Peat Decomposition Research Articles

Peat profile database from peatlands in Canada.

Peatlands cover approximately 12% of the Canadian landscape and play an important role in the carbon cycle through their centennial- to millennial-scale storage of carbon under waterlogged and anoxic conditions. In recognizing the potential of these ecosystems as natural climate solutions and therefore the need to include them in national greenhouse gas inventories, the Canadian Model for Peatlands module (CaMP v. 2.0) was developed by the Canadian Forest Service. Model parameterization included compiling peat profiles across Canada to calibrate peat decomposition rates from different peatland types, to define typical bulk density profiles, and to describe the hydrological (i.e., water table) response of peatlands to climatic changes. A total of 1217 sites were included in the dataset from published and unpublished sources. The CORESITES table contains site location and summary data for each profile, as well as an estimate of total carbon mass per unit area (in megagrams of C per hectare). Total carbon mass per unit area at each location was calculated using bulk density and carbon content through each profile. The PROFILES table contains data for depth (in centimeters), bulk density (in grams per cubic meter), ash and carbon content (in percentage), and material descriptions for contiguous samples through each peat profile. Data gaps for bulk density and C content were filled using interpolation, regression trees, and assigned values based on material description and/or soil classification to allow for the estimation of total carbon mass per unit area. A subset of the sites (N = 374) also have pH and pore water trace-elemental geochemistry data and are found in the WATER table. The REFERENCES table contains the full citation of each source of the data and is linked to each core location through the SOURCEDATA table. The LOOKUP table defines codes in the database that required more space that what was sufficient in the metadata tables. The data can be accessed on Open Government Canada and will be useful for future work on carbon stock mapping and ecosystem modeling. All metadata and data are provided © Her Majesty the Queen in Right of Canada, 2023 and information contained in this publication may be reproduced for personal or public noncommercial purposes with attribution, whereas commercial reproduction and distribution are prohibited except with written permission from NRCan; complete details are noted in the Supporting Information file Metadata S1 (see Class III.B.3: Copyright restrictions).

Rewetting on agricultural peatlands can offer cost effective greenhouse gas reduction at the national level

To reach EU’s carbon neutrality target by 2050, emission reductions in the land-use sector are needed. Agricultural peatlands attribute for half of the greenhouse gas emissions of cropland in both in EU and Finland. High greenhouse gas emissions from agricultural peatlands are primarily caused by CO2 emissions following aerobic peat decomposition due to deep drainage, and studies have shown that raising water-table has potential to slow down the decomposition process. Here we studied the emission reduction potential and cost of implementing controlled drainage, paludiculture, peatland restoration and afforestation to current land use on agricultural peatlands in Finland. We created three scenarios with increasing amount of wet field use on cultivated organic soils and estimated their effects on national greenhouse gas emissions and farmers’ income. The yearly emission reduction ranged from 0.3 to 5.0 Mt CO2 equivalents in the different scenarios compared to the current state in Finland. Emission reductive land use had a negative impact on the farmers income, which should be compensated. Assuming the government compensates the lost income for the farmers, the cost of emission reduction ranged from −4 to 45 € per ton of CO2 equivalents. Rewetting provided the most emission reduction per area and was the most cost effective. We conclude that substantial emission reduction is attainable by rewetting agricultural peatlands. The cost of emission reduction is inexpensive compared to average carbon price in European Union emission trading system, or to the costs of technical carbon capture and storage in Finland.

Tropical peat composition may provide a negative feedback on fire occurrence and severity

Loss of peat through increased burning will have major impacts on the global carbon cycle. In a normal hydrological state, the risk of fire propagation is largely controlled by peat bulk density and moisture content. However, where humans have interfered with the moisture status of peat either via drainage, or indirectly via climate change, we hypothesise that its botanical composition will become important to flammability, such that peats from different latitudes might have different compositionally-driven susceptibility to ignition. We use pyrolysis combustion flow calorimetry to determine the temperature of maximum thermal decomposition (Tmax) of peats from different latitudes, and couple this to a botanical composition analysis. We find that tropical peat has higher Tmax than other regions, likely on account of its higher wood content which appears to convey a greater resistance to ignition. This resistance also increases with depth, which means that loss of surface peat in tropical regions may lead to a reduction in the subsequent ignitability of deeper peat layers as they are exposed, potentially resulting in a negative feedback on increased fire occurrence and severity.

Holocene storminess dynamics in northwestern Ireland: Shifts in storm duration and frequency between the mid- and late Holocene

Substantial uncertainties exist regarding how future climate change will affect storminess (storm frequency and intensity) in Ireland and the United Kingdom (UK). Knowledge about spatiotemporal variations of past storminess gives us a better understanding of its mechanisms on centennial to millennial time scales, as well as the impact of external forcing on future storminess in climate models. Here, we present the oldest storm record to date from Ireland, covering the last 8000 years, reconstructed from the Roycarter Bog, a coastal blanket bog in north-western Ireland. The sequence was analysed for grain-size, chemical, mineral and organic molecular composition. The chronology was built on 11 AMS radiocarbon dates. The deposit characteristics, location and low inorganic content suggest aeolian transport of particles to the bog throughout the studied period. Cluster analysis of the grain-size frequency curves, along with the coarse to fine sand ratio, allowed the identification of eleven storm periods (cal yr BP): 6150–5500 (1); 4970–4130 (2); 4000 (3); 3490–3290 (4); 3230 (5); 2850–2590 (6); 2170–1920 (7); 1440 (8); 1225–890 (9); 620–470 (10); and 290–230 (11).During the mid-Holocene, the relative sea level was lower and the local beach sources located further away, giving a longer transport distance compared to the late Holocene. In the latter part of the mid-Holocene (6150–4130 cal yr BP), during the Holocene thermal maximum, increased storminess and wind strengths were inferred for north-western Ireland, manifested as two longer storm periods. During the late Holocene the storm frequency increased, and a greater number (9) of shorter storm periods were recorded. Comparison between our results and regional peat palaeostorm records from Scotland, north of our study site, showed an antiphase relationship between storminess in Ireland and Scotland during the latter part of the mid-Holocene, but mostly in-phase storminess over the last 3000 years. Taken together, enhanced wind strength and storminess were recorded during the warmer mid-Holocene, while an increased frequency of storm events occurred in the cooler late Holocene. Mid-Holocene storm periods occurred during locally wet periods, while most of the storm periods during late Holocene occurred during drier phases. Alternatively, the elevated mineral input during late Holocene promoted microbial activity and peat decomposition. The apparent variability in cyclicity and frequency between the mid- and late Holocene indicates that the processes governing storminess in the region shifted. This calls for further studies ahead, including climate modelling, to disentangle the complex processes governing storminess on millennial to centennial time scale.

Late Holocene changes in the water table at an alkaline fen in Central Latvia: Their impacts on CaCO3 deposition at the fen and relation to the hydroclimate patterns of the Eastern Baltic Region

Sediments of CaCO3-precipitating alkaline fens, comprising biotic and abiotic indicators of water table changes, are among the most reliable archives for obtaining palaeohydrological data. The study uses a semiquantitative method based on a combination of selected indicators (plant macrofossils, mollusc shells, degree of peat decomposition) to estimate the relative changes in the water table position at Lustūžkalns alkaline fen, Latvia, Eastern Baltic Region. The study also aims to determine the time frames of CaCO3 deposition at the fen using loss on ignition and carbon and oxygen stable isotope records. The chronology of the three sediment sequences studied is based on the AMS radiocarbon dating of terrestrial plant macrofossils. Although the reconstructed water table positions revealed differences between the cores, the major shift from the low water tables persisting since ca. 5000 cal yr BP to the prevailing high water stands at ca. 3000 cal yr BP was common to all the sequences. The major shift observed is consistent with a change from low to high water tables in peatlands in Latvia and at numerous fens and bogs across the Eastern Baltic Region, Fennoscandia and NW Europe. Concurrent with the increase in the water tables was the onset of CaCO3 precipitation on the Lustūžkalns fen surface, which began at ca. 3000 cal yr BP and accelerated from ca. 2500 cal yr BP. The Late Holocene CaCO3 precipitation at Lustūžkalns can be attributed to the change from warm and dry conditions during the Holocene Thermal Maximum (HTM) to cooler but humid during the Late Holocene. In contrast, in Central and Western Europe, the main period of freshwater carbonate precipitation occurred during the warm and humid HTM.

Organic matter decomposition in mountain peatlands: effects of substrate quality and peatland degradation

Abstract Background and Aims Peatlands occupy only 3% of Earth’s terrestrial lands but store about one-third of global soil carbon. However, these large carbon stocks are currently under threat due to peatland degradation, where altered hydrological balance could enhance peat oxidation; thus releasing large amounts of CO2 into the atmosphere. We investigated the interactive effects of substrate quality, peat depth and peatland degradation on the decomposition rate of organic matter in peatlands by way of a field incubation experiment. Methods We incubated high-quality fresh peat and a lower-quality degraded peat substrate at three different depths (5, 15, and 30 cm) in two (intact and degraded) mountain peatlands for 18 months. Our results indicated that there is a significant interactive effect of substrate quality, peat depth, and peatland type on the peat decomposition rate. Results The fresh peat showed significantly higher decomposition rates than the degraded peat substrate, likely due to the high percentage of bioavailable carbon in the fresh moss substrate. In the degraded peatland, fresh peat at 30 cm showed no mass loss during the incubation period, likely due to the high-water table creating anaerobic conditions. The fresh peat incubated in the intact peatland showed a higher decomposition rate than the same substrate incubated in the degraded peatland due to the comparatively lower water table in the intact peatland. Conclusions Our findings indicate that the quality of the substrate being decomposed and the depth of the water table act as the main factors affecting the decomposition rate in mountain peatlands.

Peatland carbon chemistry, amino acids and protein preservation in biogeochemically distinct ecohydrologic layers

AbstractPeatlands play a significant role in global carbon and nitrogen cycles due to their carbon storage capabilities. However, there are key knowledge gaps in our understanding of how peatland hydrology influences the biogeochemical properties that drive peatland functioning and health. This study examines peatland hydrology and biogeochemical dynamics by exploring the variations in carbon chemistry, total amino acid (‘protein’) content and amino acid composition in the ecohydrologic layers: acrotelm, mesotelm and catotelm. The dynamic movement of the water table recorded half‐hourly over 4 years was used to assist in identifying the boundaries between these layers. Peat amino acids were measured using liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). Carbon chemistry was analysed by solid state Cross Polarization Magic Angle Spinning (CPMAS) 13C Nuclear Magnetic Resonance (NMR) spectroscopy, with the alkyl:O‐alkyl ratio used to quantify the extent of decomposition. Our result revealed a strong positive correlation between the extent of decomposition and total protein content, indicating selective preservation of proteinaceous materials during peat decomposition. Each ecohydrologic layer displayed a distinct amino acid composition and carbon functional group composition. The acrotelm was relatively enriched in seven amino acids and two carbon functional groups. The mesotelm was relatively enriched in four amino acids, while the catotelm was relatively enriched in three amino acids and four carbon functional groups. The variations in amino acid composition reflect differences in microbial function and efficiency, while variations in carbon functional groups provide insights into long‐term carbon sequestration in peatland. Collectively, these results provide more insights into nutrient cycling and changes in organic matter composition during peat decomposition. These findings demonstrate that peatland biogeochemistry is closely linked to ecohydrology and suggest that changes to water table dynamics could affect the ability of peatlands to sequester and store carbon in the future.

Aerobic and anaerobic decomposition rates in drained peatlands: Impact of botanical composition

Drained peatlands in temperate climates are under threat from climate change and human activities. The resulting decomposition of organic matter plays a major role in regulating the associated land subsidence rates, yet the determinants of aerobic and anaerobic peat decomposition rates are not fully understood. In this study, we sought to gain insight into the drivers of decomposition rates in botanically diverse peatlands (sedge, reed, wood, and moss dominant) under oxic and anoxic conditions. Peat samples were collected from the anoxic zone and incubated for 24 h (short) and 15 weeks (long) under either oxic or anoxic conditions. CO2 emissions, hydrolytic and oxidative exoenzyme potential activities, phenolic compound concentrations, and several edaphic factors were measured at the end of each incubation period.We found that 15 weeks of oxygen exposure of anoxic peat samples accelerated the average CO2 emissions by 3.9-fold. Reed and sedge peat respired more than wood and moss peat under anoxic conditions. Interestingly, CO2 emissions from anoxic peat layers under permanently anoxic conditions were substantial and given the thickness of peat deposits in the field, such activities may play an important role in long-term land subsidence rates and total CO2 emissions from drained peatlands. The results from the long-term incubations showed that decomposition rates appear to be also controlled by factors other than oxygen intrusion such as substrate availability. In summary, the botanical composition of the peat matrix, incubation conditions and time of incubation are all important factors that need to be considered when predicting peat decomposition and subsequent land subsidence rates.

Large variation in carbon dioxide emissions from tropical peat swamp forests due to disturbances

The huge carbon stock of tropical peat swamp forest (PSF) in Southeast Asia has been threatened by environmental disturbances due to quasi-periodic El Niño-Southern Oscillation (ENSO) droughts, biomass and peat burning, smoke haze, drainage, and deforestation. Carbon dioxide (CO2) emissions from such disturbances have not been well quantified because of insufficient field data. Therefore, we quantified the ecosystem-scale CO2 balance and examine the disturbance effects from a long-term field experiment for 12–15 years at three PSF sites with different degrees of degradation in Indonesia. Here, we show a drastic change of an undrained PSF from a CO2 sink to a source owing to the transient groundwater lowering by the droughts, a significant decrease in ecosystem photosynthesis due to the radiation attenuation by smoke haze in drought years, and long-lasting CO2 emissions through enhanced peat decomposition by drainage. The impact on CO2 emissions was greater from drainage than drought-induced disturbances.

Soil Cover Modifications in Vicinity of Disappearing Lakes as a Result of Climate Change

Abstract Disappearance of lakes is one of the most dangerous processes affecting the entire natural environment, including soil. This phenomenon is considered natural, resulting from climate change, however in recent decades, a significant acceleration of this process has been observed due to the direct impact of human activity. In areas directly adjacent to lakes, organic soils usually predominate. Unfortunately, wetlands are increasingly being drained and used for agricultural purposes. Under such circumstances, changes in the physical and chemical properties of these soils are often irreversible, causing their degradation. As an effect of increased mineralization, a number of typical modifications occur in soils, such as carbon loss, increased degree of peat decomposition, and changes in soil structure. Long-term dehydration has led to muck formation. Additionally, lowering of lake water uncovers previously flooded areas and increases the intensity of soil-forming processes. However, the presence of the Subaquatic qualifier in the World Reference Base for Soil Resources (WRB) suggests that sediments in shallow water bodies no more than 200 cm deep can also be classified as soils. The progressive disappearance of lakes observed all over the world is therefore a process affecting not only the reduction of water bodies, but also changes in the properties and typology of soils and vegetation cover.

Progress towards adopting low-carbon agriculture on peatlands for sustainable development in Indonesia

Indonesia, progressing towards sustainable development, faces the complex task of transitioning to low-carbon agriculture in peatlands, an essential part of broader sustainable objectives. Under the Paris Agreement, it targets a conditional 41% emission reduction, focusing on minimizing emissions from peat decomposition and fires within agricultural practices in peatlands. This paper explores the complexities and progress of low-carbon agriculture in peatlands, underscoring its significance in the larger sustainable development agenda. Our study reveals that current strategies to reduce carbon emissions in peatlands aim at restoring their natural waterlogged conditions. Yet, progress is hindered mainly due to an inadequate understanding of greenhouse gas emissions from peatlands and overlooking their unique features, which leads to overestimated emissions from agricultural use. For improved strategies, it’s important to analyze successful existing sustainable practices and enhance understanding of peatland ecology. Techniques like the “Water Management Trinity,” implemented since 1986, and eco-management emphasize the importance of using permanent water gates to maintain water levels optimal for both peat preservation and crop production. Over time, these practices modify peatland attributes, making emissions comparable to those from mineral soil, thus rendering low-carbon agriculture attainable. It’s vital for stakeholders to assess emissions with updated data, incorporating detailed information on peatland characteristics and emissions. The journey towards low-carbon agriculture in Indonesia’s peatlands is a complex endeavor necessitating the amalgamation of scientific research, sustainable practices, and socio-economic development. Adopting a holistic approach can strike a balance between agricultural productivity, peatland conservation, and climate change mitigation, fulfilling sustainable development goals in Indonesia and globally.

Potential of APSIS-InSAR for measuring surface oscillations of tropical peatlands.

Tropical peatland across Southeast Asia is drained extensively for production of pulpwood, palm oil and other food crops. Associated increases in peat decomposition have led to widespread subsidence, deterioration of peat condition and CO2 emissions. However, quantification of subsidence and peat condition from these processes is challenging due to the scale and inaccessibility of dense tropical peat swamp forests. The development of satellite interferometric synthetic aperture radar (InSAR) has the potential to solve this problem. The Advanced Pixel System using Intermittent Baseline Subset (APSIS, formerly ISBAS) modelling technique provides improved coverage across almost all land surfaces irrespective of ground cover, enabling derivation of a time series of tropical peatland surface oscillations across whole catchments. This study aimed to establish the extent to which APSIS-InSAR can monitor seasonal patterns of tropical peat surface oscillations at North Selangor Peat Swamp Forest, Peninsular Malaysia. Results showed that C-band SAR could penetrate the forest canopy over tropical peat swamp forests intermittently and was applicable to a range of land covers. Therefore the APSIS technique has the potential for monitoring peat surface oscillations under tropical forest canopy using regularly acquired C-band Sentinel-1 InSAR data, enabling continuous monitoring of tropical peatland surface motion at a spatial resolution of 20 m.

Analisis Emisi Karbon di Kesatuan Hidrologi Gambut Sungai Mendahara - Sungai Batanghari

Global Warming Due to Carbon Emissions is a threat to life on earth. According to the World Meteorological Organization, the earth's temperature rose by 1.06 °C to 1.26 °C above pre-industrial levels (1850–1900). According to the IPCC report (2021), the impacts of climate change will reach all regions in the world without exception. Indonesia's commitment to reduce carbon emissions by 29% with its efforts and 41% with international cooperation until 2030. Analysis of land cover uses the Unsupervised Classification, the method for calculating carbon emissions above the surface uses the IPCC method, namely the stock differential and the method for analyzing emissions of peat decomposition uses the Hooijer formula et al. (2006, 2010) with estimated water level from the TMAT BRGM data regression equation with NDWI Landsat 8 values then total carbon emissions by adding emissions from above and below the surface. Based on the results of the analysis of land cover at the research location, the area was dominated by plantations at 37.8%, while the forest area was only 7.9%. Ground carbon emissions average 0.23 Mt CO2-eq per year, below Ground carbon emissions are 9.94 Mt CO2-eq and total carbon emissions are 10.17 Mt CO2-eq with total emissions from 2013 - 2022 of 91.6 Mt CO2-eq Carbon emissions in KHG Sungai Mendahara - Batanghari graphically fluctuate, there is an increase and decrease but tends to increase until 2022 this is due to land conversion and massive land clearing in forest areas and the biggest contributor to carbon emissions from decomposition peatlands.

Rewetting drained peatlands through subsoil infiltration stabilises redox-dependent soil carbon and nutrient dynamics

Centuries of drainage have stimulated peat decomposition. To counteract the resulting increase in greenhouse gas emission and land subsidence in Dutch agricultural peatlands, passive and active subsurface infiltration (SSI) systems have been developed for peatland rewetting. Here, we studied the effects of SSI systems on groundwater levels, porewater composition and redox potential in four drained peatlands in the Netherlands to determine how soil processes are affected, especially carbon and nutrient dynamics. For three years, groundwater levels were measured continuously, and porewater samples were collected 8–10 times per year in paired SSI (active and passive) and control plots. SSI plots had higher summer groundwater levels and less seasonal fluctuation in groundwater levels than control plots. Redox potential and porewater composition in control plots reflected dominance of oxidation processes during dry periods in the upper soil layers, whereas SSI plots showed dominance of reduction processes in these layers throughout the year. These differences between control and SSI plots were strongest at locations with active SSI systems. Our results show that SSI systems can be effective measures to raise and stabilise groundwater levels in drained peatlands, which results in more stable redox zonation and dominance of anaerobic soil processes, especially during dry periods and when active SSI systems are applied. On the short term, a switch from oxic to anoxic conditions can cause mobilisation of phosphorus and ammonium, while on the longer term the application of SSI can lead to substantial change in carbon and nutrient dynamics. Understanding the full effects of implementing SSI systems and other mitigation measures in drained peatlands is important before they are applied on a large scale.

Sources of nitrous oxide emissions from agriculturally managed peatlands.

The draining and fertilization of peatlands for agriculture is globally an important source of the greenhouse gas nitrous oxide (N2 O). Hitherto, the contribution of major sources to the N2 O emission-that is, fertilization and nitrogen (N) release from peat decomposition-has not yet been deciphered. This hampers the development of smart mitigation strategies, considering that rewetting to halt peat decomposition and reducing N fertilization are promising N2 O emission-reduction strategies. Here, we used machine learning techniques and global N2 O observational data to generalize the distribution of N2 O emissions from agriculturally managed peatlands, to distinguish the sources of N2 O emissions, and to compare mitigation options. N2 O emissions from agriculturally managed croplands were 401.0 (344.5-470.9) kt N year-1 , with 121.6 (88.6-163.3) kt N year-1 contributed by fertilizer N. On grasslands, 64.0 (54.6-74.7) kt N2 O-N year-1 were emitted, with 4.6 (3.7-5.7) kt N2 O-N year-1 stemming from fertilizer N. The fertilizer-induced N2 O emission factor ranged from 1.5% to 3.2%. Reducing the current fertilizer input by 20% could achieve a 10% N2 O emission reduction for croplands but only 3% for grasslands. Rewetting 1.9 Mha cropland and 0.26 Mha grassland would achieve the same N2 O emission reductions. Our results suggest that N2 O mitigation strategies for managed peatlands should be considered separately across land-use types and climatic zones. For croplands, particularly in the tropics, relevant N2 O mitigation potentials are achievable through both fertilizer N reduction and peatland rewetting. For grasslands, management schemes to halt peat degradation (e.g. rewetting) should be considered preferentially for mitigating N2 O and contributing to meeting climate goals.

The Holocene evolution of floodplain mire geosystems in the southeastern part of the Meshchera lowlands

The results of paleoecological studies of peat deposits in the area of the southeastern part of the Meshchera lowlands (Mostovoye mire) based on the analyses of peat properties, plant macrofossils, charcoal, pollen and radiocarbon dating are presented. The mire was formed in the oxbow depression on the floodplain of the Goose River around 9480 cal. yr. BP and was eutrophic throughout most of the Holocene. Drastic changes in the dynamics of the mire, namely its transition to the mesotrophic stage, characterized by a decrease in the degree of peat decomposition, occurred about 70 years ago. The results of the pollen analysis show the existence of birch-pine forests in combination with shrub thickets formed by Betula nana in the period 9480-8750 cal. yr. BP. In the subsequent stages, the vegetation cover turned to a combination of broad-leaved, birch-pine forests and riverine forests with alder. Frequent fires, both natural and anthropogenic, have favored the development of birch and pine forests over the last millennium.

Transformation of peat deposits and carbon accumulation in post-pyrogenic raised bogs within the taiga zone of West Siberia

The aim of the study was to assess of the transformation of the hydrologic and physical properties of peat deposits and peat accumulation rates in the post-pyrogenic sites of drained fens in the taiga zone of West Siberia. Location and time of the study. Field studies were conducted in 2022 on the Bakchar fen (drained for forestry, seven plots) and Ust-Bakchar fen (drained for peat extraction, three plots) located in the Tomsk region. Methods. Peat sampling was carried out from two boreholes at each plot in the hollow and the hummock. The sampling increment was 5 cm; the total depth was 45–90 cm. Peat samples were taken at nine subsites by the envelope method on each plot in 0–30 cm layer by 10 cm increment for water content determination in laboratory. Laboratory study of peat characteristics was carried out using the following methods: water and ash content measurements (GOST 11306-2013, GOST 11306-2013), estimation of peat decomposition and humification degree, botanical composition (GOST 28245-89), as well as measuring peat bulk density. Carbon stocks in the upper layer of peat deposits was estimated using the values of peat ash content and density. Results. The peat deposit of the upper layers was formed mainly by sphagnum peat with Sphagnum fuscum plant residues predominating. The differences between hollows and hummocks in their peat properties were manifested to a depth of 5–15 cm from the surface of depressions. The burnout of the hollows led to the changes of all peat properties to a depth of 10–15 cm: the changes were more pronounced in ash content, which was 1.5–9 times higher in the 0–5 cm layer as compared with the unburned site. The changes in peat properties on positive relief forms, i.e. moss hummocks, was less evident in the upper 0–5 cm layer, but reached a greater depth of 30 cm. The change was revealed mainly as an increase in peat ash content due to the migration of ash elements from the surface of burnt hollows and as an increase in bulk density due to subsidence of moss hummocks with the died-off sphagnum moss. Although the average water content in postpyrogenic and unburned sites was the same, amounting to 90–91% in the 0–30 cm layer, some difference was observed between the microrelief forms. The post-pyrogenic site in the Bakchar fen was characterized by water content decrease in hollows and hummocks, the maximum values being observed at an altitude near the average surface. In the Ust-Bakchar fen, water content was found to decrease from hollows to hummocks. In the Bakchar fen, 30 years after the fire peat accumulation occurred only on positive microrelief forms, where the 35 cm thick layer formed after the fire. Taking into account the microrelief heterogeneity, carbon accumulation over the post-fire period was estimated as 1.9 kg C/m2 or 60 g C/m2 per year. Peat accumulation seemed much slower in the Ust-Bakchar fen and was apparently absent on most of the surface. The average rate was estimated as 7 g C/m2 per year. Conclusions. The study found fen hollows to be most prone to burnout. The consequences of the fire manifest themselves in the drying of the upper layer of the peat deposit, thus preventing intensive overgrowth by sphagnum mosses 6–8 years after the fire. At the drained for forestry site in the Bakchar fen, 30 years after the fire the peat accumulation rate on moss hummocks was comparable to the rate in the unburned areas.

Factors regulating lignocellulolytic microbes, their degrading enzymes, and heterotrophic respiration in oil palm cultivated peatlands

Even though their role in mediating tropical peat decomposition and GHG emissions had been widely recognized, information concerning lignocellulolytic microbes, their degrading enzyme ability, and interconnection with soil physicochemical properties and peat heterotrophic respiration on mature oil palm plantation/OPP block level were rudimentary. This study evaluated the effect of sampling depth (0-30, 30-60, and 60-90 cm), OPP management zone (fertilization circle/FTC, frond stack/FRS, and harvesting path/HVP), and peat physicochemical properties on the lignocellulolytic bacteria and fungi, their degrading enzymes activities and peat heterotrophic respiration/Rh using principal component analysis/PCA, multiple linear regression/MLR, and generalized linear mixed effect models/GLMM. This study found that the soil microbiological and physicochemical properties varied widely. Dominant lignocellulolytic bacterial population and their cellulase enzyme activity were higher than fungi, regardless of sampling depth and management zone. PCA and GLMM analyses showed the significant importance of sampling depth and management zone in governing lignocellulolytic microbial population, their enzyme activities, and Rh. Microbial population and cellulase activity were also remarkably affected by the interaction of all studied factors. Peat chemical properties (pH and total Mn) controlled the natural variance of lignocellulolytic microbes and their enzymes, whereas total K regulate Rh. This study suggested that the research on microbiological-related GHG mitigation in OPP should be focused on managing the fungal population and cellulase enzyme activity at the peat surface (0-30 cm) and fertilization circle.

MEASUREMENT OF WATER RETENTION OF PEAT SOIL IN CANAL BLOCKING USING PRESSURE PLATE CHAMBER

Measuring air retention in constructed canal blockage is critical for determining changes in air content after canal blocking. The purpose of this study is to assess the influence of changes in levels on air retention values measured at three depths, namely 0-20 cm, 20-40 cm, and 40-60 cm, at four transect sampling stations created at a distance of 10 m to 260 m from the canal block. Changes in bulk density, porosity, and peat volume affect groundwater. Peat soil samples were collected from burned peatlands, and canal blocks were constructed. A pressure plate chamber was used to assess air retention. The findings of the investigation revealed that the air retention pattern of peat soil at 16 test sample locations was at maximum at PF 0.2 at each depth. At higher pressures (pF 2-4.2), peat groundwater is strongly bonded by peat soil particles. The average bulk density of peat is 0.2 2 and the porosity value is 86.79%. The higher the air content at each pF value has no influence on the porosity and bulk density values. Changes in air content between pF 2.0 and 4.2 lower average peat volume by 7.4%. The size of this value is assumed to be determined by the peat's type, maturity, and decomposition value

Redox potential is a robust indicator for decomposition processes in drained agricultural peat soils: A valuable tool in monitoring peatland wetting efforts

Peat decomposition driven by soil metabolic processes is responsible for approximately 2 % of global annual anthropogenic greenhouse gas emissions. A peat soil's redox potential (Eh) and pH reflect its biogeochemical state and are therefore linked to the rate of peat decomposition and greenhouse gas production. In this study, we aim to establish if continuous Eh measurements are an effective tool to monitor metabolic peat decomposition processes and thus to quantify the effects of peat wetting efforts. We applied continuous in-situ Eh measurements (>150 sensors 2020–2022) as a proxy for metabolic peat decomposition processes, which we validated under field conditions with extensive sampling of porewater chemistry (pH, NO3–, SO42−, Mn(II), Fe(II), S2− and CH4, >2000 samples) for five agricultural, drained, minerotrophic peatland sites in the Netherlands. These 5 sites consisted of plots with and without subsoil irrigation (SSI), where SSI aims to raise groundwater levels and thus wet the peat soil. We found that in-situ continuous Eh measurements closely reflected spatial and temporal heterogeneity in pore water chemistry. Therefore, we concluded that Eh is a robust proxy for peat decomposition processes. Building on this result, we used continuous Eh measurements to study the prevalence of specific metabolic processes from site-to-site in relation with groundwater level changes. We found that, while groundwater levels are an important driver for (an)aerobic conditions, groundwater levels do not explain the full dynamics and extent of (an)aerobic conditions. O2 intrusion was mostly limited to approximately 0.5 m depth at deep (>0.8 m) groundwater levels, likely due to air diffusion limitation. Higher and more constant groundwater levels year-round at SSI plots decreased oxygen intrusion and tended to deplete porewater Fe(II) and SO42−, which led to more reducing Eh and higher porewater CH4 concentrations. The depletion of electron acceptors and occurrence of methanogenesis differed from site to site. In summary, high-frequent Eh monitoring is found to be an effective tool to monitor metabolic peat decomposition processes and quantify the effects of peatlands wetting efforts. Therefore, this methodology is suitable to evaluate and further optimize peatland monitoring and preservation.