Sirvi Autor "Mander, Ülo" järgi

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15N tracers and microbial analyses reveal in situ N2O sources in contrasting water regimes of a drained peatland forest
(2024) Masta, Mohit; Espenberg, Mikk; Kuusemets, Laura; Pärn, Jaan; Thayamkottu, Sandeep; Sepp, Holar; Kirsimäe, Kalle; Sgouridis, Fotis; Kasak, Kuno; Soosaar, Kaido; Mander, Ülo
Managed peatlands are a significant source of nitrous oxide (N2O), a powerful greenhouse gas and stratospheric ozone depleter. Due to the complexity and diversity of microbial N2O processes, different methods such as tracer, isotopomer, and microbiological technologies are required to understand these processes. The combined application of different methods helps to precisely estimate these processes, which is crucial for the future management of drained peatlands, and to mitigate soil degradation and negative atmospheric impact. In this study, we investigated N2O sources by combining tracer, isotopomer, and microbial analysis in a drained peatland forest under flooded and drained treatments. On average, the nitrification genes showed higher abundances in the drained treatment, and the denitrification genes showed higher abundances in the flooded treatment. This is consistent with the underlying chemistry, as nitrification requires oxygen while denitrification is anaerobic. We observed significant differences in labelled N2O fluxes between the drained and flooded treatments. The emissions of N2O from the flooded treatment were nearly negligible, whereas the N2O evolved from the nitrogen-15 (15N)-labelled ammonium (15NH4+) in the drained treatment peaked at 147 μg 15N m-2 h-1. This initially suggested nitrification as the driving mechanism behind N2O fluxes in drained peatlands, but based on the genetic data, isotopic analysis, and N2O mass enrichment, we conclude that hybrid N2O formation involving ammonia oxidation was the main source of N2O emissions in the drained treatment. Based on the 15N-labelled nitrate (15NO3-) tracer addition and gene copy numbers, the low N2O emissions in the flooded treatment came possibly from complete denitrification producing inert dinitrogen. At atomic level, we observed selective enrichment of mass 45 of N2O molecule under 15NH4+ amendment in the drained treatment and enrichment of both masses 45 and 46 under 15NO3- amendment in the flooded treatment. The selective enrichment of mass 45 in the drained treatment indicated the presence of hybrid N2O formation, which was also supported by the high abundances of archaeal genes.
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A comprehensive porewater survey of European peatlands reveals sustained elevated phosphorus levels after 10–20 years of rewetting
(2025) Krishnankutty, Nimisha; Gelbrecht, Jörg; Petersen, Rasmus Jes; Rayner, Dylan; Lau, Maximilian P.; Frank, Stefan; Andersen, Roxane; Pärn, Jaan; Mander, Ülo; Hoffmann, Carl C.; Mäenpää, Maarit I.; Goldhammer, Tobias; Kull, Ain; Florea, Adrian-Florin; Zak, Dominik
Rewetting drained peatlands can lead to high nutrient mobilization, increased methane emissions, and a slow re-establishment of peat-forming vegetation. To guide effective restoration and management, understanding the temporal and spatial variability in porewater chemistry is essential. This study surveyed 64 natural and rewetted peatlands across Germany, Poland, Estonia, Sweden, Georgia, and Scotland from 1997 to 2017. A total of 812 anoxic porewater samples were collected using dialysis samplers (0–0.6 m depth). The rewetted fens exhibited a wide range of dissolved substances, spanning orders of magnitude for soluble reactive phosphorus (SRP: 0.1–18.9 mg L−1), ammonium (NH4+-N: 0.1–117.3 mg L−1), and dissolved organic carbon (DOC: 13–313 mg L−1). However, the mean concentrations were significantly higher than those observed in natural fens (p < 0.05). Depth-integrated mobilization rates for nutrients in rewetted fens were, on average, 23 times higher for SRP (1.8 mg P m−2 d-1) and 4.6 times higher for NH4+-N (3.6 mg N m−2 d-1) compared to their natural counterparts (0.1 mg P m−2 d-1 and 0.8 mg N m−2 d-1). Seasonal variation was also evident in rewetted fens densely colonized by helophytes, with SRP concentrations being lower in the growing season. Notably, SRP concentrations remained elevated 10–20 years after rewetting; however, a 50–80 % decrease was observed at sites characterized by comparatively low iron content in the peat (< 20 mg g−1 dry mass). Further investigations should explore how nutrient dynamics evolve over extended rewetting periods in different contexts, including climate change.
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A comprehensive porewater survey of European peatlands reveals sustained elevated phosphorus levels after 10–20 years of rewetting
(2025) Krishnankutty,; Gelbrecht, Jörg; Petersen, Rasmus Jes; Rayner, Dylan; Lau, Maximilian P.; Frank, Stefan; Andersen, Roxane; Pärn, Jaan; Mander, Ülo; Kotowski, Wiktor; Liu, Haojie; Iversen, Bo V.; Heckrath, Goswin; Hansen, Hans C.B.; Hoffmann, Carl C.; Mäenpää, Maarit I.; Goldhammer, Tobias; Kull, Ain; Florea, Adrian-Florin; Zak, Dominik
Rewetting drained peatlands can lead to high nutrient mobilization, increased methane emissions, and a slow re-establishment of peat-forming vegetation. To guide effective restoration and management, understanding the temporal and spatial variability in porewater chemistry is essential. This study surveyed 64 natural and rewetted peatlands across Germany, Poland, Estonia, Sweden, Georgia, and Scotland from 1997 to 2017. A total of 812 anoxic porewater samples were collected using dialysis samplers (0–0.6 m depth). The rewetted fens exhibited a wide range of dissolved substances, spanning orders of magnitude for soluble reactive phosphorus (SRP: 0.1–18.9 mg L−1), ammonium (NH4+-N: 0.1–117.3 mg L−1), and dissolved organic carbon (DOC: 13–313 mg L−1). However, the mean concentrations were significantly higher than those observed in natural fens (p < 0.05). Depth-integrated mobilization rates for nutrients in rewetted fens were, on average, 23 times higher for SRP (1.8 mg P m−2 d-1) and 4.6 times higher for NH4+-N (3.6 mg N m−2 d-1) compared to their natural counterparts (0.1 mg P m−2 d-1 and 0.8 mg N m−2 d-1). Seasonal variation was also evident in rewetted fens densely colonized by helophytes, with SRP concentrations being lower in the growing season. Notably, SRP concentrations remained elevated 10–20 years after rewetting; however, a 50–80 % decrease was observed at sites characterized by comparatively low iron content in the peat (< 20 mg g−1 dry mass). Further investigations should explore how nutrient dynamics evolve over extended rewetting periods in different contexts, including climate change.
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Amazonase madaliku palmisoomuldade mikrobioloogiline lämmastikuringe ning selle seos dilämmastikoksiidi voogudega
(Tartu Ülikool, 2022) Hints, Liina; Espenberg, Mikk; Mander, Ülo; Tartu Ülikool. Geograafia osakond; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
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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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Distinct microbial communities drive methane cycling in below- and above-ground compartments of tropical cloud forests growing on peat
(2025) Kazmi, Fahad Ali; Mander, Ülo; Khanongnuch, Ramita; Öpik, Maarja; Ranniku, Reti; Soosaar, Kaido; Masta, Mohit; Tenhovirta, Salla A. M.; Kasak, Kuno; Ah-Peng, Claudine; Espenberg, Mikk
Cloud forests are unique yet understudied ecosystems regarding CH4 exchange despite their significance in carbon storage. We investigated CH4 fluxes in peat soil and tree stems of two tropical cloud forests on Réunion Island, one featuring Erica reunionensis and the second a mix of E. reunionensis and Alsophila glaucifolia. The study examined microbiomes across below-ground (soil) and above-ground (canopy soil, leaves, and stems) forest compartments. Metagenomics and qPCR analyses targeted key genes in methanogenesis and methanotrophy in soil and above-ground samples, alongside soil physicochemical measurements. CH4 fluxes from peat soil and tree stems were measured using gas chromatography and portable trace gas analyzers. Peat soil in both forests acted as a CH4 sink (− 23.8 ± 4.84 µg C m− 2 h− 1) and CO2 source (55.5 ± 5.51 µg C m− 2 h− 1), with higher CH4 uptake in sites dominated by endemic tree species E. reunionensis. In forest soils, a high abundance of n-DAMO 16 S rRNA gene (3.42 × 107 ± 7 × 106 copies/g dw) was associated with nitrate levels and higher rates of CH4 uptake and CO2 emissions. NC-10 bacteria (0.1–0.3%) were detected in only the Erica forest soil, verrucomicrobial methanotrophs (0.1–3.1%) only in the mixed forest soil, whereas alphaproteobacterial methanotrophs (0.1–3.3%) were present in all soils. Tree stems in both forests were weak sinks of CH4 (-0.94 ± 0.4 µg C m− 2 h− 1). The canopy soil hosted verrucomicrobial methanotrophs (0.1–0.3%). The leaves in both forests exhibited metabolic potential for CH4 production, e.g., exhibiting high mcrA copy numbers (3.5 × 105 ± 2.3 × 105 copies/g dw). However, no CH4-cycling functional genes were detected in the stem core samples. Tropical cloud forest peat soils showed high anaerobic methanotrophy via the n-DAMO process, while aerobic methanotrophs were abundant in canopy soils. Leaves hosted methanotrophs but predominantly methanogens. These results highlight the significant differences between canopy and soil microbiomes in the CH4 cycle, emphasizing the importance of above-ground microbiomes in forest CH4 gas budgets.
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Distinct microbial communities drive methane cycling in below- and above-ground compartments of tropical cloud forests growing on peat
(2025) Kazmi, Fahad Ali; Mander, Ülo; Khanongnuch, Ramita; Öpik, Maarja; Ranniku, Reti; Soosaar, Kaido; Masta, Mohit; Tenhovirta, Salla A. M.; Kasak, Kuno; Ah-Peng, Claudine; Espenberg, Mikk
Cloud forests are unique yet understudied ecosystems regarding CH4 exchange despite their significance in carbon storage. We investigated CH4 fluxes in peat soil and tree stems of two tropical cloud forests on Réunion Island, one featuring Erica reunionensis and the second a mix of E. reunionensis and Alsophila glaucifolia. The study examined microbiomes across below-ground (soil) and above-ground (canopy soil, leaves, and stems) forest compartments. Metagenomics and qPCR analyses targeted key genes in methanogenesis and methanotrophy in soil and above-ground samples, alongside soil physicochemical measurements. CH4 fluxes from peat soil and tree stems were measured using gas chromatography and portable trace gas analyzers. Peat soil in both forests acted as a CH4 sink (− 23.8 ± 4.84 µg C m− 2 h− 1) and CO2 source (55.5 ± 5.51 µg C m− 2 h− 1), with higher CH4 uptake in sites dominated by endemic tree species E. reunionensis. In forest soils, a high abundance of n-DAMO 16 S rRNA gene (3.42 × 107 ± 7 × 106 copies/g dw) was associated with nitrate levels and higher rates of CH4 uptake and CO2 emissions. NC-10 bacteria (0.1–0.3%) were detected in only the Erica forest soil, verrucomicrobial methanotrophs (0.1–3.1%) only in the mixed forest soil, whereas alphaproteobacterial methanotrophs (0.1–3.3%) were present in all soils. Tree stems in both forests were weak sinks of CH4 (-0.94 ± 0.4 µg C m− 2 h− 1). The canopy soil hosted verrucomicrobial methanotrophs (0.1–0.3%). The leaves in both forests exhibited metabolic potential for CH4 production, e.g., exhibiting high mcrA copy numbers (3.5 × 105 ± 2.3 × 105 copies/g dw). However, no CH4-cycling functional genes were detected in the stem core samples. Tropical cloud forest peat soils showed high anaerobic methanotrophy via the n-DAMO process, while aerobic methanotrophs were abundant in canopy soils. Leaves hosted methanotrophs but predominantly methanogens. These results highlight the significant differences between canopy and soil microbiomes in the CH4 cycle, emphasizing the importance of above-ground microbiomes in forest CH4 gas budgets.
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Dry and wet periods determine stem and soil greenhouse gas fluxes in a northern drained peatland forest
(2024) Ranniku, Reti; Mander, Ülo; Escuer-Gatius, Jordi; Schindler, Thomas; Kupper, Priit; Sellin, Arne; Soosaar, Kaido
Greenhouse gas (GHG) fluxes from peatland soils are relatively well studied, whereas tree stem fluxes have received far less attention. Simultaneous year-long measurements of soil and tree stem GHG fluxes in northern peatland forests are scarce, as previous studies have primarily focused on the growing season. We determined the seasonal dynamics of tree stem and soil CH4, N2O and CO2 fluxes in a hemiboreal drained peatland forest. Gas samples for flux calculations were manually collected from chambers at different heights on Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) trees (November 2020–December 2021) and analysed using gas chromatography. Environmental parameters were measured simultaneously with fluxes and xylem sap flow was recorded during the growing season. Birch stems played a greater role in the annual GHG dynamics than spruce stems. Birch stems were net annual CH4, N2O and CO2 sources, while spruce stems constituted a CH4 and CO2 source but a N2O sink. Soil was a net CO2 and N2O source, but a sink of CH4. Temporal dynamics of stem CH4 and N2O fluxes were driven by isolated emissions' peaks that contributed significantly to net annual fluxes. Stem CO2 efflux followed a seasonal trend coinciding with tree growth phenology. Stem CH4 dynamics were significantly affected by the changes between wetter and drier periods, while N2O was more influenced by short-term changes in soil hydrologic conditions. We showed that CH4 emitted from tree stems during the wetter period can offset nearly half of the soil sink capacity. We presented for the first time the relationship between tree stem GHG fluxes and sap flow in a peatland forest. The net CH4 flux was likely an aggregate of soil-derived and stem-produced CH4. A dominating soil source was more evident for stem N2O fluxes.
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Dry and wet periods determine stem and soil greenhouse gas fluxes in a northern drained peatland forest
(Science of The Total Environment, 2024) Ranniku, Reti; Mander, Ülo; Escuer-Gatius, Jordi; Schindler, Thomas; Kupper, Priit; Sellin, Arne; Soosaar, Kaido
Greenhouse gas (GHG) fluxes from peatland soils are relatively well studied, whereas tree stem fluxes have received far less attention. Simultaneous year-long measurements of soil and tree stem GHG fluxes in northern peatland forests are scarce, as previous studies have primarily focused on the growing season. We determined the seasonal dynamics of tree stem and soil CH4, N2O and CO2 fluxes in a hemiboreal drained peatland forest. Gas samples for flux calculations were manually collected from chambers at different heights on Downy Birch (Betula pubescens) and Norway Spruce (Picea abies) trees (November 2020–December 2021) and analysed using gas chromatography. Environmental parameters were measured simultaneously with fluxes and xylem sap flow was recorded during the growing season. Birch stems played a greater role in the annual GHG dynamics than spruce stems. Birch stems were net annual CH4, N2O and CO2 sources, while spruce stems constituted a CH4 and CO2 source but a N2O sink. Soil was a net CO2 and N2O source, but a sink of CH4. Temporal dynamics of stem CH4 and N2O fluxes were driven by isolated emissions' peaks that contributed significantly to net annual fluxes. Stem CO2 efflux followed a seasonal trend coinciding with tree growth phenology. Stem CH4 dynamics were significantly affected by the changes between wetter and drier periods, while N2O was more influenced by short-term changes in soil hydrologic conditions. We showed that CH4 emitted from tree stems during the wetter period can offset nearly half of the soil sink capacity. We presented for the first time the relationship between tree stem GHG fluxes and sap flow in a peatland forest. The net CH4 flux was likely an aggregate of soil-derived and stem-produced CH4. A dominating soil source was more evident for stem N2O fluxes.
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Dual controls of vapour pressure deficit and soil moisture on photosynthesis in a restored temperate bog
(Science of The Total Environment, 2025) Thayamkottu, Sandeep; Masta, Mohit; Skeeter, June; Pärn, Jaan; Knox, Sara H.; Smallman, T. Luke; Mander, Ülo
Despite only covering ~3 % of the land mass, peatlands store more carbon (C) per unit area than any other ecosystem. This is due to the discrepancy between C fixed by the plants (Gross primary productivity (GPP)) and decomposition. However, this C is vulnerable to frequent, severe droughts and changes in the peatland microclimate. Plants play a vital role in ecosystem C dynamics under drought by mediating water loss to the atmosphere (surface water vapour conductance) and GPP by the presence/absence of stomatal regulation. This is dependent on soil moisture, air temperature, and vapour pressure deficit (VPD). Although there is ample evidence of the role of VPD on stomatal regulation and GPP, the impact of soil moisture is still debated. We addressed this knowledge gap by investigating the role of bulk surface conductance of water vapour in shifts between climatic (Air temperature (Tair), incoming shortwave radiation (SWR) and VPD) and water limitation of GPP in a peat bog in Canada. A causal analysis process was used to investigate how environmental factors influenced GPP. The results suggested that stomatal regulation in response to increased VPD caused the reduction in GPP in 2016 (~2.5 gC m−2 day−1 as opposed to ~3 gC m−2 day−1 in 2018). In contrast, GPP was limited again in 2019 due to the dry surface. This was driven by the relaxed stomatal regulation adopted by the ecosystem following the initial drought to maximise C assimilation. We found the threshold at which surface water decline limited GPP was at about −8 cm water table depth (82.5 % soil moisture). The causal inference corroborated our findings. The temporal variations of water and energy limitation seen in this study could increasingly restrict GPP due to the projected climate warming.
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Dual controls of vapour pressure deficit and soil moisture on photosynthesis in a restored temperate bog
(2025) Thayamkottu, Sandeep; Masta, Mohit; Skeeter, June; Pärn, Jaan; Knox, Sara H.; Smallman, T. Luke; Mander, Ülo
Despite only covering ~3 % of the land mass, peatlands store more carbon (C) per unit area than any other ecosystem. This is due to the discrepancy between C fixed by the plants (Gross primary productivity (GPP)) and decomposition. However, this C is vulnerable to frequent, severe droughts and changes in the peatland microclimate. Plants play a vital role in ecosystem C dynamics under drought by mediating water loss to the atmosphere (surface water vapour conductance) and GPP by the presence/absence of stomatal regulation. This is dependent on soil moisture, air temperature, and vapour pressure deficit (VPD). Although there is ample evidence of the role of VPD on stomatal regulation and GPP, the impact of soil moisture is still debated. We addressed this knowledge gap by investigating the role of bulk surface conductance of water vapour in shifts between climatic (Air temperature (Tair), incoming shortwave radiation (SWR) and VPD) and water limitation of GPP in a peat bog in Canada. A causal analysis process was used to investigate how environmental factors influenced GPP. The results suggested that stomatal regulation in response to increased VPD caused the reduction in GPP in 2016 (~2.5 gC m−2 day−1 as opposed to ~3 gC m−2 day−1 in 2018). In contrast, GPP was limited again in 2019 due to the dry surface. This was driven by the relaxed stomatal regulation adopted by the ecosystem following the initial drought to maximise C assimilation. We found the threshold at which surface water decline limited GPP was at about −8 cm water table depth (82.5 % soil moisture). The causal inference corroborated our findings. The temporal variations of water and energy limitation seen in this study could increasingly restrict GPP due to the projected climate warming.
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Dynamics of soil microbial nitrogen cycle during a year-long study in a drained peatland forest
(Tartu Ülikool, 2022) Ferch, Zane Walden; Espenberg, Mikk; Mander, Ülo; Tartu Ülikool. Geograafia osakond; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
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Effects of Water Table Fluctuation on Greenhouse Gas Emissions from Wetland Soils in the Peruvian Amazon
(2023) Pärn, Jaan; Soosaar, Kaido; Schindler, Thomas; Machacova, Katerina; Muñoz, Waldemar Alegría; Fachín, Lizardo; Aspajo, José Luis Jibaja; Negron-Juarez, Robinson I.; Maddison, Martin; Rengifo, Jhon; Dinis, Danika Journeth Garay; Oversluijs, Adriana Gabriela Arista; Fucos, Manuel Calixto Ávila; Vásquez, Rafael Chávez; Wampuch, Ronald Huaje; García, Edgar Peas; Sohar, Kristina; Horna, Segundo Cordova; Gómez, Tedi Pacheco; Muñoz, Jose David Urquiza; Espinoza, Rodil Tello; Mander, Ülo
Amazonian swamp forests remove large amounts of carbon dioxide (CO2) but produce methane (CH4). Both are important greenhouse gases (GHG). Drought and cultivation cut the CH4 emissions but may release CO2. Varying oxygen content in nitrogen-rich soil produces nitrous oxide (N2O), which is the third most important GHG. Despite the potentially tremendous changes, GHG emissions from wetland soils under different land uses and environmental conditions have rarely been compared in the Amazon. We measured environmental characteristics, and CO2, CH4 and N2O emissions from the soil surface with manual opaque chambers in three sites near Iquitos, Peru from September 2019 to March 2020: a pristine peat swamp forest, a young forest and a slash-and-burn manioc field. The manioc field showed moderate soil respiration and N2O emission. The peat swamp forests under slight water table drawdown emitted large amounts of CO2 and CH4. A heavy post-drought shower created a hot moment of N2O in the pristine swamp forest, likely produced by nitrifiers. All in all, even small changes in soil moisture can create hot moments of GHG emissions from Amazonian wetland soils, and should therefore be carefully monitored.
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Effects of Water Table Fluctuation on Greenhouse Gas Emissions from Wetland Soils in the Peruvian Amazon
(2021) Pärn, Jaan; Soosaar, Kaido; Schindler, Thomas; Machacova, Katerina; Muñoz, Waldemar Alegría; Fachín, Lizardo; Aspajo, José Luis Jibaja; Negron‑Juarez, Robinson I.; Maddison, Martin; Rengifo, Jhon; Dinis, Danika Journeth Garay; Oversluijs, Adriana Gabriela Arista; Fucos, Manuel Calixto Ávila; Vásquez, Rafael Chávez; Wampuch, Ronald Huaje; García, Edgar Peas; Sohar, Kristina; Horna, Segundo Cordova; Gómez, Tedi Pacheco; Muñoz, Jose David Urquiza; Espinoza, Rodil Tello; Mander, Ülo
Amazonian swamp forests remove large amounts of carbon dioxide (CO2) but produce methane (CH4). Both are important greenhouse gases (GHG). Drought and cultivation cut the CH4 emissions but may release CO2. Varying oxygen content in nitrogen-rich soil produces nitrous oxide (N2O), which is the third most important GHG. Despite the potentially tremendous changes, GHG emissions from wetland soils under different land uses and environmental conditions have rarely been compared in the Amazon. We measured environmental characteristics, and CO2, CH4 and N2O emissions from the soil surface with manual opaque chambers in three sites near Iquitos, Peru from September 2019 to March 2020: a pristine peat swamp forest, a young forest and a slash-and-burn manioc field. The manioc field showed moderate soil respiration and N2O emission. The peat swamp forests under slight water table drawdown emitted large amounts of CO2 and CH4. A heavy post-drought shower created a hot moment of N2O in the pristine swamp forest, likely produced by nitrifiers. All in all, even small changes in soil moisture can create hot moments of GHG emissions from Amazonian wetland soils, and should therefore be carefully monitored.
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Erinevate taimeliikide mõju mikrobioloogilisele metaani- ja lämmastikuringele ning CH4 ja N2O emissioonidele riimveest mõjutatud rannikul
(Tartu Ülikool, 2020) Pille, Kristin; Espenberg, Mikk; Mander, Ülo; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
Rannikualad on mitmekesised ökosüsteemid, mis kujunevad mitmete tegurite koosmõjul. Oma mitmekesisuse ning varieeruvusega pakuvad nad mitmeid elutähtsaid ökosüsteemi teenuseid. Tänapäeva üha intensiivistuv inimtegevus ning kliimamuutustega kaasnevad häiringud on suurendanud mõjusid rannikualadele. Erinevad taimed mõjutavad rannikumulla mikroobikooslusi, mõjutades sealseid mikrobioloogilisi metaani- ja lämmastikuringet. Mikrobioloogiliste aineringe häiringute tagajärjel võib aga keskkonda emiteerida kahjulikke kasvuhoonegaase, nagu metaani CH4 ning dilämmastikoksiidi N2O. Käesoleva magistritöö eesmärgiks oli uurida erinevaid riimveelisi rannikualasid Lääne-Eestis ja Ida-Hiinas ning seal kasvavate taimeliikide mõju mikrobioloogilisele metaani- ja lämmastikuringele. Erinevate metaani- ja lämmastikuringe protsesside toimumise potentsiaali määrati protsessile spetsiifiliste markergeenidega. Metaaniringes osalevaid mikroorganisme tuvastati järgmiseid geene kvantifitseerides: metaani tootvaid metanogeenid (mcrA) ning metaani tarbijaid metanotroofid (pmoA). Lämmastikuringes uuriti järgnevaid protsesse: lämmastiku fikseerimine (nifH), nitrifikatsioon (bakterite ja arhede amoA), denitrifikatsioon (nirS, nirK, nosZI, nosZII), dissimilatoorne nitraadi redutseerimine ammooniumiks (nrfA), anaeroobne ammooniumi oksüdatsioon (ANAMMOX spetsiifiline 16S rRNA geen) ning täielik ammooniumi oksüdeerimine (COMAMMOX spetsiifiline 16S rRNA geen). Lisaks uuriti lämmastiku- ja süsinikuringet ühendavat nitritist sõltuvat anaeroobset metaani oksüdeerimist (n-damo spetsiifiline 16S rRNA geen). Neist nelja protsessi vaheetappides – nitrifikatsioon (k.a COMAMMOX), denitrifikatsioon, DNRA ja nitrifitseerijate denitrifikatsioon, käigus võib eralduda keskkonda kahjulikku kasvuhoonegaasi N2O-d. Keskkonnategurite mõju rannikukoosluste mikroorganismidele hinnati metaani ja naerugaasi emissioonide kontsentratsioone mõõtes kambermeetodil ning nende olulisi seoseid geeni- ning keskkonnaparameetrite vahel erinevate statistiliste meetoditega (Spearmani korrelatsioonikoefitsent, ANOVA). Antud magistritöö tulemustest järeldus, et taimed mängivad olulist rolli kasvukeskkonna kujundamises ning seeläbi kahjulike kasvuhoonegaaside heitkoguste emiteerimises. Erinevad keskkonnatingimused määrasid uurimisalade koosluse struktuuri. Keskkonnatingimused soodustasid COMAMMOX-i protsessi läbiviivate mikroorganismide aktiivsust Spartina ja Scirpuse ning kare-kaislaga katsealal, kus mikroorganismide kohastumuste eelistuste kohta rannikusetetes teatakse vähe. ANAMMOX-i suurim 43 geneetiline potentsiaal Hiina katsealadel näitas, et üleliigne lämmastik redutseeriti nii, et minimaalselt eraldus kahjulikku dilämmastikoksiidi. Hiina uurimisala keskkonnatingimused soodustasid nitrifikatsiooni toimumist, seevastu Eestis emiteerus kahjulik N2O-d peamiselt mittetäieliku denitrifikatsiooni tulemina. Uurimisalad erinesid üksteisest peamiselt üldsüsiniku protsentuaalsuse ja anaeroobsete tingimuste poolest, mis pakkus soodsat elukeskkonda just nirK geeni omavatele mikroorganismidele. Suurimad emissioonide kontsentratsioone näidati vanema Spartina alterniflora´ga kaetud alal, kus metaani eraldus võrreldes Eesti alaga märkimisväärselt ligi neli korda rohkem. Eestis täheldati suuremaid metaanikoguseid lagedalt alalt, kus dilämmastikoksiidi emiteerus rohkem hariliku pillirooga (Phragmites australis) katsealalt. Metaani tarbivate mikroorganismide aktiivsus oli seotud metaani suuremate emissioonidega. Dilämmastikoksiidi korral täheldati oluline seos taimeliigi vanuse ning biomassiga, kus nooremad taimed leevendasid kasvuhoonegaasi emiteerumist atmosfääri. Seevastu taimede puhkeperioodil tuvastati tihe konkurents protsesside läbiviimiseks vajalike substraatide vahel mikroorganismidega, mille tõttu vähenesid kasvuhoonegaasi kogused. Lämmastiku- ja süsinikuringet ühendava n-damo suurimat geneetilist potentsiaal leiti pillirooga ja lagedalt mudaselt alalt, kus eelnimetatud protsess leevendas metaanikoguste paiskamist atmosfääri. Parema kaitse tagamiseks on oluline mõista rannikualades toimuvaid protsesse ning nende seoseid erinevate keskkonnaparameetritega. Taimede potentsiaali vahendada emissioonide vooge ning risosfääris toimuv suhe väärib tähelepanu, sest see võib muuta meie arusaama, kuidas taimed reageerivad lämmastikuühendite kasvule, soolsusele, merevee tõusu või muudele kliimamuutusest intensiivistuvatele teguritele. Uued teadmised ning varasemate teadmiste kinnitused aitavad mõista, kuidas toimub keerukas ranniku ökosüsteem mikroorganismide vaatevinklist ning kuidas seda on võimalik mõjutada taimedega.
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Global peatland greenhouse gas dynamics: state of the art, processes, and perspectives
(New Phytologist, 2025) Mander, Ülo; Öpik, Maarja; Espenberg, Mikk
Natural peatlands regulate greenhouse gas (GHG) fluxes through a permanently high groundwater table, causing carbon dioxide (CO2) assimilation but methane (CH4) emissions due to anaerobic conditions. By contrast, drained and disturbed peatlands are hotspots for CO2 and nitrous oxide (N2O) emissions, while CH4 release is low but high from drainage ditches. Generally, in low-latitude (tropical and subtropical) peatlands, emissions of all GHGs are higher than in high-latitude (temperate, boreal, and Arctic) peatlands. Their inherent dependence on the water regime makes peatlands highly vulnerable to both direct and indirect anthropogenic impacts, including climate change-induced drying, which is creating anthro-natural ecosystems. This paper presents state-of-the-art knowledge on peatland GHG fluxes and their key regulating processes, highlighting approaches to study spatio-temporal dynamics, integrated methods, direct and indirect human impacts, and peatlands' perspectives.
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Global peatland greenhouse gas dynamics: state of the art, processes, and perspectives
(2025) Mander, Ülo; Espenberg, Mikk; Öpik, Maarja
Natural peatlands regulate greenhouse gas (GHG) fluxes through a permanently high groundwater table, causing carbon dioxide (CO2) assimilation but methane (CH4) emissions due to anaerobic conditions. By contrast, drained and disturbed peatlands are hotspots for CO2 and nitrous oxide (N2O) emissions, while CH4 release is low but high from drainage ditches. Generally, in low-latitude (tropical and subtropical) peatlands, emissions of all GHGs are higher than in high-latitude (temperate, boreal, and Arctic) peatlands. Their inherent dependence on the water regime makes peatlands highly vulnerable to both direct and indirect anthropogenic impacts, including climate change-induced drying, which is creating anthro-natural ecosystems. This paper presents state-of-the-art knowledge on peatland GHG fluxes and their key regulating processes, highlighting approaches to study spatio-temporal dynamics, integrated methods, direct and indirect human impacts, and peatlands' perspectives.
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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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Greening of a boreal rich fen driven by CO2 fertilisation
(Agricultural and Forest Meteorology, 2024) Thayamkottu, Sandeep; Smallman, T. Luke; Pärn, Jaan; Mander, Ülo; Euskirchen, Eugénie S.; Kane, Evan S.
Boreal peatlands store vast amounts of soil organic carbon (C) owing to the imbalance between productivity and decay rates. In the recent decades, this carbon stock has been exposed to a warming climate. During the past decade alone, the Arctic has warmed by ∼ 0.75°C which is almost twice the rate of the global average. Although, a wide range of studies have assessed peatlands’ C cycling, our understanding of the factors governing source / sink dynamics of peatland C stock under a warming climate remains a critical uncertainty at site, regional, and global scales. Here our focus was on answering two key questions: (1) What drives the interannual variability of carbon dioxide (CO2) fluxes at the Bonanza Creek rich fen in Alaska, and (2) What are the internal carbon allocation patterns during the study years? We addressed these knowledge-gaps using an intermediate complexity terrestrial ecosystem model calibrated by a Bayesian model-data fusion framework at a weekly timestep with publicly available eddy covariance, satellite-based earth observation, and in-situ datasets for 2014 to 2020. We found that the greening trend (a relative increase of leaf area index ∼0.12 m2 m-2 by 2020) in the fen ecosystem is forced by a CO2 fertilisation effect which in combination resulted in increased gross primary production (GPP). Relative to 2014, GPP increased by ∼75 gC m-2 year-1 (by 2020; 95% confidence interval (CI): -41.35 gC m-2 year-1 to 213.55 gC m-2 year-1) while heterotrophic respiration stayed constant. Consistent with the observed greening, our analysis indicates that the ecosystem allocated more C to foliage (∼50%) over the structural (A carbon pool consisting of branches, stems and coarse roots; ∼30%) and fine root C pools (∼20%).