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Watanabe T.,Tohoku University | Minoura K.,Tohoku University | Nara F.W.,Tohoku University | Shichi K.,Japan Forestry and Forest Products Research Institute | And 3 more authors.
Global and Planetary Change | Year: 2012

Multi-proxy records (geochemistry, clay mineralogy and paleontology) from three sediment cores from Lake Hovsgol, northwest Mongolia, provide paleoenvironmental changes in continental Asia from the last glacial to the present (during the last 29calka BP). This paper presents the first continuous δ13C and δ18O dataset for ostracod shells (Cytherissa lacustris) from Lake Hovsgol sediments. A positive shift in ostracod δ13C values (from +0.5‰ to +3.2‰) began at ca. 21calka BP, and was associated with a decrease in δ13C values of total organic carbon (from -24.7‰ to -27.3‰) and an increase in the mass accumulation rate of total organic carbon (MAR-TOC). These results suggest that increased lake productivity led to the 13C-enrichment of dissolved inorganic carbon in Lake Hovsgol. In addition, decreases in clay content and the illite crystallinity index (full width at half maximum of the 10Å peak) began at ca. 21calka BP, indicating an increase in surface runoff and a change in sources of clastic materials in the watershed. The highest δ18Oostracod values (up to -4.8‰) at 16-15calka BP indicate the increases in precipitation from the East Asian monsoon. The total pollen amount increased, and Betula, Alnus, and Salix were dominant (up to 53%, 30%, and 6%, respectively) after 16-15calka BP. These findings indicate that broad-leaved trees expanded around Lake Hovsgol. In addition, fossil diatom valves appeared after 16-15calka BP, suggesting climate amelioration, and increased input of soil-derived nutrients and dissolved silica. Between 10 and 5calka BP (Holocene climate optimum), productivity was high in and around the lake (MAR-TOC, up to 47.3mg/cm2kyr; MAR-diatoms, up to 14.4×108 valves/cm2kyr; total pollen concentration, up to 9.0×105 grains/cm3). Environmental changes during the last 29kyr in and around Lake Hovsgol are clearly associated with fluctuations in summer insolation and East Asian monsoon intensity. © 2012 Elsevier B.V.

Shichi K.,Japan Forestry and Forest Products Research Institute | Takahara H.,Kyoto Prefectural University | Hase Y.,Goshoura Cretaceous Museum | Watanabe T.,Tohoku University | And 4 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

We reconstructed vegetation changes and fire events in the southern Lake Baikal region over the past 33. cal. kyr using a sediment core from the Buguldeika Saddle, southern Lake Baikal, to examine vegetation response to past short-term climate variations. Herbs, such as Artemisia and Asteraceae, were dominant just before the Last Glacial Maximum (LGM). Low pollen accumulation rates (PARs) with little herb pollen indicate sparse herbaceous vegetation cover during the LGM. Picea expanded after the Bølling interval, suggesting expansion of riparian areas, and shrub Alnus rapidly increased during the following Allerød interval. Abies and Pinus subgen. Haploxylon began to increase at the beginning of the Holocene and Pinus subgen. Diploxylon has been highly dominant since the middle Holocene. The vegetation change after the LGM is similar to that from other sites in the Lake Baikal region, but the responses to short-term climate events are pronounced. Fluctuations in herb elements and vegetation cover as indicated by the PAR correspond to the Younger Dryas (YD) cooling event. The decline in the PAR and increase in herb taxa were remarkable at the beginning of the YD, but Larix and Picea trees were distributed in river valleys near Lake Baikal in the latter half. The rapid expansion of Betula and Artemisia following frequent fires in the early Holocene may have been in response to the 8.2. cal. ka. BP cooling event. From these findings, the southern Lake Baikal region, including the Selenga River basin, may possibly have been more sensitive than other parts of the region to abrupt climate changes. © 2013 Elsevier B.V.

Matsumoto K.,Japan Forestry and Forest Products Research Institute | Noerdjito W.A.,Indonesian Institute of Sciences | Fukuyama K.,Association of International Research Initiatives for Environmental Studies
Journal of Tropical Forest Science | Year: 2015

The biodiversity status of insects in plantations in the tropics is little known. To evaluate the biodiversity restoration function of the plantation, we compared the species richness and species composition of butterfly assemblages in three plantations of Acacia mangium, two ex-forest grasslands and a native forest in East Kalimantan based on repeated 45-min sampling sessions in December 2004, May 2005 and December 2005. Higher species richness was recorded in plantation than in grassland, indicating that the plantation could support more butterfly species. Even higher species richness was found in the native forest. The species accumulation trend indicated by a rarefaction curve suggested that there were many more undiscovered species in the native forest. The butterflies found in the native forest included many range-restricted species, which were not found in the plantation and grassland. These range-restricted species were thought to be specific to the interior of the native forest and unlikely to colonise the plantations. Artificial plantations established on degraded grasslands can enrich butterfly assemblage, but this enrichment is mainly due to the increase in species with moderate or wide distribution ranges, rather than the recovery of range-restricted native forest species. © Forest Research Institute Malaysia

Hasegawa M.,Japan Forestry and Forest Products Research Institute | Okabe K.,Japan Forestry and Forest Products Research Institute | Fukuyama K.,Association of International Research Initiatives for Environmental Studies | Makino S.,Japan Forestry and Forest Products Research Institute | And 5 more authors.
Experimental and Applied Acarology | Year: 2013

The community structures of Mesostigmata, Prostigmata, and Oribatida in the soil of broad-leaved regeneration forests and conifer plantations of various ages were assessed alongside soil and plant environmental variables using three response metrics (density, species richness, and species-abundance distribution). The density and species richness of mites recovered swiftly after clear-cutting or replanting. Oribatid mites dominated the soil mite communities in terms of densities and species richness for both forest types. Soil mite communities in broad-leaved forests was related to forest age, the crown tree communities index, and forest-floor litter weight. In contrast, soil mite communities in the conifer plantation sites were related to various indices of understory plants. The development of the understory plants was synchronized with the silvicultural schedules, including a closed canopy and thinning. Such a conifer plantation management may affect indirectly the community of mites. © 2012 Springer Science+Business Media Dordrecht.

Nara F.W.,Tohoku University | Watanabe T.,Tohoku University | Watanabe T.,University of Liege | Kakegawa T.,Tohoku University | And 6 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

Changes in sulfur cycles in Lake Hovsgol (northwest Mongolia) are discussed on the basis of total organic carbon (TOC), total sulfur (TS) concentrations and stable sulfur isotope ratios (δ34S) in two sediment cores (X104 and X106) covering the last glacial to the present. Correlation plots of TOC and TS (C-S plots) of the sediment cores indicate dissolved sulfate enrichment in sediment pore water and high sulfate reducing bacteria (SRB) activity during the climate transition from the last glacial to postglacial period (LG-PG transition, from ca. 21 to 11.6calka BP). In addition, positive shifts of δ34S values (from +3.7‰ to +32.6‰) were observed during the LG-PG transition. These results suggest a large influx of 34S-rich dissolved sulfate into the lake during this period. The 34S-rich dissolved sulfate may have accumulated on the shore (wetlands and marshes) of Lake Hovsgol during the last glacial period. Owing to the increase in atmospheric precipitation and lake level rise during the LG-PG transition, the 34S-rich dissolved sulfate may have been supplied from the shore to the lake. Increased sulfate influx during the LG-PG transition has also been observed in a Lake Baikal sediment core. Our new sulfur geochemical data shows past-environmental changes, particularly moisture changes, within continental Asia during the climate transition. © 2010 Elsevier B.V.

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