Kramarets V. Spruce forest stands of the Ukrainian Carpathians: current conditions and increase of biotic stability

Spruce forest stands occupy 155.6 thousand ha (24.9% of the whole forest area) on the territory of Zakarpattia OULMG, 289.3 thousand ha (49.3%) on the territory of Ivano-Frankivsk OULMG, 87.9 thousand ha (11.8%) on the territory of Lviv OULMG and 58.9 thousand ha (31.8%) on the territory of Chernivtsi OULMG. 201 thousand ha of spruce derivative forests with a volume 57.9 million m3 of growing stock can be found in the forest fund of this region. The predominant number of derivative spruce trees (59.8%) is currently situated at altitudes 600-800 m a.s.l. Based on the geobotanical study results carried out in spruce derivative forests, the plant associations (according to Brown-Blanke) have been identified showing participation of spruce trees. The species composition of adventitious plants was identified demonstrating how they can distribute themselves under the canopy of derived spruce trees and significantly transform the forest environment. The nature of reforestation successions on the site of declined or removed by cuttings of spruce derivative forests was studied with aim to investigate the natural regeneration under the canopy of derived spruce trees. The introduction of an adventitious plants such as Heracleum sosnowskyi, H. mantegazzianum, Solidago canadensis, S. gi¬gan¬tea, Stenactis annua (Erigeron annuus) and others were found as a certain danger to spruce forest stands under their canopy and between other forest gaps noting the ability of introduced plants significantly transform the forest environment. However, European spruce is still the dominant species under the canopy of spruce derivative forests. It was recommended to apply special measures should be taken for the preliminary restoration of valuable forest species (such as beech, fir) and their companions (birch, sycamore, maple) for the future formation of forest stands, which are suitable for particular edapho-climatic conditions in the area. It has been also determined the variability of the main morphological features of spruce cones on the territory of the Ukrainian Carpathians. According to the results of nuclear DNA population analyses seven coenopopulations of European spruce in the Ukrainian Carpathians, it is established that geographical distance, different ecological and phytocenotic growth conditions do not lead to their genetic differentiation and do not significantly affect the genetic characteristics of spruce in the Carpathian region. All surveyed spruce coenopopulations originate from one historical refugium and are characterized by high intrapopulation and low interpopulation variability (percentage of molecular deviations within coenopopulations - 98%, between coenopopulations - 2%). The forest areas were found significantly (R2 = 0.98) decreased with age increasing of the derivative spruce trees on the slopes of different exposures without trees decline symptoms but increased significantly (R2 = 0.96) with high level of damage. An intensive spruce sanitary conditions deterioration was observed in high relative density spruce stands (9-10 units) and in low relative density spruce stands. Degradation and decline of spruce trees were accelerated by changes in the functioning of different groups of heterotrophic organisms, their quantity, aggressiveness, and pathogenicity. It was found that the complex of soil invertebrates is restructured in spruce derivative forests with no development of mycorrhizal root fungi. It was also identified 81 species of xylotrophic macromycetes (26 species growing on living trees) and 110 species of cambio- xylophagous insects: Curculionidae (Scolytinae 25 species, Entiminae 2 species, Molytinae 5 species), Cerambycidae (28 species), Buprestidae (2 species), Siricidae (2 species). The outbreaks of bark beetle’s distribution are found as one of the most important weakening factors in spruce forests. There are measures and recommendations are proposed to improve the sanitary condition in spruce derivative forests to promote growth and formation of indigenous forest stands in Carpathian region of Ukraine.