ANDIC SOIL PROPERTIES OF SPODOSOLS IN NONVOLCANIC MATERIALS OF SOUTHEAST ALASKA

Andic properties are typical of soils in volcanic materials, including those in southeast Alaska. Nonvolcanic materials, however, predominate in southeast Alaska, yet andic properties are common in Spodosols throughout the area. A well-drained, forested Spodosol was sampled in Holocene beach deposits with no more than traces of volcanic glass. The pedon has a thin E horizon and a spodic horizon that has andic soil properties typical of Spodosols in southeast Alaska. Acid-oxalate-extractable Al + (Fe/2) is 3.6% in the Bh, 5.8% in the Bhs, and 6.4% in the Bs horizon. Soil bulk densities are low and P retention is >90% in all subhorizons of the spodic horizon. The soil is an Andic Humicryod. About one-third of the Spodosols in nonvolcanic materials of southeast Alaska meet the andic or aquandic subgroup requirements of Haplocryods, Humicryods, or Cryaquods. In addition, other Spodosols have andic properties in subhorizons of a spodic horizon < 25 cm thick and some are in lithic subgroups. Rapid weathering and leaching, high organic matter content, and cool temperatures promote the accumulation of amorphous Al and Fe compounds in the perudic soils of southeast Alaska.