大阪府河内平野における過去一万三千年間の植生変遷と古地理

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The vegetational history and the paleogeography of the Kawachi Plain for the last 13, 000 years are summarized as follows;1) For the period between 13, 000 and 10, 200yr.BP, the vegetation in the Kawachi Plain was dominated by the subalpine forest including Pinus (Haploxylon), Picea, Abies and Tsuga. The climate was colder and drier than that of the present. However, around the period between 11, 800 and 11, 000yr.BP, there was a short warm duration characterized by the increase of the temperate trees such as Quercus, Carpinus, Ulmus, zelkova and Corylus. The sea-level was nearly more than 22m lower than the present one. The flood plain was spreaded over the Kawachi Plain and Menyanthes, Cyperaceae and Sphagnum grew on the marshy lowland.2) Around 10, 200yr.BP, the subalpine trees were abruptly reduced and the temperate trees (Quercus, Ulmus, Zelkova and Carpinus) began to increase. This change of vegetation was perhaps caused by the sudden climatic warming. Warm temperate plants which had been thrusted into the marginal part of the southern Kyushu and Shikoku migrated to the northward and upward. The period between 10, 200 and 9, 000 or 8, 500yr.BP was characterized by the prominant of grass pollen (Artemisia, Compositae, Persicaria and Lythrum) indicating the low density of the forest.3) Around 9, 000 or 8, 500yr.BP, the temperate trees such as Quercus, Celtis, Aphananthe, Ulmus, Zelkova, Carpinus and Fagus rapidly increased indicating the climatic amelioration. After that time, sea-level rised fast and the shoreline transgressed into the Kawachi Plain.4) Around 6, 500yr.BP, the migration of the plants was almost completed and the warm temperate species (mainly Cyclobalanopsis and Castanopsis) were able to colonize in the hilly district of the Kawachi Plain. At this period, the embayment area was spreaded over the lowland of the Kawachi Plain.5) Around 3, 000yr.BP, the shoreline regressed and the lobate delta was spread over the southern part of the Kawachi Plain. The microrelief of the lobate delta was chracterized by two landform types, i. e. dry highland and marshy lowland. Yayoi man took the dry highland as a residential place and the marshy lowland as a rice field. The vegetation around the residential highland was covered with grasses. The climate was slightly cooler and wetter than that of the present. In the late Yayoi period, the great flood occurred and the residential area was submerged. After this catastrophic submergence, the Kawachi Plain was covered by the lagoonal deposit.6) At the beginning of the Kofun period, the strandlinie of the Kawachi lagoon regressed and the flood plain of the Yamato R. was spreaded over the southern part. Man readvanced into the flood plain which was composed of natural levee deposit. From this period, man's impact on vegetation was enlarged and the broad leaved forest (Cyclobalanopsis, Castanopsis, Celtis and Aphananthe) was deforested by Kofun man. The pine forest rapidly expanded.
日本第四紀学会の論文

大阪府河内平野における過去一万三千年間の植生変遷と古地理

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