Compaction stimulates denitrification in an urban park soil using ¹⁵N tracing technique.

Soils in urban areas are subjected to compaction with accelerating urbanization. The effects of anthropogenic compaction on urban soil denitrification are largely unknown. We conducted a study on an urban park soil to investigate how compaction impacts denitrification. By using (15)N labeling method and acetylene inhibition technique, we performed three coherent incubation experiments to quantify denitrification in compacted soil under both aerobic and anaerobic conditions. Uncompacted soil was set as the control treatment. When monitoring soil incubation without extra substrate, higher nitrous oxide (N2O) flux and denitrification enzyme activity were observed in the compacted soil than in the uncompacted soil. In aerobic incubation with the addition of K(15)NO3, N2O production in the compacted soil reached 10.11 ng N h(-1) g(-1) as compared to 0.02 ng N h(-1) g(-1) in the uncompacted soil. Denitrification contributed 96 % of the emitted N2O in the compacted soil and 36 % of the emitted N2O in the uncompacted soil; total denitrification rate was higher in the compacted soil (up to 79.35 ng N h(-1) g(-1)) than in the uncompacted soil (0.11 ng N h(-1) g(-1)). Under anaerobic incubation with the addition of K(15)NO3, no statistical difference in total N losses and (15)N-(N2O+N2) flux between the uncompacted soil and the compacted soil was detected. Compaction promoted soil denitrification and may impact urban N biogeochemical cycling.