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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Current developments in soil organic matter modeling and the expansion of model applications. A review

It is important to note that Soil organic matter (SOM) is a great natural resource. It is fundamental to soil and ecosystem functions across a wide range of scales, from site-specific soil fertility and water holding capacity to global biogeochemical cycling. It is also a highly complex material that is sensitive to direct and indirect human impacts. In our SOM research, simulation models play an important role by providing a mathematical framework to integrate, examine, and test the understanding of SOM dynamics. Simulation models of SOM are also increasingly used in more ‘applied’ settings to evaluate human impacts on ecosystem function, and to manage SOM for greenhouse gas mitigation, improved soil health, and sustainable use as a natural resource. Within this context, there is a need to maintain a robust connection between scientific developments in SOM modeling approaches and SOM model applications. This need forms the basis of this review. In this review we first provide an overview of SOM modeling, focusing on SOM theory, data-model integration, and model development as evidenced by a quantitative review of SOM literature. Second, we present the landscape of SOM model applications, focusing on examples in climate change policy. Finally, we conclude by discussing five areas of recent developments in SOM modeling including: (1) microbial roles in SOM stabilization; (2) modeling SOM saturation kinetics; (3) temperature controls on decomposition; (4)SOM dynamics in deep soil layers; and (5)SOM representation in earth system models. Our aim is to comprehensively connect SOM model development to its applications, revealing knowledge gaps in need of focused interdisciplinary attention and exposing pitfalls that, if avoided, can lead to best use of SOM models to support policy initiatives and sustainable land management solutions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Microbial functional diversity covaries with permafrost thaw-induced environmental heterogeneity in tundra soil

Permafrost soil in high latitude tundra is one of the largest terrestrial carbon (C) stocks and is highly sensitive to climate warming. Understanding microbial responses to warming-induced environmental changes is critical to evaluating their influences on soil biogeochemical cycles. In this study, a functional gene array (i.e., geochip 4.2) was used to analyze the functional capacities of soil microbial communities collected from a naturally degrading permafrost region in Central Alaska. Varied thaw history was reported to be the main driver of soil and plant differences across a gradient of minimally, moderately, and extensively thawed sites. Compared with the minimally thawed site, the number of detected functional gene probes across the 15-65 cm depth profile at the moderately and extensively thawed sites decreased by 25% and 5%, while the community functional gene β-diversity increased by 34% and 45%, respectively, revealing decreased functional gene richness but increased community heterogeneity along the thaw progression. Particularly, the moderately thawed site contained microbial communities with the highest abundances of many genes involved in prokaryotic C degradation, ammonification, and nitrification processes, but lower abundances of fungal C decomposition and anaerobic-related genes. Significant correlations were observed between functional gene abundance and vascular plant primary productivity, suggesting that plant growth and species composition could be co-evolving traits together with microbial community composition. Finally, altogether, this study reveals the complex responses of microbial functional potentials to thaw-related soil and plant changes and provides information on potential microbially mediated biogeochemical cycles in tundra ecosystems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Altering plant carbon allocation to stems has distinct effects on rhizosphere soil microbiome assembly, interactions, and potential functions in sorghum

Abstract Altering plant carbon allocation from leaves to stems is key to improve biomass for forage, fuel, and renewable chemicals. The sorghum dry stalk ( D ) locus controls a quantitative trait for sugar accumulation, with enhanced carbon allocation in the stems of juicy green ( dd ) sorghum but reduced carbon allocation in that of dry white ( DD ) sorghum. However, it remains unclear whether altering sorghum sugar accumulation in stem affects below‐ground microbiome. Here we investigated sorghum rhizosphere soil microbiome in near isogenic lines with different magnitude of carbon allocations and accumulation in the stems. Results showed that enhanced carbon accumulation in stems of juicy green sorghum results in stronger selection in rhizosphere microbiome assembly. The rhizosphere soil microbial communities selected in juicy green sorghum tended to be fast‐growing microbial taxa which possessed potential functions that would promote higher potential capacity to use chemically labile carbon sources and potentially result in higher potential decomposition rates. We found the rhizosphere microbes selected by juicy green sorghum form weaker interactions than dry white sorghum. This is the first comprehensive study revealing how the different magnitude of carbon allocations to stems regulates microbial community assembly, microbial interaction, and microbial functions. This study indicates that future plant modification for bioenergy crops should also consider the impacts on belowground microbial community without compromising the sustainability.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Mineral protection of soil carbon counteracted by root exudates [Root exudates counteract mineral control on soil carbon turnover]

Multiple lines of existing evidence suggest that climate change enhances root exudation of organic compounds into soils. Recent experimental studies show that increased exudate inputs may cause a net loss of soil carbon. This stimulation of microbial carbon mineralization (‘priming’) is commonly rationalized by the assumption that exudates provide a readily bioavailable supply of energy for the decomposition of native soil carbon (co-metabolism). Here we show that an alternate mechanism can cause carbon loss of equal or greater magnitude. We find that a common root exudate, oxalic acid, promotes carbon loss by liberating organic compounds from protective associations with minerals. By enhancing microbial access to previously mineral-protected compounds, this indirect mechanism accelerated carbon loss more than simply increasing the supply of energetically more favourable substrates. Lastly, our results provide insights into the coupled biotic–abiotic mechanisms underlying the ‘priming’ phenomenon and challenge the assumption that mineral-associated carbon is protected from microbial cycling over millennial timescales.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Soil pore architecture and rhizosphere legacy define N 2 O production in root detritusphere

Root detritusphere is one of the most important sources of N 2 O, however, understanding of how N 2 O emission from the detritusphere is influenced by soil properties remains elusive. Here, we evaluated the effects of pore architecture and soil moisture on N 2 O emission during the decomposition of in-situ grown roots of switchgrass, an important bioenergy crop. We combined dual isotope labeling ( 15 C and 15 N) with zymography to gain insights into the location of the microbial N 2 O production in soils with contrasting pore architectures. In the studied soil, the effect of soil pore architecture on N 2 O emissions was 6 times greater than that of soil moisture. Soil dominated by > 30 μm Ø pores (i.e., large-pore soil) had higher chitinase activity than the soil dominated by < 10 μm Ø pores (i.e., small-pore soil), especially near the decomposing roots. The chitinase activity on the decomposing roots was positively correlated with emission of root-derived N 2 O, indicating that N released from root decomposition was an important source of N 2 O. Greater N 2 O and N2 emission was induced by switchgrass roots in soils dominated by the large- compared to the small-pore soils. Here, the microenvironment developed near decomposing roots of the large-pore soil also resulted in positive N 2 O priming. Our study challenged the traditional view on soil moisture as the main factor of N 2 O production. Production and emission of N 2 O was most intensive in microbial activity hotspots (i.e., rhizosphere legacy) in the large pores, where decomposed roots release mineral N as the main N 2 O source.

13C Pulse labeling↗
DOE OSTI2023

Manganese effects on plant residue decomposition and carbon distribution in soil fractions depend on soil nitrogen availability

Recent studies have highlighted the critical role of manganese (Mn) in plant litter decomposition and soil organic carbon (C) cycling in forest ecosystems. Long term nitrogen (N) deposition and N fertilization can increase soil acidity and mobilize bioavailable Mn (Mn 2+ ) in soil. However, no studies have examined the interactive effect of N and Mn fertilization on litter decomposition and carbon distribution in agricultural soils, despite agroecosystems being subject to both N and Mn management. We hypothesized that increased soil N and Mn availability would accelerate plant residue decomposition and transfer of its C to mineral-associated organic matter (MAOM), and that the combined effect of Mn and N enrichment would be greater than the individual effect. Here, we conducted a laboratory incubation experiment by adding 13 C-labeled residue of perennial grass Glyceria striata (Lam.) to agricultural soils that had received 225 kg N ha –1 yr –1 for 27 years (N 1 ) and comparable soils that received no N (N 0 ). Before the experiment, these soils also received three levels of dissolved Mn 2+ , designated M 0 (no additional Mn), M 1 (50 mg kg –1 ), or M 2 (250 mg kg –1 ). We measured total CO 2 production as well as distribution of 13 C from the residue into CO 2 , particulate organic matter (POM), MAOM, and dissolved organic carbon (DOC) over a 1-year period. Manganese amendments significantly increased CO 2 production from residue decomposition in the N 1 soil, but no such effect was observed in the N 0 soil. Manganese also accelerated the loss of residue-derived C from POM and DOC, but increased its recovery in MAOM. However, the positive effect of added Mn in decomposition and recovery in MAOM in the presence of N fertilization occurred only during the initial 30-day decomposition period, where M 2 showed a 12% increase in cumulative CO 2 production from residue, 8% increase in POM loss, and 43% increase in recovery of residue C in MAOM compared to M 0 . For M 1 , only CO 2 emission from residue was significantly higher than Mo during this period. At 365 days M 2 showed 8% increase in CO 2 production, 1% increase in POM loss, and 16% increase in recovery of residue C in MAOM compared to M 0 , but none of these were statistically significant (p < 0.05). This study adds to the growing evidence that increasing Mn availability enhances plant litter decomposition. However, the occurrence and magnitude of Mn-induced stimulation of decomposition is context specific. Further investigation with greater temporal resolution, involving a multitude of litter and soil types and including microbial compositional and functional characterization, is recommended to fully elucidate the interactive role of Mn and N on C cycling.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Microbial carbon use efficiency promotes global soil carbon storage

Soils store more carbon than other terrestrial ecosystems. How soil organic carbon (SOC) forms and persists remains uncertain, which makes it challenging to understand how it will respond to climatic change. It has been suggested that soil microorganisms play an important role in SOC formation, preservation and loss. Although microorganisms affect the accumulation and loss of soil organic matter through many pathways, microbial carbon use efficiency (CUE) is an integrative metric that can capture the balance of these processes. Although CUE has the potential to act as a predictor of variation in SOC storage, the role of CUE in SOC persistence remains unresolved. Here we examine the relationship between CUE and the preservation of SOC, and interactions with climate, vegetation and edaphic properties, using a combination of global-scale datasets, a microbial-process explicit model, data assimilation, deep learning and meta-analysis. We find that CUE is at least four times as important as other evaluated factors, such as carbon input, decomposition or vertical transport, in determining SOC storage and its spatial variation across the globe. In addition, CUE shows a positive correlation with SOC content. Our findings point to microbial CUE as a major determinant of global SOC storage. Understanding the microbial processes underlying CUE and their environmental dependence may help the prediction of SOC feedback to a changing climate.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2016

Resource stoichiometry and the biogeochemical consequences of nitrogen deposition in a mixed deciduous forest

Abstract Ecosystems often show differential sensitivity to chronic nitrogen (N) deposition; hence, a critical challenge is to improve our understanding of how and why site‐specific factors mediate biogeochemical responses to N enrichment. We examined the extent to which N impacts on soil carbon (C) and N dynamics depend on microbial resource stoichiometry. We added N to forest plots dominated by ectomycorrhizal ( ECM ) trees, which have litter and soil pools rich in organic N and relatively wide C:N ratios, and adjacent forest plots dominated by arbuscular mycorrhizal ( AM ) trees, which have litter and soil pools rich in inorganic N and relatively narrow C:N ratios. While microbes in both plot types exhibited fairly strict biomass homeostasis, microbes in AM ‐ and ECM ‐dominated plots differed in their physiological responses to N addition. Microbes in ECM plots responded to N enrichment by decreasing their investment in N‐acquisition enzymes (relative to C‐acquisition enzymes) and increasing N mineralization rates (relative to C mineralization rates), suggesting that N addition alleviated microbial N demand. In contrast, heterotrophic microbial activities in AM plots were unaffected by N addition, most likely as a result of N‐induced increases in net nitrification (60% increase relative to control plots) and nitrate mobilization (e.g., sixfold increases in mobilization relative to control plots). Combined, our findings suggest the stoichiometric differences between AM and ECM soils are the primary drivers of the observed responses. Plant and microbial communities characterized by wide C:N are more susceptible to N‐induced changes in decomposition and soil C dynamics, whereas communities characterized by narrow C:N are more susceptible to N‐induced nitrate leaching losses. Hence, the biogeochemical consequences of N deposition in temperate forests may be driven by the stoichiometry of the dominant trees and their associated microbes.

Midgley, Meghan G.↗
DOE OSTI2019

Continental scale structuring of forest and soil diversity via functional traits

Trait-based ecology claims to offer a mechanistic approach for explaining the drivers that structure biological diversity and predicting the responses of species, trophic interactions and ecosystems to environmental change. However, support for this claim is lacking across broad taxonomic groups. A framework for defining ecosystem processes in terms of the functional traits of their constituent taxa across large spatial scales is needed. Here, we provide a comprehensive assessment of the linkages between climate, plant traits and soil microbial traits at many sites spanning a broad latitudinal temperature gradient from tropical to subalpine forests. Our results show that temperature drives coordinated shifts in most plant and soil bacterial traits but these relationships are not observed for most fungal traits. Shifts in plant traits are mechanistically associated with soil bacterial functional traits related to carbon (C), nitrogen (N) and phosphorus (P) cycling, indicating that microbial processes are tightly linked to variation in plant traits that influence rates of ecosystem decomposition and nutrient cycling. In conclusion, our results are consistent with hypotheses that diversity gradients reflect shifts in phenotypic optima signifying local temperature adaptation mediated by soil nutrient availability and metabolism. They underscore the importance of temperature in structuring the functional diversity of plants and soil microbes in forest ecosystems and how this is coupled to biogeochemical processes via functional traits.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Tracing priming effects in palsa peat carbon dynamics using a stable isotope-assisted metabolomics approach

Introduction: Peatlands store up to a third of global soil carbon, and in high latitudes their litter inputs are increasing and changing in composition under climate change. Although litter significantly influences peatland carbon and nutrient dynamics by changing the overall lability of peatland organic matter, the physicochemical mechanisms of this impact—and thus its full scope—remain poorly understood. Methods: We applied multimodal metabolomics (UPLC-HRMS, 1 H NMR) paired with 13 C Stable Isotope-Assisted Metabolomics (SIAM) to track litter carbon and its potential priming effects on both existing soil organic matter and carbon gas emissions. Through this approach, we achieved molecule-specific tracking of carbon transformations at unprecedented detail. Results: Our analysis revealed several key findings about carbon dynamics in palsa peat. Microbes responded rapidly to litter addition, producing a short-term increase in CO 2 emissions, fueled nearly exclusively by transformations of litter carbon. Litter inputs significantly contributed to the organic nitrogen pool through amino acids and peptide derivatives, which served as readily accessible nutrient sources for microbial communities. We traced the fate of plant-derived polyphenols including flavonoids like rutin, finding evidence of their degradation through heterocyclic C-ring fission, while accumulation of some polyphenols suggested their role in limiting overall decomposition. The SIAM approach detected subtle molecular changes indicating minimal and transient priming activity that was undetectable through conventional gas measurements alone. This transient response was characterized by brief microbial stimulation followed by rapid return to baseline metabolism. Pre-existing peat organic matter remained relatively stable; significant priming of its consumption was not observed, nor was its structural alteration. Discussion: This suggests that while litter inputs temporarily increase CO 2 emissions, they don’t sustain long-term acceleration of stored carbon decomposition or substantially decrease peat’s carbon store capacity. Our findings demonstrate how technological advancements in analytical tools can provide a more detailed view of carbon cycling processes in complex soil systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Enhanced aquatic respiration associated with mixing of clearwater tributary and turbid Amazon River waters

When water bodies with unique biogeochemical constituents mix together there is potential for diverse responses by aquatic microbial communities and associated ecosystem functions. Here we evaluate bulk respiration rates under varying mixtures of turbid Amazon River water and two lowland tributaries—the Tapajós and Xingu rivers—based on O2 drawdown in dark rotating incubation chambers. Preliminary experiments containing 50% Tapajós River and 50% Amazon River water were performed during falling water. More detailed experiments containing 5%, 17%, 33%, and 50% tributary water were performed for both the Tapajós and Xingu rivers at 3 different rotation velocities (0, 0.22, and 0.66 m s-1) during the falling water period. Respiration rates were higher in the mixtures compared to both river endmembers in most experiments. For both the Xingu and Tapajós rivers a 17% mixture yielded maximal respiration rates that were 1.6 to 2.8 times faster than each tributary, respectively. The 50% mixtures, on the other hand, only yielded 1.4 to 1.9 times amplified respiration rates for the Tapajós and Xingu rivers, respectively, and in one case was respiration was 2.8 times lower in the 50% mixture compared to the tributary. We hypothesize that these enhanced respiration rates are driven, in part, by microbial priming effects that have been previously identified on a molecular level for these rivers. The results of this study suggest that there may be a “sweet spot” for priming effects to occur in terms of the relative abundance of “priming” and “primed” substrates.

58 GEOSCIENCES↗
DOE OSTI2025

Vulnerability of mineral-organic associations in the rhizosphere

The majority of soil carbon (C) is stored in organic matter associated with reactive minerals. These mineral-organic associations (MOAs) inhibit microbial and enzymatic access to organic matter, suggesting that organic C within MOAs is resistant to decomposition. However, plant roots and rhizosphere microbes are known to transform minerals through dissolution and exchange reactions, implying that MOAs in the rhizosphere can be dynamic. Here we identify key drivers, mechanisms, and controls of MOA disruption in the rhizosphere and present a new conceptual framework for the vulnerability of soil C within MOAs. We introduce a vulnerability spectrum that highlights how MOAs characteristic of certain ecosystems are particularly susceptible to specific root-driven disruption mechanisms. This vulnerability spectrum provides a framework for critically assessing the importance of MOA disruption mechanisms at the ecosystem scale. Comprehensive representation of not only root-driven MOA formation, but also disruption, will improve model projections of soil C-climate feedbacks and guide the development of more effective soil C management strategies.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Radiocarbon analysis of soil microbial biomass via direct chloroform extraction

Microbial processing of soil organic matter is a significant driver of C cycling, yet we lack an understanding of what shapes the turnover of this large terrestrial pool. In part, this is due to limited options for accurately identifying the source of C assimilated by microbial communities. Laboratory incubations are the most common method for this; however, they can introduce artifacts due to sample disruption and processing and can take months to produce sufficient CO 2 for analysis. We present a biomass extraction method which allows for the direct 14 C analysis of microbial biomolecules and compare the results to laboratory incubations. In the upper 50 cm soil depths, the Δ 14 C from incubations was indistinguishable from that of extracted microbial biomass. Below 50 cm, the Δ 14 C of the biomass was more depleted than that of the incubations, either due to the stimulation of labile C decomposition in the incubations, the inclusion of biomolecules from non-living cells in the biomass extractions, or differences in C used for assimilation versus respiration. Our results suggest that measurement of Δ 14 C of microbial biomass extracts can be a useful alternative to soil incubations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Thermodynamically controlled preservation of organic carbon in floodplains

Organic matter decomposition in soils and terrestrial sediments has a prominent role in the global carbon cycle. Carbon stocks in anoxic environments, such as wetlands and the subsurface of floodplains, are large and presumed to decompose slowly. The degree of microbial respiration in anoxic environments is typically thought to depend on the energetics of available terminal electron acceptors such as nitrate or sulfate; microbes couple the reduction of these compounds to the oxidation of organic carbon. However, it is also possible that the energetics of the organic carbon itself can determine whether it is decomposed. Here we examined water-soluble organic carbon by Fourier-transform ion-cyclotron-resonance mass spectrometry to compare the chemical composition and average nominal oxidation state of carbon—a metric reflecting whether microbial oxidation of organic matter is thermodynamically favourable—in anoxic (sulfidic) and oxic (non-sulfidic) floodplain sediments. We observed distinct minima in the average nominal oxidation state of water-soluble carbon in sediments exhibiting anoxic, sulfate-reducing conditions, suggesting preservation of carbon compounds with nominal oxidation states below the threshold that makes microbial sulfate reduction thermodynamically favourable.We conclude that thermodynamic limitations constitute an important complement to other mechanisms of carbon preservation, such as enzymatic restrictions and mineral association, within anaerobic environments.

Boye, Kristin E.↗
DOE OSTI2016

Stability of peatland carbon to rising temperatures

Peatlands contain one-third of soil carbon (C), mostly buried in deep, saturated anoxic zones (catotelm). The response of catotelm C to climate forcing is uncertain, because prior experiments have focused on surface warming. Here, we show that deep peat heating of a 2 m-thick peat column results in an exponential increase in CH 4 emissions. But, this response is due solely to surface processes and not degradation of catotelm peat. Incubations show that only the top 20–30 cm of peat from experimental plots have higher CH 4 production rates at elevated temperatures. Radiocarbon analyses demonstrate that CH 4 and CO 2 are produced primarily from decomposition of surface-derived modern photosynthate, not catotelm C. Furthermore, there are no differences in microbial abundances, dissolved organic matter concentrations or degradative enzyme activities among treatments. Our results suggest that although surface peat will respond to increasing temperature, the large reservoir of catotelm C is stable under current anoxic conditions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Ecological and genomic responses of soil microbiomes to high-severity wildfire: linking community assembly to functional potential

Increasing wildfire severity, which is common throughout the western United States, can have deleterious effects on plant regeneration and large impacts on carbon (C) and nitrogen (N) cycling rates. Soil microbes are pivotal in facilitating these elemental cycles, so understanding the impact of increasing fire severity on soil microbial communities is critical. Here, we assess the long-term impact of high-severity fires on the soil microbiome. We find that high-severity wildfires result in a multi-decadal (>25 y) recovery of the soil microbiome mediated by concomitant differences in aboveground vegetation, soil chemistry, and microbial assembly processes. Our results depict a distinct taxonomic and functional successional pattern of increasing selection in post-fire soil microbial communities. Changes in microbiome composition corresponded with changes in microbial functional potential, specifically altered C metabolism and enhanced N cycling potential, which related to rates of potential decomposition and inorganic N availability, respectively. Based on metagenome-assembled genomes, we show that bacterial genomes enriched in our earliest site (4 y since fire) harbor distinct traits such as a robust stress response and a high potential to degrade pyrogenic, polyaromatic C that allow them to thrive in post-fire environments. Taken together, these results provide a biological basis for previously reported process rate measurements and explain the temporal dynamics of post-fire biogeochemistry, which ultimately constrains ecosystem recovery.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Functional insights of novel Bathyarchaeia reveal metabolic versatility in their role in peatlands of the Peruvian Amazon

ABSTRACT The decomposition of soil organic carbon within tropical peatlands is influenced by the functional composition of the microbial community. In this study, building upon our previous work, we recovered a total of 28 metagenome-assembled genomes (MAGs) classified as Bathyarchaeia from the tropical peatlands of the Pastaza-Marañón Foreland Basin (PMFB) in the Amazon. Using phylogenomic analyses, we identified nine genus-level clades to have representatives from the PMFB, with four forming a putative novel family (“CandidatusPaludivitaceae”) endemic to peatlands. We focus on theCa. Paludivitaceae MAGs due to the novelty of this group and the limited understanding of their role within tropical peatlands. Functional analysis of these MAGs reveals that this putative family comprises facultative anaerobes, possessing the genetic potential for oxygen, sulfide, or nitrogen oxidation. This metabolic versatility can be coupled to the fermentation of acetoin, propanol, or proline. The other clades outsideCa. Paludivitaceae are putatively capable of acetogenesis andde novoamino acid biosynthesis and encode a high amount of Fe 3+ transporters. Crucially, theCa. Paludivitaceae are predicted to be carboxydotrophic, capable of utilizing CO for energy generation or biomass production. Through this metabolism, they could detoxify the environment from CO, a byproduct of methanogenesis, or produce methanogenic substrates like CO 2 and H 2 . Overall, our results show the complex metabolism and various lineages of Bathyarchaeia within tropical peatlands pointing to the need to further evaluate their role in these ecosystems. IMPORTANCE With the expansion of theCandidatusPaludivitaceae family by the assembly of 28 new metagenome assembled genomes, this study provides novel insights into their metabolic diversity and ecological significance in peatland ecosystems. From a comprehensive phylogenic and functional analysis, we have elucidated their putative unique facultative anaerobic capabilities and CO detoxification potential. This research highlights their crucial role in carbon cycling and greenhouse gas regulation. These findings are essential for resolving the microbial processes affecting peat soil stability, offering new perspectives on the ecological roles of previously underexplored and underrepresented archaeal populations.

Microbiology↗
DOE OSTI2015

A microbial functional group-based module for simulating methane production and consumption: Application to an incubated permafrost soil

In this study, accurately estimating methane (CH 4 ) flux is critically important for investigating and predicting the biogeochemistry-climate feedback. Better simulating CH 4 flux requires explicit representations of microbial processes on CH 4 dynamics because all processes for CH 4 production and consumption are actually carried out by microbes. A microbial functional group based module was developed and tested against an incubation experiment. The module considers four key mechanisms for CH 4 production and consumption: methanogenesis from acetate or single-carbon compounds and CH 4 oxidation using molecular oxygen or other inorganic electron acceptors. These four processes were carried out by four microbial functional groups: acetoclastic methanogens, hydrogenotrophic methanogens, aerobic methanotrophs, and anaerobic methanotrophs. This module was then linked with the decomposition subroutine of the Community Land Model , and was further used to simulate dynamics of carbon dioxide (CO 2 ) and CH 4 concentrations from an incubation experiment with permafrost soils. The results show that the model could capture the dynamics of CO 2 and CH 4 concentrations in microcosms with top soils, mineral layer soils and permafrost soils under natural and saturated moisture conditions and a temperature gradient of -2°C, 3°C, and 5°C. Sensitivity analysis confirmed the importance of acetic acid's direct contribution as substrate and indirect effects through pH feedback on CO 2 and CH 4 production and consumption. This study suggests that representing the microbial mechanisms is critical for modeling CH 4 production and consumption; it is urgent to incorporate microbial mechanisms into Earth system models for better predicting the behavior of the climate system.

54 ENVIRONMENTAL SCIENCES↗