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Contents 0 Acknowledgements ...... 1 1 List of Included Publications ...... 2 2 Summary ...... 3 3 Introduction ...... 5 3.1 Terms and Definitions...... 6 4 Quantity of Plant Species Richness ...... 7 4.1 How Many Species? ...... 7 4.2 Geographic Distribution, Hotspots and Endemism ...... 8 5 Scales: Taxonomic, Spatial and Temporal Scale ...... 13 6 Measuring Biodiversity ...... 17 6.1 Species Richness, Equitability, Abundance, Functional Diversity ...... 17 6.2 Spatial Levels of Species Diversity...... 22 6.3 Monitoring and Field Measurements...... 25 6.4 Sampling...... 27 6.4.1 Random vs. Non-Random Sampling (Example I)...... 28 7 Species Richness and Sampling Area ...... 31 7.1 Island Biogeography...... 31 7.1.1 Species-Area Effects (Example II)...... 33 7.1.2 Species Richness and Islands Size (Example III)...... 36 7.2 Landscape Heterogeneity ...... 37 7.2.1 Bryophytes and Landscape Heterogeneity (Example IV) ...... 39 8 Species Diversity and Environment at Different Spatial Scales ...... 42 8.1 Large Gradients Complexes: Latitude and Altitude...... 44 8.2 Regional Scale ...... 49 8.2.1 Macroclimate (Example V) ...... 49 8.3 Local Scale ...... 51 8.3.1 Soil pH (Example VI)...... 51 8.3.2 Disturbance...... 59 8.3.2.1 Human Trampling (Example VII)...... 63 8.3.2.2 Grazing (Example VIII)...... 65 8.3.2.3 Shrub Expansion and Grazing (Example IX)...... 70 8.3.3 Resource Availability, Competition and Productivity...... 72 8.3.3.1 Light Effects (Examples X, XI, XII, XIII) ...... 74 8.3.3.2 Productivity (Examples XIV, XV) ...... 80 9 Species Diversity in Time ...... 86 9.1 Historical Development...... 86 9.1.1 Time of Isolation of the German Frisian Islands (Example XVI)...... 87 9.2 Succession ...... 90 9.2.1 Coastal Dune Succession (Example XVII) ...... 93 9.3 Biological Invasions...... 97 9.3.1 Native Species Richness and Biological Invasion (Example XVIII)...... 98 10 Short Conclusion ...... 101 11 References ...... 102

12 Appendix ...... 137 12.1 Reprints of Publications ...... 137 12.1.1 Coastal dune succession and plant diversity on a German Wadden Sea Island 137 12.1.2 Interactive effects of rabbit grazing and environmental factors on plant species-richness on dunes of Norderney ...... 159 12.1.3 Classification and habitat characteristics of plant communities invaded by the non-native Rosa rugosa Thunb. in NW Europe...... 172 12.1.4 Expansion of Rosa rugosa and Hippophaë rhamnoides in coastal grey dunes: effects at different spatial scales...... 191 12.1.5 Effects of Rosa rugosa invasion in different coastal dune vegetation types..... 200 12.1.6 Diversity of bryophytes in an urban area of NW Germany ...... 219 12.1.7 Random vs non-random sampling: effects on patterns of species abundance, species richness and vegetation-environment relationships...... 227 12.1.8 Effects of the expansion by Hippophaë rhamnoides on plant species richness in coastal dunes ...... 240 12.1.9 Species richness in Sea-Buckthorn scrub...... 251 12.1.10 Soil pH and species diversity in coastal dunes...... 256 12.1.11 Differences in species richness on non-native and native plants between the East and North Frisian Islands ...... 267 12.2 Complete Publication List...... 270 Acknowledgements 1

0 Acknowledgements I would like to express my sincere gratitude to Prof. Dr. Martin Diekmann, the chief of the research group “vegetation ecology and conservation biology” for his support and patience throughout this time.

Special thanks are due to Prof. Dr. Ellen Kiel, Oldenburg, for encouraged mentoring for some years.

Thanks