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Vegetation history after the late period of the Last Glacial Age has been reconstructed using phytolith records obtained from three tephra sections in the Nangodani Valley basin, southern part of the Aso caldera, south‐west Japan. The topography of the Nangodani Valley basin is divided into three types: somma (caldera rim and wall), caldera floor (central valley) and post‐caldera central cone slope. The vegetation transitions after the late period of the Last Glacial Age in the basin vary between these topographic types. The differences can be explained based on human activities in the valley basin. Grassland dominated by Sasa and Pleioblastus dwarf bamboos (before 8 ka) and Miscanthus and other Andropogoneae pampas grasses (after 8 ka) occurred in the central valley and on the post‐caldera central cone slope, which were strongly affected by human activities including a long period of burning. In contrast, forest with an understory of Bambusoideae plants was preserved on the caldera rim and wall, which was inaccessible because of its steep topography, during the Holocene. [ABSTRACT FROM AUTHOR]

Phytolith and charcoal records in cumulative soils provide a past history of vegetation transition with fire occurrence. By using these records, we assess the long-term response of respective grass types to variations in fire frequency in central Japan. We analyzed phytoliths and macrocharcoals in cumulative soils on the Kannabe Plateau in central Japan. The results of the analysis showed that prior to 8000 cal BP, Sasa species was dominant along with Pleioblastus species under conditions of low fire frequency. Between 8000 and 2000 cal BP, the plateau was covered by grasslands dominated by Pleioblastus species under a warmer climate and/or an increase in fire frequency. Since approximately 2000 cal BP, the grasslands have been covered by Miscanthus sinensis under a high fire frequency of repeated cycles of annual burning, as is present today. The establishment and maintenance of a M. sinensis grassland are probably related to human activity in this area because this species had many uses. Correlation coefficients for phytolith types versus charcoal concentrations in cumulative soils from three areas in central Japan, including the Kannabe Plateau area, were obtained to assess the habitats and related fire frequencies for their respective grass types. These correlations were consistent with their fire tolerance and degree of succession, as inferred from modern observations. This suggests that the modern fire ecology of these grass types can be used to understand their long-term fire ecology. [ABSTRACT FROM AUTHOR]

Silicon (Si) has various biogeochemical functions, such as regulating soil formation and species composition, not only in terrestrial ecosystems but also in aquatic ones. Bamboo stands accumulate large quantities of amorphous Si. Evaluating Si dynamics in moso bamboo ( Phyllostachys pubescens) forests, which are currently spreading through eastern Asia, is important in understanding their biogeochemical function as a supply source of phytoliths. We conducted a study on the organic accumulation and biological cycle of Si in three P. pubescens stands in central Japan with different site characteristics. The amounts of Si accumulation aboveground and underground were 200-360 and 180-460 kg/ha, respectively. These values indicate that Si accumulation underground was comparable to that aboveground. Silicon supply to the forest floor through litterfall was 77-330 kg/ha/year corresponding to 165-706 kg/ha/year as phytoliths (SiO), and 72-88 % was supplied as leaf litter. These results showed that a huge biogenic Si pool derived from bamboo plants exists in the floor of bamboo forests. Furthermore, we estimated the Si turnover time in P. pubescens forests as being 1.3-12.2 years, although this variation may depend on forestry conditions such as soil water content or stem density. [ABSTRACT FROM AUTHOR]

Phytolith and macroscopic charcoal in cumulative soils on the Soni Plateau, Central Japan, were evaluated to clarify the Holocene history of intentional fires and grassland development, and to compare the findings with those derived from pollen and charcoal records in sediments taken from a nearby mire in the previous study. Prior to ~1500 cal. BP, Bambusoid short-cell phytoliths and Pleioblastus-type and Bambusoideae-type bulliform cell phytoliths were abundant with scarce charcoal particles (<1000 particles/cm3). In contrast, since ~1500 cal. BP Andropogoneae-type bulliform cell phytoliths and Bilobate short-cell phytoliths were dominant with abundant charcoal particles (>1000 particles/cm3). Based on correlating these records with pollen and charcoal records in mire sediments, prior to ~1500 cal. BP, dwarf bamboo flourished on the forest floor under largely fire-free conditions, whereas since ~1500 cal. BP, grassland dominated by Japanese pampas grass has been sustained by periodic intentional burning that has continued until the present day. [ABSTRACT FROM AUTHOR]

Abstract: The genesis of a 40-cm-thick buried Holocene humic soil horizon in a 6-m-high sequence near Towada volcano, Japan, was examined by dating stable, plant-derived humin particles by AMS-based radiocarbon (14C), and by analyzing stable carbon isotope ratios (δ13C), phytolith composition, and soil chemical properties. The AMS dating yielded calibrated ages ranging from 7570–7679 to 6180−6313calyr BP. We obtained a strong correlation (r=0.99, ***p<0.001) between sample depth and the mean age. The (now buried) humic soil was formed by the incremental accumulation of tephric loess and aeolian dust at a constant rate of ~30mm per century for at least 1200years. Whilst the soil surface was slowly rising, graminaceous vegetation was supplied at a constant rate so that developmental upbuilding pedogenesis ensued. The soil was buried and isolated by the fall of the Towada-Chuseri tephra about 6200calyr BP. Thus the tephra-soil sequence near Towada volcano represents both developmental and retardant upbuilding pedogenesis. [Copyright &y& Elsevier]