SPATIAL HETEROGENEITY IN THE DISTRIBUTION OF DENITRIFYING BACTERIA ASSOCIATED WITH DENITRIFICATION ACTIVITY ZONES

Denitrifying enzyme activity (DEA) in artificially established denitri fication activity zones was, on average, 3.5-fold greater than in bulk soil. Denitrifier biomass was between 1 and 4 orders of magnitude gre ater in activity zones. Denitrifier specific activity was lower in act ivity zones and more similar to specific activity values reported for pure cultures of denitrifying bacteria added to soil. Measurements of DEA and biomass carried out on a homogeneous subsample derived from a soil core containing a denitrification activity zone will overestimate the DEA and biomass of the bulk soil and underestimate the DEA and bi omass of the activity zone.