The doctoral dissertation in the field of Geography will be examined at the Faculty of Social Sciences and Business Studies at Joensuu Campus and online.
What is the topic of your doctoral research? Why is it important to study the topic?
My dissertation explores how drones can be used to detect and assess mires. It focuses on mapping vegetation at different spatial scales, i.e. microhabitats, plant communities, and Sphagnum species, and evaluating map accuracy. The study examines aapa and palsa mire complexes in Finland—vulnerable habitats undergoing natural and climate-driven changes reflected in vegetation patterns, with particularly Sphagnum mosses as indicators. Using different drones and sensors alongside field surveys, the research combines new technology with traditional methods to produce detailed vegetation maps. Such maps are crucial: in aapa mires, fen–bog transitions can lead to an increase in bog vegetation at the expense of fen species, with potential implications for carbon sequestration. In palsa mires, the thawing of permafrost lenses typically drives degradation, followed by vegetation succession.
What are the key findings or observations of your doctoral research?
Mapping ecosystems with drones allows detection of fine-scale vegetation typical for mires, beyond what satellite data can resolve. As drone applications rapidly expand, we must ask how much to invest in advanced technology for monitoring and what trade-offs exist. This work shows that microhabitats can be mapped with standard RGB sensors at approximately 30 centimetres spatial resolution, while plant communities require less than 10 centimetres spatial resolution with near-infrared bands. The results also indicate that even hyperspectral sensors covering 400–1000 nanometre may be insufficient to distinguish moss species, leaving open the question of whether even more advanced or costly sensors would be necessary. Besides spatial resolution, accuracy also depends on water level and vegetation phenology. The study highlights these factors and provides thematic, numerical, and map-based guidance, offering value to researchers and ecologists.
How can the results of your doctoral research be utilised in practice?
Accurate vegetation maps guide restoration, conservation planning, and evaluation of ecosystem services, benefiting both practitioners and society. This work also offers practical tools. For example, an alternative map combines the most likely and second-most likely plant communities in areas of lower reliability. Such information helps managers and planners interpret uncertainty, make informed decisions, and prioritize actions, demonstrating how advanced drone-based mapping can support practical ecosystem management and monitoring. Importantly, peatlands are not unique to Finland, but they occur worldwide. The approaches developed in this dissertation can therefore be applied globally and are not even limited to peatlands. Developed mapping principles are also applicable to other landscapes.
What are the key research methods and materials used in your doctoral research?
The dissertation followed a categorical approach. First, I conducted drone-based mapping comparing simple RGB sensors with commonly used multispectral sensors, which include red-edge and near-infrared bands, testing different spatial resolutions to determine the minimum requirements for plant community maps. Next, I applied a State-of-the-Art hyperspectral drone sensor and field imager to assess the spectral separability of dominant Sphagnum moss species and created corresponding maps. The final study integrated these lessons, using probability statistics and an alternative map to improve interpretation of vegetation patterns. It also addressed temporal variation, comparing map accuracy from imagery acquired at the same time in two different years.
The doctoral dissertation of Franziska Wolff, M.Sc., entitled Detecting and Assessing Mire Vegetation using Unoccupied Aerial Vehicles will be examined at the Faculty of Social Sciences and Business Studies. The opponent will be Professor Sebastian van der Linden, University of Greifswald, and the custos will be Professor Timo Kumpula, University of Eastern Finland. The language of the public defence is English.
