Long-term response of respective grass types to variations in fire frequency in central Japan, inferred from phytolith and macrocharcoal records in cumulative soils deposited during the Holocene

Abstract

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.