Tartu Ülikooli
digitaalarhiiv ADA

ADA, Tartu Ülikooli digitaalarhiivi sisuks on peamiselt Tartu Ülikooli monograafiad, doktoritööd, üliõpilastööd, lõputööd, magistritööd, õppematerjalid, Tartu Ülikooli raamatukogus digiteeritud materjalid ning Tartu Ülikooli teadlaste isikuarhiivid. Digitaalarhiivis olevaid materjale hoitakse turvaliselt ja varustatakse püsilingiga. Teenuse haldamise ja arendamisega tegeleb Tartu Ülikooli raamatukogu.

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disserid2
Doktoritööd al. 2004. MSc, PhD (ETD)
eope
E-õppe materjalid
raamatukogu2
Tartu Ülikooli raamatukogu
muuseum
Tartu Ülikooli muuseum
humanitar
Humanitaarteadused ja kunstid
reaal
Loodus- ja täppisteadused
medika
Meditsiiniteadused
sotsiaal
Sotsiaalteadused
emta2
Eesti Muusika- ja Teatriakadeemia
teadusagentuur
Eesti Teadusagentuur ja teised asutused
ministeerium
Haridus- ja Teadusministeerium
kirjastus
Tartu Ülikooli kirjastus

Hiljutised sisestused

  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
    Impact of drainage on soil CH4 and N2O fluxes in nutrient-rich hemiboreal peatland forests of Europe
    (2026) Kamil-Sardar, Muhammad; Laiho, Raija; Jauhiainen, Jyrki; Butlers, Aldis; Schindler, Thomas; Vahter, Hanna; Čiuldienė, Dovilė; Vigricas, Egidijus; Teemusk, Alar; Kull, Ain; Lazdiņš, Andis; Haberl, Andreas; Bārdule, Arta; Līcīte, Ieva; Samariks, Valters; Mander, Ülo; Armolaitis, Kęstutis; Soosaar, Kaido
    Background and aims Peatland forests play a significant, yet highly variable, role in atmospheric methane (CH4) and nitrous oxide (N2O) emissions. Drainage reduces CH4 but increases N2O fluxes from nutrient-rich soils, creating complex climate trade-offs. To refine regional climate strategies, a clearer understanding of soil fluxes and influencing factors across forest types in the hemiboreal zone is needed. Methods This study presents two years of soil flux and environmental data collected from 2020 to 2023 using manual chambers at 18 drained (DF) and 7 undrained (UF) sites, with different tree species, in Estonia, Latvia, and Lithuania. Results Soil water‑table depth was the primary control on annual CH4 exchange; DF sites acted as CH4 sinks (–4.6 kg ha–1 y–1), whereas UF sites were net sources (38.2 kg ha–1 y–1). In contrast, N2O emissions occurred at all sites, averaging 5.9 kg ha–1 y–1 in DF and 1.4 kg ha–1 y–1 in UF soils. Within DF sites, Myrtillus‑type pine stands exhibited the lowest N2O fluxes, while alder stands showed the highest, followed by birch- and spruce-dominated stands, reflecting differences in hydrology, pH, and C/N ratios of the soil. Conclusions Our findings reveal significantly lower CH4 and moderately higher N2O emissions from DF soils than the IPCC Tier 1 temperate zone emission factor (EF), which has thus far been used for the hemiboreal zone. This study can improve national GHG inventories using specific information. We recommend applying Baltic region-specific EFs, as the mean annual CH4 and N2O emissions showed no significant difference across the three countries.
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
    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.
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
    Genetic Potential for N₂O Metabolism in Tree Tissues: Insights From Nitrogen Cycling Gene Prevalence and nosZ Diversity Across Tree Species
    (2026) Thiyagarasaiyar, Krishnapriya; Paul, Dhiraj; Kerttula, Johanna; Keski-Karhu, Milja; Soosaar, Kaido; Mander, Ülo; Hallin, Sara; Machacova, Katerina; Pumpanen, Jukka; Siljanen, Henri M.P.
    Nitrous oxide (N2O) is a potent greenhouse gas, and microorganisms play a crucial role in its metabolism. While N2O cycling among soil microorganisms is well studied, there is a major knowledge gap regarding the distribution and diversity of these microorganisms within tree ecosystems. In this study, we aimed to comprehensively assess the potential for nitrogen (N) cycling and the diversity of N2O-reducing microorganisms in shoots (leaves and terminal branches) and wood cores of four tree species — European beech (Fagus sylvatica), European hornbeam (Carpinus betulus), birch (Betula pendula and Betula pubescens) and Norway spruce (Picea abies). We assessed N2O exchange through shoot incubation experiments and measured internal N2O concentrations in stem wood. Inorganic N species were studied as indicators of microbial transformation, and a targeted metagenomic approach was used to determine the relative abundance of N-cycling genes and nosZ clade I and II diversity. Our study revealed that hornbeam shoots showed potential N2O emissions (0.002–0.007 ng N2O g⁻¹ FW h⁻¹), while beech shoots indicated N2O consumption (-0.001 to -0.017 ng N2O g⁻¹ FW h⁻¹). Birch had internal stem wood N2O concentration of + 150.39 ppb, and beech − 9.74 ppb when compared to the ambient concentration. Targeted metagenomic analysis revealed the presence of key nitrification and denitrification genes in both tissue types. In particular, nosZ genes were detected in shoots (0 to 26.48 per 100,000 reads) and in wood cores (0 to 31.95 per 100,000 reads), with clade I dominating over clade II and Rhizobiales prevalent within clade I. Overall, our findings show that internal tree tissues harbour distinct N‑cycling microbial assemblages dominated by nosZ clade I, suggesting that trees may function as localized N2O sinks or sources depending on tissue type and microbial composition.
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
    National-scale geospatial modelling of recommended riparian buffer widths
    (2026) Uuemaa, Evelyn; Kmoch, Alexander; Kull, Ain; Mõisja, Kiira; Tominga, Hanna-Ingrid; Guamán-Pintado, Pamela; Mander, Ülo
    Determining optimal riparian buffer widths, especially considering landscape spatial heterogeneity, is challenging, often relying on computationally intensive hydrological models with limited scalability. Empirical nomographs, linking terrain, soil, and slope, offer a more tractable alternative. Building upon a nomograph developed for Estonian catchments in the earlier research, we present its first computational implementation within a geospatial modelling framework. We developed a geospatial modelling algorithm in Python to calculate recommended buffer widths based on slope, specific slope length (synthesised from flow length, slope length, and LS factor), and soil type, utilising high-resolution national datasets. This algorithm was applied to the entire territory of Estonia (approx. 43,000 km2). The model produces spatially explicit buffer width recommendations that reflect local variations in topography and soil conditions. The proposed framework provides a computationally efficient and scalable tool for supporting strategic planning, policy development, and prioritisation of riparian buffer implementation. While not intended for direct site-level design, it offers a robust first-order assessment of spatial patterns in buffer width requirements and can be further refined through local calibration and validation.
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Avatud juurdepääs ,
    Linking nitrogen transformations and soil δ15N to assess drivers of nitrogen losses across a tropical peat swamp forest and an oil palm plantation
    (2026) Wangari, Elizabeth Gachibu; Yung Teo, Kien; Mwanake, Ricky Mwangada; Sangok, Faustina Elfrida; Lindang, Herman Umbau; Chaddy, Auldry; Lau, Sharon Yu Ling; Khan, Fawad; Busman, Nur Azima; Lo, Kim San; Vahter, Hanna; Kamil-Sardar, Muhammad; Kanger, Kärt; Willibald, Georg; Ambus, Per; Pihlatie, Mari; Soosaar, Kaido; Espenberg, Mikk; Butterbach-Bahl, Klaus; Kiese, Ralf; Mander, Ülo; Melling, Lulie
    Conversion of tropical peatland forests to oil palm plantations has been associated with elevated nitrous oxide (N2O) emissions and nitrate (NO3−) leaching, yet the biogeochemical mechanisms driving these nitrogen (N) losses remain poorly understood. To address this gap, soil N2O fluxes, gross N transformation rates, microbial gene abundances, annual NO3− leaching rates, and bulk soil δ15N signatures were quantified along transects in Malaysia that included intact tropical peat swamp forest and drained oil palm plantation. Oil palm plantation sites had higher topsoil oxygen (O2) concentrations than forest sites, indicating that drainage shifts soils from predominantly anaerobic to aerobic conditions. These redox shifts, together with fertilizer inputs, increased nitrifier gene abundances and enhanced gross nitrification rates, which exceeded ammonification rates by up to 186%, promoting soil NO3− accumulation. The elevated soil NO3− concentrations stimulated N2O production, probably through coupled nitrification-denitrification, and increased NO3− leaching. Overall, these results showed that oil palm plantation sites had higher gaseous and hydrological N losses than peat forest sites. Additionally, nitrification rates, hydrological N export, and gaseous N losses were positively correlated with more enriched bulk soil δ15N values along the land use gradient. These findings demonstrated that bulk soil δ15N patterns may have the potential to serve as indicators of long-term N cycling and losses in tropical peatlands associated with human-induced land use changes.
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Piiratud juurdepääs ,
    Kohtuballistikaekspertiis
    (Tartu Ülikool, 2005) Kaing, Hendrik; Lindmäe, Herbert, juhendaja
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Piiratud juurdepääs ,
    Alusetu rikastumise õigus Eestis : (võrdlev käsitlus ja kohtupraktikas kerkinud probleemid)
    (Tartu Ülikool, 2005) Kahn, Katrin; Tampuu, Tambet, juhendaja
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Piiratud juurdepääs ,
    Teenistuskohustuse rikkumine ja selle tagajärjed
    (Tartu Ülikool, 2007) Jõgi, Urve; Merusk, Kalle, juhendaja
  • Pisipilt
    listelement.badge.dso-type Kirje , listelement.badge.access-status Piiratud juurdepääs ,
    Töötaja õiguslik seisund ja nõuete rahuldamine tööandja maksejõuetuse korral
    (Tartu Ülikool, 2007) Kalaus, Tiia; Erikson, Merle, juhendaja