Abstract

Nitrous oxide (N2O) is a potent greenhouse gas produced during denitrification, a process that includes several genes coding enzymes responsible for nitrogen (N) forms transformations. In volcanic ash soils of southern Chile, fertilization had increased over the last 10 years with implications for N2O emissions. Despite this, little is still known about potential denitrification and the presence of denitrifying genes. In this study we report the abundance of denitrifying genes and a basal characterization of microbial communities in five volcanic ash soils with different levels of organic matter. The denitrifying genes determination showed that nosZI predominated over nirK and nirS in all soils suggesting a complete denitrification pathway, which would explain low N2O losses in such soils. Estimation of total microorganisms studies using 16S and 18S rRNA showed that in these soils bacteria (10(9)) was most abundant over archaea and fungi (10(7); p0.05). Sequences of DNA obtained by denaturant gradient gel electrophoresis (DGGE) indicated that Firmicutes, Acidobacteria and Proteobacteria are the main bacterial classes represented in Andisoils (33, 28 and 23%, respectively) but with a lower diversity. More detailed studies about denitrifiers, gene-activity relationship and N2O emissions are required.