Journal of Forest Research

, Volume 4, Issue 3, pp 207–215

Distribution and physical properties of colluvium and saprolite in unchannelized valleys in Tsukuba Experimental Basin, Japan

  • Yasuhiro Ohnuki
  • Shuichiro Yoshinaga
  • Shoji Noguchi
Original Articles

DOI: 10.1007/BF02762250

Cite this article as:
Ohnuki, Y., Yoshinaga, S. & Noguchi, S. J For Res (1999) 4: 207. doi:10.1007/BF02762250


To clarify the role of colluvium and saprolite in the hydrological processes of a forested mountain, the thickness and the physical properties of them were investigated at the Tsukuba Experimental Basin. We measured their thickness using a penetrometer, surveyed soil profiles, and analyzed undisturbed cylindrical samples for measurements of physical properties. At the zero-order basin, which is mainly covered by volcanic ash, the colluvium is mostly over 1.0 m in thickness. Along the axis of the basin, we found colluvium over 6.0 m thick. The saprolite thickness is heterogeneously distributed over the hillslopes and along the axis of the hollow, where it is rather thick. The physical properties of shallow colluvium, deep colluvium and saprolite, particularly bulk density and total porosity, are different. Thick colluvium and saprolite play an important role as a buffer against direct runoff.

Key words

colluviumphysical propertyporositysaproliteunchannelized valley

Copyright information

© The Japanese Forest Society and Springer 1999

Authors and Affiliations

  • Yasuhiro Ohnuki
    • 1
  • Shuichiro Yoshinaga
    • 2
  • Shoji Noguchi
    • 3
  1. 1.Kyushu Research CenterForestry and Forest Products Research InstituteKumamotoJapan
  2. 2.Shikoku Research CenterForestry and Forest Products Research InstituteKochiJapan
  3. 3.Forestry and Forest Products Research InstituteIbarakiJapan