The stage of soil development modulates rhizosphere effect along a High Arctic desert chronosequence

Abstract

In mature soils, plant species and soil type determine the selection of root microbiota. Which of these two factors drives rhizosphere selection in barren substrates of developing desert soils has, however, not yet been established. Chronosequences of glacier forelands provide ideal natural environments to identify primary rhizosphere selection factors along the changing edaphic conditions of a developing soil. Here, we analyze changes in bacterial diversity in bulk soils and rhizospheres of a pioneer plant across a High Arctic glacier chronosequence. We show that the developmental stage of soil strongly modulates rhizosphere community assembly, even though plant-induced selection buffers the effect of changing edaphic factors. Bulk and rhizosphere soils host distinct bacterial communities that differentially vary along the chronosequence. Cation exchange capacity, exchangeable potassium, and metabolite concentration in the soil account for the rhizosphere bacterial diversity. Although the soil fraction (bulk soil and rhizosphere) explains up to 17.2% of the variation in bacterial microbiota, the soil developmental stage explains up to 47.7% of this variation. In addition, the operational taxonomic unit (OTU) co-occurrence network of the rhizosphere, whose complexity increases along the chronosequence, is loosely structured in barren compared with mature soils, corroborating our hypothesis that soil development tunes the rhizosphere effect.

Variations in the Compositions of Soil Bacterial and Fungal Communities Due to Microhabitat Effects Induced by Simulated Nitrogen Deposition of a Bamboo Forest in Wetland

“…Both bacterial and fungal changes in phylum/class discriminant clades responded to changes in alpha diversity, especially those in the fungal community at the N60-N90 levels, thereby implying that the abundance of soil microorganisms below the class level varied with SND levels. This is consistent with the findings of Mapelli [57], which showed that bacterial community development in bulk soil vs. rhizosphere soil coincides with soil fertility gradients. In addition, we found that several clades, including the bacterial clades Planctomycetes, Verrucomicrobia, and Actinobacteria and the fungal clades Dothideomycetes, Atheliales, Tremellomycetes, and Mortierellales had a higher discriminant level (LDA scores of ≥4).…”

Rhizosheath microbial community assembly of sympatric desert speargrasses is independent of the plant host

“…Bacterial and fungal components interact to form complex microbial networks in the rhizosheath-root system of the three speargrass species. In contrast, in bulk sand, disconnected micro-habitats and the presence of higher numbers of dormant cells may explain the lower complexity and the identification of co-presence interactions only [ 62 ].…”

New Fusarium species from the Kruger National Park, South Africa

“…Nutrient content also increased from the top to the bottom of the slope which is consistent with the increase in CEC . Nutrient poor soils are also a driver of biological diversity and most likely influenced fungal diversity in these particular locations ( Havlicek and Mitchell 2014 , Mapelli et al 2017 ).…”