Vertical distribution of tree fine roots in the tephra profile with two buried humic soil layers

Surface humic soils, where fine roots are mainly distributed, can be accidentally buried due to coverage by deposits such as volcanic ash. This buried humic soil may influence the vertical distribution of fine roots because soil organic matter strongly affects soil functions. However, fine root distributions in buried humic soils are little understood. In order to elucidate the effects of buried humic soils on fine root distribution, we investigated fine root biomass and soil characteristics in a soil profile down to 3.3 m with two buried humic soils formed by tephra in Tomakomai, Hokkaido, Japan. In this profile, fine root biomass decreased with soil depth, but increased in buried humic soils that had higher soil total carbon (C) content and higher fine soil ratio than buried nonhumic soils. These results lead us to surmise a preferential development of active fine roots in buried humic soils rich in organic C rather than nonhumic soils.