Soil depth matters: shift in composition and inter-kingdom co-occurrence patterns of microorganisms in forest soils

FEMS Microbiology Ecology, vol. 97

Abstract

Soil depth represents a strong physiochemical gradient that greatly affects soil-dwelling microorganisms. Fungal communities are typically structured by soil depth, but how other microorganisms are structured is less known. Here, we tested whether depth-dependent variation in soil chemistry affects the distribution and co-occurrence patterns of soil microbial communities. This was investigated by DNA metabarcoding in conjunction with network analyses of bacteria, fungi, as well as other micro-eukaryotes, sampled in four different soil depths in Norwegian birch forests. Strong compositional turnover in microbial assemblages with soil depth was detected for all organismal groups. Significantly greater microbial diversity and fungal biomass appeared in the nutrient-rich organic layer, with sharp decrease towards the less nutrient-rich mineral zones. The proportions of copiotrophic bacteria, Arthropoda and Apicomplexa were markedly higher in the organic layer, while patterns were opposite for oligotrophic bacteria, Cercozoa, Ascomycota and ectomycorrhizal fungi. Network analyses indicated more intensive inter-kingdom co-occurrence patterns in the upper mineral layer (0-5 cm) compared to the above organic and the lower mineral soil, signifying substantial influence of soil depth on biotic interactions. This study supports the view that different microbial groups are adapted to different forest soil strata, with varying level of interactions along the depth gradient.

Authors 6

1. Sunil Mundra corresponding

   University of Oslo · United Arab Emirates University

   Affiliation as printed

   Department of Biology, College of Science, United Arab Emirates University, Al-Ain, Abu-Dhabi, UAE

   Section for Genetics and Evolutionary Biology (EvoGene), Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway

2. O. Janne Kjønaas

   Norwegian Institute of Bioeconomy Research

   Affiliation as printed

   NIBIO, Department of Terrestrial Ecology, NO-1431 Ås, Norway

3. Luís Neves Morgado Aachen Naturalis Biodiversity Center

   Naturalis Biodiversity Center · University of Oslo

   Affiliation as printed

   Naturalis Biodiversity Center, 2300 RA Leiden, the Netherlands

   Section for Genetics and Evolutionary Biology (EvoGene), Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway

4. Anders Kristian Krabberød

   University of Oslo

   Affiliation as printed

   Section for Genetics and Evolutionary Biology (EvoGene), Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway

5. Yngvild Ransedokken

   Norwegian University of Life Sciences

   Affiliation as printed

   Faculty of Environmental and Natural Resource Management, Norwegian University of Life Sciences, NO-1432 Ås, Norway

6. Håvard Kauserud

   University of Oslo

   Affiliation as printed

   Section for Genetics and Evolutionary Biology (EvoGene), Department of Biosciences, University of Oslo, NO-0316 Oslo, Norway