Peatland microbial community responses to plant functional group and drought are depth‐dependent

Abstract

Peatlands store one‐third of Earth's soil carbon, the stability of which is uncertain due to climate change‐driven shifts in hydrology and vegetation, and consequent impacts on microbial communities that mediate decomposition. Peatland carbon cycling varies over steep physicochemical gradients characterizing vertical peat profiles. However, it is unclear how drought‐mediated changes in plant functional groups (PFGs) and water table (WT) levels affect microbial communities at different depths. We combined a multiyear mesocosm experiment with community sequencing across a 70‐cm depth gradient, to test the hypotheses that vascular PFGs (Ericaceae vs. sedges) and WT (high vs. low) structure peatland microbial communities in depth‐dependent ways. Several key results emerged. (i) Both fungal and prokaryote (bacteria and archaea) community structure shifted with WT and PFG manipulation, but fungi were much more sensitive to PFG whereas prokaryotes were much more sensitive to WT. (ii) PFG effects were largely driven by Ericaceae, although sedge effects were evident in specific cases (e.g., methanotrophs). (iii) Treatment effects varied with depth: the influence of PFG was strongest in shallow peat (0–10, 10–20 cm), whereas WT effects were strongest at the surface and middle depths (0–10, 30–40 cm), and all treatment effects waned in the deepest peat (60–70 cm). Our results underline the depth‐dependent and taxon‐specific ways that plant communities and hydrologic variability shape peatland microbial communities, pointing to the importance of understanding how these factors integrate across soil profiles when examining peatland responses to climate change.

Peatland Degradation Reduces Microbial Richness and Alters Microbial Functions in an Australian Peatland

“…In contrast to prokaryotes, soil fungal community structure was not affected by soil depth in the intact bog, consistent with Wang et al (2019) who studied minerotrophic fens in China using a similar sampling design to ours, but in contrast with Lamit et al (2017Lamit et al ( , 2021 who found dramatic shifts in fungal community structure with depth. Furthermore, it is important to note that marginal sampling effort in our study may have affected the detectability of an effect of soil depth on fungal communities, similarly to Wang et al (2019) and in contrast to Lamit et al (2017Lamit et al ( , 2021 where sampling effort was greater. This is farther re ected in the lack of overall compositional shifts in soil fungi in our study, although phyla and functional guilds changed with soil depth.…”

“…Whilst microbial biomass has been shown to be typically high across all peat depths, microbial composition varies with peat depth as it is shaped by many factors, including moisture and oxygen availability [23,69], changes in substrate and redox potential [11,70], and carbon and soil nutrient dynamics [66].…”

“…These changes in vertical abiotic conditions are likely to lead to changes in fungal and prokaryotic community composition, diversity and function as well. Our understanding of the fungal, especially mycorrhizal and free-living saprotrophic fungi, in peatland carbon cycling is very limited [21][22][23] in comparison with the prokaryotic guilds (e.g., methanogens and methanotrophs) that have received more research attention [24,25]. This knowledge gap highlights the need to further explore the importance of fungal communities in peatlands.…”

Does Shift in Vegetation Abundance After Nitrogen and Phosphorus Additions Play a Key Role in Regulating Fungal Community Structure in a Northern Peatland?

“…Furthermore, a loss of living Sphagnum will lead to the subsidence of bare peat and the subsequent saturated conditions are not favorable for the growth of ericaceous shrubs. The significant correlation between the abundance of ericaceous shrubs and the relative abundance of ErMF is in line with the finding that the removal of Ericaceae can cause a remarkable decrease in ErMF abundance ( Lamit et al, 2021 ).…”

“…Although PFT abundance changed substantially after N and/or P additions, the anticipated cascading effect on the fungal community was weak, which is inconsistent with our second hypothesis. This may be because our surface peat cannot capture the complex vertical stratification of the fungal community associated with vascular plants with different rooting depths in peatlands (e.g., Lin et al, 2014 ; Lamit et al, 2021 ). Unexpectedly, even 2 years of N and/or P additions also significantly changed PFT abundance, but the effects were complex.…”