Effects of vegetation regime on denitrification potential in two tropical volcanic soils

Effects of vegetation and nutrient availabilityon potentail denitrification rates were studied in twovolcanic, alluvial-terrace soils in lowland Costa Rica thatdiffer greatly in weathering stage and thus in availabilityof P and base cations. Potential denitrification rates weresignificantly higher in plots where vegetation had beenleft undisturbed than in plots where all vegetation hadbeen removed continuously, and were higher on the lessfertile of the two soils. The potential denitrification rateswere correlated strongly with respiration rates, levels ofmineralizable N, microbial biomass, and moisture con-tent, and moderately well with concentrations of extract-able NH4 , Kjeldahl N, and total C. In all plots,Jenitrification rates were stimulated by the removal of02 and by the addition of glucose but not by the addi-tion of water or NO3.
Key words: Denitrification — Soil respiration — Nitrousoxide — Tropical volcanic soils — Microbial biomass