Saitama, Japan
Saitama, Japan

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Matsuo M.,Kyoto University | Yokoyama M.,Kyoto University | Umemura K.,Kyoto University | Sugiyama J.,Kyoto University | And 8 more authors.
Holzforschung | Year: 2011

The color properties of aging wood samples from historical buildings have been compared with those of recent wood samples that were heat treated at temperatures ranging from 90°C to 180°C. The results of kinetic analysis obtained by the time-temperature superposition method showed that the color change during natural aging was mainly due to a slow and mild oxidation process. In other words, heat treatment could accelerate the changes in wood color that occur during aging. In one sample, the color change (ΔE* ab) after 921 years at ambient temperature was almost equivalent to that of heating (artificial aging) approximately for 6.7 h at 180°C. The results have been interpreted that the aging and the subsequent change in wood color begin at the time of tree harvesting. © 2011 by Walter de Gruyter Berlin New York.

Fan J.,CAS Institute of Geology and Geophysics | Fan J.,University of Chinese Academy of Sciences | Xiao J.,CAS Institute of Geology and Geophysics | Xiao J.,University of Chinese Academy of Sciences | And 8 more authors.
Quaternary Science Reviews | Year: 2016

Teleconnections to the high latitudes, forcing by the tropical oceans and solar variability have all been suggested as dominant factors in the sub-millennial global climate changes, yet there is little consensus as to the relative importance of these factors for the East Asian summer monsoon (EASM) variability. This study presents the results of high-resolution analyses of Ca and Mg concentrations, Mg/Ca ratio, δ18O and δ13C values of endogenic calcites from a sediment core from Dali Lake in the EASM margin, in order to investigate the sub-millennial EASM variability and its possible driving forces during the last 6 kyrs. Increases in these chemical proxy data were interpreted as drought events in the region due to the intensive evaporation losses overwhelming the water input to the lake. The chemical proxy data in this study combined with multi-proxy indicators including grain size component and total organic carbon concentrations from the same sediment core imply that declines in the EASM intensity may have played a dominant role in triggering the drought events during the last 6 kyrs. The results indicate that the EASM intensity significantly declined at the intervals of 5.8–4.75, 3.2–2.8, 1.65–1.15 and 0.65–0.2 kyrs BP. Large declines in the EASM intensity during the last 6 kyrs correspond in time to occurrences of ice-rafted debris in the North Atlantic, indicating that millennial-to-centennial scale changes in the EASM intensity were mainly controlled by climatic processes occurring in the northern high latitudes. These data imply that persistent global warming may be favorable for the strengthening of the EASM circulation and for the transportation of more rainfall to the semi-arid regions of northern China on sub-millennial scales. © 2016 Elsevier Ltd

Zhai D.,CAS Institute of Geology and Geophysics | Xiao J.,CAS Institute of Geology and Geophysics | Zhou L.,CAS Institute of Geology and Geophysics | Wen R.,CAS Institute of Geology and Geophysics | And 5 more authors.
Quaternary Research | Year: 2011

A sediment core from Hulun Lake, Inner Mongolia was analyzed for species assemblages and shell chemistry of ostracodes to investigate changes in the hydrology and climate of the East Asian summer monsoon margin during the Holocene. Darwinula stevensoni was abundant, Ilyocypris spp. scarce, littoral ostracodes absent and Mg/Ca, Sr/Ca and δ18O were low 11,100 to 8300yr ago, indicating high lake levels and cool/fresh waters. Darwinula stevensoni declined largely, Ilyocypris spp. throve, littoral ostracodes were rare and chemical indicators remained in low values 8300 to 6200yr ago, suggesting that the lake continued high stands but water became warm. The lake then contracted and water became cool/brackish 6200 to 4300yr ago. Littoral ostracodes flourished 4300 to 3350yr ago, marking the lowest lake levels of the entire Holocene. The lake level recovered and water salinity decreased 3350 to 1900yr ago. From 1900 to 500yr ago, the lake maintained the preceding status albeit lowered stands and increased salinities 1100 to 800yr ago. During the recent 500yr, the lake expanded and water salinity decreased. The data imply that the East Asian summer monsoon did not intensify until 8300yr ago and weakened dramatically 4300 to 3350yr ago. © 2011 University of Washington.

Wen R.,CAS Institute of Geology and Geophysics | Xiao J.,CAS Institute of Geology and Geophysics | Chang Z.,CAS Institute of Geology and Geophysics | Zhai D.,CAS Institute of Geology and Geophysics | And 3 more authors.
Boreas | Year: 2010

Quantitative palaeoclimatic reconstruction with the weighted averaging partial least squares method was applied to the pollen profile from Hulun Lake in northeastern Inner Mongolia. The data provide a detailed history of variations in precipitation and temperature over the northeastern margin of the East Asian summer monsoon during the Holocene. A warm and dry climate prevailed over the lake region until c. 8000 cal. BP. During the period c. 8000-4400 cal. BP, precipitation increased markedly and temperature gradually declined. The interval between c. 4400 and 3350 cal. BP was marked by extremely dry and relatively cold conditions. Precipitation recovered from c. 3350 to 1000 cal. BP, with temperatures rising c. 3350-2050 cal. BP and dropping c. 2050-1000 cal. BP. During the last 500 years, the climate of the lake region displayed a general trend of warming and wetting. While Holocene temperature variations in the mid-high latitude monsoonal margin were controlled by changes in summer solar radiation in the Northern Hemisphere, they could also be related to the strength of the East Asian summer monsoon. The lack of precipitation during the early Holocene could be attributed to the weakened summer monsoon resulting from the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoonal precipitation during the middle to late Holocene would have been associated with the ocean-atmosphere interacting processes occurring in the western tropical Pacific. © 2009 The Authors, Journal compilation © 2009 The Boreas Collegium.

Wen R.,CAS Institute of Geology and Geophysics | Xiao J.,CAS Institute of Geology and Geophysics | Chang Z.,CAS Institute of Geology and Geophysics | Zhai D.,CAS Institute of Geology and Geophysics | And 4 more authors.
Quaternary Research | Year: 2010

Pollen-assemblage data from a sediment core from Hulun Lake in northeastern Inner Mongolia describe the changes in the vegetation and climate of the East Asian monsoon margin during the Holocene. Dry steppe dominated the lake basin from ca. 11,000 to 8000 cal yr BP, suggesting a warm and dry climate. Grasses and birch forests expanded 8000 to 6400 cal yr BP, implying a remarkable increase in the monsoon precipitation. From 6400 to 4400 cal yr BP, the climate became cooler and drier. Chenopodiaceae dominated the interval from 4400 to 3350 cal yr BP, marking extremely dry condition. Artemisia recovered 3350-2050 cal yr BP, denoting an amelioration of climatic conditions. Both temperature and precipitation decreased 2050 to 1000 cal yr BP as indicated by decreased Artemisia and the development of pine forests. During the last 1000 yr, human activities might have had a significant influence on the environment of the lake region. We suggest that the East Asian summer monsoon did not become intensified until 8000 cal yr BP due to the existence of remnant ice sheets in the Northern Hemisphere. Changes in the monsoon precipitation on millennial to centennial scales would be related to ocean-atmosphere interactions in the tropical Pacific. © 2009 University of Washington.

Bhandari S.,Tribhuvan University | Bhandari S.,Paleo Labo Co. | Momohara A.,Chiba University | Uhl D.,Senckenberg Institute | And 2 more authors.
Review of Palaeobotany and Palynology | Year: 2016

Late Quaternary plant macrofossils from fluvial, fluvio-deltaic and lacustrine sediments of the Gokarna Formation in the Besigaon, Mulpani, and Dhapasi sections in the Kathmandu Valley, Nepal were analyzed. The obtained plant macrofossils allowed us to reconstruct the late Pleistocene paleoenvironment in central Nepal, which was influenced strongly by the SW Indian monsoon system and tectonic movements of the Himalayas. In total, 102 taxa from 52 families were identified to genus or species levels. The dominance of Eurya, Ficus, Morus, Zizyphus, Stephania, Rubus, Quercus subgen. Cyclobalanopsis, Pyracantha, and Carpinus in the lower and middle plant macrofossil assemblages indicates influence of a warm climate. In the upper plant macrofossil assemblages, the higher contents of cooler climatic taxa such as Abies, Pinus, Picea smithiana, Tsuga dumosa, Taxus wallichiana, Quercus subgen. Lepidobalanus, and Betula indicate a climatic deterioration. The higher diversity and common occurrence of aquatic plants indicate rich wetland vegetation in the Kathmandu basin. The plant macrofossil analysis shows at least three cycles of climate fluctuation between warm and cool phases during the deposition of the Gokarna Formation between 53,170. ±. 820. yrs. BP and 49,300. ±. 2100/1700. yrs. BP. These cycles seem to be fairly local or regional, but this can also be correlated with the overall global cooling context in GISP2 oxygen isotope curve in the late Pleistocene. © 2016.

Mitsuguchi T.,Japan National Institute of Environmental Studies | Mitsuguchi T.,Japan Atomic Energy Agency | Hirota M.,Paleo Labo Co. | Group P.L.A.D.,Paleo Labo Co. | And 3 more authors.
Geo-Marine Letters | Year: 2016

In this study, a sea-surface water Δ14C record of AD 1966–2000 (i.e., after the atmospheric nuclear-bomb testing period of the mid-1950s to early 1960s) was reconstructed from a coral sample collected from Iki Island, western Japan. The island is located in the Tsushima Strait where the Tsushima Current flows from the East China Sea (ECS) continental shelf into the Sea of Japan, indicating a strong influence of the ECS shelf water on the island. It is widely accepted that the Tsushima Current originates in the area between the ECS shelf break and the Nansei Islands further offshore as a branch of the Kuroshio Current, although another possible origin is the Taiwan–Tsushima Current System. The Δ14C record from Iki Island shows the following evidence of a response to the atmospheric nuclear testing: (1) an increase from ~55‰ in 1966 to ~133‰ in 1970, (2) a plateau ranging between ~123 and ~142‰ during the 1970s to the late 1980s, and (3) a gradual decrease from ~115‰ in 1990 to ~83‰ in 2000. Comparison of this record with coral Δ14C records from the Nansei Islands (Okinawa Island, Ishigaki Island and Kikai Island), located ~160–280 km off the ECS shelf break and little influenced by the shelf water, suggests that the surface-water Δ14C around Iki Island was ~30–45‰ lower than that of the Nansei Islands from the mid-1960s to late 1970s, and that the Δ14C difference between Iki Island and the Nansei Islands decreased from the end of the 1970s to ~0–15‰ in the mid-1980s to 2000. The lower Δ14C around Iki Island can be explained as follows: (1) in contrast to the Nansei Islands area, the ECS shelf area is a vertically mixed, highly concentrated carbon reservoir significantly connected to subsurface and deeper waters outside the shelf area, strongly suggesting that the surface-water Δ14C of the shelf area (perhaps excepting very shallow innermost shelf areas) was significantly less sensitive to the atmospheric nuclear-bomb 14C spike than that of the Nansei Islands area; (2) the shelf-surface water is conveyed from the northern ECS to Iki Island by the Tsushima Current. Thus, it can be suggested that the post-bomb coral Δ14C record from Iki Island reflects oceanographic conditions of the northern ECS shelf. © 2016 Springer-Verlag Berlin Heidelberg

Noshiro S.,Japan Forestry and Forest Products Research Institute | Kudo Y.,National Museum of Japanese History | Sasaski Y.,Paleo Labo Co.
Quaternary International | Year: 2016

In Japan plant remains excavated from lowland sites have revealed that people managed and used plant resources, especially arboreal ones, around settlements since the early Jomon period starting at ca. 7000 cal yr BP. This management of arboreal resources mainly consisted of management and use of native Castanea crenata (chestnut) and introduced Toxicodendron vernicifluum (lacquer tree) resources. At present this management system seems to have been established suddenly at the beginning of the early Jomon period. This is partly due to the paucity of sites of the preceding incipient and initial Jomon periods that yielded plant materials. Even in these periods, however, people must have used and did some kind of management of plant resources, because the management system appearing in the early Jomon period seems to be too sophisticated to appear suddenly and includes various introduced plants beside the lacquer tree. To clarify the human-plant relationship during the incipient and initial Jomon periods, we reviewed the studies on plant remains carried out in central to northeastern Japan. Based on the collected materials, we discussed change in the human-plant relationship from the incipient and initial to the early Jomon periods from three points, change in the availability of Castanea crenata resources, change in people's mobility and sedentism, and submergence of sites in relation to the late Glacial to the early Holocene transgression. © 2016 Elsevier Ltd and INQUA.

Noshiro S.,Japan Forestry and Forest Products Research Institute | Sasaki Y.,Paleo Labo Co.
IAWA Journal | Year: 2011

To identify archaeological oak woods with very large vessels (> 200 μm), the wood structure of eleven species of evergreen Quercus and Lithocarpus from Japan were studied. Species groups could be identified by the size and frequency of vessels and the ray structure. Quercus phillyraeoides of subg. Sclerophyllodrys had semi-ring-porous wood with small (< 100 μm on average), numerous vessels, and aggregate rays. Two species of Lithocarpus had aggregate to semi-compound rays that came to be divided by the development of vertical masses of fusiform cells. Among species of Quercus subg. Cyclobalanopsis, Q. gilva, Q. hondae, and Q. miyagii had very large vessels with a maximum vessel diameter over 200 μm. Within the species groups, individual species could not be identified just from wood structure, but Q. gilva could be distinguished when the distribution ranges of species were considered. The vertical splitting of semi-compound rays in Lithocarpus with the formation of a vertical wedge of fusiform cells differed from the ray development so far reported in Fagaceae or other taxa that have broad rays, and occurred only in the subgenus Pasania.

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