1,720,996 research outputs found
Links between methane oxidation rates and methanotroph community composition in a pine forest soil
No full textThe main gap in our knowledge about what determines the rate of CH4 oxidation in forest soils is the biology of the microorganisms involved, the identity of which remains unclear. In this study, we used stable-isotope probing (SIP) following 13CH4 incorporation into phospholipid fatty acids (PLFAs) and DNA/RNA, and sequencing of methane mono-oxygenase (pmoA) genes, to identify the influence of variation in community composition on CH4 oxidation rates. The rates of 13C incorporation into PLFAs differed between horizons, with low 13C incorporation in the organic soil and relatively high 13C incorporation into the two mineral horizons. The microbial community composition of the methanotrophs incorporating the 13C label also differed between horizons, and statistical analyses suggested that the methanotroph community composition was a major cause of variation in CH4 oxidation rates. Both PLFA and pmoA-based data indicated that CH4 oxidizers in this soil belong to the uncultivated ‘upland soil cluster α’. CH4 oxidation potential exhibited the opposite pattern to 13C incorporation, suggesting that CH4 oxidation potential assays may correlate poorly with in situ oxidation rates. The DNA/RNA-SIP assay was not successful, most likely due to insufficient 13C-incorporation into DNA/RNA. The limitations of the technique are briefly discussed
Methane Production, Oxidation, and Emissions under Simulated Enhanced Nutrient Deposition in a Northern Peat Bog
Full text linkNorthern peatlands play a significant role in the global carbon (C) cycle by functioning as sources of atmospheric methane (CH4). Peatlands are becoming polluted as a result of nitrogen (N) deposition, which is likely to impact CH4 dynamics. This thesis presents research at the Mer Bleue bog (Ottawa, Canada) in the longest known simulated atmospheric nutrient deposition experiment. After 8 years of simulated N (and other nutrient) deposition, activities of microbial communities involved in CH4 cycling have been analyzed in the laboratory and CH4 fluxes measured using chamber techniques in the field. High rates (>10 times ambient deposition) of simulated N deposition decreased CH4 production, and enhanced CH4 oxidation in vitro. However, in situ CH4¬ emissions were greater in the high N plots. I hypothesize that CH4 production is therefore driven by short-lived root exudates in the field, consistent with increased shrub biomass that occurs concomitantly with high N deposition.MAS
Effects of forest equipment on boreal forest soils: a review
Full text linkSoil disturbance is an important aspect of forest harvesting operations. Machines that are responsible for the harvesting of trees and wood transportation have a direct effect on the soil that they operate on. Some of these machines can weigh dozens of tonnes, making their effect on the soil considerable; the degree of contact with soil also affects soil integrity. On improperly constructed roads and sensitive soils, these machines are a detriment to not just the soil itself, but the plants and wildlife that reside in the soil play dynamic roles cycling nutrients and organic matter and maintaining the ecology in forest ecosystems. Machine effects on boreal soil have been characterized and synthesized using a literature-review based approach, mainly focusing on western Canada and Ontario
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Mulch quality regulates soil fertility and microbial communities during a crop cycle
Full text linkContext
The benefits of plant-based mulch extend beyond improving soil physical properties as mulches hold value as a fertiliser and in maintaining robust soil microbial communities throughout the crop cultivation period.
Aims
We investigated the impact of plant-based mulch quality (comprising contrasting hemicellulose, cellulose, and lignin components) sourced from single and diverse species mixtures on soil fertility, microbial communities, crop yield, and seed quality by growing barley from seed to maturity in rhizotrons.
Methods
The treatments consisted of residue mixtures containing 17, 12, 6, and 1 grassland plant species, as well as wood chips, with a control group receiving no residues. Soil samples were collected at two time points, 69 and 195 days after mulch application, for nutrient and microbial phospholipid fatty acid analysis. Residues were analysed for hemicellulose, cellulose, and lignin content.
Key results
We found that high-quality residues, with low carbon:nitrogen ratio, low recalcitrance, and the highest nitrogen content decomposed most quickly and increased available soil potassium concentrations compared to residues of lower quality. The lower-quality residues retained a greater proportion of their initial fertilisation capacity, which was released gradually. There was a concomitant increase in soil microbial biomass at later stages of decomposition in residues of lower quality. Residue quality significantly affected crop seed quality but not yield.
Conclusions
Lower-quality residues can maintain their fertilisation capacity over a longer time horizon than higher-quality residues. Plant residue mulch can influence soil microbial biomass throughout the cultivation period, regardless of its initial quality, and can affect crop quality although this effect is slow and not always readily detectable.
Implications
These findings emphasise the importance of considering plant-based mulch quality in enhancing soil fertility and crop quality
Methane Production, Oxidation, and Emissions under Simulated Enhanced Nutrient Deposition in a Northern Peat Bog
No full textNorthern peatlands play a significant role in the global carbon (C) cycle by functioning as sources of atmospheric methane (CH4). Peatlands are becoming polluted as a result of nitrogen (N) deposition, which is likely to impact CH4 dynamics. This thesis presents research at the Mer Bleue bog (Ottawa, Canada) in the longest known simulated atmospheric nutrient deposition experiment. After 8 years of simulated N (and other nutrient) deposition, activities of microbial communities involved in CH4 cycling have been analyzed in the laboratory and CH4 fluxes measured using chamber techniques in the field. High rates (>10 times ambient deposition) of simulated N deposition decreased CH4 production, and enhanced CH4 oxidation in vitro. However, in situ CH4¬ emissions were greater in the high N plots. I hypothesize that CH4 production is therefore driven by short-lived root exudates in the field, consistent with increased shrub biomass that occurs concomitantly with high N deposition.MAS
Industrial residuals in land reclamation: enhancing soil recovery and ecological function in disturbed glacial soils
Full text linkThis dissertation investigates the reclamation potential of industrial residuals in remediating disturbed glacial soils in Northeastern Ontario. Focusing on two distinct yet similarly degraded landscapes — abandoned aggregate borrow pits and acid- and metal-affected mixed-wood forest soils in the Sudbury region — the research explores the application of industrial by-products to enhance soil fertility, facilitate revegetation, and support ecological restoration. The study is structured around three research objectives: first, assessing passive recolonization processes and dominant functional traits in abandoned borrow pits; second, evaluating the efficacy of industrial residues, including pulp and paper mill sludge, biomass boiler fly ash, and municipal biosolids, in improving borrow pit soil fertility and facilitating vegetation establishment; and third, testing the potential of these residues to ameliorate acidic and metal-laden soils for reforestation efforts in post-mining landscapes.
The research incorporates a thorough analysis of soil and vegetation dynamics, functional trait diversity, and soil-organism interactions across experimental and natural sites. By determining community-weighted mean (CWM) and Rao’s Quadratic Entropy Index analyses, the study quantifies the functional role of plant traits in supporting ecosystem resilience and stability of abandoned borrow pits. Results demonstrate the significant but variable effects of land applying industrial solids on soil quality, with implications for both nutrient dynamics and biological activity. Notably, the application of these residues to acidic soils supports positive vegetation outcomes, particularly for pioneer and stress-tolerant species adapted to low-nutrient environments. Additionally, findings highlight the challenges associated with northern soil reclamation, including frost heave and the limited microbial and nutrient availability in exposed, compacted substrates.
The research contributes to the understanding of reclamation strategies in regenerating forest ecosystems, emphasizing the importance of tailored, site-specific amendments to improve soil health and promote sustainable land recovery. The outcomes of this thesis have broad implications for land management policies in resource-extractive landscapes, underscoring the need for long-term monitoring, adaptive management, and integrated use of local industrial by-products to restore ecosystem functionality in severely degraded soils
Soil Nutrient and Greenhouse Gas Cycles in Managed Mixed Deciduous Ontario Forests: The Role of Elevated Atmospheric Nitrogen Deposition and Nutrient and Biochar Amendments
No full textCanada’s temperate forests are experiencing an environmental disturbance in the form of atmospheric nitrogen deposition arising from fossil fuel burning and agricultural practices. Nitrogen, a major nutrient required for plants and soil microorganisms, is normally in short supply in temperate forest ecosystems. However, when soil nitrogen is in excess, various negative impacts can result such as nutrient leaching, increased nitrous oxide emissions and disturbances to carbon cycling, including reduced soil methane uptake. Research has revealed a shift from nitrogen to phosphorus limitation in forests in central Ontario where chronic nitrogen deposition rates are high, and introducing soil amendments might have the potential to mitigate these negative effects. Before management strategies can be devised, it is important to characterize the degree of nitrogen excess, and how soil nutrient cycling and fluxes of greenhouse gases are being influenced, which may offset carbon gains from increased primary productivity. In an assessment of ambient soil characteristics representing natural topographic heterogeneity at Haliburton Forest, high inorganic nitrogen pools did not result in elevated nitrous oxide effluxes in upland soils, though hot spots and hot moments of nitrous oxide efflux occurred in wet depression areas where ammonium concentrations and moisture were high. Rapid methane efflux was also observed including what appear to be the highest rates in forest systems reported to date. A reduction in longer- (>5 year) and shorter-term (0-3 year) inorganic nitrogen pools in upland phosphorous-amended sites does support that the forest is phosphorous limited, however, there was no evidence of increased nitrous oxide emissions, even in nitrogen-amended sites that would be expected under nitrogen saturated conditions. Phosphorous limitation may be ameliorated by amending soils with biochar, which resulted in increased soil phosphorus, pH, and cation retention. The results of this research reveal that soils in temperate forests in Ontario are at a stage of nitrogen excess relative to ecosystem demands, but do not appear to have reached nitrogen saturation. However, with elevated exchangeable nitrogen pools and increasing nitrogen deposition, denitrification and methanogenic potentials, particularly under predicted increasing moisture regimes, may substantially impact and offset the overall carbon sink at this forest.Ph.D
Microbial Community Composition and Activities Across Northern Peatlands
No full textNorthern peatlands are large repositories of carbon and little is known about the effect the microbial community has on carbon mineralization rates, and there is concern that a loss of microbial diversity due to environmental change may lead to reduced ecosystem functioning. Microbial communities vary among peatland types and abiotic variables such as temperature and pH have a large influence on carbon dioxide production, but distinguishing between abiotic controls and the role of microbial community structure has proved challenging.
Microbial activity and community composition was characterized in three peatlands within the James Bay Lowlands, Ontario. Similar dominant microbial taxa were observed at all three peatlands despite differences in nutrient content and substrate quality and geographic location. In contrast, microbial activity differed among the sites, indicating that it is influenced by the quality of the peat substrate and the presence of microbial inhibitors.
A series of reciprocal field and laboratory transplant experiments were conducted at a rich and poor fen near White River, Ontario to more explicitly distinguish between the abiotic and microbial controls on carbon mineralization. The effect of transplantation differed between the laboratory and field studies and when viewed individually could lead to different interpretations of the effect of substrate change. Surprisingly, intensive sampling within both fens was unable to reveal a difference between the rich and poor fen microbial community due to high within site temporal and spatial variation. Thus studies with small sampling effort will have a very incomplete understanding of microbial community structure and thus microbial ecology.
A reciprocal sterilization transplant experiment was also conducted to examine how different microbial communities adapted to various peat substrates influenced C-mineralization patterns. Post-inoculation/incubation bacterial communities across peatlands converged towards a similar community structure, suggesting that abiotic variables are the dominant control on peatland microbial activity and community composition.
The studies presented in this thesis collectively show that across a broad range of temperate and sub-arctic peatland types dominant members of the microbial community are generally similar, and decomposition rates can be predicted by broader controlling environmental factors rather than temporal niche or distributional constraints of the microbial community.Ph
Microbial Community Composition and Activities Across Northern Peatlands
No full textNorthern peatlands are large repositories of carbon and little is known about the effect the microbial community has on carbon mineralization rates, and there is concern that a loss of microbial diversity due to environmental change may lead to reduced ecosystem functioning. Microbial communities vary among peatland types and abiotic variables such as temperature and pH have a large influence on carbon dioxide production, but distinguishing between abiotic controls and the role of microbial community structure has proved challenging.
Microbial activity and community composition was characterized in three peatlands within the James Bay Lowlands, Ontario. Similar dominant microbial taxa were observed at all three peatlands despite differences in nutrient content and substrate quality and geographic location. In contrast, microbial activity differed among the sites, indicating that it is influenced by the quality of the peat substrate and the presence of microbial inhibitors.
A series of reciprocal field and laboratory transplant experiments were conducted at a rich and poor fen near White River, Ontario to more explicitly distinguish between the abiotic and microbial controls on carbon mineralization. The effect of transplantation differed between the laboratory and field studies and when viewed individually could lead to different interpretations of the effect of substrate change. Surprisingly, intensive sampling within both fens was unable to reveal a difference between the rich and poor fen microbial community due to high within site temporal and spatial variation. Thus studies with small sampling effort will have a very incomplete understanding of microbial community structure and thus microbial ecology.
A reciprocal sterilization transplant experiment was also conducted to examine how different microbial communities adapted to various peat substrates influenced C-mineralization patterns. Post-inoculation/incubation bacterial communities across peatlands converged towards a similar community structure, suggesting that abiotic variables are the dominant control on peatland microbial activity and community composition.
The studies presented in this thesis collectively show that across a broad range of temperate and sub-arctic peatland types dominant members of the microbial community are generally similar, and decomposition rates can be predicted by broader controlling environmental factors rather than temporal niche or distributional constraints of the microbial community.Ph
Soil Nutrient and Greenhouse Gas Cycles in Managed Mixed Deciduous Ontario Forests: The Role of Elevated Atmospheric Nitrogen Deposition and Nutrient and Biochar Amendments
Full text linkCanada’s temperate forests are experiencing an environmental disturbance in the form of atmospheric nitrogen deposition arising from fossil fuel burning and agricultural practices. Nitrogen, a major nutrient required for plants and soil microorganisms, is normally in short supply in temperate forest ecosystems. However, when soil nitrogen is in excess, various negative impacts can result such as nutrient leaching, increased nitrous oxide emissions and disturbances to carbon cycling, including reduced soil methane uptake. Research has revealed a shift from nitrogen to phosphorus limitation in forests in central Ontario where chronic nitrogen deposition rates are high, and introducing soil amendments might have the potential to mitigate these negative effects. Before management strategies can be devised, it is important to characterize the degree of nitrogen excess, and how soil nutrient cycling and fluxes of greenhouse gases are being influenced, which may offset carbon gains from increased primary productivity. In an assessment of ambient soil characteristics representing natural topographic heterogeneity at Haliburton Forest, high inorganic nitrogen pools did not result in elevated nitrous oxide effluxes in upland soils, though hot spots and hot moments of nitrous oxide efflux occurred in wet depression areas where ammonium concentrations and moisture were high. Rapid methane efflux was also observed including what appear to be the highest rates in forest systems reported to date. A reduction in longer- (>5 year) and shorter-term (0-3 year) inorganic nitrogen pools in upland phosphorous-amended sites does support that the forest is phosphorous limited, however, there was no evidence of increased nitrous oxide emissions, even in nitrogen-amended sites that would be expected under nitrogen saturated conditions. Phosphorous limitation may be ameliorated by amending soils with biochar, which resulted in increased soil phosphorus, pH, and cation retention. The results of this research reveal that soils in temperate forests in Ontario are at a stage of nitrogen excess relative to ecosystem demands, but do not appear to have reached nitrogen saturation. However, with elevated exchangeable nitrogen pools and increasing nitrogen deposition, denitrification and methanogenic potentials, particularly under predicted increasing moisture regimes, may substantially impact and offset the overall carbon sink at this forest.Ph.D
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