Identification of buried woods and pollen analysis were carried out to reveal the paleovegetation of the Sanbe-Azukihara buried forest in Shimane, southwestern Japan. The buried forest was formed by a debris avalanche derived from Mt. Sanbe at ca. 3500 yrs BP. The paleoflora in the Sanbe-Azukihara buried forest was mainly composed of Cryptomeria japonica, Chamaecyparis obtusa, Cephalotaxus harringtonia, cf. Castanopsis cuspidata, Quercus subgen. Cyclobalanopsis sp., Zelkova serrata, Aesculus turbinata, Cercidiphyllum sp., and Sapindus mukorossi. The study results indicated that vegetation changed gradually from a wasteland to a Cryptomeria japonica forest through a riparian forest between 4500 and 3500 yrs BP. In central Chugoku region where the study area is located, the high ratio of C. japonica pollen has not so far been reported from pollen analytical studies through the Holocene. The discovery of a buried forest of Cryptomeria japonica in the central Chugoku region shows that this area had a cool humid climate suitable for the growth of C. japonica and provides a material to clarify the reason for the weak development of C. japonica forests during the Holocene in this region.
Vegetation history since the late Middle Pleistocene was clarified from the pollen analysis of the upper 10 m of the OK4 core from the Okute basin in Mizunami city, Gifu Prefecture. The age-depth curve of interbeded five tephra layers indicated that the upper 10 m of the core ranges over the past 170 ka (Marine Isotope Stages 1–6). We recognized 14 local pollen zones (OK4-I to OK4-XIV): I (ca. 167–155 ka), VIII (ca. 64–56 ka), and XI (ca. 30–26 ka), Pinaceae forests; II and III (ca. 155–125 ka), and XII (ca. 26–16 ka), Pinaceae forests with Betula; V and VI (ca. 115–90 ka), Cryptomeria japonica-Sciadopitys verticillata forests; VII (ca. 90–64 ka), Sciadopitys verticillata- Pinaceae forests; IX and X (ca. 56–30 ka), mixed forests of Pinaceae and deciduous broad-leaved trees; XIII (ca. 16–7 ka), deciduous broad-leaved forests (mainly, Quercus subgen. Lepidobalanus); IV (ca. 125–115 ka) and XIV (ca. 7–0 ka), mixed forests of broad-leaved trees and Pinaceae with Quercus subgen. Cyclobalanopsis. We revealed that K-Tz fell at the last stage of Cryptomeria japonica-Sciadopitys verticillata forests (ca. 115–90 ka) and that, after the fall, Cryptomeria japonica declined and pinaceous trees dominated in the forests. Keywords: K-Tz, Marine Isotope Stage 6, pollen analysis, Tokai district, vegetation history
Environmental changes in the Sencho-muta basin at Tano, Kokonoe, Oita Prefecture, are discussed from pollen, phytolith, and charcoal-fragment analyses of drilling cores. Around the fall of K-Ah (7.3 ka), a lake spread in the northern part of the basin, shallow water in the central part, and dry soil in the southern part. In the central part, grass pollen such as Gramineae and Cyperaceae dominated with evergreen broad-leaved tree pollen of Quercus subgen. Cyclobalanopsis, and grass phytoliths and charcoal fragments occurred frequently throughout the samples. Grassland with an evergreen forest has been the main vegetation around Sencho-muta since 8000 years ago. After the fall of K-Ah, Castanea/Castanopsis/Lithocarpus pollen and bambusoid phytoliths decreased, and Cyclobalanopsis pollen and charcoal fragments occurred most abundantly. Until the deposition of black silt below T2 tephra, several sand and gravel layers intercalated by riverine activities. Just below T2, black silt changed to soil at all points, implying depression of water level in the whole basin. Oryza sativa phytoliths occur in the top of the black silt with abundant Pinus pollen. Soil over T2 commonly includes charcoal fragments and phytoliths. Finally soil developed at all points. Oryza sativa phytoliths and Pinus and Cryptomeria pollen increase again by human activities.