The development of humus-iron podsol profiles, linked by radiocarbon dating and pollen analysis to vegetation history [Quercus petraea, Quercus robur, soil, forest]

• Published in: Oikos Vol. 36; no. 2
• Main Authors: Cruickshank, J.G, Cruickshank, M.M. (Belfast Univ. (UK). Dept. of Geography)
• Format: Journal Article
• Language: English
• Published: 01.03.1981
• ISSN: 0030-1299; 1600-0706
• DOI: 10.2307/3544453

The paper considers a possible development sequence leading to the formation of humus-iron podsols during a past cycle of pedogenesis, and gives an explanation for the survival of these soil profiles, currently associated with mixed oak-birch woodland at a site near Ballycastle in Northern Ireland. The vegetation of the study area is dominated by mature oak trees (both Q. petraea and Q. robur), many of which are 200-300 yr old. Pollen and soil profile analytical data from several sites on a centrally situated ridge in Breen Wood are examined, and used to reconstruct vegetation and soil history, radiocarbon dates providing a time scale. Pollen stratigraphy of surface mor humus (20-30 cm thick) provides a sensible record of vegetation changes within the Wood, and a number of samples from layers in the mor and from Bhs horizons below have been radiocarbon dated. As a result, circumstantial evidence is presented to suggest that the humus-iron podsols developed their characteristic Bhs horizons by down-profile movement of humus during two separate heath phases of forest clearances, initiated respectively about 2000 B.P. and 1400 B.P. Consequently, these profiles do not reflect current pedogenesis under mixed oak woodland, although present soil conditions help to preserve pre-existing profiles.