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A Preliminary Mapped Summary of Holocene Pollen Data for Northeast China

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A Preliminary Mapped Summary of Holocene Pollen Data for Northeast China See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/229419177 A preliminary mapped summary of Holocene pollen data for Northeast China Article in Quaternary Science Reviews · April 1998 DOI: 10.1016/S0277-3791(98)00017-1 CITATIONS READS 54 51 2 authors, including: Guoyu Ren China Meteorological Administration (CMA), Beijing/China University of Geosciences (CUG), Wuhan 315 PUBLICATIONS 8,203 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: International Atmospheric Circulation Reconstructions over the Earth (ACRE) China View project Regional and urban climatology View project All content following this page was uploaded by Guoyu Ren on 02 October 2020. The user has requested enhancement of the downloaded file. Quaternary Science Reviews, Vol. 17, pp. 669Ð688, 1998 ( 1998 Elsevier Science Ltd. Printed in Great Britain. All rights reserved. PII: S0277-3791(98)00017±1 0277Ð3791/98, $19.00 A PRELIMINARY MAPPED SUMMARY OF HOLOCENE POLLEN DATA FOR NORTHEAST CHINA GUOYU REN* and LANSHENG ZHANG- *National Climate Center, No. 46 Baishiqiao Road, Beijing 100081, Peoples+ Republic of China -Beijing Normal University, Xinjiekouwai Street, Beijing, 100871, Peoples+ Republic of China AbstractÐMaps 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 ºlmus 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. ( Elsevier Science Ltd. All rights reserved INTRODUCTION Here we present the preliminary research results for the Holocene pollen maps from northeast China and Isopoll and isochrone maps have been widely used in describe the methods used to produce contours the studies of late Quaternary paleoecology and whether isopolls or isochrones. The maps are then used paleoclimatology (Bernabo and Webb, 1977; Huntley to interpret the past vegetation. The underlying causes and Birks, 1983; Huntley, 1990; Webb, 1985; Anderson for the vegetation changes are discussed and a few et al., 1994; Ren, 1994). These maps illustrate the conclusions are drawn. changing patterns of past vegetation (Bernabo and Webb, 1977), show how major ecotones have moved (Webb, 1983; Bernabo and Webb, 1977), and aid inter- MODERN ENVIRONMENT OF THE STUDY pretations of past climates (Bartlein et al., 1984; Hun- AREA tley, 1990; COHMAP Members, 1988). Furthermore, this acquired paleoecological and paleoclimatological knowledge aids researchers in testing and calibrating Physiography ecological and climatic models (Huntley, 1990; CO- The study area extends from 37¡ to 59¡N and 110 to HMAP Members, 1988; IGBP, 1994), in estimating 135¡E and includes: Heilongjiang, Jilin Liaoning prov- past variations in the terrestrial carbon reserves (Pren- inces, the Northern part of Hebei Province (including tice and Sarnthein, 1993), and in assessing e¤ects of Beijing Municipality) and Inner Mongolia Auton- human activities on Holocene vegetation and environ- omous Region east of 110¡E (Figs 1 and 2). Major ment (Ren, 1994). topographical features of the area are the extensive Time series of maps summarize late Quaternary Northeast Plain surrounded by a series of mountains pollen data for North America and Europe (Webb, and hills. The Northeast China Plain consists of the 1983; Anderson and Brubaker, 1994; Huntley and Sanjiang Plain, Songnen Plain and Liaohe Plain, each Birks, 1983; Huntley, 1990). In the continental of which is no more than 400 m above sea level. Two East Asia, however, pollen-mapping has not been done series of the northeast-southwest-trending mountains, before 1994, largely due to the low density of sites the Daxingan Mts. and the Changbai Mts., run parallel with well-dated records. Ren (1994) made a first along the western and eastern sides of the Songnen attempt to summarize the Holocene vegetation and Plain and Liaohe Plain, while the Xiaoxingan Range climatic changes of Northeast China through mapping with a northwestÐsoutheast orientation lies to the of the available fossil pollen data. The maps revealed north of the Songnen Plain. some interesting patterns in vegetation change that Both the Liaohe River and the Songhuajiang are hard to identify from analysis of pollen data at River originate in the Daxingan Mts., but the former single sites. flows eastward and then southward into the Bohai Sea, 669 670 Quaternary Science Reviews: Volume 17 and the latter runs up to the northeastern corner of the ized by widely scattered bogs and swamps, which can study area, where it combines with the other two large also be found in the other regions, though to a less rivers, the Heilongjing River and the Wusulijiang extent. River, forming a low-lying Sanjiang Plain character- Climate Nearly every part of Northeast China is strongly influenced by temperate east Asian monsoon. Mean January temperatures range from !6¡C in the south to !30¡C in northern Daxingan Mts. The mean July temperatures have a much more homogeneous distri- bution, with the highest temperatures occurring in the south and the inland plains (Fig. 2). Annual precipita- tion decreases from more than 1000 mm in northern Hebei Province and southeastern Liaoning Province to less than 300 mm in some stations west of Daxingan Mts. (Fig. 3). Eighty to ninety percent of the total annual precipitation falls in the three summer months (JuneÐAugust). Little snow or rain falls in winter and spring, and most regions are normally dry during the beginning stage of plant growth, a unique climatic phenomenon not characteristic of the same latitude areas of Europe and North America. The climates are most like those in Kansas, Minnesota, and Alberta in North America. Vegetation Modern vegetation cover consists of the temperate types, including temperate moist forest, temperate forest steppe and temperate steppe (Fig. 4). Forest is found in mountain and hill regions, and steppe dominates the major fluvial plains and the Inner Mongolia Plateau west of the Daxingan Mts. A mixed plant belt called forest steppe between the forest of the Changbai Mts. and the steppe in the Songnen and FIG. 1. Physiographic regions of Northeast China. Liaohe Plains. FIG. 2. Mean January and July temperature (¡C) in northeast China. G. Ren and L. Zhang: Summary of Holocene Pollen Data 671 Warm temperate deciduous forest grows in the south of the study area, where varied species of Quercus are common, and species of ºlmus, Juglans, ¹ilia, Carpinus, Corylus, Pinus and Betula are also important components of the forest. Between the cold- temperate conifer forest and the warm-temperate de- ciduous forest is temperate mixed conifer and decidu- ous forest, in which Pinus koraiensis is the dominant species. Other important species include Abies holo- phylla, Carpinus cordota, Acer mono, Quercus mon- golica, ºlmus propinqua, Fraxinus mand shurica, Jug- lans mand shurica, ¹ilia amurensis and Betula platy- phylla. As a representative type for Northeast China, the mixed forest covers the Changbai Mts., Xiaoxingan Range and the western pediment belts facing the Song- nen Plain (Wu, 1980). Temperate steppe mainly develops on the central plains and the Inner Mongolia Plateau. Its floristic components mainly include the families of Gramineae, Chenopodiaceae, Compositae and Cyperaceae. One genus most commonly found in the steppe is Artemisia (Wu, 1980; Academic Sinica, 1985). The best developed forest steppe appears on the eastern fringe of the Song- nen and Liaohe Plains, where trees and herbs grow alternately in the di¤erent topographical units. Of the FIG. 3. Annual precipitation (mm) in northeast China. trees, those corresponding to the deciduous compo- nents of the mixed forest to the east are usually the most common. At present, however, nearly the whole forest steppe belt and part of the steppe close to it are farmed (Fig. 4). DATA AND METHODS Data Pollen data are mainly taken from the published research reports for single sites, with the exception of a few sites that came from unpublished dissertations. Considerable variation exists among the data in such aspects as the topographic position of the sampling sites, sediment type of the samples, sampling interval, radiocarbon-dating control, laboratory analysis pro- cedure, and percentage calculation method. These problems have to be taken into consideration before confidence is given to the data. Topographic position: Pollen studies
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