Ecological Research

, Volume 25, Issue 6, pp 1161–1169 | Cite as

Differences in distribution patterns around river confluences among hydrophilic vegetation groups

  • Takeshi Osawa
  • Hiromune Mitsuhashi
  • Hideyuki Niwa
  • Atushi Ushimaru
Original Article


In riparian areas, the distribution patterns of plant species are generally considered to depend on their flooding tolerance. Areas around river confluences are known to experience frequent and/or strong flooding events and provide diverse habitats for plants in riparian areas. However, the degree to which hydrophilic vegetation types increase their distribution around confluences may depend on their flooding tolerance. To test this hypothesis, we compared patch numbers and total areas of ten vegetation groups between confluences and single-flow areas. The vegetation groups were classified on the basis of life form and morphology of dominant species. Additionally, we compared total area of natural bare ground (an index of flooding disturbance) between confluences and single-flow areas. We found that patch numbers of annual grass, forb, and vine, perennial grass and forb, and riparian forest vegetation, as well as total areas of annual forb and vine, perennial grass and forb, bamboo and riparian forest vegetation, and natural bare ground, were greater around river confluences than in single-flow areas. On the other hand, patch numbers of shrub vegetation and total areas of annual grass, perennial vine, willow, and shrub vegetation decreased around confluences. These results suggest that confluences enhance diverse, but not all, types of habitat for hydrophilic vegetation. Thus, river confluences are a key element in maintaining diverse riparian vegetation.


Disturbance Flooding Vegetation type River ecosystem 



We thank the members of the ecology division of The Museum of Nature and Human Activities Hyogo for their valuable support. We also thank the members of the Laboratory of River Environment LLP for equipment and the RNER data set. We are grateful to the members of the Biodiversity Laboratory at Kobe University for their valuable support. Two anonymous reviewers and an editor provided many valuable comments during the review process.


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Copyright information

© The Ecological Society of Japan 2010

Authors and Affiliations

  • Takeshi Osawa
    • 1
    • 2
  • Hiromune Mitsuhashi
    • 3
  • Hideyuki Niwa
    • 4
  • Atushi Ushimaru
    • 1
  1. 1.Graduate School of Human Development and EnvironmentKobe UniversityKobeJapan
  2. 2.National Institute for Agro-Environmental ScienceTsukubaJapan
  3. 3.The Museum of Nature and Human Activities HyogoSandaJapan
  4. 4.Graduate School of Global Environmental StudiesKyoto UniversityKyotoJapan

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