抄録
Pollen analysis of a 5, 500 year-core of peaty sediment from an alluvial lowland of the River Kashio, in the southwestern part of Yokohama, Central Japan, showed the following vegetational changes over this area.
(1) At ca. 5, 500y. B. P. such deciduous trees as Quercus subgen. Lepidobalanus, Celtis-Aphananthe and Carpinus-Ostrya abundantly existed along with much Quercus subgen. Cyclobalanopsis and scanty Pasania-Castanopsis, both of which are the main elements of laurel forests. Cyclobalanopsis slightly increased twards ca. 4, 700y. B. P., while many taxa of deciduous broad-leaved trees declined ca. 4, 700y. B. P. But Lepidobalanus remained the main element of forest vegetation till ca. 2, 800y. B. P.
(2) Pasania-Castanopsis was one of the main elements of forest vegetation between ca. 3, 800y. B. P. and ca. 3, 300y. B. P.
(3) Pasania-Castanopsis suddenly decreased ca. 3, 300y. B. P., and Cyclobalanopsis did not increase from ca. 4, 700y. B. P. to ca. 2, 800y. B. P. These trends meant that Lepidobalanus increased ca. 3, 300y. B. P.
(4) Cyclobalanopsis was abundant between ca. 2, 800y. B. P. and ca. 1, 000y. B. P., while Lepidobalanus was not abundant during that period.
(5) A gradual increase in the amount of Cryptomeria began ca. 4, 700y. B. P., and Cryptomeria was abundant between ca. 2, 600y. B. P. and ca. 1, 000y. B. P.
(6) Castanea was one of the main elements of forest vegetation from ca. 4, 700y. B. P. to ca. 3, 300y. B. P.
(7) At ca. 2, 100y. B. P. Gramineae suddenly increased along with the continuous presence of weeds. Pinus suddenly increaed at ca. 1, 000y. B. P., and has been abundant since that time onward. This evidence suggests that human impact on vegetation has been intensified since ca. 2, 100y. B. P., and especially since ca. 1, 000y. B. P.
