Specialeforsvar: Jesper Rauff Schultz

The distribution of Lobelia dortmanna in Nationalpark Thy and the relationships with geographical and physio-chemical parameters

Supervisor: Prof Ole Pedersen, Department of Biology, UCPH

External examiner: Prof Morten Foldager, RUC

In Nationalpark Thy some of the most pristine, oligotrophic, low alkaline lakes in Denmark are found. They make a habitat for the isoetid Lobelia dortmanna. These lakes are likely to be subjected to an enhanced brownification due to the plantations in the catchment area. This process is considered a threat to plants of the isoetid growthform as L. dortmanna, because it can limit light for photosynthesis or increase organic matter content in the sediments leading to radial oxygen loss. This study investigates how L. dortmanna is distributed in 83 lakes in Nationalpark Thy. Field investigations were performed to obtain physio-chemical parameters and data on land use and soil type cover in the lake cathments was obtained by cathcment buffers. This data was used in analyses of the different parameters relation to L dortmanna presence. The analyses showed no direct impact of the momentary concentration of CDOM on the presence of L. dortmanna. CDOM was found to be closely related to the terrestrial surroundings through correlation analyses. It was shown that area and shoreline were the only factors that had a positive effect on the presence of L. dortmanna. By logistic regression, a model was built to provide the best predictors of L. dortmanna presence between our different datasets in Nationalpark Thy.

Lobelia lake. Photo: Jesper Rauff Schultz