The increase in forest stands productivity is closely related to the forest management based on forest typology. It is now established that the stand productivity depends on forest species relevance to the best-suited forest types. In Ukraine, techniques have been developed for determining the potential productivity of forest stands (Vorobyov 1959, Ostapenko & Tkach 2002, Turkevych et al. 1973). According to Vorobyov, the correlation between the actual and potential productivity of primary types of stands measures the extent to which a forest uses the natural fertility of the land. Since the main end product of the forest is wood, it is most logical and convenient to determine the quality of the site conditions by the stand volume.
Materials and Methods
Quantitative estimation of the forest site capacity using was carried out by means of indices of productivity of highly productive primary stands. Forest mensuration indices of modal and primary highly productive stands were analyzed using the database of the production association “Ukrderzhlisproekt” as of 01.01.2011 and according to the data of sample plots laid out in highly productive stands with a relative density of stocking of more than 0.8. The ratio of stand volume of modal stands to the stand volume of highly productive primary stands, expressed as a percentage, indicates the degree of forest site capacity using.
More than 30 tree species form forests of Ukraine, however, the Scots pine (33 % of the forest area) and pedunculate oak (24 % of the area) stands are predominate. For a detailed analysis of the site capacity using, we developed the productivity tables for modal and highly productive pine and oak stands, depending on forestry districts and forest types. It has been found that Ukrainian stands use an average of 50–75 % of the forest site capacity of lands. In general, pine stands use forest site capacity to a slightly greater extent compared to oak stands. For example, the average weighted value of the capacity used by pine forests was 68–76 % in the Polissya zone, 70–78 % and 68–73 % in the Right-bank and Left-bank Forest-Steppe zones respectively, and 54–78 % in the Steppe zone, depending on the forest type. For oak stands, the value was 71–75 % and 63–71 % for the Right-bank and Left-bank Forest-Steppe zones respectively and 65–75 % for the Steppe zone.
A systematic approach to addressing the problem of increasing forest productivity should be based on an objective assessment of the actual productivity. It is important to carry out tending felling and conversion felling of low-value young stands and secondary stands in accordance with scientifically grounded recommendations, with the differentiation of forest management systems on a zonal and typological basis. The timing of tending felling also affects the degree of the site capacity use as a result of reducing the natural mortality in stands.
First of all, forest management activities should be applied in the stands using the site capacity to a lesser extent. These are the pine stands in the fresh oak-pine infertile forest sites in the Eastern Polissya zone in Chernihiv and Sumy regions, in the fresh infertile pine forest type in the Western Polissya zone in Volyn and Rivne regions, and in the dry and fresh pine infertile sites in the Black Sea and Azov southern steppe regions in Zaporizhzhya, Mykolayiv and Kherson regions.
For the oak stands, the priority areas for forest management are as follows: the stands in the fresh maple-lime oak forest site type in Sumy and Kharkiv regions, in the fresh elm-maple oak forest type in the Right-bank Dnipro Northern Steppe zone in Dnipropetrovsk, Kirovohrad and Odesa regions, and in dry elm-maple oak forest sites in the Left-bank Dnipro Northern Steppe zone in Dnipropetrovsk and Donetsk regions.
Absolute values of the indicator, which characterizes the extent to which stands of various tree species composition use the natural fertility of the forest land, vary considerably in the natural zones of Ukraine. This is due to the specificities of forest management in these stands. The basis for increasing the productivity of forests should be the differentiation of forest management systems and individual forestry activities on a zonal and typological basis. To determine the volume and priority of relevant forest management activities, the data on the productivity of modal and highly productive pine and oak stands and the indicators of forest site capacity using would be useful.
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