Multiscale studies of the peatland-atmosphere interactions in northern Eurasia

• Main Author: Alekseychik, Pavel
• Other Authors: Christensen, Torben, University of Helsinki, Faculty of Science, Department of Physics, Division of Atmospheric Sciences, Helsingin yliopisto, matemaattis-luonnontieteellinen tiedekunta, fysiikan laitos, Helsingfors universitet, matematisk-naturvetenskapliga fakulteten, institutionen för fysik, Vesala, Timo, Mammarella, Ivan
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Helsingin yliopisto 2017
• Subjects: Arctic; Climate change; Subarctic
• Online Access: http://hdl.handle.net/10138/228545

North Eurasia (NE) is recognized as a region of high importance for the global climate change. Large and systematic shifts in temperature and precipitation, predicted for NE, are expected to cause irreversible disturbances in the ecosystem-atmosphere interactions. The region is dominated by natural boreal and arctic ecosystems, which are experiencing increasing levels of anthropogenic influence through environmental pollution (mainly agriculture- and mining-related) and land use change. However, despite the general consensus on the importance of environmental changes in NE, many aspects of the problem remain poorly understood. Due to the great extent of NE, many crucial areas remain inaccessible or lack the required infrastructure, thereby relevant surface-atmosphere exchange measurement data remains scarce. This thesis examines the surface budgets of carbon dioxide and energy of subarctic peatlands, which count among the most important ecosystems in NE owing to their large carbon storage and areal coverage, and their high sensitivity to climate and land use changes. Peatlands are also heterogeneous ecosystems, with large diversity found both internally and between the ecosystem subtypes. Peatland heterogeneity is notable on several characteristic scales, including the single plant, microsite, microtopography element and ecosystem type. Different scales of variation are covered with specific measurement techniques, i.e. plant-scale gas exchange, chamber and eddy-covariance (EC) technique. The latter is in the focus of this work. Aerodynamic roughness length (z0) and photosynthesis rate measured by EC were compared with the plant- and microsite-scale measurements of leaf area index (LAI) and photosynthesis rate. High correspondence between the estimates on different scales was found, indicating that the transition between the upscaled plant and ecosystem-scale estimates is possible, and thus adding credibility to both. In the fen Siikaneva-1, LAI showed a strong linear relationship with z0, while the EC-derived ...