Effect of fluvial and geomorphic disturbances on habitat segregation of tree species in a sedimentation-dominated riparian forest in warm-temperate mountainous region in southern Japan |
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| Authors: | Hiroka Ito Satoshi Ito Tamotsu Matsui Tomomi Marutani |
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| Institution: | (1) United Graduate School of Agricultural Science, Kagoshima University, Kagoshima, Japan;(2) Division of Forest Science, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuen Kibanadai Nishi, Miyazaki 889-2192, Japan;(3) Faculty of Agriculture, Hokkaido University, Sapporo, Japan |
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| Abstract: | We investigated habitat segregation and patterns of species diversity of trees in relation to variations in fluvial and geomorphic
disturbances (erosion or sedimentation) along a longitudinal stream gradient from V-shaped valley to alluvial fan and between
valley and adjacent hill slopes in a warm-temperate mountainous riparian forest in Kyushu, southwestern Japan. We longitudinally
divided the riparian area into four geomorphic zones: V-shaped valley (VV-zone), upper fan (UF-zone), middle fan (MF-zone),
and lower fan (LF-zone). We surveyed the distribution of tree species (diameter at breast height ≥3 cm) in the four riparian
zones and in additional plots on hill slopes (SL-zone) representing the broader, nonriparian forest matrix. Detrended correspondence
analysis ordination demonstrated variations in species composition along the longitudinal stream gradient. Species guild analysis
based on the detection of the species preferred zone by a bootstrap method revealed a guild structure corresponding to each
geomorphic zone. The four riparian zones were differentiated from the SL-zone by having a low proportion of SL-guild species
and a high proportion of infrequent species that were characterized by deciduous leaf habit. The LF-zone was the most differentiated
and was characterized by low tree density and specialist species established on the flat and unstable soil surface created
by frequent deposition of sediment. The UF- and MF-zones were characterized by a high tree density and species richness (particularly
of infrequent species) established on the stable ground surface of a high alluvial terrace. Microsite heterogeneity produced
by channel formation may also maintain a high species diversity in the riparian zones. |
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| Keywords: | Geomorphic guild Longitudinal stream gradient Microsite heterogeneity Site stability Species diversity |
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