Factors that shape the elevational patterns of plant diversity in the
Yatsugatake Mountains, Japan
Abstract
Elevation is involved in determining plant diversity in montane
ecosystems. This study examined whether the species distribution of
plants in the Yatsugatake Mountains, central Japan, substantiated
hypotheses associated with an elevational diversity gradient. Species
richness of trees, shrubs, herbs, ferns, and bryophytes was investigated
in study plots established at 200-m elevational intervals from 1800 to
2800 m. The changes in plant diversity (alpha and beta diversities,
plant functional types, and elevational ranges) with elevation were
analyzed in relation to climatic factors and elevational diversity
gradient hypotheses, that is, mass effect, mid-domain effect, and
Rapoport’s elevational rule. A comparison of alpha and beta diversities
revealed that different plant groups respond variably to elevation; the
alpha diversity of trees and ferns decreased, that of herbs increased,
whereas the alpha diversity of shrubs and bryophytes showed a U-shaped
relationship and a hump-shaped pattern. The beta diversity of shrubs,
herbs, and bryophytes increased above the subalpine–alpine transition
ecotone. In accordance with these changes, the dominance of evergreen
shrubs and graminoids increased above this ecotone, whereas that of
evergreen trees and liverworts decreased. None of the plant groups
showed a wide elevational range at higher elevations. These elevational
patterns of plant groups were explained by climatic factors, and not by
elevational diversity gradient hypotheses. These patterns were further
influenced by plant–plant interactions via competition for light
availability and physical habitat alternation.