The development of the humus layer in some woodlands of the English Lake District

A study of soil properties in some woodland sites in the English Lake District reveals two very different trends in both surface and profile development, on similar parent material. Under the prevailing high rainfall, topography appears to be the main factor determining whether a flushed brown earth with a mull humus layer and ash-sycamore-oak-hazel tree community will develop, or a leached podzolic brown earth with a mor humus layer and oak, birch and rowan as the characteristic trees. In both soil series the capacity of the surface horizons to adsorb cations increases in proportion to the amount of organic matter present. In the mulls this increased capacity is largely saturated by bases, in the mors by hydrogen ions. As the humus content rises, acidity and base saturation tend to maintain a fairly constant level in the mulls, while in the mors there is a steady rise in acidity coupled with a fall in base saturation.