Linking soil N₂O emissions with soil microbial community abundance and structure related to nitrogen cycle in two acid forest soils

Aims Tree species and seasonal change influence N 2 O flux and microbial communities, but the mechanisms are unclear. We studied N 2 O flux in soils planted with slash pine and oil-seed camellia trees. We sampled on typical days of the four seasons. We tested whether N-cycling communities respond more to tree species or seasonal change. We assessed how tree species affect N 2 O flux. Methods We used qPCR and RFLP to determine abundance and community composition of amoA -containing bacteria (AOB) and archaea (AOA), and denitrifiers that contain the narG , nirK , nirS , and nosZ genes. Results N 2 O flux rate and soil characteristics varied significantly between forest soils and sampling seasons. Abundance of all detected genes, but not of the nirS gene, was significantly affected by tree species. Differences in gene abundance between days in different seasons were found only for narG , nirK, and nosZ . Functional microbial community composition in the soil varied between the tree species for most of the genes studied, but varied, not significantly, slightly among sampling days. Differences in the abundance and community composition of nitrifiers and denitrifiers between tree species depended on soil concentration of NH 4 + , NO 3 − , and dissolved organic carbon (DOC). N 2 O flux rate was affected by community composition, but not abundance of nitrifiers and denitrifiers. Temperature, NO 3 − , and DOC concentrations significantly affected N 2 O flux. Conclusions Tree species influenced N 2 O flux more than seasonal change, by altering community composition and environmental factors rather than nitrifier/denitrifier abundance.