北関東の二次林植生について
1953 年 35 巻 1 号 p. 9-13
詳細
1953 年 35 巻 1 号 p. 9-13
An intermediate zone exsists between the cool-temperate beech climax and the warm-temperate broad-leaved evergreen climax in Japan. On account of its heterogeneity, very different names are given to the zone and the related communities as follows, -
Aida-tai (intermediate zone) TANAKA (1887); Abies firma-Pinus densiflora-Fagus japonica-Quercus serrata-Castanea crenata-Zelkowa serrrata formation as the cool-temperate lowland vegetation after KURYTA (1933) and FUZISTMA (1941): Castaneeon crenatae NAKANO (1942); the warmtemperate deciduous forest zone KIRA (1949); Tsugion Sieboldii SUZ.-Tok (1952).
The Utunomiya University Forest, situated in this intermediate zone (36°46′ N, 139°20′E, 300-400m) lies farther north from the northern range of the broad-leaved evergreens but bears no beech stand. The vegetative period (months warmer than 10°C) is seven months here, too warm for the beech climax (ibid. 4-6months) but too cold for the evergreen climax (ibid. over 8 months). The liparitic ground rock of lower tertiary age is covered by quarternary Kantô loam interstratified by two or three layers of pumice beds.
We recognized an association, Rhodoreto-Pinetum densiflorae, namely Pinus densiflora-Rhododendron Kaempferi association. Already this has been named by different authors. Pinus densiflora-Castanea crenata-Quercus serrata association KURITA, Pinus densiflora-Quercus serrata association YOSIOKA pro parte, and Castaneeto-Pinetum quercetosum serratae NAKANO are all synonymous; but these are not adopted as a proper name, because of the trinominal nomenclature and the combined names exclusively of trees. Consequently, a new name will be necessary for it.
Its characteristics are Rhododendron Kaempferi, Hydrangea hirta, Carex gifuensis and Dioscorea gracillima when compared with cariceto-Pleioblastetum ehinonis and Castaneetum crenatac. This has two subassociations. Carex lanceolata subassociation, differentiated by Artemisia Keiskeana, Carex lanceolata and Paederia chinensis, is found on the southward exposition, while Carex gifuensis sub association, differentiated by Carex gifuensis and Astilbe congestaprefers to the northward slopes.
The upper tree layer attains to 10-15m. and is dominated by Pinus. The lower tree-layer is a almost absent probably by the human disturbance. The shrub layer is composed of deciduous nanophanerophytes like Rhododendron Kaempferi mixed with evergreen Pleioblastus chino. The upper herb layer is about 30cm in height and is composed by hemicryptophyte, like Astilbe and Artemisia. The lower 10-15cm tall dominated by Carices or Disporum. This is an important serclimax in this district. Chamaecyparis and Cryptomeria palantation will be almost replaced by this, when careful protection is not adopted. Marshy places along the valley are covered by Alnus japonica-Cirsium Sieboldi-Carex omiana soeiation. Besides, a fragment of Zelkowa serrata-Acer nikoense-Disporum smilacinum sociation is found on the gravellous land of the valley bottom. They are fragments of other association or even alliance, of which the occurrences are restricted.
