern China, and the amplitude of the variations was lower in the east. This suggests that the western higher-altitude areas were more sensitive to climatic change than were the eastern lower-altitude areas. Holocene climatic records in the Dunde and Guliya ice cores do not correspond. Inverse δ18O variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed. The correlation between the isotopic composition of carbonates in lake deposits in western China and climatic variations is similar to that in the ice cores. The climatic resolution in ice cores and lake sediments is higher than that in other media. The lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of China is a result of the different locations and elevations of the sampling sites, the different resolutions of the source material, and the varied climatic conditions within China. Further work is needed to confirm both the conclusions and the inferences presented here.
... The early to mid-Holocene vegetation pattern from this work is consistent with those of previous studies (Liu, 1989;Yuan and Sun, 1990;Sun et al., 1991;Makohonienko et al., 2001) (Fig. 1B), suggesting that the vegetation changes were of a regional nature. Meteorological data from northern China (Domrös and Peng, 1988) indicate that precipitation and temperature are key factors responsible for the spatial differentiation of modern vegetation (Editorial Board for Flora of China, 1995;Hou, 2001) (Fig. 1A). ...
... AD 1100 and 1200 recorded in Lake Teletskoye were related to arid climate conditions (Andreev et al., 2007). Pollen assemblages of this study and other records indicate a progressive change from a wet and warm climate in the early Holocene to a drier and colder climate in the mid-Holocene (Liu, 1989;Yuan and Sun, 1990 Liu, 2007). Therefore a shift toward a drier climate during the mid-Holocene could trigger the burning of peatlands and their surroundings. ...
Pollen and charcoal particles from a Jinchuan peat (northeastern China) were examined to investigate the fire origin and interaction between climate, vegetation, fire and human activity during the Holocene. Pollen results show that: (i) a broadleaved deciduous forest was dominant during the early Holocene; (ii) from ~ 5500 cal. yr B.P. there was a gradual increase in coniferous trees (mainly Pinus), and a decrease in broadleaved deciduous trees (e.g. Quercus, Juglans, and Ulmus–Zelkova); (iii) after ~ 4200 cal. yr B.P., the deciduous forest was replaced by a mixed forest of coniferous and deciduous trees; (iv) coniferous trees including Pinus, Abies and Picea further increased after ~ 2000 cal. yr B.P., reflecting a cooler and drier climate after ~ 5500–4200 cal. yr B.P. Two layers of abundant microfossil charcoal particles (250–10 μm) and the coexistence of macrofossil particles (> 2 mm) suggest two local fires: fire event 1 (5120 ± 66 cal. yr B.P.) and fire event 2 (1288 ± 8 cal. yr B.P., AD 662 ± 8). Charcoal layer 1, with a large amount of Monolete psilate spores, is superimposed on the long-term trend of vegetation changes, indicating a natural origin for fire event 1 that was probably facilitated by drying environmental conditions since the mid-Holocene. Cerealia-type pollen and a low percentage of Monolete psilate spores were observed in charcoal layer 2, indicating that fire event 2 was caused by clearing. We suggest that fire event 2 may be related to the spread of the Han farming culture accompanied by the territorial expansion of the Tang Dynasty to the studied area in AD 668.
... The vegetation changes for the Changbai Mountain region in eastern Manchuria have been previously studied by Liu (1989), Mingram et al. (2004a, b), , Sun and Yuan (1990), Sun and Weng (1992), and Yuan and Sun (1990). The longest sequences covering the Late Glacial and the Holocene were presented from Gushantun and Jinchuan sites (Liu, 1989;, subsequently used for the regional synthesis in China (Sun and Chen, 1991;Ren and Zhang, 1998;Yu et al., 2000;Ren and Beug, 2002). ...
... The vegetation changes for the Changbai Mountain region in eastern Manchuria have been previously studied by Liu (1989), Mingram et al. (2004a, b), , Sun and Yuan (1990), Sun and Weng (1992), and Yuan and Sun (1990). The longest sequences covering the Late Glacial and the Holocene were presented from Gushantun and Jinchuan sites (Liu, 1989;, subsequently used for the regional synthesis in China (Sun and Chen, 1991;Ren and Zhang, 1998;Yu et al., 2000;Ren and Beug, 2002). These studies, however, concentrated on main vegetation changes, forest taxa and selected herbaceous components with restricted analyses of anthropogenic factors. ...
Pollen analytical data from Jinchuan site in the Changbai Mountains, located within the mixed temperate broadleaved forest zone of Northeast China, were used for the reconstruction of vegetation changes and dynamics of human habitation activities in the last 6000 cal. years in the periphery to the Chinese civilization areas of former Manchuria. The beginning of the present type of vegetation dominated by mixed forests with the characteristic tree species Korean pine (Pinus koraiensis Siebold & Zuccarini) was dated to 3100 cal. BC. Expansion of Korean pine occurred in two steps. The second phase of enhanced expansion of pine along with other coniferous taxa of higher altitudes such as Abies and Picea was dated to around 70 AD. The pattern of Late Holocene spread of coniferous elements (P. koraiensis, Picea, Abies) and retreat of deciduous oaks was associated with phases of climatic cooling and presumably changes in effective precipitation.The oldest record of habitation processes identified in pollen assemblages from Jinchuan was dated to around 140 AD. The buckwheat (Fagopyrum esculentum) cultivation was documented since the first half of the 9th century AD. The 18th century immigration of the Chinese population of Han ethnicity was reflected in the fossil archive, due to economic activities of the settlers connected with exploitation of forest resources through cutting of pine trees, protection of walnut stands, and cultivation of Hordeum/Triticum cereals.
... A negative correlation is significant at the 99% level, indicating that the initial forest decline occurred progressively later with distance from the core region. Exceptions are Longquanhu (site 17 on Fig. 1 Fig. 1 and Table 1) (Liu, 1989), the change appeared around 1000 yr BP. However, no long-term downward trend in AP percentages could be detected in the northernmost parts of Northeast China during the last 6000 yr. ...
... Xia et al., 1993; (4) Chen et al., 1977; (5) Xu et al., 1988; (6) Xu et al., 1993; (7)Zhao, 1992; (8) Ciu et al., 1993; (9) Sun et al., 1991; (10) Wang et al., 1991; (11) Du et al., 1989; (12) Wang, 1987; (13) Jarvis, 1993; (14) Tang and Shen, 1992; (15) Liu, 1991; (16) Sun et al., 1993; (17) Liu, 1989; (18) Zhao,, 1989. ...
Fossil pollen data from China indicate continued forest decline during the mid- to late Holocene in most regions north of the Yangtze River. The earliest forest decline can be detected ca. 5000 yr BP in the middle and lower Yellow River regions. North, northeast and northwest from this region, forest decline became progressively later, and almost no decline took place in the northernmost part of northeast China and in the remote areas of west China during the last 5000 yr. Climate changes could hardly account for the temporal and spatial patterns of the forest decline. Instead, anthropogenic disturbance may have been of overwhelming importance. Ancient agriculture and high-density settlement expanded outward from the middle and lower Yellow River regions in similar patterns to those of forest change. This study also indicates that land-use and land-cover changes may have started in the early stage of Chinese civilization in an extensive area of the country.
... The 4.2-kyr event: About 4600 cal aB.P., the humidity-aridity index (Iph) significantly increased, while the warmth index (Iw) sharply decreased, indicating rapid cooling and aridity; a sudden reduction in LOI 550 verified this phenomenon. This cooling event was recorded at 4.0 ka B.P. in the Gushantun Bog [109], 3.9 ka B.P. in the Jinchuan peat bog [110], and 4.11 ka B.P. in the Erlongwan maar lake [111], as well as in North America, Africa, the Middle East, and India [112]. It might mark the end of the Mid-Holocene and the beginning of the Late Holocene in the central Songnen Plain, Northeast China. ...
Identification of paleoclimate oscillation from various climate proxies across different regions is important for the mechanistic research of paleoclimate. Phytoliths from the lacustrine sediment of central NE China were extracted for paleoclimate reconstruction and abrupt event recognition. The combined phytolith assemblages; indices of Iw, Iph, D/P, Pi/P, and T/P; and the 66.4% PCA information with 95% confidence ellipse showed six global synchronously paleo-stages in the past 25,000 years: mixed coniferous broadleaf forest in a semi-humid cool climate (25,165–22,180 cal aB.P.), cold and arid steppe (22,180–18,080 cal aB.P.), semi-humid and semi-arid steppe (18,080–11,380); semi-humid cool grassland (11,380–7790 cal aB.P.), humid warm forest steppe (7790–4300 cal aB.P.), and semi-arid and cool meadow steppe (4300 cal aB.P. to the present). The global abrupt events of the 4.2-kiloyear event, 8.2-kiloyear event, Younger Dryas (YD), Heinrich1 (H1), and Heinrich2 (H2) were also captured by phytolith indices. The regional character of the reduction in humidity of the YD might have been affected by the combined influence of the Okhotsk High and the surrounding mountains. These findings not only strengthen phytolith palaeoresearch but also provide basic information for the mechanistic research of palaeoclimate in the edge area of Northeast Asia and promote global climate change research.
... The peatland is nearly circular in shape with a diameter of~1000 m and is surrounded by Cenozoic basalt of the Longgang volcanic group. The peatland has an average thickness of~7 m and provides a sedimentary record dating back to ca 13,000 years before present (Liu, 1989;Li et al., 2017). The GST peatland is surrounded by temperate mixed conifer-hardwood forests, which are dominated by Pinus koraiensis and Quercus mongolica, together with some other broadleaved deciduous species such as Carpinus cordata, Phellodendron amurense, Acer pictum subsp. ...
Ongoing climate changes have a direct impact on forest growth; they also affect natural fire regimes, with further implications for forest composition. Understanding of how these will affect forests on decadal-to-centennial timescales is limited. Here we use reconstructions of past vegetation, fire regimes and climate during the Holocene to examine the relative importance of changes in climate and fire regimes for the abundance of key tree species in northeastern China. We reconstructed vegetation changes and fire regimes based on pollen and charcoal records from Gushantun peatland. We then used generalized linear modelling to investigate the impact of reconstructed changes in summer temperature, annual precipitation, background levels of fire, fire frequency and fire magnitude to identify the drivers of decadal-to-centennial changes in forest openness and composition. Changes in climate and fire regimes have independent impacts on the abundance of the key tree taxa. Climate variables are generally more important than fire variables in determining the abundance of individual taxa. Precipitation is the only determinant of forest openness, but summer temperature is more important than precipitation for individual tree taxa with warmer summers causing a decrease in cold-tolerant conifers and an increase in warmth-demanding broadleaved trees. Both background level and fire frequency have negative relationships with the abundance of most tree taxa; only Pinus increases as fire frequency increases. The magnitude of individual fires does not have a significant impact on species abundance on this timescale. Both climate and fire regime characteristics must be considered to understand changes in forest composition on the decadal-to-centennial timescale. There are differences, both in sign and magnitude, in the response of individual tree species to individual drivers.
... For example, Changbai Mountains contain nearly 92.162 km 2 in area with 38.92 million tons of peat storage (Chen, 2000). Previous studies on peat sequences in Northeastern China for paleoclimate and paleoenvironment were mainly carried out in a few mires, including Hani Mire (Hong et al., 2005(Hong et al., , 2010, Jinchuan Mire (Hong et al., 2000Makohinienko et al., 2008), Gushantun Mire (Liu, 1989) and Hanlongwan Mire (Fu, 2006) in Changbai Mountains, Motianling bog in Great Hinggan (Zhang et al., 2014), and Shen Jiadian (SJD) peatland in the Sanjiang Plain . Most of these records used stable isotopes (cellulose δ 18 O and δ 13 C) and lipid biomarkers (n-Alkane concentration and distributions) as major proxies for paleoclimate reconstructions. ...
A 1.8 m long core was retreated from Baijianghe mire in the west flank of Changbai Mountains of China in 2016. The peat sequence was dated by AMS ¹⁴ C and ²¹⁰ Pb/ ¹³⁷ Cs methods, showing a 1600-y depositional history. Based on the measured porosity, dry bulk density (DBD), TOC%, absorbance and plant macrofossil, we discuss the mire development and environmental change during the last 1600 years. The basin of Baijianghe Mire was a water-logged bottomland between 330 and 660 CE. A strong drought occurred during 530–600 CE caused lowering of water table which provided hydrological condition to form a peatland. Wet climate during 660–800 CE led to enhanced primary productivity and accumulation of plant remains, resulting rapidly development of the mire. Warm but fluctuating wetness conditions during the Medieval Warm Period (MWP, 900–1150 CE) in the study area kept moderate development of the mire. Baijianghe Mire had the fastest development during 1200–1370 CE under relatively wetter and probably warm conditions. Low carbon accumulation of the mire appeared during the Little Ice Age (LIA, 1500–1850 CE) under cold and dry climates. From 1850 CE to 1945 CE, the climate turned to warm and wet. However, the peatland had experienced strong influence by human activity since 1945 CE. The peatland has gradually recovered from artificial drain since 1990s.
... Among the indicators listed above, pollen is the most widely used indicator in Quaternary research. In NE China, pollen-based paleoenvironmental studies are mainly conducted on peat deposits in forest regions (Liu, 1989;Yuan and Sun, 1990;Ren, 1999;Li et al., 2005a;Schettler et al., 2006;Liu et al., 2008;Chu et al., 2009;Stebich et al., 2015;Xu et al., 2014). This is partly because pollen is typically well preserved in peats and peatland development is promoted under the moist and cool-cold temperature conditions in the forested region of NE China. ...
... The sediment sequences hold a detailed record of terrestrial vegetation characteristics and sea level fluctuation (Milliman and Meade, 1983;Hanebuth et al., 2000;Coe et al., 2003). Sediment characteristics and micropaleontological floral and faunal distributions may directly or indirectly respond to climate variation (Liu, 1989a;Berglund, 2003;Dobrzanska et al., 2004). Therefore, the study of the sediment on the continental shelf can help us to understand changes in the environment and climate, and provide a basic reference for regional or global climate change (Yi et al., 2012;Yao et al., 2014). ...
... Consequently, the majority of these studies are inadequate to trace abrupt climatic events as well as changes in vegetation. Moreover, because most pollen records do not extend back to the last Pleniglacial, there are few reliable reconstructions of the floral history in this region during the Last Glacial period (liu 1988, liu et al. 1989, Yu et al. 2000, hong et al. 2005. ...
High-resolution palynological, sedimentological and geochemical studies are being undertaken on a varved sediment sequence from the Sihailongwan maar lake, Jilin Province, aimed at reconstructing the vegetational development and climatic history of Northeastern China since the last glaciation. The most recent pollen diagram from Sihailongwan Lake represents the upper 17 m of a total annually laminated sedimentary sequence of 38 in, which has been sampled at a resolution of 10 cm. It illustrates the main vegetational features of the studied region during approximately the last 37,000 years. A high-resolution timescale for the palynological data set has been provided by both AXIS 14C age determinations and varve counting. The lowermost pollen samples indicate steppe and open woodland communities with abundant Artemisia, grasses and sedges, which are typical for glacial conditions. Moreover, some of the pollen spectra, predominantly those from the Last Glacial Maximum, exhibit distinct fluctuations in Picea, Larix and Artemisia, which closely correlate with abrupt changes in varve thickness. These appear to indicate millennial-scale climatic fluctuations during the Pleniglacial in Northeast China. The climatic amelioration following the Last Glacial Maximum is reflected in the pollen record by a gradual increase in arboreal taxa. During the Late-glacial, Ulmus and Fraximus spread out again in this region. The prominent reappearance of Picea and Larix, coupled with a marked decrease in Ulmus and Fraxinus, immediately prior to the start of the Holocene, implies a climatic reversal compatible with the Younger Dryas event in Europe. The pollen diagram indicates the dominance of deciduous forest during the Early Holocene, followed by an expansion in pine about 5,200 years ago. In this remote area, human impact signals are sparse and are restricted to the last few centuries. © E. Schweizerbart'sche Verlagsbuchhandlung (Nägele u. Obermiller), 2007.
... The cooling event at ∼7300 cal yr BP, which resulted in a vegetation succession from mixed coniferous and broadleaved forest to forest-steppe, also appears in pollen records from Moon Lake in the central GKR [31] and the Buguldeika Core from Baikal Lake [83]. The cooling event at ∼4500 cal yr BP, which may have global parallels, appears in the pollen records from Erlongwan Maar Lake [84], the Gushantun Bog in Jilin [85], and Hokkaido in Japan [86]. Vegetation shows a succession from forest-steppe to steppewoodland. ...
Pollen samples from peat sediments on the south bank of the Heilongjiang River in northern Northeast China (NE China) were analyzed to reconstruct the historical response of vegetation to climate change since 7800 cal yr BP. Vegetation was found to have experienced five successions from cold-temperate mixed coniferous and broadleaved forest to forest-steppe, steppe-woodland, steppe, and finally meadow-woodland. From 7800 to 7300 cal yr BP, the study area was warmer than present, and
Betula, Larix
, and
Picea
-dominated mixed coniferous and broadleaved forests thrived. Two cooling events at 7300 cal yr BP and 4500 cal yr BP led to a decrease in
Betula
and other broadleaved forests, whereas herbs of Poaceae expanded, leading to forest-steppe and then steppe-woodland environments. After 2500 cal yr BP, reduced temperatures and a decrease in evaporation rates are likely to have resulted in permafrost expansion and surface ponding, with meadow and isolated coniferous forests developing a resistance to the cold-wet environment. The Holocene warm period in NE China (7800–7300 cal yr BP) could have resulted in a strengthening of precipitation in northernmost NE China and encouraged the development of broadleaved forests.
... However, most studies of the Holocene climate history of China have employed a single proxy indicator (e.g. Liu 1989;Shi et al. 1992;Wu et al. 1994;An et al. 2000;Zhou et al. 2002), so this time-transgressive behavior is not always clearly observed in some records. The conclusions from these studies have presented a controversial picture of the post-glacial evolution of regional climate. ...
We have carried out a multiproxy analysis of high-resolution eutrophic peat/mud, sand dune, and loess/paleo- sol sequences covering the Holocene period in both southern and northern China, in order to test the hypothesis of a time- transgressive Holocene optimum in the East Asian monsoon area (An et al. 2000). Samples were radiocarbon dated to estab- lish the chronology. Our results indicate that the Holocene optimum occurred between ~10,000-5000 cal yr ago in both south- ern and northern China, consistent with a global pattern rather than simply a local expression. Our data also support the conclusion that the evolution of Holocene climate in China is consistent with changes in Northern Hemisphere solar radiation.
... BP, triggered by an associated climatic shift. The steady increases in Ulmus (from that time on) and Fraxinus (starting about 200 years later) imply an earlier reexpansion of (cool-) temperate tree taxa within the study region than formerly suggested (Liu, 1989;. These previous studies date the expansion of Ulmus and Fraxinus some time after 11,000 radiocarbon years before present (about 12,900 cal yrs. ...
The results presented here from the annually laminated sedimentary sequence of Sihailongwan lake provide the first comprehensive palaeoecological record covering the Late Pleniglacial to the Early Holocene (16,700–10,600 cal yrs. BP) from Northeast China. High-resolution pollen analyses have enabled the vegetational and climatic changes of the last glacial-interglacial transition to be reconstructed in more detail than has been previously possible. Moreover, a reliable chronology has been provided by both varve counting and 40 calibrated AMS 14C age determinations.Palaeobotanical evidence indicates predominantly steppe and open taiga-like woodland communities, with abundant Betula, Larix, Alnus fruticosa, Artemisia, grasses and sedges, which are typical of cold and dry conditions between 16,700 and 14,450 cal yrs. BP. The beginning expansion of Ulmus and Fraxinus marks the onset of the Late-glacial climatic amelioration at 14,450 cal yrs. BP. Dense deciduous forests, predominantly consisting of thermophilous broadleaf taxa, become established and widespread during the Early Holocene.Two short-term climatic reversals to colder and/or dryer conditions are recorded in the proxy data between 13,900 and 13,800 cal yrs. BP and 13,100 and 12,900 cal yrs. BP, correlating with the Oldest Dryas/Greenland Interstadial (GI) 1d event and the Gerzensee/Killarney/GI-1b oscillation, respectively. The prominent reappearance of Picea and Larix, coupled with a marked decrease in broadleaved trees, prior to the start of the Holocene, implies a climatic reversal compatible with the Younger Dryas event in the circum-Atlantic region. The evident synchroneity of climate changes in the North Atlantic region and East Asia supports the theory of strong atmospheric coupling between both regions.
... An et al. (2006) defined the Holocene optimum as an effective moisture maximum. In eastern China, the Holocene optimum, as recorded by the pollen data (Chen et al., 1977;Zhang et al., 1981;Li and Liang, 1985;Liu, 1989), started 8500-7500 BP and terminated 4000-3000 BP, although it should be noted that these trends might lag a few hundreds years behind the occurrence of actual climatic change (He et al., 2004). The Holocene optimums of the Korean west coast and east China are much alike in occurring period. ...
Organic and inorganic geochemical and mineralogical analyses from core CL4 drilled in the Cheollipo wetland were carried out to investigate the Holocene Climatic Optimum, the formation of pyrite, and the humidity of the Korean western coast during the Holocene time. Lithostratigraphy, mineralogy, major element concentrations and organic contents of the sediments of the CL4 borehole core indicate that the Holocene Climatic Optimum occurred from about 7400 to 4500 BP, and that pyrite formed in brackish water tidal flat or salt marsh at least during 7400–6400 BP. In addition, sediments coarser in mean grain size and larger in standard deviation corresponded with periods of 8500, 5400, 5000 and 1700 BP. During the periods, the coarse sediments seem to have been delivered by high energy storm events. The periods partially overlap with those of high ratios of Si/Al, Na/Al and Na/Ti. These phenomena indicate that the weakly weathered terrigenous sediments were delivered to the Cheollipo borehole core site by storm events.
... This sluggish response of the polar front would have hampered the northward advance of the summer monsoonal front, which today provides most of the summer precipitation to Japan, and suppressed precipitation over the north-central part of Honshu Island during the Holocene. This hypothesis is consistent with both lake (Wang & Ji et al. 1995) and swamp (Liu 1989) records in northeastern China that indicate a dry episode between 10.3 and 8.3 ka BP. Accordingly, we suggest that the longer persistence and slower northward migration of the polar front in the North Pacific in the Holocene would have hindered the northward shift of the summer monsoonal front, and thereby suppressed monsoonal precipitations over northeastern Asia during the Holocene. ...
Xiao, J. L., Inouchi, Y., Kumai, H., Yoshikawa, S., Kondo, Y. & Takahashi, K. 2004 (February): Precipitation history of the Lake Biwa area in central Japan over the last 145 ka. Boreas, Vol. 33, pp. 74–81. Oslo. ISSN 0300–9483.
The fluvial quartz flux (FQF, g cm-2 ka-1) to Lake Biwa of central Japan is developed as a proxy of variations in palaeoprecipitation over the lake catchment. Lake Biwa sediments spanning the last c. 145 ka are characterized by 4 main intervals when the FQF values were significantly greater than 2 g cm-2 ka-1, and 5 main periods during which FQF values were lower. Three of the intervals with high FQF values occur from c. 128 to 78 ka BP, with peak values at c. 122, 101 and 82 ka BP; the fourth of two narrow peaks exists between c. 48 and 35 ka BP. Three main periods with lower FQF values intervene between intervals of high FQF values, and two others lie before c. 128 ka BP and after c. 35 ka BP. The data imply that palaeoprecipitation over the lake catchment increased during the intervals of high FQF values, and decreased during the periods of lower FQF values. High FQF values between c. 48 and 35 ka BP are interpreted to reflect an effective runoff of meltwater from the surrounding mountains during the interstade of the last glaciation. Relatively low FQF values during the early Holocene are interpreted to reveal a sluggish northward retreat of the polar front in the North Pacific Ocean that suppressed the northward advance of the summer monsoonal front and regional precipitation. During the last interglaciation, the increasing trend of FQF values is interpreted to indicate a progressive expansion of the Sea of Japan related to the rise in global sea level, which increased moisture advection to, and precipitation within, the Lake Biwa region.
... In the forests, trees were relatively sparse because the pollen accumulation rate remained low (Sun and Yuan, 1990;Yaun and Sun, 1990;Liu, 1989). Shrub Betula populations might have been large at least in the north (Xia, 1988;Xia, pers. ...
Maps of pollen data have long been unavailable for continental Asia despite their importance for paleoecological and paleoclimatic studies. Pollen data from 65 Holocene sites have allowed the mapping of eight pollen taxa and seven time slices for Northeast China. These pollen maps show significant vegetation changes during the last 10,000 years in the current forest regions of Northeast China, with the early Holocene characterized by widely distributed Betula trees, the mid-Holocene by the development of temperate deciduous forest mainly consisting of Quercus and Ulmus trees, and the late Holocene by the marked increase in the abundance of Pinus trees and the development of temperate mixed conifer and deciduous forest. An unexpected finding from the pollen mapping research is the south-to-north propagation of the mid-to-late-Holocene forest decline, which may have been caused by the persistent human activities and the gradually northward expansion of agriculture during the last 5000 years. It is thus evident that caution has to be taken when reconstructing the mid-to-late-Holocene climates from pollen records in some regions of Northeast China. The classic paleoclimate reconstruction for the southern part of the study area and possibly for North and Northwest China needs to be re-evaluated.
... Consequently, the majority of these studies are inadequate to trace abrupt climatic events as well as changes in vegetation. Moreover, because most pollen records do not extend back to the last Pleniglacial, there are few reliable reconstructions of the floral history in this region during the Last Glacial period (liu 1988, liu et al. 1989, Yu et al. 2000, hong et al. 2005. ...
Total organic carbon (TOC) content, total nitrogen (TN) content, stable nitrogen isotope (δ15N) and stable organic carbon isotope (δ13Corg) ratios were continuously analysed on a high resolution sediment profile from Lake Sihailongwan (SHL), covering the time
span between 16,500 and 9,500years BP. Strong variations of the investigated proxy parameters are attributed to great climatic
fluctuations during the investigated time period. Variations in organic carbon isotope ratios and the ratio of TOC/TN (C/N
ratio) are discussed with respect to changing proportions of different organic matter (OM) sources to bulk sedimentary OM.
Phases of high TOC content, high TN content, depleted δ13Corg values and high δ15N values are interpreted as times with increased productivity of lacustrine algae in relation to input of terrigenous organic
matter. Two distinct phases of enriched nitrogen isotope ratios from 14,200 to 13,700 and 11,550 to 11,050years BP point
towards a reduced phytoplankton discrimination against 15N due to a diminished dissolved inorganic nitrogen pool. The combination of geochemical (TOC, TN, C/N ratio) and isotopic
(δ13Corg, δ15N) proxy parameters points to a division of climate development into four stages. A cold and dry stage before 14,200years
BP, a warm optimum stage with high phytoplankton productivity from 14,200 to 12,450 BP, a colder and drier stage from 12,450
to 11,600 BP and a stage of climatic amelioration with high variability in TOC and TN contents after 11,600 BP. These results
are discussed in relation to monsoon variability and Northern Hemisphere climate development of the late glacial.
... Three pollen records from peat profiles (Jinchuan: site D1, Jiang et al., 2008; Qindeli Bog: site D3, Xia, 1988; Gushantun Bog: site D2, Liu, 1989) in the mixed conifer-hardwood forest of northeast China span the entire Holocene. Pollen record at ca. 280-year resolution from Qindeli shows that from 12.5 to 10 ka broadleaved trees, including Betula, dominated the vegetation (Fig. 3F). ...
Fossil pollen records from 31 sites with reliable chronologies and high-resolution data in the monsoonal region of China were synthesized to document Holocene vegetation and climate change and to understand the large-scale controls on these changes. The reconstruction of moisture histories was based on a four-class ordinal wetness index at 200-year time slices at individual sites. The vegetation experienced diverse changes over the Holocene in different regions: (1) between tropical seasonal rain forest and more open forest in tropical seasonal rain forest region; (2) from mixed evergreen and deciduous broadleaved forest to more deciduous or Pinus-dominated forest in subtropical region; (3) from mixed evergreen and deciduous broadleaved forest to deciduous forest in temperate deciduous forest region; (4) from deciduous broadleaved forest to conifer–deciduous forest in conifer–deciduous mixed forest region; (5) from steppe forest to steppe in temperate steppe region; and (6) from steppe forest/meadow to meadow/steppe in highland meadow/steppe region. Despite various vegetation sequences in different regions, our synthesis results show that a humid climate generally characterized the early and middle Holocene, and a drier climate prevailed during the late Holocene, with an abrupt shift at ca. 4.5 ka (1 ka = 1000 cal yr BP). Abrupt palynological changes based on a squared-chord distance of pollen assemblages occurred at 11–10, 6–5 and 2–1 ka from most sites. The synthesized pattern of moisture change is similar to the ones inferred from other independent climate proxies; however, gradual vegetation changes in the early Holocene lagged about 1000 yr behind the summer monsoon maximum as indicated by speleothem isotope records from Dongge and Sanbao caves. Human activities likely affected vegetation change greatly during the late Holocene, but the magnitude and precise timing are less clear and require further investigation.
... Most studies of the late glacial to Holocene climate history of China have employed a single proxy indicator (e.g., Liu, 1989;Shi et al., 1992;Wu et al., 1994;An et al., 1990An et al., , 2000Zhou et al., 2002). The conclusions from these studies have presented a complicated picture of post glacial evolution of regional climate. ...
We have carried out a multi-proxy analysis of a radiocarbon-dated peat core that records the history of paleoclimate change dating from 18 ka in the Dingnan region of southern China. Fatty acid and hydrocarbon distributions, total organic carbon (TOC) concentrations, pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals. Plant waxes are the predominant origin of the n-alkanoic acid and n-alkane compositions of this sedimentary sequence. Contributions of these geolipid components vary relative to TOC and with changes in lithology and help to refine a pollen-based reconstruction of local paleoclimate evolution. A period of cool and fairly wet climate (15,630–10,450 cal aBP) follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions. The second period (10,450–6040 cal aBP) experienced the warmest climate and the highest precipitation, indicated by a minimum C18:1/C18:0 ratio, together with the low CPI values of n-alkanes and high ACL values. The third time interval (6040–3800 cal aBP) was a moderately dry and cool period. The climate record of the most recent period (<3800 cal aBP) is obscured by agricultural disturbance. The Younger Dryas (12,900–11,600 cal aBP) appears in this record as a period of variable and very wet climate. During the interval 10,450–6040 cal aBP, both temperature and the precipitation/evaporation ratio maximized. Therefore, we consider this period to represent the Holocene Optimum which coincides with that of the northern hemisphere. Moreover, our results do not fit the spatially asynchronous pattern of the East Asian monsoon Holocene Optimum in China suggested by previous studies. They instead parallel the pattern of global paleoclimate change and consequently show that the evolution of Holocene paleoclimate in southern China is consistent with changes in northern hemisphere solar radiation.
... Peat bogs are extensively distributed in northeast China. Some have been studied for the cimate-influenced Holocene evolution of biological environments (Liu, 1989;Hong et al., 2001Hong et al., , 2003. These and other studies confirm that northeast China has been sensitive to postglacial climate changes (Zhou et al., 2001;Jiang et al., 2006). ...
Based on paleoclimatic reconstructions using various proxies, the Holocene Climate Optimum (10.5–6 ka) has been characterized as a warmer and wetter period in most of East Asia. The summer monsoons associated with the East Asian Monsoon evidently intensified and extended further inland from the Pacific Ocean, a source region of moisture. A notable exception to this general pattern exists in northeast China, where less wet conditions are recorded. We determined molecular compositions of individual plant wax hydrocarbons and their hydrogen isotope compositions (δD values) in a radiocarbon-dated peat core recovered from the Hani marsh in Jilin Province (China) and confirmed that the temperature-dependent effective precipitation in northeast China decreased during the Holocene Climate Optimum. A combination of Paq, an indicator of the relative contribution of aquatic to terrestrial plants, and the difference in δD between low (C23, C25 and C27) and high molecular weight (C31) n-alkanes in the Hani peat bog indicates a dramatic change in vegetation from the deglaciation to the Holocene. No significant differences were observed between the δD values of low and high molecular weight n-alkanes with relatively high δD values and low Paq during the early Holocene, indicating that all n-alkanes were produced by evapotranspiration-sensitive terrestrial plants during that time. However, lower δD values of mid-chain n-alkanes (C23, C25 and C27) relative to the long chain n-alkane (C31), together with higher Paq values during the deglaciation (14–11 ka), suggest an increase in the contribution of aquatic plants and a higher water level during the period. The study demonstrates that northeast China was under a markedly wetter climate condition during the late deglaciation. For the 16 kyr record in the Hani peat sequence, we infer that moisture delivery by the East Asian Monsoon was relatively invariable in northeast China, but increased evaporation during the warmer Holocene Climate Optimum reduced the effective precipitation, defined by the balance between precipitation and evaporation.
The Holocene Temperature Conundrum refers to the mismatch between proxy-based temperature records and those based on climate model simulations. A possible reason for this mismatch is a putative proxy-based bias in reconstructed summer temperatures, and therefore, regional reconstructions of seasonal temperature are crucial for resolving the conundrum. In this paper, we reconstruct vegetation and climate changes over the last ~10,000 years BP based on a high-resolution pollen record from Gushantun peatland, Changbai Mountains, northeast China. Multiple quantitative reconstruction approaches were used and weighted averaging partial least squares regression (WAPLS) was found to be the most appropriate method for reconstructing Holocene temperature and precipitation. The reconstructed climate record shows that the Holocene Climate Optimum occurred between 8 ka and 6 ka and exhibited a cold month mean temperature that was 3°C warmer than modern temperatures. Climate gradually cooled during late Holocene with a minimum cold month temperature of -19.6°C. Four prominent cold events occurred around 8.7 ka BP, 7.8 ka BP, 5.7 ka BP, and 2.5 ka BP with an amplitude variation up to 3°C. The synthesized seasonal temperature time series and a comparison with other proxies show that the decreasing trend in mean annual temperature is not a seasonal bias caused by summer temperature change. This study provides evidence of a Holocene seasonal temperature change at a regional scale and insights for further understanding of the Holocene Temperature Conundrum.
Peatlands are important carbon pools and stable carbon sinks in terrestrial ecosystems. Studying carbon storage and accumulation characteristics can provide a scientific basis for the conservation and restoration of peatlands. Based on the 2014–2015 survey of the Jilin Provincial Forestry Department on the carbon storage of peatlands in the Changbai Mountains, the surveyed 865 peatlands have a total area of 22,900 hm ² and carbon storage of 18,753,300 tons. There are 275 medium‐sized organic carbon (OC) stocks of peatlands (10000–100,000 tons) in this area, and their carbon storage accounts for 41.3% of the total reserves. The peatland carbon in this area is mainly distributed in the Yanbian Korean Autonomous Prefecture, valleys and the lava platform are the most important geomorphological basis for peatland deposits. The Mudanjiang River Basin has the largest carbon storage and it is dominated by a nutrient‐rich peatland. Peatlands in the Changbai Mountains formed and developed since the Holocene, and the carbon accumulation intensity is different in each stage. The average carbon density of peatlands in this area was 69.74 kg/m ³ with an average value of 81.77 kg/m ² for OC accumulation per unit area. The average value of the carbon cumulative intensity of peatlands was 164.43 ton/km ² and the carbon accumulation rate of peatlands was 38.96 g/(a m ² ).
Increasing afforestation efforts are made in the southeastern Gobi in the Inner Mongolia Autonomous Region of China, where tree and grass coexist. However, afforestation that does not consider climate carrying capacity and afforestation at the cost of grassland reduction have caused more and more drawbacks, although forests are of global significance for preventing dust storm emission. Reconstructions of historical forest and grassland cover, forest-grassland interactions, and drivers are urgently required to test the predictions of ecosystem models that support afforestation. Based on a robust reconstruction method applied to a 19,000-year long pollen sequence from northern China, we show that tree cover peaked during the early Holocene (30.7 ± 12.3%) and gradually declined to 13.2 ± 4.3% during the last two centuries. Temperature, precipitation, and fire drove the postglacial evolution of tree and grass cover, and forest may suppress grassland when tree cover is higher than 13.8%. Our study suggests that a cautious approach should be taken regarding the risks posed by afforestation efforts in the southeastern Gobi.
Northeast (NE) China lies in the northernmost part of the East Asian Summer monsoon (EASM) region. Although a series of Holocene climatic records have been obtained from lakes and peats in this region, the Holocene hydrological history and its controls remain unclear. More specifically, it is currently debated whether NE China experienced a dry or wet climate during the early Holocene. Here we reconstruct changes in mean annual air temperature and peat soil moisture across the last ∼13,000 year BP using samples from the Gushantun and Hani peat, located in NE China. Our approach is based on the distribution of bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) and the abundance of the archaeal isoprenoidal (iso)GDGT crenarchaeol. Using the recently developed peat-specific MAATpeat temperature calibration we find that NE China experienced a relatively warm early Holocene (∼5–7 °C warmer than today), followed by a cooling trend towards modern-day values during the mid- and late Holocene. Moreover, crenarchaeol concentrations, brGDGT-based pH values, and the distribution of 6-methyl brGDGTs, all indicate an increase in soil moisture content from the early to late Holocene in both peats, which is largely consistent with other data from NE China. This trend towards increasing soil moisture/wetter conditions across the Holocene in NE China records contrasts with the trends observed in other parts of the EASM region, which exhibit an early and/or mid-Holocene moisture/precipitation maximum. However, the Holocene soil moisture variations and temperature–moisture relationships (warm–dry and cold–wet) observed in NE China are similar to those observed in the core area of arid central Asia which is dominated by the westerlies. We therefore propose that an increase in the intensity of the westerlies across the Holocene, driven by increasing winter insolation, expanding Arctic sea ice extent and the enhanced Okhotsk High, caused an increase in moisture during the late Holocene in NE China.
The humification degree of peat is a significant climatic proxy for paleoclimate change. Using the alkali-extraction method, a time series of absorbance values of the Hani peatland, Northeast China, was determined, which is used as an indicator for the humification degree of peat. Combined with 14C dating data of peat cellulose, and compared with δ18O and δ13C time series of the cellulose in the Hani peatland, the evidence for the existence of 14 ka paleoclimate was provided. Higher humification degrees hint a warmer-wetter climate, and vice versa. It also reconstructs the four stages of Holocene climate evolution in this region: 11.5–9.8 cal ka B.P., warm and wet period; 9.8–9.0 cal ka B.P., cold and dry period; 9.0–4.8 cal ka B.P., warm and wet period; and 4.8–0 cal ka B.P., warm-wet and dry-cold alternation period. Meanwhile, it is revealed that the abrupt climate shifts signals such as the “8.2 ka” event and the “4.2 ka” event. Results showed that the Hani peat humification degree is of sensitive response to paleoclimate change. Therefore, it is a feasible method to analyze the relationship between paleoclimate change and peat humification degree.
The Qinling Mountains provide a natural boundary between the north and south parts in China, and support a huge variety of plants and wildlife. However, the research on the vegetation history of Qinling forests has remained a blank. In order to choose the most suitable tree species to restore the Qinling forests, it is necessary to carry out studies on the history of forest vegetation in the area. Swamp sediments of mountain basins can store pollen from different historical periods in various levels. Through research on the deposition age of particular sediments in different levels and the characteristics of the pollen assemblage, we can understand the history of the forest vegetation in the area and further provide the scientific basis for the proper management of forests. In this paper, we have divided the vegetation history and climatic variations in the Qinling Mountains into four stages based on the pollen analysis and 14C age determination of a swamp sediment profile of mountain basins at an altitude of 2200 m as well as the pollen analysis on surface soil. In Stage 1 (18,715–7629 cal BP), the vegetation was composed of Abies and Picea. The climate was cold and humid. In Stage 2 (7629–3131 cal BP), the vegetation was dominantly Abies, Picea, Betula, Quercus and Alnus. The climate was warm and humid. During Stage 3 (3131–50 cal BP), the vegetation was dominantly Abies. The climate was cold and humid. During Stage 4 (0–50 cal BP), the vegetation was dominantly Betula, Quercus, Corylus, Alnus, and Tsuga, with fewer Pinus as well as groups of Abies. The climate was warm and dry. There is a noticeable decrease of Abies and Picea in accordance with a climate change from cold and humid to warm and dry. We also noticed an increase of Betula, Quercus, Corylus, Alnus, and Tsuga, which prefer warm and dry environments.
The response of the evolution of Holocene Asian-African summer monsoon
precipitation to orbital forcing and the relationship with tropical
Atlantic ITCZ (Inter-tropical Convergence Zone) as well as sea surface
temperatures are studied with the Kiel Climate Model (KCM), a coupled
atmosphere-ocean-sea ice general circulation model. The transient
simulation for the period of Holocene from 9.5 ka BP (thousands of years
before present day, ka BP) to present (0 ka BP) tests the response of
climate change in Asian-African summer monsoon areas to changes in
orbital parameters in terms of eccentricity, obliquity and precession.
The empirical orthogonal function (EOF) analysis of KCM's orbital
forcing induced evolution of summer precipitation shows different
temporal-spatial patterns in summer precipitation over the Asian-African
summer monsoon influenced areas during the Holocene. The statistical
correlation analysis indicates a closely relationship between
Asian-African summer monsoon precipitation and the lower level (850 hPa)
zonal winds over (0-15N, 30W-30E) as well as the tropical Atlantic ITCZ,
the latter showing a continuously southward shifting of its position
with a gradually weakened intensity during the Holocene, which probably
resulted from the gradually increased south-north gradient of sea
surface temperature (SST) over the tropical Atlantic that weakened the
cross-equatorial flow from southern to northern Hemisphere from 9.5 ka
BP to 0 ka BP.
This paper focuses mainly on the climatic and environmental variations 5 to 3 ka. B.P. with particular reference to one stable warmer and wetter millennium (7.2-6 ka B.P.). Some large-scale centennial warming was accompanied by an increase in precipitation owing to the expansion of the monsoon circulation, e.g. rapid warming during the period from 8.5 to 8.3 ka B.P. and was reflected in the high level of some inland lakes and the sudden expansion of vegetation in pollen diagrams. The growth of the Neolithic culture with agriculture and settlement in the present semi-arid area of Northwest China was undoubtedly related to the dramatic warming and wetting before 8 ka B.P. According to the proxy data of palynological studies, the deviation of annual mean temperature from today's about 7-6 ka B.P. was roughly estimated at about 1°C in South China, 2°C in the Changjiang (Yangtze) Valley, 3°C in North China and Northeast China. The strongest warming by 4–5°C was recorded in Qinghai-Xizang (Tibet) Plateau. The winter temperature rise was much greater than the annual average temperature.
Study on the carbonate content and oxygen isotope of a sediment section in Dabusu Lake revealed that this region has experienced
several cold-wet and warm-dry climatic cycles since 15400 a BP. It was about 6740 a BP when the climate in the region reached
a relatively stable warm stage, so that the lake water was gradually condensed and finally a lake was formed.
In this paper, the Holocene paleoenvironment change sequence in middle Inner Mongolia was primarily reconstructed on the basis
of palynological analysis at the resolution of 70 years on a peat profile, which was located in the northern part of Tumd
Plain with its oldest age of 9100 a. B. P. As the consequence indicated, the Holocene climate change in the middle Inner Mongolia
had undergone cool→temperate→warm→temperate→cool series, and the history could be divided into 5 epochs: 9100 – 7400 a B.
P., with slightly arid and cold climate; 7400 – 5000 a B. P., transitory climate with dynamic fluctuation, earlier period
temperate and slightly arid, and later period temperate and slightly humid; 5000 – 4100 a B. P., with warm and humid climate;
4100 – 1350 a B. P., with transitory climate getting arid, as the result of human being’s growing influence; 1350 a B. P.
— present, with temperate and slightly arid climate, under strong influence of human being. The warm period of Holocene occurred
in 7400 – 4000 a B. P., while the optimal period occurred in 5000 – 4100 a B. P.
Chronology is the basis for using lacustrine sediments to reconstruct the history of environmental change. Radioactive-nuclides
such as 14C, 210Pb and 137Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead
carbon”, the measured 14C age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element,
and easy to migrate vertically in the sediment that leads to the error of the time marker. 210Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed
lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14C dating is stronger. Based on the analysis on results of 14C, 210Pb and 137Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate
the 14C calendar ages, and establish the time sequence for cores CE-1 and CE-2 with result of 210Pb CRS model for the upper 35 cm and recalculated 14C calendar age for sediments bellow 35 cm. Since 1400 cal. a BP, sedimentation interrupted for more than 1000 years. According
to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.
A number of studies have revealed that the climate in the eastern margin of the Tibetan Plateau and Northeast China is sensitive
to postglacial changes. Unfortunately, the link of the past climate evolution between the two regions is not well understood.
In this study, two cores are analyzed to determine this link directly. The high-resolution n-alkanol distribution patterns from two typical peat sequences covering the past 16,000calyears in the northeastern margin
of the Tibetan Plateau and Northeast China, respectively, are closely examined by gas chromatograph–mass spectrometry analysis.
In combination with other palaeoclimatic proxies, it is proposed that the n-alkanol average chain length and (C22+C24)/(C26+C28) ratio could reflect past climate changes in the two peat sequences. The n-alkanol proxies reveal several climatic intervals in the period from the last deglaciation through the Holocene. A comparison
of n-alkanol records between the northeastern margin of the Tibetan Plateau and Northeast China indicates that the start and end
of the warm Holocene Optimum differed at the two locations. The spatially asynchronous pattern of climatic change is possibly
a result of different responses to change in solar radiation. The evolution of the Holocene paleoclimate is more consistent
with changes in Northern Hemisphere solar radiation in Northeast China than on the Tibetan Plateau. The Holocene Optimum began
and terminated earlier in Northeast China than in the northeastern margin of the Tibetan Plateau. Thus, the two n-alkanol proxies provide valuable insights into the regional Holocene climate and local environmental conditions.
Keywords
n-Alkanols–Paleoclimate–Comparative study–The Tibetan Plateau–Northeast China–Solar radiation
Holocene pollen maps of China north of the Yangtze River are presented for six time slices at 2000 year intervals and for ten taxa or taxon combinations on the basis of a data set of pollen diagrams of 142 sites. In spite of the problems with the differentiated data quality, a general correspondence of modern pollen maps with actual vegetation distribution justifies the feasibility of using the pollen maps to illustrate the past temporal and spatial patterns of vegetation change and to tentatively reconstruct palaeo-biomes for the specific time slices. The pollen maps reveal large changes in Holocene vegetation. In the southeastern half of the study area, arboreal taxa generally expanded in the early Holocene times, reaching their maximum at 6 or 4 ka BP, and then shrank during the late Holocene. An exception was found for eastern and northern Northeast China where the maximum development of arboreal taxa occurred during the last 4000 or 2000 years. The evident drop in AP percentages, and therefore the decline of forests, occurred after 6 ka BP in the most southeastern regions, especially in the middle and lower reaches of the Yellow River, and may have been caused by the expansion of farming since the Yangshao Culture period. The reconstructed biomes enable the visual expression of palaeo-vegetation change. A relatively open forest with Pinus as its dominant component developed in the southeastern Loess Plateau and western North China Plain from 8 to 6 ka BP, but it came to an end at about 4 ka BP. On the other hand, cold temperate conifer forest, and temperate mixed conifer and deciduous forest in Northeast China did not yet exist between 10 and 6 ka BP. They appeared at 4 ka BP and then continued to develop through time. Warm temperate deciduous forest experienced a remarkable reduction during the last 6000 years. Alpine valley Picea/Abies forest in the eastern Qinghai-Tibet Plateau developed in the early and mid Holocene, but started to decline at 4 ka BP, and has almost disappeared today.
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