Elevated temperature alters microbial communities, but not decomposition rates, during 3 years of in situ peat decomposition

Abstract

Microbial community changes in response to climate change drivers have the potential to alter the trajectory of important ecosystem functions. In this paper, we show that while microbial communities in peatland systems responded to manipulations of temperature and CO₂ concentrations, these changes were not associated with similar responses in peat decomposition rates over 3 years. It is unclear however from our current studies whether this functional resiliency over 3 years will continue over the longer time scales relevant to peatland ecosystem functions.

Keywords: climate change; microbiome; organic matter decomposition; peatlands.

Fig 1

Principal coordinates analysis of Bray-Curtis dissimilarities of bacterial/archaeal (A) and fungal (B) communities in decomposition ladders. Points are colored based on sample depth, filled based on enclosure CO₂ treatments, and shaped based on enclosure temperature treatments.

Fig 2

Bacterial/archaeal (A) and fungal (B) α-diversity at q = 0 (species richness) across depths (vertical facets/colors), CO₂ treatments (horizontal facets), and temperature treatments (x-axis). Note that the PCR and sequencing runs for three fungal samples failed to produce a minimum number of quality controlled sequences and were thus omitted from analyses and this figure (panel B, second and third rows).

Fig 3

Summary of network topologies for temperature treatment microbial networks. The number of edges (A) represents the sum total connections between taxa (nodes; B) within the network. Mean degree (C) represents the average number of connections per taxon. Hubs (D) are defined as nodes within the network that are in the 90th percentile for degree and betweenness centrality and represent highly connected and centralized taxa.

Fig 4

Class-level distribution of network hubs across temperature treatments (color). Hubs were aggregated at class-level taxonomic annotations (y-axis) and faceted by kingdom-level taxonomy.

Fig 5

Comparisons of peat soil oven dry mass (A), carbon:nitrogen (B), percent aromatics (C), and percent carbohydrates (D) in peat decomposition ladders at the start of the experiment (T₀ ) and after 3 years of incubation in the SPRUCE enclosures (T_f). Box and whisker plots display the median (middle of box), quartiles (top and bottom of box), minimum and maximum values excluding outliers (end of whisker), and outliers (points).

Fig 6

Peat mass loss (% of starting mass lost) (A), percent C:N change (T_f – T₀) (B), percent aromatics change (T_f – T₀) (C), and percent carbohydrates change (T_f – T₀) (D) across depths (facets) and temperature treatments (x-axis).