DISCUSSION
Our work provides new insights on the colonization and primary
succession patterns in deglaciated terrains, by integrating soil depth
in the primary succession studies and by implementing a multi-taxa
approach across multiple forelands. Here, the multi-taxa approach
allowed characterizing patterns for a wide range of topsoil organisms
involved in colonization and successional processes. In order to cover
the largest proportion of biodiversity, we considered both generalist
(for Bacteria, Mycota and Eukaryota) and more specific (for Collembola,
Insecta and Oligochaeta) markers. Alpha- and beta-diversity variation
through time showed a strikingly consistent pattern across these taxa.
The considered depths did not strongly affect the alpha diversity of
some taxa at any stage of soil development, even though communities
inhabiting surface and deep soil layers were not exactly the same.
Importantly, beta-diversity between surface and deep soil decreased
through time across most of taxa, supporting the hypothesis of
homogenization between surface and deep soil along the succession (Rime
et al., 2015).