The typical vegetation in northern Japan’s subalpine zones comprises coniferous forest dominated by Abies mariesii.　However, around Mt. Akita-Komagatake in northern Japan, the expected predominance of A. mariesii is not extensively observed, and the predominant vegetation is instead composed of shrubs and the dwarf bamboo Sasa kurilensis.　This area is referred to as the “pseudo-alpine zone.”　Pollen analysis has revealed that A. mariesii was not commonly present during the last glacial period, and that the species began to expand to the subalpine zone during the post-glacial period.　The presence of the pseudo-alpine zone suggests that A. mariesii forests have not yet completely spread into the subalpine zone and are continuing to expand their ranges.　In this study, the environmental conditions and forest dynamics of small stands of A. mariesii forest on Mt. Akita-Komagatake were surveyed to determine whether the A. mariesii forests are still in the process of spreading.

At the survey site, there were few mixed forests where A. mariesii is present along with other plants.　A. mariesii-dominant forest was present on a flat area, and its boundary was sharply defined.　Measurement of the volumetric water content of soil revealed that soil moisture was not only highest in the A. mariesii thick forest, but also consistently higher in the A. mariesii thick and thin forests than in S. kurilensis grasslands and Fagus crenata forest.　Additionally, young A. mariesii trees （shorter than breast height） were found only inside the A. mariesii distribution area.

The presence of A. mariesii in a sharply defined area, the soil moisture results, and the absence of young A. mariesii trees outside A. mariesii forest indicate that the pseudo-alpine zone is formed by the localized distribution of A. mariesii forest in a high soil moisture area, and that A. mariesii forest is not expanding under present conditions.