Altitudinal changes in vegetation of tree, herb and fern species on Mount Norikura, central Japan

Abstract

Altitudinal changes in vegetation of tree species (>1.3m tall) and understory herb and fern species were studied at 13 sites between 800m and 3000m a.s.l. on Mount Norikura, central Japan. Based on the result of cluster analysis, altitudinal vegetation pattern was roughly classified by tree species into a montane deciduous broad-leaved forest type between 800m and 1600m a.s.l., a subalpine coniferous forest type between 1600m and 2500m a.s.l. and an alpine dwarf pine Pinus pumila scrub type between 2500m and 3000m a.s.l. Understory herb and fern species also changed with altitude, but the altitudinal change of vegetation of the understory species did not correspond with that of tree species. Especially, understory species formed a large cluster between 1400m and 2800m a.s.l., although a subcluster was definitely recognized between 1400m and 2000m a.s.l. because of the dominance of the dwarf bamboo Sasa senanensis. The number of tree species decreased with increasing altitude, but the number of understory herb and fern species did not decrease. Species diversity, expressed as the Shannon-Wiener H' index and Simpson's index (1-D), of tree and herb species tended to decrease between 1400m and 2000m a.s.l. because S. senanensis excluded the other plants. Therefore, this study suggests that altitudinal changes in vegetation differed between taxonomic groups, such as tree species and understory herb and fern species, and the species diversity is determined not only by altitude, but also by S. senanensis.