Browsing by Author "Schindler, Thomas"

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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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Importance of N2O in greenhouse gas budgets of tropical peatlands
(Frontiers in Environmental Science, 2025) Pärn, Jaan; Espenberg, Mikk; Soosaar, Kaido; Kasak, Kuno; Thayamkottu, Sandeep; Schindler, Thomas; Ranniku, Reti; Sohar, Kristina; Mander, Ülo; Melling, Lulie; Malaverri, Lizardo Fachín
Tropical peatland ecosystems significantly influence Earth’s climate through their greenhouse gas exchange. Permanently wet peatlands take up carbon dioxide in plants and accumulate organic carbon in soil but release methane. Man-made drainage of peat releases carbon dioxide and nitrous oxide. Exchange of the greenhouse gases in relationship with tropical conditions are poorly understood. This is a global-scale field study of fluxes of three greenhouse gases – carbon dioxide, methane and nitrous oxide – and their environmental drivers across the full moisture range of tropical peatlands. We show that net emission of carbon dioxide dominates greenhouse gas budgets in drained tropical peatlands while nitrous oxide emission is the second most important contributor. Tropical peat swamp forests in their natural wet states are large greenhouse gas sinks and should be a global conservation and restoration priority.
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Temporal and spatial dynamics of microbial communities and greenhouse gas flux responses to experimental flooding in riparian forest soils
(2025) Reiss, Kristel; Mander, Ülo; Öpik, Maarja; Sepp, Siim-Kaarel; Kanger, Kärt; Schindler, Thomas; Soosaar, Kaido; Pihlatie, Mari; Butterbach-Bahl, Klaus; Putkinen, Anuliina; Niinemets, Ülo; Espenberg, Mikk
Extreme rainfall and flooding are expected to increase in Northern subboreal habitats, altering soil hydrology and impacting greenhouse gas (GHG) fluxes by shifting redox potential and microbial communities as soils transition from aerobic to anaerobic conditions. This study examined the effects of a 2-week growing-season flash flood on bacterial, archaeal, and fungal communities and microbial processes driving CH4 and N2O fluxes in riparian alder (Alnus incana) forests. Flooding reduced soil nitrate accumulation as determined by quantitative polymerase chain reaction and promoted dinitrogen-fixing, nifH gene-carrying bacteria like Geomonas. Sequencing data showed that anaerobic bacteria (Oleiharenicola, Pelotalea) increased during the flood, while N2O emissions declined, indicating a shift towards complete denitrification to N2. However, drier patches within the flooded area emitted N2O, suggesting nitrification or incomplete denitrification. A diverse arbuscular mycorrhizal community was detected, including genera Acaulospora, Archaeospora, Claroideoglomus, Diversispora, and Paraglomus. Flooding increased the abundance of the fungal genera Naucoria, Russula, and Tomentella and the family Thelephoraceae, which symbiotically support alder trees in nitrogen uptake and carbon sequestration. Microtopographic differences of 0.3–0.7 m created spatial variability in GHG emissions during flooding, with some waterlogged areas emitting CH4, while others enhanced CH4 oxidation (determined by FAPROTAX) and promoted nitrification-driven N2O emissions in drier, elevated zones. We conclude that flash flooding during the active growing season significantly affects nitrogen-fixing and nitrifying microbes and alters symbiotic fungal community composition, creating spatial variability in GHG emissions.
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Tree stem CH4 and N2O fluxes in various forest ecosystems
(2021-07-07) Schindler, Thomas; Mander, Ülo, juhendaja; Soosaar, Kaido, juhendaja; Machacova, Katerina, juhendaja; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
Metaan (CH4) ja dilämmastikoksiid ehk naerugaas (N2O) on ohtlikud kasvuhoonegaasid (KHG), mille osakaal globaalses kliima soojenemises kasvab. On teada, et maismaaökosüsteemid, eriti metsad reguleerivad nende gaaside emissioone, kuid alles viimasel aastakümnel on seda hakatud neid voogusid lähemalt uurima. Erinevates kliimavööndites, metsaökosüsteemides ja puuliikide tasemel on KHG voogude taga olevate protsesside intensiivsus ja keskkonnatingimuste mõju neile voogudele erinev, mistõttu on oluline nende selgitamine ja kvantifitseerimine. Käesolevas doktoritöös uuriti puutüvede CH4 ja N2O voogude rolli kahes parasvöötme kaldaäärses metsas Eestis ja Doonau jõe vesikonnas (Austrias), troopilises palmisoos Amazonase madalikul Peruus ja troopilises vihmametsas La Reunioni saarel. Lisaks analüüsiti CH4 ja N2O voogude ajalist dünaamikat ja veetaseme mõju nendele voogudele. Uuritud parasvöötme metsamuldade kõrgema veesisalduse korral olid metaani ja naerugaasi emissioonid puutüvedest suuremad, eriti nende madalamates segmentides. Kaldaäärsete metsade puuliikide (hall lepp, harilik saar, paplid) tüveemissioonid sõltusid eeskätt veerežiimist ja temperatuurist, olles kõrgemad märjematel ja jahedatel perioodidel, kusjuures ööpäevaseid voogude muutusi ei täheldatud. Troopikas oli peamiseks teguriks sademete režiim, sest nii aasta- kui ka ööpäevaringselt on õhu- ja mullatemperatuur ühtlaselt kõrge. Seejuures oli tüvevoogude puhul sageli määravaks taimede füsioloogiliste ja morfoloogiliste parameetrite erinevus. Näiteks uuringu tulemused näitavad, et Amazonase soode palmide alumised tüveosad emiteerisid mõlemaid gaase märgatavalt vähem kui ülaosad, mis oli tõenäoliselt tingitud tüvede erinevast morfoloogiast võrreldes puudega. La Reunioni vulkaanilisel saarel täheldatud CH4 ja N2O sidumine puutüvedes oli vähem seotud mullaomadustega, seal mängisid tõenäoliselt olulist rolli tüvesid katvad samblad ja samblikud. Seni tehtud vähesed uuringud näitavad CH4 ja N2O voogude suurt varieeruvust puutüvede ja atmosfääri vahel erinevates metsaökosüsteemides. Mõnes metsas võivad puutüvede ja- võrade gaasivood olla olulisim osa nende gaaside kogubilansis, mis mõnikord muudavad need metsad süsiniku sidujatest selle allikaks. Seetõttu on puude gaasivoogude paremaks mõistmiseks ning metsade globaalse metaani- ja naerugaasibilansi selgitamiseks vajalikud täiendavad interdistsiplinaarsed, eeskätt mikrobioloogilised ja isotoopuuringud.