Search

This paper reviews the distribution of Pinus koraiensis in the south of the Russian Far East in the past based on palynological and chronological data. The aim is to determine the chronological timing of the spatial migration of Pinus koraiensis and to correlate it with climate fluctuations explaining the changes of the geographical range of Pinus koraiensis in the south of the Russian Far East during the Marine Isotope Stages MIS 5 (127 000--71 000 BP), MIS 3 (57 000 BP -- 28 000 cal BP), MIS 2 (28 000--11 700 cal BP), and MIS 1 (11 700 cal BP -- to present). The consideration of the obtained pollen fossil data suggests that the range of Pinus koraiensis was in the south of the Russian Far East during MIS 5, as it was proved based on significant pollen grain percentage in the sediments of this age. Pinus koraiensis was widespread along with Pinus densiflora, Quercus, Ulmus, Juglans, Carpinus, and Phellodendron. During MIS 3, Pinus koraiensis was a component of birch-fir and birch-broadleaved forests. In MIS 2, Pinus koraiensis disappeared from the vegetation of this region. In the early Holocene, Pinus koraiensis expanded its range northward and again appeared in the vegetation of the south of the Russian Far East. Soon enough, it became one of the leading components in spruce-fir forests with Quercus and Ulmus. The increase in its proportion in the vegetation in the Holocene coincided mostly with the periods of warming climate from 11 700 to 11 500 cal BP, from 10 100 to 9300 cal BP, from 8800 to 5300 cal BP, from 4700 to 3500 cal BP, and from 2600 to 1800 cal BP. In the present case, the most diverse vegetation with Pinus koraiensis was typical of the Holocene optimum of the south of the Russian Far East from 8800 to 5300 cal BP. [ABSTRACT FROM AUTHOR]

In this paper, grain‐size records of 128 surface samples and six sediment cores retrieved from freshwater marshes across the Sanjiang Plain were employed to reconstruct the marshes' hydrological variation during the Holocene and to discuss its links to the East Asian summer monsoon (EASM) variation. The grain‐size hydrological significance for the marshes' deposits was first interpreted by quantitative analyses of 128 modern samples. The results indicate that the sand fraction exhibits a higher level significance to modern water‐level conditions than other grain‐size parameters. Thus, the sand accumulation rates of the six cores were calculated and employed to reconstruct the Holocene hydrological regime of the marshes on the plain. Based on the cluster analysis, it can be identified that three higher water‐level stages occurred during 6.2–5.6 thousand yr BP, 5.6–4.5 thousand yr BP, and 2.8–2.4 thousand yr BP, whereas four lower water‐level stages occurred during ~8.0–6.2 thousand yr BP, 4.5–2.8 thousand yr BP, 2.4–0.7 thousand yr BP, and 0.7–0 thousand yr BP, respectively. Considering the prevalent monsoon climate on the modern Sanjiang Plain, it is reasonable to believe that the local water‐level fluctuations were mainly regulated by the EASM variation rather than local factors including flooding, waterway modification, depression infilling, and human activities. The higher water‐level stages were linked to a stronger EASM and vice versa. This study provides essential background datasets for understanding the potential controls on the marsh development and degradation on the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

Discriminating the provenance of fine-grained sediments is crucial for reconstructing paleogeography, sedimentary processes, and paleoclimate. In this paper, we investigate the South Bohai Coast to better understand source-to-sink systems in East Asia. This region is influenced by both distant sources such as the large-scale Yellow River and small local river sources flowing from the Luzhong Mountain area. Two Holocene sedimentary cores, dated using optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C chronology, were used to investigate the provenance of the fine-grained sediments over the last 7 kyrs. Clay mineralogy and relevant non-linear modeling were employed for provenance discrimination. The results show that the fine-grained sediments along the South Bohai Coast were mainly derived from the Yellow River during the periods of 7.0–5.4 ka and 4.5–2.6 ka, respectively, while the input from the Luzhong Mountain-derived rivers was greater during 5.4–4.5 ka and 2.6–0.2 ka, respectively. Fluvial activities and marine-terrestrial interaction driven by climate factors such as East Asian winter monsoon, temperature, and precipitation in river basins, dominantly influenced the provenance of fine-grained sediments from 7.0 to 2.6 ka. Anthropogenic impact on provenance increased after 2.6 ka. The chronology of the two cores showed extremely rapid sedimentation rate transitions at 5.2 ka and 1.5 ka, respectively, very likely attributed to anthropogenic-induced rapid progradation. Our study provides a model for better understanding the paleoenvironmental and paleogeographic evolution of a coastal area where multiple sources exist. • Anthropogenically high sedimentation rate in the South Bohai Coast in late Holocene. • Provenance discrimination of the fine-grained sediments in the South Bohai Coast since the mid-Holocene. • The major source of the fine-grained sediments in the South Bohai Coast changed episodically. [ABSTRACT FROM AUTHOR]

This article presents the generalization results of studying the long-term history of paleofires in the world and on the territory of Russia specifically. Perspective and reliable methods of reconstructing the local and regional dynamics of paleofires – micro- and macro-charcoal analyzes, are considered. In the article, we analyze approaches to the study of paleofires, methods of processing and identifying micro- and macroscopic charcoal particles, including the state-of-the-art software tools for their identification ("The Charcoal Quantification Tool", "WinSEEDLETM") and analysis ("CharAnalysis") based on a review of world and Russian scientific achievements. In addition, the possibilities of modern international paleofire databases (Global Charcoal Database, Reading Palaeofire Database), which contain up-to-date information on local and regional paleofire data in the Holocene, are considered here. The results of the study of paleofires globally and on the territory of Russia in particular are analyzed and possible research directions along with fire reconstruction issues are highlighted. The review of Russian publications has shown that the central and south parts of the East European Plain, as well as the southeast of Western Siberia, are the most studied regions in terms of reconstructing the dynamics of paleofires. Few similar studies were carried out in the Urals Mts., Eastern Siberia and the Far East, but most of the regions of Russia remain understudied in this regard. In recent years, Russian researchers are mainly focused on the study of local fire dynamics based on the use of macro-charcoal analysis. The analysis of international paleofire databases (Global Charcoal Database, Reading Palaeofire Database) shows that these data need to be radically revised in relation to key sites in Russia. The authors present a generalized scheme-map of Russia indicating the key areas where paleofire dynamics were reconstructed using micro- or macro-charcoal analyzes. [ABSTRACT FROM AUTHOR]

Insolation changes play an important role in driving monsoon changes at orbital time scales. One key issue that has remained outstanding is whether the Asian monsoon is driven by local insolation from the Northern Hemisphere (NH) or remote insolation from the Southern Hemisphere (SH) at orbital band. Here, we perform a set of sensitivity experiments to quantify the impacts of local and remote insolation changes on the Afro‐Asian summer monsoon at 11 ka BP relative to the present. We show that the Afro‐Asian summer monsoon is overwhelmingly driven by the precession induced local insolation change in the tropical‐subtropical NH. The insolation from NH high latitudes also affects the Afro‐Asian summer monsoon. In contrast, the insolation from SH plays a negligible role. Our model experiments support the idea that the Afro‐Asian summer monsoon are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Plain Language Summary: The Afro‐Asian summer monsoon response to solar insolation has been studied extensively both in observation evidences and model simulations. However, whether the Afro‐Asian summer monsoon is driven by local insolation from the Northern Hemisphere (NH) and remote insolation from the Southern Hemisphere (SH) still remains an open question. This work, for the first time, systematically isolates local and remote insolation impacts on Afro‐Asian summer monsoon using insolation from 11 ka BP. Our study suggests that the Afro‐Asian summer monsoon is driven by local precession insolation change. The increased local summer insolation at 11 ka increases the land‐sea thermal contrast, migrating the subcloud moist static energy maximum and westerly jet northward. These processes lead to a belt of increased monsoon precipitation stretching from North Africa eastward into South and East Asia, resulting in enhanced monsoon circulation and precipitation. The remote insolation from NH high latitude can also drives the incremental Afro‐Asian summer monsoon precipitation but the magnitude is much smaller compared with local effect. The insolation from SH has negligible role. Our model experiments support the idea that NH summer monsoons are driven predominantly by the direct forcing of NH low latitudes summer insolation for the Holocene. Key Points: The first study to completely isolate the local and remote insolation effect on Afro‐Asian summer monsoon at geological timeThe Afro‐Asian summer monsoon during Holocene is driven by local precession forcing in the tropical‐subtropical Northern HemisphereThe "latent heat" hypothesis is not supported by this study [ABSTRACT FROM AUTHOR]

Peatlands are one of the most significant carbon reservoirs in the terrestrial ecosystem. Understanding past peatland carbon accumulation processes and their responses to varying external and internal forcing factors would help reveal the general development patterns of peatland ecosystems and provide useful insights into projecting the fate of carbon reservoirs into the future. In this paper, the basal ages of 17 peat cores were used to explore the lateral expansion processes of the Laolike peatland, northeast China. Two cores were selected to calculate carbon accumulation rates (CAR) and reconstruct moisture/precipitation records based on δ13C and grain size analyses. The basal ages show that the peatland was initiated at 12.1 cal kyr BP, then laterally expanded with its fastest rate occurring during the early Holocene, and reached its largest area around 6 cal kyr BP. The time-weighted mean CAR in the Laolike peatland ranged from 31.1 to 52.9 g C/m2/yr (with an average of 42 g C/m2/yr) during the Holocene. The peatland experienced a high CAR of 52.5 g C/m2/yr from 11.7 to 5 cal kyr BP, followed by a low CAR of 35.1 g C/m2/yr after 5 cal kyr BP. Both lateral expansion and vertical accretion are consistent with the summer insolation, climate seasonality, and the strength of the East Asia summer monsoon (EASM) over multi-millennium timescales, where the CAR correlated well with δ13C and grain size, implying moisture/precipitation might be the primary factors controlling carbon accumulation over millennium timescales. Local conditions, such as topography and hydrology, also played an important role in the process of peatland initiation and lateral expansion, as well as the discrepant CAR within the peatland. This study reveals the roles of climate and local conditions in peatland initiation, expansion, and CAR during the Holocene. In addition, we provide a window for a better understanding of the driving factors of peatland development in the temperate zones of the Northern Hemisphere. • Climate conditions are the primary control on the lateral expansion and vertical accretion of Laolike peatland over multi-millennium timescales. • Moisture/precipitation affects carbon accumulation of Laolike peatland over millennium timescales. • Local conditions play an important role in the lateral expansion and the internal differences of carbon accumulation rate. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon and winter monsoon (EASM and EAWM) are two important components of the East Asian monsoon system. However, the relationship between the two components during the Holocene remains debated in the observation. Here, we use a set of simulations in CCSM3 to investigate the EASM‐EAWM relation across different timescales during the Holocene. It is shown that the intensities of EASM and EAWM are positively correlated at orbital timescale but negatively correlated from millennial down to multidecadal timescales. The positive correlation at orbital timescales is forced by the seasonal insolation forcing, while the negative correlation at millennial and shorter timescales is caused mainly by the internal variability of the Atlantic Meridional Overturning Circulation (AMOC) and the subsequent teleconnection to East Asia via land‐sea thermal contrast. Plain Language Summary: The East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) are important factors that affect regional climate. However, it has remained controversial whether EASM and EAWM vary in‐phase or out of phase in the Holocene. Our simulations show that EASM correlates with EAWM positively at orbital timescale due to the seasonal precessional forcing but negatively correlated from multidecadal to millennial timescales because of the impact of the Atlantic Meridional Overturning Circulation (AMOC). Key Points: Anticorrelations are found in EASM and EAWM variations from multidecadal to millennial timescales during the HoloceneThe negative EASM‐EAWM relation is likely caused by the AMOC [ABSTRACT FROM AUTHOR]

Studies of the vegetation response to abrupt climatic events may provide valuable insights into assessing the impacts of such events under future global warming scenarios. Here we present a detailed record of regional vegetation change based on high‐resolution pollen records for the intervals 9000–7000 and 5000–3000 cal a bp from the Hulun Lake region of north‐eastern China. Our aims were to determine the regional expression of the 8.2‐ and 4.2‐ka events in north‐eastern China, especially their effects on vegetation composition. The results show that the response of the vegetation of the Hulun Lake region to the climatic cooling of the 8.2‐ka event was relatively minor; however, the 4.2‐ka event, which resulted in climatic aridification, resulted in pronounced vegetation degradation. We suggest that the specific characteristics of the 8.2‐ and 4.2‐ka events, together with their duration and the regional climatic background on an orbital time scale, were the main factors responsible for the contrasting vegetation responses. The strengthening and northward shift of the Intertropical Convergence Zone (ITCZ) tended to offset the cooling effect of the 8.2‐ka event on regional vegetation in the mid–high latitudes of East Asia; in contrast, the decrease in summer insolation in the Northern Hemisphere and the southward shift of the ITCZ may have intensified the drought effect of the 4.2‐ka event in East Asia and the associated vegetation degradation. Under future global warming scenarios, both extreme cooling events and extreme drought events may cause a deterioration of the ecological environment; however, the resulting regional vegetation responses may be substantially different. [ABSTRACT FROM AUTHOR]

The use of ecological models enables determining the current distribution of species, but also their past distribution when matching climatic conditions are available. In specific cases, they can also be used to determine the likelihood of fossils to belong to the same species-under the hypothesis that all individuals of a species have the same ecological requirements. Here, using environmental modeling, we reconstructed the distribution of the Mongolian toad, Strauchbufo raddei, since the Last Glacial Maximum and thus covering the time period between the Late Pleistocene and the Holocene. We found the range of the species to have shifted over time, with the LGM population clustered around the current southern range of the species, before expanding east and north during the Pleistocene, and reaching the current range since the mid-Holocene. Finally, we determined that the ecological conditions during the life-time of the mid-Pleistocene fossils attributed to the species in Europe were too different from the one of the extant species or fossils occurring at the same period in Asia to belong to the same species. [ABSTRACT FROM AUTHOR]

The impact of global warming on the climate of northern China has been investigated intensively, and the behavior of the East Asian monsoon during previous intervals of climatic warming may provide insight into future changes. In this study, we use paleovegetation records from loess and lake sediments in the marginal zone of the East Asian summer monsoon (EASM) to reconstruct the EASM during the interval of warming from the Last Glacial Maximum (LGM) to the Holocene. The results show that during the LGM, desert steppe or dry steppe dominated much of northern China; in addition, the southeastern margin of the deserts east of the Helan Mountains had a distribution similar to that of the present-day, or was located slightly further south, due to the cold and dry climate caused by a strengthened East Asian winter monsoon (EAWM) and weakened EASM. During the last deglaciation, with the strengthening of the EASM and concomitant weakening of the EAWM, northern China gradually became humid. However, this trend was interrupted by abrupt cooling during the Heinrich 1 (H1) and Younger Dryas (YD) events. The EASM intensified substantially during the Holocene, and the monsoon rain belt migrated at least 300 km northwestwards, which led to the substantial shrinking of the desert area in the central and eastern part of northern China, and to the large expansion of plants favored by warm and humid conditions. Paleoclimatic records from the marginal zone of the EASM all show that the EASM reached its peak in the mid-Holocene, and past global climatic warming significantly strengthened the EASM, thereby greatly improving the ecological environment in northern China. Thus, northern China is expected to become wetter as global warming continues. Finally, high resolution Holocene vegetation records are sparse compared with the numerous records on the orbital timescale, and there is a need for more studies of Holocene climatic variability on the centennial-to-decadal scale. [ABSTRACT FROM AUTHOR]

Glacial-interglacial changes in the distribution of C3/C4 vegetation on the Chinese Loess Plateau have been related to East Asian summer monsoon intensity and position, and could provide insights into future changes caused by global warming. Here, we present δ13C records of bulk organic matter since the Last Glacial Maximum (LGM) from 21 loess sections across the Loess Plateau. The δ13C values (range: -25%o to -16%o) increased gradually both from the LGM to the mid-Holocene in each section and from northwest to southeast in each time interval. During the LGM, C4 biomass increased from <5% in the northwest to 10-20% in the southeast, while during the mid-Holocene C4 vegetation increased throughout the Plateau, with estimated biomass increasing from 10% to 20% in the northwest to >40% in the southeast. The spatial pattern of C4 biomass in both the LGM and the mid-Holocene closely resembles that of modern warm-season precipitation, and thus can serve as a robust analog for the contemporary East Asian summer monsoon rain belt. Using the 10-20% isolines for 4 biomass in the cold LGM as a reference, we derived a minimum 300-km northwestward migration of the monsoon rain belt for the warm Holocene. Our results strongly support the prediction that Earth's thermal equator will move northward in a warmer world. The southward displacement of the monsoon rain belt and the drying trend observed during the last few decades in northern China will soon reverse as global warming continues. [ABSTRACT FROM AUTHOR]