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"McLaughlin, Jim"
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Microbial activity across a boreal peatland nutrient gradient: the role of fungi and bacteria
Microbes involved in decomposition within peatlands and the conditions that influence their activities have implications for C and greenhouse gas exchange. The objectives of this research were to characterize the role of fungal and bacterial activities in peatlands using selective antibiotic inhibition techniques across a nutrient gradient (rich to poor fens) and to search for environmental controls on the activity of each group. Bacterial activities predominated across a range of rich to poor boreal peatlands in central Ontario, Canada, although fungal activity became increasingly important in the poor sites. Linkages between soil pH and nutrient status and fungal and bacterial activities were found. However, they did not confirm our initial hypotheses that bacterial activity would be low in poor sites due to proton stress and low nutrient (particularly N) availability, whereas, fungal activity would be low in rich sites due to increased competitive ability of bacteria under near neutral pH conditions and high nutrient availability. Further work across these sites aimed at characterizing the phylogeny of the rhizosphere fungi is needed to determine if increased presence of mycorrhizae in poor sites could have explained our observed patterns. However, regardless of fungal: bacterial activity ratio differences across sites and its associated controls, microbial CO2 production rates across fen types did not vary significantly, suggesting that the proportion of bacteria and fungi may not matter to broader carbon cycling and greenhouse gas emissions in peat soils.
Journal Article
Batman, the brave and the bold : the Bronze Age
\"The late '60s marked the height of Batmania, when fans of the Batman television series and the comic books couldn't get enough of the Caped Crusader. His appearances on covers meant higher sales, so it was decreed Batman would take up permanent residence in THE BRAVE AND THE BOLD. His courage was never questioned, and he fearlessly teamed up with the most daring partners from across the DC Universe at a time when such crossovers were rare. These groundbreaking stories featured some of Batman's greatest team-ups with such legendary characters as Wonder Woman, the Flash, Deadman, Green Arrow, Green Lantern, the Teen Titans and others, all by some of the foremost comics talent of the Bronze Age--Neal Adams, Jim Aparo, Bob Haney, Dick Giordano and Dennis O'Neil, to name a few.\"-- Provided by publisher.
Book
The essential carbon service provided by northern peatlands
Northern peatlands have cooled the global climate by accumulating large quantities of soil carbon (C) over thousands of years. Maintaining the C sink function of these peatlands and their immense long-term soil C stores is critical for achieving net-zero global carbon dioxide (CO₂) emissions by 2050 to mitigate climate warming. One-quarter of the world’s northern peatlands are in Canada, with these mostly intact ecosystems providing a global C service that is increasingly recognized as a critical part of nature-based solutions to combat climate change. However, land-use change and other disturbances threaten these globally important stores of “irrecoverable C” (that is, soil C lost to disturbance that will take centuries to recover). Inadequate policy safeguards to avoid conversion and degradation, and the limited quantification and reporting of peatland greenhouse-gas emissions and removals, increase the vulnerability of these peatlands. Targeted policies from local to global scales will be needed for improved decision making and incentivizing long-term C management of northern peatlands.
Journal Article
Climate change effects on peatland decomposition and porewater dissolved organic carbon biogeochemistry
Carbon accumulation and storage is a defining characteristic of peatland ecosystems. Decomposition of peat releases dissolved organic carbon (DOC) to receiving waters and can be an important fraction of the peatland carbon budget, along with being an important modifier of downstream water quality. Changes in temperature and hydrological processes under future climate scenarios are expected to impact decomposition processes in peatlands with unclear ramifications for both the quantity and the quality of the DOC released. We experimentally examined the individual and interactive effects of increased temperature, elevated atmospheric carbon dioxide concentration, and lower water table position on peatland decomposition and the quantity and quality of porewater DOC in intact, replicated peat monoliths in a full factorial design. Decomposition rates and porewater DOC concentrations significantly increased under elevated temperature conditions; however, the quality of this carbon was variable, showing signs of both increased lability and recalcitrance. Lowered water table treatments also increased decomposition rates, although the high water conditions prompted greater porewater DOC concentrations and lability. It is expected that elevated decomposition rates under future climate scenarios will alter porewater DOC quantity in peatlands; however, we suggest that contributions from the aboveground system are needed to fully understand changes in DOC quality and subsequent ecosystem dynamics.
Journal Article
Effects of Climate Change on Peatlands in the Far North of Ontario, Canada: A Synthesis
The Hudson Bay Lowlands (HBL) is the largest peatland complex in North America. More than 75% of the HBL occurs in Ontario, where the provincial government mandates that ecosystem carbon storage and sequestration be considered in land-use planning. Accomplishing this task requires identifying carbon indicators and assessing their responses to changing ecosystem processes, such as succession, permafrost thaw, and evapotranspiration (ET). Therefore, we synthesized information on peat carbon indicators and ecosystem process from the literature. Findings indicate that the long-term carbon accumulation, carbon dioxide (CO2) sequestration, peat depth, and peatland age were similar (p > 0.10) between dry and wet peatland features. Furthermore, CO2 sequestration displayed the highest variability and ponds were net CO2 emitters. Recent carbon accumulation, CH4 emission, and ET were highest (p < 0.01) in wet features, with CH4 emission displaying wide variation. Increased active layer thickness (105 ± 92 cm per 100 years) in permafrost was the most variable ecosystem process analyzed in this study, while variation in permafrost loss (53 ± 23% per 100 years) was similar to that of carbon accumulation and ET rates. Processes creating wet and pond conditions may increase landscape-scale CO2 and CH4 emissions to the atmosphere, weakening peatland carbon sinks. Dry conditions may reduce CH4 emissions but potentially increase peatland susceptibility to fire. Knowledge of these changes should be useful for climate change vulnerability and adaptation assessments for large landscapes. However, better understanding of variability in CO2 sequestration, CH4 emission, and permafrost dynamics is required to design such assessments for small landscapes.
Journal Article
Enhanced carbon release under future climate conditions in a peatland mesocosm experiment: the role of phenolic compounds
BACKGROUND AND AIMS: Future climate conditions (warmer, wetter) are expected to change aboveground plant communities with linked belowground alterations (e.g. porewater chemistry) that can influence carbon dynamics. The aims of this study were 1) to determine if porewater phenolic compound concentrations reflect the changing aboveground plant community and 2) to elucidate if changes in phenolic compounds alter belowground carbon release. METHODS: We monitored the changes in vegetation biomass, porewater phenolic compound concentrations, respired CO₂ and phenol oxidase enzyme activity in 84 intact peatland mesocosms exposed to elevated atmospheric CO₂, elevated temperature, and decreased water table conditions in a full factorial design. RESULTS: Phenolic compound concentrations were indicative of the vascular plant expansion that occurred under warmer and anaerobic conditions, suggesting that phenolic compounds could be a simple indicator of northern plant community dynamics. Ecosystem CO₂ respiration increased with rising phenolic compound concentrations, suggesting that phenolic compounds can decrease microbial carbon use efficiency in northern peatlands. CONCLUSIONS: Using an aboveground-belowground framework we present a previously unrecognized mechanism influencing northern carbon dynamics; wherein, climate change conditions can restructure the plant community composition in turn increasing porewater phenolic concentrations, which results in decreased microbial carbon use efficiency and enhanced carbon release.
Journal Article
Forest Soil Calcium Dynamics and Water Quality: Implications for Forest Management Planning
Forest management planning is increasingly focused at the landscape scale. The resulting increase in planning unit size has fueled debate about forest sustainability, particularly at local scales. In boreal and temperate regions, Ca depletion in forest and aquatic ecosystems is a recently debated issue. Planning decisions that sustain forest soil and surface water Ca require identification of sites sensitive to Ca loss and application of silvicultural prescriptions that maintain background Ca pools and fluxes. Therefore, I synthesized data on forest Ca cycling and export and long‐term (>10 yr) soil exchangeable Ca pools and changes in surface water quality. Findings indicated that hardwood forest soils contained over three‐times more (P < 0.05), their catchments exported three‐times more (P < 0.05), and through leaf‐litter fall they recycled twice (p < 0.01) as much Ca as conifer–mixedwood forests. Nonetheless, over similar timeframes, forest floor in mature hardwood stands lost more (P < 0.05) Ca than did conifer–mixedwood soils, which was consistent with net stream and lake Ca losses (P < 0.01). However, surface water acid neutralizing capacity increased (P < 0.01), possibly due to greater sulfate declines relative to Ca. On average, based on soil concentrations and contents, forestry practices did not significantly deplete Ca in either cover type. Study results indicate that stand‐ and catchment‐scale forest Ca pools and fluxes can be used to identify areas potentially sensitive to Ca depletion and water quality degradation. However, considerable variation exists in Ca and acidification responses to external stressors, limiting spatial and temporal projections.
Journal Article
Variation in carbon and nitrogen concentrations among peatland categories at the global scale
Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg -1 and 13.9 ± 7.4 g kg -1 , with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg -1 ) and lowest in intermediate and extremely rich fens (375–414 g kg -1 ). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.
Journal Article
Peatland Microbial Community Composition Is Driven by a Natural Climate Gradient
Peatlands are important players in climate change–biosphere feedbacks via long-term net carbon (C) accumulation in soil organic matter and as potential net C sources including the potent greenhouse gas methane (CH₄). Interactions of climate, site-hydrology, plant community, and groundwater chemical factors influence peatland development and functioning, including C dioxide (CO₂) and CH₄ fluxes, but the role of microbial community composition is not well understood. To assess microbial functional and taxonomic dissimilarities, we used high throughput sequencing of the small subunit ribosomal DNA (SSU rDNA) to determine bacterial and archaeal community composition in soils from twenty North American peatlands. Targeted DNA metabarcoding showed that although Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla on average, intermediate and rich fens hosted greater diversity and taxonomic richness, as well as an array of candidate phyla when compared with acidic and nutrient-poor poor fens and bogs. Moreover, pH was revealed to be the strongest predictor of microbial community structure across sites. Predictive metagenome content (PICRUSt) showed increases in specific genes, such as purine/pyrimidine and amino-acid metabolism in mid-latitude peatlands from 38 to 45° N, suggesting a shift toward utilization of microbial biomass over utilization of initial plant biomass in these microbial communities. Overall, there appears to be noticeable differences in community structure between peatland classes, as well as differences in microbial metabolic activity between latitudes. These findings are in line with a predicted increase in the decomposition and accelerated C turnover, and suggest that peatlands north of 37° latitude may be particularly vulnerable to climate change.
Journal Article