Sirvi Märksõna "Carbon dioxide" järgi

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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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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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Long-term carbon sequestration and heatwave resilience in an old hemiboreal upland coniferous forest
(Agricultural and Forest Meteorology, 2025) Rogozin, Svyatoslav; Krasnova, Alisa; Mander, Ülo; Uri, Veiko; Soosaar, Kaido
Boreal forests play an important role in the global carbon cycle due to their extensive area and ability to sequester a considerable amount of atmospheric carbon dioxide (CO2). They are generally stable ecosystems that function as carbon sinks. However, their sink capacity is vulnerable to the impact of extreme weather conditions. In this study, we aim to investigate the multi-year and seasonal carbon dynamics of an old upland coniferous forest in the hemiboreal zone, identify the main environmental drivers influencing annual NEP, and explore the potential legacy effects of the 2018 heatwave. Over an eight-year period (2016–2023), the forest shifted from a carbon sink (mean net ecosystem productivity (NEP) of 238 ± 52 g C m−2 year−1) to a carbon-neutral state in 2020 (NEP = -2 ± 5 g C m−2 year−1) and back to a net carbon sink (NEP = 136 ± 50 g C m−2 year−1). The average NEP over the eight-year period was 170 ± 42 g C m−2 year−1. Our research showed no significant year-to-year changes in GEP during the study period, while the changes in Reco were substantial. Our results confirm that air temperature has the greatest influence on annual NEP. The warmest autumn over the past 19 years, recorded in 2020, and an atypical June together resulted in a noticeable increase in ecosystem respiration, which shifted annual NEP towards negative net values, while no significant impact on GEP was found. Additionally, our study found that the old upland hemiboreal forest showed no legacy effect in the years following the 2018 heatwave, demonstrating its resilience to extreme temperature events. Our results underscore the importance of continuous monitoring carbon dynamics variability to determine the ecosystem's resilience to seasonal temperature fluctuations and to inform management strategies for forests preservation.
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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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Springtime soil and tree stem greenhouse gas fluxes and the related soil microbiome pattern in a drained peatland forest
(2025) Ranniku, Reti; Kazmi, Fahad Ali; Espenberg, Mikk; Truupõld, Joosep; Escuer‑Gatius, Jordi; Mander, Ülo; Soosaar, Kaido
Spring can be a critical time of year for stem and soil methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions as soil freeze–thaw events can be hot moments of gas release. Greenhouse gas fluxes from soil, Downy birch (Betula pubescens) and Norway spruce (Picea abies) stems were quantified using chamber systems and gas analysers in spring 2023 in a northern drained peatland forest. Dissolved gas concentrations in birch sap and soil water, environmental parameters, soil chemistry, and functional gene abundances in the soil were determined. During spring, initially low soil and stem CH4, N2O, and CO2 emissions increased towards late April. Temperature emerged as the primary driver of soil and stem fluxes, alongside photosynthetically active radiation influencing stem fluxes. Soil hydrologic conditions had minimal short-term impact. No clear evidence linked stem CH4 emissions to birch sap gas concentrations, while relationships existed for CO2. Functional gene abundances of the N and CH4-cycles changed between measurement days. Potential for methanogenesis and complete denitrification was higher under elevated soil water content, shifting to methanotrophy and incomplete denitrification as the study progressed. However, our results highlight the need for further analysis of relationships between microbial cycles and GHG fluxes under different environmental conditions, including identifying soil microbial processes in soil layers where tree roots absorb water.