Metabarcoding data reveal vertical multi-taxa variation in topsoil
communities during the colonization of deglaciated forelands
Abstract
Ice-free areas are increasing worldwide due to the dramatic glacier
shrinkage and are undergoing rapid colonization by multiple lifeforms,
thus representing key environments to study ecosystem development. Soils
have a complex vertical structure. However, we know little about how
microbial and animal communities differ across soil depths and
development stages during the colonization of deglaciated terrains, how
these differences evolve through time, and whether patterns are
consistent among different taxonomic groups. Here, we used environmental
DNA metabarcoding to describe how community diversity and composition of
six groups (Eukaryota, Bacteria, Mycota, Collembola, Insecta,
Oligochaeta) differ between surface (0-5 cm) and relatively deep (7.5-20
cm) soils at different stages of development across five Alpine
glaciers. Taxonomic diversity increased with time since glacier retreat
and with soil evolution; the pattern was consistent across different
groups and soil depths. For Eukaryota, and particularly Mycota,
alpha-diversity was generally the highest in soils close to the surface.
Time since glacier retreat was a more important driver of community
composition compared to soil depth; for nearly all the taxa, differences
in community composition between surface and deep soils decreased with
time since glacier retreat, suggesting that the development of soil
and/or of vegetation tends to homogenize the first 20 cm of soil through
time. Within both Bacteria and Mycota, several molecular operational
taxonomic units were significant indicators of specific depths and/or
soil development stages, confirming the strong functional variation of
microbial communities through time and depth. The complexity of
community patterns highlights the importance of integrating information
from multiple taxonomic groups to unravel community variation in
response to ongoing global changes.