I'm referring to something like this.
Entisols, inceptisols, and alfisols are three stages of soil development in temperate woodland and forest areas. The entisols are the most recently deposited, undeveloped soils, inceptisols are woodland soils in a moderate stage of development, and alfisols are fully developed woodland soils. Both inceptisols and alfisols have moderate to high nutrient content and moderate to high fertility.
Mollisols develop under temperate grasslands, tend to form a tall layer of soil, and are highly fertile.
Aridisols form in scrub vegetation under arid and semi-arid conditions and can have moderate to high nutrient content, but are at high risk of becoming salinized.
Hot, rainy climates produce highly weathered soils with low nutrient content. Ultisols are old soils, drained of nutrients, and oxisols represent a more advanced stage of this process. Weathering remnants and metal oxides are all that's left in the latter type of soil.
Cold regions produce different types of soil: in coniferous forests, the needle litter leaches nutrients from the soil and forms spodosols. Gilisols, meanwhile, form due to persistent freezing temperatures and contain permafrost within two meters of the surface.
Andisols are highly fertile soils produced by weathering of volcanic ash, and vertisols are also fertile and form through the weathering of limestone.
Histosols form out of organic matter in wet conditions, and include muck and peat.