Permafrost thaw is transforming boreal forests into mosaics of wetlands and drier uplands. Topographic controls on hydrological and ecological conditions impact methane (CH4) fluxes, contributing to uncertainty in local and regional CH4 budgets and underlying drivers. The objective of this study was to explore CH4 fluxes and their drivers in a transitioning boreal forest-fen ecosystem (Goldstream Valley, Alaska, USA). This landscape is characterized by thawing discontinuous permafrost and heterogeneous mosaics of fens, collapse-scar channels, and small mounds of permafrost soils. From a survey in July 2021, observed chamber CH4 fluxes included fen areas with intermediate to very high emissions (29.8-635.3 mg CH4 m(-2) d(-1)), clustered locations with CH4 uptake (-2.11 to -0.7 mg CH4 m(-2) d(-1)), and three anomalous emission hotspots (342.4-772.4 mg CH4 m(-2) d(-1)) that were located near samples with lower emissions. Some surface and near-surface variables partially explained the spatial variation in CH4 flux. Log-transformed CH4 flux had a positive linear relationship with soil moisture at 20 cm depth (R-2 = 0.31, p-value < 1e-5) and negative linear relationships with microtopography (R-2 = 0.13, p-value < 0.006) and slope (R-2 = 0.28, p-value < 2e-5). Methane emissions generally occurred in flat, wet, graminoid-dominated fens, whereas CH4 uptake occurred on permafrost mounds dominated by feather mosses and woody vegetation. However, the CH4 hotspots occurred on drier, slightly sloped locations with low or undetectable near-surface methanogen abundance, suggesting that CH4 was produced in deeper soils. When the hotspot samples were omitted, log-transformed CH4 flux had a positive linear relationship with near-surface methanogen abundance (R-2 = 0.29, p-value = 0.0023), and stronger linear relationships with soil moisture, slope, and soil macronutrient concentrations. Our findings suggest that some CH4 emission hotspots could arise from CH4 in deep taliks. The inference that methanogenesis occurs in deep taliks was strengthened by the identification of intrapermafrost taliks across the study area using low-frequency geophysical induction. This study assesses surface spatial heterogeneity in the context of subsurface permafrost conditions and highlights the complexity of CH4 flux patterns in transitioning forest-wetland ecosystems. To better inform regional CH4 budgets, further research is needed to understand the spatial distribution of terrestrial CH4 hotspots and to resolve their surface, near-surface, and subsurface drivers.

Resource depletion and climate changes due to human activities and excessive burning of fossil fuels are the driving forces to explore alternatives clean energy resources. The objective of this study was to investigate the potential of potato peel waste (PPW) at various temperatures T15 (15 degrees C), T25 (25 degrees C), and T35 (35 degrees C) in anaerobic digestion (AD) for biogas generation. The highest biogas and CH4 production (117 mL VS-g and 74 mL VS-g) was observed by applying 35 degrees C (T35) as compared with T25 (65 mL VS-g and 22 mL VS-g) on day 6. Changes in microbial diversity associated with different temperatures were also explored. The Shannon index of bacterial community was not significantly affected, while there was a positive correlation of archaeal community with the applied temperatures. The bacterial phyla Firmicutes were strongly affected by T35 (39%), whereas Lactobacillus was the dominant genera at T15 (27%). Methanobacterium and Methanosarcina, as archaeal genera, dominated in T35 temperature reactors. In brief, at T35, Proteiniphilum and Methanosarcina were positively correlated with volatile fatty acids (VFAs) concentration. Spearman correlation revealed dynamic interspecies interactions among bacterial and archaeal genera; facilitating the AD system. This study revealed that temperature variations can enhance the microbial community of the AD system, leading to increased biogas production. It is recommended for optimizing the AD of food wastes.

Permafrost thaw could increase methane (CH4) emissions, which largely depends on CH4 production driven by methanogenic archaea. However, large-scale evidence regarding key methanogenic taxa and their relative importance to abiotic factors in mediating methanogenesis remains limited. Here, we explored the methanogenic community, potential CH4 production and its determinants in the active layer and permafrost deposits based on soil samples acquired from 12 swamp meadow sites along a , similar to 1000 km permafrost transect on the Tibetan Plateau. Our results revealed lower CH4 production potential, mcrA gene abundance, and richness in the permafrost layer than those in the active layer. CH4 production potential in both soil layers was regulated by microbial and abiotic factors. Of the microbial properties, marker OTUs, rather than the abundance and diversity of methanogens, stimulated CH4 production potential. Marker OTUs differed between the two soil layers with hydrogenotrophic Methanocellales and facultative acetoclastic Methanosarcina predominant in regulating CH4 production potential in the permafrost and active layer, respectively. Besides microbial drivers, CH4 production potential increased with the carbon/nitrogen (C/N) ratio in both soil layers and was also stimulated by soil moisture in the permafrost layer. These results provide empirical evidence for model improvements to better predict permafrost carbon feedback to climate warming.

Although the martian environment is currently cold and dry, geomorphological features on the surface of the planet indicate relatively recent (<4 My) freeze/thaw episodes. Additionally, the recent detections of near-subsurface ice as well as hydrated salts within recurring slope lineae suggest potentially habitable micro-environments within the martian subsurface. On Earth, microbial communities are often active at sub-freezing temperatures within permafrost, especially within the active layer, which experiences large ranges in temperature. With warming global temperatures, the effect of thawing permafrost communities on the release of greenhouse gases such as carbon dioxide and methane becomes increasingly important. Studies examining the community structure and activity of microbial permafrost communities on Earth can also be related to martian permafrost environments, should life have developed on the planet. Here, two non-psychrophilic methanogens, Methanobacterium formicicum and Methanothermobacter wolfeii, were tested for their ability to survive long-term (similar to 4 year) exposure to freeze/thaw cycles varying in both temperature and duration, with implications both for climate change on Earth and possible life on Mars.