Classification Structure of Floodplain Forests in Estonia: A Comparison of Two Classification Approaches

Abstract

Flooded forests in 79 sample areas were studied in various parts of Estonia. Using the principal component analysis and cluster analysis, six community types were established: (i) Tilia cordata—Mercurialis perennis, (ii) Ulmus laevis—Allium ursinum, (iii) Populus tremula—Convallaria majalis, (iv) Alnus incana—Cirsium oleraceum, (v) Alnus glutinosa—Filipendula ulmaria and, (vi) Alnus glutinosa—Carex acutiformis. The species composition of these types partly overlaps but the abundance proportions of species are clearly different and all types have several significant indicator species. Another classification scheme was established by TWlNSPAN analysis. Following the phytosociological approach, the communities belong to Querco—Fagetea, Alno—Ulmion (Pruno—Fraxinetum, Ficario—Ulmetum, Pruno padi—Alnetum incanae, the latter subdivided further into P.p.—A.i. var. Frangida alnus and P.p.—A.i. var. Urtica dioica), and to Alnetea glutinosae, Alnion (Carici elongatae—Alnetum, represented with two subassociations: C....