Sirvi Autor "Melling, Lulie" järgi

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Carbon dioxide dynamics across three stages of tropical peatland conversion to oil palm plantations
(2026) Kiew, Frankie; Hirata, Ryuichi; Hirano, Takashi; Wong, Guan Xhuan; Waili, Joseph Wenceslaus; Lo, Kim San; Soosaar, Kaido; Kasak, Kuno; Melling, Lulie; Mander, Ülo
This study represents the first long-term investigation spanning from a tropical peat swamp forest (PSF) to its conversion into an oil palm plantation (OPP), offering valuable data for assessing carbon dioxide (CO2) dynamics across different conversion stages. The conversion of tropical peat swamp forests to oil palm plantations has significant implications for CO2 dynamics. However, ecosystem-scale studies investigating CO2 dynamics across different stages of land conversion are lacking. This study used the eddy covariance (EC) technique to measure the net ecosystem exchange (NEE) of CO2 above a tropical peat swamp forest in Sarawak, Malaysia, from 2011 until it was cleared in 2017 and ultimately converted into an OPP in 2018. Our study found that the removal of forest biomass during land preparation led to a substantial increase in annual NEE from 25 ± 179 (2011 to 2016) to 2732 ± 655 g C m−2 year−1 (2017 to 2019). This increase was attributed to an 83 % reduction in gross primary productivity (GPP) and a 14 % reduction in ecosystem respiration (Reco). The near-ground environmental conditions also significantly changed across the conversion stages, inducing drier conditions compared to the forest. These changes were found to affect the controlling factors of nighttime NEE during conversion, resulting in a negative relationship with both air temperature and vapor pressure deficit above canopy, in contrast to the typical relationship with groundwater level observed before conversion. The conversion is also found to cause significant reduction in overall ecosystem photosynthetic activity as evidenced by the reduction in maximum gross photosynthetic rate (Pmax), photosynthetic photon flux density (PPFD), quantum yeild (α), and dark respiration (REd). Although ecosystem-scale assessments of CO2 dynamics provide insights into how ecosystems respond to changes in relation to land conversion, it is crucial to assess other respiration components, such as soil respiration and aboveground woody debris, for a more comprehensive analysis.
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Greenhouse gas emissions from ditches in oil palm plantations on tropical peatlands in Malaysia
(2025) Kasak, Kuno; Dronova, Iryna; Soosaar, Kaido; Melling, Lulie; Xhuan, Wong Guan; Sangok, Faustina; Ranniku, Reti; Villa, Jorge A.; Bansal, Sheel; Peacock, Michael; Mander, Ülo
Tropical peatlands, which store 20% of global peat carbon, are increasingly threatened by conversion to alternative land-uses such as oil palm plantations, pulp wood plantations, crop growth or other economic activities. This transformation involves peatland drainage, which lowers water tables, exposes peat to oxygen, and alters greenhouse gas (GHG) emissions: increasing carbon dioxide (CO2) and nitrous oxide (N2O) fluxes while reducing methane (CH4) emissions from soils. However, drainage ditches created in the process may become significant sources of CH4 due to anoxic conditions. This study quantified GHG fluxes from drainage ditches in Sarawak, Malaysia, through spatial sampling conducted during the daytime in the transitional period between the drier and wetter seasons using portable trace gas analyzers. Median fluxes were 0.19 g CH4 m−2 d−1, 17.1 g CO2 m−2 d−1, and − 0.12 mg N2O m−2 d−1. Physical water parameters such as pH, oxygen concentration, temperature, and oxidation–reduction potential were found to be significant drivers of GHG fluxes. The median emissions from ditches in one hectare of land were 5.84 kg CO2 ha−1 d−1, 2.78 kg CH4 as CO2 eq ha−1 d−1, and − 0.001 kg N2O as CO2 eq ha−1 d−1. These findings underscore the role of drainage ditches as CH4 sources in tropical peatland agriculture, highlighting the need for further research into GHG management in these modified landscapes.
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Greenhouse gas emissions from ditches in oil palm plantations on tropical peatlands in Malaysia
(2025) Kasak, Kuno; Dronova, Iryna; Soosaar, Kaido; Melling, Lulie; Xhuan, Wong Guan; Sangok, Faustina; Ranniku, Reti; Villa, Jorge A.; Bansal, Sheel; Peacock, Michael; Mander, Ülo
Tropical peatlands, which store 20% of global peat carbon, are increasingly threatened by conversion to alternative land-uses such as oil palm plantations, pulp wood plantations, crop growth or other economic activities. This transformation involves peatland drainage, which lowers water tables, exposes peat to oxygen, and alters greenhouse gas (GHG) emissions: increasing carbon dioxide (CO2) and nitrous oxide (N2O) fluxes while reducing methane (CH4) emissions from soils. However, drainage ditches created in the process may become significant sources of CH4 due to anoxic conditions. This study quantified GHG fluxes from drainage ditches in Sarawak, Malaysia, through spatial sampling conducted during the daytime in the transitional period between the drier and wetter seasons using portable trace gas analyzers. Median fluxes were 0.19 g CH4 m−2 d−1, 17.1 g CO2 m−2 d−1, and − 0.12 mg N2O m−2 d−1. Physical water parameters such as pH, oxygen concentration, temperature, and oxidation–reduction potential were found to be significant drivers of GHG fluxes. The median emissions from ditches in one hectare of land were 5.84 kg CO2 ha−1 d−1, 2.78 kg CH4 as CO2 eq ha−1 d−1, and − 0.001 kg N2O as CO2 eq ha−1 d−1. These findings underscore the role of drainage ditches as CH4 sources in tropical peatland agriculture, highlighting the need for further research into GHG management in these modified landscapes.
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Impact of land conversion on environmental conditions and methane emissions from a tropical peatland
(2025) Wong, Guan Xhuan; Hirata, Ryuichi; Hirano, Takashi; Kiew, Frankie; Waili, Joseph Wenceslaus; Mander, Ülo; Soosaar, Kaido; Melling, Lulie
Tropical peatlands are significant sources of methane (CH₄), but their contribution to the global CH₄ budget remains poorly quantified due to the lack of long-term, continuous and high-frequency flux measurements. To address this gap, we measured net ecosystem CH4 exchange (NEE-CH4) using eddy covariance technique throughout the conversion of a tropical peat swamp forest to an oil palm plantation. This encompassed the periods before, during and after conversion periods from 2014 to 2020, during which substantial environmental shifts were observed. Draining the peatland substantially lowered mean monthly groundwater levels from −20.0 ± 14.2 cm before conversion to −102.3 ± 31.6 cm during conversion and increased slightly to −96.5 ± 19.3 cm after conversion. Forest removal increased mean monthly soil temperature by 2.3 to 3.1 °C, reducing net radiation (Rn) and raising vapor pressure deficit (VPD). Following the tree removal, controlled burning temporarily warmed air temperature by 8 °C, increased VPD and significantly attenuated Rn, resulting in negative values owing to radiation interception by smoke and increased surface warming. Contrary to expectations that drainage would lower CH4 emissions, the site remained a consistent net source, with even higher emissions observed during and after conversion. The mean monthly NEE-CH4 during conversion (23.3 ± 8.6 mg C m−2 d−1) was about 2-times higher than before conversion (12.1 ± 5.3 mg C m−2 d−1) and about 1.5-times higher than after conversion (16.3 ± 4.1 mg C m−2 d−1). The heightened CH4 release is likely attributable to emissions from drainage ditches, underscoring their significant role in post-conversion CH4 dynamics. Despite its short duration, controlled burning substantially elevated NEE-CH4, ranging from 0.04 to 0.91 mg C m−2 s−1. Our findings highlight the substantial impact of land conversion on peatland CH4 dynamics, emphasizing the need for accurate flux measurements across various conversion stages to refine global CH4 budgets.
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Impact of land conversion on environmental conditions and methane emissions from a tropical peatland
(2025) Wong, Guan Xhuan; Hirata, Ryuichi; Hirano, Takashi; Kiew, Frankie; Waili, Joseph Wenceslaus; Mander, Ülo; Soosaar, Kaido; Melling, Lulie
Tropical peatlands are significant sources of methane (CH₄), but their contribution to the global CH₄ budget remains poorly quantified due to the lack of long-term, continuous and high-frequency flux measurements. To address this gap, we measured net ecosystem CH4 exchange (NEE-CH4) using eddy covariance technique throughout the conversion of a tropical peat swamp forest to an oil palm plantation. This encompassed the periods before, during and after conversion periods from 2014 to 2020, during which substantial environmental shifts were observed. Draining the peatland substantially lowered mean monthly groundwater levels from −20.0 ± 14.2 cm before conversion to −102.3 ± 31.6 cm during conversion and increased slightly to −96.5 ± 19.3 cm after conversion. Forest removal increased mean monthly soil temperature by 2.3 to 3.1 °C, reducing net radiation (Rn) and raising vapor pressure deficit (VPD). Following the tree removal, controlled burning temporarily warmed air temperature by 8 °C, increased VPD and significantly attenuated Rn, resulting in negative values owing to radiation interception by smoke and increased surface warming. Contrary to expectations that drainage would lower CH4 emissions, the site remained a consistent net source, with even higher emissions observed during and after conversion. The mean monthly NEE-CH4 during conversion (23.3 ± 8.6 mg C m−2 d−1) was about 2-times higher than before conversion (12.1 ± 5.3 mg C m−2 d−1) and about 1.5-times higher than after conversion (16.3 ± 4.1 mg C m−2 d−1). The heightened CH4 release is likely attributable to emissions from drainage ditches, underscoring their significant role in post-conversion CH4 dynamics. Despite its short duration, controlled burning substantially elevated NEE-CH4, ranging from 0.04 to 0.91 mg C m−2 s−1. Our findings highlight the substantial impact of land conversion on peatland CH4 dynamics, emphasizing the need for accurate flux measurements across various conversion stages to refine global CH4 budgets.
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Importance of N2O in greenhouse gas budgets of tropical peatlands
(Frontiers in Environmental Science, 2025) Pärn, Jaan; Espenberg, Mikk; Soosaar, Kaido; Kasak, Kuno; Thayamkottu, Sandeep; Schindler, Thomas; Ranniku, Reti; Sohar, Kristina; Mander, Ülo; Melling, Lulie; Malaverri, Lizardo Fachín
Tropical peatland ecosystems significantly influence Earth’s climate through their greenhouse gas exchange. Permanently wet peatlands take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage of peat releases carbon dioxide and nitrous oxide. Exchange of the greenhouse gases in relationship with tropical conditions are poorly understood. This is a global-scale field study of fluxes of three greenhouse gases – carbon dioxide, methane and nitrous oxide – and their environmental drivers across the full moisture range of tropical peatlands. We show that net emission of carbon dioxide dominates greenhouse gas budgets in drained tropical peatlands while nitrous oxide emission is the second most important contributor. Tropical peat swamp forests in their natural wet states are large greenhouse gas sinks and should be a global conservation and restoration priority.
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Importance of N2O in greenhouse gas budgets of tropical peatlands
(2025) Pärn, Jaan; Espenberg, Mikk; Soosaar, Kaido; Kasak, Kuno; Thayamkottu, Sandeep; Schindler, Thomas; Ranniku, Reti; Sohar, Kristina; Malaverri, Lizardo Fachín; Melling, Lulie; Mander, Ülo
Tropical peatland ecosystems significantly influence Earth’s climate through their greenhouse gas exchange. Permanently wet peatlands take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage of peat releases carbon dioxide and nitrous oxide. Exchange of the greenhouse gases in relationship with tropical conditions are poorly understood. This is a global-scale field study of fluxes of three greenhouse gases – carbon dioxide, methane and nitrous oxide – and their environmental drivers across the full moisture range of tropical peatlands. We show that net emission of carbon dioxide dominates greenhouse gas budgets in drained tropical peatlands while nitrous oxide emission is the second most important contributor. Tropical peat swamp forests in their natural wet states are large greenhouse gas sinks and should be a global conservation and restoration priority.
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Nitrous oxide as second most important greenhouse gas in tropical peatlands
(2024) Pärn, Jaan; Espenberg, Mikk; Soosaar, Kaido; Kasak, Kuno; Thayamkottu, Sandeep; Schindler, Thomas; Ranniku, Reti; Sohar, Kristina; Malaverri, Lizardo Fachín; Melling, Lulie; Mander, Ülo
Earth’s climate largely depends on carbon and nitrogen exchange between the atmosphere and tropical peatland ecosystems. Permanently wet peatlands take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage releases carbon dioxide from peat soils. Carbon and nitrous gas exchange and their relationships with tropical peatland conditions are poorly understood. We analysed natural peat swamp forests and fens, moderately drained and dry peatlands under a wide variety of land uses. The tropical peat swamp forests were large greenhouse gas sinks while tropical peatlands under moderate and low soil moisture levels emitted carbon dioxide and nitrous oxide. Carbon dioxide uptake of 160 mg m–2 h–1 dominated the net greenhouse gas budgets overall, while nitrous oxide emission of 90 mg CO2-equivalent m–2 h–1 on average was the second most important contributor (ahead of average methane emissions of 36 mg CO2-equivalent m–2 h–1) across the whole tropical peat moisture range.
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Peatland restoration pathways to mitigate greenhouse gas emissions and retain peat carbon
(2023) Mander, Ülo; Espenberg, Mikk; Melling, Lulie; Kull, Ain
Peatlands play a crucial role in the global carbon (C) cycle, making their restoration a key strategy for mitigating greenhouse gas (GHG) emissions and retaining C. This study analyses the most common restoration pathways employed in boreal and temperate peatlands, potentially applicable in tropical peat swamp forests. Our analysis focuses on the GHG emissions and C retention potential of the restoration measures. To assess the C stock change in restored (rewetted) peatlands and afforested peatlands with continuous drainage, we adopt a conceptual approach that considers short-term C capture (GHG exchange between the atmosphere and the peatland ecosystem) and long-term C sequestration in peat. The primary criterion of our conceptual model is the capacity of restoration measures to capture C and reduce GHG emissions. Our findings indicate that carbon dioxide (CO2) is the most influential part of long-term climate impact of restored peatlands, whereas moderate methane (CH4) emissions and low N2O fluxes are relatively unimportant. However, lateral losses of dissolved and particulate C in water can account up to a half of the total C stock change. Among the restored peatland types, Sphagnum paludiculture showed the highest CO2 capture, followed by shallow lakes and reed/grass paludiculture. Shallow lakeshore vegetation in restored peatlands can reduce CO2 emissions and sequester C but still emit CH4, particularly during the first 20 years after restoration. Our conceptual modelling approach reveals that over a 300-year period, under stable climate conditions, drained bog forests can lose up to 50% of initial C content. In managed (regularly harvested) and continuously drained peatland forests, C accumulation in biomass and litter input does not compensate C losses from peat. In contrast, rewetted unmanaged peatland forests are turning into a persistent C sink. The modelling results emphasized the importance of long-term C balance analysis which considers soil C accumulation, moving beyond the short-term C cycling between vegetation and the atmosphere.
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Peatland restoration pathways to mitigate greenhouse gas emissions and retain peat carbon
(2024) Mander, Ülo; Espenberg, Mikk; Melling, Lulie; Kull, Ain
Peatlands play a crucial role in the global carbon (C) cycle, making their restoration a key strategy for mitigating greenhouse gas (GHG) emissions and retaining C. This study analyses the most common restoration pathways employed in boreal and temperate peatlands, potentially applicable in tropical peat swamp forests. Our analysis focuses on the GHG emissions and C retention potential of the restoration measures. To assess the C stock change in restored (rewetted) peatlands and afforested peatlands with continuous drainage, we adopt a conceptual approach that considers short-term C capture (GHG exchange between the atmosphere and the peatland ecosystem) and long-term C sequestration in peat. The primary criterion of our conceptual model is the capacity of restoration measures to capture C and reduce GHG emissions. Our findings indicate that carbon dioxide (CO2) is the most influential part of long-term climate impact of restored peatlands, whereas moderate methane (CH4) emissions and low N2O fluxes are relatively unimportant. However, lateral losses of dissolved and particulate C in water can account up to a half of the total C stock change. Among the restored peatland types, Sphagnum paludiculture showed the highest CO2 capture, followed by shallow lakes and reed/grass paludiculture. Shallow lakeshore vegetation in restored peatlands can reduce CO2 emissions and sequester C but still emit CH4, particularly during the first 20 years after restoration. Our conceptual modelling approach reveals that over a 300-year period, under stable climate conditions, drained bog forests can lose up to 50% of initial C content. In managed (regularly harvested) and continuously drained peatland forests, C accumulation in biomass and litter input does not compensate C losses from peat. In contrast, rewetted unmanaged peatland forests are turning into a persistent C sink. The modelling results emphasized the importance of long-term C balance analysis which considers soil C accumulation, moving beyond the short-term C cycling between vegetation and the atmosphere.
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Temporal dynamics of soil microbial C and N cycles with GHG fluxes in the transition from tropical peatland forest to oil palm plantation
(Environmental Microbiology, 2024) Midot, Frazer; Goh, Kian Mau; Liew, Kok Jun; Lau, Sharon Yu Ling; Espenberg, Mikk; Mander, Ülo; Melling, Lulie
Tropical peatlands significantly significantly significantly influence influence local and global carbon and nitrogen cycles, yet they face growing pressure from anthropogenic activities. Land use changes, such as peatland forests conversion to oil palm plantations, affect affect the soil microbiome and greenhouse gas (GHG) emissions. However, the temporal dynamics of microbial community changes and their role as GHG indicators are not well understood. This study examines the dynamics of peat chemistry, soil microbial communities, and GHG emissions from 2016 to 2020 in a logged-over secondary peat swamp forest in Sarawak, Malaysia, which transitioned to an oil palm plantation. This study focuses on changes in genetic composition governing plant litter degradation, methane (CH4), and nitrous oxide (N2O) fluxes. fluxes. fluxes. Soil CO2 emission increased (doubling from approximately 200 mg C m−2 h−1), while CH4 emissions decreased (from 200 μg C m−2 h−1 to slightly negative) following land use changes. The N2O emissions in the oil palm plantation reached approximately 1,510 μg N m−2 h−1, significantly significantly significantly higher than previous land uses. The CH4 fluxes fluxes were driven by groundwater table, humification levels, and C:N ratio, with Methanomicrobia populations dominating methanogenesis and Methylocystis as the main CH4 oxidizer. The N2O fluxes fluxes correlated with groundwater table, total nitrogen, and C:N ratio with dominant nirK-type denitrifiers denitrifiers (13-fold nir to nosZ) and a minor role by nitrification nitrification (a threefold increase in amoA) in the plantation. Proteobacteria and Acidobacteria encoding incomplete denitrification denitrification genes potentially impact N2O emissions. These findings highlighted complex interactions between microbial communities and environmental factors influencing GHG fluxes fluxes in altered tropical peatland ecosystems.
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Temporal dynamics of soil microbial C and N cycles with GHG fluxes in the transition from tropical peatland forest to oil palm plantation
(2025) Midot, Frazer; Goh, Kian Mau; Liew, Kok Jun; Lau, Sharon Yu Ling; Espenberg, Mikk; Mander, Ülo; Melling, Lulie
Tropical peatlands significantly influence local and global carbon and nitrogen cycles, yet they face growing pressure from anthropogenic activities. Land use changes, such as peatland forests conversion to oil palm plantations, affect the soil microbiome and greenhouse gas (GHG) emissions. However, the temporal dynamics of microbial community changes and their role as GHG indicators are not well understood. This study examines the dynamics of peat chemistry, soil microbial communities, and GHG emissions from 2016 to 2020 in a logged-over secondary peat swamp forest in Sarawak, Malaysia, which transitioned to an oil palm plantation. This study focuses on changes in genetic composition governing plant litter degradation, methane (CH4), and nitrous oxide (N2O) fluxes. Soil CO2 emission increased (doubling from approximately 200 mg C m−2 h−1), while CH4 emissions decreased (from 200 µg C m−2 h−1 to slightly negative) following land use changes. The N2O emissions in the oil palm plantation reached approximately 1,510 µg N m−2 h−1, significantly higher than previous land uses. The CH4 fluxes were driven by groundwater table, humification levels, and C:N ratio, with Methanomicrobia populations dominating methanogenesis and Methylocystis as the main CH4 oxidizer. The N2O fluxes correlated with groundwater table, total nitrogen, and C:N ratio with dominant nirK-type denitrifiers (13-fold nir to nosZ) and a minor role by nitrification (a threefold increase in amoA) in the plantation. Proteobacteria and Acidobacteria encoding incomplete denitrification genes potentially impact N2O emissions. These findings highlighted complex interactions between microbial communities and environmental factors influencing GHG fluxes in altered tropical peatland ecosystems.