Nitrous Oxide Consumption Potentials of Well-drained Forest Soils in Southern Québec, Canada

Abstract

To establish the major controls on N 2 O consumption by forest soils, we conducted laboratory incubations of 16 samples from four soil types, two organic and two mineral, varying in overlying forest vegetation (sugar maple, American beech and eastern hemlock). The fastest potential consumption of N 2 O occurred under anoxic conditions with little soil nitrate and under elevated headspace N 2 O concentration. Potential N 2 O consumption rates were fastest in organic soils under hemlock and beech trees (111 and 75 ng N 2 O-N g −1 d −1 , respectively) compared to mineral soils under beech and maple trees (45 and 41 ng N 2 O-N g −1 d −1 ). Organic soils showed faster N 2 O consumption rates than mineral soils, possibly due to larger organic C levels and higher C:N ratios. Acetylene treatment confirmed that denitrification was the process underlying N 2 O consumption. These results suggest that soils regularly consume N 2 O with varying magnitude, most likely in anoxic microsites throughout the soil profile and that the potential for N 2 O consumption is larger in organic than in mineral forest soils.