Bacterial community dissimilarity in soils is driven by long‐term land‐use practices

Aditi Sengupta,Parwinder S Grewal,Warren A Dick,Janani Hariharan

doi:10.1002/agg2.20031

Abstract

AbstractLand‐use practices impact soil microbial functionality and biodiversity, with reports suggesting that anthropogenic activities potentially result in reduced microbial functions and loss of species. The objective of this study was to assess the effect of long‐term (>50 yr) land use (natural forest and grassland, and agricultural land) on soil bacterial community structure. A high‐throughput sequencing‐by‐synthesis approach of the 16S rRNA gene was used to study bacterial community and predicted functional profiles of Alfisols, as affected by variables including land‐use (forest, grass, agricultural) and soil/crop management (rotation and tillage) in long‐term experimental plots in Hoytville, OH. The distribution of the abundant phyla was different across samples. No‐till soils showed higher diversity indices than the plow‐till (PT) soils. Ordinations across locations suggested that no‐till soils had distinctly different community structure compared with plow‐till soils, while crop rotation within the no‐till plot had highest number of taxa. Overall land use (forest, grass, agronomic treatment) and tillage (within agricultural soils) were found to be significant when evaluating bacterial community dissimilarity. Predictive functional profiles showed that the forest soil had greatest proportion of PICRUSt‐assignable gene functions followed by the no‐till and grassland soils whereas plow‐till soils had the lowest predicted gene abundances across all samples. The results provide a view of soil bacterial diversity and predictive functional capacity in long‐term land‐use and soil/crop management practices, with a potential to inform future experiments to increase our understanding of long‐term impacts of land use on microbial community structure and function.

Highlights

Rarefaction is not an ideal normalization method (Weiss et al, 2017) as it leads to losing rare operational taxonomic unit (OTU), but researchers acknowledge that alternatives to rarefying have not been sufficiently developed
We found that bacterial communities in agricultural soils, forest, and grass areas were diverse and impacted by long-term land use, despite the soil types being similar across all the land use practices
The results are in accordance with vast previous research that show land-use impacts soil microbial diversity

Summary

Introduction

Soil microorganisms contribute to crucial ecological processes like decomposition of organic matter, regulation of greenhouse gas fluxes, breakdown of xenobiotic compounds, biogeochemical cycling of nutrients, plant disease suppression, and plant growth (Garbeva, van Veen, & van Elsas, 2004; Nannipieri et al, 2003). Structure (Babujia, Silva, Nogueira, & Hungria, 2014; Potthoff et al, 2006), crop residue accumulation from notillage (Ceja-Navarro et al, 2010; Mathew, Feng, Githinji, Ankumah, & Balkcom, 2012), leaf litter decomposition from forests (Chapman, Newman, Hart, Schweitzer, & Koch, 2013; Purahong et al, 2014), and biomass accumulated on surface of grasslands (Garbeva, Postma, van Veen, & van Elsas, 2006; Lienhard et al, 2012; McCaig, Glover, & Prosser, 2001; Singh, Munro, Potts, & Millard, 2007) affect soil microbial community structure, diversity, biomass, and activity. Studies estimate that land-use and land-management practices account for 20–24% of total anthropogenic greenhouse gas emissions (Smith, Bustamante, Ahammad, Clark, & Dong, 2014). Conventional agriculture practices involve plowing and sowing, whereas conservation practices like no-tillage are characterized by sowing directly into the soil, while maintaining 30% crop residue present on the surface (Claasen, Bowman, McFadden, Smith, & Wallander, 2018). Based on estimates reported in 2012, about 40% of the total cropland (1.8 million ha) in Ohio is continuous no-tillage (Lessiter Media, 2014)

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