Linked from
The 18 pages that link to Soil horizon, each with the reason it gives.
PedosphereBroader topic: Horizons show how processes organize the pedosphere vertically.
PaleosolBroader topic: Horizon sequences preserve the layered profile used to identify a paleosol.
Soil profileBroader topic: Profiles are described by the sequence of horizons they contain.
Soil scienceBroader topic: Horizons record soil-forming processes at different depths.
Soil surveyBroader topic: Horizon boundaries and features help classify and map soil bodies.