北アメリカ西海岸地帯における植生変遷史 : I.ミネラル湖とホール湖

抄録

A progressive succession of the vegetation is recognized in response to the gradual, changing climate in the Puget Lowland approximately for the past 19,000 years : (1) tundra (pollen zone T, spanning from over 19,000 to 16,300 yr B.P.), (2) Pinus contorta-Picea engelmannii-Tsuga mertensiana parkland (LI, 16,300-12,000 yr B.P.), (3) Pinus contorta-Abies-Alnus woodland associated with Picea engelmannii (LII, 12,000-10,000 yr B.P.), (4) Pseudotsuga menziesii-Alnus rubra woodland with Pteridium aquilinum (PIa, 10,000-8,500 yr B.P.), (5) Pseudotsuga menziesii-Alnus rubra woodland accompanied by Pteridium aquilinum on relatively dry soils, and Thuja plicata on moist soils (PIb, 8,500-7,000 yr B.P.), (6)Pseudotsuga menziesii-Thuja plicata forest (PII, 7,000-5,000 yr B.P.), (7) Tsuga heterophylla-Thuja plicata-Pseudotsuga menziesii forest (PIIIa, 5,000-100 yr B.P.), and (8) anthropogenic Alnus rubra forests with abundant herbs and bracken fern (PIIIb, after 100 yr B.P.). Modern lowland coniferous forests, having a history of only about 5,000 years, were extensively logged by Euro-American settlers about 100 years ago.