Northern red oak (Quercus rubraL.) is one of the most important introduced tree species in the Czech Republic, occupying about 6,000 ha with ca. 900,000 m3of the standing volume. The presented study aims to evaluate its soil forming effects on natural oak sites. Soil chemistry of the upper soil layers (F+H, Ah, B horizons) was studied in three pairs of stands of both species. In each stand, four bulk samples were taken separately for particular horizons, each consisting of 5 soil-borer cores. The soil characteristics analysed were: pH (active and potential), soil adsorption complex characteristics (content of bases, exchangeable cation capacity, base saturation), exchangeable acidity (exchangeable Al and H), total carbon and nitrogen content, and plant available nutrients content (P, K, Ca, Mg). Total macronutrient content (P, K, Ca, Mg) was analysed only in holorganic horizons. Results confirmed acidification effects of red oak on the upper forest soil layers such as decreased pH, base content, base saturation, all nutrient contents in total as well as plant-available form and increased soil exchangeable acidity (exchangeable Al) in comparison to the sessile oak stands, especially in holorganic horizons and in the uppermost mineral layer (Ahhorizon). Northern red oak can be considered as a slightly site-soil degrading species in the studied sites and environmental conditions in comparison to native oak species.

The article analyses growth and quality of Northern red oak (Quercus rubra Linnaeus) based on 13 research plots (seven in red oak stands and six in sessile oak stands) with the ages between 17 to 159 years. The collected data includes height, DBH, crown diameter, stem and crown quality, health status of each tree on the plot. Analogous plots were chosen in sessile oak (Quercus sessilis Linnaeus) stands on similar sites to get reference data. The results proved the high wood production potential of red oak when compared to sessile oak being at the same or higher quality and health. The data propose the red oak to be a good additional species in lowland stands.

Influence of introduced northern red oak stands (Quercus rubra L.) on herb understory with comparison with herb understory of autochthonous Sessile oak (Quercus petraea agg. L) and Scots pine (Pinus sylvestris L.) was observed in Louny region area on 14 plots. The analysis of the ground vegetation was performed using classical phytosociological methods. Significant changes were not determined in the site character, when comparing particular tree species stands, the differences consisted especially in the natural regeneration of tree species. Northern red oak showed a tendency of more fast penetration in the neighboring stands.