Sirvi Autor "Escuer-Gatius, Jordi" 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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Interactions of fertilisation and crop productivity in soil nitrogen cycle microbiome and gas emissions
(2025) Kuusemets, Laura; Mander, Ülo; Escuer-Gatius, Jordi; Astover, Alar; Kauer, Karin; Soosaar, Kaido; Espenberg, Mikk
Fertilised soils are a significant source of nitrous oxide (N2O), a highly active greenhouse gas and a stratospheric ozone depleter. Nitrogen (N) fertilisers, while boosting crop yield, also lead to N2O emissions into the atmosphere, impacting global warming. We investigated relationships between mineral N fertilisation rates and additional manure amendment with different crop types through the analysis of abundances of N cycle functional genes, soil N2O and N2 emissions, nitrogen use efficiency (NUE), soil physicochemical analysis and biomass production. Our study indicates that N2O emissions are predominantly dependent on the mineral N fertilisation rate and enhance with an increased mineral N fertilisation rate. Crop type also has a significant impact on soil N2O emissions. Higher N2O emissions were attained with the application of manure in comparison to mineral fertilisation. Manure amendment also increased the number of N cycle genes that are significant in the variations of N2O. The study indicates that N2O emissions were mainly related to nitrification in the soil. Quantification of nitrogen cycle functional genes also showed the potential role of denitrification, comammox (complete ammonia oxidation) and dissimilatory nitrate reduction to ammonium (DNRA) processes as a source of N2O. Our study did not find soil moisture to be significantly linked to N2O emissions. The results of the study provide evidence that, for wheat, a fertilisation rate of 80 kg N ha−1 is closest to the optimal rate for balancing biomass yield and N2O emissions and achieving a high NUE. Sorghum showed good potential for cultivation in temperate climates, as it showed a similar biomass yield compared to the other crop types and fertilisation rates but maintained low N2O emissions and N losses in a mineral N fertilisation rate of 80 kg N ha−1.