Soil biochar amendment shapes the composition of N₂O-reducing microbial communities

Johannes Harter, Pascal Weigold, Mohamed El-Hadidi, Daniel H. Huson, Andreas Kappler, Sebastian Behrens

Geomicrobiology & Microbial Ecology, Center for Applied Geosciences, University of Tuebingen, Sigwartstr. 10, 72076 Tuebingen, Germany.

Abstract

Soil biochar amendment has been described as a promising tool to improve soil quality, sequester carbon, and mitigate nitrous oxide (N₂O) emissions. N₂O is a potent greenhouse gas. The main sources of N₂O in soils are microbially-mediated nitrogen transformation processes such as nitrification and denitrification. While previous studies have focused on the link between N₂O emission mitigation and the abundance and activity of N₂O-reducing microorganisms in biochar-amended soils, the impact of biochar on the taxonomic composition of the nosZ gene carrying soil microbial community has not been subject of systematic study to date. We used 454 pyrosequencing in order to study the microbial diversity in biochar-amended and biochar-free soil microcosms. We sequenced bacterial 16S rRNA gene amplicons as well as fragments of common (typical)nosZ genes and the recently described ‘atypical’ nosZ genes. The aim was to describe biochar-induced shifts in general bacterial community diversity and taxonomic variations among the nosZ gene containing N2O-reducing microbial communities. While soil biochar amendment significantly altered the 16S rRNA gene-based community composition and structure, it also led to the development of distinct functional traits capable of N₂O reduction containing typical and atypical nosZ genes related to nosZ genes found in Pseudomonas stutzeri and Pedobacter saltans, respectively. Our results showed that biochar amendment can affect the relative abundance and taxonomic composition of N₂O-reducing functional microbial traits in soil. Thus these findings broaden our knowledge on the impact of biochar on soil microbial community composition and nitrogen cycling.

Graphical abstract

Keywords: Nitrogen cycle; Biochar; Nitrous oxide emission; nosZ genes; Soil microbial community; 454 amplicon pyrosequencing.