The issues of conservation and restoration of forests in Ukraine currently has become a top priority. Special attention should be paid to reforestation by maximizing the use of natural seed regeneration because such forests are more resistant to negative environmental factors, diseases, and pests. In the North East of Ukraine, the largest area of forests in forest enterprises is occupied by oak stands. Oak forests perform important silvicultural and ecological functions and are a source of valuable timber in the national economy. The aims of the investigation are to analyze the current state of advance growth in the oak forests in the North-East of Ukraine, to study peculiarities of its formation and to develop research-based activities for the natural reproduction of oak forests by seeds.
Materials and Methods
The research was conducted in Trostyanetske Forestry Enterprise, in natural oak stands of different age, composition, density, and forest site capacity, which are growing in dry, fresh and moist maple-lime oak forest types. Accounting of natural regeneration was carried out according to the method developed by scientists of Ukrainian Research Institute of Forestry and Forest Melioration (URIFFM). We distributed advance growth by species, groups of heights, age groups and state of vitality.
Oak stands are dominating in the forest fund of Trostyanetske Forestry Enterprise in terms of land area and growing stock. Planted oak forest stands grow on the area of 6.5 thousand hectares, and forest stands of natural origin occupy an area of 6.8 thousand hectares. The studied oak forests have uneven age structure with near absence of young stands of natural origin. Under a canopy of uneven-aged indigenous natural oak stands in fresh maple-lime fertile oak forest type, the total number of advance growth of economically valuable species is 34.7 thousand stems per ha; the number of advance growth in oak forests in moist maple-lime fertile oak forest type is somewhat smaller (up to 30.0 thousand stems per ha). In dry maple-lime fertile oak forest type, the number of advance reproduction is up to 20.5 thousand stems per ha and the lowest number – up to 10.2 thousand units per ha – was detected under a canopy of secondary forest stands.
Orientation on natural regeneration of oak stands requires the effective use of available natural reproduction of commercially valuable species, especially of English oak (Quercus robur L.) and common ash (Fraxinus excelsior L.).
The results of the present studies concerning the quantitative characteristics of the advance growth under the canopy of uneven-aged natural oak stands indicate the usefulness of developing and implementing activities in oak forest regeneration by the natural way, in particular, by seeds.
The advance regeneration of the main forest forming species, English oak, under the canopy of natural oak stands growing in the maple-lime fertile oak forest type in the region has not been satisfactory, except for certain sites where an advance growth of economically valuable species appears periodically (after seed year) in sufficient quantity. On such sites, it is possible to form a new generation of valuable natural oak forests of seed origin, which will effectively perform important silvicultural and ecological functions, in place of mature and overmature forest stands, subject to the timely and sound forest management.
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