CLASSIFICATION AND ORDINATION OF PLANT FORMATIONS IN THE PANTANAL OF BRAZIL

Classification and ordination of plant formations are presented for a seasonally flooded plain of the Brazilian Pantanal. Phytosociological data were collected on 10 physiognomically distinct formations during the rainy, flood, and dry seasons. The degree of association among pla nt species was measured with Jaccard similarity index, and both Jaccar d similarity index and Bray Curtis distance index were employed to cla ssify sample units into similar groups. The ordination of plant specie s and sample units were performed with Correspondence Analysis. Four g roups of plant formations were significantly distinct on a quantitativ e basis: marsh ponds/waterlogged basins, short grasslands, tall grassl and/scrub, and forest-edges. These formations were ordered along a gra dient of topographic relief from depressions with permanent standing w ater (marshes) through flats subject to seasonal flooding (grasslands and scrub) and mounds of sandy soil above the flood level (forests). A lthough hydroperiod appears to be one of the most important variables, the distribution of plant species within wetlands is most probably ex plained by the interaction of many additional factors. A few plant spe cies could be used as indicators of the local hydrological and edaphic conditions, e.g., Eleocharis elegans, Aeschynomene fluminensis, Hydro lea spinosa, and Hymenachne amplexicaulis for marsh ponds, and Caperon ia castaneifolia, Diodia kuntzei, and Eleocharis acutangula for waterl ogged basins. The procedure presented in this study could be developed as a tool for the inventory and management of the Pantanal and other palustrine wetland habitats.