Multiple-trophic patterns of primary succession following retreat of a high-elevation glacier

How multiple, interacting components of complex soil communities assemble within forefields of receding glaciers is still largely unknown, especially at high-elevation sites (>5000 m a.s.l.) where plant succession is very slow. To examine succession of soil communities across different trophic levels, we investigated four major soil groups: bacteria, fungi, nematodes, and other non-fungal non-nematode microbial eukaryotes at the Puca Glacier in the Peruvian Andes spanning 9-, 24-, and 89-year-old deglaciated soils. This is the first study of microbial communities, other than bacteria, at a high-elevation chronosequence in the Andes Mountains. In addition, we characterized soil biogeochemical properties (e.g., C, N, moisture, and pH) and rates of microbial enzyme activities associated with C, N, and P acquisition. We found significantly correlated increases in estimated richness and high species turnover in all soil groups along the chronosequence. These shifts in soil communities were significantly correlated with microbial enzyme activities and measures of C, N, moisture, and pH. Stoichiometric comparisons of enzyme activities showed phosphorus (P) and carbon (C) limitation of microbial activity across the entire chronosequence with no hint of nitrogen (N) limitation. Taken together, the observed shifts in soil communities and biogeochemistry indicate coordinated increases in trophic complexity and ecosystem functioning during the initial 90 yr of microbial succession along the post-glacial chronosequence of the Puca Glacier.