Belowground biodiversity in mountain soils has received limited attention, as the heterogeneity and inaccessibility of these ecosystems make their study and the formulation of broad conclusions challenging. Remoteness and considerable variations in soil conditions over short distances further add to these difficulties. Yet, recent years have seen important progress in our understanding of these ecosystems. With our literature review, we provide the first global synthesis of published research on microorganisms, cryptogams, and invertebrate fauna in mountain soils above the treeline.
Drawing from nearly 1,400 publications and the expertise of 37 mountain soil scientists worldwide, we summarized diversity and distribution patterns in alpine soils. Our findings show an elevation-dependent decline in faunal diversity, while cryptogams initially increase before decreasing towards the nival belt. The diversity of prokaryotes shows unpredictable, often site-specific reactions, whereas fungal diversity is closely linked to plant associations. We also identified research hotspots in the European Alps and Central Asia, alongside significant taxonomic gaps, particularly in biocrusts, soil protists, and soil fauna. Our findings further revealed that research on alpine soils primarily focuses on the effects of climate change, land-use change, and pollution.
Finally, we emphasize the need to address spatial, taxonomic, and thematic biases, expand research efforts in understudied regions, and strengthen political commitments and international collaboration to enhance the protection and sustainable management of mountain soils.