oa Paleovegetational Changes Recorded by Plant Terpenoids in Sediment from Lake SUWA (Japan) Over the Past 27 Ka

Lacustrine and riverine sediments distributed in mountain areas are sensitive recorders of both global and local paleoclimate and paleoenvironment.We applied biomarker analysis to two sediment cores from the coast of Lake Suwa, located in mountain area in central Japan. In these sediments, plant-derived diterpenoids (DTs) and triterpenoids were identified. We established the ratios of sugiol/SDTs, totarol/SDTs and dehydroabietic acid (DAA)/SDTs as vegetation proxies. In these cores, the sugiol/SDTs and totarol/SDTs ratios indicate the contributions of Cupressaceae to the total gymnosperm vegetations, and the DAA/SDTs values mainly indicated the contribution of Pinaceae. The DAA/SDTs values were higher in the glacial period, but the totarol/SDTs and sugiol/SDTs values increased in the deglacial stage. These results indicated the vegetation around Lake Suwa converted from the subalpine coniferous forest, which mainly consisted of Pinaceae, to the temperate coniferous forest, in which the contribution of Cupressaceae was relatively high, with deglacial warming. Also during the cooling events, Pinaceae vegetation in DT indicators rapidly decreased but Cupressaceae vegetation indicators showed increasing spikes. This might reflect the decrease in summer precipitation caused by the weakening of summer monsoon.