Ecological Characteristics of Dune Heath Lakes in Thy National Park – Threats and future Management Michael Straarup Nielsen Institute for Bioscience – Aquatic Biology Aarhus University Lobelia dortmanna 60 ECTS Master’s Thesis Title Danish Økologiske Karakteristika af Klithedesøer i Nationalpark Thy – Trusler og Fremtidig Forvaltning Title English Ecological Characteristics of Dune Heath Lakes in Thy National Park – Threats and future Management Author Michael Straarup Nielsen (201205459) Supervisor Tenna Riis, Institute for Bioscience – Aquatic Biology, Aarhus University Date 7-12-2018 Front- and backpage Aquarel and pencil by Michael Straarup Nielsen. 1 Table of Contents List of Tables ...................................................................................................................................... 4 List of Figures ..................................................................................................................................... 4 Abstract ............................................................................................................................................... 5 Danish Abstract .................................................................................................................................. 6 Introduction ........................................................................................................................................ 7 Threats to Coastal Dune Systems.................................................................................................. 7 Plant Communities in Dune Lakes ............................................................................................... 8 Methods ............................................................................................................................................. 10 Study site and sampling design ................................................................................................... 10 Selecting lakes for sampling ........................................................................................................ 10 Vegetation sampling ..................................................................................................................... 12 Physico-chemical sampling .......................................................................................................... 13 Organic Matter ............................................................................................................................ 13 Nutrients and Trace Elements ..................................................................................................... 13 Chlorophyll-a .............................................................................................................................. 14 Alkalinity and pH ....................................................................................................................... 14 Stable Isotope Analysis ............................................................................................................... 15 Germination of Seed Banks ............................................................................................................ 15 Multivariate Methods ..................................................................................................................... 16 Geographic Information System .................................................................................................... 16 Results ............................................................................................................................................... 17 Physico-chemical Analysis ........................................................................................................... 17 Lake Conditions in Relation to Land-use ................................................................................... 18 Spearman’s Rank Correlations ................................................................................................... 20 Stable Isotope Analysis ................................................................................................................ 21 Species Diversity ........................................................................................................................... 23 Vegetation distribution ................................................................................................................ 24 DCA Explained by Physico-chemical Gradients ....................................................................... 26 Germination of Seed Banks ......................................................................................................... 26 Discussion .......................................................................................................................................... 27 Land-use Effects on Lake Chemical Conditions ....................................................................... 27 2 Relationship between lake chemical conditions and vegetation distribution ......................... 29 Further Threats to Dune Lakes in Thy National Park ............................................................. 31 Future Management of Dune Lakes ........................................................................................... 33 Conclusion ..................................................................................................................................... 34 Acknowledgements........................................................................................................................... 36 References ......................................................................................................................................... 37 Appendix 1 ........................................................................................................................................ 41 Appendix 2 ........................................................................................................................................ 42 Appendix 3 ........................................................................................................................................ 43 Appendix 4 ........................................................................................................................................ 44 Appendix 5 ........................................................................................................................................ 45 Appendix 6 ........................................................................................................................................ 46 Appendix 7 ........................................................................................................................................ 47 Appendix 8 ........................................................................................................................................ 48 3 List of Tables Table 1: Summary of physico-chemical factors ................................................................................ 17 Table 2: Aquatic macrophyte diversity indices. ................................................................................. 23 Table 3: The 20 most common plant species found in lakes ............................................................. 24 Table 4: Spearman's Rank correlation coefficients ............................................................................ 26 Table 5: Identifiable plant species found in sediment samples. ......................................................... 27 List of Figures Figure 1: Isoetes echinospora. .............................................................................................................. 9 Figure 2: Flowering Lobelia dortmanna. ............................................................................................. 9 Figure 3: Shallow lake near Tved Klitplantage. ................................................................................ 12 Figure 4: Map showing areas with 50 examined lakes ...................................................................... 11 Figure 5: Transect method used for vegetation sampling. ................................................................. 12 Figure 6: PCA-ordination for August ................................................................................................ 18 Figure 7: PCA-ordination for November. .......................................................................................... 19 Figure 8: Clustering of isotopic fingerprints of lake 12_6. ................................................................ 21 Figure 9: Clustering of isotopic fingerprints of lake 12_28. .............................................................. 22 Figure 10: Clustering of isotopic fingerprints of lake 12_21. ............................................................ 23 Figure 11: DCA-ordination of lakes and plant species. ..................................................................... 25 Figure 12: Ortophotos showing part of Hanstholm Game Reserve ................................................... 31 List of Appendices Appendix 1: Physico-chemical factors, August 2017.......………………………………………….41 Appendix 2: Physico-chemical factors, November 2017..………………………………………….42 Appendix 3: Spearman’s Rank Correlation Coefficients for August……………………………….43 Appendix 4: Spearman’s Rank Correlation Coefficients for November……..……….…………….44 Appendix 5: Isotopic Fingerprints