LITTORELLETEA a Study of the Vegetation of Some Amphiphytic Communities of Western Europe
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w LITTORELLETEA A study of the vegetation of some amphiphytic communities of western Europe M.M. Schoof-van Pelt LITTORELLETEA A STUDY OF THE VEGETATION OF SOME AMPHIPHYTIC COMMUNITIES OF WESTERN EUROPE Promotor: Prof. Dr. V. Westhoff LITTORELLETEA A STUDY OF THE VEGETATION OF SOME AMPHIPHYTIC COMMUNITIES OF WESTERN EUROPE PROEFSCHRIFT TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE WISKUNDE EN NATUURWETENSCHAPPEN AAN DE KATHO LIEKE UNIVERSITEIT TE NIJMEGEN, ÒP GEZAG VAN DE RECTOR MAGNIFICUS PROF. MR. F.J.F.M. DUYNSTEE VOLGENS BESLUIT VAN HET COLLEGE VAN DECANEN IN HET OPENBAAR TE VERDEDIGEN OP DONDERDAG 21 JUNI 1973 DES NAMIDDAGS TE 2 UUR PRECIES. DOOR MARGARITA MARIA SCHOOF-VAN PELT GEBOREN TE TILBURG 1973 DRUK: STICHTING STUDENTENPERS NIJMEGEN aan Dick, die meer deed dan gedogen Ach. die Welt ist so geräumig, Und der Kopf ist so beschrankt Wilhelm Busch (1832-1908) CONTENTS I. INTRODUCTION 11 1.1 History of the investigations 11 1.2 Scope of the investigations 13 1.3 Scientific importance of the study 14 1.4 Investigated areas IS II. METHODS 21 II. 1 Vegetation analysis 21 11.2 Nomenclature 22 11.3 Water analyses 23 11.4 Soils 24 III. CLIMATE 26 IV. GEOLOGY 29 V. RESULTS: THE ASSOCIATIONS 32 V.l Isoëto-Lobelietum 32 V.l.l Introduction 32 V.l.2 The present relevés 34 V.1.3 Synecology 44 V.l .4 Synchorology 45 V.l.5 Discussion 47 V.2 Eleocharetum multicaulis 54 V.2.1 Introduction 54 V.2.2 The present relevés 57 V.2.3 Synecology 76 V.2.4 Synchorology 79 V.2.5 Discussion 80 V.2.6 Other representatives of the association 90 V.3 Pilularietum globuliferae 91 V.3.1 Introduction 91 V.3.2 The present relevés 93 V.3.3 The transects 98 V.3.4 Synecology 100 V.3.5 Synchorology 101 V.3.6 Discussion 101 V.4 Eleocharetum acicularis 106 V.4.1 Introduction 106 V.4.2 The present relevés 108 V.4.3 Synecology 111 V.4.4 Synchorology 114 V.4.5 Discussion 115 V.5 Samolo-Littorelletum 122 V.5.1 Introduction 122 V.5.2 The present relevés 123 V.5.3 Synecology 124 V.5.4 Synchorology 126 V.5.5 Discussion 126 V.6 Sparganietum minimi 128 V.6.1 Introduction 128 V.6.2 The present relevés 130 V.6.3 Synecology 132 V.6.4 Synchorology 133 V.6.5 Discussion 133 V.7 Sphagno-Sparganietum angustifolii 135 V.7.1 Introduction 135 V.7.2 The present relevés 136 V.7.3 Synecology 138 V.7.4 Synchorology 140 V.7.5 Discussion 140 V.8 The syntaxonomical position of the present associations 143 V.8.1 Introduction. Existing classifications 143 V.8.2 Discussion. Classification of the present associations and comparison with classification systems previously published 145 V.8.3 Conclusion 154 VI. DISTRIBUTION AND ECOLOGY OF LITTORELLETEA SPECIES 157 VII. IMPOVERISHMENT OF FLORA AND VEGETATION DURING THE LAST 35 YEARS 173 VILI Isoëto-Lobelietum 174 VII .2 Eleocharetum multicaulis 176 VII.3 Other associations 179 VII .4 Conclusion 180 SUMMARY 181 SAMENVATTING 183 REFERENCES 185 LEGEND TO THE TABLES 196 ACKNOWLEDGEMENTS 215 CURRICULUM VITAE 216 Chapter I INTRODUCTION 1.1 History of the investigations In 1947 the Department of Nature Conservation and Landscape Management was founded within the Dutch State Forestry Service. Its main scope was to take inventories and to carry out ecological investigations relating to choice and management of nature reserves. Within this scope, the need was felt to have at the Department's disposal a survey of the biotic communities worth while being considered for protection and conservation. The intention was: 1. to outline the major synecosystems (groups of ecosystems), such as shifting sands, dry pastures, moorland, deciduous woodland, salt marshes, swamps and former river beds; 2. to describe, within the most threatened of these synecosystems, the various plant communities characteristic of them; 3. to make an inventory of all separate sites representative of such ecosystems; 4. to arrange these representatives in a sequence according to criteria such as: optimal development, degree of disturbance, size of the stand, number of rare and characteristic taxa; 5. to determine which stands needed to be protected most urgently. Because of the limited provisions (staff and funds) of the Department, financial support was asked from the Nederlandse Organisatie voor Zuiver Wetenschappelijk Onderzoek Z.W.O. (Netherlands Organization for the Advancement of Pure Research). This Organization, however, does not intend to support any investigation carried out by an „applied" institute. The Netherlands Organization for the Advancement of Applied Research (T.N.O.) on the other hand would have considered the intended research not to be „applied", because it did not aim to increase the productive capacity of the human society. As a result the intended research came down between two stools. As a way out, the Department of Nature Conservation and Landscape 11 Management founded a subsidiary body, the „Stichting Onderzoek Levensge meenschappen" or S.O.L. (Foundation for the Investigation of Biocoenoses), which assumed the specific task of making a survey of biotic communities being considered for protection and conservation. This organization was financially supported by the Netherlands Organization for the Advancement of Pure Research. In 1956, the research task of the Department of Nature Conservation and Landscape Management of the State Forestry Service was assumed by the State Institute of Nature Conservation Research, founded in that year. In the years 1954-1956, the S.O.L. carried out an investigation and evaluation (as rendered above) of the synecosystem of the former river beds. The results of the study were published in a separate volume of Wentia (5, 1961, 258 pages). A similar investigation was considered necessary for another type of threatened ecosystem, the moorland pools. This study was undertaken by the S.O.L. and carried out by the following investigators: CA. Bastiaanssen, Drs. J. van Donselaar, Drs. P. Glas, H. Moller Pillot, J.H. Peters, H.J. Verhoeven and E.E. van der Voo. The study was published, with the understanding that mimeographed reports of all investigated stands have been issued. The importance of the investigation for Nature Conservation has been shown to full advantage. One could indicate, with the aid of the reports, the priority of which moorland pools had to be protected and adequately managed. The reports had a limited distribution, however; a summarizing publication, in which the syntaxonomy, synecology and synchorology of the observed vegetation units was described, was never published. In this respect the investigation is, therefore, not finished. It was the intention of the present author to use the data of the S.O.L. investigations as a starting-point for her own investigations of the vegetation of moorland pools. However, since she has not taken part in the former research, it was not considered appropriate to simply assemble the formerly collected data into a publication. On the other hand, it would be regrettable if use was not made of these data. Due to a limited amount of time avaible for the study, a choice had to be made concerning the number of Dutch localities presently investigated; the choice of localities and vegetation types was based on the data of the S.O.L. investigations. 12 I. 2 Scope of the investigations The present study can be best described as a comparative phytosociological investigation of the vegetation types of oligotrophic and mesotrophic moorland pools and similar waters in The Netherlands and adjacent territories. The investigated ecosystem type, the moorland pools („vennen" in Dutch) are completely or for the greater part, isolated, stagnant, fresh water pools occurring on an originally oligotrophic substrate (usually holocene blowing sand or pleistocene coversand, as well as fluvioglacial sand). These pools show vertical water movement, and therefore, have fluctuating water levels. They can run dry completely or partly during a shorter or longer period of the year. The water is of oligotrophic or dystrophic origin, but it may have a metatrophic character because of zoogenic influences (guanotrophy) or because of anthropogenic disturbances. The term metatrophic is taken from LEENTVAAR (1958), and is discussed in SEGAL (1965) and SCHROEVERS (1966). The pools are usually of aeolic origin, but in some cases they have originated by water movement (former river or brook bed, which became isolated) or by glacial influence (FABER 1948). Flora and vegetation of these moorland pools have an atlantic to subatlantic character (WESTHOFF et al. 1946, DIERSSEN 1972, Chapter VI of this study). This type of ecosystem is geographically restricted to Ireland, Great-Britain, Denmark, north western Germany, The Netherlands, Belgium and France (north of the mediterranean region). In a wider sense, the moorland pool ecosystem also occurs in shallow, oligotrophic and minero- trophic waters of East Germany, Poland and Scandinavia. The present author was mainly concerned with the type of pools which are most threatened by human disturbance. Phytosociologically the most characteristic vegetation of these moorland pools can be assigned to the class Littorelletea. Such pools are usually situated in stable gradient habitats, such as in transition zones between moorlands or forests on holocene blowing sand, pleistocene coversand or fluvioglacial sand (poor in nutrients), and areas which are richer in nutrients, such as the valley of a brooklet or a river. In some cases anthropogenic influences can be positive for the origin and maintainance of Littorelletea communities, provided that they are small, and stay quantitatively and qualitatively the same. It was also the scope of the investigation to examine if changes in the 13 Vegetation and the habitat have taken place in the decade since the S.O.L.