Vesicular-arbuscular mycorrizae for dating multiple paleosols and carbon loss rate determination

A promising technique for dating paleosols is reported based on radiocarbon (C-14) dating of asexual spores from vesicular-arbuscular mycorrizae (VAM). The soils are dispersed in water and some 6000-8000 spores separated by hand picking under a low power microscope. The dried spores are then dated by accelerator mass spectroscopy (AMS). A chronosequense of closely superimposed paleosols from an arctic/alpine meadow soil, northern Sweden, was dated and the long-term (i.e., over a millennium time-span) organic carbon loss rate determined. A very low carbon loss rate was obtained, 4.7 x 10(-4) +/- 9.2 x 10(-5) year(-1). It is argued that this approach is likely to give a better estimate for long-term loss than litter-bag studies covering a couple of decades. (C) 2000 Elsevier Science B.V. All rights reserved.