**3.2.1 Alluvial formation**

The Alluvial Araucaria Rainforest is associated mainly with the Montane formation and is easily distinguished by its typical physiognomy. This is a riparian forest that always occupies alluvial lands adjacent to watercourses (IBGE, 1992; Roderjan et al., 2002).

The physiognomy is structurally characterized by a high density of medium and small individuals, with the canopy ranging between 10 and 20 m in height. Communities can present different degrees of development. In the fairly homogeneous associations, subject to soils with considerable hydromorphy, such as some Fluvisols and Gleysols, *Sebastiania commersoniana* is the most relevant species. In more developed associations *Vitex megapotamica, Schinus terebinthifolius, Allophylus edulis, Luehea divaricata, Symplocos uniflora, Blepharocalyx salicifolius, Myrrhinium atropurpureum, Myrciaria tenella* and *Daphnopsis racemosa*  are present. Even *Araucaria angustifolia* can be observed where lower hydromorphy allows its growth (Leite & Klein, 1990; Roderjan et al., 2002; Barddal, 2002; Pires et al., 2005).
