Effects of soil chemical characteristics and water regime on denitrification genes (nirS, nirK, and nosZ) abundances in a created riverine wetland complex

Abstract The impacts of site-specific characteristics, such as wetland type, water regime, and soil chemical parameters, on the abundance of denitrifying genes encoding nitrite ( nirS and nirK ) and nitrous oxide ( nosZ ) reductases, and their proportions in a bacterial community were investigated in a river diversion wetland complex using quantitative real time polymerase chain reaction. The water regimes of the wetlands had the greatest effect on all denitrification gene parameter values, except nirK abundance. While the proportion of nirS genes dominated other targeted genes, and their abundance and proportion in bacterial community was highest in constantly flooded areas, nosZ and nirK gene proportions were highest in occasionally flooded areas. Environmental factors had different effects on the abundances and proportions of nirS , nirK , and nosZ genes. The abundance of the nirS gene and ratio of nirK and nirS genes were affected by soil pH, and nirK gene proportions in the bacterial community were related to the NO 3 -N concentration in soil; however, the nature of these relationships varied in different wetlands and transitional areas, respectively. This finding suggests that microbes related to denitrification in soils of different wetland types do not respond similarly to the same environmental variables.