State and productivity of silver fir (Abies alba) stands on the northeastern macroslope of the Ukrainian Carpathians

Abstract

Introduction

In recent years, considerable attention has been devoted to the study of the biotic stability, spread of pests and diseases, and degradation processes in Abies alba stands, as well as to the characteristics of their formation, structure, and growth. A comprehensive assessment of the current condition and growth dynamics of silver fir stands is essential for evaluating the adaptive capacity of the species under climate change and for developing scientifically grounded strategies for the targeted formation of uneven-aged forest stands based on close-to-nature silviculture principles.

Materials and methods

The analysis of subcompartments was based on the current forest management database of Ukrderzhlisproekt as of 1 January 2021 and covered the northeastern macroslope of the Ukrainian Carpathians within the Ivano-Frankivsk, Lviv, and Chernivtsi regions. Sample plots were established in the Gorgany mountain range (Vygoda Forestry Management Unit, Shevchenkivske Forestry) within the most widespread forest type – moist beech-spruce mixed forest. Circular sample plots of 500 m² were established in fir stands of different ages and compositions; their number depended on the size and homogeneity of the forest subcompartment in accordance with selective forest inventory standards. The yield tables for silver fir in the study region were developed considering stand composition, site quality class, and forest type, which reflect the specific regional characteristics of fir stand development.

Results

The total area of forest stands containing silver fir on the northeastern macroslope of the Ukrainian Carpathians was estimated at approximately 130.5 thousand ha, representing 8.2% of the total forest area of the studied territory. The largest areas of fir forests are concentrated in the Lviv Region (about 45% of the total fir forest area), followed by the Ivano-Frankivsk and Chernivtsi regions, which account for approximately 30% and 25%, respectively. Exploitation forests predominate within these areas. A high degree of coenotic plasticity of silver fir was identified across 71 forest types grouped into seven typological groups within the region. The species is most widely distributed in fir forest types, where it occurs in 85% of forest stands as a dominant or co-dominant species, forming characteristic phytocoenoses. An imbalance in age structure was observed, with the area occupied by young stands being approximately three times greater than that of mature stands. The analysis showed that the increase in average diameter slows after stands reach 100 years of age. At the age of 140 years, the difference in average diameter between the studied and reference stands was approximately 4.2 cm, indicating enhanced radial growth in more intensively thinned stands. Even greater differences were observed in tree height, with an average difference of approximately 2.7 m, reflecting the potential for increased height growth under improved growing space conditions.

Conclusions

The altitudinal distribution of silver fir on the northeastern macroslope of the Ukrainian Carpathians is determined by the complex interaction of climatic, soil, and orographic factors that define its ecological niche and the boundaries of its natural range in the region. The orographic structure of the territory, particularly slope exposure, directly influences the distribution of fir–beech stands and determines their mosaic spatial structure. In the studied region, Abies alba occurs under highly favourable ecological conditions, enabling the formation of some of the highest standing wood volumes in Ukraine. Fir forests are concentrated mainly in moist beech–fir forest types, where they form highly productive stands. The predominance of site quality class I confirms the high forestry potential of these territories. The identified imbalance in age structure, with the area of young stands being three times greater than that of mature stands, may result in a future reduction in timber harvesting due to the insufficient area of stands reaching final felling age. At the same time, the predominance of young and middle-aged stands (71% of the total area) contributes to intensive carbon sequestration, which is important for climate change mitigation. The potential productivity of forest vegetation is not yet fully realized, and the revealed patterns emphasize the need to optimize forest management practices to achieve more effective utilization of the bioproductive potential of fir forests in the region.

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