Наукові праці Лісівничої академії наук України (Dec 2019)
The influence of phytocoenotic conditions on wood accumulation by stands with the Pseudotsuga menziesii (Mirb.) Franco participation in the western region of Ukraine
Abstract
Pseudotsuga menziesii, under appropriate cultivation conditions in rich, fresh and moist types of forest growth conditions, is a fast-growing woody species suitable for forest planting. In young stands up to 25-30 years of age, Douglas fir is inferior in growth rate to spruce and especially to larch. After 35 years of age, Douglas fir increases its growth rate and its stagnation compared to larch and spruce decreases. The best growth of Douglas fir in height, diameter and volume of the average tree was found in pure in composition stands (8-10 units), as well as in plantations where the participation of Douglas fir is 5-6 units. The initial spacing of Douglas fir in plantations is within 1.5 × 1.0 – 2.5 × 3.0 m, density – 1.3-6.6 thousand pcs ∙ ha-1 with various combinations with other species. Currently, there is a tendency to create greater plant spacing between crops of Douglas fir (2 × 2, 3.5 × 3.5 m or more) using selected planting stock. On grey (dark grey) forest soils in well-aerated locations, Douglas fir is characterized by intensive growth, high biotic stability, accumulating about 600-800 m3 ∙ ha-1 of stemwood at the age of 40-60 years. When studying the growth rate of various forms of Douglas fir by the structure of the bark, no significant difference was found between these indexes. However, in the process of selecting material for creating plantation stands, preference should still be given to individuals with a weakly and medium furrowed bark as such in which the share of bark in the total trunk volume is less. It is recommended to plant forest plantation of Douglas fir with a pure composition, which will eliminate the negative impact on the species at a young age of other fast-growing tree species, fulfil the potential for the rapid growth of Douglas fir and facilitate crop tending. The stock of Douglas fir stemwood with an initial plant spacing of 4 × 4 m at a technical maturity age is very high and even higher than in the case of a dense initial species spacing (1.5 × 1.5; 1.0 × 1.5, 2 × 2). However, if it is necessary to save planting material, a spare spacing of Douglas fir plants without the presence of associated species has several disadvantages: limited opportunities for targeted selection of highly productive individuals; late canopy closure of crops; poor self-pruning, especially at a young age; significant underutilization of potential such as forest growth conditions, which is manifested in a decrease in the intensity of intermediate use, and, therefore, the silvicultural effect of crop cultivation. In pure Douglas fir stands under conditions D2, it is recommended to take the initial density when establishing plantations in the range of 1.5-2.0 thousand units ∙ ha-1 (taking into account the associated species, the total density is 6.6 thousand units hа-1). Under forest soil conditions D3, the growth rate of Douglas fir is slightly higher, so the initial species density should be slightly less (1.0-1.5 thousand units ∙ ha-1), and taking into account the associated species – 4.5-5.0 thousand units.
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