1999 Volume 16 Issue 2 Pages 115-129
The distribution and growth environment of Pteridophyllum racemosum Sieb. et Zucc. (Pr, hereafter), a herbaceous plant of Papaveraceae endemic to Honshu, were studied through field surveys and a literature review. Based on growth environment, the Pr population was divided into two types. The first, named D-type here, comprises the populations shaded by deciduous trees and shrubs, which are mainly situated on the steep lower slopes of small valleys. The second, named C-type, comprises the populations shaded by conifer trees, such as Abies veitchii and A. mariesii, on flat ground or gentle slopes. The horizontal and vertical distributions of these two Pr types are distinct. D-type is distributed mainly in northern Honshu (Aomori, Akita, Yamagata, Miyagi, Fukushima and Niigata) and tends to be on the Sea of Japan side. In contrast, C-type is distributed mainly in central Honshu (Iwate, Fukushima, Tochigi, Tokyo, Saitama, Yamanashi, Nagano, Niigata, Shizuoka and Gifu), and tends to occur inland and in regions on the Pacific side. Vertically, D-type is distributed on a lower elevation (280m-1400m) than C-type (1040m-2565m). Local population size of D-type is generally smaller than that of C-type. The distinction between D- and C-type did not correlated with the snow depth of the areas. Instead, the distributional pattern of C-type or D-type corresponds respectively to the presence or absence of dense coniferous forest, to the survival or extinction of coniferous forest within the area during the Post Glacial Period, and to the presence or absence of some relict conifers, such as Pinus koraiensis, Picea maximowiczii (in central Honshu) and P. glehnii (in northern Honshu), that reportedly covered a wider area in the Last Glacial Period. These facts suggest that the distributional pattern of the two types of Pr might be caused by differences in climatic and vegetational changes between the associated areas during the Post Glacial Period. Thus, on the Sea of Japan side, Pr once growing in coniferous forest (C-type) in the Glacial Period, became mostly extinct due to the collapse of coniferous forests under the heavy snow conditions of the Post Glacial Period, with a few remaining as D-type. In contrast, in inland regions and on the Pacific side, the coniferous forest has continued to survive, so Pr of C-type has also thrived here throughout the Post Glacial Period.
