Melanic Epipedon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 24

Table 4.2 Classification of soil series containing a melanic epipedon

No. of soil
series Order Suborder Great group Subgroups

Andisols Aquands Melanaquands Typic (1) 1

Cryands Fulvicryands Eutric (2), Pachic (2), Typic (1), Vitric (1) 6

Udands Fulvudands Aquic (2), Eutric (1), Pachic (5), Typic (1) 9

Melanudands Pachic (4) 4

Xerands Melanoxerands Pachic (4), Typic (2) 6

Vitrixerands Humic (3) 3

29

Fig. 4.2 Counties in
western USA containing
soils with a melanic
epipedon

4.5 Factors Influencing the Development
of the Melanic Epipedon

The key factors affecting the development of the melanic epipedon are highly
weathered alluvium, colluvium, and residuum derived from andesite and conditions
that lead to the accumulation of abundant organic C (Table 4.3 ). These include
abundant rainfall (1,500 mm/yr), cool temperatures, and dense coniferous forests.