Factors of mull and mor development in temperate grasslands

[First paragraph...]
The humus forms of soil profiles have been defined as the group of A horizons in which organic matter is concentrated (Barratt 1964). They are generally the first parts of soil profiles to respond to changes in soil-forming factors and they are particularly worthy of study in the temperate grasslands of Great Britain and New Zealand where grasslands have largely developed on former forest soils.