Sirvi Autor "Kupper, Priit" järgi

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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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Hydraulic and environmental limitations to leaf water relations in trees with respect to canopy position
(2006) Kupper, Priit; Sellin, Arne, juhendaja
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Põdra potentsiaalne viljakus (erinevates vanuserühmades) Eestis aastatel 1993/94...1997/98
(Tartu Ülikool, 1998) Kupper, Priit; Kirk, Anne, juhendaja
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Transitional hypoxia during peatland water table fluctuations drives high N2O fluxes via shifting microbial pathways
(Volume 305, Part 1, 2026) Masta, Mohit; Ali Kazmi, Fahad; Espenberg, Mikk; Visnapuu, Triinu; Sennett, Louise B.; Eving, Lauri; Lewicka-Szczebak, Dominika; Deb, Sushmita; Khanongnuch, Ramita; Kuusemets, Laura; Kupper, Priit; Butterbach-Bahl, Klaus; Mander, Ülo
Nitrogen (N) cycling in peatlands is sensitive to variations in water table, temperature, and soil moisture. Water table fluctuations in peatlands can trigger the formation of transitional oxic and hypoxic zones within the peat and influence N2O fluxes. However, studies exploring these transitions by combining isotopic and microbial analyses are rare. This study assessed the impact of oxic-to-hypoxic transitions on N dynamics in drained peat soil. Birch-planted mesocosms were treated with 15N-NO3- and 15N-NH4+ tracers, while artificial fog generation allowed for the quantification of N2O exchange between the soil surface and the atmosphere. Rewetting reduced soil oxygen levels, significantly increasing N2O fluxes; peak value (162 ± 22.80 μg N m−2 h−1) was recorded under hypoxic conditions. During the transition, the abundance of nirK-type denitrifiers increased. N2O was initially enriched by the 15N-NH4+ tracer, followed by the 15N-NO3- tracer, which contributed significantly to the N2O flux under hypoxic conditions. The 3D FRAME isotope model attributed early N2O production to nitrification (Ni) and nitrifier denitrification (nD); however, it identified a dual contribution from nitrification (Ni) and bacterial denitrification (bD) during the later phases. NosZ genes were detected in birch leaf samples, suggesting a potential aboveground microbial N2O sink. 15N tracer also confirmed the solubility of soil N2O in fog droplets during the experimental period, but the fraction of dissolved N2O was found to be very low (<0.2%). Nonetheless, these findings warrant further research.