Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea: Analyses along a complex ecological gradient Dissertation zur Erlangung des Doktorgrades des Departments Biologie der Fakultät Mathematik, Informatik und Naturwissenschaften der Universität Hamburg Antonia Wanner aus Hannover Hamburg, 2009 Antonia Wanner Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea Index I Tables V Figures VII 1 Introduction 1 2 Study regions and sites 5 2.1 Climate, vegetation zones 5 2.2 Hydrology 7 2.2.1 Salinity 7 2.2.2 Flooding characteristics 8 2.2.3 Ice cover 10 2.3 Land rise and soils, development of salt grasslands 11 2.3.1 Land rise and soil development 11 2.3.2 Development of salt grasslands 11 2.3.3 Zonation 12 2.4 Salt grasslands: Distribution, decline and management (history) 13 2.4.1 Estonia 13 2.4.2 Schleswig-Holstein 14 2.4.3 Mecklenburg-Vorpommern 14 2.4.4 Northern Denmark 15 2.5 Overview of all study sites 16 Part 1: Impact of management on Baltic salt grassland vegetation: analyses along a complex ecological gradient 22 Introduction 22 3 Methods 27 3.1 Vegetation analysis 27 3.2 Characterisation of site conditions 27 3.3 Data analysis 30 3.3.1 Different measures of diversity 30 3.3.2 Species traits 31 3.3.3 Statistical analysis 33 I Antonia Wanner Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea 4 Results 37 4.1 Abiotic site conditions 37 4.2 Management history, ‚natural’ grazing 38 4.3 Vegetation structure 40 4.4 Species richness and diversity 41 4.4.1 Species richness and spatial scale: impact of management and region 41 4.4.2 Species richness and cover of Phragmites australis 43 4.4.3 Species-area-curves 44 4.4.4 Evenness 44 4.4.5 Diversity and salt grassland soil types 45 4.4.6 Impact on species richness: site conditions and vegetation structure 49 4.5 Species composition 51 4.5.1 Ordination 51 4.5.2 Mean Ellenberg values 52 4.5.3 Species groups 52 4.6 Individual species 58 4.7 Conservation perspective 61 4.7.1 Characteristic species 61 4.7.2 Red List species 62 5 Discussion 64 5.1 Discussion of methods 64 5.2 Environmental gradients 65 5.3 Plant geographic perspective 71 5.3.1 Comparison of the Baltic with the North Sea region 71 5.3.2 Shift of ecological species groups 73 5.3.3 Species’ distribution patterns along the Baltic Sea ecological gradient 74 5.3.4 Distribution boundaries 76 5.4 Impact of management 77 5.4.1 Changes of vegetation structure 77 5.4.2 Length of the successional trajectory 78 5.4.3 Change of strategy types 79 5.4.4 Change of individual species 81 5.4.5 Factors steering the speed and direction of succession 83 5.4.6 Differences in speed and direction of succession between regions 88 5.5 Diversity 91 5.5.1 Diversity along environmental gradients 91 5.5.2 Diversity and management – different diversity measures 94 II Antonia Wanner Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea Part 2: Impact of grazing, abandonment and restoration on vegetation and seed banks of salt grasslands in Estonia 97 Introduction 97 6 Methods 99 6.1 Soil seed bank 99 6.2 Data analysis 99 6.2.1 Classification of the seed bank and longevity of seeds 100 6.2.2 Diversity and similarity indices 100 6.3 Statistical Analysis 101 7 Results 105 7.1 Site conditions 105 7.2 Vegetation analysis 106 7.2.1 Species diversity 106 7.2.2 Vegetation structure 107 7.2.3 Impact of management on species’ cover and frequency 108 7.2.4 Species groups 109 7.2.5 Spatial heterogeneity 111 7.2.6 Species composition and relation to abiotic conditions 111 7.2.7 Impact of vegetation structure and site conditions on species richness 112 7.3 Seed bank analysis 113 7.3.1 Species composition 114 7.3.2 Impact of management on species’ seed density and relative abundance in seed bank and aboveground vegetation 115 7.3.3 Species groups 117 7.3.4 Similarity index 121 7.3.5 Spatial heterogeneity 122 7.3.6 Longevity 122 8 Discussion 125 8.1 Abiotic characteristics 125 8.2 Vegetation changes during progressive secondary succession 125 8.2.1 Species richness and management 125 8.2.2 Species richness and environmental factors 126 8.2.3 Vegetation structure and changes in species composition in the course of succession 127 8.3 Vegetation changes during retrogressive succession (restorative grazing) 128 8.4 Impact of succession on the seed bank 129 8.4.1 Discussion of methods 129 8.4.2 General characteristics of the seed bank 131 8.4.3 Changes after abandonment 132 8.4.4 Seed banks as a source for restoration? 134 III Antonia Wanner Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea 9 Part 3: A method for classifying coastal marshes of the German Baltic Sea for the European Water Framework Directive 141 9.1 Introduction 141 9.2 Coastal marshes as part of the coastal water bodies 141 9.3 Scale of classification: reference conditions 142 9.4 Hydromorphological parameters 143 9.4.1 Flooding dynamics 143 9.4.2 Intensity of drainage 144 9.4.3 Restriction of flooding 144 9.5 Vegetation parameters 145 9.5.1 Normative definitions of the WFD for angiosperms 145 9.5.2 Quantity: Coastal marsh area 145 9.5.3 Quality: Zonation 146 9.5.4 Quality: Plant species composition 148 9.6 Water bodies for which coastal marshes should be considered in the WFD-classification 149 9.7 Combining parameters to an overall assessment 150 9.8 Monitoring 151 9.9 Perspectives 152 10 Conclusions for nature conservation management 153 10.1 Two general concepts for nature conservation in coastal ecosystems 153 10.2 Consequences of management on the vegetation 154 10.2.1 ‘Characteristic’ species 155 10.2.2 Red List species 155 10.2.3 Impact of restorative grazing of Estonian salt grasslands 156 10.2.4 Potential of the seed bank for restoration 158 10.3 Consequences of management on some animal groups 158 10.3.1 Birds 158 10.3.2 Amphibians 160 10.3.3 Invertebrates 160 10.4 Consequences of management on ecosystem functions 161 10.5 Conclusions 164 11 References 169 Annexes Summary Acknowledgement IV Antonia Wanner Management, biodiversity and restoration potential of salt grassland vegetation of the Baltic Sea Tables Table 2-1: Average number of flooding days/year at several water level stations in the four study regions.....…… …...10 Table 2-2: Overview of all study sites……………. ……………………………………………………………………..17 Part 1 Table 3-1: Database for relating elevation of study sites to mean sea level, and for calculating flooding frequencies…29 Table 3-3: Transformation of modified Braun-Blanquet-scale to a metric scale of percentage cover class means……..30 Table 3-4: Socio-ecological classification of all species in the vegetation data set……………………………………...31 Table 3-5: Indicator values of salinity tolerance by Ellenberg et al. (1992) and Scherfose (1990)……………………...32 Table 4-1: Differences of abiotic characteristics between regions and/or management classes…………………………38 Table 4-2: Period of abandonment (in years) of ‚early’ and ‚late’ successional sites in the four regions……………….39 Table 4-3: Degree of ‘natural’ grazing by geese, rabbits, hares, deer or moose………………………………………....39 Table 4-4: Differences of vegetation structure characteristics between management classes and/or regions…………...40 Table 4-5: Total number of species in regions and management classes………………………………………………...41 Table 4-6: Results of a 3-factorial ANOVA. Impact of region, management and spatial scale on species number……..42 Table 4-7: Species numbers of the vegetation on 1, 25, 625 m² in the four regions and the management classes……....43 Table 4-8: Linear regressions between the cover of Phragmites australis and species richness of late successional 1-m²- subplots……………………………………………………………………………………………………………..43 Table 4-9: Differences in the characteristics of the species-area-curves (slope and intercept) between management classes and/or regions………………………………………………………………………………………………44 Table 4-10: Correlations of vegetation structure parameters, abiotic site conditions and mean Ellenberg values with depth of the organic layer and species number……………………………………………………………………..46 Table 4-11: Impact of Region, management, type and scale on species richness………………………………………..47 Table 4-12: Impact of region, management, type and scale on the evenness of the vegetation………………………….48 Table 4-13: Multiple linear regression models with a) elevation and vegetation structure parameters and abiotic site conditions (direct approach), b) elevation and vegetation structure parameters and mean indicator values (indirect approach)…………………………………………………………………………………………………………...50 Table 4-14: Mean (unweighted) Ellenberg indicator values and percentage of flooding and water level fluctuation indi- cators of all management classes and regions…………………………………………………………………...…52 Table 4-15: Mean of relative species number and relative cover of annual and biennial species in management classes and regions………………………………………………………………………………………………………….53 Table 4-16: Mean of relative species number and relative cover of socio-ecological species groups in management classes and regions………………………………………………………………………………………………….55 Table 4-17: Impact of management and region on mean relative cover of CSR-strategy types after Grime (1979)…….56 Table 4-18: Impact of management and region on mean cover (%) of individual species………………………………58 Table 4-19: Impact of management and region on mean frequency (%) of individual species………………………….60 V Antonia Wanner Management, biodiversity