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Abstract
Introduction
English oak (Quercus robur L.) is one of the most spread and productive forest tree species. Oak forests of natural seed origin are proved to be the most resistant and productive. Natural regeneration of English oak is rather well investigated. However, such research does not lose its relevance due to the need to develop measures to promote the increase of the area of oak forests of natural seed origin.
The aim of the research was to reveal the peculiarities of forming, age and size structure of English oak natural regeneration under the forest canopy.
Materials and Methods
The research was carried out in 2010–2016 in Mokhnach forestry of the State Enterprise «Skrypaivske Training & Research Forest Economy” as well as in Chaikivske and Zhovtneve forestries of the State Enterprise “Vovchanske Forest Economy” (Kharkiv region). Natural regeneration number (density), condition and height were assessed in the 1 ? 1 meter plots at the end of vegetation period in every of 60 sample plots, which were located in different forest site conditions in the stands of 40–186 years old with relative density of stocking 0.5–0.9, and 40–100 % oak participation in the stand composition.
Over 160 thousand plants of English oak natural reproduction were assessed.
Results and Conclusions
In 2010–2016 in 60 sample plots the peculiarities of forming, age and size structure of English oak natural regeneration under a forest canopy was studied. It was found that undergrowth density was the highest in the fresh maple and lime oak stand (on average 3.4 thousand plants per ha), significantly increased with the age of the parent stand and decreased with the age of the renewal itself. In the age structure of English oak natural regeneration under a forest canopy, the current year plants predominated (46.1 %); the part of 2–3-year renewal was 29.8 %, the part of 4–8-year-old renewal was 22.7 %, the part of 9–15-year-old renewal was 1.4 %. As the relative density of parent stand stocking increased the density of oak seedlings increased, the density of current year oaks increased but the density of 4–8-year-old renewal decreased as a result of insufficient illumination or competition with other plants. In the combined sample without age distribution of English oak natural reproduction, the success of regeneration was good in 3,3 % of inspected plots, insufficient in 4.9 %, satisfactory in 8.2 %, and unsatisfactory in 83,6 % of inspected plots.
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