Pyrogenic carbon content and dynamics in top and subsoil of French forests

Abstract

Pyrogenic carbon (PyC) may leave the soil surface where it is deposited, either through degradation, lateral transport or transfer within the profile. However, PyC has been seldom measured in the subsoil. We estimated the quantity and molecular composition of PyC in the topsoil and subsoil of 22 French forests with diverse soil types and vegetation cover. While the absolute PyC content decreased with depth, its proportion to the soil organic carbon remained constant or tended to increase. The benzene polycarboxylic acids pattern indicated that more condensed structures were found in the subsoil. Our results show that PyC transfers through the soil profile, probably as soluble fraction, and tends to accumulate in the subsoil, specifically in podzolic soils.