Assessing the role of artificial compaction on physicochemical properties and carbon emissions of tropical peat soils

Compaction is undertaken because of claims that confined and restricted peat pores may enhance soil moisture due to the effect of capillary rise. The increase in soil moisture is said to lead to additional benefits of reduced C emissions and reduced risk and extent of peat fires. Nevertheless, information pertaining to induce compaction on peat physicochemical properties and carbon emission seems to be in scarcity. This thesis explored the notion of a misconception in definition of peat compaction in tropical peatland landscape due to confounding factors between (passive) natural compaction by oxidation, shrinkage and compression and (active) artificial compaction- by heavy machinery. This study suggest that this could be a reason for wide interpretation on peat compaction processes. Therefore, the aim of this research project was to assess the impact of artificial compaction on the tropical peat physicochemical properties and carbon emissions from peat surface as well through peat fire. To make such a contribution, a series of experiments was conducted at matured oil palm plantation (OP) and secondary peat swamp forest (SF) located in Selangor, Peninsular Malaysia. This study first to explore the source of compaction efforts in OP. Holding an assumption that microsites are different in term of bulk density value (compaction) due to agri-management, the findings are inconclusive. Despite fruitless experiment, this study continues to assess the potential and effects of artificial compaction by profile compaction magnitude (induce compaction efforts) on physicochemical properties and carbon emission by implementing in-situ and ex-situ approaches. The mechanisms of artificial compaction are explored further by measured and determined physicochemical properties and carbon emission from peat surface and fire. Subsequently, correlations between physicochemical properties and carbon emission were established. To simplify, this study yielded a number of main key findings: (1) Tropical peat compaction as marked by bulk density (BD) value in matured oil palm plantation relies on the degree of peat oxidation by periodical drainage. (2) It is challenging to achieve artificial compaction on tropical peatland due to labile soil organic matter that leads to self-regulatory mechanism through water table fluctuation. (3) Extremely low water table level and high labile carbon proportion may aid artificial compaction by consolidating varied decomposition degrees between peat horizons from surface and deeper peat. This resulted in average temporary inverse CO2 and CH4 emissions by the percentage ratio of ca. 1:2, and later, taken over by water table level control. (4) Oxidative or passive compaction leads to higher emission factor (EF) from fire path, owing to peat in advanced decomposition state. In other words, this study does not recommend applying artificial compaction to either land use type. Primarily this is because: (1) there is no effect from the practice on already drained peatlands; (2) undertaking this in degraded sites as a mechanism to reduce emissions as part of rehabilitation in sites marked for reforestation and rewetting would likely fail due to the fact that compressed peat will return to its original structure due to the increased water table fluctuation or even via rainfall, or any interaction with water sources such that the efforts to induce artificial compaction on tropical peatland are rendered useless; (3) when considered in relation to global warming potential, the results from compacting treatments within the forest soils indicated negligible CH4 emission in relation to CO2-eq though the enhancement is 2-fold greater than the reduction of CO2. As such the net effect is 41.1 t CO2-eq ha-1 yr-1 . However, even if net emissions are reduced by 33%, emissions are still not countered by organic matter inputs so are still net emissions to atmosphere. Furthermore, soils would still be are vulnerable to the “birch effect” when seasonal rewetting does occur. (4) To minimize fires moving forward as well the emissions from future fires, raising water tables will both reduce fire occurrence but will also contribute to decreasing BD value where fires do occur. This result also highlights that any efforts to compact peat as a mitigation measure against fire is in fact more likely to increase EFs overall. Lastly, it is suggested that the terminology of compaction should be differentiated according to the nature of compaction: (1) oxidative or shrinkage compaction or passive compaction —oxidation of peat due to lowered water table, causing peat to collapse and become compressed under its own weight; and (2) artificial or active compaction—induced by horizontal load compression that causes admixture (consolidation) between distinct degrees of decomposition in peat

Translocation of tropical peat surface to deeper soil horizons under compaction controls carbon emissions in the absence of groundwater

Compaction is recognized as an effective method for mitigating the risk of fires by enhancing soil moisture levels. This technique involves restricting peat pore spaces through compaction, facilitating improved capillary action for water retention and rehydration. The compaction of tropical peatlands, while beneficial for fire prevention, has the potential to influence biogeochemical processes and subsequent carbon emissions. The magnitude of compaction and groundwater level are strongly coupled in such environments, making it difficult to distinguish the control of physicochemical properties. Therefore, this study seeks to understand how peat compaction affects its properties, carbon emissions, and their relationship, with a focus on geophysical processes. Intact peat samples were collected from a secondary peat swamp forest and an oil palm plantation in Selangor, Peninsular Malaysia. Compaction treatments were applied to achieve three levels of volume reduction. CO2 and CH4 emissions were measured using an automated gas analyzer, and the physicochemical properties of the peat were determined. The results revealed that mechanical compaction significantly altered the physicochemical properties of the secondary forest peat, displaying an opposite pattern to the oil palm plantation, particularly regarding total nitrogen and sulfur. Moreover, the average reduction percentage ratio of CO2 emissions (from 275.4 to 182.0 mg m-2 hr-1; 33.9%) to CH4 uptakes (from -17.8 to -5.2 µg m-2 hr-1; 70.1%) (~1:2) indicated distinct stages of decomposition and translocation of less decomposed peat to deeper layers due to compaction, predominantly in secondary peat swamp forest samples. The oil palm plantation samples were unaffected by compaction in terms of physicochemical properties and carbon emissions, indicating the ineffectiveness of this approach for reducing fire risk in already drained systems. This study underscores the necessity of understanding the effects of compaction in the absence of groundwater to accurately evaluate the widespread application of this technique

High heterotrophic CO2 emissions from a Malaysian oil palm plantations during dry-season

Background Tropical peatlands are currently being rapidly cleared and drained for the establishment of oil palm plantations, which threatens their globally significant carbon sequestration capacity. Large-scale land conversion of tropical peatlands is important in the context of greenhouse gas emission factors and sustainable land management. At present, quantification of carbon dioxide losses from tropical peatlands is limited by our understanding of the relative contribution of heterotrophic and autotrophic respiration to net peat surface CO2 emissions. Methods In this study we separated heterotrophic and autotrophic components of peat CO2 losses from two oil palm plantations (one established in ‘2000’ and the other in 1978, then replanted in ‘2006’) using chamber-based emissions sampling along a transect from the rooting to non-rooting zones on a peatland in Selangor, Peninsular Malaysia over the course of three months (June-August, 2014). Collar CO2 measurements were compared with soil temperature and moisture at site and also accompanied by depth profiles assessing peat C and bulk density. Results The soil respiration decreased exponentially with distance from the palm trunks with the sharpest decline found for the plantation with the younger palms. The mean heterotrophic flux was 1244.7 ± SE 149.2 mg m-2h-1 and 663.8 ± SE 102.2 mg m-2h-1 at the 2000 and 2006 plantations, respectively. Autotrophic emissions adjacent to the palm trunks were 944 ± SE 99.7 mg m-2h-1 and 1962 ± SE 246 mg m-2h-1 at the 2000 and 2006 plantations, respectively. Heterotrophic CO2 flux was positively related to peat soil moisture, but not temperature. Total peat C stocks were 60 kg m-2 (down to 1 m depth) and did not vary among plantations of different ages but SOC concentrations declined significantly with depth at both plantations but the decline was sharper in the second generation 2006 plantation. Conclusions The CO2 flux values reported in this study suggest a potential for very high carbon (C) loss from drained tropical peats during the dry season. This is particularly concerning given that more intense dry periods related to climate change are predicted for SE Asia. Taken together, this study highlights the need for careful management of tropical peatlands, and the vulnerability of their carbon storage capability under conditions of drainage

Determining crystal structures through crowdsourcing and coursework

We show here that computer game players can build high-quality crystal structures. Introduction of a new feature into the computer game Foldit allows players to build and real-space refine structures into electron density maps. To assess the usefulness of this feature, we held a crystallographic model-building competition between trained crystallographers, undergraduate students, Foldit players and automatic model-building algorithms. After removal of disordered residues, a team of Foldit players achieved the most accurate structure. Analysing the target protein of the competition, YPL067C, uncovered a new family of histidine triad proteins apparently involved in the prevention of amyloid toxicity. From this study, we conclude that crystallographers can utilize crowdsourcing to interpret electron density information and to produce structure solutions of the highest quality

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK.

BACKGROUND: A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. METHODS: This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5 × 1010 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1 - relative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. FINDINGS: Between April 23 and Nov 4, 2020, 23 848 participants were enrolled and 11 636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0-75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4-97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; pinteraction=0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8-80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74 341 person-months of safety follow-up (median 3·4 months, IQR 1·3-4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. INTERPRETATION: ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials. FUNDING: UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, Bill & Melinda Gates Foundation, Lemann Foundation, Rede D'Or, Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK

Background A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. Methods This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5 × 1010 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1 - relative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. Findings Between April 23 and Nov 4, 2020, 23 848 participants were enrolled and 11 636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0–75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4–97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; pinteraction=0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8–80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74 341 person-months of safety follow-up (median 3·4 months, IQR 1·3–4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. Interpretation ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials

Assessing the role of artificial compaction on physicochemical properties and carbon emissions of tropical peat soils

Compaction is undertaken because of claims that confined and restricted peat pores may enhance soil moisture due to the effect of capillary rise. The increase in soil moisture is said to lead to additional benefits of reduced C emissions and reduced risk and extent of peat fires. Nevertheless, information pertaining to induce compaction on peat physicochemical properties and carbon emission seems to be in scarcity. This thesis explored the notion of a misconception in definition of peat compaction in tropical peatland landscape due to confounding factors between (passive) natural compaction by oxidation, shrinkage and compression and (active) artificial compaction- by heavy machinery. This study suggest that this could be a reason for wide interpretation on peat compaction processes. Therefore, the aim of this research project was to assess the impact of artificial compaction on the tropical peat physicochemical properties and carbon emissions from peat surface as well through peat fire. To make such a contribution, a series of experiments was conducted at matured oil palm plantation (OP) and secondary peat swamp forest (SF) located in Selangor, Peninsular Malaysia. This study first to explore the source of compaction efforts in OP. Holding an assumption that microsites are different in term of bulk density value (compaction) due to agri-management, the findings are inconclusive. Despite fruitless experiment, this study continues to assess the potential and effects of artificial compaction by profile compaction magnitude (induce compaction efforts) on physicochemical properties and carbon emission by implementing in-situ and ex-situ approaches. The mechanisms of artificial compaction are explored further by measured and determined physicochemical properties and carbon emission from peat surface and fire. Subsequently, correlations between physicochemical properties and carbon emission were established. To simplify, this study yielded a number of main key findings: (1) Tropical peat compaction as marked by bulk density (BD) value in matured oil palm plantation relies on the degree of peat oxidation by periodical drainage. (2) It is challenging to achieve artificial compaction on tropical peatland due to labile soil organic matter that leads to self-regulatory mechanism through water table fluctuation. (3) Extremely low water table level and high labile carbon proportion may aid artificial compaction by consolidating varied decomposition degrees between peat horizons from surface and deeper peat. This resulted in average temporary inverse CO2 and CH4 emissions by the percentage ratio of ca. 1:2, and later, taken over by water table level control. (4) Oxidative or passive compaction leads to higher emission factor (EF) from fire path, owing to peat in advanced decomposition state. In other words, this study does not recommend applying artificial compaction to either land use type. Primarily this is because: (1) there is no effect from the practice on already drained peatlands; (2) undertaking this in degraded sites as a mechanism to reduce emissions as part of rehabilitation in sites marked for reforestation and rewetting would likely fail due to the fact that compressed peat will return to its original structure due to the increased water table fluctuation or even via rainfall, or any interaction with water sources such that the efforts to induce artificial compaction on tropical peatland are rendered useless; (3) when considered in relation to global warming potential, the results from compacting treatments within the forest soils indicated negligible CH4 emission in relation to CO2-eq though the enhancement is 2-fold greater than the reduction of CO2. As such the net effect is 41.1 t CO2-eq ha-1 yr-1 . However, even if net emissions are reduced by 33%, emissions are still not countered by organic matter inputs so are still net emissions to atmosphere. Furthermore, soils would still be are vulnerable to the “birch effect” when seasonal rewetting does occur. (4) To minimize fires moving forward as well the emissions from future fires, raising water tables will both reduce fire occurrence but will also contribute to decreasing BD value where fires do occur. This result also highlights that any efforts to compact peat as a mitigation measure against fire is in fact more likely to increase EFs overall. Lastly, it is suggested that the terminology of compaction should be differentiated according to the nature of compaction: (1) oxidative or shrinkage compaction or passive compaction —oxidation of peat due to lowered water table, causing peat to collapse and become compressed under its own weight; and (2) artificial or active compaction—induced by horizontal load compression that causes admixture (consolidation) between distinct degrees of decomposition in peat

Sustainability of several cropping systems on Asajaya peatland

Cropping system is an important in soil sustainability. Physical and chemical properties with several of cropping systems on Asajaya peat land indicated variety of results. Kampung Pendam was the most sustain between the two of study areas. It showed appropriate chemical and physical properties that contribute to soil sustainability

Image_5_Translocation of tropical peat surface to deeper soil horizons under compaction controls carbon emissions in the absence of groundwater.jpeg

Compaction is recognized as an effective method for mitigating the risk of fires by enhancing soil moisture levels. This technique involves restricting peat pore spaces through compaction, facilitating improved capillary action for water retention and rehydration. The compaction of tropical peatlands, while beneficial for fire prevention, has the potential to influence biogeochemical processes and subsequent carbon emissions. The magnitude of compaction and groundwater level are strongly coupled in such environments, making it difficult to distinguish the control of physicochemical properties. Therefore, this study seeks to understand how peat compaction affects its properties, carbon emissions, and their relationship, with a focus on geophysical processes. Intact peat samples were collected from a secondary peat swamp forest and an oil palm plantation in Selangor, Peninsular Malaysia. Compaction treatments were applied to achieve three levels of volume reduction. CO2 and CH4 emissions were measured using an automated gas analyzer, and the physicochemical properties of the peat were determined. The results revealed that mechanical compaction significantly altered the physicochemical properties of the secondary forest peat, displaying an opposite pattern to the oil palm plantation, particularly regarding total nitrogen and sulfur. Moreover, the average reduction percentage ratio of CO2 emissions (from 275.4 to 182.0 mg m-2 hr-1; 33.9%) to CH4 uptakes (from -17.8 to -5.2 µg m-2 hr-1; 70.1%) (~1:2) indicated distinct stages of decomposition and translocation of less decomposed peat to deeper layers due to compaction, predominantly in secondary peat swamp forest samples. The oil palm plantation samples were unaffected by compaction in terms of physicochemical properties and carbon emissions, indicating the ineffectiveness of this approach for reducing fire risk in already drained systems. This study underscores the necessity of understanding the effects of compaction in the absence of groundwater to accurately evaluate the widespread application of this technique.</p

Image_6_Translocation of tropical peat surface to deeper soil horizons under compaction controls carbon emissions in the absence of groundwater.jpeg

Compaction is recognized as an effective method for mitigating the risk of fires by enhancing soil moisture levels. This technique involves restricting peat pore spaces through compaction, facilitating improved capillary action for water retention and rehydration. The compaction of tropical peatlands, while beneficial for fire prevention, has the potential to influence biogeochemical processes and subsequent carbon emissions. The magnitude of compaction and groundwater level are strongly coupled in such environments, making it difficult to distinguish the control of physicochemical properties. Therefore, this study seeks to understand how peat compaction affects its properties, carbon emissions, and their relationship, with a focus on geophysical processes. Intact peat samples were collected from a secondary peat swamp forest and an oil palm plantation in Selangor, Peninsular Malaysia. Compaction treatments were applied to achieve three levels of volume reduction. CO2 and CH4 emissions were measured using an automated gas analyzer, and the physicochemical properties of the peat were determined. The results revealed that mechanical compaction significantly altered the physicochemical properties of the secondary forest peat, displaying an opposite pattern to the oil palm plantation, particularly regarding total nitrogen and sulfur. Moreover, the average reduction percentage ratio of CO2 emissions (from 275.4 to 182.0 mg m-2 hr-1; 33.9%) to CH4 uptakes (from -17.8 to -5.2 µg m-2 hr-1; 70.1%) (~1:2) indicated distinct stages of decomposition and translocation of less decomposed peat to deeper layers due to compaction, predominantly in secondary peat swamp forest samples. The oil palm plantation samples were unaffected by compaction in terms of physicochemical properties and carbon emissions, indicating the ineffectiveness of this approach for reducing fire risk in already drained systems. This study underscores the necessity of understanding the effects of compaction in the absence of groundwater to accurately evaluate the widespread application of this technique.</p