Classification of lakes in Southern Sweden on the basis of their macrophyte composition by means of multivariate methods

Summary Methods developed by Jensén (1977, 1978) have been used to typify 50 lakes in Scania, S Sweden, according to their macrophyte composition. The macrophytic vegetation has been treated numerically both by classification programs (DIVINF, TABORD) and ordination programs (Reciprocal averaging, PCA). Characteristic cover (%), relevé frequency (%) and transect frequency (%) for each species in each lake have been used in the numerical treatment. The values of the attributes have been transformed to a logarithmic scale: 100 (1+log Cover %). In the classification the species have been divided into two life forms (helophytes = H, nymphaeids = N) and a life-form group (elodeids, lemnids and Isoetids = ELI). Classifications have resulted in ten helophyte lake types, eleven ELI lake types and 6 nymphaeid lake types (fusion limit of similarity ratio = 0.80) and 3 helophyte, 5 ELI and 4 nymphaeid groups of lake types (fusion limit 0.30).The three helophyte groups were characterized by Carex-Equisetum, Seirpus lacustris and Phragmites communis respectively. The ELI groups were characterized by (i) the almost complete lack of ELI, (ii) sparse elodeids, (iii) isoetids, (iv) lemnids + elodeids. The nymphaeid groups were characterized by (i) Potamogeton natans (scattered) (ii) dense co-dominance of Nuphar luteum, Nymphaea alba and Potamogeton natans, (iii) Nuphar luteum (+ Polygonum amphibium) and (iv) lack of nymphaeids.In every lake there is one of the 10 H types, one of the 6 N types and one of the 11 ELI types present the combinations generally varying from lake to lake. A given H type is often found together with a given ELI type while a given N type occurs less often with a given ELI type or a given H type (fusion limit 0.80). At fusion limit 0.30 the combinations of a certain H, ELI and N type occur more regularly. The results show that lakes must be classified on the basis of the two life-forms (H and N) and the life-form group (ELI) to indicate the true macrophyte composition of a given lake as compared with other lakes.Nomenclature follows Lid (1974); Juncus bulbosus f. fluitans is shortened to Juncus fluitans.I am grateful to Professor Nils Malmer, head of the Department of Plant Ecology, Lund, Sweden, Dr. Eddy van der Maarel, University of Nijmegen, Holland, Professor Hans Mathiesen, University of Aarhus, Denmark, and my colleague Fil. Kand. Stefan Persson for valuable advice and discussions. I also thank my wife Fil. Kand. Eva Waldemarson Jensén, Institute of Ecological Botany, Uppsala, for valuable discussions, Dr. R.S. Clymo for advice with ordination, Mr Åke Rühling for valuable technical advice, Mr. Henry Letocha for correction of the language, Mrs. Mimmi Varga for drawing the figures and Mrs. Brita Billstein for typewriting the text and the tables.This work has been suported by grants from the University of Lund, for which I am duly grateful.