Melanic Epipedon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 25

Table 4.3 Factors influencing the development of the melanic horizon
Area Factor Reference

Climate

Nilgiri Hills,
India

Climatic change induces complexation of
organic acids with Fe oxides to produce
non-allophanic melanic

Caner et al. ( 2000 )

Italy,
New Zealand

Abundant rainfall and sustained soil moisture
favors melanic

Parfitt et al. ( 1983 ) and Vacca
et al. ( 2009 )

No. CA Fire important for accumulation organic

matter

Takahashi et al. ( 1994 )

Ecuador Climate influences leaching regime and SOM

decomposition

Zehetner et al. ( 2003 )

New Zealand Ustic soil-moisture regime and good drainage

important

Parfitt et al. (1982) and Parfitt
and Kimble ( 1989 )

Organisms

Japan Grassy vegetation releases A-type humic

acids that complex with Al

Egashira et al. ( 1997 )

Ecuador Paramo vegetation releases A-type humic

acids that complex with Al

Poulenard et al. ( 2003 )

No. CA Melanic forms under coniferous forest as well

as grassland

Takahashi et al. ( 1994 )

Relief

Bolivia, India,
Ecuador

Melanic forms at high elevations in tropical
mountains (2,000-4,500 m)

Egashira et al. ( 1997 ), Caner
et al. ( 2000 ), Poulenard
et al. ( 2003 ) and Zehetner
et al. ( 2003 )

Parent material

New Zealand Allophanic materials especially conducive to

forming melanic

Parfitt et al. ( 1983 )

Bolivia, India,
New Zealand,
Ecuador

Non-allophanic melanic common on basalts
and basic and ultrabasic materials

Egashira et al. ( 1997 ), Caner
et al. ( 2000 ), Poulenard
et al. ( 2003 ) and Vacca
et al. ( 2009 )

Time Parent material

Ecuador Melanic forms in 3,000 yr Poulenard et al. ( 2003 )

4.6 Genesis of the Melanic Epipedon

The melanic epipedon occurs in soils enriched in volcanic ash or other highly
weathered volcanic materials. The cool moist conditions lead to the establishment
of coniferous forests in western USA. The melanic epipedon is formed from the
complexation of humic acids with amorphous and organic-bound Al (Parfitt
et al. 1983 ; Shoji et al. 1988 ). These compounds have a net positive charge that
enable fixation of phosphate and other anions.