PHD DEFENCE: Biogenic carbon cycling dynamics in diverse urban green spaces

Esko Karvinen, MMM will defend the doctoral dissertation entitled “Biogenic carbon cycling dynamics in diverse urban green spaces” in the Faculty of Agriculture and Forestry, University of Helsinki, on 16 June 2026 at 12:00. The aim of this thesis was to enhance our understanding of the biogenic carbon cycling dynamics in diverse urban green spaces such as parks, urban forests, lawns, and meadows. In particular, the goal was to provide estimates of carbon sequestration in such areas.

Urban green spaces produce various ecosystem services ranging from runoff-water and air temperature management to supporting biodiversity and wellbeing of citizens. Yet, biogenic carbon cycling dynamics in urban green spaces and, consequently, their role in climate change mitigation and adaptation remain understudied, especially in high-latitude regions. This research gap complicates comprehensively considering their climatic impacts in sustainable urban planning.

Field measurement campaigns spanning multiple years were performed and the acquired results were used together with various remote sensing data sources to analyse, for example, soil respiration and plant photosynthesis. In addition, process-based ecosystem models were used to both temporally upscale the momentary measurements and to simulate scenarios related to, for instance, the development of carbon sequestration in future climate. Central part of the work was to validate the performance of originally non-urban process-based ecosystem models in cities, where the environmental conditions experienced by vegetation differ from the context the models were originally developed for.

Results of the study portrayed tree-covered areas as central carbon sinks both now and in the future, while carbon sequestration of lawns and meadows was observed to fluctuate more based on weather conditions. In this respect, meadows were found to be more resistant to drought conditions, which should be noted as droughts are predicted to be more frequent and severe in the future. The results underlined the role of soil in both determining the carbon balance of urban green spaces and affecting the applicability of process-based ecosystem models, as the soil materials and growing media used in green space construction can contain higher concentrations of carbon in comparison to typical soil in corresponding natural ecosystems.

Overall, the collected measurement datasets, presented modelling approaches, as well as the addressed limitations in current research both aid in directing future research efforts on the topic and support sustainable urban planning.