BIODEGRADABLE DISSOLVED ORGANIC-CARBON IN SEEPAGE WATERS FROM 2 FOREST SOILS

Dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC) and phenols were measured in water leached from two forest soi ls (a mottled brown soil and a podzolic pseudogley) collected during a 3-day artificial rain experiment. Different behaviours of the soils w ith regard to their relationships with these compounds were observed. DOC removal from brown soil decreased over the 3-day experiment follow ing a two-step evolution (first decreasing, then stabilizing), dependi ng on BDOC initial stock. DOC concentration from podzolic pseudogley l eachates increased from day 1 to day 3 and was poor in BDOC. A major p art of the DOC removed from this soil was therefore refractory carbon. A Spearman rank correlation test showed a highly significant relation ship between this fraction of DOC and phenols. Differences between the se two types of soil as for their organic matter are well known. Never theless, BDOC measurements are more satisfactory than chemical analyse s because they give information on DOC quality as it directly relates to microbial populations themselves.