Abstract
Vast areas of land in the forest-steppe of West Siberia are occupied by birch forests, the most common ecosystems there. However, currently, little is known about the microbiome composition in the underlying soil, especially along a sequence of soil genetic horizons. The study aimed at inventorying microbiome in genetic horizons of a typical Phaeozem under undisturbed birch forest in West Siberia. Bacteria and fungi were studied using 16S rRNA genes’ and ITS2 amplicon sequencing with Illumina MiSeq. Proteobacteria and Acidobacteria together accounted for two-thirds of the operational taxonomic units (OTUs) numbers and half of the sequences in each genetic horizon. Acidobacteria predominated in eluvial environments, whereas Proteobacteria, preferred topsoil. The fungal sequences were dominated by Ascomycota and Basidiomycota phyla. Basidiomycota was the most abundant in the topsoil, whereas Ascomycota increased down the soil profile. Thelephoraceae family was the most abundant in the A horizon, whereas the Pyronemataceae family dominants in the AEl horizon, ultimately prevailing in the subsoil. We conclude that soil genetic horizons shape distinct microbiomes, therefore soil horizontation should be accounted for while studying undisturbed soils. This study, representing the first description of bacterio- and mycobiomes in genetic horizons of the Phaeozem profile, provides a reference for future research.
Highlights
Soils are a major component of terrestrial ecosystems
In soil under a secondary natural forest of Betula albosinensis in China, Acidobacteria’s relative abundance was found to reach its maximum (63%) at 40–60 cm soil depth [29], which was not the case in our study where Acidobacteria abundance reached its maximum of 37% in the AEl horizon, i.e., 5–21 cm layer (Figure 1b). In contrast to those results, we found no significant correlation between Acidobacteria and Proteobacteria abundance and dissolved organic carbon
To the best of our knowledge, here we present the first study describing changes in the soil bacteriobiome and mycobiome diversity along the sequence of genetic horizons of the undisturbed Phaeozem pedon under birch forest, a widely spread ecosystem throughout the forest-steppe zone in the south of West Siberia, using high-throughput sequencing techniques
Summary
Soils are a major component of terrestrial ecosystems. Developed soils are highly structured media representing an integrated system of specific soil environments, i.e., soil genetic horizons, developed by soil genesis under the effect of soil-forming factors (parent material, climate, relief, biota, and time) and sustained by many elementary soil processes. I.e., the organisms less than 5000 μm3 [1] in body volume, are important players in many of the elementary soil processes, decomposing plant material, cycling nutrients, controlling pests, supplying water and nutrients to plants, contributing to shaping specific sequence of soil genetic horizons in a soil profile. Specific soil properties within genetic horizons can shape the composition of its microbial assemblage [2]. Forests dominated by white birch form large ecosystems in temperate biomes. Vast areas of land in the forest-steppe of West Siberia are covered by birch forests, the most common and still relatively undisturbed ecosystems there
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