Forest regeneration processes in oak stands with the participation of small-leaved lime under the conditions of the West Podillya

Abstract

The forest regeneration processes were investigated in the 41-100-year-old oak stands with the participation of small-leaved lime and on the 1-5-year-old harvesting areas under conditions of fresh hornbeam-oak forests of the West Podillya. The share of oak and lime in their composition varies from single trees to 10 units. The estima-tion of the natural regeneration of tree species amount was carried out by establishing in each site of 20 plots with an area of 4 m2 (2 × 2 m). Self-seeding and advance growth plants were assessed and grouped according to species, physiological condi-tion and age groups. The advance growth up to 0.50 m in height is considered to be small, 0.51-1.50 m – medium, and 1.51 m and above - large. According to the physio-logical condition, the advance growth is divided into healthy, moderately weakened and much weakened plants. It is found that natural regeneration in the stands is mostly unsatisfactory. The total number of natural regeneration of tree species in the advance growth ranges from 1.13 to 10.27 thousand plants / ha. Its species composition includes English and red oak, common ash, Norway maple and sycamore, European white elm, hornbeam, small-leaved lime, rowan tree, and beech. It was found that the age structure in the majority of the study plots is dominated by the 1-3-year-old ad-vance growth. In 59 % of the stands, its proportion is 50–100 %, while in other it var-ies within 28.6-48.4 %. Among the tree species, Norway maple and sycamore, horn-beam and elm are the best to regenerate. Their advance growth under the canopy of the parent stands reaches 4-8 years old and older. Oak advance growth of 1-3 years old was found in 72.3% of the plots (0.25-2.63 thousand plants / ha). Lime advance growth of seed origin occurs in 45.5 % of the study stands and is 0.25-1.38 thousand plants / ha with proportion 5.6-35.0 %. The frequency of advance growth occurrence in the forest stands is 30-95%. Among the tree species, the lowest rates of occurrence are characteristic of the advance growth of small-leaved lime. The amount of small advance growth in different plots varies from 50 to 100%. Among the tree species, the entire advance growth of common and red oak, common ash and beech belong to the small one which does not exceed 25 cm. In the forest stands, the moderately weakened (41.1-54.1%) young growth is prevalent and, to a large extent, the very weakened (19.1-41.8%) advance growth of tree species is present. The share of healthy advance growth in the stands varies within 14.0-30.5 %. Natural seed regen-eration of small-leaved lime is found on 38% of the investigated 1–5-year-old cutover areas. The advance growth of lime on 1-year-old cutovers occurs in 50% of the plots, on 2- and 3-year-olds - in 40%, and on 4-5-year-olds - in 30%. Its quantity ranges from 55 to 275 pcs per hectare. The average height of lime seedlings increases with age from 13.2 cm on 1-year-old cutover areas to 40.6 cm on 5-year-old cutover areas. The viability of lime nuts in different years of observation remains largely high and ranges from 55 to 94%.

Keywords

• self-seeding
• advance growth
• viability of nuts
• occurrence
• physiological state
• species composition