Biology subjects

Chanton, J.

Publications and source records attributed to Chanton, J..

3 recordsLinked to original sources

bioRxiv2023

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

Peatlands store approximately one-third of the global terrestrial carbon and are historically considered carbon sinks due to primary production outpacing microbial decomposition of organic matter. Climate change has the potential to alter the rate at which peatlands store or release carbon, and results from the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment have shown net losses of organic matter and increased greenhouse gas production from a boreal peatland in response to whole-ecosystem warming. In this study, we utilized the SPRUCE sites to investigate how warming and elevated CO2 impact peat microbial communities and peat soil decomposition. We deployed peat soil decomposition ladders across warming and CO2 treatment enclosures for three years, after which we characterized bacterial, archaeal, and fungal communities through amplicon sequencing and measured peat mass and compositional changes across four depth increments. Microbial diversity and community composition were significantly impacted by soil depth, temperature, and CO2 treatment. Bacterial/archaeal -diversity increased significantly with increasing temperature, and fungal -diversity was significantly lower under elevated CO2 treatment. Trans-domain microbial networks showed higher complexity (nodes, edges, degree, betweenness centrality) of microbial communities in decomposition ladders from warmed enclosures, and the number of highly connected, hub taxa within the networks was positively correlated with temperature. Methanogenic hubs were identified in the networks constructed from the warmest enclosures, indicating increased importance of methanogenesis in response to warming. Microbial community responses were not however reflected in measures of peat soil decomposition, as warming and elevated CO2 had no significant short-term effects on soil mass loss or composition. Regardless of treatment, on average only 4.5% of the original soil mass was lost after three years and variation between replicates was high, potentially masking treatment effects. Many previous studies from the SPRUCE experiment have shown that warming is accelerating organic-matter decomposition and CO2 and CH4 production, and our results suggest that these changes may be driven by warming-induced shifts in microbial communities.

ecology↗

bioRxiv2021

Plant organic matter inputs exert a strong control on soil organic matter decomposition in a thawing permafrost peatland

Peatlands are a climate critical carbon (C) reservoir that will likely become a C source under continued warming. A strong relationship between plant tissue chemistry and the soil organic matter (SOM) that fuels C gas emissions is inferred, but rarely examined at the molecular level. Here we compared Fourier transform infrared (FT-IR) spectroscopy measurements of solid phase functionalities in plants and SOM to ultra-high-resolution mass spectrometric analyses of plant and SOM water extracts across a palsa-bog-fen thaw and moisture gradient in an Arctic peatland. From these analyses we calculated the C oxidation state (NOSC), a measure which can be used to assess organic matter quality. Palsa plant extracts had the highest NOSC, indicating high quality, while extracts of Sphagnum, which dominated the bog, had the lowest NOSC. The percentage of plant compounds that are less bioavailable and accumulate in the peat, increases from palsa (25%) to fen (41%) to bog (47 %), reflecting the pattern of percent Sphagnum cover. The pattern of NOSC in the plant extracts was consistent with the high number of consumed compounds in the palsa and low number of consumed compounds in the bog. However, in the FT-IR analysis of the solid phase bog peat, carbohydrate content was high implying higher quality SOM. We explain this discrepancy as the result of low solubilization of bog SOM facilitated by the low pH in the bog which makes the solid phase carbohydrates less available to microbial decomposition. Plant-associated lignins and tannins declined in the unsaturated palsa peat indicating decomposition, but accumulated in the bog and fen peat where decomposition was presumably inhibited by the anaerobic conditions. A molecular-level comparison of the aboveground C sources and peat SOM demonstrates that climate-associated vegetation shifts in peatlands are important controls on the mechanisms underlying changing C gas emissions.

ecology↗

bioRxiv2021

Quantifying the Inhibitory Impact of Soluble Phenolics on Carbon Mineralization from Sphagnum-rich Peatlands

The mechanisms controlling the extraordinarily slow carbon (C) mineralization rates characteristic of Sphagnum-rich peatlands ("bogs") remain somewhat elusive, despite decades of research on this topic. Soluble phenolic compounds have been invoked as potentially significant contributors to bog peat recalcitrance due to their affinity to slow microbial metabolism and cell growth. Despite this potentially significant role, the effects of soluble phenolic compounds on bog peat C mineralization remain unclear. We analyzed this effect by manipulating the concentration of free soluble phenolics in anaerobic bog peat incubations using water-soluble polyvinylpyrrolidone (PVP), a compound that binds with and inactivates phenolics, preventing phenolic-enzyme interactions. CO2 and CH4 production rates (end-products of C mineralization) correlated positively with PVP concentration following Michaelis-Menten (M.M.) saturation functions. Using M.M. parameters, we determined that soluble phenolics inhibit, at minimum, 57 {+/-} 16% of total C (CO2+CH4) mineralization in the anaerobic incubation conditions studied. These findings are consistent with other studies that have indicated that soluble phenolics play a significant role in regulating bog peat stability in the face of decomposition.

ecology↗