Abstract
Early colonization and succession of soil microbial communities are essential for soil development and nutrient accumulation. Herein we focused on the changes in pioneer prokaryotic communities in rhizosphere and bulk soils along the high-elevation glacier retreat chronosequence, the northern Himalayas, Tibetan Plateau. Rhizosphere soils showed substantially higher levels of total organic carbon, total nitrogen, ammonium, and nitrate than bulk soils. The dominant prokaryotes were Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Crenarchaeota, Bacteroidetes, and Planctomycetes, which totally accounted for more than 75% in relative abundance. The dominant genus Candidatus Nitrososphaera occurred at each stage of the microbial succession. The richness and evenness of soil prokaryotes displayed mild succession along chronosequene. Linear discriminant analysis effect size (LEfSe) analysis demonstrated that Proteobacteria (especially Alphaproteobacteria) and Actinobacteria were significantly enriched in rhizosphere soils compared with bulk soils. Actinobacteria, SHA_109, and Thermoleophilia; Betaproteobacteria and OP1.MSBL6; and Planctomycetia and Verrucomicrobia were separately enriched at each of the three sample sites. The compositions of prokaryotic communities were substantially changed with bulk and rhizosphere soils and sampling sites, indicating that the communities were dominantly driven by plants and habitat-specific effects in the deglaciated soils. Additionally, the distance to the glacier terminus also played a significant role in driving the change of prokaryotic communities in both bulk and rhizosphere soils. Soil C/N ratio exhibited a greater effect on prokaryotic communities in bulk soils than rhizosphere soils. These results indicate that plants, habitat, and glacier retreat chronosequence collectively control prokaryotic community composition and succession.
Highlights
Glaciers cover ∼10% of the land surface of the Earth and are rapidly shrinking in most parts of the world, leading to significant impacts on terrestrial ecosystems (Jain, 2014; Milner et al, 2017)
The dominant phyla across all samples were Proteobacteria (21.95%), Actinobacteria (18.11), Acidobacteria (9.50%), Chloroflexi (7.9%), Crenarchaeota (6.81%), Bacteroidetes (6.27%), and Planctomycetes (5.69%), accounting for more than 75% of the total prokaryotic sequences
The phyla Proteobacteria, especially class Alphaproteobacteria, and Actinobacteria were significantly enriched in rhizosphere soil; Acidimicrobiia and Gemmatimonadetes were significantly enriched in bulk soil (Figure 5A)
Summary
Glaciers cover ∼10% of the land surface of the Earth and are rapidly shrinking in most parts of the world, leading to significant impacts on terrestrial ecosystems (Jain, 2014; Milner et al, 2017). The biological, physical, and chemical characteristics of the deglaciated soil are closely linked to the deglaciation chronosequence (Bernasconi et al, 2011). These newly exposed substrates represent natural laboratories to study primary succession of the microbial community and the concomitant development of new soil (Schuette et al, 2010). The establishment of pioneering microbial communities is the key determinant of deglaciated soil development and its ecosystem function and stability (Schmidt et al, 2008; Kabala and Zapart, 2012) and facilitates the colonization of pioneering plants (Bradley et al, 2014). Cyanobacterial diversity and evenness increase in young deglaciated soils (
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