Disappearance of Alic Melanudands and Alic Fulvudands in the Kitakami Mountains, northeastern Japan.

摘要

Andisols of the southern part of the Kitakami mountain range are strongly influenced by long-range eolian dust deposited during the Quaternary. These Andisols are enriched with crystalline clay minerals, KCI-extractable Al and organic C. Under the seventh edition of Keys to Soil Taxonomy, they were classified variously as Alic Melanudands, Alic Fulvudands, Alic Hapludands, or Alic Pachic Melanudands. However, with the publication of the eighth edition of Keys to Soil Taxonomy, all the Alic subgroups of Melanudands and Fulvudands were removed whereas those subgroups of Hapludands were retained. The change was carried forward into the second edition of Soil Taxonomy (Soil Survey Staff, 1999) and the latest Keys to Soil Taxonomy (i.e., 10th edition). We present some selected chemical properties and the andic soil properties of 13 pedons of the Kitakami Mountain range to expose the inconsistency in the classification of Alic Andisols. The amount of KCI-extractable Al in the Melanudands and Fulvudands ranged from 0.1 to 13.4 cmol(+) kg-1. Those Melanudands and Fulvudands that satisfied the Alic subgroup requirements because they contained >2.0 cmol(+) kg-1 KCI-extractable Al in the prescribed horizons are currently classified as Typic Melanudands or Typic Fulvudands. On the contrary, the Hapludands that previously met the Alic subgroup requirements in the earlier editions of Soil Taxonomy are still classified as Alic Hapludands. We also emphasize the need to create the Alic Pachic Fulvudands subgroups.