Holocene Phytolith Record at Picea glehnii Stands on the Dorokawa Mire in Northern Hokkaido, Japan

Abstract

Phytolith analysis was applied to clarify a vegetation history at Picea glehnii stands on the Dorokawa Mire, northern Hokkaido. Phytolith assemblages from surface samples and Holocene deposits from the mire are used to clarify the stand-scale vegetation history, with special focus on the dynamics of Gramineae, which includes dwarf bamboo, and the establishment of P. glehnii stands on the mire. The phytolith records during the early-Holocene (ca. 12,000 to 10,000 cal BP) indicate the distribution of Pooideae-dominated vegetation, which reflects the cool climate. Phragmites (reed) dominated vegetation from the early to mid-Holocene (ca. 10,000 to 5,000 cal BP) suggests wet conditions like low-moor. The reed was replaced by dwarf bamboo at ca. 5,000 cal BP, although the distribution of dwarf bamboo was scattered. At ca. 1,500 cal BP, dwarf bamboo increased abruptly and has been sustained to the present. Also, Pinaceae type phytoliths began to occur continuously at ca. 1,000 cal BP. Taking into account the relationship between modern vegetation and modern phytolith assemblages on the mire, the occurrence of the Pinaceae type phytoliths from the sediment samples indicates the existence of P. glehnii in the study sites. On the basis of these results, P. glehnii stands with dense undergrowth of dwarf bamboo would have been established in the study sites on the mire by ca. 1,000 cal BP at least.