Implications of wetland degradation for the potential denitrifying activity and bacterial populations with nirS genes as found in a succession in Qinghai-Tibet plateau, China

Abstract

Alpine wetland in the Zoige Plateau has suffered from serious degradation during the last 30 years due to global climate change and anthropogenic impact. Denitrification is a key nitrogen removal process which can be performed by different microorganisms, including bacteria harboring nirS-genes. In this study, a degradation succession was used to study the effect on potential denitrification activity (PDA) and on bacterial communities harboring nirS genes. Based on the determination of the PDA, the abundance, structural diversity, and phylogenetic identity of the soil bacteria with nirS genes were further assessed by qPCR, terminal restriction fragment length polymorphism (T-RFLP), and DNA-sequencing, respectively. The results showed that soil PDA ranged from 8.78 to 52.77 ng N2O-N g−1 dry soil h−1, being lowest in sandy soil and highest in swamp soil. The abundance of nirS genes (copies g−1 soil) were also the lowest in the sandy soil while highest in the swamp soil. The average Shannon-Wiener diversity index of the nirS denitrifying bacterial structural ranged from 2.20 in the meadow soil to 3.07 in the swamp soil. Redundancy analysis (RDA) showed that the nirS denitrifying bacterial community correlated with soil water content and available phosphorus, with water content as the major factor in shaping the nirS denitrifying bacterial community. The results of this study suggest that the wetland degradation would decrease soil PDA, and abundance and structural diversity of the denitrifying bacteria with nirS genes. These findings can contribute to support a theoretical foundation for predicting the potential influences of wetland degradation on soil denitrifying bacteria in alpine wetlands.