Riparian land-use systems impact soil microbial communities and nitrous oxide emissions in an agro-ecosystem

Tolulope G Mafa-Attoye; Megan A Baskerville; Enoch Ofosu; Maren Oelbermann; Naresh V Thevathasan; Kari E Dunfield

doi:10.1016/j.scitotenv.2020.138148

Riparian land-use systems impact soil microbial communities and nitrous oxide emissions in an agro-ecosystem

Sci Total Environ. 2020 Jul 1:724:138148. doi: 10.1016/j.scitotenv.2020.138148. Epub 2020 Mar 24.

Authors

Tolulope G Mafa-Attoye¹, Megan A Baskerville², Enoch Ofosu¹, Maren Oelbermann², Naresh V Thevathasan¹, Kari E Dunfield³

Affiliations

¹ School of Environmental Sciences, University of Guelph, Canada.
² School of Environment, Resources and Sustainability, University of Waterloo, Canada.
³ School of Environmental Sciences, University of Guelph, Canada. Electronic address: dunfield@uoguelph.ca.

PMID: 32259726
DOI: 10.1016/j.scitotenv.2020.138148

Abstract

Riparian buffer systems (RBS) are considered a best management practice (BMP) in agricultural landscapes to intercept soil nitrogen (N) and phosphorus (P) leaching and surface runoff into aquatic ecosystems. However, these environmental benefits could be offset by increased greenhouse gas (GHG) emissions, including nitrous oxide (N₂O). The main sources of N₂O in soil are linked to processes which are mediated by soil microbial communities. These microorganisms play crucial roles in N-cycling and in the reduction of nitrate to N₂, and N₂O gases. This study was conducted to determine the abundance and diversity of microbial communities and functional genes associated with N-cycling and their influence on N₂O emissions in different riparian land-use: undisturbed natural forest (UNF), rehabilitated site (RH), grass buffer (GRB), and an adjacent agricultural land (AGR). Soil was sampled concurrently with N₂O emissions on July 13, 2017. DNA was extracted and used to target key N-cycling genes for N-fixation (nifH), nitrification: (amoA), and denitrification (nirS, nirK, and nosZ) via quantitative PCR, and for high throughput sequencing of total bacterial and fungal communities. Non-metric multidimensional scaling (NMDS) was used to examine microbial community composition and indicated significant differences in bacterial (p < 0.001) and fungal (p < 0.0085) communities between sites. Bacterial abundance differed significantly (p = 0.0005) between RBS and AGR sites with the highest populations occurring in the UNF (2.1 × 10¹⁰ copies g^-1 dry soil), and lowest in AGR (5.3 × 10⁹ copies g^-1 dry soil). However, the AGR site had the highest ammonia-oxidizing bacteria (AOB) abundance, indicating that nitrification is highest at this site. The abundance of the nosZ gene was highest in RH and GRB demonstrating the capacity for complete denitrification at these sites, lowering measured N₂O. These results suggest N-cycling microbial community dynamics differ among RBS and are influencing N₂O emissions in the sites investigated.

Keywords: Denitrification; Ecosystem services; Illumina mi-seq; Land management; Microbial diversity; N(2)O emission; Nitrification.

MeSH terms

Denitrification
Microbiota*
Nitrification
Nitrous Oxide / analysis*
Soil
Soil Microbiology

Substances

Soil
Nitrous Oxide