Distribution of microbial biomass down soil profiles under regenerating woodland

Adenosine triphosphate (ATP) was measured in soil profiles taken from two areas of deciduous woodland on Rothamsted Farm, one near neutral, one acidic. Biomass carbon (C) was calculated from these measurements. Comparison of the results with others taken from the literature showed that an exponential function m=e−(rbd) gave a close fit to the assembled data for the top metre of mineral soil, where m is biomass C, expressed as a fraction of that in the topsoil, d the depth (in cm, measured downwards from the middle of the topmost sampling layer) and rb a constant, in cm−1. The mean value for rb for 12 soils (including our two) is 0.046 cm−1, with a SD of ±0.0078.