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Lim J.,Korea Institute of Geoscience and Mineral Resources | Fujiki T.,International Research Center for Japanese Studies
Quaternary Science Reviews | Year: 2011

At centennial to millennial timescales, little is known of C3 and C4 plant productivity's responses to past regional climate changes and the dominant forcing factors during the Holocene, although large-scale changes in glacial-interglacial periods have been attributed to changes in aridity, temperature, and CO2 concentration. We investigated the δ13C of TOC, C/N ratios, and pollen in samples from a wetland on Jeju Island, Korea. The bulk isotopic signal ranging from -17‰ to -29‰ was partitioned into C3 and C4 plant signals by using a binary mixing model and calculating separate organic carbon-accumulation rates for C3 and C4 plants (OCAR3 and OCAR4) during the last 6500 years. Pollen data indicated that the temperate deciduous broadleaved trees replaced grassland dominated by Artemisia, dry-tolerant grass, and further expanded in the maar. The long-term decreasing trend of Artemisia-dominated grassland was similar to those of δ13C values and OCAR4. The multi-centennial to millennial variability superimposed on the gradual increasing trend of OCAR3 was inversely correlated with those of the sea surface temperature (SST) in the western tropical Pacific (WTP) and El Niño-Southern Oscillation (ENSO) activity, suggesting that C3 plants have stronger sensitivity to regional climate change driven by oceanic forcing. Our data suggest that vegetation changes in a coastal area in East Asia were affected by monsoonal changes coupled with SST in WTP and ENSO activity. The vegetation change on Jeju Island varied quite differently from change in the westerly pathway, suggesting only a weak influence from high-latitude-driven atmospheric circulation changes. We conclude that centennial- to millennial-scale climate changes in coastal regions of East Asia during the mid- to late-Holocene may have been mainly controlled by low-latitudinal oceanic forcing, including forcing by SST and ENSO activity. © 2011 Elsevier Ltd.

Nasu H.,Graduate University for Advanced Studies | Gu H.-B.,Hunan Provincial Institute of Archaeology and Cultural Relics | Momohara A.,Chiba University | Yasuda Y.,International Research Center for Japanese Studies
Archaeological and Anthropological Sciences | Year: 2012

Archaeobotanical analysis of moat sediments from the Neolithic site of Chengtoushan, Hunan, China, provides evidence of the land-use change for rice and foxtail millet cultivation around the site. Rice constantly appeared through the three phases of Daxi culture with high percentages, while accompanying wetland species of paddy field weeds gradually decreased. In contrast, foxtail millet increased together with upland field and ruderal weeds through the time. These changes suggest that foxtail millet cultivation was established with the expansion of dry farming in region of the site, while rice cultivation was continuously practiced on the alluvial plain surrounding the site. This diversification of land-use through the addition of foxtail millet cultivation may be attributed to population increase or as a buffer to natural disasters such as flooding. In addition, gathering of wild nuts and fruits continued alongside cultivation. These multiple strategies for food procurement provided sustainable food supply for the population of Chengtoushan for 1,800 years. © 2011 Springer-Verlag.

Tarasov P.E.,Free University of Berlin | Nakagawa T.,Northumbria University | Demske D.,Free University of Berlin | Osterle H.,Potsdam Institute for Climate Impact Research | And 11 more authors.
Earth-Science Reviews | Year: 2011

This study presents a newly compiled dataset of modern pollen and climate data from 798 sites across Japan and the Russian Far East. This comprehensive reference dataset combined with the modern analogue technique (MAT) provides a powerful tool for pollen-based reconstruction of the Quaternary Northwest Pacific climate. Pollen-derived reconstruction of the modern climate at the reference pollen-sampling sites matches well with the estimated modern climate values (R2 values vary between 0.79 and 0.95, and RMSEP values vary between 5.8 and 9.7% of the modern climatic range for all nine tested variables). The successful testing of the method encourages its application to the fossil pollen records. We used a coarse-resolution pollen record from Lake Biwa to reconstruct glacial-interglacial climate dynamics in central Japan since ~438kyr and compared it to the earlier reconstruction based on a less representative reference dataset. The current and earlier results consistently demonstrate that the coldest glacial intervals experienced pronounced cooling in winter and moderate cooling in summer, supporting the growth of cool mixed forest (COMX) where warm mixed forest (WAMX) predominates today. During the last glacial, maximum (~24kyr BP) mean temperatures of the coldest (MTCO) and warmest (MTWA) month were about -13°C (RMSEP=2.34°C) and 21°C (RMSEP=1.66°C) respectively, and annual precipitation (PANN) was about 800mm (RMSEP=158.06mm). During the thermal optimums of the interglacial intervals, the temperatures of the coldest and warmest month were above 0°C and 25°C respectively, leading to the reconstruction of WAMX and temperate conifer forest (TECO). Although both these vegetation types grow in the southern part of Japan today, WAMX requires warmer space. The presence of WAMX during marine isotope stages (MIS) 11 and 1, and its absence during MIS 9 and MIS 5 contradict the marine isotope and Antarctic ice records, suggesting that the latter two interglacials were the warmest of the last 800kyr. The apparent contradiction allows at least three different explanations including low temporal resolution of the pollen record; different trends in CO2 concentrations during 'short' and 'long' interglacials; and regional climate variability and non-linear response of different regions to the global forcing. More definitive conclusions will be possible on the basis of forthcoming high-resolution pollen records from central Japan. © 2011 Elsevier B.V.

Yamada K.,University of Turku | Kamite M.,Tokyo Metroplitan University | Saito-Kato M.,National Museum of Nature and Science | Okuno M.,Fukuoka University | And 2 more authors.
Quaternary International | Year: 2010

Micro-sedimentological, geochemical data from Lakes Ni-no-Megata and San-no-Megata in northeastern Japan are used to reconstruct environmental and climate changes over the last 2000 years. Comparing these records in two neighboring maar lakes allows reconstruction of centennial scale climate change concerned the East Asian monsoon activities without the influence of human activities. S content and coarse mineral grains records show that long-term climate changes, with one warm/humid interval from AD 1200 to 750, and two cold/dry intervals from AD 1 to 750, AD 1200 to the present. These climate changes have similar trends to Asian monsoon records in China, and could correspond to the Dark Age Cold Period (DACP), the Medieval Warm Period (MWP) and the Little Ice Age (LIA) climate changes in Europe. Moreover, short-term climatic deterioration events occurred in the 6th, 10th and 18th centuries. Particularly the event around the 10th century is well correlated with other paleoclimate proxies in China, Europe and Mesoamerica, suggesting tele-connection by atmospheric circulation through the Northern Hemisphere. However, the record is asynchronous with solar activity. This might suggest the solar forcing has indirectly influenced lake sedimentation associated with Asian monsoon activities in Japan. © 2009 Elsevier Ltd and INQUA.

Yamanaka T.,Kyushu University | Yamanaka T.,Okayama University | Miyabe S.,Kyushu University | Miyabe S.,Marine Works Japan Ltd. | And 3 more authors.
Journal of Asian Earth Sciences | Year: 2010

The Aira Caldera in Kyushu, southwest Japan, is a huge Quaternary caldera that formed as a result of an eruption ca. 25. ka. Most of the caldera is now submerged under the innermost part of Kagoshima Bay, which is part of a large graben. The caldera was initially a freshwater lake but eventually became a marine environment. Previous studies demonstrated that the center part of the bay was occupied by fresh water during sea-level lowstand around 18. ka, and was invaded by marine water at ca. 13. ka, during rapid post-glacial sea-level rise. Geochemical and fossil diatom assemblages, however, strongly suggest that seawater was present in the caldera lake during the 18-13. ka interval: sediment from this time contains both elevated sedimentary sulfide content and marine diatom species. This evidence implies that water in the center part of Kagoshima Bay was not entirely fresh for the last 18,000. yrs, and that the Aira Caldera changed abruptly from a freshwater lake to a marine environment at 13. ka. This abrupt change may have resulted from collapse of part of the caldera wall during eruption of Sakurajima Volcano. © 2010 Elsevier Ltd.

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