Abstract
Pollen and charcoal analyses were performed in a sediment core (BP09-6) collected from the deepest area of Beppu Bay, Japan. An accurate age-depth model for the core was constructed using the wiggle-matching method. Pollen grains of Castanea, Castanopsis, and Lithocarpus that are difficult to identify with an optical microscope were identified using a scanning electron microscope. The analyses indicated that lucidophyll forests composed mainly of Quercus subgenus Cyclobalanopsis trees and Castanopsis cuspidata were predominant from 600 BC to AD 1200. These forests declined sharply after a fire event that occurred at AD 1200, indicated by a peak in the amount of macroscopic charcoal fragments in the core, and afterwords most forests in the catchment area of Beppu Bay disappeared due to increased human activities such as fires, logging, and farming. Until the first half of the Edo period, the remaining vegetation was a secondary forest comprising pine, oak, and chestnut trees, as well as light-demanding herbaceous vegetation such as grasses, moxa, and bracken. After approximately AD 1750, i.e., the latter half of the Edo period, pine forests formed in locations devastated by afforestation and natural regeneration. Then, Cryptomeria japonica plantations increased by further forestation.
