Red oaks were first introduced in Lithuanian forests in about 1875. This study aimed to assess morphological traits and ground vegetation of red oak stands in different sites and regions of Lithuania. The study was conducted in 32red oak forest stands located in the western, central and southern regions of Lithuania. Morphological traits of red oak and ground vegetation of the stands were recorded. The differences in morphological traits and ground vegetation of red oak between different sites and regions were assessed using redundancy analysis, canonical correspondence analysis (CCA) and indicator species analysis.

Morphological traits of red oak did not differ significantly between different sites, being similar in both fertile and unfertile sites. Similarly, morphological traits of red oak growing in the southern continental region and western coastal region of Lithuania did not differ significantly. Only two-stems and dense crown trees slightly increased further from the western region. Species number in red oak stands in the southern continental region of Lithuania was lower than that in the western coastal region. The vegetation structure of alien red oak stands differ in southern and western Lithuania.

Key words: red oak, CCA, climatic condition, site type, stem straightness.