Riepšas, E. and Straigytė, L. 2008. Invasiveness and Ecological Effects of Red Oak(Quercus rubra L.) in Lithuanian forests.  Baltic Forestry 14(2): 122-130

The introduction of alien tree species may cause a threat to biodiversity. Introduction should not be allowed if there are doubts concerning invasiveness of the introduced species. The plantations of red oak (Quercus rubra L.) in Lithuanian forests are established in 79 stands on an area of about 116 ha. However, its invasiveness has not been studied yet. The aim of the work is to ascertain the interaction between the red oak and native flora as well as to asses the expedience of growing red oak in Lithuanian forests. Red oak spreads more abundantly than common oak on less fertile sites. It has an adverse effect on the structure of local floral communities such as the number of grass species and their ocurrence degree decreases. Consequently, 11 nemoral grass species are not detected any more. The soil in the stands of red oak contains 34% less micromycetes, 20% less mineralizing and 5% less ammonifying microorganisms, than soil in the stands of common oak. It contains lower amounts of the most trace elements important for the nutrition of plants than the soil in the stands of common oak. The intensity of red oak invasiveness is higher than the mean (0.65), possible distribution level is medium (0.57), the level of adverse effect on society is lower than the mean (0.35). We ascertained that introduction of red oak in Lithuanian forests is not advantageous from ecological viewpoint.

Key words: Red Oak (Quercus rubra L.), forest, invasiveness