Põhjapoolkera soode põhjaveetaseme seire täiendamine optiliste ja termiliste satelliidiandmete abil

Väitekirja elektrooniline versioon ei sisalda publikatsiooneSood on märgalad, kuhu taimede mittetäieliku lagunemise tõttu on talletunud palju turvast, , mis sisaldab suurt kogust süsinikku. Turvas on moodustunud aastatuhandete jooksul niisketes tingimustes. Inimtegevuse surve ning globaalne kliima soojenemine on põhjustanud soode kuivenemise ning seetõttu talletunud süsiniku lendumist kasvuhoonegaaside (KHG), peamiselt süsihappegaasina (CO2), mis põhjustab omakorda kliima soojenemist. Ka teised KHG-d, metaan ja naerugaas, lenduvad soodest ja nendegi puhul on olulisimaks teguriks põhjaveetaseme langus. Seetõttu on täpsem teadmine soode põhjaveetaseme muutustest olulise tähtsusega Maa kliima muutumise ennustamisel. Käesolev väitekiri annab ülevaate uuringutest, mille välitööde osa tehti Eestis Endla looduskaitsealal Männikjärve ja Linnusaare rabades, võrdlevad analüüsid aga sarnaste soodega Soomes, Rootsis, Kanadas ja USA-s. Töö peamiseks eesmärgiks oli täiendada Põhjapoolkera soode põhjaveetaseme sattelliidi-põhist kaugseiret, mille alusel hinnati tulemuste olulisust, võrreldes seda soodes tehtud kohapealsete mõõtmistega. Esmakordselt näidati, et kasutatud optiliste ja termiliste spektrite signaalid, mis on turba veesisalduse ja rohelise (kasvuperioodi) taimkatte määramise seisukohast kõige tundlikumad, , iseloomustavad usaldusväärselt soode põhjaveetaset. Täiendava uuringuga taimkatte mõjust seosele leiti vastav niiskusindeks ja selle kõige usaldusväärsemad kohad (pikslid) soodes, mis omakorda võimaldas üldistada tulemust kogu soo ulatuses. Algselt Eesti soodes välja töötatud metoodika õigustas ennast ka teistes soodes nii Euroopas kui ka Põhja-Ameerikas ning seda soovitatakse kasutada edasistes uuringutes.Peatlands are a type of wetlands, which have accumulated huge quantities of carbon as a plant matter. The accumulation of this carbon occurred in water-logged conditions and took thousands of years. Global climate change can lead to the drying of peatlands and, thus, the release of accumulated carbon in the form of greenhouse gas – carbon dioxide (CO2). Releasing CO2 into the atmosphere will amplify global climate change. Therefore, knowledge of water table depth in peatlands is essential for predicting future Earth climate. In this thesis, we present results of our four articles integrated together and they share one general aim – to improve the estimation of water table depth in Northern Hemisphere peatlands using remotely sensed information in thermal and optical spectra. We evaluated the usefulness of this information to detect the temporal and spatial changes in water table depth based on in-situ data collected in peatlands. Particularly, we used signals sensitive to moisture and green vegetation, and utilized them in several indices that indicate soil moisture conditions. In this thesis, we have determined, for the first time, that used in our study moisture index based on optical data has a strong temporal relationship with in-situ measured water table depth in peatlands. Moreover, we discussed the impact of vegetation cover on that relationship and suggested a method for selecting the most informative pixels of moisture index. In conclusion, we suggest the future perspectives of using optical-based moisture index together with challenges it might have.https://www.ester.ee/record=b536954

PEAT-CLSM : A Specific Treatment of Peatland Hydrology in the NASA Catchment Land Surface Model

Peatlands are poorly represented in global Earth system modeling frameworks. Here we add a peatland-specific land surface hydrology module (PEAT-CLSM) to the Catchment Land Surface Model (CLSM) of the NASA Goddard Earth Observing System (GEOS) framework. The amended TOPMODEL approach of the original CLSM that uses topography characteristics to model catchment processes is discarded, and a peatland-specific model concept is realized in its place. To facilitate its utilization in operational GEOS efforts, PEAT-CLSM uses the basic structure of CLSM and the same global input data. Parameters used in PEAT-CLSM are based on literature data. A suite of CLSM and PEAT-CLSM simulations for peatland areas between 40 degrees N and 75 degrees N is presented and evaluated against a newly compiled data set of groundwater table depth and eddy covariance observations of latent and sensible heat fluxes in natural and seminatural peatlands. CLSM's simulated groundwater tables are too deep and variable, whereas PEAT-CLSM simulates a mean groundwater table depth of -0.20 m (snow-free unfrozen period) with moderate temporal fluctuations (standard deviation of 0.10 m), in significantly better agreement with in situ observations. Relative to an operational CLSM version that simply includes peat as a soil class, the temporal correlation coefficient is increased on average by 0.16 and reaches 0.64 for bogs and 0.66 for fens when driven with global atmospheric forcing data. In PEAT-CLSM, runoff is increased on average by 38% and evapotranspiration is reduced by 19%. The evapotranspiration reduction constitutes a significant improvement relative to eddy covariance measurements.Peer reviewe

Recovery of carbon stocks after wildfires in boreal forests : a synthesis

Book of abstracts Cool forests at risk? The Critical Role of Boreal and Mountain Ecosystems for People, Bioeconomy, and ClimatePeer reviewe

Simulating urban soil carbon decomposition using local weather input from a surface model

Non peer reviewe

GPS-based studies on human activity space: data infrastructure in the Mobility Lab of the University of Tartu

Knowledge on the spatiotemporal dynamics of people is important for public governance, policy-making, research and development. The Era of Big Data has provided unprecedented possibilities to track human mobility, and has also raised new risks and challenges. The Mobility Lab at the University of Tartu has 15 years of experience in making use of passive and active mobile positioning datasets in a wide variety of research directions. As a more recent spatiotemporal data type for the lab, the longitudinal GPS-tracking dataset has opened up new frontiers in studying human dynamics since 2013. The smart phone application MobilityLab, developed jointly by the Mobility Lab and Cambridge Computer Laboratory, collects various locational and behavioural data on a voluntary basis. MobilityLog surveys are complemented by qualitative interviews held both at the beginning and end of the automated data collection period. The interviews cover the semantics of visited places, travel behaviour, use of information and communication technology, main social contacts, and social characteristics of sample. The Mobility Lab has just started new GPS-based longitudinal surveys in the field of segregation, environmental exposure, and transnationality.Non peer reviewe

Změny na krajinné škále v období okolo přelomu pleistocén-holocén a v antropocénu ve střední Evropě

Práce se zabývá dynamikou středoevropské krajiny. Zahrnuty jsou čtyři případové studie zaměřené na dvě klíčová období environmentální transformace: pozdní glaciál a antropocén. Všechny případové studie spojuje krajinná škála jako prostorové měřítko zkoumaných jevů, tedy nejen jako prostorový rozsah výběru vzorků, jak je rámcově popsáno v úvodu. Případové studie využívají disparátní kontexty a metody, což napomáhá přiblížení se tak komplexnímu fenoménu - krajině. Zahrnuté studie se zabývají krajinou a vegetací posledního glaciálu, a to (1) srovnáváním pylových záznamů napříč ČR s využitím moderních analogií (zde z Jakutska), které ukázalo, že změna na přechodu pozdního glaciálu a holocénu nemusela být tak velká, jak se dosud předpokládalo. Alespoň někde mohly již během posledního glaciálu existovat lesy podporované táním permafrostu. Navazující studie (2) zkoumá, jak tání permafrostu, tzv. termokrasové procesy vedly ke genezi celé jezerní krajiny, jejíž dědictví na Třeboňsku nečekaně přetrvalo až do současnosti. Na to navazuje studie (3) využívající podrobného paleoenvironmentálního záznamu sedimentů objevených jezer s využitím především geochemických sedimentologických metod. Dynamika eroze a pedogeneze během klimatických výkyvů v pozdním glaciálu odhalila dalekosáhlé změny krajiny v časovém...This thesis investigates the dynamics of the central European landscape. Four case studies, exploring two key periods of environmental transformation: Late Glacial and the Anthropocene, are included. All case studies are connected by the spatial scale of interest: the landscape scale. This scale is targeted not only by the spatial extent of the sampling, but by the essence of the issues investigated, as broadly described in the introduction. The studies use disparate methods and different contexts, which helps to approach such a complex phenomenon - the landscape and its formation. The included studies are dealing with the Last Glacial landscape and vegetation by (1) comparing pollen records using modern analogues (here from Yakutia) and argues that the change at the Late Glacial/Holocene transition may not have been as great as previously thought, because at least somewhere forests may had existed during the Last Glacial being supported by permafrost melting. A follow-up study (2) explores how permafrost melting, i.e., thermokarst processes, generated an entire lake landscape whose remnants unexpectedly largely persist in the Třeboň region (southern Czech Republic) to recent times. This is followed by (3) the use of a detailed palaeoenvironmental record of the discovered lakes and their contexts...Katedra botanikyDepartment of BotanyPřírodovědecká fakultaFaculty of Scienc