A study on syntaxonomic units of communities situated in Lácar and Huiliches Department to the south-west of the province of Neuquén, Argentina is done in the district of deciduous leaf forest. 42 vegetation samples were taken according to the methodology of the phytosociological school of Zurich-Montpellier. Cover presence, flora composition, and importance value of each species was studied. A biological spectrum of the vegetation was made up and also graphs of homogeneity and species -census were prepared.
The results were: 182 species distributed in two types of vegetation: 1- Forest of the inferior deck of the mountain with Nothofagus antarctica, Austrocedrus chilensis, Schinus patagonica and Berberis buxifolia; 2- Forest of hill side with Nothofagus dombeyi, N. alpina and N. obliqua. From the phytosociological study and the use of multivaried statistical methods three new syntax appeared:
1. Austrocedro-Nothofagion antarticae all. nov., 2. Nothofagion dombeyi-obliquae all.nov. and 3. Nothofagetum dombeyi alpinae ass. nov.